Basic and Diluted Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands		3 Months Ended		6 Months Ended
	Aug. 17, 2015	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 07, 2017	May 10, 2017	Feb. 14, 2014
Components of basic and diluted net income (loss) per share
Net loss		$ (14,066,000)	$ (596,000)	$ (50,626,000)	$ (8,123,000)
Weighted average shares outstanding used to compute net loss per share:
Basic (in shares)		35,145	34,223	34,764	34,481
Diluted (in shares)		35,145	34,223	34,764	34,481
Net income (loss) per share:
Basic (in usd per share)		$ (0.40)	$ (0.02)	$ (1.46)	$ (0.24)
Diluted (in usd per share)		$ (0.40)	$ (0.02)	$ (1.46)	$ (0.24)
Anti-dilutive securities (in shares)		18,573	17,769	18,737	18,432
Options to purchase shares of common stock
Net income (loss) per share:
Anti-dilutive securities (in shares)		2,904	2,525	2,939	2,694
Shares of common stock issuable upon the vesting of RSUs
Net income (loss) per share:
Anti-dilutive securities (in shares)		944	480	1,073	974
Warrants
Net income (loss) per share:
Anti-dilutive securities (in shares)		1,515	7,382	1,515	7,382
2019 Convertible Notes
Basic and Diluted Net Income (Loss) per Share
Interest rate		2.25%		2.25%
Debt, face amount								$ 200,000,000
2019 Convertible Notes | Convertible Notes
Net income (loss) per share:
Anti-dilutive securities (in shares)		1,515	7,382	1,515	7,382
2022 Convertible Notes
Basic and Diluted Net Income (Loss) per Share
Interest rate		3.25%		3.25%
Debt term (in years)				5 years
Debt, face amount						$ 20,000,000	$ 300,000,000
2022 Convertible Notes | Convertible Notes
Net income (loss) per share:
Anti-dilutive securities (in shares)		11,695	0	11,695	0
2015 Term Loan Facility
Basic and Diluted Net Income (Loss) per Share
Debt term (in years)	6 years			6 years
Debt, face amount	$ 350,000,000	$ 350,000,000.0		$ 350,000,000.0