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Basic and Diluted Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Feb. 28, 2014
Basic and Diluted Net Income (Loss) per Share
Net loss from continuing operations	$ (25,817)	$ (14,252)	$ (83,916)	$ (50,178)
Net income (loss) from discontinued operations	5,736	186	9,592	(448)
Net loss	$ (20,081)	$ (14,066)	$ (74,324)	$ (50,626)
Weighted average common shares outstanding (in shares)	34,358	35,145	34,261	34,764
Net loss per share:
Loss from continuing operations (in dollars per share)	$ (0.75)	$ (0.41)	$ (2.45)	$ (1.44)
Income (loss) from discontinued operations (in dollars per share)	0.17	0.01	0.28	(0.01)
Basic and diluted net loss per share (in dollars per share)	$ (0.58)	$ (0.40)	$ (2.17)	$ (1.45)
Anti-dilutive securities (in shares)			18,801	18,737
Options to purchase shares of common stock
Net loss per share:
Anti-dilutive securities (in shares)			3,893	2,939
Shares of common stock issuable upon the vesting of RSUs
Net loss per share:
Anti-dilutive securities (in shares)			1,415	1,073
Warrants
Net loss per share:
Anti-dilutive securities (in shares)			1,008	1,515
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	1,515
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%