Supplemental Oil and Gas Disclosures (Unaudited) - Information About Results of Operations of Oil and Natural Gas Interests (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Consolidated entities
Results of operations	$ (5,777)	$ (170,567)	$ (19,703)
Consolidated Entities
Consolidated entities
Revenues	10,111	51,553	82,919
Production costs	(4,392)	(19,820)	(19,727)
Exploration costs	(124)	(11,864)	(17,416)
Depreciation, depletion, amortization	(2,157)	(28,774)	(29,442)
Results of Operations, Impairment of Oil and Gas Properties	(612)	(164,831)	(32,665)
Oil and gas administrative expenses	(8,700)	(11,700)	(17,000)
Results of Operations, Accretion of Asset Retirement Obligations	(56)	(144)	(121)
Income tax expenses	(20)	14,717	13,398
Results of operations	(5,950)	(170,863)	(20,054)
Equity Method Investee
Consolidated entities
Royalty revenues	284	428	786
Production costs	(76)	(102)	(105)
Oil and gas administrative expenses	(35)	(51)	(95)
Income tax expenses	0	21	(235)
Results of operations	$ 173	$ 296	$ 351