Property, Plant and Equipment

The following table sets forth the Company’s property, plant and equipment:



	December 31,
	2018			2017
	(In thousands)
Proved oil and gas properties⁽¹⁾	$	7,878,104		$	7,058,782
Less: Accumulated depreciation, depletion, amortization and impairment	(2,853,353		)	(2,395,153		)
Proved oil and gas properties, net	5,024,751			4,663,629
Unproved oil and gas properties	1,034,085			780,173
Other property and equipment⁽²⁾	1,151,772			868,746
Less: Accumulated depreciation	(183,499		)	(139,062		)
Other property and equipment, net	968,273			729,684
Total property, plant and equipment, net	$	7,027,109		$	6,173,486

__________________


(1)	Included in the Company’s proved oil and gas properties are estimates of future asset retirement costs of $40.5 million and $38.4 million at December 31, 2018 and 2017, respectively.


(2)	Included in the Company’s other property and equipment are estimates of future asset retirement costs of $1.3 million and $1.5 million at December 31, 2018 and 2017, respectively.

Impairment. The Company reviews its proved oil and natural gas properties for impairment whenever events and circumstances indicate that a decline in the recoverability of their carrying value may have occurred. The Company estimates the expected undiscounted future cash flows of its proved oil and natural gas properties by field and then compares such amount to the carrying amount of the proved oil and natural gas properties in the applicable field to determine if the carrying amount is recoverable. If the carrying amount exceeds the estimated undiscounted future cash flows, the Company will adjust the carrying amount of the proved oil and natural gas properties to fair value. The factors used to determine fair value are subject to management’s judgment and expertise and include, but are not limited to, recent sales prices of comparable properties, the present value of future cash flows net of estimated operating and development costs using estimates of proved reserves, future commodity pricing, future production estimates, anticipated capital expenditures and various discount rates commensurate with the risk and current market conditions associated with realizing the expected cash flows projected. These assumptions represent Level 3 inputs, as further discussed under Note 7 — Fair Value Measurements.

As of December 31, 2018, the Company sold certain proved and unproved oil and natural gas properties (see Note 11 – Divestitures). For the year ended December 31, 2018, the Company recorded an impairment loss of $383.4 million, which was included in its exploration and production segment to adjust the carrying amount of these assets, net of the associated ARO liabilities, to their estimated fair value. For the year ended, December 31, 2017, the Company did not record impairment of proved oil and gas properties. As of December 31, 2016, the Company sold certain proved oil and natural gas properties and other midstream properties. For the year ended December 31, 2016, the Company recorded an impairment loss of $3.6 million, of which $2.4 million was included in its midstream services segment and $1.1 million was included in its exploration and production segment, to adjust the carrying amount of these assets, net of the associated ARO liabilities, to their estimated fair value.

In addition, as a result of expiring leases and periodic assessments of unproved properties, the Company recorded non-cash impairment charges on its unproved oil and gas properties of $0.9 million, $6.9 million and $1.1 million for the years ended December 31, 2018, 2017 and 2016, respectively.