v3.26.1
Shareholder Report, Average Annual Return (Details)
 12 Months Ended 46 Months Ended 56 Months Ended 60 Months Ended 113 Months Ended 116 Months Ended 120 Months Ended
Apr. 30, 2026
Apr. 30, 2026
Apr. 30, 2026
Apr. 30, 2026
Apr. 30, 2026
Apr. 30, 2026
Apr. 30, 2026
C000229441 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A with initial sales charge (5.75%)            
Average Annual Return, Percent 17.24%   6.15% [1]        
C000229440 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C with CDSC (1% for 12 months)            
Average Annual Return, Percent [2] 22.56%   6.73% [3]        
C000236389 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A with initial sales charge (4.25%)            
Average Annual Return, Percent (0.45%) 2.04% [4]          
C000236392 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C with CDSC (1% for 12 months)            
Average Annual Return, Percent [5] 2.30% 2.45% [6]          
C000173915 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A with initial sales charge (5.75%)            
Average Annual Return, Percent 17.28%     7.08% 10.24% [7]    
C000173916 [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 [8] 20.39%     7.58% 10.29% [9]    
C000173917 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C with CDSC (1% for 12 months)            
Average Annual Return, Percent [10] 22.48%     7.55% 10.12% [11]    
C000119447 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A with initial sales charge (5.75%)            
Average Annual Return, Percent 17.29%     7.15%     10.13%
C000119448 [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 [12] 19.59%     7.32%     9.97%
C000119449 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C with CDSC (1% for 12 months)            
Average Annual Return, Percent [13] 22.50%     7.60%     9.96%
C000119423 [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 [14] 5.25%     2.58%     5.32%
C000119430 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A with initial sales charge (5.75%)            
Average Annual Return, Percent 3.67%     2.46%     5.49%
C000119424 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C with CDSC (1% for 12 months)            
Average Annual Return, Percent [15] 8.24%     2.90%     5.32%
C000092196 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A with initial sales charge (5.75%)            
Average Annual Return, Percent 17.24%     7.13%     10.14%
C000092197 [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 [16] 19.44%     7.29%     9.96%
C000092198 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C with CDSC (1% for 12 months)            
Average Annual Return, Percent [17] 22.44%     7.59%     9.96%
C000119439 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A with initial sales charge (5.75%)            
Average Annual Return, Percent 15.96%     6.82%     9.97%
C000119440 [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 [18] 18.12%     6.99%     9.80%
C000119441 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C with CDSC (1% for 12 months)            
Average Annual Return, Percent [19] 21.07%     7.28%     9.79%
C000119431 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A with initial sales charge (5.75%)            
Average Annual Return, Percent 10.29%     5.13%     8.66%
C000119432 [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] 12.19%     5.26%     8.49%
C000119433 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C with CDSC (1% for 12 months)            
Average Annual Return, Percent [21] 15.11%     5.58%     8.48%
C000006829 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A with initial sales charge (5.75%)            
Average Annual Return, Percent 14.42%     6.39%     9.60%
C000006830 [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 [22] 16.56%     6.55%     9.43%
C000006831 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C with CDSC (1% for 12 months)            
Average Annual Return, Percent [23] 19.56%     6.85%     9.43%
C000006820 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A with initial sales charge (5.75%)            
Average Annual Return, Percent 6.12%     3.52%     7.09%
C000006821 [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 [24] 7.75%     3.65%     6.92%
C000006822 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C with CDSC (1% for 12 months)            
Average Annual Return, Percent [25] 10.79%     3.96%     6.92%
C000006793 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A with initial sales charge (4.25%)            
Average Annual Return, Percent 5.26%     2.56%     4.50%
C000006794 [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 [26] 5.12%     2.35%     4.17%
C000006795 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C with CDSC (1% for 12 months)            
Average Annual Return, Percent [27] 8.12%     2.68%     4.16%
Without Sales Load [Member] | C000229439 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R4 without sales charge            
Average Annual Return, Percent 24.74%   7.77% [28]        
Without Sales Load [Member] | C000229442 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R6 without sales charge            
Average Annual Return, Percent 24.86%   7.88% [29]        
Without Sales Load [Member] | C000229441 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A without sales charge            
Average Annual Return, Percent 24.39%   7.51% [1]        
