Fair Value Disclosures (Non-recurring Measurements) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Original Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unproved oil and gas properties	$ 816,282
Proved oil and gas properties	1,895,670
Total	2,711,952
Original Carrying Value | Predecessor
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unproved oil and gas properties		$ 0
Proved oil and gas properties		3,350
Total		3,350
Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unproved oil and gas properties	74,217
Proved oil and gas properties	604,023
Total	678,240
Estimated Fair Value | Predecessor
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unproved oil and gas properties		0
Proved oil and gas properties		2,162
Total		2,162
Impairment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unproved oil and gas properties	742,065
Proved oil and gas properties	1,291,647
Total	$ 2,033,712
Impairment | Predecessor
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unproved oil and gas properties		0
Proved oil and gas properties		1,188
Total		$ 1,188