Investments - Summary of Amortized Cost and Fair Values of Fixed Maturity Securities (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Cost	$ 38.4	$ 38.5
Gross unrealized gains	0.1	0.3
Gross unrealized losses	(1.4)	(0.5)
Fair value	37.1	38.3
U.S. Treasury securities, obligations of U.S. Government agencies and Municipalities
Debt Securities, Available-for-sale [Line Items]
Cost	30.2	30.2
Gross unrealized gains	0.1	0.2
Gross unrealized losses	(1.2)	(0.4)
Fair value	29.1	30.0
Corporate debt
Debt Securities, Available-for-sale [Line Items]
Cost	8.2	8.3
Gross unrealized gains		0.1
Gross unrealized losses	(0.2)	(0.1)
Fair value	$ 8.0	$ 8.3

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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Amount, before tax, of unrealized loss 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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Amount 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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