Basic and Diluted Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jun. 30, 2017	Feb. 28, 2014
Basic and Diluted Net Income (Loss) per Share
Net loss	$ (54,242)	$ (36,560)
Weighted average common shares outstanding (in shares)	34,162	34,378
Shares used in calculating dilutive net loss per share (in shares)	34,162	34,378
Net loss per share:
Basic and diluted (in usd per share)	$ (1.59)	$ (1.06)
Anti-dilutive securities (in shares)	18,665	17,945
Options to purchase shares of common stock
Net loss per share:
Anti-dilutive securities (in shares)	3,771	2,406
Shares of common stock issuable upon the vesting of RSUs
Net loss per share:
Anti-dilutive securities (in shares)	1,401	775
Warrants
Net loss per share:
Anti-dilutive securities (in shares)	1,008	7,382
2019 Convertible Notes | Convertible Debt Securities
Net loss per share:
Anti-dilutive securities (in shares)	790	7,382
2022 Convertible Notes | Convertible Debt Securities
Net loss per share:
Anti-dilutive securities (in shares)	11,695	0
Convertible Debt | 2019 Convertible Notes
Basic and Diluted Net Income (Loss) per Share
Interest rate	2.50%			2.50%
Convertible Debt | 2022 Convertible Notes
Basic and Diluted Net Income (Loss) per Share
Interest rate	3.25%		3.25%