Fair Value Measurement - Assets Measured at Fair Value on a Nonrecurring Basis (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Goodwill, impairment charge	$ 98.5
Total, impairment charge	99.3	$ 13.9	$ 22.4
Goodwill, net book value	457.8	553.4	588.5
Fair Value, Measurements, Nonrecurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-lived assets, impairment charge	0.6	13.7	1.3
Goodwill, impairment charge	98.5		21.3
Other intangible assets, impairment charge	0.2	0.2	0.2
Total, impairment charge	99.3	$ 13.9	22.8
Goodwill, net book value	53.3
Total Assets, net book value	53.3
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	53.3
Total, fair value measurement	$ 53.3		$ 0.7