Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net loss	$ (19,634)	$ (11,286)	$ (10,824)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	10,207	7,742	5,976
Loss on disposal of assets	15	74
Deferred income taxes	(47)	(138)	(431)
Accretion of interest on debt	493		130
Non-cash interest expense on line of credit and term loan		67	11
Non-cash investment income	(204)
Provision for doubtful accounts and sales return reserve	637	387	366
Stock-based compensation	9,218	3,056	1,488
Change in fair value of contingent consideration obligation	(1,020)
Increase (decrease) in operating assets and liabilities:
Accounts receivable	(13,067)	(2,295)	(4,813)
Prepaid expenses	(551)	(348)	(656)
Other assets	(785)	(1,096)	(408)
Accounts payable	(90)	(423)	866
Accrued payroll and employee related liabilities	3,596	1,312	1,181
Accrued expenses	(132)	539	(171)
Deferred revenue	16,378	11,982	11,623
Other liabilities	(151)	(70)	113
Net cash provided by operating activities	4,863	9,503	4,451
Cash flows from investing activities:
Capital expenditures	(1,667)	(970)	(2,502)
Proceeds from sale leaseback transaction	794
Payments for acquisition of business, net of acquired cash	(21,235)	(2,306)
Additions to capitalized software development costs	(6,160)	(5,494)	(4,902)
Change in restricted cash	(294)
Purchase of short-term investments	(60,764)
Maturities of short-term investments	18,060
Purchase of intangibles		(250)
Net cash used in investing activities	(71,266)	(9,020)	(7,404)
Cash flows from financing activities:
Proceeds from line of credit		9,500	12,000
Payments on line of credit		(19,500)	(5,000)
Payments of issuance costs relating to line of credit and term loan	(3,834)	(19)	(59)
Principal payments on capital leases		(58)	(101)
Proceeds from public offering, net of underwriters discounts and commissions	10,444	69,750
Payments of public offering costs	(872)	(1,960)	(1,391)
Payments on notes payable		(2,018)	(1,779)
(Payments) proceeds from term loan		(5,000)	5,000
Proceeds from issuance of convertible notes	115,000
Purchase of convertible note capped call hedge	(12,922)
Payments of contingent consideration obligation	(3,750)
Proceeds from employee stock purchase plan	1,540
Proceeds from warrant exercises		25
Proceeds from option exercises	2,869	750	49
Repurchase of common stock			(1,500)
Net cash provided by financing activities	108,475	51,470	7,219
Effect of exchange rates on cash and cash equivalents	(83)	234	(100)
Net increase in cash and cash equivalents	41,989	52,187	4,166
Cash and cash equivalents—beginning of year	60,765	8,578	4,412
Cash and cash equivalents—end of year	102,754	60,765	8,578
Supplemental disclosures of cash flow information:
Interest		495	369
Taxes, net of (refunds)	28	(117)	124
Supplemental disclosure of non-cash activities
Capitalized assets included in accounts payable and accrued expenses	73	104	63
Deferred offering costs in accounts payable and accrued expenses		298	1,175
Stock-based compensation capitalized for software development	81	$ 45	$ 34
Debt issuance costs included in accounts payable and accrued expenses	$ 84