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Debt (Tables)

9 Months Ended

Sep. 30, 2025

Debt Disclosure [Abstract]

Schedule of Debt

The following table summarizes the Company’s Debt:

	December 31, 2024		September 30, 2025
Senior bank debt	$—		$100.0
Senior notes	1,092.1		743.1
Junior subordinated notes	1,189.0		1,189.3
Junior convertible securities	339.1		339.2
Debt	$2,620.2		$2,371.6

Schedule of Principal Terms of Senior and Junior Subordinated Notes

The principal terms of the senior

notes outstanding as of September 30, 2025 are presented and described below:

		2030 Senior Notes		2034 Senior Notes
Issue date		June 2020		August 2024
Maturity date		June 2030		August 2034
Par value (in millions)		$350.0		$400.0
Stated coupon		3.30%		5.50%
Coupon frequency		Semi-annually		Semi-annually
Call price		As defined		As defined

As of September 30, 2025, the Company had junior subordinated notes outstanding, the respective principal terms of which

are presented and described below:

		2059 Junior Subordinated Notes		2060 Junior Subordinated Notes		2061 Junior Subordinated Notes		2064 Junior Subordinated Notes
Issue date		March 2019		September 2020		July 2021		March 2024
Maturity date		March 2059		September 2060		September 2061		March 2064
Par value (in millions)		$300.0		$275.0		$200.0		$450.0
Stated coupon		5.875%		4.75%		4.20%		6.75%
Coupon frequency		Quarterly		Quarterly		Quarterly		Quarterly
Call price		As defined		As defined		As defined		As defined
NYSE Symbol		MGR		MGRB		MGRD		MGRE

Schedule of Convertible Securities

The following table presents interest expense recorded in connection with the junior convertible securities:

		For the Three Months Ended September 30,				For the Nine Months Ended September 30,
		2024		2025		2024		2025
Contractual interest expense		$4.4		$4.4		$13.2		$13.2
Amortization of debt issuance costs		0.1		0.1		0.2		0.2
Total		$4.5		$4.5		$13.4		$13.4
Effective interest rate		5.21%		5.21%		5.21%		5.21%

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Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

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