Schedule V - Valuation and Qualifying Accounts (Details) - Reserve for unrecoverable reinsurance [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 0.0	$ 15.9		$ 15.9
Charged to Cost and Expenses	0.0	0.0		0.0
Charged to Other Accounts - Describe	0.0	0.0		0.0
Deductions - Describe	0.0	(15.9)	[1]	0.0
Balance at End of Period	$ 0.0	$ 0.0		$ 15.9

[1] (1) Reflects the reduction of allowances for unrecoverable reinsurance no longer deemed necessary.