Cash, Cash Equivalents, and Marketable Debt Securities (Tables)

3 Months Ended

Mar. 31, 2025

Cash, Cash Equivalents, and Short-Term Investments [Abstract]

Schedule of Cash and Available-For-Sale Debt Securities by Major Asset Category

The following table shows the Company’s cash, cash equivalents, and available-for-sale ("AFS") debt securities by major asset category at March 31, 2025 and December 31, 2024 (in millions):

	March 31, 2025
	Adjusted Cost Basis		Unrealized Gain		Unrealized Loss		Fair Value		Cash and Cash Equivalents		Short-Term Marketable Debt Securities		Long-Term Marketable Debt Securities
Cash and cash equivalents	$	745.0	$	—	$	—	$	745.0	$	745.0	$	—	$	—
Level 1 (a):
U.S. Treasury securities		32.1		—		—		32.1		—		20.0		12.1
Money market funds		5.2		—		—		5.2		5.2		—		—
Subtotal		37.3		—		—		37.3		5.2		20.0		12.1
Level 2 (b):
Corporate debt securities		128.2		0.4		—		128.6		1.5		70.6		56.5
U.S. government agency securities		2.7		—		—		2.7		—		—		2.7
Certificates of deposit		0.8		—		—		0.8		—		0.8		—
Subtotal		131.7		0.4		—		132.1		1.5		71.4		59.2
Total	$	914.0	$	0.4	$	—	$	914.4	$	751.7	$	91.4	$	71.3

	December 31, 2024
	Adjusted Cost Basis		Unrealized Gain		Unrealized Loss		Fair Value		Cash and Cash Equivalents		Short-Term Marketable Debt Securities		Long-Term Marketable Debt Securities
Cash and cash equivalents	$	684.8	$	—	$	—	$	684.8	$	684.8	$	—	$	—
Level 1 (a):
U.S. Treasury securities		30.8		0.1		—		30.9		—		23.0		7.9
Money market funds		0.2		—		—		0.2		0.2		—		—
Subtotal		31.0		0.1		—		31.1		0.2		23.0		7.9
Level 2 (b):
Corporate debt securities		131.2		0.3		—		131.5		—		75.8		55.7
Certificates of deposit		2.4		—		—		2.4		—		2.4		—
U.S. government agency securities		2.4		—		—		2.4		—		0.8		1.6
Subtotal		136.0		0.3		—		136.3		—		79.0		57.3
Total	$	851.8	$	0.4	$	—	$	852.2	$	685.0	$	102.0	$	65.2

(a)Valuations based on quoted prices for identical assets or liabilities in active markets.

(b)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.

Schedule of Marketable Debt Securities in Continuous Loss Position

The following tables provide information about the Company’s marketable debt securities that have been in a continuous loss position as of March 31, 2025 and December 31, 2024 (in millions, except number of marketable debt securities in a loss position):

	March 31, 2025
	Fair Value of Marketable Debt Securities in a Loss Position < 12 Months		Number of Marketable Debt Securities in a Loss Position < 12 Months		Unrealized Losses < 12 Months (c)		Fair Value of Marketable Debt Securities in a Loss Position ≥ 12 Months		Number of Marketable Debt Securities in a Loss Position ≥ 12 Months		Unrealized Losses ≥ 12 Months (c)
Corporate debt securities	$	16.7		23	$	—	$	—		—	$	—
U.S. government agency securities		0.8		1		—		—		—		—
U.S. Treasury securities		—		—		—		1.2		1		—
	$	17.5		24	$	—	$	1.2		1	$	—

	December 31, 2024
	Fair Value of Marketable Debt Securities in a Loss Position < 12 Months		Number of Marketable Debt Securities in a Loss Position < 12 Months		Unrealized Losses < 12 Months		Fair Value of Marketable Debt Securities in a Loss Position ≥ 12 Months		Number of Marketable Debt Securities in a Loss Position ≥ 12 Months		Unrealized Losses ≥ 12 Months (c)
Corporate debt securities	$	16.5		26	$	0.1	$	2.7		4	$	—
U.S. Treasury securities		3.1		4		—		6.7		5		—
U.S. government agency securities		0.8		1		—		—		—		—
	$	20.4		31	$	0.1	$	9.4		9	$	—

(c)Unrealized losses were insignificant for the period presented.