Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2014

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Equipment

	Useful lives in years	December 31,
		2014		2013
		(In Thousands)
Machinery, equipment and automotive	3  - 30	$	360,222	$	319,088
Proved natural gas properties	*		72,529		66,764
Buildings and improvements	8 - 30		55,975		48,379
Furniture, fixtures and store equipment	5 - 10		6,492		6,933
Assets under capital leases	5		240		1,672
Land improvements	10 - 40		7,125		6,214
Construction in progress	N/A		292,324		110,376
Capital spare parts	N/A		8,722		9,718
Land	N/A		9,780		9,780
			813,409		578,924
Less accumulated depreciation, depletion and amortization			194,204		162,123
		$	619,205	$	416,801