Property, Plant and Equipment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Property, Plant, and Equipment
Gross property, plant and equipment	$ 3,849.4		$ 3,849.4		$ 3,007.1
Accumulated depreciation	1,125.9		1,125.9		1,040.0
Total property, plant and equipment, net	2,723.5		2,723.5		1,967.1
Capitalized interest	1.9	$ 0.8	3.4	$ 1.2
Original carrying value of assets under capital lease obligations	24.8		24.8		24.8
Land and improvements
Property, Plant, and Equipment
Gross property, plant and equipment	46.5		46.5		38.6
Buildings
Property, Plant, and Equipment
Gross property, plant and equipment	64.4		64.4		53.6
Machinery and equipment
Property, Plant, and Equipment
Gross property, plant and equipment	3,510.5		3,510.5		2,723.0
Automotive equipment
Property, Plant, and Equipment
Gross property, plant and equipment	24.7		24.7		24.8
Furniture and fixtures
Property, Plant, and Equipment
Gross property, plant and equipment	22.7		22.7		21.3
Leasehold improvements
Property, Plant, and Equipment
Gross property, plant and equipment	3.4		3.4		3.6
Aircraft
Property, Plant, and Equipment
Gross property, plant and equipment	3.6		3.6		3.6
Railcars
Property, Plant, and Equipment
Gross property, plant and equipment	16.7		16.7		16.3
Construction in progress
Property, Plant, and Equipment
Gross property, plant and equipment	$ 156.9		$ 156.9		$ 122.3