Trading Assets and Liabilities and Derivatives - Additional Information (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities Sold under Agreements to Repurchase, Amount Offset Against Collateral	$ 1,100	$ 1,064
Repurchase Agreements [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities Pledged as Collateral	1,100	1,100
Equity Trading [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities Pledged as Collateral	40	40
Derivative [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities Pledged as Collateral	$ 341	$ 202