v3.20.2
Basis of Presentation and Summary of Significant Accounting Policies - Components of Restricted Cash (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Jun. 30, 2020
Dec. 31, 2019
Accounting Policies [Line Items]      
Current   $ 225 $ 299
Non-current   16 46
Total   241 345
Debt service      
Accounting Policies [Line Items]      
Current   55 58
Non-current   8 8
Total   63 66
Construction major maintenance      
Accounting Policies [Line Items]      
Current   35 28
Non-current   7 6
Total   42 34
Margin Deposits Received/Returned to PG&E [Member]      
Accounting Policies [Line Items]      
Total   119  
Security project insurance      
Accounting Policies [Line Items]      
Current   130 209
Non-current   0 31
Total   130 240
Other      
Accounting Policies [Line Items]      
Current   5 4
Non-current   1 1
Total   $ 6 $ 5
Subsequent Event | Debt service      
Accounting Policies [Line Items]      
Total $ 52    
Subsequent Event | Construction major maintenance      
Accounting Policies [Line Items]      
Total 2    
Subsequent Event | Security project insurance      
Accounting Policies [Line Items]      
Total $ 34