Derivative Financial Instruments Credit Default Swaps (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Securities pledged as collateral	$ 140.1		$ 219.7
Asset Fair Value	493.4		566.4
Liability Fair Value	185.7		469.2
Payables under securities loan agreement, including collateral held
Derivatives, Fair Value [Line Items]
Cash collateral held for securities loan agreement	127.4		167.0
Credit contracts | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Maximum potential future net exposure on sale of credit default swaps	384.0		329.0
Term of derivative	5 years
Credit contracts | Not Designated as Hedging Instrument | Derivatives
Derivatives, Fair Value [Line Items]
Asset Fair Value	8.1	[1]	3.6	[1]
Liability Fair Value	0	[1]	0	[1]
Over the Counter [Member]
Derivatives, Fair Value [Line Items]
Securities pledged as collateral	1.2
Fixed maturities
Derivatives, Fair Value [Line Items]
Securities pledged as collateral	$ 42.5		$ 39.5

[1] Open derivative contracts are reported as Derivatives assets or liabilities on the Consolidated Balance Sheets at fair value