XML 34 R1.htm IDEA: XBRL DOCUMENT v3.19.2
DEI Document - USD ($)
shares in Millions, $ in Millions
 3 Months Ended 9 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Document Information [Line Items]        
Other revenue $ 39 $ 38 $ 121 $ 117
Defined Benefit Plan, Other Cost (Credit) $ 65 $ 65 $ 194 $ 193
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     Jun. 30, 2019  
Document Fiscal Year Focus     2019  
Document Fiscal Period Focus     Q3  
Amendment Flag     false  
Entity Common Stock, Shares Outstanding 0   0  
Entity Current Reporting Status     Yes  
Entity Shell Company     false