Basic and Diluted Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Feb. 28, 2014
Basic and Diluted Net Income (Loss) per Share
Net loss from continuing operations	$ (64,678)	$ (155,713)	$ (148,592)	$ (205,890)
Net income from discontinued operations	95,517	3,652	105,108	3,202
Net income (loss)	$ 30,839	$ (152,061)	$ (43,484)	$ (202,688)
Weighted average common shares outstanding (in shares)	34,492	35,311	34,339	34,948
Net loss per share:
Loss from continuing operations (in dollars per share)	$ (1.88)	$ (4.41)	$ (4.33)	$ (5.89)
Income (loss) from discontinued operations (in dollars per share)	2.77	0.10	3.06	0.09
Basic and diluted net loss per share (in dollars per share)	$ 0.89	$ (4.31)	$ (1.27)	$ (5.80)
Anti-dilutive securities (in shares)			18,328	18,022
Options to purchase shares of common stock
Net loss per share:
Anti-dilutive securities (in shares)			3,700	3,389
Shares of common stock issuable upon the vesting of RSUs
Net loss per share:
Anti-dilutive securities (in shares)			1,135	1,140
Warrants
Net loss per share:
Anti-dilutive securities (in shares)			1,008	1,008
2022 Convertible Notes | Convertible Debt Securities
Net loss per share:
Anti-dilutive securities (in shares)			11,695	11,695
2019 Convertible Notes | Convertible Debt Securities
Net loss per share:
Anti-dilutive securities (in shares)			790	790
Convertible Debt | 2022 Convertible Notes
Basic and Diluted Net Income (Loss) per Share
Interest rate	3.25%	3.25%	3.25%	3.25%
Convertible Debt | 2019 Convertible Notes
Basic and Diluted Net Income (Loss) per Share
Interest rate	2.50%		2.50%		2.50%