Loans Held for Investment - Schedule of Modifications to Borrowers (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Financing Receivable, Modifications to Borrowers [Line Items]
Accrued interest receivable	$ 102.6	$ 116.8
Financing Receivable, Modified in Period, Accrued Interest, Amount	1.4	0.2	$ 1.6
Accruing 30 or more DPD
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	18.9	0.0
Nonaccrual 30 or more DPD
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	7.7	7.8
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 30.0	$ 26.4	$ 31.8
Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage	0.37%	0.28%	0.36%
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification	0.00%	0.00%	0.35%
Financing Receivable, Modified, Weighted Average Term Increase from Modification	9 years 3 months 18 days	8 years 7 months 6 days	5 years 9 months 18 days
Commercial Real Estate Portfolio Segment [Member] | Extension of terms or maturity
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 28.5	$ 26.4	$ 28.6
Commercial Real Estate Portfolio Segment [Member] | Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	1.5	0.0	0.6
Commercial Real Estate Portfolio Segment [Member] | Principal Forgiveness
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 1.5
Commercial Real Estate Portfolio Segment [Member] | Weighted-Average Months of Term Extension
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction	10 years 8 months 12 days	0 years	6 years
Commercial Real Estate Portfolio Segment [Member] | Principal Forgiven
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 1.3
Commercial Real Estate Portfolio Segment [Member] | Weighted-Average Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction Percent	1.00%	0.00%	0.30%
Commercial Real Estate Portfolio Segment [Member] | Interest rate adjustment
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 1.1
Real Estate Construction Financing Receivable [Member]
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 1.9	$ 1.9	$ 13.7
Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage	0.23%	0.15%	0.75%
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification	0.00%	0.00%	0.00%
Financing Receivable, Modified, Weighted Average Term Increase from Modification	7 years 4 months 24 days	4 years	9 years 1 month 6 days
Real Estate Construction Financing Receivable [Member] | Extension of terms or maturity
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 1.9	$ 1.9	$ 13.7
Real Estate Construction Financing Receivable [Member] | Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.0	0.0	0.0
Real Estate Construction Financing Receivable [Member] | Principal Forgiveness
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Real Estate Construction Financing Receivable [Member] | Weighted-Average Months of Term Extension
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction	0 years	0 years	0 years
Real Estate Construction Financing Receivable [Member] | Principal Forgiven
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Real Estate Construction Financing Receivable [Member] | Weighted-Average Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction Percent	0.00%	0.00%	0.00%
Real Estate Construction Financing Receivable [Member] | Interest rate adjustment
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Residential Real Estate
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.4	$ 0.3	$ 0.7
Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage	0.02%	0.01%	0.03%
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification	0.00%	0.00%	0.00%
Financing Receivable, Modified, Weighted Average Term Increase from Modification	22 years 3 months 18 days	0 years	131 years 7 months 6 days
Residential Real Estate | Extension of terms or maturity
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.3	$ 0.0	$ 0.6
Residential Real Estate | Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.1	0.3	0.0
Residential Real Estate | Principal Forgiveness
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.1
Residential Real Estate | Weighted-Average Months of Term Extension
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction	84 years 9 months 18 days	31 years 2 months 12 days	0 years
Residential Real Estate | Principal Forgiven
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.3
Residential Real Estate | Weighted-Average Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction Percent	2.20%	3.40%	0.00%
Residential Real Estate | Interest rate adjustment
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Agricultural Real Estate Financing Receivable [Member]
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 14.4	$ 12.0	$ 6.4
Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage	2.29%	1.71%	0.89%
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification	0.00%	0.00%	0.00%
Financing Receivable, Modified, Weighted Average Term Increase from Modification	12 years 8 months 12 days	10 years 4 months 24 days	4 years 6 months
Agricultural Real Estate Financing Receivable [Member] | Extension of terms or maturity
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 11.6	$ 12.0	$ 6.4
Agricultural Real Estate Financing Receivable [Member] | Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	2.8	0.0	0.0
Agricultural Real Estate Financing Receivable [Member] | Principal Forgiveness
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Agricultural Real Estate Financing Receivable [Member] | Weighted-Average Months of Term Extension
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction	4 years	0 years	0 years
Agricultural Real Estate Financing Receivable [Member] | Principal Forgiven
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Agricultural Real Estate Financing Receivable [Member] | Weighted-Average Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction Percent	0.30%	0.00%	0.00%
Agricultural Real Estate Financing Receivable [Member] | Interest rate adjustment
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Real Estate Financing Receivable [Member]
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 46.7	$ 40.6	$ 52.6
Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage	0.40%	0.30%	0.39%
Real Estate Financing Receivable [Member] | Extension of terms or maturity
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 42.3	$ 40.3	$ 49.3
Real Estate Financing Receivable [Member] | Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	4.4	0.3	0.6
Real Estate Financing Receivable [Member] | Principal Forgiveness
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.0	0.0	1.6
Real Estate Financing Receivable [Member] | Principal Forgiven
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.0	0.0	1.6
