Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 328	$ 341	$ 315
Capitalized software [member]
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 95	$ 94	$ 79