Summary of Significant Accounting Policies - Basic and Diluted Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands		3 Months Ended								12 Months Ended
	Aug. 17, 2015	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 14, 2014
Debt Instrument [Line Items]
Net income (loss) - basic		$ (10,557,000)	$ 16,196,000	$ (596,000)	$ (7,527,000)	$ 7,201,000	$ (20,584,000)	$ 33,258,000	$ 12,904,000	$ (2,483,000)	$ 32,779,000	$ 135,817,000
Dilutive effect of convertible 2.5% notes										0	0	1,654,000
Net income (loss) - diluted										$ (2,483,000)	$ 32,779,000	$ 137,471,000
Weighted average common shares outstanding (in shares)										34,346	31,471	22,416
Effect of dilutive securities:
Warrants (in shares)										0	2,466	0
Stock options and RSUs (in shares)										0	1,371	520
Convertible 2.5% notes (in shares)										0	0	2,289
Shares used in calculating dilutive net income (loss) per share (in shares)										34,346	35,308	25,225
Net income (loss) per share:
Basic (USD per share)		$ (0.31)	$ 0.47	$ (0.02)	$ (0.22)	$ 0.21	$ (0.62)	$ 1.09	$ 0.47	$ (0.07)	$ 1.04	$ 6.06
Diluted (USD per share)		$ (0.31)	$ 0.43	$ (0.02)	$ (0.22)	$ 0.20	$ (0.62)	$ 0.82	$ 0.39	$ (0.07)	$ 0.93	$ 5.45
2.5% Convertible Notes
Debt Instrument [Line Items]
Principal amount of debt at time of issuance		$ 200,000,000.0								$ 200,000,000.0			$ 200,000,000
Interest rate (percent)		2.50%								2.50%
2015 Term Loan Facility
Debt Instrument [Line Items]
Principal amount of debt at time of issuance	$ 350,000,000	$ 350,000,000.0								$ 350,000,000.0
Debt term (years)	6 years									6 years		5 years