Loans - Allowance for Credit Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 44,436	$ 43,765	$ 44,168
Change in accounting method	(7)
Provision for Credit Losses	19,425	2,775	2,550
Loans Charged-off	(3,572)	(2,901)	(3,791)
Recoveries Collected	902	797	838
Total Ending Allowance Balance	77,694	44,436	43,765
Heartland
Allowance for Credit Losses [Roll Forward]
Change in accounting method	16,503
Provision for Credit Losses	16,200
Excluding Heartland Acquisition
Allowance for Credit Losses [Roll Forward]
Provision for Credit Losses	3,232
Commercial and Industrial Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	7,059	7,921	13,749
Change in accounting method	1,438
Provision for Credit Losses		(694)	(4,190)
Loans Charged-off	(764)	(223)	(1,792)
Recoveries Collected	49	55	154
Total Ending Allowance Balance	19,576	7,059	7,921
Commercial and Industrial Loans | Heartland
Allowance for Credit Losses [Roll Forward]
Change in accounting method	5,246
Provision for Credit Losses	1,797
Commercial and Industrial Loans | Excluding Heartland Acquisition
Allowance for Credit Losses [Roll Forward]
Provision for Credit Losses	4,751
Commercial Real Estate Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	25,818	25,923	21,598
Change in accounting method	(3,271)
Provision for Credit Losses		120	4,305
Loans Charged-off	(26)	(308)	(56)
Recoveries Collected	0	83	76
Total Ending Allowance Balance	40,626	25,818	25,923
Commercial Real Estate Loans | Heartland
Allowance for Credit Losses [Roll Forward]
Change in accounting method	7,675
Provision for Credit Losses	7,522
Commercial Real Estate Loans | Excluding Heartland Acquisition
Allowance for Credit Losses [Roll Forward]
Provision for Credit Losses	2,908
Agricultural Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	4,917	3,837	4,188
Change in accounting method	(1,655)
Provision for Credit Losses		1,086	(324)
Loans Charged-off	0	(8)	(27)
Recoveries Collected	0	2	0
Total Ending Allowance Balance	3,324	4,917	3,837
Agricultural Loans | Heartland
Allowance for Credit Losses [Roll Forward]
Change in accounting method	3,352
Provision for Credit Losses	170
Agricultural Loans | Excluding Heartland Acquisition
Allowance for Credit Losses [Roll Forward]
Provision for Credit Losses	(3,460)
Leases
Allowance for Credit Losses [Roll Forward]
Beginning Balance	397	346	209
Change in accounting method	720
Provision for Credit Losses		51	137
Loans Charged-off	0	0	0
Recoveries Collected	0	0	0
Total Ending Allowance Balance	1,178	397	346
Leases | Heartland
Allowance for Credit Losses [Roll Forward]
Change in accounting method	0
Provision for Credit Losses	0
Leases | Excluding Heartland Acquisition
Allowance for Credit Losses [Roll Forward]
Provision for Credit Losses	61
Consumer Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	727	759	595
Change in accounting method	(284)
Provision for Credit Losses		962	919
Loans Charged-off	(1,667)	(1,511)	(1,309)
Recoveries Collected	510	517	554
Total Ending Allowance Balance	687	727	759
Consumer Loans | Heartland
Allowance for Credit Losses [Roll Forward]
Change in accounting method	20
Provision for Credit Losses	179
Consumer Loans | Excluding Heartland Acquisition
Allowance for Credit Losses [Roll Forward]
Provision for Credit Losses	1,202
Home Equity Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,196	1,834	1,344
Change in accounting method	1,056
Provision for Credit Losses		424	551
Loans Charged-off	(96)	(170)	(94)
Recoveries Collected	19	108	33
Total Ending Allowance Balance	4,065	2,196	1,834
Home Equity Loans | Heartland
Allowance for Credit Losses [Roll Forward]
Change in accounting method	11
Provision for Credit Losses	570
Home Equity Loans | Excluding Heartland Acquisition
Allowance for Credit Losses [Roll Forward]
Provision for Credit Losses	309
Credit Cards
Allowance for Credit Losses [Roll Forward]
Beginning Balance	520	383	257
Change in accounting method	(24)
Provision for Credit Losses		786	563
Loans Charged-off	(905)	(681)	(455)
Recoveries Collected	303	32	18
Total Ending Allowance Balance	600	520	383
Credit Cards | Heartland
Allowance for Credit Losses [Roll Forward]
Change in accounting method	0
Provision for Credit Losses	0
Credit Cards | Excluding Heartland Acquisition
Allowance for Credit Losses [Roll Forward]
Provision for Credit Losses	706
Residential Mortgage Loans
Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,802	2,762	2,228
Change in accounting method	2,013
Provision for Credit Losses		40	589
Loans Charged-off	(114)	0	(58)
Recoveries Collected	21	0	3
Total Ending Allowance Balance	7,638	$ 2,802	$ 2,762
Residential Mortgage Loans | Heartland
Allowance for Credit Losses [Roll Forward]
Change in accounting method	199
Provision for Credit Losses	5,962
Residential Mortgage Loans | Excluding Heartland Acquisition
Allowance for Credit Losses [Roll Forward]
Provision for Credit Losses	$ (3,245)