Investments Components of Equity Realized Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Components of Equity Realized Gains (Losses) [Line Items]
Realized Investment Gains (Losses)	$ 115.0	$ 72.4	$ 506.4	$ 35.6
Equity Securities, FV-NI, Net Realized Gain (Loss) on Sales	4.0	16.6	13.4	131.8
Equity Securities, FV-NI, Unrealized Gain (Loss)	$ 111.0	$ 55.8	$ 493.0	$ (96.2)