Financial Derivatives (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Low Range Of Spread On Written Credit Derivatives	0.15%	0.15%
High Range Of Spread On Written Credit Derivatives	5.00%	5.00%
Credit Default Swap, Selling Protection [Member]
Derivative [Line Items]
Total net up-front payments received	$ 33.4	$ 28.9