Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Apr. 07, 2021
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 158.1	$ 17.1
Finite-Lived Trade Names, Gross	0.4	0.4
Trade Name, Impaired, Accumulated Impairment Loss	0.0	0.0
Finite-Lived Intangible Assets, Accumulated Amortization	15.0	8.9
Indefinite-Lived Trade Names	0.4	0.4
Finite-Lived Intangible Assets, Net	143.1	8.2
Goodwill and intangible assets, net	$ 491.3	289.9		$ 201.4
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	26 years 2 months 12 days
Amortization of Intangible Assets	$ 6.1	1.6	$ 1.6
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	14.6	14.6
Finite-Lived Intangible Assets, Accumulated Amortization	10.2	8.8
Finite-Lived Intangible Assets, Net	4.4	5.8
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	2.5	2.5
Finite-Lived Intangible Assets, Accumulated Amortization	0.6	0.1
Finite-Lived Intangible Assets, Net	1.9	2.4
Correspondent relationships
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	76.0	0.0
Finite-Lived Intangible Assets, Accumulated Amortization	2.8	0.0
Finite-Lived Intangible Assets, Net	73.2	0.0
Trade Names
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	9.5	0.0
Finite-Lived Intangible Assets, Accumulated Amortization	0.4	0.0
Finite-Lived Intangible Assets, Net	9.1	0.0
License
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	55.5	0.0
Finite-Lived Intangible Assets, Accumulated Amortization	1.0	0.0
Finite-Lived Intangible Assets, Net	$ 54.5	$ 0.0