Parent Guarantor - Schedule of Condensed Consolidating Statements of Cash Flows (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Condensed Financial Statements, Captions [Line Items]
Cash flows from operating activities	$ 195,394	$ 160,185
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(375,976)	(322,614)
Additions to furniture, fixtures and other	(3,958)	(616)
Payment of acquiree's debt associated with merger, net of cash acquired	0	(53,357)
Proceeds from sale of properties	1,334	(221)
Other investing activities	(1,400)	232
Cash flows from financing activities:
Proceeds from debt	200,000
Principal payments on debt	(26,859)	(350)
Other financing activities	(1,741)	(4,745)
Increase (Decrease) in Cash and Cash Equivalents	(13,206)	(221,486)
Beginning Cash and Cash Equivalents	32,774	314,466
Ending Cash and Cash Equivalents	19,568	92,980
Intercompany Eliminations
Condensed Financial Statements, Captions [Line Items]
Cash flows from operating activities	0	0
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	0	0
Additions to furniture, fixtures and other	0	0
Payment of acquiree's debt associated with merger, net of cash acquired		0
Proceeds from sale of properties	0	0
Other investing activities		0
Cash flows from financing activities:
Proceeds from debt	0
Principal payments on debt	0	0
Other financing activities	0	0
Increase (Decrease) in Cash and Cash Equivalents	0	0
Beginning Cash and Cash Equivalents	0	0
Ending Cash and Cash Equivalents	0	0
Parent Guarantor | Reportable Legal Entities
Condensed Financial Statements, Captions [Line Items]
Cash flows from operating activities	0	0
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	0	0
Additions to furniture, fixtures and other	0	0
Payment of acquiree's debt associated with merger, net of cash acquired		0
Proceeds from sale of properties	0	0
Other investing activities	0	0
Cash flows from financing activities:
Proceeds from debt	0
Principal payments on debt	0	0
Other financing activities	0	0
Increase (Decrease) in Cash and Cash Equivalents	0	0
Beginning Cash and Cash Equivalents	0	0
Ending Cash and Cash Equivalents	0	0
Subsidiary Issuer | Reportable Legal Entities
Condensed Financial Statements, Captions [Line Items]
Cash flows from operating activities	195,394	160,185
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(375,976)	(322,614)
Additions to furniture, fixtures and other	(3,958)	(616)
Payment of acquiree's debt associated with merger, net of cash acquired		(53,357)
Proceeds from sale of properties	1,334	(221)
Other investing activities	(1,400)	232
Cash flows from financing activities:
Proceeds from debt	200,000
Principal payments on debt	(26,859)	(350)
Other financing activities	(1,741)	(4,745)
Increase (Decrease) in Cash and Cash Equivalents	(13,206)	(221,486)
Beginning Cash and Cash Equivalents	32,774	314,466
Ending Cash and Cash Equivalents	19,568	$ 92,980
Subsidiary Guarantor | Reportable Legal Entities
Condensed Financial Statements, Captions [Line Items]
Cash flows from operating activities	0
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	0
Additions to furniture, fixtures and other	0
Proceeds from sale of properties	0
Other investing activities	0
Cash flows from financing activities:
Proceeds from debt	0
Principal payments on debt	0
Other financing activities	0
Increase (Decrease) in Cash and Cash Equivalents	0
Beginning Cash and Cash Equivalents	0
Ending Cash and Cash Equivalents	$ 0