Derivative Financial Instruments (Notional Amounts, Balance Sheet Location And Estimated Fair Values Of Derivative Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Contractual Notional Amount	$ 13,778.4	$ 16,940.0
Total derivative assets	529.8	901.9
Amounts netted	(216.7)	(791.8)
Net derivative assets	313.1	110.1
Total derivative liabilities	(477.1)	(812.5)
Amounts netted	216.7	791.8
Net derivative liabilities	(260.4)	(20.7)
Hedging Instruments [Member]
Derivative [Line Items]
Contractual Notional Amount	1,185.0	1,660.0
Hedging Instruments [Member] | Other Assets/Other Liabilities | Interest Rate Swaps [Member]
Derivative [Line Items]
Contractual Notional Amount	1,185.0	1,660.0
Total derivative assets	2.6	30.9
Total derivative liabilities	(7.8)	(20.7)
Non-Hedging Instruments [Member]
Derivative [Line Items]
Contractual Notional Amount	12,593.4	15,280.0
Total derivative assets	527.2	871.0
Total derivative liabilities	(469.3)	(791.8)
Non-Hedging Instruments [Member] | Other Assets/Other Liabilities | Options [Member]
Derivative [Line Items]
Contractual Notional Amount	12,208.5	14,912.4
Total derivative assets	428.0
Total derivative liabilities	(458.4)
Non-Hedging Instruments [Member] | Fixed Maturity Securities [Member] | Derivatives Embedded In Convertible Fixed Maturity Securities [Member]
Derivative [Line Items]
Contractual Notional Amount	287.0	295.0
Total derivative assets	98.7	89.2
Total derivative liabilities	0	0
Non-Hedging Instruments [Member] | Equity Securities [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Contractual Notional Amount	97.9
Total derivative assets	0
Total derivative liabilities	(9.4)
Non-Hedging Instruments [Member] | Equity Securities [Member] | Credit Default And Interest Rate Swaps [Member]
Derivative [Line Items]
Contractual Notional Amount		72.6
Total derivative assets		1.8
Total derivative liabilities		(2.5)
Non-Hedging Instruments [Member] | Equity Securities [Member] | Futures [Member]
Derivative [Line Items]
Contractual Notional Amount	0	0
Total derivative assets	0.5	3.5
Total derivative liabilities	(1.5)	(1.6)
Non-Hedging Instruments [Member] | Equity Securities and Other Assets [Member] | Options [Member]
Derivative [Line Items]
Total derivative assets		776.5
Total derivative liabilities		$ (787.7)