Operating Segment Information (Capital Expenditures) (Details) - USD ($) $ in Thousands	4 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2016	Aug. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Capital expenditures	$ 24,333
Predecessor
Segment Reporting Information [Line Items]
Capital expenditures		$ 24,894	$ 127,138	$ 212,728
Gas And Oil Production
Segment Reporting Information [Line Items]
Capital expenditures	23,990
Gas And Oil Production | Predecessor
Segment Reporting Information [Line Items]
Capital expenditures		22,684	111,329	193,131
Other Partnership Management
Segment Reporting Information [Line Items]
Capital expenditures	273
Other Partnership Management | Predecessor
Segment Reporting Information [Line Items]
Capital expenditures		2,046	14,050	14,202
Corporate and Other
Segment Reporting Information [Line Items]
Capital expenditures	$ 70
Corporate and Other | Predecessor
Segment Reporting Information [Line Items]
Capital expenditures		$ 164	$ 1,759	$ 5,395