Long-Duration Insurance Contracts - Policyholder Account Balances (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Policyholder Account Balance [Roll Forward]
Beginning balance	$ 5,100.3
Interest credited	216.9	$ 215.9	$ 205.7
Ending balance	5,064.1	5,100.3
Indexed Universal Life
Policyholder Account Balance [Roll Forward]
Beginning balance	72.9	57.8
Premiums received	25.8	17.8
Surrenders and withdrawals	(2.2)	(2.2)
Benefit payments	0.0	0.0
Net transfers from (to) separate account	(0.5)	(0.2)
Interest credited	4.6	3.9
Other	(5.1)	(4.2)
Ending balance	$ 95.5	$ 72.9	57.8
Weighted-average crediting rate	5.60%	6.10%
Net amount at risk	$ 0.0	$ 0.0
Cash surrender value	73.7	54.5
Experience Life
Policyholder Account Balance [Roll Forward]
Beginning balance	58.0	61.2
Premiums received	(0.9)	(0.8)
Surrenders and withdrawals	(3.7)	(3.7)
Benefit payments	(1.4)	(1.6)
Net transfers from (to) separate account	0.0	0.0
Interest credited	2.8	2.9
Other	0.0	0.0
Ending balance	$ 54.8	$ 58.0	61.2
Weighted-average crediting rate	5.00%	5.00%
Net amount at risk	$ 0.0	$ 0.0
Cash surrender value	54.2	57.4
Fixed Account Annuities
Policyholder Account Balance [Roll Forward]
Beginning balance	4,508.4	4,556.0
Premiums received	202.2	203.5
Surrenders and withdrawals	(363.8)	(388.6)
Benefit payments	(76.7)	(69.2)
Net transfers from (to) separate account	28.4	23.3
Interest credited	171.4	167.7
Other	16.9	15.7
Ending balance	$ 4,486.8	$ 4,508.4	4,556.0
Weighted-average crediting rate	3.90%	3.80%
Net amount at risk	$ 23.4	$ 29.4
Cash surrender value	4,443.1	4,452.6
Fixed Indexed Account Annuities
Policyholder Account Balance [Roll Forward]
Beginning balance	409.5	449.0
Premiums received	14.7	15.9
Surrenders and withdrawals	(44.1)	(51.2)
Benefit payments	(4.1)	(4.2)
Net transfers from (to) separate account	(0.9)	(2.2)
Interest credited	13.5	16.1
Other	(15.3)	(13.9)
Ending balance	$ 373.3	$ 409.5	449.0
Weighted-average crediting rate	3.50%	3.80%
Net amount at risk	$ 0.0	$ 0.0
Cash surrender value	368.7	402.0
SPIA (non-life contingent)
Policyholder Account Balance [Roll Forward]
Beginning balance	28.6	32.6
Premiums received	1.9	1.9
Surrenders and withdrawals	(0.5)	(1.3)
Benefit payments	(4.7)	(5.5)
Net transfers from (to) separate account	0.0	0.0
Interest credited	0.9	0.9
Other	(0.1)	0.0
Ending balance	$ 26.1	$ 28.6	$ 32.6
Weighted-average crediting rate	3.50%	3.10%
Net amount at risk	$ 0.0	$ 0.0
Cash surrender value	$ 25.8	$ 28.3