v3.25.2
Shareholder Report, Average Annual Return (Details)
 12 Months Ended 44 Months Ended 59 Months Ended 60 Months Ended 92 Months Ended 105 Months Ended 117 Months Ended 120 Months Ended
May 31, 2025
May 31, 2025
May 31, 2025
May 31, 2025
May 31, 2025
May 31, 2025
May 31, 2025
May 31, 2025
C000006838 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent 3.22%     9.62%       8.25%
C000006843 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B with CDSC (declining over six years from 4% to 0%)              
Average Annual Return, Percent [1] 4.72%     9.82%       8.08%
C000006844 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [2] 7.71%     10.09%       8.08%
C000006851 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent 2.07%     5.80%       5.78%
C000006856 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B with CDSC (declining over six years from 4% to 0%)              
Average Annual Return, Percent [3] 3.48%     5.96%       5.62%
C000006857 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [4] 6.46%     6.26%       5.61%
C000006887 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent 0.93%     3.80%       4.34%
C000006892 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B with CDSC (declining over six years from 4% to 0%)              
Average Annual Return, Percent [5] 2.30%     3.90%       4.18%
C000006893 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [6] 5.25%     4.25%       4.17%
C000006904 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent 10.16%     5.54%       3.13%
C000006905 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B with CDSC (declining over six years from 4% to 0%)              
Average Annual Return, Percent [7] 12.03%     5.68%       2.96%
C000006906 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [8] 15.05%     6.00%       2.96%
C000006911 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent 2.72%     8.01%       7.18%
C000006916 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B with CDSC (declining over six years from 4% to 0%)              
Average Annual Return, Percent [9] 4.21%     8.21%       7.02%
C000006917 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [10] 7.16%     8.49%       7.02%
C000006924 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent 7.42%     8.05%       6.12%
C000006929 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B with CDSC (declining over six years from 4% to 0%)              
Average Annual Return, Percent [11] 9.16%     8.23%       5.95%
C000006930 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [12] 12.13%     8.52%       5.95%
C000006937 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent 8.80%     9.15%       7.32%
C000006938 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B with CDSC (declining over six years from 4% to 0%)              
Average Annual Return, Percent [13] 10.59%     9.34%       7.15%
C000006939 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [14] 13.59%     9.62%       7.15%
C000006941 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent 7.62%     7.57%       7.54%
C000006942 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B with CDSC (declining over six years from 4% to 0%)              
Average Annual Return, Percent [15] 9.35%     7.78%       7.37%
C000006943 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [16] 12.32%     8.04%       7.37%
C000142775 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent (0.31%)     1.59%       2.63%
C000142776 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B with CDSC (declining over six years from 4% to 0%)              
Average Annual Return, Percent [17] 0.98%     1.64%       2.39%
C000142777 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [18] 4.02%     2.03%       2.39%
C000160020 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent 8.99%     14.77%     14.06% [19]  
C000160021 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B with CDSC (declining over six years from 4% to 0%)              
Average Annual Return, Percent [20] 10.76%     15.05%     13.91% [21]  
C000160022 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [22] 13.73%     15.28%     13.91% [23]  
C000160029 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent (11.05%)     7.28%     6.28% [24]  
C000160030 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B with CDSC (declining over six years from 4% to 0%)              
Average Annual Return, Percent [25] (9.87%)     7.43%     6.12% [26]  
C000160031 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [27] (7.28%)     7.72%     6.12% [28]  
C000160038 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent 0.12%     12.76%     9.18% [29]  
C000160039 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B with CDSC (declining over six years from 4% to 0%)              
Average Annual Return, Percent [30] 1.66%     13.02%     9.03% [31]  
C000160040 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [32] 4.56%     13.26%     9.03% [33]  
C000172715 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent 1.55%     12.84%   9.90% [34]    
C000172716 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B with CDSC (declining over six years from 4% to 0%)              
Average Annual Return, Percent [35] 2.97%     13.08%   9.81% [36]    
C000172717 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [37] 5.85%     13.32%   9.81% [38]    
