SUMMARIZED QUARTERLY FINANCIAL INFORMATION - UNAUDITED - Results of Operations by Quarter (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	2 Months Ended	3 Months Ended							10 Months Ended	12 Months Ended
	Mar. 31, 2017	Feb. 28, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Results Of Operations By Quarter [Line Items]
Operating revenue	$ 25,809		$ 76,327	$ 79,525	$ 76,722					$ 250,284
Income (loss) from operations	(258,594)		5,302	2,653	(4,519)					(255,158)
Net income (loss)	$ (259,613)		$ 17,138	$ 1,297	$ (6,461)					$ (247,639)
Basic income (loss) per share (in usd per share)	$ (12.98)		$ 0.86	$ 0.06	$ (0.32)					$ (12.38)
Diluted income (loss) per share (in usd per share)	$ (12.98)		$ 0.86	$ 0.06	$ (0.32)					$ (12.38)
Write-down of oil and gas properties	$ 256,435		$ 0	$ 0	$ 0					$ 256,435
Gain (loss) on Appalachia Properties divestiture	0		0	(132)	27					(105)
Reorganization items	0		0	0	0					0
Other expense	$ 0		$ 369	$ 47	$ 814					1,230
Restructuring fees										739
Other operational expenses										$ 3,359
Predecessor
Results Of Operations By Quarter [Line Items]
Operating revenue		$ 68,922				$ 113,107	$ 94,427	$ 89,319	$ 80,677		$ 377,392	$ 544,649
Income (loss) from operations		209,119				(90,234)	(72,128)	(174,656)	(172,150)		(509,168)	(1,365,323)
Net income (loss)		$ 630,317				$ (116,406)	$ (89,635)	$ (195,761)	$ (188,784)		$ (590,586)	$ (1,090,915)
Basic income (loss) per share (in usd per share)		$ 110.99				$ (20.76)	$ (16.01)	$ (35.05)	$ (33.89)		$ (105.63)	$ (197.45)
Diluted income (loss) per share (in usd per share)		$ 110.99				$ (20.76)	$ (16.01)	$ (35.05)	$ (33.89)		$ (105.63)	$ (197.45)
Write-down of oil and gas properties		$ 0				$ 73,094	$ 36,484	$ 118,649	$ 129,204		$ 357,431	$ 1,362,447
Gain (loss) on Appalachia Properties divestiture		213,453									0	0
Reorganization items		(437,744)				10,947	0	0	0		10,947	0
Other expense		13,336									596	434
Restructuring fees		0				13,424	5,784	9,436	953		29,597	0
Other operational expenses		$ 530				$ 6,187	$ 9,059	$ 27,680	$ 12,527		$ 55,453	$ 2,360