Basic and Diluted Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Components of basic and diluted net income (loss) per share
Net (loss) income		$ (152,061,000)	$ 16,196,000	$ (202,688,000)	$ 8,074,000
Weighted average common shares outstanding		35,311	34,171	34,948	34,377
Effect of dilutive securities:
Stock options and RSUs (in shares)		0	558	0	387
2019 Convertible Notes (in shares)		0	7,382	0	0
Shares used in calculating dilutive net (loss) income per share		35,311	42,111	34,948	34,764
Net (loss) income per share:
Basic (in usd per share)		$ (4.31)	$ 0.47	$ (5.80)	$ 0.23
Diluted (in usd per share)		$ (4.31)	$ 0.43	$ (5.80)	$ 0.23
Anti-dilutive securities (in shares)		17,570	9,849	18,022	18,196
Options to purchase shares of common stock
Net (loss) income per share:
Anti-dilutive securities (in shares)		3,145	2,218	3,389	2,778
Shares of common stock issuable upon the vesting of RSUs
Net (loss) income per share:
Anti-dilutive securities (in shares)		932	249	1,140	654
Warrants
Net (loss) income per share:
Anti-dilutive securities (in shares)		1,008	7,382	1,008	7,382
2019 Convertible Notes | Convertible Debt Securities
Net (loss) income per share:
Anti-dilutive securities (in shares)		790	0	790	7,382
2022 Convertible Notes
Basic and Diluted Net Income (Loss) per Share
Debt term				5 years
2022 Convertible Notes | Convertible Debt Securities
Net (loss) income 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	6 years
Convertible Debt
Basic and Diluted Net Income (Loss) per Share
Interest rate		2.50%		2.50%
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%
Line of Credit | 2015 Term Loan Facility
Basic and Diluted Net Income (Loss) per Share
Debt term				6 years
Debt amount		$ 350,000,000.0		$ 350,000,000.0