Consolidated Statements of Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Revenues	$ 277,507	$ 259,838	$ 206,649
Costs and operating expenses:
Cost of revenue (exclusive of depreciation and amortization presented separately below; includes related party expenses of $0, $0, and $405 for 2016, 2015, and 2014, respectively)	25,167	23,657	17,513
Sales and marketing (includes related party expenses of $13,910, $20,852, and $19,443, for the years ended December 31, 2016, 2015, and 2014, respectively)	154,406	151,002	128,569
Technology and development	53,580	48,021	36,563
General and administrative	59,908	83,494	58,296
Depreciation and amortization	23,345	17,646	13,213
Total costs and operating expenses	316,406	323,820	254,154
Loss from operations	(38,899)	(63,982)	(47,505)
Interest income	376	107	59
Interest expense	(2,530)	(443)	(380)
Other income	0	13	37
Loss before provision for income taxes	(41,053)	(64,305)	(47,789)
Provision for income taxes	655	606	640
Net loss	$ (41,708)	$ (64,911)	$ (48,429)
Net loss per share, basic and diluted (in dollars per share)	$ (0.49)	$ (0.79)	$ (0.68)
Weighted average common shares outstanding, basic and diluted	84,483	81,914	70,837
Other comprehensive loss:
Comprehensive loss	$ (41,708)	$ (64,911)	$ (48,429)