Loans Held for Investment - Schedule of Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024	Dec. 31, 2023
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Recoveries Collected	$ 1.8	$ 2.6
Off-Balance Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal)	20.2	8.4
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	215.3	227.7	$ 204.1	$ 227.7
Financing Receivable, Allowance for Credit Loss, Writeoff	10.8	11.0	114.7
Provision for Loan, Lease, and Other Losses	20.0	5.3
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Writeoff			25.4
Agricultural
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Recoveries Collected	0.0	0.3
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	7.1	4.2	9.0	4.4
Financing Receivable, Allowance for Credit Loss, Writeoff	2.9	0.0	0.3
Provision for Loan, Lease, and Other Losses	1.0	(0.5)
Residential
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Writeoff	0.3		1.0
Total real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Recoveries Collected	0.1	0.7
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	146.0	152.9	139.4	160.1
Financing Receivable, Allowance for Credit Loss, Writeoff	0.3	3.2	39.6
Provision for Loan, Lease, and Other Losses	6.8	(4.7)
Indirect consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Writeoff	2.7		8.5
Total consumer loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Recoveries Collected	1.2	1.0
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	15.9	12.6	16.8	13.0
Financing Receivable, Allowance for Credit Loss, Writeoff	4.7	3.8	15.4
Provision for Loan, Lease, and Other Losses	2.6	2.4
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Recoveries Collected	0.5	0.6
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	46.3	58.0	38.9	$ 50.2
Financing Receivable, Allowance for Credit Loss, Writeoff	2.9	4.0	$ 59.4
Provision for Loan, Lease, and Other Losses	$ 9.8	$ 11.2

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

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Amount of expense (reversal of expense) for expected credit loss for off-balance sheet credit exposure. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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