Other Noncurrent Liabilities - Other Noncurrent Liabilities (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Other Liabilities Disclosure [Abstract]
Operating lease liabilities	$ 17.6	$ 18.8
Reserve for uncertain tax positions	6.9	6.8
Accrued litigation settlement	49.6	49.4
Deferred income	61.5	58.9
Other postretirement benefits	10.8	10.8
Employee benefits	5.8	6.2
Insurance claims and expenses	42.8	39.3
Deferred payment obligation		1.3
Accrued development costs	24.6	24.6
Other	7.9	7.8
Total	$ 227.5	$ 223.9