Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Major categories of property, plant and equipment and accumulated depreciation and depletion

The major categories of property, plant and equipment and accumulated depreciation and depletion are presented below:

	December 31,
	2017			2016
	(millions of dollars)
Mineral rights and reserves	$	545.9		$	547.8
Land		44.5			42.7
Buildings		199.6			195.6
Machinery and equipment		1,247.5			1,193.6
Furniture and fixtures and other		132.3			123.3
Construction in progress		49.8			38.4
		2,219.6			2,141.4
Less: accumulated depreciation and depletion		(1,158.3	)		(1,089.6	)
Property, plant and equipment, net	$	1,061.3		$	1,051.8