Loans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loans and Leases Receivable Disclosure [Line Items]
Uncollectible Portion of Billed Finance Charges and Fees	$ 1,300	$ 1,400	$ 1,100
Finance Charge And Fees Reserves	468	491
Loans held for sale, at lower of cost or fair value	1,192	971
Loans and Leases Receivable, Impaired, Commitment to Lend	$ 256	241
Loans Sold Percent Retained Servicing	100.00%
Performing
Loans and Leases Receivable Disclosure [Line Items]
Troubled debt restructurings included in impaired loans	$ 1,600	2,200
Residential Mortgage Loans And Commercial Multifamily Real Estate Loans
Loans and Leases Receivable Disclosure [Line Items]
Payments for Origination of Mortgage Loans Held-for-sale		8,400	$ 7,600
Commercial Multifamily Real Estate
Loans and Leases Receivable Disclosure [Line Items]
Payments for Origination of Mortgage Loans Held-for-sale	8,700
Federal Home Loan banks
Loans and Leases Receivable Disclosure [Line Items]
Loans Pledged as Collateral	15,800	27,300
Line of Credit Facility, Remaining Borrowing Capacity	19,300	21,000
Federal Reserve Discount Window
Loans and Leases Receivable Disclosure [Line Items]
Loans Pledged as Collateral	9,200	9,100
Line of Credit Facility, Remaining Borrowing Capacity	7,600	7,400
Consumer Portfolio Segment | Performing
Loans and Leases Receivable Disclosure [Line Items]
Troubled debt restructurings included in impaired loans	1,200	1,300
Commercial Banking | Performing
Loans and Leases Receivable Disclosure [Line Items]
Troubled debt restructurings included in impaired loans	$ 282	$ 574