Reconciliation of Asset Retirement Obligation Liability (Tables)

12 Months Ended

Dec. 31, 2017

Asset Retirement Obligation [Abstract]

Schedule of change in asset retirement obligation liability [Table Text Block]

A reconciliation of the Company’s total asset retirement obligation liability is as follows:

	As of December 31,
	2017			2016
	(in thousands)
Beginning asset retirement obligations	$	123,307		$	140,874
Liabilities incurred (1)	7,588			21,293
Liabilities settled (2)	(30,432		)	(57,100		)
Accretion expense	5,988			7,795
Revision to estimated cash flows	8,019			10,445
Ending asset retirement obligations (3)(4)	$	114,470		$	123,307

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⁽¹⁾  Reflects liabilities incurred through drilling activities and acquisitions of drilled wells.

⁽²⁾  Reflects liabilities settled through plugging and abandonment activities and divestitures of properties.

⁽³⁾  Balances as of December 31, 2017, and 2016, included $11.4 million and $26.2 million, respectively, of asset retirement obligations associated with oil and gas properties held for sale.

⁽⁴⁾  Balances as of December 31, 2017, and 2016, included $75,000 and $932,000, respectively, related to the Company’s current asset retirement obligation liability, which is recorded in accounts payable and accrued expenses on the accompanying balance sheets.