CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Revenues	$ 185,279	$ 206,980	$ 204,724
Cost of revenues	63,742	61,834	78,669
Amortization of acquired intangible assets	1,453	1,736	1,733
Gross profit	120,084	143,410	124,322
Operating expenses:
Research and development	17,767	16,799	14,190
In-process research and development	274	527	0
Sales and marketing	70,856	77,179	76,960
General and administrative	34,867	43,381	47,949
Amortization of acquired intangible assets	2,400	2,974	3,009
Goodwill and intangible assets impairment	165,171	0	0
Restructuring expenses	1,188	706	9,665
Litigation settlement expenses	0	0	45,982
Total operating expenses	292,523	141,566	197,755
Operating (loss) income	(172,439)	1,844	(73,433)
Other income (expense):
Interest income	53	10	6
Interest expense	(12,589)	(13,616)	(3,959)
Other income (expense), net	6,980	(33)	(1,662)
Total other income (expense)	(5,556)	(13,639)	(5,615)
Loss before income taxes	(177,995)	(11,795)	(79,048)
Income tax provision	681	1,087	3,179
Net loss	$ (178,676)	$ (12,882)	$ (82,227)
Net loss per common share:
Net loss per basic share (in dollars per share)	$ (1.79)	$ (0.13)	$ (0.85)
Net loss per diluted share (in dollars per share)	$ (1.79)	$ (0.16)	$ (0.85)
Weighted-average shares used in computing net loss per share:
Shares used in calculating basic net loss per share (in shares)	99,574	97,347	96,235
Shares used in calculating diluted net loss per share (in shares)	99,574	97,735	96,235