Property, Plant and Equipment

12 Months Ended

Dec. 31, 2019

Property Plant And Equipment [Abstract]

Property, Plant and Equipment

4.  Property, Plant and Equipment

	Average	December 31,
	useful lives  (1)	2019		2018
		(In Thousands)
Machinery, equipment and automotive	25	$	1,204,695	$	1,189,438
Buildings and improvements	26		38,810		39,032
Land improvements	34		8,223		8,076
Furniture, fixtures and store equipment	3		1,122		1,122
Construction in progress	N/A		31,575		28,753
Capital spare parts	N/A		24,245		28,945
Land	N/A		4,575		4,583
			1,313,245		1,299,949
Less accumulated depreciation and    amortization			376,771		325,701
		$	936,474	$	974,248

(1) Weighted average useful lives as of December 31, 2019.

4.  Property, Plant and Equipment (continued)

Machinery, equipment and automotive primarily includes the categories of property and equipment and estimated useful lives as follows: processing plants and plant infrastructure (15-30 years); certain processing plant components (3-10 years); and trucks, automobiles, trailers, and other rolling stock (2-7 years).