Income Taxes - Reconciliations of Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 37.3	$ 46.3	$ 47.4
Gross increases for tax positions in prior periods	3.6	2.5	0.6
Gross decreases for tax positions in prior periods	(0.9)	(0.7)	0.0
Gross increases based on tax positions related to the current year	0.2	0.2	0.2
Gross decreases related to settlements with taxing authorities	(0.6)	(0.9)	(1.1)
Reductions due to statute expiration	0.0	(10.1)	(0.8)
Ending balance	39.6	37.3	$ 46.3
Employee compensation and benefits	$ 26.5	$ 18.2

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from employee compensation.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of unrecognized tax benefits.

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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