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Supplemental Oil and Gas Disclosures (Unaudited) - Changes in Standardized Measure of Discounted Future Net Cash Flow (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Schedule Of Changes In Standardized Measure Of Discounted Future Net Cash Flows [Line Items] |  |  |
Beginning Balance | $ 67,498 | $ 165,616 | $ 136,853
Changes resulting from: |  |  |
Net change in sales prices and production costs | (3,645) | (137,648) | 507
Net change in future development costs | 0 | 92 | 1,308
Sales of oil and gas, net of production costs | (5,871) | (32,160) | (63,979)
Net change due to extensions and discoveries | 410 | 11,747 | 58,228
Net change due to acquisition of reserves | 0 | 0 | 2,778
Net change due to divestitures of reserves | (63,535) | (15,855) | (5,804)
Net change due to revisions of quantity estimates | 1,367 | (15,431) | 14,960
Previously estimated development costs incurred | 0 | (15,096) | (15,497)
Accretion of discount | 3,105 | 22,886 | 18,277
Net change in timing and other | (208) | 3,808 | 4,313
Net change in income taxes | 11,864 | 49,347 | (17,322)
Aggregate change for the year | (56,513) | (98,118) | 28,763
Ending Balance | 10,985 | 67,498 | 165,616
Consolidated Entities |  |  |
Schedule Of Changes In Standardized Measure Of Discounted Future Net Cash Flows [Line Items] |  |  |
Beginning Balance | 66,796 | 163,841 | 135,553
Changes resulting from: |  |  |
Net change in sales prices and production costs | (3,585) | (136,536) | (1,064)
Net change in future development costs | 0 | 92 | 1,308
Sales of oil and gas, net of production costs | (5,663) | (31,732) | (63,192)
Net change due to extensions and discoveries | 410 | 11,747 | 58,228
Net change due to acquisition of reserves | 0 | 0 | 2,778
Net change due to divestitures of reserves | (63,535) | (15,855) | (5,804)
Net change due to revisions of quantity estimates | 1,304 | (15,164) | 15,303
Previously estimated development costs incurred | 0 | (15,096) | (15,497)
Accretion of discount | 2,992 | 22,600 | 18,067
Net change in timing and other | (128) | 4,018 | 4,198
Net change in income taxes | 11,722 | 48,689 | (17,031)
Aggregate change for the year | (56,483) | (97,045) | 28,288
Ending Balance | 10,313 | 66,796 | 163,841
Equity Method Investee |  |  |
Schedule Of Changes In Standardized Measure Of Discounted Future Net Cash Flows [Line Items] |  |  |
Beginning Balance | 702 | 1,775 | 1,300
Changes resulting from: |  |  |
Net change in sales prices and production costs | (60) | (1,112) | 1,571
Net change in future development costs | 0 | 0 | 0
Sales of oil and gas, net of production costs | (208) | (428) | (787)
Net change due to extensions and discoveries | 0 | 0 | 0
Net change due to acquisition of reserves | 0 | 0 | 0
Net change due to divestitures of reserves |  | 0 | 0
Net change due to revisions of quantity estimates | 63 | (267) | (343)
Previously estimated development costs incurred | 0 | 0 | 0
Accretion of discount | 113 | 286 | 210
Net change in timing and other | (80) | (210) | 115
Net change in income taxes | 142 | 658 | (291)
Aggregate change for the year | (30) | (1,073) | 475
Ending Balance | $ 672 | $ 702 | $ 1,775

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- Definition Amount of decrease in standardized measure of discounted future net cash flow as a result of sales of minerals in place. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 35 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e62500-109447 + Details
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