Without Sales Load [Member] | C000229440 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C without sales charge            
Average Annual Return, Percent 23.56%   6.73% [3]        
Without Sales Load [Member] | C000229443 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name I without sales charge            
Average Annual Return, Percent 24.75%   7.79% [30]        
Without Sales Load [Member] | C000229438 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R1 without sales charge            
Average Annual Return, Percent 23.57%   6.73% [31]        
Without Sales Load [Member] | C000229437 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R2 without sales charge            
Average Annual Return, Percent 24.16%   7.26% [32]        
Without Sales Load [Member] | C000229436 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R3 without sales charge            
Average Annual Return, Percent 24.44%   7.52% [33]        
Without Sales Load [Member] | C000236387 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R6 without sales charge            
Average Annual Return, Percent 4.25% 3.50% [34]          
Without Sales Load [Member] | C000236390 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R1 without sales charge            
Average Annual Return, Percent 3.30% 2.45% [35]          
Without Sales Load [Member] | C000236393 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R2 without sales charge            
Average Annual Return, Percent 3.81% 2.96% [36]          
Without Sales Load [Member] | C000236388 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R3 without sales charge            
Average Annual Return, Percent 4.07% 3.21% [37]          
Without Sales Load [Member] | C000236386 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R4 without sales charge            
Average Annual Return, Percent 4.22% 3.47% [38]          
Without Sales Load [Member] | C000236389 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A without sales charge            
Average Annual Return, Percent 3.97% 3.19% [4]          
Without Sales Load [Member] | C000236392 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C without sales charge            
Average Annual Return, Percent 3.29% 2.45% [6]          
Without Sales Load [Member] | C000236391 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name I without sales charge            
Average Annual Return, Percent 4.22% 3.47% [39]          
Without Sales Load [Member] | C000173915 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A without sales charge            
Average Annual Return, Percent 24.43%     8.35% 10.94% [7]    
Without Sales Load [Member] | C000173916 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name B without sales charge            
Average Annual Return, Percent 24.39%     7.87% 10.29% [9]    
Without Sales Load [Member] | C000173917 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C without sales charge            
Average Annual Return, Percent 23.48%     7.55% 10.12% [11]    
Without Sales Load [Member] | C000173918 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name I without sales charge            
Average Annual Return, Percent 24.67%     8.63% 11.22% [40]    
Without Sales Load [Member] | C000119453 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R3 without sales charge            
Average Annual Return, Percent 24.44%     8.42%     10.79%
Without Sales Load [Member] | C000119454 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R4 without sales charge            
Average Annual Return, Percent 24.73%     8.69%     11.06%
Without Sales Load [Member] | C000173233 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R6 without sales charge            
Average Annual Return, Percent 24.94%     8.84%   11.02% [41]  
Without Sales Load [Member] | C000173923 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R6 without sales charge            
Average Annual Return, Percent 24.83%     8.78% 11.35% [42]    
Without Sales Load [Member] | C000173922 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R4 without sales charge            
Average Annual Return, Percent 24.71%     8.61% 11.21% [43]    
Without Sales Load [Member] | C000173919 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R1 without sales charge            
Average Annual Return, Percent 24.44%     8.14% 10.44% [44]    
Without Sales Load [Member] | C000173920 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R2 without sales charge            
Average Annual Return, Percent 24.05%     8.07% 10.66% [45]    
Without Sales Load [Member] | C000173921 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R3 without sales charge            
Average Annual Return, Percent 24.38%     8.36% 10.94% [46]    
Without Sales Load [Member] | C000173232 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R6 without sales charge            
Average Annual Return, Percent 23.47%     8.53%   10.84% [47]  
Without Sales Load [Member] | C000119446 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R4 without sales charge            
Average Annual Return, Percent 23.32%     8.37%     10.90%
Without Sales Load [Member] | C000119442 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name I without sales charge            
Average Annual Return, Percent 23.31%     8.37%     10.91%
Without Sales Load [Member] | C000119443 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R1 without sales charge            
