LHFI Considered Impaired (Additional Information) (Detail) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2018		Jun. 30, 2017		Jun. 30, 2018		Jun. 30, 2017		Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Gross	[1]	$ 144,935				$ 144,935				$ 143,181
Transfer of Loans Held-for-sale to Portfolio Loans		12		$ 3		18		$ 10
Financing Receivable, Modifications, Post-Modification Recorded Investment		102	[2]	130	[3]	206	[4]	216	[5]
Other Real Estate		53				53				57
Accrual Loans [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Modifications, Recorded Investment		$ 2,400				$ 2,400				$ 2,400
Percentage Of Accruing Troubled Debt Restructurings, Current		98.00%				98.00%				96.00%
Proceeds due from FHA or VA [Member]
Financing Receivable, Impaired [Line Items]
Other Real Estate		$ 44				$ 44				$ 45
Consumer Other Direct [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Gross		9,448				9,448				$ 8,729
Financing Receivable, Modifications, Post-Modification Recorded Investment		$ 3	[2]	$ 2	[3]	$ 5	[4]	$ 4	[5]

[1] Includes loans of consolidated VIEs of $165 million and $179 million at June 30, 2018 and December 31, 2017, 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.

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

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