Other Assets - Other Assets (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Other noncurrent assets:
Land held for development	$ 80.5	$ 96.0
Operating lease right-of-use assets	24.6	26.1
Restricted cash and cash equivalents	37.7	37.8
IBNR receivables	37.7	37.1
Marketable securities	2.8	2.9
Pension asset	8.5	8.4
Note receivables - OPA	30.1	25.3
Other	10.6	8.7
Total	$ 232.5	$ 242.3