Investments - Net Realized Gains on Sales of Investments (Details) - Fixed Maturities - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net Investment Income [Line Items]
Gains on Sales	$ 22.7	$ 1.2	$ 37.8	$ 5.3
Losses on Sales	$ (1.9)	$ (1.9)	$ (4.5)	$ (4.0)