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	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loss Contingencies [Line Items]
Outstanding repurchase demands received	$ 3	$ 44	$ 89
GSEs [Member]
Loss Contingencies [Line Items]
Outstanding repurchase demands received	2	41	86
Others [Member]
Loss Contingencies [Line Items]
Outstanding repurchase demands received	$ 1	$ 3	$ 3