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Major Lessees - Revenues from Lessees that Exceeded Ten Percent of Total Revenues and Other Income (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Foresight Energy |  |  |
Operating Leased Assets [Line Items] |  |  |
Revenues | $ 86,614 | $ 81,546 | $ 88,432
Percent | 17.70% | 20.40% | 24.70%
Alpha Natural Resources |  |  |
Operating Leased Assets [Line Items] |  |  |
Revenues | $ 34,364 | $ 48,783 | $ 55,147
Percent | 7.00% | 12.20% | 15.40%

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- Definition Percentage of revenues from lessees exceeding ten percent of revenues. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition The total amount of revenue recognized for the period from operating leases, including minimum lease revenue, contingent revenue, percentage revenue and sublease revenue. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=7501430&loc=d3e39896-112707 + Details
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- Details
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- Details
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