Long-Term Debt (Narrative) (Details) (USD $)
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3 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 0 Months Ended | 12 Months Ended | 0 Months Ended | |||||||||||||||||||||||||||||||||||||||||
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Mar. 31, 2013
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Mar. 31, 2012
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Dec. 31, 2012
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Dec. 31, 2011
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Mar. 31, 2013
Senior Notes [Member]
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Dec. 31, 2012
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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Oct. 09, 2012
Senior Notes [Member]
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Dec. 31, 2011
Senior Notes [Member]
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Mar. 31, 2013
Building Loans [Member]
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Dec. 31, 2012
Building Loans [Member]
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Dec. 31, 2011
Building Loans [Member]
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Mar. 31, 2011
Building Loans [Member]
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Oct. 09, 2012
Maximum [Member]
Senior Notes [Member]
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Oct. 09, 2012
Minimum [Member]
Senior Notes [Member]
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Dec. 24, 2010
Amegy Bank National Association [Member]
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Sep. 30, 2010
Amegy Bank National Association [Member]
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Oct. 31, 2011
Nova Scotia, KeyBank, Societe Generale [Member]
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May 03, 2011
Nova Scotia, KeyBank, Societe Generale [Member]
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May 02, 2012
Credit Suisse, Deutche Bank, IberiaBank,KeyBank,Amegy Bank, Nova Scotia [Member]
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Dec. 18, 2012
Nova Scotia, Amegy, KeyBank [Member]
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Dec. 31, 2012
Nova Scotia, Amegy, KeyBank [Member]
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Oct. 19, 2012
Nova Scotia, Amegy, KeyBank [Member]
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Oct. 17, 2012
Nova Scotia, Amegy, KeyBank [Member]
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Mar. 31, 2013
Nova Scotia, Amegy, KeyBank [Member]
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Dec. 31, 2012
Nova Scotia, Amegy, KeyBank [Member]
Interest Expense [Member]
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Dec. 18, 2012
Nova Scotia, Amegy, KeyBank [Member]
Senior Notes [Member]
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Oct. 17, 2012
Nova Scotia, Amegy, KeyBank [Member]
Senior Notes [Member]
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Oct. 09, 2012
Nova Scotia, Amegy, KeyBank [Member]
Senior Notes [Member]
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Dec. 18, 2012
Base Rate Loans [Member]
Nova Scotia, Amegy, KeyBank [Member]
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Oct. 19, 2012
Base Rate Loans [Member]
Nova Scotia, Amegy, KeyBank [Member]
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Oct. 17, 2012
Base Rate Loans [Member]
Nova Scotia, Amegy, KeyBank [Member]
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Dec. 18, 2012
Euro Dollar Loans [Member]
Nova Scotia, Amegy, KeyBank [Member]
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Oct. 19, 2012
Euro Dollar Loans [Member]
Nova Scotia, Amegy, KeyBank [Member]
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Oct. 17, 2012
Euro Dollar Loans [Member]
Nova Scotia, Amegy, KeyBank [Member]
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Dec. 18, 2012
Federal Funds Rate [Member]
Base Rate Loans [Member]
Nova Scotia, Amegy, KeyBank [Member]
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Oct. 17, 2012
Eurodollar [Member]
Nova Scotia, Amegy, KeyBank [Member]
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Dec. 18, 2012
Eurodollar [Member]
Base Rate Loans [Member]
Nova Scotia, Amegy, KeyBank [Member]
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May 01, 2013
Subsequent Event [Member]
Nova Scotia, Amegy, KeyBank [Member]
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Debt Instrument [Line Items] | ||||||||||||||||||||||||||||||||||||||||||||||||
Interest Costs Capitalized | $ 2,629,000 | $ 0 | ||||||||||||||||||||||||||||||||||||||||||||||
Revolving credit facility | 100,000,000 | 350,000,000 | 45,000,000 | |||||||||||||||||||||||||||||||||||||||||||||
Borrowing capacity | 65,000,000 | 50,000,000 | 125,000,000 | 90,000,000 | 155,000,000 | 40,000,000 | 45,000,000 | 50,000,000 | ||||||||||||||||||||||||||||||||||||||||
Line of Credit Facility, Amount Outstanding | 0 | |||||||||||||||||||||||||||||||||||||||||||||||
Amount of current credit facility used to repay former credit facility | 42,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||
Amount of current credit facility used to repay term loan | 2,500,000 | |||||||||||||||||||||||||||||||||||||||||||||||
Applicable rate, minimum | 0.75% | 0.75% | 1.00% | 1.75% | 1.75% | 2.00% | ||||||||||||||||||||||||||||||||||||||||||
Applicable rate, maximum | 1.50% | 1.50% | 1.75% | 2.50% | 2.50% | 2.75% | ||||||||||||||||||||||||||||||||||||||||||
Commitment fee percentage | 0.375% | 0.50% | ||||||||||||||||||||||||||||||||||||||||||||||
Senior unsecured notes issued | 50,000,000 | 250,000,000 | 300,000,000 | |||||||||||||||||||||||||||||||||||||||||||||
Stated interest rate | 7.75% | 7.75% | 5.82% | 7.75% | 7.75% | |||||||||||||||||||||||||||||||||||||||||||
Write-off of deferred loan costs | 1,143,000 | 0 | 55,000 | 1,088,000 | ||||||||||||||||||||||||||||||||||||||||||||
Basis spread | 0.50% | 1.00% | ||||||||||||||||||||||||||||||||||||||||||||||
Debt instrument, description of rate | LIBOR01 | |||||||||||||||||||||||||||||||||||||||||||||||
Interest rate at period end | 2.97% | |||||||||||||||||||||||||||||||||||||||||||||||
Ratio of funded debt to EBITDAX necessary to maintain covenants | 2.00 | |||||||||||||||||||||||||||||||||||||||||||||||
Minimum ratio of EBITDAX to interest expense | 3.00 | |||||||||||||||||||||||||||||||||||||||||||||||
Building Loan Oustandind Amount Of Buidling Loan Refinanced | 302,143,000 | 300,000,000 | 300,000,000 | [1] | 0 | [1] | 2,107,000 | 2,143,000 | [2] | 2,283,000 | [2] | 2,400,000 | ||||||||||||||||||||||||||||||||||||
Loan, periodic payment | 22,000 | 22,000 | ||||||||||||||||||||||||||||||||||||||||||||||
Debt issued | 50,000,000 | 250,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||
Redemption of principal amount plus aggregate net proceeds | 100.00% | 35.00% | ||||||||||||||||||||||||||||||||||||||||||||||
Percentage of notes required to be outstanding for redemption | 65.00% | |||||||||||||||||||||||||||||||||||||||||||||||
Discount price | 101.00% | 98.534% | ||||||||||||||||||||||||||||||||||||||||||||||
Unamortized discount | 3,500,000 | 3,595,000 | 3,665,000 | |||||||||||||||||||||||||||||||||||||||||||||
Effective interest rate | 7.531% | 8.00% | ||||||||||||||||||||||||||||||||||||||||||||||
Unamortized premium | $ 500,000 | $ 490,000 | $ 500,000 | |||||||||||||||||||||||||||||||||||||||||||||
Debt Instrument, Covenant Compliance, Reasonable Transaction Expense Ratio | 2.00 | |||||||||||||||||||||||||||||||||||||||||||||||
Debt Instrument, Covenant Compliance, Earnings Before Income Tax Depreciation Depletion Amortization and Exploration Expenses Ratio | 3.00 | |||||||||||||||||||||||||||||||||||||||||||||||
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