v3.26.1
Average Annual Total Returns - American Century Government Income Trust
 12 Months Ended 60 Months Ended 89 Months Ended 120 Months Ended
Aug. 01, 2026
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2025
Bloomberg U.S. Aggregate Bond Index          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Bloomberg U.S. Aggregate Bond Index     (reflects no deduction for fees, expenses or taxes)        
Average Annual Return, Percent   7.30% (0.36%)   2.01%
Bloomberg U.S. GNMA Index          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Bloomberg U.S. GNMA Index    (reflects no deduction for fees, expenses or taxes)        
Average Annual Return, Percent   8.08% 0.23%   1.50%
Bloomberg U.S. Government/MBS Index          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Bloomberg U.S. Government/MBS Index      (reflects no deduction for fees, expenses or taxes)        
Average Annual Return, Percent   7.09% (0.53%)   1.46%
Bloomberg U.S. 1-3 Year Government Bond Index          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Bloomberg U.S. 1-3 Year Government Bond Index    (reflects no deduction for fees, expenses or taxes)        
Average Annual Return, Percent   5.17% 1.76%   1.84%
Bloomberg U.S. Treasury Inflation Protected Securities (TIPS) Index          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Bloomberg U.S. Treasury Inflation Protected Securities (TIPS) Index    (reflects no deduction for fees, expenses or taxes)        
Average Annual Return, Percent   7.01% 1.12%   3.09%
CAPITAL PRESERVATION FUND INVESTOR CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Investor Class        
Average Annual Return, Percent   3.87% 2.89%   1.82%
GINNIE MAE FUND INVESTOR CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Investor Class Return Before Taxes        
Average Annual Return, Percent   7.41% (0.33%)   1.07%
GINNIE MAE FUND INVESTOR CLASS | After Taxes on Distributions          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Return After Taxes on Distributions        
Average Annual Return, Percent   5.72% (1.54%)   (0.06%)
GINNIE MAE FUND INVESTOR CLASS | After Taxes on Distributions and Sales          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Return After Taxes on Distributions and Sale of Fund Shares        
Average Annual Return, Percent   4.36% (0.77%)   0.33%
GINNIE MAE FUND I CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] [1] I Class1 Return Before Taxes        
Average Annual Return, Percent [1]   7.51% (0.23%)   1.17%
GINNIE MAE FUND A CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] A Class Return Before Taxes        
Average Annual Return, Percent   2.32% (1.49%)   0.36%
GINNIE MAE FUND C CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] [2] C Class2 Return Before Taxes        
Average Annual Return, Percent [2]   6.34% (1.32%)   0.21%
GINNIE MAE FUND R CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] R Class Return Before Taxes        
Average Annual Return, Percent   7.00% (0.82%)   0.57%
GINNIE MAE FUND R5 CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] R5 Class Return Before Taxes        
Average Annual Return, Percent   7.62% (0.13%)   1.27%
GOVERNMENT BOND FUND INVESTOR CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Investor Class Return Before Taxes        
Average Annual Return, Percent   7.24% (0.76%)   1.22%
GOVERNMENT BOND FUND INVESTOR CLASS | After Taxes on Distributions          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Return After Taxes on Distributions        
Average Annual Return, Percent   5.46% (2.07%)   0.08%
GOVERNMENT BOND FUND INVESTOR CLASS | After Taxes on Distributions and Sales          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Return After Taxes on Distributions and Sale of Fund Shares        
Average Annual Return, Percent   4.25% (1.12%)   0.45%
GOVERNMENT BOND FUND I CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] [3] I Class1 Return Before Taxes        
Average Annual Return, Percent [3]   7.23% (0.67%)   1.31%
GOVERNMENT BOND FUND A CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] A Class Return Before Taxes        
Average Annual Return, Percent   2.16% (1.92%)   0.51%
GOVERNMENT BOND FUND C CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] [4] C Class2 Return Before Taxes        
Average Annual Return, Percent [4]   6.06% (1.75%)   0.38%
GOVERNMENT BOND FUND R CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] R Class Return Before Taxes        
Average Annual Return, Percent   6.59% (1.26%)   0.72%
GOVERNMENT BOND FUND R5 CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] R5 Class Return Before Taxes        
Average Annual Return, Percent   7.45% (0.56%)   1.43%
SHORT-TERM GOVERNMENT FUND INVESTOR CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Investor Class Return Before Taxes        
Average Annual Return, Percent   4.91% 1.57%   1.58%
SHORT-TERM GOVERNMENT FUND INVESTOR CLASS | After Taxes on Distributions          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Return After Taxes on Distributions        
Average Annual Return, Percent   3.34% 0.41%   0.75%
SHORT-TERM GOVERNMENT FUND INVESTOR CLASS | After Taxes on Distributions and Sales          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Return After Taxes on Distributions and Sale of Fund Shares        
