Summary of Significant Accounting Policies - Basic and Diluted Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Basis of Presentation and Summary of Significant Accounting Policies
Net income (loss) - basic	$ 7,201	$ (20,584)	$ 33,258	$ 12,904	$ 143,008	$ 1,458	$ (1,547)	$ (7,102)	$ 32,779	$ 135,817	$ (9,602)
Dilutive effect of convertible 2.5% notes										1,654
Net income (loss) - diluted									$ 32,779	$ 137,471	$ (9,602)
Weighted average common shares outstanding									31,471	22,416	21,703
Effect of dilutive securities:
Warrants (in shares)									2,466
Stock options and RSUs (in shares)									1,371	520
Convertible 2.5% notes (in shares)										2,289
Shares used in calculating dilutive net income (loss) per share (in shares)									35,308	25,225	21,703
Net income (loss) per share:
Basic	$ 0.21	$ (0.62)	$ 1.09	$ 0.47	$ 5.98	$ 0.07	$ (0.07)	$ (0.33)	$ 1.04	$ 6.06	$ (0.44)
Diluted	$ 0.20	$ (0.62)	$ 0.82	$ 0.39	$ 4.67	$ 0.07	$ (0.07)	$ (0.33)	$ 0.93	$ 5.45	$ (0.44)
Anti-dilutive securities excluded from the computation of diluted net income (loss) per share
Anti-dilutive securities (in shares)									9,168	10,412	3,285
Employee and Non Employee Stock Option
Anti-dilutive securities excluded from the computation of diluted net income (loss) per share
Anti-dilutive securities (in shares)									1,619	2,708	2,820
Employee and Non Employee Restricted Stock Units
Anti-dilutive securities excluded from the computation of diluted net income (loss) per share
Anti-dilutive securities (in shares)									167	322	465
Warrants
Anti-dilutive securities excluded from the computation of diluted net income (loss) per share
Anti-dilutive securities (in shares)										7,382
Convertible 2.5% notes
Anti-dilutive securities excluded from the computation of diluted net income (loss) per share
Anti-dilutive securities (in shares)									7,382