Cash, Cash Equivalents and Short-Term Investments - Schedule of Breakdown of the Short-Term Investments (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Less than 12 months
Fair Value	$ 17.2	$ 43.5
Gross Unrealized Losses	0.0	(0.2)
More than 12 months
Fair Value	263.1	534.8
Gross Unrealized Losses	(8.5)	(21.1)
Total
Fair Value	280.3	578.3
Gross Unrealized Losses	(8.5)	(21.3)
Corporate notes and obligations
Less than 12 months
Fair Value	6.2	25.1
Gross Unrealized Losses	0.0	(0.1)
More than 12 months
Fair Value	123.9	240.3
Gross Unrealized Losses	(4.1)	(10.2)
Total
Fair Value	130.1	265.4
Gross Unrealized Losses	(4.1)	(10.3)
U.S. Treasury securities
Less than 12 months
Fair Value	4.8	17.8
Gross Unrealized Losses	0.0	(0.1)
More than 12 months
Fair Value	76.0	174.0
Gross Unrealized Losses	(2.8)	(6.0)
Total
Fair Value	80.8	191.8
Gross Unrealized Losses	(2.8)	(6.1)
Asset backed securities
Less than 12 months
Fair Value	0.0	0.6
Gross Unrealized Losses	0.0	0.0
More than 12 months
Fair Value	32.6	66.0
Gross Unrealized Losses	(0.6)	(2.3)
Total
Fair Value	32.6	66.6
Gross Unrealized Losses	(0.6)	(2.3)
Municipal securities
Less than 12 months
Fair Value	6.2	0.0
Gross Unrealized Losses	0.0	0.0
More than 12 months
Fair Value	25.3	46.1
Gross Unrealized Losses	(0.7)	(2.0)
Total
Fair Value	31.5	46.1
Gross Unrealized Losses	(0.7)	(2.0)
U.S. agency obligations
Less than 12 months
Fair Value	0.0	0.0
Gross Unrealized Losses	0.0	0.0
More than 12 months
Fair Value	3.6	3.5
Gross Unrealized Losses	(0.2)	(0.3)
Total
Fair Value	3.6	3.5
Gross Unrealized Losses	(0.2)	(0.3)
Foreign government obligations
Less than 12 months
Fair Value		0.0
Gross Unrealized Losses		0.0
More than 12 months
Fair Value		3.3
Gross Unrealized Losses		(0.2)
Total
Fair Value		3.3
Gross Unrealized Losses		(0.2)
Supranational securities
Less than 12 months
Fair Value	0.0	0.0
Gross Unrealized Losses	0.0	0.0
More than 12 months
Fair Value	1.7	1.6
Gross Unrealized Losses	(0.1)	(0.1)
Total
Fair Value	1.7	1.6
Gross Unrealized Losses	$ (0.1)	$ (0.1)

Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions

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