Loans Held for Sale - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Nonaccrual loans	$ 31.6		$ 39.8
Transfer of loans from held-for-sale to held for investment	0.0	$ 19.8
Loans held for sale	59.1		79.9
Transfer of loans to held-for-sale	3.1	$ 12.4
Financing Receivable, Held-for-Sale, Not Part of Disposal Group, after Valuation Allowance	59.1		79.9
Agricultural
Debt Securities, Available-for-sale [Line Items]
Nonaccrual loans	25.2		29.3
Loans held for sale	49.5		62.5
Transfer of loans to held-for-sale	0.0
Proceeds from Collection of Loans Held-for-sale	15.2
Increase (Decrease) in Fair Value Adjustments on Other Assets (Liabilities) Carried at Fair Value under Fair Value Option	2.2
Financing Receivable, Held-for-Sale, Not Part of Disposal Group, after Valuation Allowance	49.5		62.5
Commercial construction
Debt Securities, Available-for-sale [Line Items]
Nonaccrual loans	6.4		10.5
Loans held for sale	6.4		10.5
Transfer of loans to held-for-sale	3.1
Proceeds from Collection of Loans Held-for-sale	0.0
Increase (Decrease) in Fair Value Adjustments on Other Assets (Liabilities) Carried at Fair Value under Fair Value Option	(4.1)
Financing Receivable, Held-for-Sale, Not Part of Disposal Group, after Valuation Allowance	$ 6.4		$ 10.5