Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2024

Equity [Abstract]

Summary of Components of Changes in Accumulated Other Comprehensive Income (AOCI)

Changes in AOCI, net of taxes, by component follows (dollars in millions). Amounts in parentheses indicate losses.

	Unrealized Loss On Foreign Exchange Contracts			Unrealized (Loss) Gain on Marketable Debt Securities			Unfunded Employee Benefit Obligations			Total
Balance at January 1, 2023	$	(0.2	)	$	(1.9	)	$	(100.3	)	$	(102.4	)
Other comprehensive income before reclassifications		—			1.8			23.2			25.0
Amounts reclassified from AOCI		0.1			—			6.4			6.5
Net current-period other comprehensive income		0.1			1.8			29.6			31.5
Balance at December 31, 2023	$	(0.1	)	$	(0.1	)	$	(70.7	)	$	(70.9	)
Other comprehensive income before reclassifications		—			0.3			23.1			23.4
Amounts reclassified from AOCI		—			—			4.1			4.1
Net current-period other comprehensive income		—			0.3			27.2			27.5
Balance at December 31, 2024	$	(0.1	)	$	0.2		$	(43.5	)	$	(43.4	)

Summary of Reclassifications Out of Accumulated Other Comprehensive Income (AOCI)

The following table presents information about reclassifications out of AOCI (dollars in millions). Amounts in parentheses indicate expenses in the Consolidated Statements of Income.

	Amounts Reclassified from AOCI Year Ended December 31,
Details about AOCI Components	2024			2023
Unfunded employee benefit obligations (a)
Amortization of prior service costs	$	(5.1	)	$	(4.8	)
Amortization of actuarial gains / (losses)		(0.4	)		(3.7	)
		(5.5	)		(8.5	)	Total before tax
		1.4			2.1		Tax benefit
	$	(4.1	)	$	(6.4	)	Net of tax

(a)These AOCI components are included in the computation of net pension and postretirement benefit costs. See Note 12, Employee Benefit Plans and Other Postretirement Benefits, for additional information.