Total Gains and Losses Included in Earnings for Assets and Liabilites Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Gain and losses included in earnings	$ 12	$ 170	$ 96	$ 249
Mortgage Banking Revenue
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Gain and losses included in earnings	(59)	125	(2)	175
Other Noninterest Income
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Gain and losses included in earnings	$ 71	$ 45	$ 98	$ 74