Acquisitions (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Allegheny County Airport – Allegheny County Airport [Member]
Business Acquisition [Line Items]
Bonus Payment in Escrow	7.60%
Bonus Payment	$ 46,315
Ryerson Dam and Lake [Member]
Business Acquisition [Line Items]
Business Acquisition, Contingent Consideration, Potential Cash Payment	36,000
Gas and Oil Area, Undeveloped, Gross	506,000
Bonus Payment	$ 13,728
Allegheny County Airport – Pittsburgh International Airport [Member] [Member]
Business Acquisition [Line Items]
Gas and Oil Area, Undeveloped, Gross	9,300

An up-front payment made to the lessor when an oil and gas lease is signed.

No definition available.

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- Definition

% of bonus payment placed into escrow.

+ References

No definition available.

+ Details

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- Definition

Amount of potential cash payments that could result from the contingent consideration arrangement.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph f

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Definition

Lease area in which a working interest is owned and on which wells have not been drilled or completed to a point that would permit the production of commercial quantities of oil and gas regardless of whether or not such area contains proved reserves.

+ References

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

-Publisher SEC

-Name Industry Guide

-Number 2

-Paragraph 5

+ Details

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