Schedule II Condensed Financial Information of Registrant - Condensed Statements of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Revenues
Net investment income	$ 445.7	$ 444.8	$ 400.9	[1]
Net investment losses	(17.3)	(24.0)	(56.5)	[1]
Revenues, Total	1,595.2	1,491.9	1,381.6	[1]
Expenses
Interest expense	34.6	29.7	19.4	[1]
Total benefits, losses and expenses	1,466.6	1,438.6	1,365.1	[1]
Income tax benefit	25.8	8.3	(3.3)	[1]
Net income	102.8	45.0	19.8	[1]
Parent company
Revenues
Net investment income	0.1	0.2	0.0
Revenues, Total	0.1	0.2	0.0
Expenses
Interest expense	34.6	29.7	19.4
Other	8.1	5.1	8.4
Total benefits, losses and expenses	42.7	34.8	27.8
Loss before income tax benefit and equity in net earnings of subsidiaries	(42.6)	(34.6)	(27.8)
Income tax benefit	(9.6)	(6.9)	(6.3)
Loss before equity in net earnings of subsidiaries	(33.0)	(27.7)	(21.5)
Equity in net earnings (losses) of subsidiaries	135.8	72.7	41.3
Net income	$ 102.8	$ 45.0	$ 19.8

[1] Recast for the adoption of ASU 2018-12.