Average Annual Return, Percent   2.89% 0.70%   0.85%
SHORT-TERM GOVERNMENT FUND I CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] [5] I Class1 Return Before Taxes        
Average Annual Return, Percent [5]   5.02% 1.65%   1.67%
SHORT-TERM GOVERNMENT FUND A CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] A Class Return Before Taxes        
Average Annual Return, Percent   2.30% 0.83%   1.10%
SHORT-TERM GOVERNMENT FUND C CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] [6] C Class2 Return Before Taxes        
Average Annual Return, Percent [6]   3.89% 0.54%   0.72%
SHORT-TERM GOVERNMENT FUND R CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] R Class Return Before Taxes        
Average Annual Return, Percent   4.40% 1.06%   1.07%
SHORT-TERM GOVERNMENT FUND R5 CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] R5 Class Return Before Taxes        
Average Annual Return, Percent   5.12% 1.77%   1.78%
INFLATION-ADJUSTED BOND FUND INVESTOR CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Investor Class Return Before Taxes        
Average Annual Return, Percent   6.67% 0.84%   2.70%
Performance Inception Date Feb. 10, 1997        
INFLATION-ADJUSTED BOND FUND INVESTOR CLASS | After Taxes on Distributions          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Return After Taxes on Distributions        
Average Annual Return, Percent   4.85% (0.95%)   1.33%
Performance Inception Date Feb. 10, 1997        
INFLATION-ADJUSTED BOND FUND INVESTOR CLASS | After Taxes on Distributions and Sales          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] Return After Taxes on Distributions and Sale of Fund Shares        
Average Annual Return, Percent   3.94% (0.12%)   1.48%
Performance Inception Date Feb. 10, 1997        
INFLATION-ADJUSTED BOND FUND I CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] [7] I Class1 Return Before Taxes        
Average Annual Return, Percent [7]   6.69% 0.95%   2.80%
Performance Inception Date [7] Apr. 10, 2017        
INFLATION-ADJUSTED BOND FUND Y CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] [7] Y Class1 Return Before Taxes        
Average Annual Return, Percent [7]   6.80% 1.03%   2.90%
Performance Inception Date [7] Apr. 10, 2017        
INFLATION-ADJUSTED BOND FUND A CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] A Class Return Before Taxes        
Average Annual Return, Percent   1.54% (0.33%)   1.97%
Performance Inception Date Jun. 15, 1998        
INFLATION-ADJUSTED BOND FUND C CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] [8] C Class2 Return Before Taxes        
Average Annual Return, Percent [8]   5.64% (0.15%)   1.82%
Performance Inception Date [8] Mar. 01, 2010        
INFLATION-ADJUSTED BOND FUND R CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] R Class Return Before Taxes        
Average Annual Return, Percent   6.12% 0.34%   2.18%
Performance Inception Date Mar. 01, 2010        
INFLATION-ADJUSTED BOND FUND R5 CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] R5 Class Return Before Taxes        
Average Annual Return, Percent   6.90% 1.05%   2.91%
Performance Inception Date Oct. 01, 2002        
INFLATION-ADJUSTED BOND FUND R6 CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] R6 Class Return Before Taxes        
Average Annual Return, Percent   6.96% 1.10% 2.73%  
Performance Inception Date Jul. 28, 2017        
INFLATION-ADJUSTED BOND FUND G CLASS          
Prospectus [Line Items]          
Average Annual Return, Label [Optional Text] G Class Return Before Taxes        
Average Annual Return, Percent   7.18% 1.31% 2.95%  
Performance Inception Date Jul. 28, 2017        
[1] Historical performance for the I Class prior to its inception (April 10, 2017) is based on the performance of R5 Class shares. I Class performance has been adjusted to reflect differences in expenses between classes, if applicable.
[2] C Class shares automatically convert to A Class shares after approximately eight years. All returns for periods greater than eight years reflect this conversion.
[3] Historical performance for the I Class prior to its inception (April 10, 2017) is based on the performance of R5 Class shares. I Class performance has been adjusted to reflect differences in expenses between classes, if applicable.
[4] C Class shares automatically convert to A Class shares after approximately eight years. All returns for periods greater than eight years reflect this conversion.
[5] Historical performance for the I Class prior to its inception (April 10, 2017) is based on the performance of R5 Class shares. I Class performance has been adjusted to reflect differences in expenses between classes, if applicable.
[6] C Class shares automatically convert to A Class shares after approximately eight years. All returns for periods greater than eight years reflect this conversion.
[7] Historical performance for the I and Y Classes prior to their inception is based on the performance of R5 Class shares. I and Y Class performance has been adjusted to reflect differences in expenses between classes, if applicable.
[8] C Class shares automatically convert to A Class shares after approximately eight years. All returns for periods greater than eight years reflect this conversion.