CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Revenue	$ 236,634	$ 216,007	$ 186,672
Cost of revenue	82,178	71,791	62,800
Gross profit	154,456	144,216	123,872
Operating expenses:
Research and development	21,547	19,868	16,302
Sales and marketing	111,376	105,635	95,323
General and administrative	56,264	54,983	60,216
Total operating expenses	189,187	180,486	171,841
Loss from operations	(34,731)	(36,270)	(47,969)
Other expense, net:
Foreign currency transaction loss	(2,430)	(1,813)	(4,752)
Discount on prepayment of notes to stockholders	0	0	(4,825)
Interest expense	(4,425)	(941)	(2,205)
Total other expense, net	(6,855)	(2,754)	(11,782)
Loss before income taxes	(41,586)	(39,024)	(59,751)
Income tax expense (benefit)	74	192	(114)
Net loss	(41,660)	(39,216)	(59,637)
Accretion and adjustment of preferred stock to fair value	0
Accretion and adjustment of preferred stock to fair value	0	0	6,879
Net loss attributable to common stockholders	$ (41,660)	$ (39,216)	$ (52,758)
Net loss per share attributable to common stockholders:
Basic and diluted (in dollars per share)	$ (1.00)	$ (0.97)	$ (1.65)
Weighted average common shares outstanding:
Basic and diluted (in shares)	41,729,013	40,237,848	31,887,246