Fair Value Measurement - Assets Measured at Fair Value on a Nonrecurring Basis (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Goodwill, impairment charge		$ 21.3
Total, impairment charge	$ 13.9	22.4	$ 558.3
Goodwill, net book value	553.4	588.5	602.0
Fair Value, Measurements, Nonrecurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-lived assets, impairment charge	13.7	1.3	0.6
Goodwill, impairment charge		21.3	527.8
Other intangible assets, impairment charge	0.2	0.2	29.7
Total, impairment charge	$ 13.9	22.8	558.1
Goodwill, net book value			15.2
Other intangible assets, net book value			4.3
Total Assets, net book value			19.5
Fair Value, Measurements, Nonrecurring | Fair Value, Inputs, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-lived assets, fair value measurement		0.7
Goodwill, fair value measurement			15.2
Other intangible assets, fair value measurement			4.6
Total, fair value measurement		$ 0.7	$ 19.8