Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net income (loss) attributable to common stockholders, basic	$ 14,597	$ (7,810)	$ 19,032	$ (18,477)
Add: Interest expense on convertible subordinated notes due 2013, net of tax	1,457	0	0	0
Net income (loss) attributable to common stockholders, diluted	$ 16,054	$ (7,810)	$ 19,032	$ (18,477)
Denominator:
Weighted-average shares used to compute basic net income (loss) per share	111,359	115,329	112,005	115,096
Weighted-average shares used to compute diluted net income (loss) per share	124,316	115,329	112,531	115,096
Net income (loss) per share
Basic (in dollars per share)	$ 0.13	$ (0.07)	$ 0.17	$ (0.16)
Diluted (in dollars per share)	$ 0.13	$ (0.07)	$ 0.17	$ (0.16)
Anti-dilutive securities (in shares)	4,276	19,856	17,136	20,194
Stock options
Net income (loss) per share
Anti-dilutive securities (in shares)	2,900	4,200	3,200	4,400
RSUs
Net income (loss) per share
Anti-dilutive securities (in shares)	100	400	100	500
Unvested RSAs
Net income (loss) per share
Anti-dilutive securities (in shares)	100	1,100	300	1,200
Equity incentive plans and ESPP
Denominator:
Dilutive effect of options and awards granted under equity incentive plan and employee stock purchase plan	355	0	526	0
Net income (loss) per share
Anti-dilutive securities (in shares)	4,276	7,178	4,383	7,516
Convertible subordinated notes
Denominator:
Dilutive effect of convertible subordinated notes due 2023	12,602	0	0	0
Net income (loss) per share
Anti-dilutive securities (in shares)	0	12,678	12,753	12,678