v3.20.1
Derivative Instruments (Textuals) (Details) - USD ($)
 3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Dec. 31, 2019
Derivatives, Fair Value [Line Items]      
Current Derivatives Assets, net of Collateral $ (14,000,000)   $ (4,000,000)
Long-Term Derivative Assets, net of Collateral (13,000,000)   (4,000,000)
Current Derivative Liabilities, net of Collateral 22,000,000   108,000,000
Long-term Derivative Liabilities, net of Collateral 48,000,000   14,000,000
Derivative, Collateral, Right to Reclaim Cash 191,000,000   191,000,000
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax $ (3,000,000) $ 0  
Summary of Derivative Instruments [Abstract]      
Maximum length of time hedging using interest rate derivative instruments 6 years    
Derivative, Net Liability Position, Aggregate Fair Value $ 153,000,000    
Collateral Already Posted, Aggregate Fair Value 104,000,000    
Gain (Loss) on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net 0 $ 1,000,000  
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months 55,000,000    
Additional Collateral, Aggregate Fair Value 1,000,000    
Parent      
Derivatives, Fair Value [Line Items]      
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax 176,000,000   72,000,000
Noncontrolling Interest      
Derivatives, Fair Value [Line Items]      
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax $ 0   $ 3,000,000