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Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Nov. 02, 2015	Dec. 10, 2013
Earnings Per Share, Basic and Diluted [Abstract]
Net loss	$ (66,837)	$ (13,001)	$ (114,507)	$ (24,215)
Shares used in computing basic and diluted net loss per share (in shares)	82,072	67,615	79,368	67,441
Basic and diluted net loss per share (in dollars per share)	$ (0.81)	$ (0.19)	$ (1.44)	$ (0.36)
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Outstanding securities used in calculations (in shares)	2,193	2,220	1,623	2,206
Convertible notes	$ 172,352		$ 172,352		$ 167,748
Potential Dilutive Effect of Securities [Abstract]
Conversion of the Notes (in shares)	14,767	3,588	14,767	3,588
Convertible Debt \| 2.25% Convertible Senior Notes
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Convertible notes	$ 75,900		$ 75,900				$ 86,300
Stated interest rate	2.25%		2.25%
Convertible Debt \| 3.25% Convertible Senior Notes
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Convertible notes	$ 100,800		$ 100,800			$ 125,000
Stated interest rate	3.25%		3.25%
Common stock options
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Outstanding securities used in calculations (in shares)	1,620	1,812	1,193	1,812
Restricted stock awards
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Outstanding securities used in calculations (in shares)	135	139	131	137
Restricted stock units
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Outstanding securities used in calculations (in shares)	438	269	299	257