XML 72 R53.htm IDEA: XBRL DOCUMENT v3.20.4
Summary of Significant Accounting Policies (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Regulatory Assets and Liabilities Disclosure [Abstract]    
Regulatory Assets, Current $ 64 $ 72
Regulatory Assets, Noncurrent 442 466
Total regulatory assets 506 538
Regulatory Liabilities, Current 59 60
Regulatory Liabilities, Noncurrent 1,314 1,277
Total regulatory liabilities 1,373 1,337
Leases [Abstract]    
Operating Lease, Right-of-Use Asset $ 182 $ 207
Interest Capitalized [Abstract]    
Minimum period of construction for capitalization of interest 3 months  
Minimum total project cost for capitalization of interest $ 1  
Retirement Benefits, Description [Abstract]    
Threshold For Amortization Of Unrecognized Actuarial Gains Losses 10.00%  
Pension Benefits [Member]    
Retirement Benefits, Description [Abstract]    
Approximate Amortization Period Of Net Actuarial Gain Loss 10 years  
Amortization Period Of Difference Between Expected And Actual Return On Plan Assets 5 years  
Other Postretirement Benefits [Member]    
Retirement Benefits, Description [Abstract]    
Approximate Amortization Period Of Net Actuarial Gain Loss 6 years  
Land [Member]    
Leases [Abstract]    
Lessee, Operating Lease, Term of Contract 108 years  
Maximum [Member]    
Leases [Abstract]    
Lessee, Operating Lease, Term of Contract 20 years  
Maximum [Member] | Pension Benefits [Member]    
Retirement Benefits, Description [Abstract]    
Threshold For Market Related Value 110.00%  
Minimum [Member]    
Leases [Abstract]    
Lessee, Operating Lease, Term of Contract 1 year  
Minimum [Member] | Pension Benefits [Member]    
Retirement Benefits, Description [Abstract]    
Threshold For Market Related Value 90.00%