Fair Value Measurement Fair Value Measurement - Schedule of Level 3 Inputs Reconciliation for Liabilities (Details) - Derivative Financial Instruments, Liabilities [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (27)	$ (43)	$ (38)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	(17)	(9)	(20)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	0	0
Purchases	0	0	0
Sales	0	0	0
Issuances	(33)	(20)	(15)
Settlements	40	36	29
Transfers Into Level 3	0	0	0
Transfers Out of Level 3	8	9	1
Ending balance	(29)	(27)	(43)
Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held	$ (17)	$ (9)	$ (20)