Debt (Tables)

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Schedule of Debt

Debt consists of the following:

			December 31
			2023		2022
	Interest Rates	Maturities	(in millions of dollars)
Outstanding Principal
Senior Notes issued 1998	6.750 - 7.250%	2028	$	335.8	$	335.8
Senior Notes issued 2002	7.375%	2032	39.5		39.5
Senior Notes issued 2012 and 2016	5.750%	2042	500.0		500.0
Senior Notes issued 2015	3.875%	2025	275.0		275.0
Senior Notes issued 2019	4.000%	2029	400.0		400.0
Senior Notes issued 2019	4.500%	2049	450.0		450.0
Senior Notes issued 2021	4.125%	2051	600.0		600.0
Medium-term Notes issued 1990 - 1996	7.190%	2028	18.5		18.5
Junior Subordinated Debt Securities issued 1998	7.405%	2038	189.7		189.7
Junior Subordinated Debt Securities issued 2018	6.250%	2058	300.0		300.0
Term Loan issued 2022	Variable	2027	350.0		350.0
Less:
Unamortized Net Premium			2.5		2.5
Unamortized Debt Issuance Costs			(30.6)		(33.2)
Total Long-term Debt			$	3,430.4	$	3,427.8
Short-term Debt
Medium-term Notes Issued 1990	7.000%	2023	—		2.0
Total Debt			$	3,430.4	$	3,429.8