Other Noncurrent Liabilities - Other Noncurrent Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Other Liabilities Disclosure [Abstract]
Operating lease liabilities	$ 19.6	$ 22.2
Reserve for uncertain tax positions	12.4	13.6
Accrued litigation settlement	49.2	60.1
Deferred income	37.1	47.4
Other postretirement benefits	10.1	10.5
Employee benefits	6.0	6.0
Insurance claims and expenses	34.8	11.0
Deferred payment obligation	9.0	9.9
Accrued development costs	7.8	8.3
Other	11.1	8.2
Total	$ 197.1	$ 197.2