FAIR VALUE - CARRYING AMOUNTS AND FV OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Assets:
Available-for-sale debt securities	$ 486,847		$ 471,355
Held-to-maturity debt securities	56,266		63,156
Equity securities with readily determinable fair value	3,015		3,188
Mortgage loans held for sale, at fair value	40,028	$ 39,384	19,224	$ 13,883	$ 11,313	$ 8,971
Consumer loans held for sale, at fair value	164	3,431	598
Consumer loans held for sale, at the lower of cost or fair value	12,800	$ 12,089	11,646	$ 37,609	$ 12,864	$ 12,838
Carrying Value
Assets:
Cash and cash equivalents	560,195		385,303
Available-for-sale debt securities	486,847		471,355
Held-to-maturity debt securities	55,745		62,531
Equity securities with readily determinable fair value	3,015		3,188
Mortgage loans held for sale, at fair value	40,028		19,224
Consumer loans held for sale, at fair value	164		598
Consumer loans held for sale, at the lower of cost or fair value	12,800		11,646
Loans, net	5,009,995		4,389,800
Federal Home Loan Bank stock	25,629		30,831
Accrued interest receivable	11,146		12,937
Rate lock loan commitments	4,436		789
Interest rate swap agreements	15,324		5,062
Liabilities:
Securities sold under agreements to repurchase and other short-term borrowings	177,397		167,617
Federal Home Loan Bank advances	137,500		750,000
Subordinated note	41,240		41,240
Accrued interest payable	1,117		2,802
Mandatory forward contracts	659		131
Interest rate swap agreements	15,491		5,166
Carrying Value | Non Interest Bearing Deposits
Liabilities:
Deposit liabilities, fair value	1,821,400		1,033,379
Carrying Value | Transaction deposits
Liabilities:
Deposit liabilities, fair value	2,305,085		2,018,687
Carrying Value | Time deposits.
Liabilities:
Deposit liabilities, fair value	891,600		733,942
Total Fair Value
Assets:
Cash and cash equivalents	560,195		385,303
Available-for-sale debt securities	486,847		471,355
Held-to-maturity debt securities	56,266		63,156
Equity securities with readily determinable fair value	3,015		3,188
Mortgage loans held for sale, at fair value	40,028		19,224
Consumer loans held for sale, at fair value	164		598
Consumer loans held for sale, at the lower of cost or fair value	12,800		11,646
Loans, net	4,979,895		4,381,396
Accrued interest receivable	11,146		12,937
Rate lock loan commitments	4,436		789
Interest rate swap agreements	15,324		5,062
Liabilities:
Securities sold under agreements to repurchase and other short-term borrowings	177,397		167,617
Federal Home Loan Bank advances	139,831		749,667
Subordinated note	31,805		32,587
Accrued interest payable	1,117		2,802
Mandatory forward contracts	659		131
Interest rate swap agreements	15,491		5,166
Total Fair Value | Non Interest Bearing Deposits
Liabilities:
Deposit liabilities, fair value	1,821,400		1,033,379
Total Fair Value | Transaction deposits
Liabilities:
Deposit liabilities, fair value	2,305,085		2,018,687
Total Fair Value | Time deposits.
Liabilities:
Deposit liabilities, fair value	901,588		737,733
Total Fair Value | Fair Value, Inputs, Level 1
Assets:
Cash and cash equivalents	560,195		385,303
Equity securities with readily determinable fair value	2,530		2,474
Total Fair Value | Fair Value, Inputs, Level 2
Assets:
Available-for-sale debt securities	480,324		463,860
Held-to-maturity debt securities	56,266		63,156
Equity securities with readily determinable fair value	485		714
Mortgage loans held for sale, at fair value	40,028		19,224
Accrued interest receivable	11,146		12,937
Rate lock loan commitments	4,436		789
Interest rate swap agreements	15,324		5,062
Liabilities:
Securities sold under agreements to repurchase and other short-term borrowings	177,397		167,617
Federal Home Loan Bank advances	139,831		749,667
Subordinated note	31,805		32,587
Accrued interest payable	1,117		2,802
Mandatory forward contracts	659		131
Interest rate swap agreements	15,491		5,166
Total Fair Value | Fair Value, Inputs, Level 2 | Non Interest Bearing Deposits
Liabilities:
Deposit liabilities, fair value	1,821,400		1,033,379
Total Fair Value | Fair Value, Inputs, Level 2 | Transaction deposits
Liabilities:
Deposit liabilities, fair value	2,305,085		2,018,687
Total Fair Value | Fair Value, Inputs, Level 2 | Time deposits.
Liabilities:
Deposit liabilities, fair value	901,588		737,733
Total Fair Value | Fair Value, Inputs, Level 3
Assets:
Available-for-sale debt securities	6,523		7,495
Consumer loans held for sale, at fair value	164		598
Consumer loans held for sale, at the lower of cost or fair value	12,800		11,646
Loans, net	$ 4,979,895		$ 4,381,396