Derivatives (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019 MMBTU Boe $ / bbl $ / MMBTU	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2021 MMBTU Boe $ / bbl $ / MMBTU	Dec. 31, 2020 MMBTU Boe $ / bbl $ / MMBTU
Derivative [Line Items]
Settlements paid for early terminations of derivatives, net | $			$ 5,409	$ 0
Commodity derivatives | Not designated as hedges
Derivative [Line Items]
Settlements paid for early terminations of derivatives, net | $		$ 5,400
Scenario, Forecast | Put Instrument 1 | Not designated as hedges | Oil derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	322,000				0	366,000
Weighted-average ($/Bbl) | $ / bbl	55.00				0	45.00
Scenario, Forecast | Put Instrument 2 | Not designated as hedges | Oil derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	322,000				0	0
Weighted-average ($/Bbl) | $ / bbl	4.39				0	0
Scenario, Forecast | Swap | Not designated as hedges | Oil derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	1,978,000					7,173,600
Weighted-average ($/Bbl) | $ / bbl	61.31					59.50
Scenario, Forecast | Swap | Not designated as hedges | Natural gas derivatives
Derivative [Line Items]
Volume (Bbl) | MMBTU	9,844,000				14,052,500	23,790,000
Weighted-average ($/Bbl) | $ / MMBTU	3.09				2.63	2.72
Scenario, Forecast | Swap | Not designated as hedges | Ethane | NGL derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	598,000				912,500	366,000
Weighted-average ($/Bbl) | $ / bbl	14.22				12.01	13.60
Scenario, Forecast | Swap | Not designated as hedges | Propane | NGL derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	478,400				730,000	1,244,400
Weighted-average ($/Bbl) | $ / bbl	27.97				25.52	26.58
Scenario, Forecast | Swap | Not designated as hedges | Normal Butane | NGL derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	184,000				255,500	439,200
Weighted-average ($/Bbl) | $ / bbl	30.73				27.72	28.69
Scenario, Forecast | Swap | Not designated as hedges | Isobutane | NGL derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	46,000				67,525	109,800
Weighted-average ($/Bbl) | $ / bbl	31.08				28.79	29.99
Scenario, Forecast | Swap | Not designated as hedges | Natural Gasoline | NGL derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	156,400				237,250	402,600
Weighted-average ($/Bbl) | $ / bbl	45.80				44.31	45.15
Scenario, Forecast | Collar | Not designated as hedges | Oil derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	0				912,500	0
Scenario, Forecast | Collar | Not designated as hedges | Floor | Oil derivatives
Derivative [Line Items]
Weighted-average ($/Bbl) | $ / bbl	0				45.00	0
Scenario, Forecast | Collar | Not designated as hedges | Ceiling | Oil derivatives
Derivative [Line Items]
Weighted-average ($/Bbl) | $ / bbl	0				71.00	0
Scenario, Forecast | Commodity | Not designated as hedges | NGL derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	1,462,800				2,202,775	2,562,000
Scenario, Forecast | Commodity | Not designated as hedges | Floor | Oil derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	2,300,000				912,500	7,539,600
Weighted-average ($/Bbl) | $ / bbl	60.42				45.00	58.79
Scenario, Forecast | Commodity | Not designated as hedges | Ceiling | Oil derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	1,978,000				912,500	7,173,600
Weighted-average ($/Bbl) | $ / bbl	61.31				71.00	59.50
Scenario, Forecast | Basis Swap | Not designated as hedges | Oil derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	920,000				0	0
Weighted-average ($/Bbl) | $ / bbl	(2.89)				0	0
Scenario, Forecast | Basis Swap 2 | Not designated as hedges | Oil derivatives
Derivative [Line Items]
Volume (Bbl) | Boe	184,000				0	0
Weighted-average ($/Bbl) | $ / bbl	(4.05)				0	0
Scenario, Forecast | Basis Swap 4 | Not designated as hedges | Natural gas derivatives
Derivative [Line Items]
Volume (Bbl) | MMBTU	9,844,000				23,360,000	32,574,000
Weighted-average ($/Bbl) | $ / MMBTU	(1.51)				(0.47)	(0.76)
Level 3 | Commodity derivatives | Not designated as hedges
Derivative [Line Items]
Present value of deferred premiums | $		$ 7,200	$ 7,200