CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Accounting Standards Update 2016-02	Accounting Standards Update 2016-13	Accounting Standards Update 2014-09	Common Stock	Preferred Stock	Paid-in Capital	Retained Earnings	Retained Earnings Accounting Standards Update 2016-02	Retained Earnings Accounting Standards Update 2016-13	Retained Earnings Accounting Standards Update 2014-09	Accumulated Other Comprehensive Income (Loss)
Balance as of beginning of period (in shares) at Dec. 31, 2017					15,019
Balance as of beginning of period at Dec. 31, 2017	$ 221,639			$ (2,659)	$ 150	$ 0	$ 194,123	$ 27,366			$ (2,659)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	224,785							224,785
Share-based compensation							4,618
Restricted stock unit vesting (in shares)					61
Restricted stock unit vesting	(1,110)				$ 1		(1,111)
Other	(82)						0	0				(82)
Balance as of end of period (in shares) at Dec. 31, 2018					15,080
Balance as of end of period at Dec. 31, 2018	447,355	$ (94)			$ 151	0	197,630	249,492	$ (94)			82
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	70,589							70,589
Share-based compensation							4,082
Restricted stock unit vesting (in shares)					56
Restricted stock unit vesting	(1,046)				$ 0		(1,046)
Other	141											141
Balance as of end of period (in shares) at Dec. 31, 2019					15,136
Balance as of end of period at Dec. 31, 2019	520,745		$ (76)		$ 151	0	200,666	319,987		$ (76)		(59)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(310,557)							(310,557)
Share-based compensation							3,284
Restricted stock unit vesting (in shares)					64
Restricted stock unit vesting	(486)				$ 1		(487)
Other	72											72
Balance as of end of period (in shares) at Dec. 31, 2020					15,200
Balance as of end of period at Dec. 31, 2020	$ 212,838				$ 152	$ 0	$ 203,463	$ 9,354				$ (131)