Activity Related to Mortgage Banking Net Revenue (Parenthetical) (Detail) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	[2]	Sep. 30, 2014
Mortgage Loans On Real Estate [Line Items]
Residential mortgage loan sales	[1]	$ 1,421		$ 1,228	$ 3,798		$ 4,423
Residential Mortgage Loans | Troubled Debt Restructuring
Mortgage Loans On Real Estate [Line Items]
Residential mortgage loan sales			$ 568

[1] Represents the unpaid principal balance at the time of the sale.

[2] Excludes $568 of HFS residential mortgage loans previously modified in a TDR that were sold during the first quarter of 2015.