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	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Included In Earnings	$ 10	$ 185	$ 255
Mortgage Banking Revenue
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Included In Earnings	16	10	233
Corporate Banking Revenue
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Included In Earnings	1		1
Other Noninterest Income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset And Liabilities Change In Unrealized Gains Losses Included In Earnings	$ (7)	$ 175	$ 21