Schedule IV Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Life insurance in force
Gross Amount	$ 37,107.3	$ 40,422.9	$ 38,564.6
Ceded to Other Companies	10,012.3	9,597.7	9,330.9
Assumed from Other Companies	0.0	0.0	0.0
Net Amount	$ 27,095.0	$ 30,825.2	$ 29,233.7
Percentage of Amount Assumed to Net	0.00%	0.00%	0.00%
Premiums
Gross Amount	$ 1,188.8	$ 1,097.6	$ 1,046.7
Ceded to Other Companies	70.9	76.3	72.0
Assumed from Other Companies	28.1	35.8	53.0
Net Amount	$ 1,146.0	$ 1,057.1	$ 1,027.7
Percentage of Amount Assumed to Net	2.50%	3.40%	5.20%
Property & Casualty
Premiums
Gross Amount	$ 743.9	$ 653.0	$ 614.7
Ceded to Other Companies	20.5	18.1	15.0
Assumed from Other Companies	13.1	10.7	8.5
Net Amount	$ 736.5	$ 645.6	$ 608.2
Percentage of Amount Assumed to Net	1.80%	1.70%	1.40%
Life & Retirement
Premiums
Gross Amount	$ 161.2	$ 166.5	$ 158.9
Ceded to Other Companies	6.6	14.8	14.9
Assumed from Other Companies	0.0	0.0	0.0
Net Amount	$ 154.6	$ 151.7	$ 144.0
Percentage of Amount Assumed to Net	0.00%	0.00%	0.00%
Supplemental & Group Benefits
Premiums
Gross Amount	$ 283.7	$ 278.1	$ 273.1
Ceded to Other Companies	43.8	43.4	42.1
Assumed from Other Companies	15.0	25.1	44.5
Net Amount	$ 254.9	$ 259.8	$ 275.5
Percentage of Amount Assumed to Net	5.90%	9.70%	16.20%