Supplemental Oil and Gas Disclosures (Unaudited) - Capitalized Cost Related to Oil and Natural Gas Producing Activities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Capitalized Costs Relating To Oil And Gas Producing Activities [Line Items]
Total costs	$ 138,855	$ 311,745
Consolidated Entities [Member]
Capitalized Costs Relating To Oil And Gas Producing Activities [Line Items]
Unproved oil and gas properties	19,441	90,446
Proved oil and gas properties	119,414	221,299
Total costs	138,855	311,745
Less accumulated depreciation, depletion and amortization	(58,242)	(48,252)
Net capitalized costs	$ 80,613	$ 263,493