Trading Assets and Liabilities and Derivatives - Additional Information (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities Sold under Agreements to Repurchase, Amount Offset Against Collateral	$ 1,002	$ 950
Repurchase Agreements [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities Pledged as Collateral	1,043	986
Derivative [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities Pledged as Collateral	446	393
Equity Trading [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities Pledged as Collateral	$ 40	$ 40