Guarantee Arrangements and Pledged Assets and Collateral - Outstanding Repurchase Demands Received From GSEs and Other Third Parties (Detail) (Obligation to Repurchase Receivables Sold [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Loss Contingencies [Line Items]
Outstanding repurchase demands received	$ 3	$ 44
GSEs [Member]
Loss Contingencies [Line Items]
Outstanding repurchase demands received	2	41
Others [Member]
Loss Contingencies [Line Items]
Outstanding repurchase demands received	$ 1	$ 3