Reinsurance - Summary of Reinsurance Activity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Gross Amount
Premiums written and contract deposits, Gross Amount	$ 351.2	$ 332.4	$ 671.8	$ 666.1
Premiums and contract charges earned, Gross Amount	231.5	230.6	465.7	473.8
Benefits, claims and settlement expenses, Gross Amount	144.6	143.3	280.2	282.8
Ceded to Other Companies
Premiums written and contract deposits, Ceded to Other Companies	5.6	6.4	11.5	12.7
Premiums and contract charges earned, Ceded to Other Companies	8.1	8.3	16.5	16.7
Benefits, claims and settlement expenses, Ceded to Other Companies	(1.0)	2.4	1.5	4.3
Assumed from Other Companies
Premiums written and contract deposits, Assumed from Other Companies	2.5	3.1	4.0	4.5
Premiums and contract charges earned, Assumed from Other Companies	2.4	3.1	4.2	4.6
Benefits, claims and settlement expenses, Assumed from Other Companies	1.5	2.1	2.7	3.2
Net Amount
Premiums written and contract deposits, Net Amount	348.1	329.1	664.3	657.9
Premiums and contract charges earned, Net Amount	225.8	225.4	453.4	461.7
Benefits, claims and settlement expenses, Net Amount	$ 147.1	$ 143.0	$ 281.4	$ 281.7