C000220109 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A with initial sales charge (5.75%)              
Average Annual Return, Percent 12.16%   12.07% [39]          
C000220112 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C with CDSC (1% for 12 months)              
Average Annual Return, Percent [40] 17.21%   12.58% [41]          
Without Sales Load [Member] | C000006838 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent 9.52%     10.92%       8.89%
Without Sales Load [Member] | C000006843 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B without sales charge              
Average Annual Return, Percent 8.72%     10.10%       8.08%
Without Sales Load [Member] | C000006844 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent 8.71%     10.09%       8.08%
Without Sales Load [Member] | C000006845 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent 9.80%     11.20%       9.16%
Without Sales Load [Member] | C000006847 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent 8.72%     10.09%       8.08%
Without Sales Load [Member] | C000006849 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent 9.28%     10.64%       8.62%
Without Sales Load [Member] | C000006850 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent 9.55%     10.92%       8.89%
Without Sales Load [Member] | C000006839 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent 9.84%     11.20%       9.16%
Without Sales Load [Member] | C000231058 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent 9.89% 5.22% [42]            
Without Sales Load [Member] | C000006851 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent 8.30%     7.06%       6.41%
Without Sales Load [Member] | C000006856 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B without sales charge              
Average Annual Return, Percent 7.48%     6.27%       5.62%
Without Sales Load [Member] | C000006857 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent 7.46%     6.26%       5.61%
Without Sales Load [Member] | C000006858 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent 8.57%     7.34%       6.68%
Without Sales Load [Member] | C000006860 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent 7.50%     6.28%       5.62%
Without Sales Load [Member] | C000006862 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent 8.06%     6.81%       6.14%
Without Sales Load [Member] | C000006863 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent 8.27%     7.07%       6.41%
Without Sales Load [Member] | C000006852 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent 8.58%     7.34%       6.67%
Without Sales Load [Member] | C000231059 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent 8.64% 3.30% [43]            
Without Sales Load [Member] | C000006887 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent 7.09%     5.03%       4.96%
Without Sales Load [Member] | C000006892 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B without sales charge              
Average Annual Return, Percent 6.30%     4.25%       4.18%
Without Sales Load [Member] | C000006893 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent 6.25%     4.25%       4.17%
Without Sales Load [Member] | C000006894 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent 7.33%     5.30%       5.22%
Without Sales Load [Member] | C000006896 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent 6.26%     4.25%       4.18%
Without Sales Load [Member] | C000006898 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent 6.83%     4.78%       4.70%
Without Sales Load [Member] | C000006899 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent 7.10%     5.03%       4.96%
Without Sales Load [Member] | C000006888 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent 7.35%     5.30%       5.22%
Without Sales Load [Member] | C000231060 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent 7.40% 2.36% [44]            
Without Sales Load [Member] | C000006904 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent 16.88%     6.79%       3.74%
Without Sales Load [Member] | C000006905 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B without sales charge              
Average Annual Return, Percent 16.03%     6.00%       2.96%
Without Sales Load [Member] | C000006906 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent 16.05%     6.00%       2.96%
Without Sales Load [Member] | C000006907 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent 17.20%     7.06%       4.00%
Without Sales Load [Member] | C000071424 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent 16.01%     6.00%       2.96%
Without Sales Load [Member] | C000071425 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent 16.62%     6.53%       3.48%
Without Sales Load [Member] | C000071426 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent 16.90%     6.80%       3.74%
Without Sales Load [Member] | C000071427 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent 17.19%     7.06%       3.99%
Without Sales Load [Member] | C000071428 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent 17.35%     7.22%       4.13%
Without Sales Load [Member] | C000006911 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent 8.98%     9.30%       7.82%
Without Sales Load [Member] | C000006916 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B without sales charge              
Average Annual Return, Percent 8.21%     8.50%       7.02%
