Supplemental Oil and Gas Disclosures (Unaudited) - Capitalized Cost Related to Oil and Natural Gas Producing Activities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Capitalized Costs Relating To Oil And Gas Producing Activities [Line Items]
Total costs	$ 311,745	$ 255,582
Consolidated Entities [Member]
Capitalized Costs Relating To Oil And Gas Producing Activities [Line Items]
Unproved oil and gas properties	90,446	100,320
Proved oil and gas properties	221,299	155,262
Total costs	311,745	255,582
Less accumulated depreciation, depletion and amortization	(48,252)	(22,941)
Net capitalized costs	$ 263,493	$ 232,641

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Amount of accumulated depreciation, depletion, amortization and valuation allowance relating to oil and gas producing activities.

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The sum of capitalized costs relating to oil and gas producing activities before accounting for accumulated depreciation.

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Net amount of capitalized costs relating to oil and gas producing activities.

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Capitalized costs of proved properties incurred for any combination mineral interests acquisitions; wells and related equipment; support equipment and facilities; and uncompleted wells and equipment and other costs not previously disclosed within this table.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 13

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 360

-Glossary Proved Properties

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-Publisher FASB

-Name Accounting Standards Codification

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Capitalized costs of unproved properties incurred for any combination mineral interests acquisitions and other costs not previously disclosed within this table.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 13

-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61901-109447

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Properties

-URI http://asc.fasb.org/extlink&oid=21914647

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-Name Accounting Standards Codification

-Topic 932

-Glossary Unproved Properties

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