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
	Mar. 31, 2013	Mar. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Included In Earnings	$ 79	$ 44
Mortgage Banking Revenue
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Included In Earnings	52	16
Other Noninterest Income
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Included In Earnings	$ 27	$ 28