Without Sales Load [Member] | C000006917 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent 8.16%     8.49%       7.02%
Without Sales Load [Member] | C000006918 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent 9.29%     9.58%       8.09%
Without Sales Load [Member] | C000006920 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent 8.16%     8.48%       7.01%
Without Sales Load [Member] | C000006922 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent 8.69%     9.03%       7.55%
Without Sales Load [Member] | C000006923 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent 8.98%     9.31%       7.82%
Without Sales Load [Member] | C000006912 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent 9.25%     9.58%       8.09%
Without Sales Load [Member] | C000231061 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent 9.33% 4.47% [45]            
Without Sales Load [Member] | C000006924 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent 13.98%     9.34%       6.75%
Without Sales Load [Member] | C000006929 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B without sales charge              
Average Annual Return, Percent 13.16%     8.52%       5.95%
Without Sales Load [Member] | C000006930 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent 13.13%     8.52%       5.95%
Without Sales Load [Member] | C000006931 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent 14.27%     9.61%       7.02%
Without Sales Load [Member] | C000006933 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent 13.19%     8.52%       5.95%
Without Sales Load [Member] | C000006935 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent 13.72%     9.06%       6.48%
Without Sales Load [Member] | C000006936 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent 14.00%     9.33%       6.75%
Without Sales Load [Member] | C000006925 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent 14.27%     9.61%       7.01%
Without Sales Load [Member] | C000195683 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent 14.38%     9.71% 7.22% [46]      
Without Sales Load [Member] | C000006937 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent 15.44%     10.45%       7.95%
Without Sales Load [Member] | C000006938 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B without sales charge              
Average Annual Return, Percent 14.59%     9.62%       7.15%
Without Sales Load [Member] | C000006939 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent 14.59%     9.62%       7.15%
Without Sales Load [Member] | C000006940 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent 15.74%     10.72%       8.23%
Without Sales Load [Member] | C000071431 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent 14.60%     9.63%       7.15%
Without Sales Load [Member] | C000071432 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent 15.14%     10.17%       7.68%
Without Sales Load [Member] | C000071433 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent 15.45%     10.45%       7.95%
Without Sales Load [Member] | C000071430 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent 15.73%     10.72%       8.22%
Without Sales Load [Member] | C000034484 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent 15.88%     10.86%       8.35%
Without Sales Load [Member] | C000006941 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent 14.19%     8.86%       8.18%
Without Sales Load [Member] | C000006942 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B without sales charge              
Average Annual Return, Percent 13.35%     8.05%       7.37%
Without Sales Load [Member] | C000006943 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent 13.32%     8.04%       7.37%
Without Sales Load [Member] | C000006944 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent 14.47%     9.13%       8.45%
Without Sales Load [Member] | C000071434 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent 13.35%     8.04%       7.37%
Without Sales Load [Member] | C000071435 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent 13.92%     8.59%       7.91%
Without Sales Load [Member] | C000071436 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent 14.18%     8.86%       8.18%
Without Sales Load [Member] | C000071437 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent 14.47%     9.13%       8.45%
Without Sales Load [Member] | C000034485 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent 14.60%     9.25%       8.56%
Without Sales Load [Member] | C000142775 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent 5.77%     2.81%       3.24%
Without Sales Load [Member] | C000142776 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B without sales charge              
Average Annual Return, Percent 4.98%     2.02%       2.39%
Without Sales Load [Member] | C000142777 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent 5.02%     2.03%       2.39%
Without Sales Load [Member] | C000142778 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent 6.09%     3.05%       3.42%
Without Sales Load [Member] | C000142779 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent 5.03%     2.03%       2.39%
Without Sales Load [Member] | C000142780 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent 5.56%     2.55%       2.91%
Without Sales Load [Member] | C000142781 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent 5.83%     2.81%       3.16%
