INVESTMENTS - Amortized Cost and Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 125.4	$ 129.5
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	0.0	1.2
Gross Unrealized Losses	(4.6)	(0.8)
Fair Value	120.8	129.9
U.S. Treasury securities and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	23.3	23.7
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.8)	(0.4)
Fair Value	22.5	23.3
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	20.0	20.4
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	0.0	0.3
Gross Unrealized Losses	(0.9)	(0.1)
Fair Value	19.1	20.6
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	48.5	48.2
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	0.0	0.7
Gross Unrealized Losses	(1.9)	(0.2)
Fair Value	46.6	48.7
Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2.7	3.5
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.2)	0.0
Fair Value	2.5	3.5
Commercial mortgage backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	27.9	30.2
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	0.0	0.2
Gross Unrealized Losses	(0.8)	(0.1)
Fair Value	27.1	30.3
Other debt obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2.5	3.5
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Fair Value	2.5	3.5
Total fixed maturities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	124.9
Allowance for Expected Credit Losses	0.0
Gross Unrealized Gains	0.0
Gross Unrealized Losses	(4.6)
Fair Value	120.3	$ 129.9
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	0.5
Allowance for Expected Credit Losses	0.0
Gross Unrealized Gains	0.0
Gross Unrealized Losses	0.0
Fair Value	$ 0.5

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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