Variable Interest Entities ("VIE's") (Consolidated Variable Interest Entity Settlement Payments and Mark-to-Market Adjustments) (Details) - Derivative Instruments Not Designated and Not Qualifying as Hedging Instruments [Member] - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Consolidated Variable Interest Entity Settlement Payments And Mark To Market Adjustments [Line Items]
Gains (losses) for consolidated variable interest entities	[1]		$ (1)		$ 5
Credit default swaps [Member]
Consolidated Variable Interest Entity Settlement Payments And Mark To Market Adjustments [Line Items]
Gains (losses) for consolidated variable interest entities			(1)		5
Contingent forwards [Member]
Consolidated Variable Interest Entity Settlement Payments And Mark To Market Adjustments [Line Items]
Gains (losses) for consolidated variable interest entities

[1] Reported in realized gain (loss) on our Consolidated Statements of Comprehensive Income (Loss).