Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net income (loss) attributable to common stockholders, basic	$ 15,033	$ (4,584)	$ 34,065	$ (23,061)
Add: Interest expense on convertible subordinated notes due 2023, net of tax	1,429	0	0	0
Net income (loss) attributable to common stockholders, diluted	$ 16,462	$ (4,584)	$ 34,065	$ (23,061)
Denominator:
Weighted-average shares used to compute basic net income (loss) per share	109,282,000	115,787,000	111,128,000	115,381,000
Weighted-average shares used to compute diluted net income (loss) per share	121,993,000	115,787,000	111,583,000	115,381,000
Net income (loss) per share
Basic (in dollars per share)	$ 0.14	$ (0.04)	$ 0.31	$ (0.20)
Diluted (in dollars per share)	$ 0.13	$ (0.04)	$ 0.31	$ (0.20)
Anti-dilutive securities (in shares)	3,881,000	19,463,000	16,851,000	20,101,000
Stock options
Net income (loss) per share
Anti-dilutive securities (in shares)	2,600,000	4,000,000	3,000,000	4,200,000
RSUs
Net income (loss) per share
Anti-dilutive securities (in shares)	49,000	300,000	100,000	400,000
Unvested RSAs
Net income (loss) per share
Anti-dilutive securities (in shares)	100,000	800,000	200,000	1,000,000
Equity incentive plans and ESPP
Denominator:
Dilutive effect of options and awards granted under equity incentive plan and employee stock purchase plan	313,000	0	455,000	0
Net income (loss) per share
Anti-dilutive securities (in shares)	3,881,000	6,559,000	4,216,000	7,197,000
Convertible subordinated notes
Denominator:
Dilutive effect of convertible subordinated notes due 2023	12,398,000	0	0	0
Net income (loss) per share
Anti-dilutive securities (in shares)	0	12,904,000	12,635,000	12,904,000