Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenues
Premiums	$ 1,293.8	$ 1,179.8	$ 2,557.6	$ 2,341.6
Net investment income	70.5	75.6	147.4	152.4
Net realized and unrealized investment gains (losses):
Net realized gains (losses) from sales and other	(19.2)	4.8	(16.2)	3.2
Net change in fair value of equity securities	(59.0)	26.5	(77.0)	65.6
Recoveries (impairments) on investments	0.3	(0.2)	(0.6)	(0.2)
Total net realized and unrealized investment gains (losses)	(77.9)	31.1	(93.8)	68.6
Fees and other income	6.5	5.8	12.4	11.8
Total revenues	1,292.9	1,292.3	2,623.6	2,574.4
Losses and expenses
Losses and loss adjustment expenses	845.5	745.1	1,633.0	1,526.4
Amortization of deferred acquisition costs	269.3	244.2	532.2	484.5
Interest expense	8.5	8.5	17.0	17.0
Other operating expenses	141.4	134.6	283.2	272.5
Total losses and expenses	1,264.7	1,132.4	2,465.4	2,300.4
Income from continuing operations before income taxes	28.2	159.9	158.2	274.0
Income tax expense (benefit):
Current	29.4	28.3	59.6	37.2
Deferred	(24.0)	2.0	(29.5)	14.4
Total income tax expense	5.4	30.3	30.1	51.6
Income from continuing operations	22.8	129.6	128.1	222.4
Discontinued operations (net of taxes):
Net income	$ 22.6	$ 128.5	$ 127.4	$ 221.2
Basic:
Income from continuing operations	$ 0.64	$ 3.60	$ 3.60	$ 6.15
Net income per share	$ 0.64	$ 3.58	$ 3.58	$ 6.12
Weighted average shares outstanding	35.6	35.9	35.6	36.2
Diluted:
Income from continuing operations	$ 0.63	$ 3.55	$ 3.55	$ 6.06
Net income per share	$ 0.63	$ 3.52	$ 3.52	$ 6.03
Weighted average shares outstanding	36.1	36.5	36.1	36.7
Life [Member]
Discontinued operations (net of taxes):
Loss from discontinued life businesses	$ (0.2)	$ (1.1)	$ (0.7)	$ (1.2)
Basic:
Loss from discontinued operations		$ (0.02)	$ (0.02)	$ (0.03)
Diluted:
Income (Loss) from discontinued operations		$ (0.03)	$ (0.03)	$ (0.03)