EMPLOYEE BENEFIT PLANS (Tables)

12 Months Ended

Dec. 31, 2017

Defined Benefit Plan Disclosure [Line Items]

Schedule of Benefit Obligations

The following table sets forth the funded status of the postretirement health care and life insurance benefit plans and their reconciliation with the related amounts in Energen’s consolidated financial statements.

As of December 31, (in thousands)	2017			2016
	Postretirement Benefits
Accumulated benefit obligation
Benefit obligation:
Balance at beginning of period	$	5,447		$	6,488
Service cost	70			94
Interest cost	227			223
Actuarial loss	413			917
Plan amendments	—			(422		)
Curtailment gain	—			(477		)
Benefits paid	(221		)	(1,376		)
Balance at end of period	$	5,936		$	5,447
Plan assets:
Fair value of plan assets at beginning of period	$	9,066		$	10,369
Actual return (loss) on plan assets*	(263		)	73
Benefits paid	(221		)	(1,376		)
Fair value of plan assets at end of period	8,582			9,066
Funded status of plans	$	2,646		$	3,619

Amounts recognized on consolidated balance sheets:
Noncurrent assets recognized	$	2,646		$	3,619
Amounts recognized to accumulated other comprehensive income:
Prior service credit, net of taxes	$	(1,680	)	$	(2,111	)
Net actuarial loss, net of taxes	1,300			643
Total accumulated other comprehensive income	$	(380	)	$	(1,468	)

*Actual loss on plan assets for the year ended December 31, 2017 include $0.9 million for tax payments.

Schedule of Allocation of Plan Assets

The Company’s weighted average plan asset allocations by asset category for postretirement benefit plans were as follows:

As of December 31,	Target		2017		2016
Asset category:
Equity securities	21	%	21	%	26	%
Debt securities	74	%	73	%	74	%
Other	5	%	6	%	—
Total	100	%	100	%	100	%

Schedule of Net Periodic Benefit Cost

The components of net periodic benefit cost were as follows:

Years ended December 31, (in thousands)	2017			2016			2015
Pension Plans
Components of net periodic benefit cost:
Interest cost	$	—		$	—		$	816
Actuarial loss amortization	—			—			737
Settlement charge	—			3,325			29,767
Net periodic expense	$	—		$	3,325		$	31,320
Postretirement Benefit Plans
Components of net periodic benefit cost:
Service cost	$	70		$	94		$	392
Interest cost	227			223			466
Expected long-term return on assets	(249		)	(316		)	(457		)
Prior service cost amortization	(454		)	(465		)	—
Actuarial gain amortization	10			—			—
Settlement charge	—			45			—
Curtailment gain	—			(816		)	—
Net periodic (income) expense	$	(396	)	$	(1,235	)	$	401

Schedule of Other Changes in Plan Assets and Projected Benefit Obligations Recognized in Other Comprehensive Income

Other changes in plan assets and projected benefit obligations recognized in other comprehensive income were as follows:

Years ended December 31, (in thousands)	2017			2016			2015
Pension Plans
Net actuarial gain experienced during the year	$	—		$	—		$	(394	)
Net actuarial loss recognized as expense	—			(3,352		)	(30,478		)
Total recognized in other comprehensive loss	—			(3,352		)	(30,872		)
Postretirement Benefit Plans
Net actuarial (gain) loss experienced during the year	$	925		$	682		$	(645	)
Net actuarial loss recognized as expense	(10		)	(9		)	—
Prior service cost recognized as income	—			780			—
Prior service credit during the year	—			(421		)	(4,071		)
Prior service cost amortization	454			465			—
Total recognized in other comprehensive income (loss)	$	1,369		$	1,497		$	(4,716	)

Schedule of Estimated Amount to be Amortized from Accumulated Other Comprehensive Income

Estimated amounts to be amortized from accumulated other comprehensive income into postretirement benefit cost during 2018 are included in the table below.

(in thousands)
Amortization of prior service credit	$	(454	)
Amortization of net actuarial loss	$	125

Schedule of Weighted Average Rate Assumptions

The weighted average rate assumptions to determine net periodic benefit costs were as follows:

Years ended December 31,	2017		2016		2015
Pension Plans
Discount rate	—		—		0.96	%
Postretirement Benefit Plans
Discount rate	4.30	%	4.37	%	4.25	%
Expected long-term return on plan assets	4.30	%	4.96	%	6.20	%

For the year ended December 31, 2015, the discount rate for the pension plans shown above represents the weighted average for the nonqualified supplemental retirement plan. As the plans were frozen as of December 31, 2014, the rate of compensation increase no longer applies for any of the plans.

The weighted average assumptions used to determine the postretirement benefit obligations at the measurement date were as follows:

Years ended December 31,	2017		2016
Discount rate	3.70	%	4.30	%

Schedule of Expected Benefit Payments

The following benefit payments, which reflect expected future service, as appropriate, are anticipated to be paid as follows:

(in thousands)	Postretirement Benefits
2018	$349
2019	$327
2020	$347
2021	$367
2022	$320
2023-2027	$1,597

Postretirement Benefit Plans

Defined Benefit Plan Disclosure [Line Items]

Schedule of Allocation of Plan Assets

Plan assets included in the funded status of the postretirement benefit plans were as follows:

	December 31, 2017
(in thousands)	Level 1		Level 2		Total
United States equities	$	165	$	—	$	165
Global equities	1,673		—		1,673
Fixed income	6,224		—		6,224
Other	520		—		520
Total	$	8,582	$	—	$	8,582

	December 31, 2016
(in thousands)	Level 1		Level 2		Total
Cash and cash equivalents	$	10	$	—	$	10
United States equities	180		—		180
Global equities	2,158		—		2,158
Fixed income	6,718		—		6,718
Total	$	9,066	$	—	$	9,066