Loans Held for Investment - Schedule of Allowance for Credit Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Losses
Recoveries Collected	$ 15.8	$ 10.2	$ 12.4
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	26.5	80.9	31.1
Provision for Loan, Lease, and Other Losses	26.8	67.8	32.2
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	191.4	204.1	227.7	$ 220.1
Financing Receivable, Allowance for Credit Loss, Writeoff	55.0	114.7	35.9
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses
Financing Receivable, Allowance for Credit Loss, Writeoff	22.0	25.4
Residential Real Estate
Financing Receivable, Allowance for Credit Losses
Financing Receivable, Allowance for Credit Loss, Writeoff	1.4	1.0
Agricultural Real Estate Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses
Financing Receivable, Allowance for Credit Loss, Writeoff	0.2
Real Estate Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses
Recoveries Collected	7.6	1.2	4.7
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	7.8	17.7	35.2
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	131.2	139.4	160.1	138.7
Financing Receivable, Allowance for Credit Loss, Writeoff	23.6	39.6	18.5
Indirect consumer
Financing Receivable, Allowance for Credit Losses
Financing Receivable, Allowance for Credit Loss, Writeoff	9.6	8.5
Other consumer
Financing Receivable, Allowance for Credit Losses
Financing Receivable, Allowance for Credit Loss, Writeoff	4.4	3.9
Credit card consumer
Financing Receivable, Allowance for Credit Losses
Financing Receivable, Allowance for Credit Loss, Writeoff	3.5	3.0
Total consumer loans
Financing Receivable, Allowance for Credit Losses
Recoveries Collected	5.7	4.9	4.7
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	6.2	14.3	(1.0)
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	11.2	16.8	13.0	23.3
Financing Receivable, Allowance for Credit Loss, Writeoff	17.5	15.4	14.0
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses
Recoveries Collected	2.3	3.8	2.6
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	4.6	44.3	(3.9)
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	36.9	38.9	50.2	54.9
Financing Receivable, Allowance for Credit Loss, Writeoff	8.9	59.4	3.4
Agricultural Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses
Recoveries Collected	0.2	0.3	0.4
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	7.9	4.6	0.8
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	12.1	9.0	4.4	$ 3.2
Financing Receivable, Allowance for Credit Loss, Writeoff	$ 5.0	$ 0.3	$ 0.0