Loans - Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 77,694	$ 44,436	$ 44,436
Change in Accounting Method		(7)
2/1/2025 Acquired Heartland PCD		15,908
Day 2 CECL Provision - Heartland		16,200
Provision (Benefit) for Credit Loss Expense	2,000	15,300
Provision (Benefit) for Credit Loss Expense		(893)
Loans Charged-off	(1,468)	(625)
Recoveries Collected	321	139
Total Ending Allowance Balance	78,547	75,158	77,694
Commercial and Industrial Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	19,576	7,059	7,059
Change in Accounting Method		1,438
2/1/2025 Acquired Heartland PCD		5,246
Day 2 CECL Provision - Heartland		1,797
Provision (Benefit) for Credit Loss Expense	(414)
Provision (Benefit) for Credit Loss Expense		(75)
Loans Charged-off	(488)	(126)	(764)
Recoveries Collected	2	4
Total Ending Allowance Balance	18,676	15,343	19,576
Commercial Real Estate Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	40,626	25,818	25,818
Change in Accounting Method		(3,271)
2/1/2025 Acquired Heartland PCD		7,080
Day 2 CECL Provision - Heartland		7,522
Provision (Benefit) for Credit Loss Expense	1,487
Provision (Benefit) for Credit Loss Expense		662
Loans Charged-off	0	0	(26)
Recoveries Collected	37	0
Total Ending Allowance Balance	42,150	37,811	40,626
Agricultural Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	3,324	4,917	4,917
Change in Accounting Method		(1,655)
2/1/2025 Acquired Heartland PCD		3,352
Day 2 CECL Provision - Heartland		170
Provision (Benefit) for Credit Loss Expense	(80)
Provision (Benefit) for Credit Loss Expense		(1,478)
Loans Charged-off	0	0	(8)
Recoveries Collected	0	0
Total Ending Allowance Balance	3,244	5,306	3,324
Leases
Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,178	397	397
Change in Accounting Method		720
2/1/2025 Acquired Heartland PCD		0
Day 2 CECL Provision - Heartland		0
Provision (Benefit) for Credit Loss Expense	142
Provision (Benefit) for Credit Loss Expense		34
Loans Charged-off	(149)	0	0
Recoveries Collected	0	0
Total Ending Allowance Balance	1,171	1,151	1,178
Consumer Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	687	727	727
Change in Accounting Method		(284)
2/1/2025 Acquired Heartland PCD		20
Day 2 CECL Provision - Heartland		179
Provision (Benefit) for Credit Loss Expense	186
Provision (Benefit) for Credit Loss Expense		227
Loans Charged-off	(395)	(325)	(1,667)
Recoveries Collected	177	113
Total Ending Allowance Balance	655	657	687
Home Equity Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	4,065	2,196	2,196
Change in Accounting Method		1,056
2/1/2025 Acquired Heartland PCD		11
Day 2 CECL Provision - Heartland		570
Provision (Benefit) for Credit Loss Expense	222
Provision (Benefit) for Credit Loss Expense		108
Loans Charged-off	0	0	(96)
Recoveries Collected	4	1
Total Ending Allowance Balance	4,291	3,942	4,065
Credit Cards
Allowance for Credit Losses [Roll Forward]
Beginning Balance	600	520	520
Change in Accounting Method		(24)
2/1/2025 Acquired Heartland PCD		0
Day 2 CECL Provision - Heartland		0
Provision (Benefit) for Credit Loss Expense	201
Provision (Benefit) for Credit Loss Expense		265
Loans Charged-off	(326)	(174)
Recoveries Collected	101	21
Total Ending Allowance Balance	576	608	600
Residential Mortgage Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	7,638	2,802	2,802
Change in Accounting Method		2,013
2/1/2025 Acquired Heartland PCD		199
Day 2 CECL Provision - Heartland		5,962
Provision (Benefit) for Credit Loss Expense	256
Provision (Benefit) for Credit Loss Expense		(636)
Loans Charged-off	(110)	0	(114)
Recoveries Collected	0	0
Total Ending Allowance Balance	$ 7,784	$ 10,340	$ 7,638