Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net loss	$ (47,515)	$ (19,634)	$ (11,286)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	13,693	10,207	7,742
Amortization of deferred commissions	5,472	5,947	5,264
Loss on disposal of assets	112	15	74
Deferred income taxes	125	(47)	(138)
Accretion of interest on debt	4,616	493
Non-cash interest expense on line of credit and term loan			67
Non-cash investment income	(498)	(204)
Provision for doubtful accounts and sales return reserve	252	637	387
Stock-based compensation	25,589	9,218	3,056
Change in fair value of contingent consideration obligation	(250)	(1,020)
Increase (decrease) in operating assets and liabilities:
Accounts receivable	(2,623)	(13,067)	(2,295)
Prepaid expenses	(1,952)	(551)	(348)
Deferred costs	(8,285)	(89)	(6,529)
Other assets	(4,014)	(6,643)	169
Accounts payable	(1,263)	(90)	(423)
Accrued payroll and employee related liabilities	4,686	3,596	1,312
Accrued expenses	298	(132)	539
Deferred revenue	13,164	16,378	11,982
Other liabilities	1,688	(151)	(70)
Net cash provided by operating activities	3,295	4,863	9,503
Cash flows from investing activities:
Capital expenditures	(1,721)	(1,667)	(970)
Proceeds from sale leaseback transaction		794
Payments for acquisition of business, net of acquired cash	(35,857)	(21,235)	(2,306)
Additions to capitalized software development costs	(8,499)	(6,160)	(5,494)
Purchase of short-term investments	(87,204)	(60,764)
Maturities of short-term investments	85,069	18,060
Purchase of intangibles	(201)		(250)
Net cash used in investing activities	(48,413)	(70,972)	(9,020)
Cash flows from financing activities:
Proceeds from line of credit			9,500
Payments on line of credit			(19,500)
Payments of issuance costs relating to line of credit and term loan	(84)	(3,834)	(19)
Principal payments on capital leases	(99)		(58)
Proceeds from public offering, net of underwriters discounts and commissions		10,444	69,750
Payments of public offering costs	(276)	(872)	(1,960)
Payments on notes payable	(59)		(2,018)
(Payments) proceeds from term loan			(5,000)
Proceeds from issuance of convertible notes		115,000
Purchase of convertible note capped call hedge		(12,922)
Restricted stock units withheld to settle employee tax withholding liability	(7,925)
Payments of contingent consideration obligation	(431)	(3,750)
Proceeds from employee stock purchase plan	1,823	1,540
Proceeds from warrant exercises			25
Proceeds from option exercises	10,150	2,869	750
Net cash provided by financing activities	3,099	108,475	51,470
Effect of exchange rates on cash and cash equivalents	(964)	(80)	234
Net increase in cash and cash equivalents	(42,983)	42,286	52,187
Cash, cash equivalents and restricted cash—beginning of year	103,051	60,765	8,578
Cash, cash equivalents and restricted cash—end of year	60,068	103,051	60,765
Supplemental disclosures of cash flow information:
Interest	1,634		495
Taxes, net of (refunds)	113	28	(117)
Supplemental disclosure of non-cash activities
Capitalized assets included in accounts payable and accrued expenses	1,609	73	104
Deferred offering costs in accounts payable and accrued expenses	21		298
Stock-based compensation capitalized for software development	236	81	$ 45
Note payable issued for asset acquisition	52
Note payable issued for business acquisition	$ 383
Debt issuance costs included in accounts payable and accrued expenses		$ 84