Consolidated Statements of Comprehensive Loss - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues, net	$ 74,991,000	$ 99,878,000	$ 108,530,000
Cost of revenues	32,520,000	35,203,000	40,137,000
Gross profit	42,471,000	64,675,000	68,393,000
Operating expenses
Sales and marketing	26,936,000	32,889,000	45,132,000
Research and development	26,564,000	27,841,000	33,318,000
General and administrative	16,444,000	19,890,000	22,391,000
Impairment of goodwill	2,797,000	0	0
Total operating expenses	72,741,000	80,620,000	100,841,000
Loss from operations	(30,270,000)	(15,945,000)	(32,448,000)
Interest expense, net	(137,000)	(129,000)	(118,000)
Other (expenses) income, net	(77,000)	998,000	222,000
Loss before provision for income taxes	(30,484,000)	(15,076,000)	(32,344,000)
Provision for income taxes	(1,007,000)	(1,404,000)	(1,005,000)
Net loss	(31,491,000)	(16,480,000)	(33,349,000)
Foreign currency translation adjustments	2,205,000	(1,110,000)	(1,030,000)
Comprehensive loss	$ (29,286,000)	$ (17,590,000)	$ (34,379,000)
Net loss per share available to common stockholders, basic and diluted	$ (5.59)	$ (3.01)	$ (6.38)
Weighted-average shares used to compute net loss per share available to common stockholders, basic and diluted	5,638	5,474	5,225
Amortization of intangible assets is allocated as follows (Note 6):
Amortization of intangible assets	$ 2,850,000	$ 3,080,000	$ 3,134,000
Cost of Revenues [Member]
Stock-based compensation is allocated as follows (Note 11):
Allocation of stock-based compensation	822,000	1,314,000	1,171,000
Amortization of intangible assets is allocated as follows (Note 6):
Amortization of intangible assets	971,000	1,027,000	1,033,000
Restructuring related expenses are allocated as follows (Note 4):
Restructuring related expenses	0	184,000	173,000
Sales and Marketing [Member]
Stock-based compensation is allocated as follows (Note 11):
Allocation of stock-based compensation	827,000	1,281,000	2,537,000
Amortization of intangible assets is allocated as follows (Note 6):
Amortization of intangible assets	877,000	934,000	921,000
Restructuring related expenses are allocated as follows (Note 4):
Restructuring related expenses	0	348,000	718,000
Research and Development [Member]
Stock-based compensation is allocated as follows (Note 11):
Allocation of stock-based compensation	1,996,000	4,989,000	7,518,000
Amortization of intangible assets is allocated as follows (Note 6):
Amortization of intangible assets	969,000	1,027,000	1,034,000
Restructuring related expenses are allocated as follows (Note 4):
Restructuring related expenses	0	44,000	53,000
General and Administrative [Member]
Stock-based compensation is allocated as follows (Note 11):
Allocation of stock-based compensation	1,059,000	2,711,000	4,393,000
Amortization of intangible assets is allocated as follows (Note 6):
Amortization of intangible assets	33,000	92,000	146,000
Restructuring related expenses are allocated as follows (Note 4):
Restructuring related expenses	$ 0	$ 20,000	$ 270,000