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Acquisitions (Details) (USD $)
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1 Months Ended | 9 Months Ended | 0 Months Ended | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Feb. 28, 2011
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Sep. 30, 2013
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Sep. 30, 2012
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May 31, 2013
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Feb. 15, 2013
Common Stock [Member]
Public Offering [Member]
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Jan. 07, 2013
Common Stock [Member]
Public Offering [Member]
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Dec. 24, 2012
Common Stock [Member]
Public Offering [Member]
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Feb. 15, 2013
Utica Shale [Member]
well
acre
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Dec. 21, 2012
Utica Shale [Member]
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Dec. 18, 2012
Utica Shale [Member]
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Dec. 19, 2012
Utica Shale [Member]
acre
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Dec. 24, 2012
Utica Shale [Member]
acre
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Dec. 17, 2012
Utica Shale [Member]
acre
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| 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 | (10,000,000) | 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 | $ 359,040,000 | $ 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 | ||||||||||||