FAIR VALUE DISCLOSURES - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financial assets
Investment securities held-to-maturity	$ 127,347	$ 142,862
Other investments	132,366	125,020
Interest Receivable	39,022
Deposits
Noninterest-bearing	3,515,048	2,643,928
Savings	3,287,314	2,960,979
Time	2,241,212	2,240,441
Carrying value
Financial assets
Cash and short-term investments	322,484	257,639
Investment securities held-to-maturity	127,347	142,862
Other investments	132,366	125,020
Loans held for sale	43,950	13,680
Loans and leases	10,023,050	9,144,015
Interest Receivable	51,600	39,591
Deposits
Deposits	11,701,415	10,210,229
Short-term borrowings	154,347	1,316,181
Long-term debt	1,285,767	414,376
Interest Payable	10,432	13,671
Fair value
Financial assets
Cash and short-term investments	322,484	257,639
Investment securities held-to-maturity	132,956	142,821
Loans held for sale	43,950	13,680
Loans and leases	10,038,565	9,134,215
Interest Receivable	51,600	39,591
Deposits
Deposits	11,714,041	10,209,790
Short-term borrowings	154,347	1,316,181
Long-term debt	1,280,963	414,937
Interest Payable	10,432	13,671
Fair Value, Inputs, Level 1 [Member] | Fair value
Financial assets
Cash and short-term investments	322,484	257,639
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	154,347	1,316,181
Long-term debt	0	0
Interest Payable	120	1,899
Fair Value, Inputs, Level 2 [Member] | Fair value
Financial assets
Cash and short-term investments	0	0
Investment securities held-to-maturity	132,956	142,821
Loans held for sale	43,950	13,680
Loans and leases	0	0
Interest Receivable	12,578	12,743
Deposits
Deposits	11,714,041	10,209,790
Short-term borrowings	0	0
Long-term debt	1,280,963	414,937
Interest Payable	10,312	11,772
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	10,038,565	9,134,215
Interest Receivable		26,848
Deposits
Deposits	0	0
Short-term borrowings	0	0
Long-term debt	0	0
Interest Payable	$ 0	$ 0