Without Sales Load [Member] | C000142782 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent 6.06%     3.04%       3.42%
Without Sales Load [Member] | C000195688 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent 6.20%     3.14% 3.99% [47]      
Without Sales Load [Member] | C000160020 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent 15.64%     16.14%     14.76% [19]  
Without Sales Load [Member] | C000160021 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B without sales charge              
Average Annual Return, Percent 14.76%     15.28%     13.91% [21]  
Without Sales Load [Member] | C000160022 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent 14.73%     15.28%     13.91% [23]  
Without Sales Load [Member] | C000160023 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent 15.90%     16.44%     15.05% [48]  
Without Sales Load [Member] | C000160024 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent 14.76%     15.29%     13.91% [49]  
Without Sales Load [Member] | C000160025 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent 15.32%     15.85%     14.48% [50]  
Without Sales Load [Member] | C000160026 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent 15.58%     16.14%     14.76% [51]  
Without Sales Load [Member] | C000160027 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent 15.92%     16.45%     15.06% [52]  
Without Sales Load [Member] | C000160028 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent 15.97%     16.53%     15.14% [53]  
Without Sales Load [Member] | C000160029 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent (5.62%)     8.55%     6.93% [24]  
Without Sales Load [Member] | C000160030 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B without sales charge              
Average Annual Return, Percent (6.34%)     7.73%     6.12% [26]  
Without Sales Load [Member] | C000160031 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent (6.40%)     7.72%     6.12% [28]  
Without Sales Load [Member] | C000160032 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent (5.41%)     8.81%     7.19% [54]  
Without Sales Load [Member] | C000160033 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent (6.39%)     7.74%     6.12% [55]  
Without Sales Load [Member] | C000160034 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent (5.84%)     8.28%     6.65% [56]  
Without Sales Load [Member] | C000160035 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent (5.66%)     8.55%     6.92% [57]  
Without Sales Load [Member] | C000160036 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent (5.41%)     8.83%     7.18% [58]  
Without Sales Load [Member] | C000160037 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent (5.30%)     8.94%     7.28% [59]  
Without Sales Load [Member] | C000160038 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent 6.23%     14.10%     9.84% [29]  
Without Sales Load [Member] | C000160039 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B without sales charge              
Average Annual Return, Percent 5.51%     13.26%     9.03% [31]  
Without Sales Load [Member] | C000160040 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent 5.52%     13.26%     9.03% [33]  
Without Sales Load [Member] | C000160041 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent 6.48%     14.38%     10.12% [60]  
Without Sales Load [Member] | C000160042 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent 6.21%     13.92%     9.36% [61]  
Without Sales Load [Member] | C000160043 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent 5.99%     13.82%     9.57% [62]  
Without Sales Load [Member] | C000160044 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent 6.24%     14.11%     9.85% [63]  
Without Sales Load [Member] | C000160045 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent 6.54%     14.40%     10.13% [64]  
Without Sales Load [Member] | C000160046 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent 6.60%     14.47%     10.21% [65]  
Without Sales Load [Member] | C000172715 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent 7.74%     14.18%   10.65% [34]    
Without Sales Load [Member] | C000172716 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name B without sales charge              
Average Annual Return, Percent 6.87%     13.33%   9.81% [36]    
Without Sales Load [Member] | C000172717 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent 6.82%     13.32%   9.81% [38]    
Without Sales Load [Member] | C000172718 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent 7.93%     14.47%   10.92% [66]    
Without Sales Load [Member] | C000172719 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent 7.44%     13.43%   9.88% [67]    
Without Sales Load [Member] | C000172720 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent 7.46%     13.91%   10.37% [68]    
Without Sales Load [Member] | C000172721 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent 7.70%     14.19%   10.65% [69]    
Without Sales Load [Member] | C000172722 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent 7.97%     14.48%   10.92% [70]    
Without Sales Load [Member] | C000172723 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent 8.06%     14.58%   11.01% [71]    
Without Sales Load [Member] | C000220109 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name A without sales charge              
Average Annual Return, Percent 19.00%   13.43% [39]          
