Other Comprehensive Income (Loss) (Reclassifications out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) from sales and other	$ 3.1	$ (0.4)
Income (loss) from continuing operations before income taxes	(53.9)	148.6
Loss adjustment expenses and other operating expenses	(728.2)	(699.6)
Tax benefit	15.2	(26.0)
Income (loss) from continuing operations	(38.7)	122.6
Net income (loss)	(40.0)	122.4
Life [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Discontinued operations - life businesses	(1.3)	(0.8)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	(14.8)	1.3
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Net Unrealized Appreciation (Depreciation) on Investments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) from sales and other	3.1	(0.3)
Impairment losses on investments	(22.2)
Income (loss) from continuing operations before income taxes	(19.1)	(0.3)
Tax benefit	5.9	3.9
Income (loss) from continuing operations	(13.2)	3.6
Net income (loss)	(13.6)	3.6
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Net Unrealized Appreciation (Depreciation) on Investments [Member] \| Life [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Discontinued operations - life businesses	(0.4)
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Defined Benefit Pension and Postretirement Plans [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss adjustment expenses and other operating expenses	(1.5)	(2.9)
Tax benefit	0.3	0.6
Income (loss) from continuing operations	$ (1.2)	$ (2.3)

Amount after tax of income (loss) from continuing operations attributable to the parent.

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