Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenue	$ 1,015,021	$ 993,260	$ 992,065
Cost of revenue	516,448	486,804	483,900
Gross profit	498,573	506,456	508,165
Operating expenses:
Research and development	159,941	157,358	151,395
Sales and marketing	183,498	173,697	169,042
General and administrative	76,576	92,953	85,618
Amortization of identified intangibles	45,291	47,339	39,560
Restructuring and other	13,581	7,562	6,731
Total operating expenses	478,887	478,909	452,346
Income from operations	19,686	27,547	55,819
Interest expense	(20,169)	(19,505)	(17,716)
Interest income and other income (expense), net	1,604	4,088	545
Total income before income taxes	1,121	12,130	38,648
Provision for (benefit from) income taxes	2,092	27,475	(6,301)
Net income (loss)	$ (971)	$ (15,345)	$ 44,949
Net income (loss) per basic common share (in USD per share)	$ (0.02)	$ (0.33)	$ 0.96
Net income (loss) per diluted common share (in USD per share)	$ (0.02)	$ (0.33)	$ 0.94
Shares used in basic per-share calculation (in shares)	44,429	46,281	46,900
Shares used in diluted per-share calculation (in shares)	44,429	46,281	47,797