Debt Securities - Gross Unrealized Losses and Fair Value Available-For-Sale Debt securities in Unrealized Loss Position (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	$ 32.1
Less Than 12 Months, Unrealized Losses	(0.2)
12 Months or Longer, Fair Value	0.0
12 Months or Longer, Unrealized Loss	0.0
Total Fair Value	32.1
Total Unrealized Losses	(0.2)
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	199.5	$ 428.6
Less Than 12 Months, Unrealized Losses	(1.9)	(1.6)
12 Months or Longer, Fair Value	299.1	0.0
12 Months or Longer, Unrealized Loss	(5.6)	0.0
Total Fair Value	498.6	428.6
Total Unrealized Losses	(7.5)	(1.6)
Securities of government-sponsored entities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	107.7	230.5
Less Than 12 Months, Unrealized Losses	(2.5)	(1.0)
12 Months or Longer, Fair Value	198.4	0.0
12 Months or Longer, Unrealized Loss	(4.5)	0.0
Total Fair Value	306.1	230.5
Total Unrealized Losses	$ (7.0)	$ (1.0)

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 accumulated unrealized loss on 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 12 months or longer, 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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