Financial Derivatives (Credit Default Swaps) (Details) - Credit Default Swap, Buying Protection [Member] - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Credit Derivatives [Line Items]
Notional Amount	$ 98	$ 110
Average term of credit risk derivatives	19 years 1 month	21 years 4 months
Underlying Other Beneficiary Single Name [Member]
Credit Derivatives [Line Items]
Notional Amount	$ 50	$ 50
Average term of credit risk derivatives	5 years 2 months	5 years 8 months
Underlying Other Beneficiary Index Traded [Member]
Credit Derivatives [Line Items]
Notional Amount	$ 48	$ 60
Average term of credit risk derivatives	33 years 8 months	34 years 2 months