Income Taxes - Additional Information (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes Other Information [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		35.00%	35.00%	35.00%
Deferred Tax Assets, Valuation Allowance		$ 79	$ 98
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		67
Unrecognized Tax Benefits, Interest on Income Taxes Accrued		8	20
Unrecognized Tax Benefits, Interest on Income Taxes Expense		4	3
Decrease in Unrecognized Tax Benefits is Reasonably Possible		17
Effective Income Tax Rate Reconciliation, Tax Credit, Amount	[1]	(69)	(65)	$ (53)
Investments [Member]
Income Taxes Other Information [Line Items]
Effective Income Tax Rate Reconciliation, Tax Credit, Amount		$ (8)	$ (21)	$ 0

[1] Excludes tax credits of $8 million, $21 million, and $0 for the years ended December 31, 2015, 2014, and 2013, respectively, which were recognized as a reduction to the related investment asset.