Derivatives Forward Contracts (Details) (Forward Contracts [Member]) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended					3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2012 USD ($) Rating		Sep. 30, 2012 USD ($) Rating		Sep. 30, 2012 SEK	Jun. 30, 2012 USD ($)	Dec. 31, 2011 USD ($)	Sep. 30, 2012 United States of America, Dollars USD ($)	Sep. 30, 2012 United States of America, Dollars USD ($)	Sep. 30, 2012 United Kingdom, Pounds USD ($)	Sep. 30, 2012 United Kingdom, Pounds USD ($)	Sep. 30, 2012 Euro Member Countries, Euro USD ($)	Sep. 30, 2012 Euro Member Countries, Euro USD ($)	Sep. 30, 2012 Sweden, Kronor USD ($)	Sep. 30, 2012 Sweden, Kronor USD ($)	Sep. 30, 2012 Foreign Currency Gain (Loss) [Member] USD ($)	Sep. 30, 2012 Foreign Currency Gain (Loss) [Member] USD ($)	Sep. 30, 2012 Goldman Sachs [Member] USD ($)		Sep. 30, 2012 J P Morgan Chase [Member] USD ($)		Sep. 30, 2012 HSBS Bank plc [Member] USD ($)		Sep. 30, 2012 Royal Bank of Canada [Member] USD ($)		Sep. 30, 2012 Deutsche Bank [Member] USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Net Exposure On Fair Value Of Over The Counter Derivative Instruments	$ 38.8	[1]	$ 38.8	[1]														$ 5.6	[1]	$ 7.3	[1]	$ 12.4	[1]	$ 8.0	[1]	$ 5.5	[1]
Fair Value Derivatives Measured on Recurring Basis, Asset Purchases	0		0
Derivative, Notional Amount	38.8		38.8		254.0
Derivative, Gain (Loss) on Derivative, Net	0.3		0.3					0.4	0.4	0	0	(0.1)	(0.1)	0	0	0	0
Derivative, Fair Value, Net	0.3		0.3			0	0	0.4	0.4	0	0	(0.1)	(0.1)	0	0	0	0
Fair Value Derivatives Measured on Recurring Basis, Asset Sales and Settlements	$ 0		$ 0
S&P Credit Ratings	22		22

[1] (2) Collateral provided (held) calculated under master netting agreement.