Without Sales Load [Member] | C000220112 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name C without sales charge              
Average Annual Return, Percent 18.21%   12.58% [41]          
Without Sales Load [Member] | C000220111 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name I without sales charge              
Average Annual Return, Percent 19.33%   13.74% [72]          
Without Sales Load [Member] | C000220110 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R1 without sales charge              
Average Annual Return, Percent 18.14%   12.56% [73]          
Without Sales Load [Member] | C000220113 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R2 without sales charge              
Average Annual Return, Percent 18.81%   13.12% [74]          
Without Sales Load [Member] | C000220108 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R3 without sales charge              
Average Annual Return, Percent 19.04%   13.44% [75]          
Without Sales Load [Member] | C000220107 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R4 without sales charge              
Average Annual Return, Percent 19.34%   13.75% [76]          
Without Sales Load [Member] | C000220106 [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name R6 without sales charge              
Average Annual Return, Percent 19.42%   13.77% [77]          
Standard And Poor s 500 Stock Index [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name Standard & Poor's 500 Stock Index              
Average Annual Return, Percent 13.52% [78] 10.31% [42],[79]   15.94% [78] 13.66% [47],[80]     12.86% [78]
Bloomberg U S Aggregate Bond Index [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name Bloomberg U.S. Aggregate Bond Index              
Average Annual Return, Percent 5.46% [81] (1.32%) [44],[82]   (0.90%) [81]       1.49% [81]
Russell 3000 Index [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name Russell 3000® Index              
Average Annual Return, Percent 13.12% [83]     15.34% [83]   13.35% [34],[83] 13.41% [24],[84]  
MSCI Emerging Markets Index net div [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name MSCI Emerging Markets Index (net div)              
Average Annual Return, Percent [85] 13.04%     7.07%       3.93%
MSCI All Country World ex US Index net div [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name MSCI All Country World (ex-US) Index (net div)              
Average Annual Return, Percent 13.75% [86]     10.37% [86] 5.67% [46],[87]     5.47% [86]
MSCI EAFE Europe Australasia Far East Index net div [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name MSCI EAFE (Europe, Australasia, Far East) Index (net div)              
Average Annual Return, Percent 13.33% [88]   10.92% [39],[89] 11.42% [88]       5.97% [88]
MFS Conservative Allocation Fund Blended Index [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name MFS Conservative Allocation Fund Blended Index              
Average Annual Return, Percent 8.50% [81] 2.79% [44],[82]   5.19% [81]       5.25% [81]
MFS Growth Allocation Fund Blended Index [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name MFS Growth Allocation Fund Blended Index              
Average Annual Return, Percent 11.48% [90] 6.68% [45],[91]   11.21% [90]       8.53% [90]
MFS Moderate Allocation Fund Blended Index [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name MFS Moderate Allocation Fund Blended Index              
Average Annual Return, Percent 10.00% [92] 4.78% [43],[93]   8.23% [92]       6.97% [92]
Russell Midcap Index [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name Russell Midcap® Index              
Average Annual Return, Percent [83] 10.32%     12.69%   10.19% [34]    
Russell 2000 Index [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name Russell 2000® Index              
Average Annual Return, Percent [84] 1.19%     9.64%     7.65% [24]  
Russell 1000 Value Index [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name Russell 1000® Value Index              
Average Annual Return, Percent [94] 8.91%     13.02%     9.94% [29]  
Russell 1000 Growth Index [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name Russell 1000® Growth Index              
Average Annual Return, Percent [95] 17.62%     17.69%     17.14% [19]  
MSCI All Country World ex US Growth Index net div [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name MSCI All Country World (ex-US) Growth Index (net div)              
Average Annual Return, Percent [86] 10.81%     7.33%       5.66%
ICE BofA 0 3 Month U S Treasury Bill Index [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name ICE BofA 0-3 Month U.S. Treasury Bill Index              
Average Annual Return, Percent 4.81% [96]     2.74% [96] 2.41% [47],[80]     1.93% [96]
MSCI EAFE Europe Australasia Far East Value Index net div [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name MSCI EAFE (Europe, Australasia, Far East) Value Index (net div)              
Average Annual Return, Percent [89] 18.72%   14.19% [39]          
MFS Aggressive Growth Allocation Fund Blended Index [Member]                
Average Annual Return [Line Items]                
Line Graph and Table Measure Name MFS Aggressive Growth Allocation Fund Blended Index              
Average Annual Return, Percent 12.97% [78] 8.44% [42],[79]   14.06% [78]       9.83% [78]
[1] Assuming redemption at the end of the applicable period.
