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) - Fair Value, Inputs, Level 3 - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gains and losses included in earnings	$ 91	$ 90
Mortgage Banking Revenue
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gains and losses included in earnings	43	36
Corporate Banking Revenue
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gains and losses included in earnings		1
Other Noninterest Income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gains and losses included in earnings	$ 48	$ 53