Summary of Significant Accounting Policies (Accounting Policies) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Accounting Change [Line Items]
Noncontrolling Interest Portion Of Accumulated Other Comprehensive Income And Other	$ 39	$ (2)	$ (40)	$ 95
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	6,110		6,110
Unamortized Debt Issuance Costs					$ 674
Investment in Unconsolidated VIEs [Member]
Accounting Change [Line Items]
Noncontrolling Interest Portion Of Accumulated Other Comprehensive Income And Other			123
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 6,316		$ 6,316		$ 787