v3.19.3
Derivative Instruments (Textuals) (Details) - USD ($)
 3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Derivatives, Fair Value [Line Items]          
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net   $ 0   $ 1,000,000  
Current Derivatives Assets, net of Collateral $ (7,000,000)   $ (7,000,000)   $ (58,000,000)
Long-Term Derivative Assets, net of Collateral (6,000,000)   (6,000,000)   (8,000,000)
Current Derivative Liabilities, net of Collateral 92,000,000   92,000,000   49,000,000
Long-term Derivative Liabilities, net of Collateral 11,000,000   11,000,000   64,000,000
Derivative, Collateral, Right to Reclaim Cash 116,000,000   116,000,000   244,000,000
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax (1,000,000) (1,000,000) $ (2,000,000) (3,000,000)  
Summary of Derivative Instruments [Abstract]          
Maximum length of time hedging using interest rate derivative instruments     6 years    
Derivative, Net Liability Position, Aggregate Fair Value 136,000,000   $ 136,000,000    
Collateral Already Posted, Aggregate Fair Value 89,000,000   89,000,000    
Gain (Loss) on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net 0 $ 0 2,000,000 $ 0  
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months     25,000,000    
Parent [Member]          
Derivatives, Fair Value [Line Items]          
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax 90,000,000   90,000,000   34,000,000
Noncontrolling Interest [Member]          
Derivatives, Fair Value [Line Items]          
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax $ 4,000,000   $ 4,000,000   $ 3,000,000