Property and Casualty Insurance Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Beginning Property and Casualty Insurance Reserves: [Abstract]
Gross of Reinsurance and Indemnification at Beginning of Year	$ 1,016.8	$ 931.4	$ 862.8
Less Reinsurance Recoverables and Indemnification at Beginning of Year	111.6
Property and Casualty Insurance Reserves, Net of Reinsurance at Beginning of Year	963.7	881.2	810.8
Property and Casualty Insurance Reserves Acquired, Net of Reinsurance				$ 695.1	$ 0.0	$ 0.0
Incurred Losses and LAE related to:
Prior Years - Incurred Losses and LAE	(7.4)	18.9	(20.7)
Total Incurred Losses and LAE	2,086.0	1,473.0	1,337.9
Paid Losses and LAE related to:
Prior Years - Paid Losses and LAE	671.0	522.4	436.5
Total Paid Losses and LAE	1,971.8	1,390.5	1,267.5
Property and Casualty Insurance Reserves, Net of Reinsurance and Indemnification at End of Year	963.7	881.2	810.8	$ 1,773.0	$ 963.7	$ 881.2
Plus Reinsurance and Indemnification Recoverables at End of Year	158.3	111.6
Property and Casualty Insurance Reserves, Gross of Reinsurance at End of Year	1,874.9	1,016.8	931.4
Continuing Operations [Member]
Incurred Losses and LAE related to:
Current Year - Incurred Losses and LAE	2,093.4	1,454.1	1,358.6
Prior Years - Incurred Losses and LAE	(5.2)	20.4	(14.4)
Paid Losses and LAE related to:
Current Year - Paid Losses and LAE	1,300.8	868.1	831.0
Prior Years - Paid Losses and LAE	668.2	518.5	431.9
Discontinued Operations [Member]
Incurred Losses and LAE related to:
Prior Years - Incurred Losses and LAE	(2.2)	(1.5)	(6.3)
Paid Losses and LAE related to:
Prior Years - Paid Losses and LAE	2.8	3.9	4.6
Catastrophe [Member]
Incurred Losses and LAE related to:
Prior Years - Incurred Losses and LAE	(8.4)	(4.5)	(19.3)
Total Incurred Losses and LAE	87.6	180.4	95.8
Property and Casualty Insurance [Member]
Beginning Property and Casualty Insurance Reserves: [Abstract]
Less Reinsurance Recoverables and Indemnification at Beginning of Year	53.1	50.2	52.0
Paid Losses and LAE related to:
Plus Reinsurance and Indemnification Recoverables at End of Year	101.9	53.1	50.2
Property and Casualty, Personal Insurance Product Line [Member]
Incurred Losses and LAE related to:
Prior Years - Incurred Losses and LAE	(1.4)	19.5	(16.8)
Property and Casualty, Commercial Insurance Product Line [Member]
Incurred Losses and LAE related to:
Prior Years - Incurred Losses and LAE	(6.1)	(0.6)	(3.9)
Property and Casualty, Commercial Insurance Product Line [Member] | Continuing Operations [Member]
Incurred Losses and LAE related to:
Prior Years - Incurred Losses and LAE	(3.9)	0.9	2.4
Property and Casualty, Commercial Insurance Product Line [Member] | Discontinued Operations [Member]
Incurred Losses and LAE related to:
Prior Years - Incurred Losses and LAE	(2.2)	(1.5)	(6.3)
Personal Automobile [Member]
Incurred Losses and LAE related to:
Prior Years - Incurred Losses and LAE	5.8	22.2	11.3
Homeowners [Member]
Incurred Losses and LAE related to:
Prior Years - Incurred Losses and LAE	3.2	1.0	(20.0)
Homeowners [Member] | Catastrophe [Member]
Incurred Losses and LAE related to:
Prior Years - Incurred Losses and LAE		(3.7)	(16.8)
Other Personal Lines [Member]
Incurred Losses and LAE related to:
Prior Years - Incurred Losses and LAE	$ (4.3)	$ (3.7)	$ (8.1)