Prior Period Consolidated Financial Statements - Schedule of Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net premiums and contract charges earned	$ 259.1	$ 257.4	$ 255.4	$ 255.8	$ 210.6	$ 225.2	$ 225.6	$ 227.4	$ 1,057.1	$ 1,027.7		$ 888.8
Insurance premiums written and contract deposits	358.2	372.7	359.9	346.2	314.0	346.2	334.2	304.4	1,552.6	1,489.1		1,359.9
Revenues	346.4	342.6	345.9	346.7	331.2	329.4	346.9	321.7	1,491.9	1,381.6	[1]	1,329.3	[1]
Net income	$ (16.7)	$ 20.4	$ (4.2)	$ 20.3	$ 46.9	$ 20.2	$ 54.2	$ 49.1	$ 45.0	$ 19.8	[1],[2]	$ 170.4	[1],[2]
Basic
Net income - basic (in usd per share)	$ (0.40)	$ 0.49	$ (0.10)	$ 0.48	$ 1.12	$ 0.48	$ 1.29	$ 1.17	$ 1.09	$ 0.48	[1]	$ 4.06	[1]
Shares of common stock - weighted average basic (in shares)	41.4	41.4	41.8	41.9	42.0	42.0	42.0	41.9	41.3	41.6	[1]	42.0	[1]
Diluted
Net income - diluted (in usd per share)	$ (0.40)	$ 0.49	$ (0.10)	$ 0.48	$ 1.11	$ 0.48	$ 1.29	$ 1.16	$ 1.09	$ 0.47	[1]	$ 4.04	[1]
Shares of common stock and equivalent shares - weighted average diluted (in shares)	41.4	41.6	41.8	42.1	42.2	42.2	42.2	42.1	41.4	41.8	[1]	42.2	[1]

[1] Recast for the adoption of ASU 2018-12. See Note 1 of the Consolidated Financial Statements

[2] Recast for the adoption of ASU 2018-12. See Note 1 of the Consolidated Financial Statements