Condensed Consolidated Statements of Equity (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Common Stock - Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Treasury Stock Restricted stock units	Treasury Stock Stock appreciation rights	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjustment Retained Earnings
Beginning Balance (in shares) at Dec. 31, 2018		37,318,942
Beginning Balance at Dec. 31, 2018	$ 765,253	$ 5	$ 451,427	$ 427,244	$ (1,656)	$ (111,767)
Beginning Balance (Accounting Standards Update 2016-02) at Dec. 31, 2018									$ (6,516)	$ (6,516)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of restricted stock units to common stock (net of shares of treasury stock purchased) (in shares)		283,339
Conversion of restricted stock units to common stock (net of shares of treasury stock purchased)	(2,760)					(2,760)
Settlement of stock appreciation rights in common stock (net of shares of treasury stock purchased) (in shares)		16,937
Settlement of stock appreciation rights in common stock (net of shares of treasury stock purchased)	(171)		(12)			(159)
Partial termination of capped call options (in shares)		(1,087)
Partial termination of capped call options	0		30			(30)
Convertible debt extinguishment impact (net of tax impact)	(152)		(152)
Termination of capped call options (in shares)							(138,012)	(9,888)
Stock compensation expense	1,353		1,353
Other comprehensive income (loss)	(362)				(362)
Net income (loss)	(43,404)			(43,404)
Ending Balance (in shares) at Mar. 31, 2019		37,618,131
Ending Balance at Mar. 31, 2019	713,241	$ 5	452,646	377,324	(2,018)	(114,716)
Beginning Balance (in shares) at Dec. 31, 2018		37,318,942
Beginning Balance at Dec. 31, 2018	765,253	$ 5	451,427	427,244	(1,656)	(111,767)
Beginning Balance (Accounting Standards Update 2016-02) at Dec. 31, 2018									$ (6,516)	$ (6,516)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(121,447)
Ending Balance (in shares) at Sep. 30, 2019		38,964,276
Ending Balance at Sep. 30, 2019	637,618	$ 5	446,435	299,281	(2,640)	(105,463)
Beginning Balance (in shares) at Mar. 31, 2019		37,618,131
Beginning Balance at Mar. 31, 2019	713,241	$ 5	452,646	377,324	(2,018)	(114,716)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of restricted stock units to common stock (net of shares of treasury stock purchased) (in shares)		58,759
Conversion of restricted stock units to common stock (net of shares of treasury stock purchased)	(518)					(518)
Settlement of stock appreciation rights in common stock (net of shares of treasury stock purchased) (in shares)		4,631
Settlement of stock appreciation rights in common stock (net of shares of treasury stock purchased)	(24)		(7)			(17)
Settlement of 2019 Convertible Senior Notes conversion premium (in shares)		1,902,781
Settlement of 2019 Convertible Senior Notes conversion premium	0		(18,779)			18,779
Termination of capped call options (in shares)		(625,558)					(805)	(2,274)
Termination of capped call options	0		8,952			(8,952)
Stock compensation expense	1,824		1,824
Other comprehensive income (loss)	395				395
Net income (loss)	(62,097)			(62,097)
Ending Balance (in shares) at Jun. 30, 2019		38,958,744
Ending Balance at Jun. 30, 2019	652,821	$ 5	444,636	315,227	(1,623)	(105,424)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of restricted stock units to common stock (net of shares of treasury stock purchased) (in shares)		3,557
Conversion of restricted stock units to common stock (net of shares of treasury stock purchased)	(39)					(39)
Settlement of stock appreciation rights in common stock (net of shares of treasury stock purchased) (in shares)		1,975
Settlement of stock appreciation rights in common stock (net of shares of treasury stock purchased)	(5)		(5)
Termination of capped call options (in shares)							(1,775)	(1,042)
Stock compensation expense	1,804		1,804
Other comprehensive income (loss)	(1,017)				(1,017)
