Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Numerator:
Net income (loss), basic and diluted	$ 4,435	$ (10,667)
Denominator:
Weighted-average shares used to compute basic net income (loss) per share	112,482	114,658
Weighted-average shares used to compute diluted net income (loss) per share	113,178	114,658
Net income (loss) per share
Basic (in dollars per share)	$ 0.04	$ (0.09)
Diluted (in dollars per share)	$ 0.04	$ (0.09)
Anti-dilutive securities (in shares)	17,331	20,290
Stock options
Net income (loss) per share
Anti-dilutive securities (in shares)	3,300	4,500
RSUs
Net income (loss) per share
Anti-dilutive securities (in shares)	100	600
Unvested RSAs
Net income (loss) per share
Anti-dilutive securities (in shares)	400	1,200
Equity incentive plans and ESPP
Denominator:
Dilutive effect of options and awards	196
Net income (loss) per share
Anti-dilutive securities (in shares)	3,917	5,866
Unvested RSAs
Denominator:
Dilutive effect of options and awards	500
Net income (loss) per share
Anti-dilutive securities (in shares)	510	1,930
Convertible subordinated notes
Net income (loss) per share
Anti-dilutive securities (in shares)	12,904	12,494