Loans - TDR Disclosures in Progress Financial Impact of Modification (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 375	$ 272
Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	141	98
Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	85	102
Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
Total Loans Modified	75	86
Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
Total Loans Modified	8	13
Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
Total Loans Modified	2	3
Commercial Banking
Financing Receivable, Modifications [Line Items]
Total Loans Modified	149	72
Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
Total Loans Modified	149	72
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
Total Loans Modified	2	25
Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Total Loans Modified	147	47
Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 0	$ 0
Reduced Interest Rate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	50.00%	52.00%
Average Rate Reduction	14.14%	13.21%
Reduced Interest Rate | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	100.00%	100.00%
Average Rate Reduction	17.74%	17.52%
Reduced Interest Rate | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	53.00%	44.00%
Average Rate Reduction	3.78%	3.72%
Reduced Interest Rate | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	52.00%	42.00%
Average Rate Reduction	4.02%	3.93%
Reduced Interest Rate | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity	60.00%	62.00%
Average Rate Reduction	2.01%	2.63%
Reduced Interest Rate | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	50.00%	21.00%
Average Rate Reduction	3.00%	6.30%
Reduced Interest Rate | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	2.00%	0.00%
Average Rate Reduction	0.27%	0.00%
Reduced Interest Rate | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	2.00%	0.00%
Average Rate Reduction	0.27%	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	0.25%	0.00%
Reduced Interest Rate | Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
% of TDR Activity	1.00%	0.00%
Average Rate Reduction	0.31%	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	28.00%	42.00%
Average Term Extension (Months)	25 months	29 months
Term Extension | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months
Term Extension | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	87.00%	74.00%
Average Term Extension (Months)	25 months	39 months
Term Extension | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	89.00%	73.00%
Average Term Extension (Months)	7 months	7 months
Term Extension | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity	80.00%	75.00%
Average Term Extension (Months)	224 months	249 months
Term Extension | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	65.00%	87.00%
Average Term Extension (Months)	7 months	11 months
Term Extension | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	20.00%	54.00%
Average Term Extension (Months)	25 months	10 months
Term Extension | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	20.00%	54.00%
Average Term Extension (Months)	25 months	10 months
Term Extension | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	100.00%	100.00%
Average Term Extension (Months)	12 months	8 months
Term Extension | Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
% of TDR Activity	19.00%	30.00%
Average Term Extension (Months)	26 months	12 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
Balance Reduction
Financing Receivable, Modifications [Line Items]
% of TDR Activity	2.00%	8.00%
Gross Balance Reduction	$ 7	$ 21
Balance Reduction | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0
Balance Reduction | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	9.00%	23.00%
Gross Balance Reduction	$ 7	$ 21
Balance Reduction | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	10.00%	27.00%
Gross Balance Reduction	$ 7	$ 21
Balance Reduction | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	1.00%
Gross Balance Reduction	$ 0	$ 0
Balance Reduction | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0
Balance Reduction | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0
Balance Reduction | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0
Balance Reduction | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0
Balance Reduction | Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0
Balance Reduction | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0
Geographic Distribution, Domestic [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 97	$ 62
Geographic Distribution, Domestic [Member] | Reduced Interest Rate | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	100.00%	100.00%
Average Rate Reduction	13.85%	12.85%
Geographic Distribution, Domestic [Member] | Term Extension | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months
Geographic Distribution, Domestic [Member] | Balance Reduction | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0
Geographic Distribution, Foreign [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 44	$ 36
Geographic Distribution, Foreign [Member] | Reduced Interest Rate | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	100.00%	100.00%
Average Rate Reduction	26.18%	25.66%
Geographic Distribution, Foreign [Member] | Term Extension | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months
Geographic Distribution, Foreign [Member] | Balance Reduction | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0