Basis of Presentation and Principles of Consolidation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefits recorded	$ 23
Diluted shares outstanding (in shares)	170,246,947	168,368,444
Increase to cash provided by operating activities	$ 244	$ 255
Decrease to cash provided by financing activities	$ 192	(28)
Initial Listing Fees
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Listings estimated useful life	6 years
Additional Listing Fees
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Listings estimated useful life	4 years
Accounting Standards Update 2016-09, Excess Tax Benefit Component [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Diluted shares outstanding (in shares)	834,311
Impact on diluted EPS (in dollars per share)	$ 0.13
Increase to cash provided by operating activities		2
Decrease to cash provided by financing activities		$ 2