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Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Derivative
Aggregate fair value of all derivative instruments with credit risk-related contingent features in a liability position	$ 49.3		$ 74.0
Derivative, Notional Amount	2,144.0		1,753.9
Approximate amount of net deferred gains on derivative instruments expected to be amortized during the next twelve months	30.9
Component of Derivative Gain (Loss) Excluded from the Assessment of Hedge Effectiveness	2.5	$ 3.3
Discontinued Hedge Accounting Due to Instrument No Longer Qualifying as Fair Value Hedge	0.0	$ 0.0
Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	1,873.3		1,490.7
Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	270.7		263.2
Cash Flow Hedging \| Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	1,282.9		932.9
Interest Rate Swaps \| Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	132.0		132.0
Interest Rate Swaps \| Cash Flow Hedging \| Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	168.9		168.9
Interest Rate Swaps \| Fair Value Hedging \| Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	590.4		557.8
Forwards \| Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	54.4		54.3
Forwards \| Cash Flow Hedging \| Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	1,114.0		764.0
Total Return Swap \| Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	84.3		76.9
Receive Fixed/Pay Fixed \| Interest Rate Swaps \| Not Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	132.0		132.0
Receive Fixed/Pay Fixed \| Interest Rate Swaps \| Cash Flow Hedging \| Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	168.9		168.9
Receive Fixed/Pay Fixed \| Interest Rate Swaps \| Fair Value Hedging \| Designated as Hedging Instrument
Derivative
Derivative, Notional Amount	590.4		557.8
Credit Exposure
Derivative
Credit Exposure on Derivatives	$ 7.9		$ 1.7