Common Stock Plans (Other Plans) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock Equivalent Units \| Petrotech Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding, Beginning of Period, Shares	213,870	173,292	141,243
Granted		76,084
Paid, Shares	(78,430)	(4,431)	(36,792)
Forfeited	(22,158)	(31,075)	(26,529)
Outstanding, End of Period, Shares	243,746	213,870	173,292
Share-based compensation expense	$ 3.0	$ 4.5	$ 6.2
Stock Equivalent Units \| Petrotech Incentive Plan \| Three years vesting period
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted	128,519		92,418
Share-based compensation, vesting period	3 years		3 years
Stock Equivalent Units \| Petrotech Incentive Plan \| Two years vesting period
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted	297
Share-based compensation, vesting period	2 years
Stock Equivalent Units \| Petrotech Incentive Plan \| 17-month vesting period
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted			2,952
Share-based compensation, vesting period			17 months
Stock Equivalent Units \| Petrotech Incentive Plan \| 16-month vesting period
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted	1,648
Share-based compensation, vesting period	16 months
Management \| 1997 Deferred Compensation Plan
Deferred Compensation Arrangements [Abstract]
Deferred compensation, reserved for issuance	576,850
Director \| Stock options \| 1992 Energen Corporation Directors Stock Plan
Deferred Compensation Arrangements [Abstract]
Granted, Shares	11,550	10,360	13,500
Number of shares remaining for issuance	116,374

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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The maximum number of shares authorized for issuance under the deferred compensation arrangement as of the balance sheet date.

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Period 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, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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Number of shares under non-option equity instrument agreements for which rights to exercise lapsed.

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Net number of non-option equity instruments granted to participants.

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Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Net number of share options (or share units) granted during the period.

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