Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2015

Property Plant And Equipment [Abstract]

Schedule of Property, Plant and Equipment

	Useful lives in		December 31,
	years		2015		2014
			(In Thousands)
Machinery, equipment and automotive	3 - 30		$	540,315	$	311,920
Proved natural gas properties	*			76,277		72,529
Buildings and improvements	10 - 30			40,372		34,022
Furniture, fixtures and store equipment	3 - 10			2,409		2,294
Assets under capital leases		3		425		240
Land improvements	10 - 40			7,183		6,875
Construction in progress	N/A			506,205		291,034
Capital spare parts	N/A			18,047		8,722
Land	N/A			8,974		8,974
				1,200,207		736,610
Less accumulated depreciation, depletion and    amortization				221,498		148,486
			$	978,709	$	588,124