SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - SALES INDUCEMENTS (NARRATIVE) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Deferred sales inducements	$ 22.5	$ 17.3	$ 14.1
Deferred sales inducements, amortization expense	17.8	15.5	$ 15.4
Unamortized deferred sales inducements	$ 65.9	$ 61.2

Amount of amortization expense (reversal of expense) for deferred sales inducement cost.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124505477&loc=d3e11332-158416

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 30
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=6481654&loc=d3e11214-158414

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(1)
-URI https://asc.fasb.org/extlink&oid=124501264&loc=SL117420844-207641

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 30
-Section 50
-Paragraph 2B
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124505477&loc=SL117422543-158416

Name:	us-gaap_DeferredSalesInducementsAmortizationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration