Debt and Credit Arrangements (Tables)

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Schedule of Debt

Debt consists of the following:

DECEMBER 31	2023			2022
(in millions)
Senior debentures maturing April 15, 2026	$	375.0		$	375.0
Senior debentures maturing September 1, 2030		300.0			300.0
Senior debentures maturing October 15, 2025		61.8			61.8
Subordinated debentures maturing February 3, 2027		50.1			50.1
Total principal debt		786.9			786.9
Unamortized debt issuance costs		(3.7	)		(4.5	)
Total	$	783.2		$	782.4