XML 72 R44.htm IDEA: XBRL DOCUMENT v3.21.2
Summary of Significant Accounting Policies General and Basis of Presentation (Details)
$ in Millions
 3 Months Ended 9 Months Ended
Jun. 30, 2021
USD ($)
People
Jun. 30, 2020
USD ($)
Jun. 30, 2021
USD ($)
People
Jun. 30, 2020
USD ($)
Sep. 30, 2020
USD ($)
Sep. 30, 2019
USD ($)
Accounting Policies [Abstract]            
Cash and Cash Equivalents, at Carrying Value $ 500   $ 500   $ 500  
Restricted Cash and Cash Equivalents 19   19   21  
Regulatory Assets 9,314   9,314   10,375  
Appropriation-investment power program         1,000  
Financing Receivable, after Allowance for Credit Loss $ 109   $ 109   93  
Population of TVA's service area | People 10   10      
Allowance for uncollectible accounts $ 1   $ 1      
Depreciation expense 347 $ 344 1,000 $ 1,300    
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents $ 519 $ 823 $ 519 823 $ 521 $ 322
Cash and Cash Equivalents, Period Increase (Decrease)       $ 501