Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues
Premiums	$ 1,179.8	$ 1,096.6	$ 2,341.6	$ 2,238.0
Net investment income	75.6	57.7	152.4	127.3
Net realized and unrealized investment gains (losses):
Net realized gains from sales and other	4.8	0.8	3.2	3.9
Net change in fair value of equity securities	26.5	61.5	65.6	(74.7)
Impairment recoveries (losses) on investments	(0.2)	1.4	(0.2)	(27.1)
Total net realized and unrealized investment gains (losses)	31.1	63.7	68.6	(97.9)
Fees and other income	6.9	6.3	14.1	13.1
Total revenues	1,293.4	1,224.3	2,576.7	2,280.5
Losses and expenses
Losses and loss adjustment expenses	745.1	712.0	1,526.4	1,440.2
Amortization of deferred acquisition costs	244.2	237.3	484.5	474.2
Interest expense	8.5	9.4	17.0	18.8
Other operating expenses	135.7	122.5	274.8	258.1
Total losses and expenses	1,133.5	1,081.2	2,302.7	2,191.3
Income from continuing operations before income taxes	159.9	143.1	274.0	89.2
Income tax expense (benefit):
Current	28.3	18.5	37.2	39.8
Deferred	2.0	9.3	14.4	(27.2)
Total income tax expense	30.3	27.8	51.6	12.6
Income from continuing operations	129.6	115.3	222.4	76.6
Discontinued operations (net of taxes):
Net income	$ 128.5	$ 115.2	$ 221.2	$ 75.2
Basic:
Income from continuing operations	$ 3.60	$ 3.03	$ 6.15	$ 2.01
Net income per share	$ 3.58	$ 3.03	$ 6.12	$ 1.97
Weighted average shares outstanding	35.9	38.0	36.2	38.2
Diluted:
Income from continuing operations	$ 3.55	$ 3.01	$ 6.06	$ 1.98
Net income per share	$ 3.52	$ 3.01	$ 6.03	$ 1.95
Weighted average shares outstanding	36.5	38.3	36.7	38.6
Life [Member]
Discontinued operations (net of taxes):
Income (Loss) from discontinued operations	$ (1.1)	$ (0.1)	$ (1.2)	$ (1.4)
Basic:
Loss from discontinued operations	$ (0.02)		$ (0.03)	$ (0.04)
Diluted:
Income (Loss) from discontinued operations	$ (0.03)		$ (0.03)	$ (0.03)