Equity Securities (Tables)

6 Months Ended

Jun. 30, 2025

Investments, Debt and Equity Securities [Abstract]

Summary of Investments in Equity Securities, by Accounting Classification

Investments in equity securities, by accounting classification, are summarized as follows:

(in millions)	June 30, 2025		December 31, 2024
Marketable equity securities	$	396.0	$	386.8
Non-marketable equity securities		218.3		202.4
Equity method investments		101.1		102.1
	$	715.4	$	691.3

Summary of Investments in Marketable Equity Securities

Investments in marketable equity securities are summarized as follows:

(in millions)	Cost		Unrealized (losses) gains			Estimated fair value
June 30, 2025
Common stocks	$	393.7	$	(9.5	)	$	384.2
Preferred stocks		11.4		0.4			11.8
	$	405.1	$	(9.1	)	$	396.0
December 31, 2024
Common stocks	$	397.3	$	(22.6	)	$	374.7
Preferred stocks		12.0		0.1			12.1
	$	409.3	$	(22.5	)	$	386.8

Summary of Changes in Carrying Amounts of Non-Marketable Equity Securities

A summary of the changes in the carrying amounts of non-marketable equity securities, which primarily relate to the Company's venture investment portfolio, for the three and six months ended June 30, 2025 and 2024, is as follows:

	Three Months Ended June 30,					Six Months Ended June 30,
(in millions)	2025		2024			2025			2024
Carrying amount, beginning of period	$	216.6	$	226.1		$	202.4		$	224.1
Net additions		0.2		1.3			15.2			3.1
Gross unrealized gains		1.5		1.2			1.5			1.4
Gross unrealized losses and impairments		—		(2.8	)		(0.8	)		(2.8	)
Carrying amount, end of period	$	218.3	$	225.8		$	218.3		$	225.8

Summary of Cumulative Gross Unrealized Gains and Cumulative Gross Unrealized Losses and Impairments

Cumulative gross unrealized gains and cumulative gross unrealized losses and impairments related to non-marketable equity securities at June 30, 2025 and December 31, 2024, are summarized as follows:

(in millions)	June 30, 2025		December 31, 2024
Cumulative gross unrealized gains	$	246.3	$	244.8
Cumulative gross unrealized losses and impairments	$	352.4	$	351.6