MSR (Sales of Receivables and Servicing Rights - Additional Information) (Detail) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Servicing Assets at Fair Value
Residential mortgage loan sales	[1]		$ 6,927	$ 5,078	[2]	$ 5,467
Sevicing of residential mortgage loans for other investors			53,600	59,000
Amortization			$ (131)	$ (140)		$ (121)
Residential Mortgage Loans | Troubled Debt Restructuring
Servicing Assets at Fair Value
Gain on sale of HFS loans		$ 37
Residential mortgage loan sales		$ 568

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

[2] Excludes $ 568 of HFS residential mort gage loans previously modified in a TDR that were sold d uring the first quarter of 2015 .