CONCENTRATION OF RISK Accounts Receivable, net of Allowance for Doubtful Accounts (Tables)

12 Months Ended

Dec. 31, 2017

Concentration Risks, Types, No Concentration Percentage [Abstract]

Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Current [Text Block]

Other Accrued Expenses. The following table presents the components of other accrued expenses:

	As of December 31,
	2017		2016
	(in thousands)
Employee benefits	$	22,383	$	22,282
Asset retirement obligations	15,801		9,775
Environmental expenses	1,374		3,238
Other	3,429		3,330
Other accrued expenses	$	42,987	$	38,625

Accounts Receivable [Table Text Block]

Accounts Receivable. The following table presents the components of accounts receivable, net of allowance for doubtful accounts:

	As of December 31,
	2017			2016
	(in thousands)
Crude oil, natural gas, and NGLs sales	$	154,260		$	97,520
Joint interest billings (1)	34,576			20,118
Derivative counterparties	(18		)	10,266
Income tax receivable	6,015			11,505
Other	5,893			6,173
Allowance for doubtful accounts	(3,128		)	(2,190		)
Accounts receivable, net	$	197,598		$	143,392

_________

(1) The December 31, 2017 amount includes $13.9 million of pre-closing contracted completion costs of wells associated

with the Bayswater Acquisition, which closed in January 2018. Upon closing, the $13.9 million was capitalized and

included in properties and equipment, net on the consolidated balance sheet.

Individual Customers Constituting 10% or more of Total Revenue [Table Text Block]

Major Customers. The following table presents the individual customers constituting 10 percent or more of total revenues:

	Year Ended December 31,
Customer	2017		2016		2015
DCP Midstream, LP	19.6	%	20.2	%	13.2	%
Suncor Energy Marketing, Inc.	16.4	%	22.3	%	14.3	%
Aka Energy Group, LLC	—	%	13.4	%	—	%
Concord Energy, LLC	—	%	13.4	%	23.2	%
Bridger Energy, LLC	—	%	11.5	%	—	%
Shell Trading Company	—	%	—	%	13.8	%