Income Taxes Income Taxes - Cumulative Tax Effects of Primary Differences (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Deferred Tax Liabilities, Property, Plant and Equipment	$ 0.0	$ 7.6
Deferred Tax Liabilities, Deferred Expense, Reserves and Accruals	(7.6)	(17.5)
Deferred Tax Liabilities, Insurance Premiums	(6.0)	0.0
Deferred Tax Liabilities, Tax Deferred Income	(7.7)	(9.8)
Deferred Tax Liabilities, Mortgage Servicing Rights	(57.6)	0.0
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	5.1	2.1
Deferred Tax Assets, Net of Valuation Allowance	183.4	165.7
Deferred Tax Liabilities, Leasing Arrangements	(36.0)	(19.2)
Deferred Tax Liabilities, Tax Deferred Income	(5.7)	(31.2)
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Provision for Loan Losses	81.0	84.6
Deferred Tax Assets, Leasing Arrangements	38.6	21.1
Deferred Tax Assets, Other	34.9	29.1
Deferred Tax Assets, Gross	183.4	165.7
Deferred Tax Liabilities, Deferred Expense, Deferred Financing Costs	(15.5)	(12.8)
Deferred Tax Liabilities, Unearned Premiums	(7.2)	(16.8)
Deferred Tax Liabilities, Leasing Basis Differences	(12.3)	(11.1)
Deferred Tax Liabilities, Other	(6.9)	(8.4)
Deferred Tax Liabilities, Gross	(162.5)	(134.4)
Deferred tax assets, net	20.9	31.3
Deferred Tax Assets, Valuation Allowance	0.0	0.0
Deferred Tax Assets, Insurance Premiums	0.0	18.9
Deferred Tax Assets, Passthrough Income	9.1	8.4
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities	9.8	3.6
Deferred Tax Assets, Property, Plant and Equipment	$ 10.0	$ 0.0