FAIR VALUE MEASUREMENTS - FAIR VALUE ACTIVITY (Details) - Significant unobservable inputs (Level 3) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Corporate securities
Assets:
Purchases	$ 6.3	$ 9.3	$ 10.5	$ 24.2
Sales	0.0	(6.6)	(1.4)	(11.2)
Issuances	0.0	0.0	0.0	0.0
Settlements	0.0	0.0	0.0	0.0
Purchases, sales, issuances and settlements, net	6.3	2.7	9.1	13.0
Corporate securities \| Variable Interest Entities
Assets:
Purchases				0.0
Sales				(2.1)
Issuances				0.0
Settlements				0.0
Purchases, sales, issuances and settlements, net				(2.1)
Asset-backed securities
Assets:
Purchases	1.3	19.0	3.8	26.9
Sales	(0.2)	(0.7)	(7.7)	(0.9)
Issuances	0.0	0.0	0.0	0.0
Settlements	0.0	0.0	0.0	0.0
Purchases, sales, issuances and settlements, net	1.1	18.3	(3.9)	26.0
Non-agency residential mortgage-backed securities
Assets:
Purchases		0.0	0.0	6.5
Sales		(0.1)	(0.1)	(0.5)
Issuances		0.0	0.0	0.0
Settlements		0.0	0.0	0.0
Purchases, sales, issuances and settlements, net	0.0	(0.1)	(0.1)	6.0
Commercial mortgage-backed securities
Assets:
Purchases				28.0
Sales				0.0
Issuances				0.0
Settlements				0.0
Purchases, sales, issuances and settlements, net	0.0	0.0	0.0	28.0
Total fixed maturities, available for sale
Assets:
Purchases	7.6	28.3	14.3	85.6
Sales	(0.2)	(7.4)	(9.2)	(12.6)
Issuances	0.0	0.0	0.0	0.0
Settlements	0.0	0.0	0.0	0.0
Purchases, sales, issuances and settlements, net	7.4	20.9	5.1	73.0
Equity securities - corporate securities
Assets:
Purchases			0.0	67.0
Sales			(2.1)	(3.1)
Issuances			0.0	0.0
Settlements			0.0	0.0
Purchases, sales, issuances and settlements, net	0.0	0.0	(2.1)	63.9
Other invested assets - residual tranches
Assets:
Purchases	3.9	1.6	6.4	2.8
Sales	0.0	0.0	(0.3)	0.0
Issuances	0.0	0.0	0.0	0.0
Settlements	0.0	0.0	0.0	0.0
Purchases, sales, issuances and settlements, net	$ 3.9	$ 1.6	$ 6.1	$ 2.8

Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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