SECURITIES - Securities carrying amount (Details) $ in Millions	12 Months Ended
Dec. 31, 2021 USD ($) item	Dec. 31, 2020 USD ($) item	Dec. 31, 2019 USD ($)
SECURITIES.
Securities sold during the year	$ 0.0	$ 0.0	$ 20.4
Carrying value of securities pledged	25.6	27.3
Accrued interest receivable for securities	$ 2.0	$ 1.2
Securities held in a gross unrealized loss position \| item	115	18

Interest, dividends, rents, ancillary and other revenues earned but not yet received by the entity on its investments.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(4))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant