Reinsurance - Summary of Reinsurance Activity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Gross Amount
Premiums written and contract deposits, Gross Amount	$ 320.6	$ 333.7
Premiums and contract charges earned, Gross Amount	234.2	243.2
Benefits, claims and settlement expenses, Gross Amount	135.6	139.5
Ceded to Other Companies
Premiums written and contract deposits, Ceded to Other Companies	5.9	6.3
Premiums and contract charges earned, Ceded to Other Companies	8.4	8.4
Benefits, claims and settlement expenses, Ceded to Other Companies	2.5	1.9
Assumed from Other Companies
Premiums written and contract deposits, Assumed from Other Companies	1.5	1.4
Premiums and contract charges earned, Assumed from Other Companies	1.8	1.5
Benefits, claims and settlement expenses, Assumed from Other Companies	1.2	1.1
Net Amount
Premiums written and contract deposits, Net Amount	316.2	328.8
Premiums and contract charges earned, Net Amount	227.6	236.3
Benefits, claims and settlement expenses, Net Amount	$ 134.3	$ 138.7