Debt and Credit Arrangements (Tables)

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Schedule of Debt

Debt consists of the following:

DECEMBER 31	2020			2019
(in millions)
Senior debentures maturing April 15, 2026	$	375.0		$	375.0
Senior debentures maturing September 1, 2030		300.0			—
Senior debentures maturing October 15, 2025		61.8			62.6
Subordinated debentures maturing February 3, 2027		50.1			50.1
Subordinated debentures maturing March 30, 2053		—			175.0
Total principal debt		786.9			662.7
Unamortized debt issuance costs		(6.1	)		(9.3	)
Total	$	780.8		$	653.4