Other Current and Non-Current Liabilities - Schedule of Other Non-Current Liabilities (Detail) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Other Liabilities Noncurrent [Abstract]
Deferred consideration payable from acquisitions	$ 25.0	$ 24.4
Uncertain tax positions, including interest and penalties	24.9	24.8
Contingent consideration obligation		213.6
Accrued payables from acquisitions		136.0
Other non-current liabilities	2.4	2.3
Total other non-current liabilities	$ 52.3	$ 401.1