Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenue (Note 3)		$ 378	$ 372
Costs and expenses:
Cost of revenue	[1]	20	17
Selling and marketing	[2]	198	207
Technology and content	[2]	67	59
General and administrative	[2]	42	35
Depreciation		20	19
Amortization of intangible assets		8	8
Total costs and expenses:		355	345
Operating income		23	27
Other income (expense):
Interest expense		(3)	(3)
Interest income and other, net		1	1
Total other expense, net		(2)	(2)
Income before income taxes		21	25
Provision for income taxes		(16)	(12)
Net income		$ 5	$ 13
Earnings per share attributable to common stockholders (Note 4):
Basic		$ 0.04	$ 0.09
Diluted		$ 0.04	$ 0.09
Weighted average common shares outstanding (Note 4):
Basic		139,312	143,632
Diluted		140,322	144,717

[1] Excludes amortization as follows:

[2] Includes stock-based compensation expense as follows