Investments - Schedule of Other Than Temporary Impairment (Details) - Fixed Maturities - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Cumulative Balance of Pre-tax Credit Losses Recognized in Retained Earnings at Beginning of Period	$ 1.2	$ 1.6	$ 1.1	$ 1.6
Pre-tax Credit Losses on Fixed Maturities without Pre-tax Credit Losses Included in Cumulative Balance at Beginning of Period	0.1	0.0	0.2	0.0
Additional Pre-tax Credit Losses on Fixed Maturities with Pre-tax Credit Losses Included in Cumulative Balance at Beginning of Period	0.0	0.0	0.0	0.0
Reductions to Previously Recognized OTTI Credit Losses	0.0	0.0	0.0	0.0
Reductions for Change in Impairment Status:
From Status of Credit Loss to Status of Intent-to-sell or Required-to-sell	0.0	(0.5)	0.0	(0.5)
Reductions for Investments Sold During Period	0.0	0.0	0.0	0.0
Cumulative Balance of Pre-tax Credit Losses Recognized in Retained Earnings at End of Period	$ 1.3	$ 1.1	$ 1.3	$ 1.1