Consolidated Statements of Income (Loss) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues
Premiums	$ 1,431.1	$ 1,331.2	$ 4,222.8	$ 3,888.8
Net investment income	84.2	73.0	250.5	220.4
Net realized and unrealized investment gains (losses):
Net realized losses from sales and other	(0.9)	(0.1)	(1.9)	(16.3)
Net change in fair value of equity securities	(5.2)	(29.1)	(13.4)	(106.1)
Impairments on investments:
Credit related impairments		(1.4)	(6.2)	(1.5)
Losses on intent to sell securities		(14.3)	(10.3)	(14.8)
Impairments on investments		(15.7)	(16.5)	(16.3)
Total net realized and unrealized investment losses	(6.1)	(44.9)	(31.8)	(138.7)
Fees and other income	7.4	7.0	23.2	19.4
Total revenues	1,516.6	1,366.3	4,464.7	3,989.9
Losses and expenses
Losses and loss adjustment expenses	1,061.5	939.6	3,218.8	2,572.6
Amortization of deferred acquisition costs	296.6	277.1	878.1	809.3
Interest expense	8.5	8.5	25.6	25.5
Other operating expenses	150.9	140.6	451.3	423.8
Total losses and expenses	1,517.5	1,365.8	4,573.8	3,831.2
Income (loss) from continuing operations before income taxes	(0.9)	0.5	(109.1)	158.7
Income tax expense (benefit):
Current	(1.1)	12.9	(13.7)	72.5
Deferred	(8.0)	(13.0)	(21.6)	(42.5)
Total income tax expense (benefit)	(9.1)	(0.1)	(35.3)	30.0
Income (loss) from continuing operations	8.2	0.6	(73.8)	128.7
Discontinued operations (net of taxes):
Net income (loss)	$ 8.6	$ 0.5	$ (72.6)	$ 128.1
Basic:
Income (loss) from continuing operations	$ 0.23	$ 0.02	$ (2.07)	$ 3.62
Net income (loss) per share	$ 0.24	$ 0.01	$ (2.03)	$ 3.6
Weighted average shares outstanding	35.8	35.6	35.7	35.6
Diluted:
Income (loss) from continuing operations	$ 0.23	$ 0.02	$ (2.07)	$ 3.56
Net income (loss) per share	$ 0.24	$ 0.01	$ (2.03)	$ 3.54
Weighted average shares outstanding	36.1	36.1	35.7	36.1
Life [Member]
Discontinued operations (net of taxes):
Income (loss) from discontinued businesses		$ (0.1)		$ (0.6)
Basic:
Income (loss) from discontinued businesses, Basic		$ (0.01)		$ (0.02)
Diluted:
Income (loss) from discontinued businesses, Diluted		$ (0.01)		$ (0.02)
Chaucer [Member]
Discontinued operations (net of taxes):
Income (loss) from discontinued businesses	$ 0.4		$ 1.2
Basic:
Income (loss) from discontinued businesses, Basic	$ 0.01		$ 0.04
Diluted:
Income (loss) from discontinued businesses, Diluted	$ 0.01		$ 0.04