Variable Interest Entities - Credit Related Note, Asset Swap Vehicle VIEs (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Asset Swap VIEs [Member] | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Par value of collateral held by VIEs	$ 5,700,000,000	$ 7,700,000,000
Credit linked notes [Member] | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Par value of collateral held by VIEs	5,900,000,000	8,700,000,000
Credit linked notes [Member] | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	$ 163,000,000	$ 311,000,000