LOANS (Total Loans Outstanding) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 3,846,936	$ 3,819,525
Percentage of Subtotal	100.00%	100.00%
Less: Allowance for loan losses	$ (45,627)	$ (47,121)	$ (43,774)	$ (43,718)
Net deferred loan fees	(1,268)	(1,066)
Loans, net	3,800,041	3,771,338
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 3,400,710	$ 3,370,511
Percentage of Total commercial loans	88.40%	88.20%
Total consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of Total consumer loans	11.60%	11.80%
Other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 73,277	$ 74,369
Consumer Loan Open Ended Revolving Lines [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	446,226	449,014
Commercial and industrial loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: Allowance for loan losses	(20,725)	(21,097)	(19,781)	(20,272)
Commercial and industrial loans: | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 1,485,007	$ 1,418,681
Percentage of Total commercial loans	38.60%	37.10%
Commercial and industrial loans: | Working capital lines of credit loans | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 778,779	$ 743,609
Percentage of Total commercial loans	20.20%	19.40%
Commercial and industrial loans: | Non-working capital loans | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 706,228	$ 675,072
Percentage of Total commercial loans	18.40%	17.70%
Commercial real estate and multi-family residential loans: | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 1,482,076	$ 1,444,913
Percentage of Total commercial loans	38.50%	37.80%
Commercial real estate and multi-family residential loans: | Construction and land development loans | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 237,887	$ 224,474
Percentage of Total commercial loans	6.20%	5.90%
Commercial real estate and multi-family residential loans: | Owner occupied loans | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 543,192	$ 538,603
Percentage of Total commercial loans	14.10%	14.10%
Commercial real estate and multi-family residential loans: | Nonowner occupied loans | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 507,041	$ 508,121
Percentage of Total commercial loans	13.20%	13.30%
Commercial real estate and multi-family residential loans: | Multifamily loans | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 193,956	$ 173,715
Percentage of Total commercial loans	5.00%	4.50%
Agri-business and agricultural loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: Allowance for loan losses	$ (4,848)	$ (4,920)	$ (3,459)	$ (3,532)
Agri-business and agricultural loans: | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 316,970	$ 382,841
Percentage of Total commercial loans	8.30%	10.00%
Agri-business and agricultural loans: | Loans secured by farmland | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 145,363	$ 186,437
Percentage of Total commercial loans	3.80%	4.90%
Agri-business and agricultural loans: | Loans for agricultural production | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 171,607	$ 196,404
Percentage of Total commercial loans	4.50%	5.10%
Other commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of Total consumer loans	1.90%	2.00%
Other commercial loans | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 116,657	$ 124,076
Percentage of Total commercial loans	3.00%	3.30%
Consumer 1-4 family mortgage loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 372,949	$ 374,645
Percentage of Total consumer loans	9.70%	9.80%
Consumer 1-4 family mortgage loans: | Closed end first mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 180,542	$ 179,302
Percentage of Total consumer loans	4.70%	4.70%
Consumer 1-4 family mortgage loans: | Open end and junior lien loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 179,065	$ 181,865
Percentage of Total consumer loans	4.70%	4.80%
Consumer 1-4 family mortgage loans: | Residential construction and land development loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Commercial And Consumer Loans	$ 13,342	$ 13,478
Percentage of Total consumer loans	0.30%	0.30%