[2] Assuming redemption at the end of the applicable period.
[3] Assuming redemption at the end of the applicable period.
[4] Assuming redemption at the end of the applicable period.
[5] Assuming redemption at the end of the applicable period.
[6] Assuming redemption at the end of the applicable period.
[7] Assuming redemption at the end of the applicable period.
[8] Assuming redemption at the end of the applicable period.
[9] Assuming redemption at the end of the applicable period.
[10] Assuming redemption at the end of the applicable period.
[11] Assuming redemption at the end of the applicable period.
[12] Assuming redemption at the end of the applicable period.
[13] Assuming redemption at the end of the applicable period.
[14] Assuming redemption at the end of the applicable period.
[15] Assuming redemption at the end of the applicable period.
[16] Assuming redemption at the end of the applicable period.
[17] Assuming redemption at the end of the applicable period.
[18] Assuming redemption at the end of the applicable period.
[19] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[20] Assuming redemption at the end of the applicable period.
[21] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[22] Assuming redemption at the end of the applicable period.
[23] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[24] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[25] Assuming redemption at the end of the applicable period.
[26] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[27] Assuming redemption at the end of the applicable period.
[28] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[29] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[30] Assuming redemption at the end of the applicable period.
[31] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[32] Assuming redemption at the end of the applicable period.
[33] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[34] For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2025.
[35] Assuming redemption at the end of the applicable period.
[36] For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2025.
[37] Assuming redemption at the end of the applicable period.
[38] For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2025.
[39] For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2025.
[40] Assuming redemption at the end of the applicable period.
[41] For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2025.
[42] For the period from the commencement of the class's investment operations, September 30, 2021 through May 31, 2025.
[43] For the period from the commencement of the class's investment operations, September 30, 2021 through May 31, 2025.
[44] For the period from the commencement of the class's investment operations, September 30, 2021 through May 31, 2025.
[45] For the period from the commencement of the class's investment operations, September 30, 2021 through May 31, 2025.
[46] For the period from the commencement of the class's investment operations, October 2, 2017 through May 31, 2025.
[47] For the period from the commencement of the class's investment operations, October 2, 2017 through May 31, 2025.
[48] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[49] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[50] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[51] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[52] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[53] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[54] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[55] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[56] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[57] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[58] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[59] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[60] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[61] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[62] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[63] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[64] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[65] For the period from the commencement of the class's investment operations, September 15, 2015 through May 31, 2025.
[66] For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2025.
[67] For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2025.
[68] For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2025.
[69] For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2025.
[70] For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2025.
[71] For the period from the commencement of the class's investment operations, August 19, 2016 through May 31, 2025.
[72] For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2025.
[73] For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2025.
[74] For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2025.
[75] For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2025.
[76] For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2025.
[77] For the period from the commencement of the class's investment operations, June 30, 2020 through May 31, 2025.
[78] Source: FactSet Research Systems Inc.
[79] Source: FactSet Research Systems Inc.
[80] Source: FactSet Research Systems Inc.
[81] Source: FactSet Research Systems Inc.
[82] Source: FactSet Research Systems Inc.
[83] Source: FactSet Research Systems Inc.
[84] Source: FactSet Research Systems Inc.
[85] Source: FactSet Research Systems Inc.
[86] Source: FactSet Research Systems Inc.
[87] Source: FactSet Research Systems Inc.
[88] Source: FactSet Research Systems Inc.
[89] Source: FactSet Research Systems Inc.
[90] Source: FactSet Research Systems Inc.
[91] Source: FactSet Research Systems Inc.
[92] Source: FactSet Research Systems Inc.
[93] Source: FactSet Research Systems Inc.
[94] Source: FactSet Research Systems Inc.
[95] Source: FactSet Research Systems Inc.
[96] Source: FactSet Research Systems Inc.