Cash, Cash Equivalents, and Marketable Debt Securities - Schedule of Company's Cash and Available-For-Sale (AFS) Debt Securities by Major Asset Category (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2024		Dec. 31, 2023
Financial Instruments [Line Items]
Adjusted Cost Basis	[1]	$ 1,253.5		$ 1,205.8
Unrealized Gain	[1]	0.1		0.3
Unrealized Loss	[1]	(0.4)		(0.5)
Fair Value	[1]	1,253.2		1,205.6
Cash and cash equivalents	[1]	692.4		648.0
Short-term marketable debt securities ($92.3 million and $93.5 million measured at fair value as of March 31, 2024 and December 31, 2023, respectively)	[1]	492.3		493.5
Long-term marketable debt securities	[1]	68.5		64.1
Level 1
Financial Instruments [Line Items]
Adjusted Cost Basis		34.9	[2]	30.9	[1]
Unrealized Gain		0.0	[2]	0.0	[1]
Unrealized Loss		(0.1)	[2]	0.0	[1]
Fair Value		34.8	[2]	30.9	[1]
Cash and cash equivalents		0.5	[2]	1.6	[1]
Short-term marketable debt securities ($92.3 million and $93.5 million measured at fair value as of March 31, 2024 and December 31, 2023, respectively)		17.5	[2]	11.3	[1]
Long-term marketable debt securities		16.8	[2]	18.0	[1]
Level 2
Financial Instruments [Line Items]
Adjusted Cost Basis		126.7	[1]	128.5	[2]
Unrealized Gain		0.1	[1]	0.3	[2]
Unrealized Loss		(0.3)	[1]	(0.5)	[2]
Fair Value		126.5	[1]	128.3	[2]
Cash and cash equivalents		0.0	[1]	0.0	[2]
Short-term marketable debt securities ($92.3 million and $93.5 million measured at fair value as of March 31, 2024 and December 31, 2023, respectively)		74.8	[1]	82.2	[2]
Long-term marketable debt securities		51.7	[1]	46.1	[2]
Cash and Cash Equivalents
Financial Instruments [Line Items]
Adjusted Cost Basis		691.9		646.4
Unrealized Gain		0.0		0.0
Unrealized Loss		0.0		0.0
Fair Value		691.9		646.4
Cash and cash equivalents		691.9		646.4
Short-term marketable debt securities ($92.3 million and $93.5 million measured at fair value as of March 31, 2024 and December 31, 2023, respectively)		0.0		0.0
Long-term marketable debt securities		0.0		0.0
Time Deposits
Financial Instruments [Line Items]
Adjusted Cost Basis	[3]	400.0		400.0
Unrealized Gain	[3]	0.0		0.0
Unrealized Loss	[3]	0.0		0.0
Fair Value	[3]	400.0		400.0
Cash and cash equivalents	[3]	0.0		0.0
Short-term marketable debt securities ($92.3 million and $93.5 million measured at fair value as of March 31, 2024 and December 31, 2023, respectively)	[3]	400.0		400.0
Long-term marketable debt securities	[3]	0.0		0.0
U.S. Treasury Securities | Level 1
Financial Instruments [Line Items]
Adjusted Cost Basis	[2]	34.4		29.3
Unrealized Gain	[2]	0.0		0.0
Unrealized Loss	[2]	(0.1)		(0.0)
Fair Value	[2]	34.3		29.3
Cash and cash equivalents	[2]	0.0		0.0
Short-term marketable debt securities ($92.3 million and $93.5 million measured at fair value as of March 31, 2024 and December 31, 2023, respectively)	[2]	17.5		11.3
Long-term marketable debt securities	[2]	16.8		18.0
Money Market Fund | Level 1
Financial Instruments [Line Items]
Adjusted Cost Basis	[2]	0.5		1.6
Unrealized Gain	[2]	0.0		0.0
Unrealized Loss	[2]	0.0		0.0
Fair Value	[2]	0.5		1.6
Cash and cash equivalents	[2]	0.5		1.6
Short-term marketable debt securities ($92.3 million and $93.5 million measured at fair value as of March 31, 2024 and December 31, 2023, respectively)	[2]	0.0		0.0
Long-term marketable debt securities	[2]	0.0		0.0
Corporate Debt Securities | Level 2
Financial Instruments [Line Items]
Adjusted Cost Basis	[1]	111.4		112.5
Unrealized Gain	[1]	0.1		0.3
Unrealized Loss	[1]	(0.2)		(0.4)
Fair Value	[1]	111.3		112.4
Cash and cash equivalents	[1]	0.0		0.0
Short-term marketable debt securities ($92.3 million and $93.5 million measured at fair value as of March 31, 2024 and December 31, 2023, respectively)	[1]	60.4		68.5
Long-term marketable debt securities	[1]	50.9		43.9
U.S. Government Agency Securities | Level 2
Financial Instruments [Line Items]
Adjusted Cost Basis	[1]	7.7		10.1
Unrealized Gain	[1]	0.0		0.0
Unrealized Loss	[1]	(0.1)		(0.1)
Fair Value	[1]	7.6		10.0
Cash and cash equivalents	[1]	0.0
Short-term marketable debt securities ($92.3 million and $93.5 million measured at fair value as of March 31, 2024 and December 31, 2023, respectively)	[1]	6.8		7.8
Long-term marketable debt securities	[1]	0.8		2.2
Certificates of Deposit | Level 2
Financial Instruments [Line Items]
Adjusted Cost Basis	[1]	7.6		5.9
Unrealized Gain	[1]	0.0		0.0
Unrealized Loss	[1]	0.0		0.0
Fair Value	[1]	7.6		5.9
Cash and cash equivalents	[1]	0.0		0.0
Short-term marketable debt securities ($92.3 million and $93.5 million measured at fair value as of March 31, 2024 and December 31, 2023, respectively)	[1]	7.6		5.9
Long-term marketable debt securities	[1]	$ 0.0		$ 0.0

[1] Valuations based on observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets and liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data.

[2] Valuations based on quoted prices for identical assets or liabilities in active markets.

[3] We had $400.0 million of investments in time deposits classified as HTM debt securities as of both March 31, 2024 and December 31, 2023. All these investments mature within one year and are recorded in “Short-term marketable debt securities” on our Consolidated Balance Sheets. We record HTM debt securities at amortized cost, which approximates fair value.