LOANS (Past due financing receivables) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 31,648	$ 31,928
Current	8,263,308	8,259,441
Nonaccrual	79,280	76,548
Total	8,374,236	8,367,917
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	21,693	25,322
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	9,955	2,501
90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	4,105
Commercial and industrial | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Past Due	5,846	9,924
Current	2,517,637	2,491,110
Nonaccrual	27,007	29,775
Total	2,550,490	2,530,809
Commercial and industrial | Commercial and industrial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	5,346	5,121
Commercial and industrial | Commercial and industrial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	500	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 | Owner occupied commercial real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	2,490	4,177
Current	1,419,112	1,461,589
Nonaccrual	9,436	6,938
Total	1,431,038	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	1,462	3,487
Commercial and industrial | Owner occupied commercial real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,028	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	9,890	695
Current	1,540,269	1,493,619
Nonaccrual	1,628	1,563
Total	1,551,787	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	2,736	614
Commercial and industrial | Non-owner occupied commercial real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	7,154	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	2,527	5,761
Current	1,066,094	1,020,153
Nonaccrual	1,079	1,167
Total	1,069,700	1,027,081
Commercial and industrial | Real estate construction | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,940	5,689
Commercial and industrial | Real estate construction | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	587	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	3,069	3,839
Current	525,328	541,455
Nonaccrual	21,710	20,543
Total	550,107	565,837
Agricultural and agricultural real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,789	3,734
Agricultural and agricultural real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	280	79
Agricultural and agricultural real estate | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	26
Residential real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	5,784	4,370
Current	773,154	814,840
Nonaccrual	13,602	13,067
Total	792,540	832,277
Residential real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	5,637	4,166
Residential real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	147	24
Residential real estate | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	180
Consumer
Financing Receivable, Past Due [Line Items]
Total Past Due	2,042	3,162
Current	421,714	436,675
Nonaccrual	4,818	3,495
Total	428,574	443,332
Consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,783	2,511
Consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	259	651
Consumer | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 0	$ 0