Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Accrued expenses	$ 49	$ 37
Interest rate hedge contracts	20	28
Share-based compensation	51	46
Net operating loss and credit carry-forwards	102	123
Deferred revenue	49	47
Other	12	28
Subtotal	283	309
Valuation allowance	(35)	(42)
Total deferred tax assets	248	267
Capitalized software development costs	(142)	(127)
Intangible assets	(700)	(737)
Property and equipment	(68)	(42)
Other	(42)	(35)
Total deferred tax liabilities	(952)	(941)
Total	$ (704)	$ (674)