Financial Derivatives (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Credit Default Swap, Selling Protection [Member]
Derivative [Line Items]
Total net up-front payments received	$ 97.9	$ 137.8
Minimum [Member]
Derivative [Line Items]
Low Range Of Spread On Written Credit Derivatives	0.24%	0.195%
Maximum [Member]
Derivative [Line Items]
Low Range Of Spread On Written Credit Derivatives	35.831%	46.287%