Properties and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2016

Property, Plant and Equipment [Abstract]

Components of net property and equipment

Properties and equipment, net are comprised of the following:

	December 31,
(In thousands)	2016			2015
Proved oil and gas properties	$	7,437,604		$	8,821,146
Unproved oil and gas properties	260,543			390,434
Gathering and pipeline systems	187,846			243,672
Land, building and other equipment	84,462			117,848
	7,970,455			9,573,100
Accumulated depreciation, depletion and amortization	(3,720,330		)	(4,596,221		)
	$	4,250,125		$	4,976,879

Schedule of net changes in capitalized exploratory well costs

The following table reflects the net changes in capitalized exploratory well costs:

	Year Ended December 31,
(In thousands)	2016		2015			2014
Balance at beginning of period	$	—	$	10,557		$	—
Additions to capitalized exploratory well costs pending the determination of proved reserves	—					10,557
Reclassifications to wells, facilities, and equipment based on the determination of proved reserves	—		(10,557		)	—
Capitalized exploratory well costs charged to expense	—		—			—
Balance at end of period	$	—	$	—		$	10,557