Investments - Summary of Amortized Cost and Fair Values of Fixed Maturity Securities (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Cost	$ 32.0	$ 38.5
Gross unrealized gains	0.0	0.3
Gross unrealized losses	(2.3)	(0.5)
Fair value	29.7	38.3
U.S. Treasury securities, obligations of U.S. Government agencies and municipalities
Debt Securities, Available-for-sale [Line Items]
Cost	22.9	30.2
Gross unrealized gains	0.0	0.2
Gross unrealized losses	(1.9)	(0.4)
Fair value	21.0	30.0
Corporate debt
Debt Securities, Available-for-sale [Line Items]
Cost	8.2	8.3
Gross unrealized gains		0.1
Gross unrealized losses	(0.4)	(0.1)
Fair value	7.8	$ 8.3
Other
Debt Securities, Available-for-sale [Line Items]
Cost	0.9
Gross unrealized gains	0.0
Gross unrealized losses	0.0
Fair value	$ 0.9

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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Amortized cost of 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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