XML 89 R64.htm IDEA: XBRL DOCUMENT v3.20.2
Risk Management Activities and Derivative Transactions Currency Swaps Outstanding (Details)
$ in Millions
9 Months Ended
Jun. 30, 2020
USD ($)
Bond_issues
Sep. 30, 2019
Bond_issues
Derivative    
Number of British pound sterling denominated bond transactions 3  
Number of currency swaps outstanding   3
Associated TVA bond issues currency exposure | $ $ 600  
Minimum    
Derivative    
Expiration date range of swaps 2021  
Maximum    
Derivative    
Expiration date range of swaps 2043