CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Revenues	$ 89,545	$ 74,493	[1]	$ 176,311	$ 147,072	[1]
Costs and expenses:
Cost of revenues	47,769	30,021		88,222	59,233
Sales and marketing	20,530	21,617		44,360	45,454
Research and development	12,122	12,774		24,748	25,894
General and administrative	11,528	11,803		22,920	23,696
Change in fair value of escrowed shares and contingent consideration, net		3,900		7,350	1,315
Total costs and expenses	91,949	80,115		187,600	155,592
Loss from operations	(2,404)	(5,622)		(11,289)	(8,520)
Interest expense	(3,326)			(6,634)
Other income (expense), net	1,270	134		2,208	261
Loss before income taxes	(4,460)	(5,488)		(15,715)	(8,259)
Provision for income taxes	200	270		302	173
Net loss	$ (4,660)	$ (5,758)		$ (16,017)	$ (8,432)
Net loss per share, basic and diluted	$ (0.05)	$ (0.06)		$ (0.17)	$ (0.10)
Weighted-average number of common shares used in computing net loss per share, basic and diluted	93,643	88,985		93,180	88,242

[1] As noted above, prior period amounts have not been adjusted under the modified retrospective method.