Net income (loss)	(15,946)			(15,946)
Ending Balance (in shares) at Sep. 30, 2019		38,964,276
Ending Balance at Sep. 30, 2019	637,618	$ 5	446,435	299,281	(2,640)	(105,463)
Beginning Balance (in shares) at Dec. 31, 2019		38,967,079
Beginning Balance at Dec. 31, 2019	1,131,906	$ 5	438,591	800,792	(1,994)	(105,488)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of restricted stock units to common stock (net of shares of treasury stock purchased) (in shares)		38,144
Conversion of restricted stock units to common stock (net of shares of treasury stock purchased)	(578)					(578)
Settlement of stock appreciation rights in common stock (net of shares of treasury stock purchased) (in shares)		16,704
Settlement of stock appreciation rights in common stock (net of shares of treasury stock purchased)	(245)		(5)			(240)
Convertible debt extinguishment impact (net of tax impact)	(17,829)		(17,829)
Termination of capped call options (in shares)							(25,134)	(14,438)
Stock compensation expense	1,367		1,367
Other comprehensive income (loss)	(551)				(551)
Net income (loss)	76,853			76,853
Ending Balance (in shares) at Mar. 31, 2020		39,021,927
Ending Balance at Mar. 31, 2020	1,190,923	$ 5	422,124	877,645	(2,545)	(106,306)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Convertible debt extinguishment impact, tax impact	1,013
Beginning Balance (in shares) at Dec. 31, 2019		38,967,079
Beginning Balance at Dec. 31, 2019	1,131,906	$ 5	438,591	800,792	(1,994)	(105,488)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Convertible debt extinguishment impact (net of tax impact)			(52,681)
Net income (loss)	104,532
Ending Balance (in shares) at Sep. 30, 2020		39,332,314
Ending Balance at Sep. 30, 2020	1,184,238	$ 5	390,383	905,324	(897)	(110,577)
Beginning Balance (in shares) at Mar. 31, 2020		39,021,927
Beginning Balance at Mar. 31, 2020	1,190,923	$ 5	422,124	877,645	(2,545)	(106,306)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of restricted stock units to common stock (net of shares of treasury stock purchased) (in shares)		230,265
Conversion of restricted stock units to common stock (net of shares of treasury stock purchased)	(2,063)					(2,063)
Settlement of stock appreciation rights in common stock (net of shares of treasury stock purchased) (in shares)		39,962
Settlement of stock appreciation rights in common stock (net of shares of treasury stock purchased)	(1,052)		(276)			(776)
Convertible debt extinguishment impact (net of tax impact)	(20,860)		(20,860)
Termination of capped call options (in shares)							(86,701)	(21,794)
Stock compensation expense	1,855		1,855
Other comprehensive income (loss)	842				842
Net income (loss)	848			848
Ending Balance (in shares) at Jun. 30, 2020		39,292,154
Ending Balance at Jun. 30, 2020	1,170,493	$ 5	402,843	878,493	(1,703)	(109,145)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Convertible debt extinguishment impact, tax impact	1,055
Conversion of restricted stock units to common stock (net of shares of treasury stock purchased) (in shares)		23,800
Conversion of restricted stock units to common stock (net of shares of treasury stock purchased)	(1,185)					(1,185)
Settlement of stock appreciation rights in common stock (net of shares of treasury stock purchased) (in shares)		16,360
Settlement of stock appreciation rights in common stock (net of shares of treasury stock purchased)	(526)		(279)			(247)
Convertible debt extinguishment impact (net of tax impact)	(13,992)		(13,992)
Termination of capped call options (in shares)							(30,624)	(7,095)
Stock compensation expense	1,811		1,811
Other comprehensive income (loss)	806				806
Net income (loss)	26,831			26,831
Ending Balance (in shares) at Sep. 30, 2020		39,332,314
Ending Balance at Sep. 30, 2020	1,184,238	$ 5	$ 390,383	$ 905,324	$ (897)	$ (110,577)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Convertible debt extinguishment impact, tax impact	$ 318