Investments - Schedule of Investments' Gross Unrealized Loss and Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	$ 17.9	$ 20.7
Unrealized Losses, Less than 12 Months	(0.7)	(0.4)
Fair Value, 12 Months or More	11.8	1.0
Unrealized Losses, 12 Months or More	(1.0)	0.0
Fair Value	29.7	21.7
Unrealized Losses	(1.7)	(0.4)
U.S. Treasury securities, obligations of U.S. Government agencies and municipalities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	11.9	16.8
Unrealized Losses, Less than 12 Months	(0.6)	(0.3)
Fair Value, 12 Months or More	10.1	1.0
Unrealized Losses, 12 Months or More	(0.8)	0.0
Fair Value	22.0	17.8
Unrealized Losses	(1.4)	(0.3)
Corporate debt
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	6.0	3.9
Unrealized Losses, Less than 12 Months	(0.1)	(0.1)
Fair Value, 12 Months or More	1.7	0.0
Unrealized Losses, 12 Months or More	(0.2)	0.0
Fair Value	7.7	3.9
Unrealized Losses	$ (0.3)	$ (0.1)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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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), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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