Total Gains and Losses Included in Earning Attributable to Changes in Unrealized Gains and Losses Related to Level 3 Assets and Liabilites Still Held at Year End (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Included In Earnings	$ 85	$ 26	$ 230	$ 45
Mortgage Banking Revenue [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Included In Earnings	103	41	174	46
Corporate Banking Revenue [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Included In Earnings				1
Other Noninterest Income [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Included In Earnings	$ (18)	$ (15)	$ 56	$ (2)