Properties and Equipment (Tables)

3 Months Ended

Mar. 31, 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"):

	March 31, 2016			December 31, 2015
	(in thousands)
Properties and equipment, net:
Crude oil and natural gas properties
Proved	$	2,954,843		$	2,881,189
Unproved	60,806			60,498
Total crude oil and natural gas properties	3,015,649			2,941,687
Equipment and other	31,222			30,098
Land and buildings	12,111			9,015
Construction in progress	135,396			113,115
Properties and equipment, at cost	3,194,378			3,093,915
Accumulated DD&A	(1,251,880		)	(1,156,237		)
Properties and equipment, net	$	1,942,498		$	1,937,678

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 March 31,
	2016		2015
	(in thousands)
Impairment of proved properties	$	969	$	293
Amortization of individually insignificant unproved properties	32		2,479
Impairment of crude oil and natural gas properties	$	1,001	$	2,772