FAIR VALUE - Summary of Assets and Liabilities measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets measured at fair value on recurring basis
Available for sale securities	$ 553,278	$ 638,291
U.S. Treasury securities
Assets measured at fair value on recurring basis
Available for sale securities	59,999	50,822
U.S. GSE securities
Assets measured at fair value on recurring basis
Available for sale securities		4,995
State and municipal obligations
Assets measured at fair value on recurring basis
Available for sale securities	37,946	34,964
U.S. GSE residential mortgage-backed securities
Assets measured at fair value on recurring basis
Available for sale securities	81,654	84,691
U.S. GSE residential collateralized mortgage obligations
Assets measured at fair value on recurring basis
Available for sale securities	205,492	277,851
U.S. GSE commercial mortgage-backed securities
Assets measured at fair value on recurring basis
Available for sale securities	17,049	13,609
U.S. GSE commercial collateralized mortgage obligations
Assets measured at fair value on recurring basis
Available for sale securities	83,380	104,156
Other asset backed securities
Assets measured at fair value on recurring basis
Available for sale securities	22,552	23,401
Corporate bonds
Assets measured at fair value on recurring basis
Available for sale securities	45,206	43,802
Carrying Amount
Assets measured at fair value on recurring basis
Available for sale securities	553,278	638,291
Financial Assets: Derivatives	57,874	15,437
Financial Liabilities:
Financial liabilities: Derivatives	68,839	16,645
Fair Value
Assets measured at fair value on recurring basis
Available for sale securities	553,278	638,291
Financial Assets: Derivatives	57,874	15,437
Financial Liabilities:
Financial liabilities: Derivatives	68,839	16,645
Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets measured at fair value on recurring basis
Available for sale securities	0	0
Financial Assets: Derivatives	0	0
Financial Liabilities:
Financial liabilities: Derivatives	0	0
Significant Other Observable Inputs (Level 2)
Assets measured at fair value on recurring basis
Available for sale securities	553,278	638,291
Financial Assets: Derivatives	57,874	15,437
Financial Liabilities:
Financial liabilities: Derivatives	68,839	16,645
Significant Unobservable Inputs (Level 3)
Assets measured at fair value on recurring basis
Available for sale securities	0	0
Financial Assets: Derivatives	0	0
Financial Liabilities:
Financial liabilities: Derivatives	0	0
Recurring basis | Carrying Amount
Assets measured at fair value on recurring basis
Available for sale securities	553,278	638,291
Recurring basis | Carrying Amount | U.S. Treasury securities
Assets measured at fair value on recurring basis
Available for sale securities	59,999	50,822
Recurring basis | Carrying Amount | U.S. GSE securities
Assets measured at fair value on recurring basis
Available for sale securities		4,995
Recurring basis | Carrying Amount | State and municipal obligations
Assets measured at fair value on recurring basis
Available for sale securities	37,946	34,964
Recurring basis | Carrying Amount | U.S. GSE residential mortgage-backed securities
Assets measured at fair value on recurring basis
Available for sale securities	81,654	84,691
Recurring basis | Carrying Amount | U.S. GSE residential collateralized mortgage obligations
Assets measured at fair value on recurring basis
Available for sale securities	205,492	277,851
Recurring basis | Carrying Amount | U.S. GSE commercial mortgage-backed securities
Assets measured at fair value on recurring basis
Available for sale securities	17,049	13,609
Recurring basis | Carrying Amount | U.S. GSE commercial collateralized mortgage obligations
Assets measured at fair value on recurring basis
Available for sale securities	83,380	104,156
Recurring basis | Carrying Amount | Other asset backed securities
Assets measured at fair value on recurring basis
Available for sale securities	22,552	23,401
Recurring basis | Carrying Amount | Corporate bonds
Assets measured at fair value on recurring basis
Available for sale securities	45,206	43,802
Recurring basis | Carrying Amount | Derivatives
Assets measured at fair value on recurring basis
Financial Assets: Derivatives	57,874	15,437
Financial Liabilities:
Financial liabilities: Derivatives	68,839	16,645
Recurring basis | Significant Other Observable Inputs (Level 2)
Assets measured at fair value on recurring basis
Available for sale securities	553,278	638,291
Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. Treasury securities
Assets measured at fair value on recurring basis
Available for sale securities	59,999	50,822
Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. GSE securities
Assets measured at fair value on recurring basis
Available for sale securities		4,995
Recurring basis | Significant Other Observable Inputs (Level 2) | State and municipal obligations
Assets measured at fair value on recurring basis
Available for sale securities	37,946	34,964
Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. GSE residential mortgage-backed securities
Assets measured at fair value on recurring basis
Available for sale securities	81,654	84,691
Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. GSE residential collateralized mortgage obligations
Assets measured at fair value on recurring basis
Available for sale securities	205,492	277,851
Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. GSE commercial mortgage-backed securities
Assets measured at fair value on recurring basis
Available for sale securities	17,049	13,609
Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. GSE commercial collateralized mortgage obligations
Assets measured at fair value on recurring basis
Available for sale securities	83,380	104,156
Recurring basis | Significant Other Observable Inputs (Level 2) | Other asset backed securities
Assets measured at fair value on recurring basis
Available for sale securities	22,552	23,401
Recurring basis | Significant Other Observable Inputs (Level 2) | Corporate bonds
Assets measured at fair value on recurring basis
Available for sale securities	45,206	43,802
Recurring basis | Significant Other Observable Inputs (Level 2) | Derivatives
Assets measured at fair value on recurring basis
Financial Assets: Derivatives	57,874	15,437
Financial Liabilities:
Financial liabilities: Derivatives	$ 68,839	$ 16,645