SCHEDULE II - Condensed Financial Information of Registrant (Parent Company) - Statement of Operations (Details) - USD ($) $ 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, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues:
Net investment income									$ 1,015.9	$ 1,420.7	$ 1,222.5
Total investment gains (losses)									(17.9)	21.3	(18.4)
Total revenues	$ 973.6	$ 905.3	$ 855.0	$ 842.9	$ 1,074.8	$ 968.3	$ 1,073.1	$ 1,006.0	3,576.8	4,122.2	3,821.1
Expenses:
Interest expense									137.0	95.4	108.8
Income tax benefit	12.0	32.2	39.3	37.0	32.3	28.2	23.6	42.6	120.5	126.7	42.5
Net income	$ 43.4	$ 105.0	$ 136.1	$ 112.3	$ 115.8	$ 99.8	$ 78.0	$ 147.4	396.8	441.0	301.8
Parent Company
Revenues:
Net investment income									9.8	7.4	28.7
Net investment income - affiliated									3.0	0.3	0.8
Total investment gains (losses)									(0.6)	(0.2)	0.2
Total revenues									12.2	7.5	29.7
Expenses:
Interest expense									62.5	62.4	55.2
Intercompany expenses (eliminated in consolidation)									3.8	0.5	1.1
Operating costs and expenses									0.2	38.5	65.9
Total expenses									66.5	101.4	122.2
Income before income taxes									(54.3)	(93.9)	(92.5)
Income tax benefit									(18.3)	(26.0)	(28.2)
Loss before equity in undistributed earnings of subsidiaries									(36.0)	(67.9)	(64.3)
Equity in undistributed earnings of subsidiaries (eliminated in consolidation)									432.8	508.9	366.1
Net income									$ 396.8	$ 441.0	$ 301.8