Other Assets - Other Assets (Detail) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Other noncurrent assets:
Land held for development	$ 68.5	$ 96.0
Operating lease right-of-use assets	23.3	26.1
Restricted cash and cash equivalents	37.7	37.8
IBNR receivables	32.5	37.1
Marketable securities	3.0	2.9
Pension asset	10.3	8.4
Note receivables - OPA	30.7	25.3
Other	13.7	8.7
Total	$ 219.7	$ 242.3