COMMITMENTS AND CONTINGENCIES, INCLUDING FINANCIAL INSTRUMENTS WITH OFF-BALANCE-SHEET RISK - Contingent Liabilities & Lease Commitments (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($) item	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Contingent Liabilities
Number of private investment funds under the Small Business Investment Company (SBIC) program | item	2
Unfunded commitments	$ 3.0		$ 3.8
Cumulative capital contributions	2.4		$ 1.6
Lease Commitments
Rent expense	$ 1.4	$ 1.4