Allowance for Credit Losses (Details) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2021 USD ($) item	Jun. 30, 2020 USD ($)		Jun. 30, 2021 USD ($) item	Jun. 30, 2020 USD ($)
Allowance for credit losses
Number of classes existing in loan and lease portfolio | item	9			9
Changes in allowance for loan and lease losses
Balance at the beginning of the period	$ 139,550	$ 120,798	[1]	$ 140,654	$ 111,254	[2]
Charge-offs	794	612		5,246	3,450
Recoveries	630	722		1,580	1,751
Net charge-offs (recoveries)	164	(110)		3,666	1,699
Provision (recovery of provision)	(3,025)	10,375	[1]	(627)	21,728	[2]
Balance at the end of the period	136,361	131,283	[1],[2]	136,361	131,283	[1],[2]
Commercial and agricultural
Changes in allowance for loan and lease losses
Balance at the beginning of the period	15,451	20,283	[1]	16,680	20,926	[2]
Charge-offs	285	42		286	571
Recoveries	141	136		518	302
Net charge-offs (recoveries)	144	(94)		(232)	269
Provision (recovery of provision)	(475)	4,682	[1]	(2,080)	4,402	[2]
Balance at the end of the period	14,832	25,059	[1],[2]	14,832	25,059	[1],[2]
Solar
Changes in allowance for loan and lease losses
Balance at the beginning of the period	5,758	2,896	[1]	5,549	2,745	[2]
Charge-offs	0	0		0	0
Recoveries	0	0		0	0
Net charge-offs (recoveries)	0	0		0	0
Provision (recovery of provision)	109	1,052	[1]	318	1,203	[2]
Balance at the end of the period	5,867	3,948	[1],[2]	5,867	3,948	[1],[2]
Auto and light truck
Changes in allowance for loan and lease losses
Balance at the beginning of the period	29,343	15,471	[1]	28,926	14,400	[2]
Charge-offs	367	0		4,653	34
Recoveries	136	58		185	140
Net charge-offs (recoveries)	231	(58)		4,468	(106)
Provision (recovery of provision)	(1,891)	1,842	[1]	2,763	2,865	[2]
Balance at the end of the period	27,221	17,371	[1],[2]	27,221	17,371	[1],[2]
Medium and heavy duty truck
Changes in allowance for loan and lease losses
Balance at the beginning of the period	6,271	4,356	[1]	6,400	4,612	[2]
Charge-offs	0	0		0	0
Recoveries	0	0		0	0
Net charge-offs (recoveries)	0	0		0	0
Provision (recovery of provision)	(383)	293	[1]	(512)	37	[2]
Balance at the end of the period	5,888	4,649	[1],[2]	5,888	4,649	[1],[2]
Aircraft
Changes in allowance for loan and lease losses
Balance at the beginning of the period	35,219	30,069	[1]	34,053	31,058	[2]
Charge-offs	0	254		0	840
Recoveries	241	55		360	503
Net charge-offs (recoveries)	(241)	199		(360)	337
Provision (recovery of provision)	(159)	1,231	[1]	888	380	[2]
Balance at the end of the period	35,301	31,101	[1],[2]	35,301	31,101	[1],[2]
Construction equipment
Changes in allowance for loan and lease losses
Balance at the beginning of the period	16,309	22,693	[1]	19,166	14,120	[2]
Charge-offs	0	129		8	1,561
Recoveries	0	379		254	590
Net charge-offs (recoveries)	0	(250)		(246)	971
Provision (recovery of provision)	1,599	929	[1]	(1,504)	10,723	[2]
Balance at the end of the period	17,908	23,872	[1],[2]	17,908	23,872	[1],[2]
Commercial real estate
Changes in allowance for loan and lease losses
Balance at the beginning of the period	24,334	19,588	[1]	22,758	18,350	[2]
Charge-offs	0	0		0	1
Recoveries	4	13		19	28
Net charge-offs (recoveries)	(4)	(13)		(19)	(27)
Provision (recovery of provision)	(1,760)	335	[1]	(199)	1,559	[2]
Balance at the end of the period	22,578	19,936	[1],[2]	22,578	19,936	[1],[2]
Residential real estate and home equity
Changes in allowance for loan and lease losses
Balance at the beginning of the period	5,163	3,908	[1]	5,374	3,609	[2]
Charge-offs	37	0		42	13
Recoveries	10	3		11	30
Net charge-offs (recoveries)	27	(3)		31	(17)
Provision (recovery of provision)	(70)	(90)	[1]	(277)	195	[2]
Balance at the end of the period	5,066	3,821	[1],[2]	5,066	3,821	[1],[2]
Consumer
Changes in allowance for loan and lease losses
Balance at the beginning of the period	1,702	1,534	[1]	1,748	1,434	[2]
Charge-offs	105	187		257	430
Recoveries	98	78		233	158
Net charge-offs (recoveries)	7	109		24	272
Provision (recovery of provision)	5	101	[1]	(24)	364	[2]
Balance at the end of the period	$ 1,700	$ 1,526	[1],[2]	$ 1,700	$ 1,526	[1],[2]

[1] *ASU 2016-13 adopted during the fourth quarter of 2020 therefore amounts during the second quarter of 2020 reflect the incurred loss method.

[2] *ASU 2016-13 adopted during the fourth quarter of 2020 therefore amounts during the first six months of 2020 reflect the incurred loss method.