Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues
Premiums	$ 1,186.0	$ 1,135.4	$ 3,527.6	$ 3,373.4
Net investment income	78.8	67.6	231.2	194.9
Net realized and unrealized investment gains (losses):
Net realized gains from sales and other	3.6	8.2	6.8	12.1
Net change in fair value of equity securities	0.3	30.3	65.9	(44.4)
Impairment recoveries (losses) on investments	0.1	(0.8)	(0.1)	(27.9)
Total net realized and unrealized investment gains (losses)	4.0	37.7	72.6	(60.2)
Fees and other income	7.6	9.1	21.7	22.2
Total revenues	1,276.4	1,249.8	3,853.1	3,530.3
Losses and expenses
Losses and loss adjustment expenses	844.0	709.7	2,370.4	2,149.9
Amortization of deferred acquisition costs	244.0	237.7	728.5	711.9
Interest expense	8.5	9.8	25.5	28.6
Loss from repayment of debt		6.1		6.2
Other operating expenses	137.4	137.9	412.2	395.9
Total losses and expenses	1,233.9	1,101.2	3,536.6	3,292.5
Income from continuing operations before income taxes	42.5	148.6	316.5	237.8
Income tax expense (benefit):
Current	9.9	29.9	47.1	69.7
Deferred	(2.2)	(0.8)	12.2	(28.0)
Total income tax expense	7.7	29.1	59.3	41.7
Income from continuing operations	34.8	119.5	257.2	196.1
Discontinued operations (net of taxes):
Net income	$ 34.0	$ 118.9	$ 255.2	$ 194.1
Basic:
Income from continuing operations	$ 0.98	$ 3.17	$ 7.14	$ 5.16
Net income per share	$ 0.95	$ 3.15	$ 7.09	$ 5.11
Weighted average shares outstanding	35.7	37.7	36.0	38.0
Diluted:
Income from continuing operations	$ 0.96	$ 3.14	$ 7.04	$ 5.11
Net income per share	$ 0.94	$ 3.13	$ 6.98	$ 5.05
Weighted average shares outstanding	36.3	38.0	36.6	38.4
Life [Member]
Discontinued operations (net of taxes):
Income (Loss) from discontinued operations	$ (0.8)	$ (0.6)	$ (2.0)	$ (2.0)
Basic:
Loss from discontinued operations	$ (0.03)	$ (0.02)	$ (0.05)	$ (0.05)
Diluted:
Income (Loss) from discontinued operations	$ (0.02)	$ (0.01)	$ (0.06)	$ (0.06)