Schedule II - Condensed Financial Information of Registrant Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Investment income from subsidiaries									$ 578.3	$ 459.5	$ 434.3
Realized Investment Gains Losses From Sales									(15.2)	185.7	6.9
Total revenues	$ 1,941.1	$ 1,760.1	$ 1,798.3	$ 1,758.7	$ 2,345.5	$ 1,721.0	$ 1,810.3	$ 2,206.6	7,258.3	8,083.7	9,341.6
Expenses:
Federal income taxes (credits)									148.7	170.9	387.7
Net Income	$ 190.6	$ 52.6	$ 155.5	$ 199.8	$ 512.1	$ (91.7)	$ (40.1)	$ 306.3	598.6	686.4	1,534.3
Parent Company [Member]
Revenues:
Investment income from subsidiaries									122.0	118.0	100.3
Real estate and other income									4.1	4.2	4.3
Other investment income									4.8	1.2	0.2
Realized Investment Gains Losses From Sales									(4.5)	0.0	0.0
Total revenues									126.5	123.6	104.9
Expenses:
Interest - subsidiaries									4.2	3.9	3.9
Interest - other									67.1	67.1	55.9
Real estate and other expenses									4.8	4.5	4.7
General expenses, taxes and fees									57.1	23.6	17.4
Total expenses									133.3	99.2	82.0
Revenues, net of expenses									(6.8)	24.3	22.8
Federal income taxes (credits)									(0.8)	2.9	(0.9)
Income (loss) before equity in earnings (losses) of subsidiaries									(5.9)	21.3	23.7
Dividends received									673.3	614.6	566.7
Earnings (losses) in excess of dividends									(68.6)	50.5	943.8
Net Income									$ 598.6	$ 686.4	$ 1,534.3