Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Accrued expenses	$ 74	$ 39
Interest rate hedge contracts	5	9
Share-based compensation	43	40
Net operating loss and credit carry-forwards	131	131
Deferred revenue	11	17
Other	14	7
Subtotal	278	243
Valuation allowance	(101)	(103)
Total deferred tax assets	177	140
Capitalized software development costs	(129)	(117)
Intangible assets	(437)	(455)
Property and equipment	(66)	(49)
Capitalized commissions	(80)	0
Investment in joint ventures	(78)	0
Other	(112)	(48)
Total deferred tax liabilities	(902)	(669)
Total	$ (725)	$ (529)