Equity Securities (Tables)

3 Months Ended

Mar. 31, 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)	March 31, 2025		December 31, 2024
Marketable equity securities	$	367.4	$	386.8
Non-marketable equity securities		216.6		202.4
Equity method investments		102.7		102.1
	$	686.7	$	691.3

Summary of Investments in Marketable Equity Securities

Investments in marketable equity securities are summarized as follows:

(in millions)	Cost		Unrealized losses			Estimated fair value
March 31, 2025
Common stocks	$	390.9	$	(35.6	)	$	355.3
Preferred stocks		12.0		0.1			12.1
	$	402.9	$	(35.5	)	$	367.4
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 months ended March 31, 2025 and 2024, is as follows:

	Three Months Ended March 31,
(in millions)	2025			2024
Carrying amount, beginning of period	$	202.4		$	224.1
Net additions		15.0			1.8
Gross unrealized gains		—			0.2
Gross unrealized losses and impairments		(0.8	)		—
Carrying amount, end of period	$	216.6		$	226.1

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 March 31, 2025 and December 31, 2024, are summarized as follows:

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