Derivatives and Hedging Activities - Schedule of Derivative Instruments, Effect on Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Derivative [Line Items]
Amount of net fee income recognized in other non-interest income
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	0.0		$ 0.0
Derivative Instruments and Hedges, Assets	189.5		189.5		$ 695.6
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	(10.5)		(10.5)		(4.4)
Financial Instruments	0.0		0.0		0.0
Derivative Asset, Notional Amount	2,021.9		2,021.9		1,691.2
Derivative Asset, Estimated Fair Value	24.8		24.8		28.1
Derivative Liability, Notional Amount	1,867.2		1,867.2		1,103.9
Derivative Liabilities, Estimated Fair Value					18.2
two-year forward starting, three-year pay fixed interest rate swap
Derivative [Line Items]
Derivative Instruments and Hedges, Assets	500.0		500.0
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	23.3		23.3
Collateral Pledged
Derivative [Line Items]
Derivative, Fair Value, Net	0.0		0.0
Not Designated as Hedging Instrument
Derivative [Line Items]
Amount of net fee income recognized in other non-interest income	1.1	$ 0.1	3.1	$ 1.2
Amount of net gains recognized in mortgage banking revenues	1.0	0.2	1.5	0.5
Interest Rate Swap
Derivative [Line Items]
Financial Instruments	0.0		0.0		0.0
Derivative Asset, Notional Amount	0.0		0.0		87.6
Derivative Asset, Estimated Fair Value	0.0		0.0		0.1
Interest Rate Swap | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Notional Amount	200.0		200.0		700.0
Derivative Asset, Estimated Fair Value	10.3		10.3		4.1
Interest Rate Swap | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Notional Amount	1,758.7		1,758.7		913.9
Derivative Asset, Estimated Fair Value	14.3		14.3		22.2
Derivative Liability, Notional Amount	1,758.7		1,758.7		913.9
Derivative Liabilities, Estimated Fair Value	99.2		99.2		18.1
Risk Participation Agreements
Derivative [Line Items]
Financial Instruments	0.0		0.0
Risk Participation Agreements | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Liability, Notional Amount	108.5		108.5		0.0
Derivative Liabilities, Estimated Fair Value	0.2		0.2		0.0
Forward Contracts | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Fair Value, Net	0.0		0.0		0.0
Derivative Asset, Notional Amount	34.6		34.6		0.0
Derivative Liability, Notional Amount	0.0		0.0		102.4
Derivative Liabilities, Estimated Fair Value	0.0		0.0		$ 0.0
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	$ 0.0	$ 0.0	$ 0.0	$ 0.0