Consolidated Statements of Comprehensive Loss (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Statement [Abstract]
Revenues	$ 50,497	$ 31,223	$ 94,427	$ 56,266
Costs and operating expenses:
Cost of revenue (exclusive of depreciation and amortization presented separately below; includes related party expenses of $634 for the three months ended June 30, 2013, and $405 and $1,162 for six months ended June 30, 2014 and 2013, respectively)	4,137	3,673	7,858	7,435
Sales and marketing (includes related party expenses of $7,169 and $6,244 for the three months ended June 30, 2014 and 2013 and $10,771 and $7,651 for six months ended June 30, 2014 and 2013, respectively)	33,292	15,626	61,059	29,409
Technology and development	8,513	5,618	15,843	11,422
General and administrative	16,439	6,629	27,955	12,942
Depreciation and amortization	2,972	2,868	6,086	5,934
Total costs and operating expenses	65,353	34,414	118,801	67,142
Loss from operations	(14,856)	(3,191)	(24,374)	(10,876)
Interest income	10	29	27	61
Interest expense	(131)	(510)	(301)	(1,751)
Other income	10	6	10	14
Loss before provision for income taxes	(14,967)	(3,666)	(24,638)	(12,552)
Provision for income taxes	67	136	317	273
Net loss	(15,034)	(3,802)	(24,955)	(12,825)
Net loss per share
Basic and diluted	$ (0.22)	$ (0.07)	$ (0.39)	$ (0.22)
Weighted average common shares outstanding, basic and diluted	67,784	58,313	63,962	57,231
Other comprehensive loss:
Comprehensive loss	$ (15,034)	$ (3,802)	$ (24,955)	$ (12,825)