LHFI Considered Impaired (Additional Information) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019		Mar. 31, 2018		Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Gross	[1]	$ 155,233				$ 151,839
Transfer of Loans Held-for-sale to Portfolio Loans		4		$ 6
Financing Receivable, Modifications, Post-Modification Recorded Investment		88	[2]	109	[3]
Accrual Loans [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Modifications, Recorded Investment		$ 1,800				$ 2,300
Percentage Of Accruing Troubled Debt Restructurings, Current		97.00%				97.00%
Commercial Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Gross		$ 83,729				$ 80,940
Consumer Other Direct [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Gross		11,029				$ 10,615
Financing Receivable, Modifications, Post-Modification Recorded Investment		$ 2	[2]	$ 1	[3]

[1] Includes loans of consolidated VIEs of $147 million and $153 million at March 31, 2019 and December 31, 2018, respectively.

[2] Includes loans modified under the terms of a TDR that were charged-off during the period.

[3] Includes loans modified under the terms of a TDR that were charged-off during the period.