Average Annual Return, Percent 22.22%     7.31%     9.80%
Without Sales Load [Member] | C000119444 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R2 without sales charge            
Average Annual Return, Percent 22.69%     7.82%     10.34%
Without Sales Load [Member] | C000119445 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R3 without sales charge            
Average Annual Return, Percent 22.97%     8.09%     10.62%
Without Sales Load [Member] | C000119447 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A without sales charge            
Average Annual Return, Percent 24.44%     8.42%     10.78%
Without Sales Load [Member] | C000119448 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name B without sales charge            
Average Annual Return, Percent 23.59%     7.62%     9.97%
Without Sales Load [Member] | C000119449 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C without sales charge            
Average Annual Return, Percent 23.50%     7.60%     9.96%
Without Sales Load [Member] | C000119450 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name I without sales charge            
Average Annual Return, Percent 24.75%     8.68%     11.01%
Without Sales Load [Member] | C000119451 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R1 without sales charge            
Average Annual Return, Percent 23.66%     7.63%     9.97%
Without Sales Load [Member] | C000119452 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R2 without sales charge            
Average Annual Return, Percent 24.13%     8.15%     10.52%
Without Sales Load [Member] | C000173229 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R6 without sales charge            
Average Annual Return, Percent 24.83%     8.84%   11.01% [48]  
Without Sales Load [Member] | C000119423 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name B without sales charge            
Average Annual Return, Percent 9.25%     2.90%     5.32%
Without Sales Load [Member] | C000119430 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A without sales charge            
Average Annual Return, Percent 10.00%     3.68%     6.12%
Without Sales Load [Member] | C000119424 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C without sales charge            
Average Annual Return, Percent 9.24%     2.90%     5.32%
Without Sales Load [Member] | C000119425 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name I without sales charge            
Average Annual Return, Percent 10.33%     3.92%     6.37%
Without Sales Load [Member] | C000119426 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R1 without sales charge            
Average Annual Return, Percent 7.86%     2.65%     5.18%
Without Sales Load [Member] | C000119427 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R2 without sales charge            
Average Annual Return, Percent 9.79%     3.42%     5.84%
Without Sales Load [Member] | C000119428 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R3 without sales charge            
Average Annual Return, Percent 10.06%     3.67%     6.11%
Without Sales Load [Member] | C000119429 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R4 without sales charge            
Average Annual Return, Percent 10.25%     3.92%     6.37%
Without Sales Load [Member] | C000173230 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R6 without sales charge            
Average Annual Return, Percent 10.45%     4.07%   6.28% [49]  
Without Sales Load [Member] | C000092196 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A without sales charge            
Average Annual Return, Percent 24.39%     8.41%     10.79%
Without Sales Load [Member] | C000092197 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name B without sales charge            
Average Annual Return, Percent 23.44%     7.59%     9.96%
Without Sales Load [Member] | C000092198 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C without sales charge            
Average Annual Return, Percent 23.44%     7.59%     9.96%
Without Sales Load [Member] | C000092199 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name I without sales charge            
Average Annual Return, Percent 24.65%     8.68%     11.06%
Without Sales Load [Member] | C000092200 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R1 without sales charge            
Average Annual Return, Percent 23.46%     7.60%     9.96%
Without Sales Load [Member] | C000092201 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R2 without sales charge            
Average Annual Return, Percent 24.05%     8.13%     10.51%
Without Sales Load [Member] | C000092202 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R3 without sales charge            
Average Annual Return, Percent 24.34%     8.40%     10.79%
Without Sales Load [Member] | C000092203 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R4 without sales charge            
Average Annual Return, Percent 24.68%     8.66%     11.06%
Without Sales Load [Member] | C000119437 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R3 without sales charge            
Average Annual Return, Percent 17.01%     6.38%     9.29%
Without Sales Load [Member] | C000119438 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R4 without sales charge            
Average Annual Return, Percent 17.30%     6.65%     9.58%
Without Sales Load [Member] | C000173231 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R6 without sales charge            