Real Estate Financing Receivable [Member] | Interest rate adjustment
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.0	0.0	1.1
Indirect consumer
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.1	$ 0.1	$ 0.1
Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage	0.02%	0.01%	0.01%
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification	0.00%	0.00%	0.00%
Financing Receivable, Modified, Weighted Average Term Increase from Modification	10 years 6 months	7 years	8 years 3 months 18 days
Indirect consumer | Extension of terms or maturity
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.1	$ 0.1	$ 0.1
Indirect consumer | Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.0	0.0	0.0
Indirect consumer | Principal Forgiveness
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Indirect consumer | Weighted-Average Months of Term Extension
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction	0 years	0 years	0 years
Indirect consumer | Principal Forgiven
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Indirect consumer | Weighted-Average Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction Percent	0.00%	0.00%	0.00%
Indirect consumer | Interest rate adjustment
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Other consumer
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount			$ 0.1
Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage			0.07%
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification			0.00%
Financing Receivable, Modified, Weighted Average Term Increase from Modification			62 years 1 month 6 days
Other consumer | Extension of terms or maturity
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount			$ 0.1
Other consumer | Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount			0.0
Other consumer | Principal Forgiveness
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount			$ 0.0
Other consumer | Weighted-Average Months of Term Extension
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction			0 years
Other consumer | Principal Forgiven
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount			$ 0.0
Other consumer | Weighted-Average Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction Percent			0.00%
Other consumer | Interest rate adjustment
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount			$ 0.0
Total consumer loans
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.1	$ 0.1	$ 0.2
Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage	0.02%	0.01%	0.02%
Total consumer loans | Extension of terms or maturity
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.1	$ 0.1	$ 0.2
Total consumer loans | Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.0	0.0	0.0
Total consumer loans | Principal Forgiveness
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.0	0.0	0.0
Total consumer loans | Principal Forgiven
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.0	0.0	0.0
Total consumer loans | Interest rate adjustment
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.0	0.0	0.0
Commercial Portfolio Segment [Member]
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 34.6	$ 9.5	$ 7.6
Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage	1.47%	0.34%	0.26%
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification	0.00%	0.00%	0.00%
Financing Receivable, Modified, Weighted Average Term Increase from Modification	7 years 8 months 12 days	20 years 2 months 12 days	12 years 2 months 12 days
Commercial Portfolio Segment [Member] | Extension of terms or maturity
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 34.2	$ 8.9	$ 7.4
Commercial Portfolio Segment [Member] | Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.4	0.6	0.2
Commercial Portfolio Segment [Member] | Principal Forgiveness
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Commercial Portfolio Segment [Member] | Weighted-Average Months of Term Extension
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction	71 years 9 months 18 days	10 years	14 years 7 months 6 days
Commercial Portfolio Segment [Member] | Principal Forgiven
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Commercial Portfolio Segment [Member] | Weighted-Average Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction Percent	1.40%	1.00%	0.50%
Commercial Portfolio Segment [Member] | Interest rate adjustment
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Agricultural Financing Receivable [Member]
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 9.2	$ 20.1	$ 36.1
Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage	1.77%	2.92%	4.69%
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification	0.00%	0.00%	0.00%
Financing Receivable, Modified, Weighted Average Term Increase from Modification	7 years 1 month 6 days	9 years 4 months 24 days	9 years 2 months 12 days
Agricultural Financing Receivable [Member] | Extension of terms or maturity
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 9.2	$ 20.1	$ 36.1
Agricultural Financing Receivable [Member] | Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.0	0.0	0.0
Agricultural Financing Receivable [Member] | Principal Forgiveness
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Agricultural Financing Receivable [Member] | Weighted-Average Months of Term Extension
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction	7 years 10 months 24 days	0 years	0 years
Agricultural Financing Receivable [Member] | Principal Forgiven
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Agricultural Financing Receivable [Member] | Weighted-Average Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Combination Term Extension and Interest Rate Reduction Percent	1.00%	0.00%	0.00%
Agricultural Financing Receivable [Member] | Interest rate adjustment
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 0.0
Loans held for investment
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 90.6	$ 70.3	$ 96.5
Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage	0.60%	0.39%	0.53%
Loans held for investment | Extension of terms or maturity
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 85.8	$ 69.4	$ 93.0
Loans held for investment | Extended Maturity and Interest Rate Reduction
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	4.8	0.9	0.8
Loans held for investment | Principal Forgiveness
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.0	0.0	1.6
Loans held for investment | Principal Forgiven
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0.0	0.0	1.6
Loans held for investment | Interest rate adjustment
Financing Receivable, Modifications to Borrowers [Line Items]
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	$ 0.0	$ 0.0	$ 1.1