Loans - TDR Disclosures in Progress Financial Impact of Modification (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 273	$ 248
Credit Card
Financing Receivable, Modifications [Line Items]
Total Loans Modified	145	163
Consumer Banking
Financing Receivable, Modifications [Line Items]
Total Loans Modified	73	70
Consumer Banking | Auto
Financing Receivable, Modifications [Line Items]
Total Loans Modified	72	62
Consumer Banking | Home loan
Financing Receivable, Modifications [Line Items]
Total Loans Modified		6
Consumer Banking | Retail banking
Financing Receivable, Modifications [Line Items]
Total Loans Modified	1	2
Commercial Banking
Financing Receivable, Modifications [Line Items]
Total Loans Modified	55	15
Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
Total Loans Modified	55	13
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
Total Loans Modified	34	2
Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Total Loans Modified	21	11
Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 0	$ 2
Reduced Interest Rate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	75.00%	80.00%
Average Rate Reduction	14.64%	16.50%
Reduced Interest Rate | Credit Card
Financing Receivable, Modifications [Line Items]
% of TDR Activity	100.00%	100.00%
Average Rate Reduction	20.04%	19.17%
Reduced Interest Rate | Consumer Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	37.00%	49.00%
Average Rate Reduction	3.88%	3.71%
Reduced Interest Rate | Consumer Banking | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	37.00%	52.00%
Average Rate Reduction	3.83%	3.76%
Reduced Interest Rate | Consumer Banking | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity		28.00%
Average Rate Reduction		1.78%
Reduced Interest Rate | Consumer Banking | Retail banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	15.00%	11.00%
Average Rate Reduction	13.01%	10.22%
Reduced Interest Rate | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	61.00%	0.00%
Average Rate Reduction	0.00%	0.00%
Reduced Interest Rate | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	62.00%	0.00%
Average Rate Reduction	0.00%	0.00%
Reduced Interest Rate | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	100.00%	0.00%
Average Rate Reduction	0.00%	0.00%
Reduced Interest Rate | Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Average Rate Reduction	0.00%	0.00%
Reduced Interest Rate | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Average Rate Reduction	0.00%	0.00%
Term Extension
Financing Receivable, Modifications [Line Items]
% of TDR Activity	24.00%	30.00%
Average Term Extension (Months)	7 months	21 months
Term Extension | Credit Card
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months
Term Extension | Consumer Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	91.00%	90.00%
Average Term Extension (Months)	7 months	23 months
Term Extension | Consumer Banking | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	91.00%	91.00%
Average Term Extension (Months)	7 months	7 months
Term Extension | Consumer Banking | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity		83.00%
Average Term Extension (Months)		214 months
Term Extension | Consumer Banking | Retail banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	85.00%	81.00%
Average Term Extension (Months)	6 months	5 months
Term Extension | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	85.00%
Average Term Extension (Months)	0 months	11 months
Term Extension | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	100.00%
Average Term Extension (Months)	0 months	11 months
Term Extension | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	100.00%
Average Term Extension (Months)	0 months	7 months
Term Extension | Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	100.00%
Average Term Extension (Months)	0 months	11 months
Term Extension | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months
Domestic credit card | Credit Card
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 98	$ 113
Domestic credit card | Reduced Interest Rate | Credit Card
Financing Receivable, Modifications [Line Items]
% of TDR Activity	100.00%	100.00%
Average Rate Reduction	16.42%	15.73%
Domestic credit card | Term Extension | Credit Card
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months
International card business | Credit Card
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 47	$ 50
International card business | Reduced Interest Rate | Credit Card
Financing Receivable, Modifications [Line Items]
% of TDR Activity	100.00%	100.00%
Average Rate Reduction	27.59%	26.86%
International card business | Term Extension | Credit Card
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months