Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

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,
(millions of dollars)	2018			2017
Mineral rights and reserves	$	582.8		$	545.9
Land		47.3			44.5
Buildings		219.3			199.6
Machinery and equipment		1,235.6			1,247.5
Furniture and fixtures and other		134.8			132.3
Construction in progress		36.1			49.8
		2,256.0			2,219.6
Less: accumulated depreciation and depletion		(1,153.1	)		(1,158.3	)
Property, plant and equipment, net	$	1,102.9		$	1,061.3