Fair Value Measurements

12 Months Ended

Dec. 31, 2025

Fair Value Disclosures [Abstract]

Fair Value Measurements

Fair Value Measurements

Assets measured at fair values on a recurring basis

    We measure and report our cash equivalents, restricted cash, and available-for-sale marketable securities at fair value on a recurring basis. The following tables summarize the fair value of these financial assets by significant investment category and their levels within the fair value hierarchy (in millions):

	December 31, 2025								December 31, 2024
	Level I		Level II		Level III		Total		Level I		Level II		Level III		Total
Financial Assets:
Cash Equivalents:
Money market funds	$	1,174.8	$	—	$	—	$	1,174.8	$	1,707.5	$	—	$	—	$	1,707.5
Commercial paper	—		29.8		—		29.8		—		—		—		—
Corporate bonds	—		6.6		—		6.6		—		—		—		—
Agency securities	—		—		—		—		—		3.0		—		3.0
U.S. government notes	124.9		—		—		124.9		31.4		—		—		31.4
	1,299.7		36.4		—		1,336.1		1,738.9		3.0		—		1,741.9
Marketable Securities:
Commercial paper	—		83.0		—		83.0		—		48.8		—		48.8
U.S. government notes	2,854.3		—		—		2,854.3		1,921.5		—		—		1,921.5
Corporate bonds	—		4,329.7		—		4,329.7		—		2,593.6		—		2,593.6
Municipal bonds	—		14.5				14.5		—		—		—		—
Agency securities	—		1,497.6		—		1,497.6		—		977.2		—		977.2
	2,854.3		5,924.8		—		8,779.1		1,921.5		3,619.6		—		5,541.1
Other Assets:
Money market funds - restricted cash	1.4		—		—		1.4		1.4		—		—		1.4
Total Financial Assets	$	4,155.4	$	5,961.2	$	—	$	10,116.6	$	3,661.8	$	3,622.6	$	—	$	7,284.4

During the year ended on December 31, 2025, the Company did not make any transfers between the levels of the fair value hierarchy.

    The following table summarizes the amortized cost, unrealized gains and losses, and fair value of our debt securities measured at fair value on a recurring basis (in millions):

	December 31, 2025								December 31, 2024
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value		Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Commercial paper	$	112.8	$	—	$	—	$	112.8	$	48.8	$	—	$	—	$	48.8
U.S. government	2,970.4		8.8		—		2,979.2		1,954.8		2.7		(4.6)		1,952.9
Corporate bonds	4,321.2		16.0		(0.9)		4,336.3		2,595.7		4.4		(6.5)		2,593.6
Municipal bonds	14.5		—		—		14.5		—		—		—		—
Agency securities	1,495.5		2.7		(0.6)		1,497.6		981.0		1.6		(2.4)		980.2
Total	$	8,914.4	$	27.5	$	(1.5)	$	8,940.4	$	5,580.3	$	8.7	$	(13.5)	$	5,575.5

For debt securities in unrealized loss positions, it is not likely that we will be required to sell such securities before recovery of their amortized cost basis nor do we have the intent to sell such securities before maturity; we invest in debt securities that have maximum maturities of three years and are generally deemed to be low risk based on their credit ratings from the major rating agencies. The longer the duration of these marketable securities, the more susceptible they are to changes in market interest rates and bond yields. Given the short-term and conservative nature of our portfolio, our debt securities are exposed to minimal credit risk; therefore, we did not recognize any credit losses or non-credit-related impairments related to our available-for-sale marketable debt securities for the years ended 2025, 2024 and 2023. All unrealized losses were recognized in other comprehensive income (loss). Realized gains or losses were immaterial for the years ended 2025, 2024 and 2023.

    The following table is an analysis of our debt securities in unrealized loss positions (in millions):

	December 31, 2025
	Unrealized Losses within 12 months				Unrealized Losses 12 months or greater				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Commercial paper	$	9.9	$	—	$	—	$	—	$	9.9	$	—
U.S. government notes	260.8		$	—	15.0		—		275.8		—
Corporate bonds	857.7		(0.9)		29.9		—		887.6		(0.9)
Municipal bonds	4.7		—		—		—		4.7		—
Agency securities	473.1		(0.6)		—		—		473.1		(0.6)
Total	$	1,606.2	$	(1.5)	$	44.9	$	—	$	1,651.1	$	(1.5)

As of December 31, 2025, we had no marketable debt securities with contractual maturities that exceed 36 months. The fair values of marketable debt securities, by remaining contractual maturities, are as follows (in millions):

	December 31, 2025
Due in 1 year or less	$	3,267.4
Due in 1 year through 3 years	5,511.7
Total marketable securities	$	8,779.1

The weighted-average remaining duration of our marketable debt securities is approximately 1.4 years as of December 31, 2025.