Average Annual Return, Percent 17.45%     6.80%   9.49% [50]  
Without Sales Load [Member] | C000119439 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A without sales charge            
Average Annual Return, Percent 23.03%     8.09%     10.63%
Without Sales Load [Member] | C000119440 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name B without sales charge            
Average Annual Return, Percent 22.12%     7.29%     9.80%
Without Sales Load [Member] | C000119441 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C without sales charge            
Average Annual Return, Percent 22.07%     7.28%     9.79%
Without Sales Load [Member] | C000119431 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A without sales charge            
Average Annual Return, Percent 17.02%     6.38%     9.30%
Without Sales Load [Member] | C000119432 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name B without sales charge            
Average Annual Return, Percent 16.19%     5.59%     8.49%
Without Sales Load [Member] | C000119433 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C without sales charge            
Average Annual Return, Percent 16.11%     5.58%     8.48%
Without Sales Load [Member] | C000119434 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name I without sales charge            
Average Annual Return, Percent 17.35%     6.65%     9.55%
Without Sales Load [Member] | C000119435 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R1 without sales charge            
Average Annual Return, Percent 16.03%     5.56%     8.45%
Without Sales Load [Member] | C000119436 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R2 without sales charge            
Average Annual Return, Percent 16.72%     6.12%     9.02%
Without Sales Load [Member] | C000006829 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A without sales charge            
Average Annual Return, Percent 21.40%     7.66%     10.25%
Without Sales Load [Member] | C000006830 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name B without sales charge            
Average Annual Return, Percent 20.56%     6.86%     9.43%
Without Sales Load [Member] | C000006831 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C without sales charge            
Average Annual Return, Percent 20.56%     6.85%     9.43%
Without Sales Load [Member] | C000006832 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name I without sales charge            
Average Annual Return, Percent 21.76%     7.93%     10.50%
Without Sales Load [Member] | C000006833 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R1 without sales charge            
Average Annual Return, Percent 20.55%     6.86%     9.42%
Without Sales Load [Member] | C000006835 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R2 without sales charge            
Average Annual Return, Percent 21.16%     7.40%     9.97%
Without Sales Load [Member] | C000006836 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R3 without sales charge            
Average Annual Return, Percent 21.50%     7.66%     10.25%
Without Sales Load [Member] | C000006837 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R4 without sales charge            
Average Annual Return, Percent 21.74%     7.93%     10.52%
Without Sales Load [Member] | C000006820 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A without sales charge            
Average Annual Return, Percent 12.60%     4.75%     7.73%
Without Sales Load [Member] | C000006821 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name B without sales charge            
Average Annual Return, Percent 11.75%     3.96%     6.92%
Without Sales Load [Member] | C000006822 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C without sales charge            
Average Annual Return, Percent 11.79%     3.96%     6.92%
Without Sales Load [Member] | C000006823 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name I without sales charge            
Average Annual Return, Percent 12.85%     5.00%     7.96%
Without Sales Load [Member] | C000006824 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R1 without sales charge            
Average Annual Return, Percent 11.78%     3.96%     6.92%
Without Sales Load [Member] | C000006826 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R2 without sales charge            
Average Annual Return, Percent 12.27%     4.48%     7.46%
Without Sales Load [Member] | C000006827 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R3 without sales charge            
Average Annual Return, Percent 12.61%     4.74%     7.72%
Without Sales Load [Member] | C000006828 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R4 without sales charge            
Average Annual Return, Percent 12.87%     5.01%     8.00%
Without Sales Load [Member] | C000173227 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R6 without sales charge            
Average Annual Return, Percent 12.97%     5.14%   7.86% [51]  
Without Sales Load [Member] | C000173228 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R6 without sales charge            
Average Annual Return, Percent 21.91%     8.08%   10.45% [52]  
Without Sales Load [Member] | C000006793 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name A without sales charge            
Average Annual Return, Percent 9.93%     3.45%     4.95%
