Debt (Tables)

12 Months Ended

Dec. 31, 2025

Debt Disclosure [Abstract]

Schedule of Debt

Debt consists of the following:

			December 31
			2025		2024
	Interest Rates	Maturities	(in millions of dollars)
Long-term Debt
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 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
Senior Notes issued 2024	4.046%	2041	400.0		400.0
Senior Notes issued 2024	6.000%	2054	400.0		400.0
Senior Notes issued 2025	5.250%	2035	300.0		—
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
Unamortized Net Discount			(129.2)		(131.3)
Unamortized Debt Issuance Costs			(36.7)		(37.0)
Total Long-term Debt			$	3,767.6	$	3,465.2
Short-term Debt
Outstanding Principal
Senior Notes issued 2015	3.875%	2025	—		275.0
Unamortized Net Discount			—		(0.2)
Unamortized Debt Issuance Costs			—		(0.2)
Total Short-term Debt			—		274.6
Total Debt			$	3,767.6	$	3,739.8