Derivative Instruments (Details 2) (Details) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative Asset	[1]	$ 302	$ 392
Derivative Liability	[1]	443	316
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		40	26
Derivative Liability		10	31
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		262	366
Derivative Liability		433	285
Energy Related Derivative [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		262	366
Derivative Liability		433	285
Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		40	29
Derivative Liability		10	34
Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		40	26
Derivative Liability		$ 10	$ 31

[1] At December 31, 2018 and 2017, we had $244 million and $155 million of collateral under master netting arrangements that were not offset against our derivative instruments on the Consolidated Balance Sheets primarily related to initial margin requirements.