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 (shares) at Dec. 31, 2018		233,936		0
Balance at beginning of period at Dec. 31, 2018	$ 1,174,230	$ 2,339	$ 2,375,286	$ 0	$ (1,203,395)
Increase (Decrease) in Stockholders' Equity
Restricted stock awards (shares)		5,986
Restricted stock awards		$ 60	(60)
Restricted stock forfeitures (shares)		(48)
Stock exchanged for tax withholding (shares)				683
Stock exchanged for tax withholding	(2,612)			$ (2,612)
Stock exchanged for cost of exercise of stock options (shares)				18
Stock exchanged for cost of exercise of stock options	$ (76)			$ (76)
Retirement of treasury stock (shares)		(701)		(701)
Retirement of treasury stock		$ (7)	(2,681)	$ 2,688
Exercise of stock options (shares)	18
Exercise of stock options	$ 76
Share-settled equity-based compensation	9,305		9,305
Net income (loss)	(9,491)				(9,491)
Balance at end of period (shares) at Mar. 31, 2019		239,191		0
Balance at end of period at Mar. 31, 2019	1,171,432	$ 2,392	2,381,926	$ 0	(1,212,886)
Balance at beginning of period (shares) at Dec. 31, 2019		237,292		0
Balance at beginning of period at Dec. 31, 2019	841,874	$ 2,373	2,385,355	$ 0	(1,545,854)
Increase (Decrease) in Stockholders' Equity
Restricted stock awards (shares)		2,771
Restricted stock awards		$ 28	(28)
Restricted stock forfeitures (shares)		(139)
Restricted stock forfeitures		$ (2)	2
Stock exchanged for tax withholding (shares)				524
Stock exchanged for tax withholding	(640)			$ (640)
Retirement of treasury stock (shares)		(524)		(524)
Retirement of treasury stock		$ (5)	(635)	$ 640
Share-settled equity-based compensation	3,341		3,341
Net income (loss)	235,095				235,095
Balance at end of period (shares) at Mar. 31, 2020		239,400		0
Balance at end of period at Mar. 31, 2020	$ 1,079,670	$ 2,394	$ 2,388,035	$ 0	$ (1,310,759)