Derivative Instruments (Derivative instruments recorded on the balance sheet at fair value) (Details) - USD ($) $ in Thousands		Sep. 30, 2017	Mar. 21, 2017	Dec. 31, 2016
Fair value of derivative instruments
Derivative assets, gross		$ 14,483
Derivative liabilities, gross		(363)
Derivative assets (liabilities), net		14,120
Netting adjustments	[1]	363
Derivative Liability, Netting adjustments	[1]	(363)
Current derivative assets, net		8,130	$ 19,058
Current derivative liabilities, net		0
Current derivative assets (liabilities), net		8,130
Long-term derivative assets, net		5,990	14,295
Long-term derivative liabilities, net		0
Long-term derivative assets (liabilities), net		5,990
Predecessor
Fair value of derivative instruments
Derivative assets, gross				$ 184
Derivative liabilities, gross				(13,553)
Derivative assets (liabilities), net				(13,369)
Netting adjustments	[1]			184
Derivative Liability, Netting adjustments	[1]			(184)
Current derivative assets, net			19,058	0
Current derivative liabilities, net				(7,525)
Current derivative assets (liabilities), net				(7,525)
Long-term derivative assets, net			$ 14,295	0
Long-term derivative liabilities, net				(5,844)
Long-term derivative assets (liabilities), net				(5,844)
Natural Gas Derivative Contracts
Fair value of derivative instruments
Derivative assets, gross		789
Derivative liabilities, gross		(358)
Derivative assets (liabilities), net		431
Natural Gas Derivative Contracts | Predecessor
Fair value of derivative instruments
Derivative assets, gross				184
Derivative liabilities, gross				(3,658)
Derivative assets (liabilities), net				(3,474)
Crude Oil Derivative Contracts
Fair value of derivative instruments
Derivative assets, gross		13,694
Derivative liabilities, gross		(5)
Derivative assets (liabilities), net		$ 13,689
Crude Oil Derivative Contracts | Predecessor
Fair value of derivative instruments
Derivative liabilities, gross				(9,895)
Derivative assets (liabilities), net				$ (9,895)

[1] Amounts represent the impact of master netting agreements that allow us to net settle positive and negative positions with the same counterparty. Positive and negative positions with counterparties are netted only to the extent that they relate to the same current versus noncurrent classification on the balance sheet.