FAIR VALUE DISCLOSURES - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	$ 68,932	$ 29,188
Financial assets
Investment securities held-to-maturity	154,327	429,328
Other investments	127,439	115,660
Deposits
Noninterest-bearing	2,501,290	2,492,434
Savings	2,953,114	3,167,325
Time	2,321,908	2,173,564
Carrying value
Financial assets
Cash and short-term investments	271,362	273,959
Investment securities held-to-maturity	154,327	429,328
Other investments	127,439	115,660
Loans held for sale	20,244	4,372
Loans and leases	8,919,237	8,767,672
Interest Receivable	44,474	41,816
Deposits
Deposits	10,109,004	10,140,394
Short-term borrowings	1,313,321	1,040,691
Long-term debt	547,042	570,739
Interest Payable	12,730	12,126
Fair value
Financial assets
Cash and short-term investments	271,362	273,959
Investment securities held-to-maturity	153,039	424,118
Loans held for sale	20,244	4,372
Loans and leases	8,850,385	8,662,868
Interest Receivable	44,474	41,816
Deposits
Deposits	10,102,924	10,113,475
Short-term borrowings	1,313,321	1,040,691
Long-term debt	545,983	557,933
Interest Payable	12,730	12,126
Fair Value, Inputs, Level 1 [Member] | Fair value
Financial assets
Cash and short-term investments	271,362	273,959
Investment securities held-to-maturity	0	0
Loans held for sale	0	0
Loans and leases	0	0
Interest Receivable	0	0
Deposits
Deposits	0	0
Short-term borrowings	1,313,321	1,040,691
Long-term debt	0	0
Interest Payable	2,859	2,035
Fair Value, Inputs, Level 2 [Member] | Fair value
Financial assets
Cash and short-term investments	0	0
Investment securities held-to-maturity	153,039	424,118
Loans held for sale	20,244	4,372
Loans and leases	0	0
Interest Receivable	14,287	13,819
Deposits
Deposits	10,102,924	10,113,475
Short-term borrowings	0	0
Long-term debt	545,983	557,933
Interest Payable	9,871	10,091
Fair Value, Inputs, Level 3 [Member] | Fair value
Financial assets
Cash and short-term investments	0	0
Investment securities held-to-maturity	0	0
Loans held for sale	0	0
Loans and leases	8,850,385	8,662,868
Interest Receivable	30,187	27,997
Deposits
Deposits	0	0
Short-term borrowings	0	0
Long-term debt	0	0
Interest Payable	$ 0	$ 0