Investments Components of Equity Realized Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Components of Equity Realized Gains (Losses) [Line Items]
Realized Investment Gains (Losses)	$ 33.9	$ 212.2	$ 540.3	$ 247.8
Equity Securities, FV-NI, Net Realized Gain (Loss) on Sales	6.3	117.7	19.7	249.5
Equity Securities, FV-NI, Unrealized Gain (Loss)	$ 27.6	$ 94.5	$ 520.6	$ (1.7)