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Major Lessee (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Major Lessee (Textual) [Abstract]
Minimum Percentage of revenue derived from major two lessees		46.00%
Total revenue attributable		61.00%
Alpha Natural Resources [Member]
Revenues from lessees that exceeded ten percent of total revenues
Revenues		$ 107,267	$ 79,084	$ 64,626
Percent		28.40%	26.20%	25.20%
The Cline Group [Member]
Revenues from lessees that exceeded ten percent of total revenues
Revenues		$ 64,829	$ 62,372	$ 37,369
Percent		17.20%	20.70%	14.60%
Percentage of revenue derived from major lessee	12.00%

X

- Definition

Entity wide revenue major customer percentage.

+ References

No definition available.

+ Details

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X

- Details

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X

- Definition

Minimum percentage of revenue derived from major two lessees.

+ References

No definition available.

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X

- Definition

Percentage of revenue derived from major lessee.

+ References

No definition available.

+ Details

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X

- Definition

Percentage of revenues from lessees exceeding ten percent of revenues.

+ References

No definition available.

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X

- 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 Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 19

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 2: 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=6453417&loc=d3e39896-112707

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