Financial Derivatives (Narrative) (Details) (USD $) In Millions, unless otherwise specified			9 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Credit Default Swap, Selling Protection [Member]	Dec. 31, 2012 Credit Default Swap, Selling Protection [Member]
Derivative [Line Items]
Low range of spread on written credit derivatives	0.25%	0.35%
High range of spread on written credit derivatives	4.58%	4.58%
Total net up-front payments received			$ 20.9	$ 12.6