Activity Related to Mortgage Banking Net Revenue (Parenthetical) (Detail) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2015	Dec. 31, 2015	[1]	Dec. 31, 2014	Dec. 31, 2013
Mortgage Loans On Real Estate [Line Items]
Residential mortgage loan sales	[2]		$ 5,078		$ 5,467	$ 21,529
Residential Portfolio Segment | Troubled Debt Restructuring
Mortgage Loans On Real Estate [Line Items]
Residential mortgage loan sales		$ 568

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

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