INVESTMENTS - Schedule of Amortized Cost and Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 320.4	$ 309.1
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	3.3	0.8
Gross Unrealized Losses	(1.0)	(3.1)
Fair Value	322.7	306.8
U.S. Treasury securities and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	47.4	46.5
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	0.7	0.0
Gross Unrealized Losses	(0.1)	(0.3)
Fair Value	48.0	46.2
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	22.3	23.9
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	0.2	0.1
Gross Unrealized Losses	(0.2)	(0.5)
Fair Value	22.3	23.5
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	121.7	106.6
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	1.3	0.3
Gross Unrealized Losses	(0.4)	(1.2)
Fair Value	122.6	105.7
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	125.5	117.3
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	1.1	0.4
Gross Unrealized Losses	(0.3)	(1.1)
Fair Value	126.3	116.6
Total fixed maturities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	316.9	294.3
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	3.3	0.8
Gross Unrealized Losses	(1.0)	(3.1)
Fair Value	319.2	292.0
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3.5	14.8
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	$ 3.5	$ 14.8

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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