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Acquisitions (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended | 3 Months Ended |  |
--- | --- | --- | --- | ---
Dec. 31, 2011 A | Dec. 31, 2010 Richland County [Member] A | Dec. 31, 2010 Roosevelt County [Member] A | Jun. 15, 2009 Kerogen Acquisition [Member] | Sep. 30, 2009 Fidelity Acquisition [Member]
Business Acquisition [Line Items] |  |  |  |  |
Number of acres acquired | 0 | 10,000 | 16,700 |  |
Payments to acquire land |  | $ 30.1 | $ 52.3 |  |
Acquisition cost |  |  |  | 27.1 | 10.7
Estimated fair value of acquisition properties |  |  |  | $ 27.1 | $ 10.7

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- Definition The number of net leasehold acres acquired. + References No definition available. + Details
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- Definition The total cost of the acquired entity including the cash paid to shareholders of acquired entities, fair value of debt and equity securities issued to shareholders of acquired entities, the fair value of the liabilities assumed, and direct costs of the acquisition. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 141 -Paragraph 51 -Subparagraph d -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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- Definition The cash outflow from the acquisition of real estate intended to generate income for the owner; excludes land acquired for use by the owner. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 17 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3213-108585 + Details
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