Organization and Summary of Significant Accounting Policies - Summary Of Changes In Future Abandonment Liabilities (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligations at January 1		$ 96,178	$ 102,909	$ 76,708
Accretion expense		5,886	6,086	4,740
Revisions	[1]	7,801	(12,755)	15,068
Plus: Additions for new assets		6,884	2,692	7,404
Less: Plugging costs and sold assets		(2,343)	(2,754)	(1,011)
Total asset retirement obligations at December 31		114,406	96,178	102,909
Less: Current portion of asset retirement obligations at December 31	[2]	2,612	1,742	1,658
Non-current portion of asset retirement obligations at December 31		$ 111,794	$ 94,436	$ 101,251

[1] Revisions primarily represent changes in the present value of liabilities resulting from changes in estimated costs and economic lives of producing properties.

[2] Balance is included in the caption “Accrued liabilities and other” in the consolidated balance sheets.