SECURITIES - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) security segment	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($) security
Financial Instruments Owned and Pledged as Collateral [Line Items]
Available-for-sale securities, at fair value transferred to held to maturity	$ 50,000,000
Loss on transfer of securities	2,200,000
Proceeds from sale of available for sale securities	$ 0	$ 0
Number of portfolio segments | segment	2
Impairment loss realized in consolidated statements of income	$ 0
Average loss on securities in an unrealized loss position	0.0258		0.0169
Number of securities in an unrealized loss position | security	18		18
Repurchase Agreements
Financial Instruments Owned and Pledged as Collateral [Line Items]
Amortized cost of securities pledged	$ 6,100,000		$ 6,300,000
Securities pledged and available to be sold under repurchase agreements, fair value	6,000,000		6,300,000
Securities pledged to various Federal Reserve Districts relating to deposits of bankruptcy trustees
Financial Instruments Owned and Pledged as Collateral [Line Items]
Amortized cost of securities	73,900,000		55,700,000
Fair value of pledged securities	72,900,000		55,500,000
Derivative
Financial Instruments Owned and Pledged as Collateral [Line Items]
Amortized cost of securities pledged	3,400,000		3,400,000
Securities pledged and available to be sold under repurchase agreements, fair value	$ 3,200,000		$ 3,300,000