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	$ 423,124	$ 339,651	$ 263,568
Cost of revenue	135,752	109,864	77,684
Gross profit	287,372	229,787	185,884
Operating expenses:
Sales and marketing	225,631	207,026	162,552
Research and development	46,977	40,991	30,618
General and administrative	70,956	49,877	41,802
Amortization of certain acquired intangible assets	150	600	828
Total operating expenses	343,714	298,494	235,800
Loss from operations	(56,342)	(68,707)	(49,916)
Other income (expense):
Interest income	1,702	894	720
Interest expense	(12,924)	(12,506)	(12,157)
Other, net	1,934	(4,016)	(2,691)
Other income (expense), net	(9,288)	(15,628)	(14,128)
Loss before income tax provision	(65,630)	(84,335)	(64,044)
Income tax provision	(1,207)	(1,181)	(855)
Net loss	$ (66,837)	$ (85,516)	$ (64,899)
Net loss per share — basic and diluted (usd per share)	$ (1.20)	$ (1.58)	$ (1.22)
Weighted average common shares outstanding, basic and diluted (in shares)	55,595	54,171	53,267