INVESTMENTS - Schedule of Amortized Cost and Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 519.1	$ 383.1
Allowance for Expected Credit Losses	0.0
Gross Unrealized Gains	1.2
Gross Unrealized Losses	(3.2)
Fair Value	517.1	387.0
United States Treasury securities and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	58.3	48.4
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	0.1	0.8
Gross Unrealized Losses	(0.2)	0.0
Fair Value	58.2	49.2
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	22.0	23.0
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	0.1	0.3
Gross Unrealized Losses	(0.1)	(0.1)
Fair Value	22.0	23.2
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	237.0	157.3
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	0.6	1.9
Gross Unrealized Losses	(1.5)	(0.2)
Fair Value	236.1	159.0
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	191.0	154.4
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	0.4	1.5
Gross Unrealized Losses	(1.4)	(0.3)
Fair Value	190.0	155.6
Total fixed maturities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	508.3	383.1
Allowance for Expected Credit Losses	0.0	0.0
Gross Unrealized Gains	1.2	4.5
Gross Unrealized Losses	(3.2)	(0.6)
Fair Value	506.3	$ 387.0
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	10.8
Allowance for Expected Credit Losses	0.0
Gross Unrealized Gains	0.0
Gross Unrealized Losses	0.0
Fair Value	$ 10.8

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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