Allowance for Credit Losses (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) item	Mar. 31, 2023 USD ($)
Allowance for credit losses
Number of classes existing in loan and lease portfolio | item	9
Changes in allowance for loan and lease losses
Balance at the beginning of the period	$ 147,552	$ 139,268
Charge-offs	7,671	1,041
Recoveries	1,548	1,235
Net charge-offs (recoveries)	6,123	(194)
Provision (recovery of provision)	6,595	3,049
Balance at the end of the period	148,024	142,511
Commercial and agricultural
Changes in allowance for loan and lease losses
Balance at the beginning of the period	17,385	14,635
Charge-offs	7,068	564
Recoveries	86	172
Net charge-offs (recoveries)	6,982	392
Provision (recovery of provision)	6,860	1,844
Balance at the end of the period	17,263	16,087
Renewable energy
Changes in allowance for loan and lease losses
Balance at the beginning of the period	6,610	7,217
Charge-offs	0	0
Recoveries	0	0
Net charge-offs (recoveries)	0	0
Provision (recovery of provision)	248	(929)
Balance at the end of the period	6,858	6,288
Auto and light truck
Changes in allowance for loan and lease losses
Balance at the beginning of the period	16,858	18,634
Charge-offs	1	112
Recoveries	653	541
Net charge-offs (recoveries)	(652)	(429)
Provision (recovery of provision)	74	(505)
Balance at the end of the period	17,584	18,558
Medium and heavy duty truck
Changes in allowance for loan and lease losses
Balance at the beginning of the period	8,965	7,566
Charge-offs	0	0
Recoveries	0	0
Net charge-offs (recoveries)	0	0
Provision (recovery of provision)	(177)	263
Balance at the end of the period	8,788	7,829
Aircraft
Changes in allowance for loan and lease losses
Balance at the beginning of the period	37,653	41,093
Charge-offs	68	0
Recoveries	368	226
Net charge-offs (recoveries)	(300)	(226)
Provision (recovery of provision)	(1,029)	(1,186)
Balance at the end of the period	36,924	40,133
Construction equipment
Changes in allowance for loan and lease losses
Balance at the beginning of the period	26,510	24,039
Charge-offs	292	1
Recoveries	199	0
Net charge-offs (recoveries)	93	1
Provision (recovery of provision)	387	1,541
Balance at the end of the period	26,804	25,579
Commercial real estate
Changes in allowance for loan and lease losses
Balance at the beginning of the period	23,690	17,431
Charge-offs	0	39
Recoveries	181	3
Net charge-offs (recoveries)	(181)	36
Provision (recovery of provision)	(27)	1,905
Balance at the end of the period	23,844	19,300
Residential real estate and home equity
Changes in allowance for loan and lease losses
Balance at the beginning of the period	7,698	6,478
Charge-offs	13	1
Recoveries	8	233
Net charge-offs (recoveries)	5	(232)
Provision (recovery of provision)	115	(89)
Balance at the end of the period	7,808	6,621
Consumer
Changes in allowance for loan and lease losses
Balance at the beginning of the period	2,183	2,175
Charge-offs	229	324
Recoveries	53	60
Net charge-offs (recoveries)	176	264
Provision (recovery of provision)	144	205
Balance at the end of the period	$ 2,151	$ 2,116