XML 135 R1.htm IDEA: XBRL DOCUMENT v3.20.1
DEI Document - USD ($)
shares in Millions, $ in Millions
 3 Months Ended 6 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Mar. 31, 2020
Mar. 31, 2019
Document Information [Line Items]        
Other revenue $ 32 $ 38 $ 78 $ 82
Defined Benefit Plan, Other Cost (Credit) $ 62 $ 65 $ 127 $ 129
Entity Registrant Name     Tennessee Valley Authority  
Entity Central Index Key     0001376986  
Current Fiscal Year End Date     --09-30  
Entity Filer Category     Non-accelerated Filer  
Entity Small Business     false  
Entity Emerging Growth Company     false  
Document Type     10-Q  
Document Period End Date     Mar. 31, 2020  
Document Fiscal Year Focus     2020  
Document Fiscal Period Focus     Q2  
Amendment Flag     false  
Entity Common Stock, Shares Outstanding 0   0  
Entity Current Reporting Status     Yes  
Entity Shell Company     false