Financial Derivatives (Credit Default Swaps) (Details) (Credit Default Swap, Buying Protection [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Credit Derivatives [Line Items]
Notional Amount	$ 110	$ 95
Average term of credit risk derivatives	21 years 3 months	24 years 11 months
Underlying Other Beneficiary Single Name [Member]
Credit Derivatives [Line Items]
Notional Amount	50	35
Average term of credit risk derivatives	5 years 9 months	7 years 4 months
Underlying Other Beneficiary Index Traded [Member]
Credit Derivatives [Line Items]
Notional Amount	$ 60	$ 60
Average term of credit risk derivatives	34 years 3 months	35 years 2 months