Without Sales Load [Member] | C000006794 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name B without sales charge            
Average Annual Return, Percent 9.12%     2.68%     4.17%
Without Sales Load [Member] | C000173225 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R6 without sales charge            
Average Annual Return, Percent 10.30%     3.82%   5.21% [53]  
Without Sales Load [Member] | C000006801 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R4 without sales charge            
Average Annual Return, Percent 10.21%     3.69%     5.21%
Without Sales Load [Member] | C000006799 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R2 without sales charge            
Average Annual Return, Percent 9.66%     3.19%     4.69%
Without Sales Load [Member] | C000006800 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R3 without sales charge            
Average Annual Return, Percent 9.93%     3.45%     4.95%
Without Sales Load [Member] | C000006795 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name C without sales charge            
Average Annual Return, Percent 9.12%     2.68%     4.16%
Without Sales Load [Member] | C000006796 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name I without sales charge            
Average Annual Return, Percent 10.20%     3.71%     5.21%
Without Sales Load [Member] | C000006797 [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name R1 without sales charge            
Average Annual Return, Percent 9.11%     2.69%     4.18%
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 4.06% [54],[55] 3.25% [4],[6],[56],[57]   0.18% [54],[55]   1.52% [53],[58] 1.67% [54],[55]
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 31.05% [59],[60]   12.12% [1],[61] 13.14% [59],[60] 15.33% [7],[44],[62],[63] 15.13% [49],[50],[64],[65] 15.26% [59],[60]
MFS Lifetime 2065 Fund Blended Index [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name MFS Lifetime 2065 Fund Blended Index            
Average Annual Return, Percent [61] 28.01%   10.13% [1]        
MFS Lifetime 2060 Fund Blended Index [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name MFS Lifetime 2060 Fund Blended Index            
Average Annual Return, Percent [62],[63] 28.01%     10.93% 12.27% [7],[44]    
MFS Lifetime 2055 Fund Blended Index [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name MFS Lifetime 2055 Fund Blended Index            
Average Annual Return, Percent 28.01% [66],[67]     10.93% [66],[67]   11.90% [41],[68] 11.96% [66],[67]
MFS Lifetime 2045 Fund Blended Index [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name MFS Lifetime 2045 Fund Blended Index            
Average Annual Return, Percent 26.11% [69],[70]     10.36% [69],[70]   11.60% [47],[71] 11.66% [69],[70]
MFS Lifetime 2035 Fund Blended Index [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name MFS Lifetime 2035 Fund Blended Index            
Average Annual Return, Percent 19.08% [60],[72]     7.83% [60],[72]   9.79% [50],[64] 9.90% [60],[72]
MFS Lifetime 2025 Fund Blended Index [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name MFS Lifetime 2025 Fund Blended Index            
Average Annual Return, Percent 11.31% [59],[73]     3.98% [59],[73]   6.04% [49],[65] 6.21% [59],[73]
MFS Lifetime 2050 Fund Blended Index [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name MFS Lifetime 2050 Fund Blended Index            
Average Annual Return, Percent 27.95% [74],[75]     10.92% [74],[75]   11.90% [48],[76] 11.95% [74],[75]
MFS Lifetime 2030 Fund Blended Index [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name MFS Lifetime 2030 Fund Blended Index            
Average Annual Return, Percent 14.05% [77],[78]     5.59% [77],[78]   7.89% [51],[79] 8.04% [77],[78]
MFS Lifetime 2040 Fund Blended Index [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name MFS Lifetime 2040 Fund Blended Index            
Average Annual Return, Percent 24.12% [80],[81]     9.59% [80],[81]   11.01% [52],[82] 11.09% [80],[81]
MFS Lifetime Income Fund Blended Index [Member]              
Average Annual Return [Line Items]              
Line Graph and Table Measure Name MFS Lifetime Income Fund Blended Index            
Average Annual Return, Percent 11.20% [54],[55]     3.57% [54],[55]   4.87% [53],[58] 5.00% [54],[55]
[1]
For the period from the commencement of the class's investment operations, September 1, 2021 through April 30, 2026.
[2]
Assuming redemption at the end of the applicable period.
[3]
For the period from the commencement of the class's investment operations, September 1, 2021 through April 30, 2026.
[4]
For the period from the commencement of the class's investment operations, June 22, 2022 through April 30, 2026.
[5] Assuming redemption at the end of the applicable period.
[6] For the period from the commencement of the class's investment operations, June 22, 2022 through April 30, 2026.
[7]
For the period from the commencement of the class's investment operations, December 6, 2016 through April 30, 2026.
[8]
Assuming redemption at the end of the applicable period.
[9]
For the period from the commencement of the class's investment operations, December 6, 2016 through April 30, 2026.
[10]
Assuming redemption at the end of the applicable period.
[11]
For the period from the commencement of the class's investment operations, December 6, 2016 through April 30, 2026.
[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]
Assuming redemption at the end of the applicable period.
