Properties and Equipment, Net

12 Months Ended

Dec. 31, 2016

Property, Plant and Equipment [Abstract]

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

Impairment

In December 2016, the Company recorded an impairment of $435.6 million associated with oil and gas properties and related pipeline assets located in West Virginia and Virginia. The impairment of these properties and the related pipeline assets was due to the carrying value of these assets exceeding the expected undiscounted cash flows of the underlying assets. These assets were reduced to fair value of approximately $89.2 million.

In December 2015, the Company recorded an impairment of $114.9 million associated with oil and gas properties in certain non-core fields in south Texas, east Texas and Louisiana. The impairment of these fields was due to a significant decline in commodity prices in late 2015. These fields were reduced to fair value of approximately $89.9 million using discounted future cash flows.

In December 2014, the Company recorded a $771.0 million impairment of oil and gas properties in certain non-core fields, primarily in east Texas. The impairment of these fields was due to a significant decline in commodity prices in late 2014 and management's decision not to pursue any further activity in these non-core areas in the current price environment. These fields were reduced to fair value of approximately $86.5 million using discounted future cash flows.

The fair value of the impaired properties was based on significant inputs that were not observable in the market and are considered to be Level 3 inputs as defined by ASC 820. Refer to Note 1 for a description of fair value hierarchy. Key assumptions included (i) reserves, including risk adjustments for probable and possible reserves; (ii) production rates based on the Company's experience with similar properties in which it operates; (iii) estimated future operating and development costs; (iv) future commodity prices; (v) future cash flows; and (vi) a market-based weighted average cost of capital rate of 10%.

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

As of December 31, 2014, capitalized exploratory well costs of $10.6 million had been capitalized for a period of one year or less. There were no capitalized exploratory well costs as of December 31, 2016 and 2015.