Organization and Summary of Significant Accounting Policies - Components of Inventories (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Tubular goods and equipment	$ 14,946	$ 15,243
Crude oil	82,460	96,744
Total	$ 97,406	$ 111,987