Stock Based Compensation (Details Textual) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stock Based compensation (Textual) [Abstract]
Stock based compensation	$ 8,914	$ 8,462	$ 8,845
Stock based compensation capitalized into oil and gas properties	3,010	2,775	2,901
Exercise price of stock options outstanding, minimum	$ 6.97
Exercise price of stock options outstanding, maximum	$ 53.20
Restricted stocks issued, value	14,100	6,251	5,831
Restricted Stock [Member]
Stock Based compensation (Textual) [Abstract]
Stock based compensation	8,796	8,263	7,624
Vesting period of stock options ,Minimum	P1Y
Vesting period of stock options ,Maximum	P3Y
Restricted stocks issued, shares	597,062	395,869	538,635
Unrecognized compensation cost related to all non-vested share-based compensation	11,541
Weighted average period for expected to be recognized for amortized cost	1.8
Excess tax benefit credited to additional paid-in-capital for net tax benefits	735	(2)	(1,647)
Stock Options [Member]
Stock Based compensation (Textual) [Abstract]
Stock based compensation	$ 118	$ 199	$ 1,221
2009 plan [Member]
Stock Based compensation (Textual) [Abstract]
Vesting period of stock options	5 years
Period after which stock option will expire subsequent to award	10 years
2009 plan [Member] \| Non - Employee Directors [Member]
Stock Based compensation (Textual) [Abstract]
Vesting period of stock options	3 years
Period after which stock option will expire subsequent to award	10 years

Share based compensation arrangement by share based payment award award expiration period.

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- Definition

Stock based compensation capitalized into oil and gas properties.

+ References

No definition available.

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- Definition

Adjustment to additional paid in capital related to the net effect of excess tax benefits and tax deficiencies associated with an equity-based compensation plan other than an employee stock ownership plan (ESOP).

+ References

No definition available.

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- Definition

As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph h

-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.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

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- Definition

The weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, using a decimal to express in number of years.

+ References

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- Definition

Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Number 123R

-Paragraph A240

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- Definition

The maximum vesting term over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition.

+ References

No definition available.

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The minimum vesting term over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition.

+ References

No definition available.

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- Definition

Equity-based compensation cost during the period with respect to the award, which will be recognized in income (as well as the total recognized tax benefit) or capitalized as part of the cost of an asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 50

-Section 50

-Paragraph 1

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-Publisher FASB

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(c)

-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.

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-Topic 718

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- Definition

The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

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- Definition

Aggregate value of stock related to Restricted Stock Awards issued during the period.

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-Topic 505

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30, 31

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