XML 67 R31.htm IDEA: XBRL DOCUMENT v3.19.3
Regulatory - Schedule of Regulatory Assets and Regulatory Liabilities (Detail) - USD ($)
$ in Millions
Sep. 30, 2019
Dec. 31, 2018
Regulatory assets:    
Regulatory assets $ 445 $ 458
Less: Current portion 55 88
Long-term regulatory assets 390 370
Regulatory liabilities:    
Regulatory liabilities 1,311 1,310
Less: Current portion 83 44
Long-term regulatory liabilities 1,228 1,266
Regulatory Tax Asset [Member]    
Regulatory assets:    
Regulatory assets 74 56
Cost-Recovery Clauses [Member]    
Regulatory assets:    
Regulatory assets 30 55
Environmental Remediation [Member]    
Regulatory assets:    
Regulatory assets 27 23
Postretirement Benefits [Member]    
Regulatory assets:    
Regulatory assets 285 295
Storm Reserve [Member]    
Regulatory assets:    
Regulatory assets 2 3
Asset Retirement Obligation [Member]    
Regulatory assets:    
Regulatory assets 19 18
Other [Member]    
Regulatory assets:    
Regulatory assets 8 8
Regulatory Tax Liability [Member] | Non-Current Liabilities [Member]    
Regulatory liabilities:    
Regulatory liabilities 710 715
Cost-Recovery Clauses [Member]    
Regulatory liabilities:    
Regulatory liabilities 30 17
Storm Reserve [Member]    
Regulatory liabilities:    
Regulatory liabilities 48 56
Accumulated Reserve - Cost of Removal [Member]    
Regulatory liabilities:    
Regulatory liabilities 507 513
Other [Member]    
Regulatory liabilities:    
Regulatory liabilities $ 16 $ 9