Property, Plant, and Equipment (Tables)

12 Months Ended

Dec. 31, 2014

Property, Plant and Equipment [Abstract]

Summary of Property, Plant and Equipment

Property, plant, and equipment on the Consolidated Balance Sheets is summarized as follows:

	December 31,
(Thousands)	2014			2013
Land	$	7,458		$	8,097
Buildings	129,673			128,187
Machinery and equipment	579,906			569,617
Software	34,525			31,571
Construction in progress	16,818			14,363
Allowances for depreciation	(534,908		)	(510,718		)
Subtotal	233,472			241,117
Capital leases	10,912			10,912
Allowances for depreciation	(1,988		)	(1,728		)
Subtotal	8,924			9,184
Mineral resources	4,980			4,979
Mine development	16,399			15,153
Allowances for amortization and depletion	(16,187		)	(8,540		)
Subtotal	5,192			11,592
Property, plant, and equipment — net	$	247,588		$	261,893