Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Revenue	$ 278,221	$ 248,484	$ 125,295
Expenses:
Cost of revenue	73,247	58,495	20,754
Sales and marketing	83,328	83,333	43,203
Technology and development	51,184	42,055	22,718
General and administrative	68,570	70,199	57,398
Restructuring and other exit costs	3,316	0	0
Impairment of intangible assets	23,473	0	0
Total expenses	303,118	254,082	144,073
Loss from operations	(24,897)	(5,598)	(18,778)
Other (income) expense:
Interest (income) expense, net	(491)	(59)	110
Other income	554	0	0
Change in fair value of preferred stock warrant liabilities	0	0	732
Foreign exchange gain, net	(939)	(1,400)	(1,119)
Total other (income) expense, net	(1,984)	(1,459)	(277)
Loss before income taxes	(22,913)	(4,139)	(18,501)
Provision (benefit) for income taxes	(4,860)	(4,561)	172
Net income (loss)	(18,053)	422	(18,673)
Cumulative preferred stock dividends	0	0	(1,116)
Net income (loss) attributable to common stockholders	$ (18,053)	$ 422	$ (19,789)
Net income (loss) per share:
Basic (usd per share)	$ (0.39)	$ 0.01	$ (0.70)
Diluted (usd per share)	$ (0.39)	$ 0.01	$ (0.70)
Net income (loss) per share:
Basic (in shares)	46,655	39,663	28,217
Diluted (in shares)	46,655	44,495	28,217