Consolidated statement of stockholders' equity - USD ($) shares in Thousands, $ in Thousands	Total	Common stock	Additional paid-in capital	Treasury stock (at cost)	Accumulated deficit
Balance at beginning of period (in shares) at Dec. 31, 2020		12,020		0
Balance at beginning of period at Dec. 31, 2020	$ (21,443)	$ 120	$ 2,398,464	$ 0	$ (2,420,027)
Increase (Decrease) in Stockholders' Equity
Restricted stock awards (in shares)		188
Restricted stock awards	0	$ 2	(2)
Restricted stock forfeitures (in shares)		(1)
Stock exchanged for tax withholding (in shares)				37
Stock exchanged for tax withholding	(1,290)			$ (1,290)
Retirement of treasury stock (in shares)		(37)		(37)
Retirement of treasury stock	0		(1,290)	$ 1,290
Share-settled equity-based compensation	2,738		2,738
Issuance of common stock, net of costs (in shares)		724
Issuance of common stock, net of costs	26,866	$ 7	26,859
Performance share conversion (in shares)		6
Net loss	(75,439)				(75,439)
Balance at end of period (in shares) at Mar. 31, 2021		12,900		0
Balance at end of period at Mar. 31, 2021	(68,568)	$ 129	2,426,769	$ 0	(2,495,466)
Balance at beginning of period (in shares) at Dec. 31, 2021		17,075		0
Balance at beginning of period at Dec. 31, 2021	513,780	$ 171	2,788,628	$ 0	(2,275,019)
Increase (Decrease) in Stockholders' Equity
Restricted stock awards (in shares)		232
Restricted stock awards	0	$ 2	(2)
Restricted stock forfeitures (in shares)		(4)
Stock exchanged for tax withholding (in shares)				76
Stock exchanged for tax withholding	(5,847)			$ (5,847)
Retirement of treasury stock (in shares)		(76)		(76)
Retirement of treasury stock	0	$ (1)	(5,846)	$ 5,847
Share-settled equity-based compensation	2,636		2,636
Performance share conversion (in shares)		75
Performance share conversion	0	$ 1	(1)
Net loss	(86,781)				(86,781)
Balance at end of period (in shares) at Mar. 31, 2022		17,302		0
Balance at end of period at Mar. 31, 2022	$ 423,788	$ 173	$ 2,785,415	$ 0	$ (2,361,800)