[20]
Assuming redemption at the end of the applicable period.
[21]
Assuming redemption at the end of the applicable period.
[22]
Assuming redemption at the end of the applicable period.
[23]
Assuming redemption at the end of the applicable period.
[24]
Assuming redemption at the end of the applicable period.
[25] Assuming redemption at the end of the applicable period.
[26]
Assuming redemption at the end of the applicable period.
[27] Assuming redemption at the end of the applicable period.
[28]
For the period from the commencement of the class's investment operations, September 1, 2021 through April 30, 2026.
[29]
For the period from the commencement of the class's investment operations, September 1, 2021 through April 30, 2026.
[30]
For the period from the commencement of the class's investment operations, September 1, 2021 through April 30, 2026.
[31]
For the period from the commencement of the class's investment operations, September 1, 2021 through April 30, 2026.
[32]
For the period from the commencement of the class's investment operations, September 1, 2021 through April 30, 2026.
[33]
For the period from the commencement of the class's investment operations, September 1, 2021 through April 30, 2026.
[34]
For the period from the commencement of the class's investment operations, June 22, 2022 through April 30, 2026.
[35]
For the period from the commencement of the class's investment operations, June 22, 2022 through April 30, 2026.
[36]
For the period from the commencement of the class's investment operations, June 22, 2022 through April 30, 2026.
[37]
For the period from the commencement of the class's investment operations, June 22, 2022 through April 30, 2026.
[38] For the period from the commencement of the class's investment operations, June 22, 2022 through April 30, 2026.
[39] For the period from the commencement of the class's investment operations, June 22, 2022 through April 30, 2026.
[40]
For the period from the commencement of the class's investment operations, December 6, 2016 through April 30, 2026.
[41]
For the period from the commencement of the class's investment operations, August 29, 2016 through April 30, 2026.
[42]
For the period from the commencement of the class's investment operations, December 6, 2016 through April 30, 2026.
[43]
For the period from the commencement of the class's investment operations, December 6, 2016 through April 30, 2026.
[44] For the period from the commencement of the class's investment operations, December 6, 2016 through April 30, 2026.
[45]
For the period from the commencement of the class's investment operations, December 6, 2016 through April 30, 2026.
[46]
For the period from the commencement of the class's investment operations, December 6, 2016 through April 30, 2026.
[47]
For the period from the commencement of the class's investment operations, August 29, 2016 through April 30, 2026.
[48]
For the period from the commencement of the class's investment operations, August 29, 2016 through April 30, 2026.
[49] For the period from the commencement of the class's investment operations, August 29, 2016 through April 30, 2026.
[50]
For the period from the commencement of the class's investment operations, August 29, 2016 through April 30, 2026.
[51]
For the period from the commencement of the class's investment operations, August 29, 2016 through April 30, 2026.
[52] For the period from the commencement of the class's investment operations, August 29, 2016 through April 30, 2026.
[53] For the period from the commencement of the class's investment operations, August 29, 2016 through April 30, 2026.
[54]
Source: FactSet Research Systems Inc.
[55] Source: FactSet Research Systems Inc.
[56]
Source: FactSet Research Systems Inc.
[57] Source: FactSet Research Systems Inc.
[58] Source: FactSet Research Systems Inc.
[59]
Source: FactSet Research Systems Inc.
[60] Source: FactSet Research Systems Inc.
[61]
Source: FactSet Research Systems Inc.
[62]
Source: FactSet Research Systems Inc.
[63] Source: FactSet Research Systems Inc.
[64]
Source: FactSet Research Systems Inc.
[65] Source: FactSet Research Systems Inc.
[66]
Source: FactSet Research Systems Inc.
[67] Source: FactSet Research Systems Inc.
[68]
Source: FactSet Research Systems Inc.
[69]
Source: FactSet Research Systems Inc.
[70] Source: FactSet Research Systems Inc.
[71]
Source: FactSet Research Systems Inc.
[72]
Source: FactSet Research Systems Inc.
[73] Source: FactSet Research Systems Inc.
[74]
Source: FactSet Research Systems Inc.
[75] Source: FactSet Research Systems Inc.
[76]
Source: FactSet Research Systems Inc.
[77]
Source: FactSet Research Systems Inc.
[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.