LOANS (Past due financing receivables) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	$ 10,177,385	$ 9,954,572
Nonaccrual	64,174	69,369
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	9,435	7,026
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	808	336
90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	246	550
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	10,489	7,912
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	10,102,722	9,877,291
Commercial and industrial | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	2,814,513	2,645,085
Nonaccrual	17,568	18,228
Commercial and industrial | Commercial and industrial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	3,786	1,024
Commercial and industrial | Commercial and industrial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	225	183
Commercial and industrial | Commercial and industrial | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	246	541
Commercial and industrial | Commercial and industrial | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	4,257	1,748
Commercial and industrial | Commercial and industrial | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	2,792,688	2,625,109
Commercial and industrial | Paycheck Protection Program ("PPP")
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	74,065	199,883
Nonaccrual	19	0
Commercial and industrial | Paycheck Protection Program ("PPP") | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	0	0
Commercial and industrial | Paycheck Protection Program ("PPP") | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	0	0
Commercial and industrial | Paycheck Protection Program ("PPP") | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	0	0
Commercial and industrial | Paycheck Protection Program ("PPP") | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	0	0
Commercial and industrial | Paycheck Protection Program ("PPP") | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	74,046	199,883
Commercial and industrial | Owner occupied commercial real estate
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	2,266,076	2,240,334
Nonaccrual	11,492	11,150
Commercial and industrial | Owner occupied commercial real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	517	130
Commercial and industrial | Owner occupied commercial real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	23	0
Commercial and industrial | Owner occupied commercial real estate | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	0	0
Commercial and industrial | Owner occupied commercial real estate | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	540	130
Commercial and industrial | Owner occupied commercial real estate | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	2,254,044	2,229,054
Commercial and industrial | Non-owner occupied commercial real estate
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	2,161,761	2,010,591
Nonaccrual	12,991	13,316
Commercial and industrial | Non-owner occupied commercial real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	1,099	3,929
Commercial and industrial | Non-owner occupied commercial real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	0	0
Commercial and industrial | Non-owner occupied commercial real estate | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	0	0
Commercial and industrial | Non-owner occupied commercial real estate | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	1,099	3,929
Commercial and industrial | Non-owner occupied commercial real estate | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	2,147,671	1,993,346
Commercial and industrial | Real estate construction
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	842,483	856,119
Nonaccrual	2,397	368
Commercial and industrial | Real estate construction | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	332	238
Commercial and industrial | Real estate construction | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	0	50
Commercial and industrial | Real estate construction | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	0	0
Commercial and industrial | Real estate construction | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	332	288
Commercial and industrial | Real estate construction | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	839,754	855,463
Agricultural and agricultural real estate
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	766,443	753,753
Nonaccrual	11,446	15,686
Agricultural and agricultural real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	2,051	687
Agricultural and agricultural real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	282	0
Agricultural and agricultural real estate | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	0	0
Agricultural and agricultural real estate | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	2,333	687
Agricultural and agricultural real estate | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	752,664	737,380
Residential real estate
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	825,242	829,283
Nonaccrual	6,938	9,167
Residential real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	991	767
Residential real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	139	46
Residential real estate | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	0	9
Residential real estate | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	1,130	822
Residential real estate | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	817,174	819,294
Consumer
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	426,802	419,524
Nonaccrual	1,323	1,454
Consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	659	251
Consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	139	57
Consumer | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	0	0
Consumer | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	798	308
Consumer | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Gross loans held to maturity	$ 424,681	$ 417,762