Loans - TDR Disclosures in Progress Financial Impact of Modification (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 251	$ 206	$ 704	$ 671
Commercial Banking
Financing Receivable, Modifications [Line Items]
Total Loans Modified	30	4	85	84
Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
Total Loans Modified	30	4	84	83
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
Total Loans Modified	9	1	12	67
Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Total Loans Modified	21	3	72	16
Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
Total Loans Modified	0	0	1	1
Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	106	103	308	315
Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	115	99	311	272
Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
Total Loans Modified	88	88	257	234
Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
Total Loans Modified	17	10	34	29
Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 10	$ 1	$ 20	$ 9
Reduced Interest Rate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	62.00%	70.00%	62.00%	65.00%
Average Rate Reduction	12.13%	11.94%	12.40%	12.34%
Reduced Interest Rate | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	71.00%	0.00%	28.00%
Average Rate Reduction	0.00%	0.85%	1.06%	1.11%
Reduced Interest Rate | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	71.00%	0.00%	29.00%
Average Rate Reduction	0.00%	0.85%	1.06%	1.11%
Reduced Interest Rate | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%	31.00%
Average Rate Reduction	0.00%	0.00%	0.00%	1.26%
Reduced Interest Rate | Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	96.00%	0.00%	20.00%
Average Rate Reduction	0.00%	0.85%	1.06%	0.18%
Reduced Interest Rate | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%	0.00%
Average Rate Reduction	0.00%	0.00%	0.00%	0.00%
Reduced Interest Rate | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	100.00%	100.00%	100.00%	100.00%
Average Rate Reduction	16.01%	16.12%	16.21%	16.60%
Reduced Interest Rate | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	43.00%	40.00%	42.00%	36.00%
Average Rate Reduction	3.81%	1.88%	3.31%	1.41%
Reduced Interest Rate | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	42.00%	40.00%	41.00%	37.00%
Average Rate Reduction	4.14%	1.70%	3.28%	1.24%
Reduced Interest Rate | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity	70.00%	41.00%	60.00%	34.00%
Average Rate Reduction	2.63%	3.33%	2.78%	2.64%
Reduced Interest Rate | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	6.00%	17.00%	19.00%	8.00%
Average Rate Reduction	6.15%	6.42%	7.19%	5.17%
Term Extension
Financing Receivable, Modifications [Line Items]
% of TDR Activity	38.00%	32.00%	38.00%	36.00%
Average Term Extension (Months)	42 months	20 months	27 months	16 months
Term Extension | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	40.00%	74.00%	53.00%	86.00%
Average Term Extension (Months)	9 months	7 months	8 months	8 months
Term Extension | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	40.00%	74.00%	53.00%	87.00%
Average Term Extension (Months)	9 months	7 months	8 months	8 months
Term Extension | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	83.00%	0.00%	86.00%	92.00%
Average Term Extension (Months)	8 months	0 months	14 months	7 months
Term Extension | Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
% of TDR Activity	21.00%	100.00%	48.00%	67.00%
Average Term Extension (Months)	9 months	7 months	6 months	10 months
Term Extension | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months	0 months	0 months
Term Extension | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months	0 months	0 months
Term Extension | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	73.00%	63.00%	71.00%	61.00%
Average Term Extension (Months)	46 months	21 months	31 months	19 months
Term Extension | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	68.00%	64.00%	69.00%	63.00%
Average Term Extension (Months)	7 months	9 months	8 months	9 months
Term Extension | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity	87.00%	52.00%	74.00%	39.00%
Average Term Extension (Months)	232 months	150 months	209 months	154 months
Term Extension | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	94.00%	88.00%	88.00%	72.00%
Average Term Extension (Months)	6 months	3 months	6 months	7 months
Balance Reduction
Financing Receivable, Modifications [Line Items]
% of TDR Activity	11.00%	15.00%	12.00%	13.00%
Gross Balance Reduction	$ 24	$ 28	$ 70	$ 78
Balance Reduction | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	8.00%	2.00%	5.00%
Gross Balance Reduction	$ 0	$ 0	$ 1	$ 2
Balance Reduction | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	8.00%	2.00%	5.00%
Gross Balance Reduction	$ 0	$ 0	$ 1	$ 2
Balance Reduction | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	18.00%	6.00%
Gross Balance Reduction	$ 0	$ 0	$ 1	$ 2
Balance Reduction | Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	11.00%	0.00%	2.00%
Gross Balance Reduction	$ 0	$ 0	$ 0	$ 0
Balance Reduction | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0	$ 0	$ 0
Balance Reduction | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0	$ 0	$ 0
Balance Reduction | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	25.00%	31.00%	26.00%	31.00%
Gross Balance Reduction	$ 24	$ 28	$ 69	$ 76
Balance Reduction | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	31.00%	35.00%	30.00%	36.00%
Gross Balance Reduction	$ 24	$ 28	$ 69	$ 75
Balance Reduction | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity	6.00%	2.00%	9.00%	6.00%
Gross Balance Reduction	$ 0	$ 0	$ 0	$ 1
Balance Reduction | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0	$ 0	$ 0
Geographic Distribution, Domestic [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 77	$ 68	$ 217	$ 199
Geographic Distribution, Domestic [Member] | Reduced Interest Rate | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	100.00%	100.00%	100.00%	100.00%
Average Rate Reduction	12.30%	11.52%	12.16%	11.52%
Geographic Distribution, Domestic [Member] | Term Extension | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%	0.00%
Average Term Extension (Months)	0 months	0 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%	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0	$ 0	$ 0
Geographic Distribution, Foreign [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 29	$ 35	$ 91	$ 116
Geographic Distribution, Foreign [Member] | Reduced Interest Rate | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	100.00%	100.00%	100.00%	100.00%
Average Rate Reduction	25.89%	25.41%	25.87%	25.35%
Geographic Distribution, Foreign [Member] | Term Extension | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%	0.00%
Average Term Extension (Months)	0 months	0 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%	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0	$ 0	$ 0
Performing
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	1,642		1,642		$ 1,652
Performing | Commercial Banking
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	187		187		194
Performing | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	$ 1,000		$ 1,000		$ 1,000