Consolidated Statements of Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues, net	$ 58,631	$ 74,991	$ 99,878
Cost of revenues	27,154	32,520	35,203
Gross profit	31,477	42,471	64,675
Operating expenses
Sales and marketing	23,425	26,936	32,889
Research and development	22,450	26,564	27,841
General and administrative	13,113	16,444	19,890
Impairment of goodwill	14,740	2,797
Total operating expenses	73,728	72,741	80,620
Loss from operations	(42,251)	(30,270)	(15,945)
Other income, net	1,593	(214)	869
Loss before provision for income taxes	(40,658)	(30,484)	(15,076)
Provision for income taxes	(586)	(1,007)	(1,404)
Net loss	(41,244)	(31,491)	(16,480)
Foreign currency translation adjustments	(356)	2,205	(1,110)
Comprehensive loss	$ (41,600)	$ (29,286)	$ (17,590)
Net loss per share available to common stockholders, basic and diluted (in dollars per share)	$ (7.13)	$ (5.59)	$ (3.01)
Weighted-average shares used to compute net loss per share available to common stockholders, basic and diluted (in shares)	5,783	5,638	5,474
Amortization of intangible assets	$ 2,537	$ 2,850	$ 3,080
Cost of Sales [Member]
Operating expenses
Allocated Share-based Compensation Expense	739	822	1,314
Amortization of intangible assets	938	971	1,027
Restructuring Costs	176		184
Selling and Marketing Expense [Member]
Operating expenses
Allocated Share-based Compensation Expense	957	827	1,281
Amortization of intangible assets	658	877	934
Restructuring Costs	827		348
Research and Development Expense [Member]
Operating expenses
Allocated Share-based Compensation Expense	1,398	1,996	4,989
Amortization of intangible assets	938	969	1,027
Restructuring Costs	115		44
General and Administrative Expense [Member]
Operating expenses
Allocated Share-based Compensation Expense	877	1,059	2,711
Amortization of intangible assets	3	33	92
Restructuring Costs	$ 158		$ 20