Parent Guarantor - Schedule of Condensed Consolidating Statements of Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Cash flows from operating activities	$ 77,683	$ 54,317
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(130,862)	(88,854)
Additions to furniture, fixtures and other	(1,309)	(122)
Repayment of debt associated with merger, net of cash acquired	0	(53,357)
Other investing activities	(273)	(157)
Cash flows from financing activities:
Proceeds from debt	70,000
Principal payments on debt	(1,859)	(116)
Other financing activities	(1,496)	(1,485)
Increase (Decrease) in Cash and Cash Equivalents	11,884	(89,774)
Beginning Cash and Cash Equivalents	32,774	314,466
Ending Cash and Cash Equivalents	44,658	224,692
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
Repayment of debt associated with merger, net of cash acquired		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
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
Repayment of debt associated with merger, net of cash acquired		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	77,683	54,317
Cash flows from investing activities:
Additions to oil and gas properties, including acquisitions	(130,862)	(88,854)
Additions to furniture, fixtures and other	(1,309)	(122)
Repayment of debt associated with merger, net of cash acquired		(53,357)
Other investing activities	(273)	(157)
Cash flows from financing activities:
Proceeds from debt	70,000
Principal payments on debt	(1,859)	(116)
Other financing activities	(1,496)	(1,485)
Increase (Decrease) in Cash and Cash Equivalents	11,884	(89,774)
Beginning Cash and Cash Equivalents	32,774	314,466
Ending Cash and Cash Equivalents	$ 44,658	$ 224,692