Schedule 4 - Reinsurance Schedule (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Life Insurance in Force
Gross Amount	$ 19,885.1	$ 20,287.7	$ 19,706.2
Ceded to Other Companies	354.8	372.3	387.7
Assumed from Other Companies	137.1	144.5	152.3
Net Amount	$ 19,667.4	$ 20,059.9	$ 19,470.8
Percentage of Amount Assumed to Net	0.70%	0.70%	0.80%
Premiums
Gross Amount	$ 5,282.7	$ 5,255.1	$ 4,652.6
Ceded to Other Companies	42.7	36.1	31.2
Assumed from Other Companies	26.3	34.7	50.8
Net Amount	$ 5,266.3	$ 5,253.7	$ 4,672.2
Percentage of Amount Assumed to Net	0.50%	0.70%	1.10%
Life Insurance
Premiums
Gross Amount	$ 408.7	$ 401.9	$ 386.0
Ceded to Other Companies	3.6	0.9	1.1
Assumed from Other Companies	0.6	0.7	0.8
Net Amount	$ 405.7	$ 401.7	$ 385.7
Percentage of Amount Assumed to Net	0.10%	0.20%	0.20%
Accident and Health Insurance
Premiums
Gross Amount	$ 167.9	$ 185.8	$ 195.5
Ceded to Other Companies	1.1	0.3	1.6
Assumed from Other Companies	1.4	4.4	5.4
Net Amount	$ 168.2	$ 189.9	$ 199.3
Percentage of Amount Assumed to Net	0.80%	2.30%	2.70%
Property and Liability Insurance
Premiums
Gross Amount	$ 4,706.1	$ 4,667.4	$ 4,071.1
Ceded to Other Companies	38.0	34.9	28.5
Assumed from Other Companies	24.3	29.6	44.6
Net Amount	$ 4,692.4	$ 4,662.1	$ 4,087.2
Percentage of Amount Assumed to Net	0.50%	0.60%	1.10%