Derivative Instruments (Textuals) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Current Derivatives Assets, net of Collateral	$ (17)		$ (58)
Long-Term Derivative Assets, net of Collateral	(3)		(8)
Current Derivative Liabilities, net of Collateral	76		49
Derivative, Collateral, Right to Reclaim Cash	187		244
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	$ 0	$ (11)
Summary of Derivative Instruments [Abstract]
Maximum length of time hedging using interest rate derivative instruments	7 years
Derivative, Net Liability Position, Aggregate Fair Value	$ 228
Collateral Already Posted, Aggregate Fair Value	139
Additional Collateral, Aggregate Fair Value	4
Long-term Derivative Liabilities, net of Collateral	69		64
Gain (Loss) on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	(1)	$ 0
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	59		34
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	$ 3		$ 3

Collateral Offset in Current Derivative Liabilities

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Collateral Offset in Current Derivatives Assets

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Collateral Offset in Long-Term Derivative Assets

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Collateral Offset in Long-term Derivative Liabilities

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Accumulated change, net of tax, in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

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The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

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The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

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Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The amount of net gain (loss) reclassified into earnings in the period when cash flow hedge is discontinued because it is probable that the original forecasted transactions will not occur by the end of the original period or an additional two month time period.

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Maximum period the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of tax expense (benefit), after reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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