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Label Element Value
Prospectus: rr_ProspectusTable  
Document Type dei_DocumentType 497
Document Period End Date dei_DocumentPeriodEndDate May 14, 2020
Entity Registrant Name dei_EntityRegistrantName AMERICAN CENTURY GOVERNMENT INCOME TRUST
Central Index Key dei_EntityCentralIndexKey 0000773674
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate May 14, 2020
Document Effective Date dei_DocumentEffectiveDate May 15, 2020
Prospectus Date rr_ProspectusDate Aug. 01, 2019
American Century Government Income Trust  
Prospectus: rr_ProspectusTable  
Supplement [Text Block] ck0000773674_SupplementTextBlock
American Century Government Income Trust
Summary Prospectus and Prospectus Supplement
Inflation-Adjusted Bond Fund
 
Supplement dated May 15, 2020 n Summary Prospectus and Prospectus dated August 1, 2019


The following replaces the Average Annual Total Returns table on page 5 of the summary prospectus and the prospectus:

Average Annual Total Returns
For the calendar year ended December 31, 2018
1 year
5 years
10 years
Since Inception
Inception
Date
Investor Class Return Before Taxes
-2.51%
1.12%
3.05%
—
02/10/1997
   Return After Taxes on Distributions
-3.66%
0.28%
2.11%
—
02/10/1997
   Return After Taxes on Distributions and Sale of Fund Shares
-1.48%
0.50%
2.05%
—
02/10/1997
I Class1 Return Before Taxes
-2.33%
1.21%
3.16%
—
04/10/2017
Y Class1 Return Before Taxes
-2.23%
1.32%
3.26%
—
04/10/2017
A Class2 Return Before Taxes
-7.08%
-0.05%
2.33%
—
06/15/1998
C Class3 Return Before Taxes
-3.49%
0.13%
2.03%
—
03/01/2010
R Class3 Return Before Taxes
-2.99%
0.63%
2.54%
—
03/01/2010
R5 Class Return Before Taxes
-2.23%
1.33%
3.27%
—
10/01/2002
R6 Class Return Before Taxes
-2.27%
—
—
-0.43%
07/28/2017
G Class Return Before Taxes
-1.98%
—
—
-0.18%
07/28/2017
Bloomberg Barclays U.S. Treasury Inflation
Protected Securities (TIPS) Index
   (reflects no deduction for fees, expenses or taxes)
-1.26%
1.69%
3.64%
 
 

1 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.
2 Prior to March 1, 2010, the A Class was referred to as the Advisor Class and did not have a front-end sales charge. Performance prior to that date has been restated to reflect this charge.
3 Historical performance for the C and R Classes prior to their inception is based on the performance of Investor Class shares. C and R Class performance has been adjusted to reflect differences in sales charges, if applicable, and expenses between classes.
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading Inflation-Adjusted Bond Fund
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2018
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | Bloomberg Barclays U.S. Treasury Inflation Protected Securities (TIPS) Index (reflects no deduction for fees, expenses or taxes)  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses or taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Barclays U.S. Treasury Inflation Protected Securities (TIPS) Index    (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 (1.26%)
5 Years rr_AverageAnnualReturnYear05 1.69%
10 Years rr_AverageAnnualReturnYear10 3.64%
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (2.51%)
5 Years rr_AverageAnnualReturnYear05 1.12%
10 Years rr_AverageAnnualReturnYear10 3.05%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 10, 1997
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel    Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (3.66%)
5 Years rr_AverageAnnualReturnYear05 0.28%
10 Years rr_AverageAnnualReturnYear10 2.11%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 10, 1997
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | INVESTOR CLASS | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel    Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 (1.48%)
5 Years rr_AverageAnnualReturnYear05 0.50%
10 Years rr_AverageAnnualReturnYear10 2.05%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 10, 1997
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | I CLASS  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel I Class Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (2.33%) [1]
5 Years rr_AverageAnnualReturnYear05 1.21% [1]
10 Years rr_AverageAnnualReturnYear10 3.16% [1]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 10, 2017 [1]
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | Y CLASS  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Y Class Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (2.23%) [1]
5 Years rr_AverageAnnualReturnYear05 1.32% [1]
10 Years rr_AverageAnnualReturnYear10 3.26% [1]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 10, 2017 [1]
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | A CLASS  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel A Class Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (7.08%) [2]
5 Years rr_AverageAnnualReturnYear05 (0.05%) [2]
10 Years rr_AverageAnnualReturnYear10 2.33% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 15, 1998 [2]
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | C CLASS  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel C Class Return Before Taxes [3]
1 Year rr_AverageAnnualReturnYear01 (3.49%) [3]
5 Years rr_AverageAnnualReturnYear05 0.13% [3]
10 Years rr_AverageAnnualReturnYear10 2.03% [3]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010 [3]
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | R CLASS  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel R Class Return Before Taxes [3]
1 Year rr_AverageAnnualReturnYear01 (2.99%) [3]
5 Years rr_AverageAnnualReturnYear05 0.63% [3]
10 Years rr_AverageAnnualReturnYear10 2.54% [3]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010 [3]
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | R5 CLASS  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel R5 Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (2.23%)
5 Years rr_AverageAnnualReturnYear05 1.33%
10 Years rr_AverageAnnualReturnYear10 3.27%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 01, 2002
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | R6 CLASS  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel R6 Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (2.27%)
Since Inception rr_AverageAnnualReturnSinceInception (0.43%)
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 28, 2017
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | G CLASS  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel G Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (1.98%)
Since Inception rr_AverageAnnualReturnSinceInception (0.18%)
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 28, 2017
[1] 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.
[2] Prior to March 1, 2010, the A Class was referred to as the Advisor Class and did not have a front-end sales charge. Performance prior to that date has been restated to reflect this charge.
[3] Historical performance for the C and R Classes prior to their inception is based on the performance of Investor Class shares. C and R Class performance has been adjusted to reflect differences in sales charges, if applicable, and expenses between classes.