v3.26.1
Average Annual Total Returns - LOOMIS SAYLES FUNDS II
 12 Months Ended 60 Months Ended 61 Months Ended 109 Months Ended 120 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Loomis Sayles High Income Fund | Bloomberg U.S. Corporate High Yield Bond Index          
Prospectus [Line Items]          
Average Annual Return, Percent 8.62% 4.51%   5.55% 6.53%
Loomis Sayles High Income Fund | Bloomberg U.S. Aggregate Bond Index          
Prospectus [Line Items]          
Average Annual Return, Percent 7.30% (0.36%)   1.93% 2.01%
Loomis Sayles High Income Fund | Class A          
Prospectus [Line Items]          
Average Annual Return, Percent 4.25% 2.05%     4.77%
Loomis Sayles High Income Fund | Class C          
Prospectus [Line Items]          
Average Annual Return, Percent 6.99% 2.12%     4.61%
Loomis Sayles High Income Fund | Class N          
Prospectus [Line Items]          
Average Annual Return, Percent 9.19% 3.23%   4.69%  
Loomis Sayles High Income Fund | Class Y          
Prospectus [Line Items]          
Average Annual Return, Percent 9.16% 3.19%     5.51%
Loomis Sayles High Income Fund | Class Y | After Taxes on Distributions          
Prospectus [Line Items]          
Average Annual Return, Percent 6.38% 0.55%     3.11%
Loomis Sayles High Income Fund | Class Y | After Taxes on Distributions and Sales          
Prospectus [Line Items]          
Average Annual Return, Percent 5.36% 1.23%     3.19%
Loomis Sayles International Growth Fund | MSCI All Country World ex USA Index (Net)          
Prospectus [Line Items]          
Average Annual Return, Percent 32.39% 7.91% 8.31%    
Loomis Sayles International Growth Fund | Class A          
Prospectus [Line Items]          
Average Annual Return, Percent 3.54% 2.19% 2.45%    
Loomis Sayles International Growth Fund | Class C          
Prospectus [Line Items]          
Average Annual Return, Percent 8.01% 2.61% 2.86%    
Loomis Sayles International Growth Fund | Class N          
Prospectus [Line Items]          
Average Annual Return, Percent 10.15% 3.71% 3.96%    
Loomis Sayles International Growth Fund | Class Y          
Prospectus [Line Items]          
Average Annual Return, Percent 10.09% 3.67% 3.92%    
Loomis Sayles International Growth Fund | Class Y | After Taxes on Distributions          
Prospectus [Line Items]          
Average Annual Return, Percent 9.67% 3.47% 3.72%    
Loomis Sayles International Growth Fund | Class Y | After Taxes on Distributions and Sales          
Prospectus [Line Items]          
Average Annual Return, Percent 6.33% 2.87% 3.07%    
Loomis Sayles Investment Grade Bond Fund | Bloomberg U.S. Aggregate Bond Index          
Prospectus [Line Items]          
Average Annual Return, Percent 7.30% (0.36%)     2.01%
Loomis Sayles Investment Grade Bond Fund | Class A          
Prospectus [Line Items]          
Average Annual Return, Percent 2.28% (0.12%)     3.05%
Loomis Sayles Investment Grade Bond Fund | Class C          
Prospectus [Line Items]          
Average Annual Return, Percent 5.01% 0.00%     2.87%
Loomis Sayles Investment Grade Bond Fund | Class N          
Prospectus [Line Items]          
Average Annual Return, Percent 7.12% 1.06%     3.82%
Loomis Sayles Investment Grade Bond Fund | Class Y          
Prospectus [Line Items]          
Average Annual Return, Percent 6.96% 1.00%     3.74%
Loomis Sayles Investment Grade Bond Fund | Class Y | After Taxes on Distributions          
Prospectus [Line Items]          
Average Annual Return, Percent 4.85% (0.69%)     1.99%
Loomis Sayles Investment Grade Bond Fund | Class Y | After Taxes on Distributions and Sales          
Prospectus [Line Items]          
Average Annual Return, Percent 4.09% 0.05%     2.21%
Loomis Sayles Investment Grade Bond Fund | Admin Class          
Prospectus [Line Items]          
Average Annual Return, Percent 6.44% 0.49%     3.24%
Loomis Sayles Strategic Income Fund | Bloomberg U.S. Aggregate Bond Index          
Prospectus [Line Items]          
Average Annual Return, Percent 7.30% (0.36%)     2.01%
Loomis Sayles Strategic Income Fund | Class A          
Prospectus [Line Items]          
Average Annual Return, Percent 5.62% 2.01%     3.38%
Loomis Sayles Strategic Income Fund | Class C          
Prospectus [Line Items]          
Average Annual Return, Percent 8.36% 2.12%     3.21%
Loomis Sayles Strategic Income Fund | Class N          
Prospectus [Line Items]          
Average Annual Return, Percent 10.62% 3.22%     4.17%
Loomis Sayles Strategic Income Fund | Class Y          
Prospectus [Line Items]          
Average Annual Return, Percent 10.56% 3.16%     4.10%
Loomis Sayles Strategic Income Fund | Class Y | After Taxes on Distributions          
Prospectus [Line Items]          
Average Annual Return, Percent 8.22% 1.03%     2.19%
Loomis Sayles Strategic Income Fund | Class Y | After Taxes on Distributions and Sales          
Prospectus [Line Items]          
Average Annual Return, Percent 6.22% 1.46%     2.36%
Loomis Sayles Strategic Income Fund | Admin Class          
Prospectus [Line Items]          
Average Annual Return, Percent 9.95% 2.65%     3.58%