Properties and Equipment (Tables)

6 Months Ended

Jun. 30, 2016

Oil and Gas Property [Abstract]

Property, Plant and Equipment

The following table presents the components of properties and equipment, net of accumulated depreciation, depletion and amortization ("DD&A"):

	June 30, 2016			December 31, 2015
	(in thousands)
Properties and equipment, net:
Crude oil and natural gas properties
Proved	$	3,067,916		$	2,881,189
Unproved	61,202			60,498
Total crude oil and natural gas properties	3,129,118			2,941,687
Equipment and other	31,566			30,098
Land and buildings	9,040			12,667
Construction in progress	117,190			113,115
Properties and equipment, at cost	3,286,914			3,097,567
Accumulated DD&A	(1,356,319		)	(1,157,015		)
Properties and equipment, net	$	1,930,595		$	1,940,552

Impairment of natural gas and crude oil properties

The following table presents impairment charges recorded for crude oil and natural gas properties:

	Three Months Ended June 30,				Six Months Ended June 30,
	2016		2015		2016		2015
	(in thousands)
Impairment of proved and unproved properties	$	1,084	$	1,631	$	2,053	$	1,919
Amortization of individually insignificant unproved properties	54		2,773		86		5,257
Impairment of crude oil and natural gas properties	1,138		4,404		2,139		7,176
Land and buildings	3,032		—		3,032		—
Impairment of properties and equipment	$	4,170	$	4,404	$	5,171	$	7,176