Property, Plant, and Equipment - Schedule of Property, Plant, and Equipment (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Total property, plant, and equipment	$ 384.6	$ 361.5
Accumulated depreciation	(284.0)	(259.5)
Property, plant, and equipment, net	100.6	102.0
Land [Member]
Property Plant And Equipment [Line Items]
Total property, plant, and equipment	7.5	7.5
Software [Member]
Property Plant And Equipment [Line Items]
Total property, plant, and equipment	218.5	197.4
Machinery and Equipment [Member]
Property Plant And Equipment [Line Items]
Total property, plant, and equipment	118.8	120.3
Buildings and Improvements [Member]
Property Plant And Equipment [Line Items]
Total property, plant, and equipment	$ 39.8	$ 36.3