Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Revenue	$ 248,484	$ 125,295	$ 83,830
Expenses:
Cost of revenue	58,495	20,754	15,358
Sales and marketing	83,333	43,203	25,811
Technology and development	42,055	22,718	18,615
General and administrative	70,199	57,398	27,926
Total expenses	254,082	144,073	87,710
Loss from operations	(5,598)	(18,778)	(3,880)
Other (income) expense
Interest (income) expense, net	(59)	110	273
Change in fair value of preferred stock warrant liabilities	0	732	4,121
Foreign exchange (gain) loss, net	(1,400)	(1,119)	728
Total other (income) expense, net	(1,459)	(277)	5,122
Loss before income taxes	(4,139)	(18,501)	(9,002)
Provision (benefit) for income taxes	(4,561)	172	247
Net income (loss)	422	(18,673)	(9,249)
Cumulative preferred stock dividends	0	(1,116)	(4,244)
Net income (loss) attributable to common stockholders	$ 422	$ (19,789)	$ (13,493)
Net income (loss) per share attributable to common stockholders:
Basic (usd per share)	$ 0.01	$ (0.70)	$ (1.17)
Diluted (usd per share)	$ 0.01	$ (0.70)	$ (1.17)
Net income (loss) per share attributable to common stockholders:
Basic (in shares)	39,663	28,217	11,488
Diluted (in shares)	44,495	28,217	11,488