Investments - OTTI losses Recognized in Accumulated Other Comprehensive Income (Details) - Fixed Maturities [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance at Beginning of Year	$ 1.6	$ 1.4	$ 5.1
Additions for Previously Unrecognized OTTI Credit Losses	0.0	1.2	2.7
Reduction due to Intent to Sell Investments	(0.5)	(0.7)	(6.3)
Reductions for Investments Sold During Period	0.0	(0.3)	(0.1)
Balance at End of Year	$ 1.1	$ 1.6	$ 1.4