Derivatives and Hedging Activities - Notional Amounts and Estimated Fair Values of Derivatives (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Derivative [Line Items]
Derivative Asset, Notional Amount	$ 2,144.7	$ 2,290.7
Derivative Assets, Estimated Fair Value	37.4	45.2
Derivative Liability, Notional Amount	2,295.7	2,449.0
Derivative Liabilities, Estimated Fair Value	127.3	159.6
Derivative Instruments and Hedges, Assets	193.3	191.9
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	6.7	8.1
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Assets, Estimated Fair Value	37.3	45.1
Derivative Liabilities, Estimated Fair Value	127.1	159.6
Derivative Instruments and Hedges, Assets	850.0
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Derivative Assets, Estimated Fair Value	0.1
Forward Contracts [Member]
Derivative [Line Items]
Derivative Assets, Estimated Fair Value		0.1
Derivative Liabilities, Estimated Fair Value	0.1
Not Designated as Hedging Instrument | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Asset, Notional Amount	1,589.0	1,728.1
Derivative Assets, Estimated Fair Value	34.3	41.6
Derivative Liability, Notional Amount	1,589.0	1,728.1
Derivative Liabilities, Estimated Fair Value	121.1	153.9
Not Designated as Hedging Instrument | Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Derivative Asset, Notional Amount	5.7	0.0
Derivative Assets, Estimated Fair Value	0.1	0.0
Derivative Liability, Notional Amount	0.0	14.8
Derivative Liabilities, Estimated Fair Value	0.0	0.0
Not Designated as Hedging Instrument | Forward Contracts [Member]
Derivative [Line Items]
Derivative Asset, Notional Amount	0.0	12.6
Derivative Liability, Notional Amount	5.6	0.0
Derivative Liabilities, Estimated Fair Value	0.1	0.0
Designated as Hedging Instrument | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Asset, Notional Amount	550.0	550.0
Derivative Assets, Estimated Fair Value	3.0	3.5
Derivative Liability, Notional Amount	300.0	300.0
Derivative Liabilities, Estimated Fair Value	$ 2.4	$ 0.3