Summary of Significant Accounting Policies - Summary of Property and Equipment Including Oil and Natural Gas Properties (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Oil and natural gas properties:
Unproved properties	$ 547,963	$ 459,549
Proved properties	2,027,472	1,896,081
Gross oil and natural gas properties	2,575,435	2,355,630
Less accumulated depreciation, depletion and amortization	(1,311,180)	(1,248,200)
Total oil and natural gas properties, net	1,264,255	1,107,430
Other property and equipment	14,450	13,508
Less accumulated depreciation	(7,501)	(6,566)
Other property and equipment, net	6,949	6,942
Total property and equipment, net	$ 1,271,204	$ 1,114,372

Amount of accumulated depreciation, depletion and amortization of oil and gas property carried under the successful effort method. Oil and gas property include, but not limited to, the entity's wells and related equipment and facilities.

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Oil and Gas properties, gross, carried under the successful effort method.

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Oil and gas properties net of accumulated depreciation, depletion, amortization, impairment, and abandonment, carried under the successful effort method.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Amount of accumulated depreciation of long-lived, physical assets used to produce goods and services and not intended for resale, classified as other.

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Oil and Gas properties with proved reserves under the successful effort method.

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Oil and Gas properties with unproved reserves under the successful effort method.

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