Long-Term Debt (Narrative) (Details) (USD $)
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3 Months Ended | 9 Months Ended | 1 Months Ended | 0 Months Ended | 0 Months Ended | ||||||||||||||||||||||||||||||||||
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Sep. 30, 2014
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Sep. 30, 2013
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Sep. 30, 2014
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Sep. 30, 2013
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Sep. 30, 2014
Senior Notes [Member]
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Aug. 18, 2014
Senior Notes [Member]
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Dec. 31, 2013
Senior Notes [Member]
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Dec. 21, 2012
Senior Notes [Member]
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Oct. 17, 2012
Senior Notes [Member]
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Mar. 31, 2011
Building Loans [Member]
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Sep. 30, 2014
Building Loans [Member]
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Dec. 31, 2013
Building Loans [Member]
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Sep. 30, 2014
Minimum [Member]
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Dec. 21, 2012
Minimum [Member]
Senior Notes [Member]
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Sep. 30, 2014
Maximum [Member]
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Dec. 21, 2012
Maximum [Member]
Senior Notes [Member]
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Apr. 23, 2014
Nova Scotia, Amegy, KeyBank [Member]
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Sep. 30, 2014
Nova Scotia, Amegy, KeyBank [Member]
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Apr. 23, 2014
Nova Scotia, Amegy, KeyBank [Member]
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Apr. 22, 2014
Nova Scotia, Amegy, KeyBank [Member]
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Dec. 27, 2013
Nova Scotia, Amegy, KeyBank [Member]
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Apr. 23, 2014
Nova Scotia, Amegy, KeyBank [Member]
Base Rate Loans [Member]
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Apr. 23, 2014
Nova Scotia, Amegy, KeyBank [Member]
Base Rate Loans [Member]
Federal Funds Rate [Member]
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Apr. 23, 2014
Nova Scotia, Amegy, KeyBank [Member]
Base Rate Loans [Member]
Eurodollar [Member]
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Apr. 23, 2014
Nova Scotia, Amegy, KeyBank [Member]
Euro Dollar Loans [Member]
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Sep. 30, 2014
Nova Scotia, Amegy, KeyBank [Member]
Letter of Credit [Member]
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Apr. 23, 2014
Nova Scotia, Amegy, KeyBank [Member]
Letter of Credit [Member]
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Apr. 22, 2014
Nova Scotia, Amegy, KeyBank [Member]
Letter of Credit [Member]
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Debt Instrument [Line Items] | |||||||||||||||||||||||||||||||||||||||
Interest cost capitalized, undeveloped properties | $ 3,400,000 | $ 3,500,000 | $ 9,600,000 | $ 9,000,000 | |||||||||||||||||||||||||||||||||||
Revolving credit facility | 1,500,000,000.0 | ||||||||||||||||||||||||||||||||||||||
Borrowing capacity | 275,000,000.0 | 275,000,000.0 | 150,000,000.0 | 70,000,000.0 | 20,000,000.0 | ||||||||||||||||||||||||||||||||||
Remaining borrowing capacity | 233,300,000 | ||||||||||||||||||||||||||||||||||||||
Credit facility outstanding | 41,700,000 | [1] | |||||||||||||||||||||||||||||||||||||
Proposed increased borrowing capacity | 450,000,000.0 | ||||||||||||||||||||||||||||||||||||||
Applicable rate, minimum | 0.50% | 1.50% | |||||||||||||||||||||||||||||||||||||
Applicable rate, maximum | 1.50% | 2.50% | |||||||||||||||||||||||||||||||||||||
Basis spread | 0.50% | 1.00% | |||||||||||||||||||||||||||||||||||||
Debt instrument, description of rate | LIBOR01 | ||||||||||||||||||||||||||||||||||||||
Debt covenant ratio for reasonable transactions | 2.00 | ||||||||||||||||||||||||||||||||||||||
Debt covenant ratio for EBITDAX | 3.00 | ||||||||||||||||||||||||||||||||||||||
Building Loan Outstanding Amount Of Building Loan Refinanced | 600,000,000 | [2] | 600,000,000.0 | 300,000,000 | [2] | 600,000,000.0 | 600,000,000.0 | 2,400,000 | 1,868,000 | [3] | 1,995,000 | [3] | |||||||||||||||||||||||||||
Stated interest rate | 7.75% | 7.75% | 7.75% | 5.82% | |||||||||||||||||||||||||||||||||||
Loan, periodic payment | 22,000 | ||||||||||||||||||||||||||||||||||||||
Debt issued | 300,000,000.0 | 50,000,000.0 | 250,000,000.0 | ||||||||||||||||||||||||||||||||||||
Redemption of principal amount plus aggregate net proceeds | 100.00% | 35.00% | |||||||||||||||||||||||||||||||||||||
Percentage of notes required to be outstanding for redemption | 65.00% | ||||||||||||||||||||||||||||||||||||||
Discount issue price, price | 106.00% | 98.534% | |||||||||||||||||||||||||||||||||||||
Unamortized discount | 3,700,000 | ||||||||||||||||||||||||||||||||||||||
Effective interest rate | 6.561% | 7.531% | 8.00% | ||||||||||||||||||||||||||||||||||||
Premium issue price, percent | 101.00% | ||||||||||||||||||||||||||||||||||||||
Unamortized premium | $ 18,000,000 | $ 500,000 | |||||||||||||||||||||||||||||||||||||
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