Derivative Instruments (Textuals) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Current Derivatives Assets, net of Collateral	$ (28)		$ (28)		$ (4)
Long-Term Derivative Assets, net of Collateral	(9)		(9)		(4)
Current Derivative Liabilities, net of Collateral	1		1		108
Long-term Derivative Liabilities, net of Collateral	43		43		14
Derivative, Collateral, Right to Reclaim Cash	260		260		191
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	(1)	$ 1	$ 2	$ 1
Summary of Derivative Instruments [Abstract]
Maximum length of time hedging using interest rate derivative instruments			7 years
Derivative, Net Liability Position, Aggregate Fair Value	120		$ 120
Collateral Already Posted, Aggregate Fair Value	37		37
Gain (Loss) on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	16	$ 0	16	$ 1
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months			57
Additional Collateral, Aggregate Fair Value	6		6
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	174		174		72
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		$ 0		$ 3