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Acquisitions (Details) (USD $) | 1 Months Ended | 3 Months Ended | 0 Months Ended |  | 0 Months Ended
--- | --- | --- | --- | --- | ---
Feb. 28, 2011 | Mar. 31, 2013 | Mar. 31, 2012 | Feb. 15, 2013 Utica Shale [Member] well acre | Dec. 21, 2012 Utica Shale [Member] | Dec. 18, 2012 Utica Shale [Member] | Dec. 19, 2012 Utica Shale [Member] acre | Dec. 24, 2012 Utica Shale [Member] acre | Dec. 17, 2012 Utica Shale [Member] acre | Feb. 15, 2013 Common Stock [Member] Public Offering [Member] | Jan. 07, 2013 Common Stock [Member] Public Offering [Member] | Dec. 24, 2012 Common Stock [Member] Public Offering [Member]
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Period allowed for refusal | 6 months |  |  |  |  |  |  |  |  |  |  |
Affiliates participation ratio |  | 50.00% |  |  |  |  |  |  |  |  |  |
Gas and oil acreage, undeveloped, net |  |  |  | 22,000 |  |  | 7,000 | 37,000 | 30,000 |  |  |
Cash price of ownership interest |  |  |  | $ 220,000,000 | $ 70,000,000 | $ 302,000,000 | $ 372,000,000 |  |  |  |  |
Amount put in escrow |  |  |  | 33,600,000 |  |  | 53,900,000 |  |  |  |  |
Stock option, portion attributable to underwriters (shares) |  |  |  |  |  |  |  |  |  |  | 900,000 | 750,000
Proceeds from issuance of common stock, net of offering costs |  | $ 357,640,000 |  | $ 325,800,000 |  |  |  | $ 460,700,000 |  | $ 325,800,000 |  | $ 460,700,000
Increase in lease interest, percentage |  |  |  | 16.20% |  |  |  |  |  |  |  |
Lease interest, percentage |  |  |  | 93.80% |  |  |  |  |  |  |  |
Existing wells excluded |  |  |  | 14 |  |  |  |  |  |  |  |
Future wells excluded |  |  |  | 16 |  |  |  |  |  |  |  |

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- Definition The designation of funds furnished by a borrower to a lender to assure future payments of the borrower's real estate taxes and insurance obligations with respect to a mortgaged property. Escrow deposits may be made for a variety of other purposes such as earnest money and contingent payments. This element excludes replacement reserves which are an escrow separately provided for within the US GAAP taxonomy. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.10) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Definition Fractional interest owned based on working interests or other economic arrangements of lease area 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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