Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Income Taxes Other Information [Line Items]
Income Tax Expense (Benefit)	$ 187	$ 67	$ 579	$ 364
Effective Income Tax Rate Reconciliation, Percent	26.00%	10.00%	29.00%	21.00%
discrete income tax benefit	$ (35)	$ (130)
Unrecognized Tax Benefits	152		$ 152		$ 210
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 65		$ 65