Cash-Based Compensation Plans - Narrative (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Compensation Related Costs [Abstract]
Cash based compensation expense	$ 296.2	$ 326.1	$ 326.5

Amount of commitment made to pay deferred cash remuneration.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant