Income (Loss) Per Share - Commutation of Basic and Diluted Loss per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2016
Earnings Per Share Reconciliation [Abstract]
Net income (loss)	$ (131,918)	$ (14,271)	$ (40,560)	$ (222,337)	$ 35,439	$ (83,891)	$ 28,169	$ 61,092	$ (409,086)	$ 40,809	$ 39,427
Less: Undistributed income allocated to participating securities									0	438	556
Net income (loss) attributable to common stockholders									(409,086)	40,371	38,871
Plus: Net income effect of convertible securities									0	0	0
Numerator for diluted income (loss) per common share									$ (409,086)	$ 40,371	$ 38,871
Basic weighted-average common stock shares outstanding (in shares)									53,295	50,352	45,726
Plus: dilutive effects of common stock equivalents (in shares)									0	118	29
Diluted weighted-average common stock shares outstanding (in shares)									53,295	50,470	45,755
Basic (USD per share)	$ (2.47)	$ (0.27)	$ (0.76)	$ (4.18)	$ 0.68	$ (1.65)	$ 0.56	$ 1.23	$ (7.68)	$ 0.80	$ 0.85
Diluted (USD per share)	$ (2.47)	$ (0.27)	$ (0.76)	$ (4.18)	$ 0.68	$ (1.65)	$ 0.56	$ 1.14	$ (7.68)	$ 0.80	$ 0.85
5.00% Convertible Senior Notes due 2021
Earnings Per Share Reconciliation [Abstract]
Debt instrument, interest rate	5.00%								5.00%			5.00%
5.00% Convertible Senior Notes due 2021 | Convertible Debt
Earnings Per Share Reconciliation [Abstract]
Debt instrument, interest rate	5.00%								5.00%			5.00%
Restricted Stock Awards
Earnings Per Share Reconciliation [Abstract]
Antidilutive securities (in shares)									475	182	68
Stock Option Awards
Earnings Per Share Reconciliation [Abstract]
Antidilutive securities (in shares)									2,229	1,577	1,304
Common Stock
Earnings Per Share Reconciliation [Abstract]
Antidilutive securities (in shares)									2,704	5,122	6,389