LOANS (Past due financing receivables) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 22,132	$ 31,928
Current	9,133,089	8,259,441
Nonaccrual	91,609	76,548
Total	9,246,830	8,367,917
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	17,037	25,322
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	3,735	2,501
90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,360	4,105
Commercial and industrial | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Past Due	4,815	9,924
Current	2,338,143	2,491,110
Nonaccrual	21,442	29,775
Total	2,364,400	2,530,809
Commercial and industrial | Commercial and industrial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	4,587	5,121
Commercial and industrial | Commercial and industrial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	228	904
Commercial and industrial | Commercial and industrial | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	3,899
Commercial and industrial | Paycheck Protection Program ("PPP")
Financing Receivable, Past Due [Line Items]
Total Past Due	0
Current	1,124,430
Nonaccrual	0
Total	1,124,430	0
Commercial and industrial | Paycheck Protection Program ("PPP") | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0
Commercial and industrial | Paycheck Protection Program ("PPP") | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0
Commercial and industrial | Paycheck Protection Program ("PPP") | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0
Commercial and industrial | Owner occupied commercial real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	1,249	4,177
Current	1,406,437	1,461,589
Nonaccrual	25,585	6,938
Total	1,433,271	1,472,704
Commercial and industrial | Owner occupied commercial real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	90	3,487
Commercial and industrial | Owner occupied commercial real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,159	690
Commercial and industrial | Owner occupied commercial real estate | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Commercial and industrial | Non-owner occupied commercial real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	2,934	695
Current	1,536,928	1,493,619
Nonaccrual	3,761	1,563
Total	1,543,623	1,495,877
Commercial and industrial | Non-owner occupied commercial real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,776	614
Commercial and industrial | Non-owner occupied commercial real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	158	81
Commercial and industrial | Non-owner occupied commercial real estate | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Commercial and industrial | Real estate construction
Financing Receivable, Past Due [Line Items]
Total Past Due	2,298	5,761
Current	1,112,172	1,020,153
Nonaccrual	1,373	1,167
Total	1,115,843	1,027,081
Commercial and industrial | Real estate construction | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,298	5,689
Commercial and industrial | Real estate construction | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	72
Commercial and industrial | Real estate construction | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Agricultural and agricultural real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	4,892	3,839
Current	496,541	541,455
Nonaccrual	19,340	20,543
Total	520,773	565,837
Agricultural and agricultural real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	4,209	3,734
Agricultural and agricultural real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	600	79
Agricultural and agricultural real estate | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	83	26
Residential real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	2,932	4,370
Current	717,246	814,840
Nonaccrual	15,584	13,067
Total	735,762	832,277
Residential real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	483	4,166
Residential real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,242	24
Residential real estate | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,207	180
Consumer
Financing Receivable, Past Due [Line Items]
Total Past Due	3,012	3,162
Current	401,192	436,675
Nonaccrual	4,524	3,495
Total	408,728	443,332
Consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,594	2,511
Consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	348	651
Consumer | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 70	$ 0