Derivative Financial Instruments (Effect Of Non-Hedging Derivatives On Income Statement And Included In Net Realized Gains (Losses) On Investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Gain (Loss) Recognized	$ (48.3)	$ (207.5)	$ 10.4
Derivatives Embedded In Convertible Fixed Maturity Securities [Member] | Net realized gains on financial instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Gain (Loss) Recognized			(22.2)
Interest Rate Swaps [Member] | Net realized gains on financial instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Gain (Loss) Recognized	(9.2)	0.2	(1.9)
Options [Member] | Net realized gains on financial instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Gain (Loss) Recognized	(35.6)	(209.1)	34.6
Futures [Member] | Net realized gains on financial instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Gain (Loss) Recognized	$ (3.5)	$ 1.4	$ (0.1)