Derivatives and Hedging Activities - Schedule of Derivative Instruments, Effect on Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Derivative [Line Items]
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	$ 15.0		$ 15.0
Derivative Instruments and Hedges, Assets	192.9		192.9		$ 191.9
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	7.1		7.1		8.1
Financial Instruments	0.0		0.0		0.0
Derivative Asset, Notional Amount	1,646.8		1,646.8		2,290.7
Derivative Asset, Estimated Fair Value	57.4		57.4		45.2
Derivative Liability, Notional Amount	2,898.0		2,898.0		2,449.0
Derivative Liabilities, Estimated Fair Value	210.0		210.0		159.6
Collateral Pledged
Derivative [Line Items]
Derivative, Fair Value, Net	0.9		0.9
Financial Instruments	0.1		0.1
Not Designated as Hedging Instrument
Derivative [Line Items]
Amount of net fee income recognized in other non-interest income	0.1	$ 2.5	0.7	$ 5.6
Amount of net gains recognized in mortgage banking revenues	0.1	(0.2)	(0.1)	(1.7)
Interest Rate Swap
Derivative [Line Items]
Derivative Instruments and Hedges, Assets	850.0		850.0
Financial Instruments	0.0		0.0		0.0
Interest Rate Swap | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Notional Amount	0.0		0.0		550.0
Derivative Asset, Estimated Fair Value	0.0		0.0		3.5
Derivative Liability, Notional Amount	850.0		850.0		300.0
Derivative Liabilities, Estimated Fair Value	18.6		18.6		0.3
Interest Rate Swap | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Notional Amount	1,638.8		1,638.8		1,728.1
Derivative Asset, Estimated Fair Value	57.4		57.4		41.6
Derivative Liability, Notional Amount	1,638.8		1,638.8		1,728.1
Derivative Liabilities, Estimated Fair Value	184.1		184.1		153.9
Risk Participation Agreements | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Liability, Notional Amount	102.2		102.2		106.1
Derivative Liabilities, Estimated Fair Value	0.0		0.0		0.0
Forward Contracts | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Fair Value, Net	0.0		0.0		0.1
Derivative Asset, Notional Amount	8.0		8.0		12.6
Interest Rate Lock Commitments | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Liability, Notional Amount	7.0		7.0		14.8
Derivative Liabilities, Estimated Fair Value	0.0		0.0		0.0
Interest Rate Collars
Derivative [Line Items]
Derivative Instruments and Hedges, Assets	300.0		300.0
Interest Rate Collars | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	300.0		300.0		300.0
Derivative Liabilities, Estimated Fair Value	7.3		7.3		$ 5.4
Cash Flow Hedging [Member] | Interest Rate Swap | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	$ (25.1)	$ (5.6)	$ (31.2)	$ (5.6)