Income Taxes - Components of Deferred Tax Assets and Deferred Tax Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Provision for accrued expenses	$ 87	$ 44
Deferred loyalty rewards	166	131
Net operating loss and tax credit carryforwards	123	122
Stock-based compensation	67	52
Property and equipment	55	0
Other	68	52
Total deferred tax assets	566	401
Less valuation allowance	(80)	(76)
Net deferred tax assets	486	325
Deferred tax liabilities:
Goodwill and intangible assets	(486)	(499)
Property and equipment	0	(131)
Other	0	(6)
Total deferred tax liabilities	(486)	(636)
Net deferred tax liability	$ 0	$ (311)