Allowance for Credit Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Changes in allowance for loan and lease losses
Balance at the beginning of the period	$ 111,254	$ 100,469	$ 94,883
Charge-offs	13,974	7,591	17,112
Recoveries	4,789	2,543	3,236
Net charge-offs (recoveries)	9,185	5,048	13,876
Provision (recovery of provision)	36,001	15,833	19,462
Balance at the end of the period	140,654	111,254	100,469
Cumulative Effect, Period of Adoption, Adjustment [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	2,584
Balance at the end of the period		2,584
Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	113,838
Balance at the end of the period		113,838
Commercial and agricultural
Changes in allowance for loan and lease losses
Balance at the beginning of the period	23,671	17,063	16,228
Charge-offs	903	1,040	229
Recoveries	663	664	222
Net charge-offs (recoveries)	240	376	7
Provision (recovery of provision)	(547)	6,984	842
Balance at the end of the period	22,229	23,671	17,063
Commercial and agricultural | Cumulative Effect, Period of Adoption, Adjustment [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	(655)
Balance at the end of the period		(655)
Commercial and agricultural | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	23,016
Balance at the end of the period		23,016
Auto and light truck
Changes in allowance for loan and lease losses
Balance at the beginning of the period	14,400	14,689	10,103
Charge-offs	7,107	991	3,308
Recoveries	499	97	68
Net charge-offs (recoveries)	6,608	894	3,240
Provision (recovery of provision)	22,437	605	7,826
Balance at the end of the period	28,926	14,400	14,689
Auto and light truck | Cumulative Effect, Period of Adoption, Adjustment [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	(1,303)
Balance at the end of the period		(1,303)
Auto and light truck | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	13,097
Balance at the end of the period		13,097
Medium and heavy duty truck
Changes in allowance for loan and lease losses
Balance at the beginning of the period	4,612	4,303	4,844
Charge-offs	15	1,132	23
Recoveries	18	32	0
Net charge-offs (recoveries)	(3)	1,100	23
Provision (recovery of provision)	(629)	1,409	(518)
Balance at the end of the period	6,400	4,612	4,303
Medium and heavy duty truck | Cumulative Effect, Period of Adoption, Adjustment [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	2,414
Balance at the end of the period		2,414
Medium and heavy duty truck | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	7,026
Balance at the end of the period		7,026
Aircraft
Changes in allowance for loan and lease losses
Balance at the beginning of the period	31,058	33,047	34,619
Charge-offs	855	3,066	12,222
Recoveries	1,800	1,143	2,499
Net charge-offs (recoveries)	(945)	1,923	9,723
Provision (recovery of provision)	1,566	(66)	8,151
Balance at the end of the period	34,053	31,058	33,047
Aircraft | Cumulative Effect, Period of Adoption, Adjustment [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	484
Balance at the end of the period		484
Aircraft | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	31,542
Balance at the end of the period		31,542
Construction equipment
Changes in allowance for loan and lease losses
Balance at the beginning of the period	14,120	10,922	9,343
Charge-offs	4,090	238	288
Recoveries	1,415	160	100
Net charge-offs (recoveries)	2,675	78	188
Provision (recovery of provision)	7,349	3,276	1,767
Balance at the end of the period	19,166	14,120	10,922
Construction equipment | Cumulative Effect, Period of Adoption, Adjustment [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	372
Balance at the end of the period		372
Construction equipment | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	14,492
Balance at the end of the period		14,492
Commercial real estate
Changes in allowance for loan and lease losses
Balance at the beginning of the period	18,350	15,705	14,792
Charge-offs	37	5	70
Recoveries	58	75	53
Net charge-offs (recoveries)	(21)	(70)	17
Provision (recovery of provision)	5,036	2,575	930
Balance at the end of the period	22,758	18,350	15,705
Commercial real estate | Cumulative Effect, Period of Adoption, Adjustment [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	(649)
Balance at the end of the period		(649)
Commercial real estate | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	17,701
Balance at the end of the period		17,701
Residential real estate and home equity
Changes in allowance for loan and lease losses
Balance at the beginning of the period	3,609	3,425	3,666
Charge-offs	74	53	63
Recoveries	33	85	23
Net charge-offs (recoveries)	41	(32)	40
Provision (recovery of provision)	118	152	(201)
Balance at the end of the period	5,374	3,609	3,425
Residential real estate and home equity | Cumulative Effect, Period of Adoption, Adjustment [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	1,688
Balance at the end of the period		1,688
Residential real estate and home equity | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	5,297
Balance at the end of the period		5,297
Consumer
Changes in allowance for loan and lease losses
Balance at the beginning of the period	1,434	1,315	1,288
Charge-offs	893	1,066	909
Recoveries	303	287	271
Net charge-offs (recoveries)	590	779	638
Provision (recovery of provision)	671	898	665
Balance at the end of the period	1,748	1,434	$ 1,315
Consumer | Cumulative Effect, Period of Adoption, Adjustment [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	233
Balance at the end of the period		233
Consumer | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Changes in allowance for loan and lease losses
Balance at the beginning of the period	$ 1,667
Balance at the end of the period		$ 1,667