UNAUDITED CONDENSED STATEMENTS OF CONSOLIDATED EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Warrants [Member]	Additional Paid in Capital [Member]	Accumulated Earnings (Deficit) [Member]
Balance at Dec. 31, 2017	$ 393,933	$ 3	$ 4,788	$ 387,856	$ 1,286
Net income (loss)	3,239	0	0	0	3,239
Share-based compensation expense	1,176	0	0	1,176	0
Restricted shares repurchased	(208)	0	0	(208)	0
Balance at Mar. 31, 2018	398,140	3	4,788	388,824	4,525
Balance at Dec. 31, 2017	393,933	3	4,788	387,856	1,286
Net income (loss)	(22,040)
Balance at Jun. 30, 2018	372,896	3	4,788	388,859	(20,754)
Balance at Mar. 31, 2018	398,140	3	4,788	388,824	4,525
Net income (loss)	(25,279)	0	0	0	(25,279)
Share-based compensation expense	336	0	0	336	0
Restricted shares repurchased	(301)	0	0	(301)	0
Balance at Jun. 30, 2018	372,896	3	4,788	388,859	(20,754)
Balance at Dec. 31, 2018	416,558	3	4,788	355,872	55,895
Net income (loss)	(31,477)	0	0	0	(31,477)
Costs incurred in conjunction with tender offer	(107)	0	0	(107)	0
Share-based compensation expense	1,443	0	0	1,443	0
Common stock repurchased and retired under the share repurchase program	(920)	0	0	(920)	0
Balance at Mar. 31, 2019	385,497	3	4,788	356,288	24,418
Balance at Dec. 31, 2018	416,558	3	4,788	355,872	55,895
Net income (loss)	(12,836)
Balance at Jun. 30, 2019	405,087	3	4,788	357,237	43,059
Balance at Mar. 31, 2019	385,497	3	4,788	356,288	24,418
Net income (loss)	18,641	0	0	0	18,641
Share-based compensation expense	1,479	0	0	1,479	0
Common stock repurchased and retired under the share repurchase program	(331)	0	0	(331)	0
Restricted shares repurchased	(199)	0	0	(199)	0
Balance at Jun. 30, 2019	$ 405,087	$ 3	$ 4,788	$ 357,237	$ 43,059