Commitments, Contingencies, Guarantees, and Others - Guarantees, LOC and Loss Sharing, U.K Cross Sell (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Insurance Claims [Member]
Loss Contingencies [Line Items]
Loss contingency accrual	$ 150	$ 176
Loss Contingency, Range of Possible Loss, Portion Not Accrued	250
Letter of Credit
Loss Contingencies [Line Items]
Contractual amounts of standby letters of credit and commercial letters of credit	1,900	1,900
Other Liabilities | Letter of Credit
Loss Contingencies [Line Items]
Letters of credit outstanding	3	3
Loss Sharing Agreement
Loss Contingencies [Line Items]
Guarantee obligation	$ 41	$ 40