Consolidated Statements of Operations - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenue	$ 125,300,000	$ 112,287,000	$ 78,479,000
Cost of revenue	60,359,000	52,834,000	37,633,000
Gross profit	64,941,000	59,453,000	40,846,000
Operating expenses:
Research and development	32,220,000	25,185,000	17,579,000
Sales and marketing	31,579,000	22,330,000	14,579,000
General and administrative	18,161,000	12,426,000	7,087,000
Total operating expenses	81,960,000	59,941,000	39,245,000
Income (loss) from operations	(17,019,000)	(488,000)	1,601,000
Interest income (expense) and other income (expense), net:
Interest expense	(908,000)	(1,633,000)	(1,208,000)
Interest income and other income (expense), net	508,000	616,000	673,000
Total interest income (expense) and other, net	(400,000)	(1,017,000)	(535,000)
Income (loss) before tax expense	(17,419,000)	(1,505,000)	1,066,000
Income tax benefit (expense)	97,000	(168,000)	(166,000)
Net income (loss)	(17,322,000)	(1,673,000)	900,000
Less: Accretion of preferred stock		(6,258,000)	(11,301,000)
Net income (loss) attributable to common stockholders	$ (17,322,000)	$ (7,931,000)	$ (10,401,000)
Net income (loss) per share attributable to common stockholders — basic and diluted	$ (0.84)	$ (0.74)	$ (2.67)
Weighted-average shares used to compute net income (loss) per shares attributable to common stockholders — basic and diluted	20,680	10,778	3,893