Income Taxes - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Unrecognized tax benefits, affect the effective tax rate	$ 57	$ 61	$ 73
Accrual for payment of interest and penalties associated with uncertain tax positions	14	16
Decrease in accruals for payment of interest and penalties associated with uncertain tax positions	3
Deferred income taxes, net	2,923	$ 2,444
Minimum [Member] | State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Expected tax benefit to continuing operations	0
Maximum [Member] | State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Expected tax benefit to continuing operations	$ 20