LHFI Considered Impaired (Additional Information) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Gross	[1]	$ 142,618		$ 143,181
Transfer of Loans Held-for-sale to Portfolio Loans		6	$ 7
Financing Receivable, Modifications, Post-Modification Recorded Investment		109	130
Impaired Financing Receivable, Interest Income, Cash Basis Method		1	1
Other Real Estate		59		57
Accrual Loans [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Modifications, Recorded Investment		$ 2,400		$ 2,400
Percentage Of Accruing Troubled Debt Restructurings, Current		98.00%		96.00%
Proceeds due from FHA or VA [Member]
Financing Receivable, Impaired [Line Items]
Other Real Estate		$ 43		$ 45
Consumer Other Direct [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Gross		8,941		$ 8,729
Financing Receivable, Modifications, Post-Modification Recorded Investment		$ 1	$ 1

[1] Includes loans of consolidated VIEs of $171 million and $179 million at March 31, 2018 and December 31, 2017, respectively.