Loans - TDR Disclosures in Progress Financial Impact of Modification (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 1,654	$ 1,095	$ 973
Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	450	414	418
Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	422	419	380
Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
Total Loans Modified	356	347	334
Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
Total Loans Modified	48	48	35
Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
Total Loans Modified	18	24	11
Commercial Banking
Financing Receivable, Modifications [Line Items]
Total Loans Modified	782	262	175
Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
Total Loans Modified	781	261	173
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
Total Loans Modified	38	12	72
Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Total Loans Modified	743	249	101
Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 1	$ 1	$ 2
Reduced Interest Rate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	41.00%	54.00%	60.00%
Average Rate Reduction	12.42%	12.42%	12.17%
Reduced Interest Rate | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	100.00%	100.00%	100.00%
Average Rate Reduction	17.09%	16.26%	16.51%
Reduced Interest Rate | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	46.00%	42.00%	37.00%
Average Rate Reduction	3.73%	3.44%	1.50%
Reduced Interest Rate | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	44.00%	41.00%	39.00%
Average Rate Reduction	3.91%	3.49%	1.38%
Reduced Interest Rate | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity	64.00%	61.00%	31.00%
Average Rate Reduction	2.25%	2.70%	2.60%
Reduced Interest Rate | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	23.00%	18.00%	10.00%
Average Rate Reduction	7.89%	6.88%	4.21%
Reduced Interest Rate | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	4.00%	0.00%	17.00%
Average Rate Reduction	0.09%	0.67%	1.35%
Reduced Interest Rate | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	4.00%	0.00%	17.00%
Average Rate Reduction	0.09%	0.67%	1.35%
Reduced Interest Rate | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	35.00%
Average Rate Reduction	0.00%	0.00%	1.31%
Reduced Interest Rate | Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
% of TDR Activity	5.00%	0.00%	3.00%
Average Rate Reduction	0.09%	0.67%	1.66%
Reduced Interest Rate | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%
Average Rate Reduction	0.00%	0.00%	0.00%
Term Extension
Financing Receivable, Modifications [Line Items]
% of TDR Activity	46.00%	36.00%	38.00%
Average Term Extension (Months)	27 months	29 months	14 months
Term Extension | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months	0 months
Term Extension | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	75.00%	71.00%	63.00%
Average Term Extension (Months)	38 months	36 months	17 months
Term Extension | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	74.00%	69.00%	65.00%
Average Term Extension (Months)	7 months	8 months	9 months
Term Extension | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity	87.00%	79.00%	38.00%
Average Term Extension (Months)	243 months	231 months	152 months
Term Extension | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	68.00%	87.00%	67.00%
Average Term Extension (Months)	10 months	6 months	9 months
Term Extension | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	57.00%	36.00%	74.00%
Average Term Extension (Months)	19 months	8 months	9 months
Term Extension | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	57.00%	36.00%	75.00%
Average Term Extension (Months)	19 months	8 months	9 months
Term Extension | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	67.00%	86.00%	93.00%
Average Term Extension (Months)	6 months	14 months	8 months
Term Extension | Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
% of TDR Activity	57.00%	34.00%	62.00%
Average Term Extension (Months)	20 months	7 months	9 months
Term Extension | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months	0 months
Balance Reduction
Financing Receivable, Modifications [Line Items]
% of TDR Activity	9.00%	10.00%	12.00%
Gross Balance Reduction	$ 108	$ 94	$ 106
Balance Reduction | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0	$ 0
Balance Reduction | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	22.00%	26.00%	30.00%
Gross Balance Reduction	$ 79	$ 93	$ 103
Balance Reduction | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	25.00%	30.00%	34.00%
Gross Balance Reduction	$ 78	$ 93	$ 102
Balance Reduction | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity	2.00%	7.00%	5.00%
Gross Balance Reduction	$ 0	$ 0	$ 1
Balance Reduction | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	9.00%	0.00%	0.00%
Gross Balance Reduction	$ 1	$ 0	$ 0
Balance Reduction | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	8.00%	1.00%	3.00%
Gross Balance Reduction	$ 29	$ 1	$ 3
Balance Reduction | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	8.00%	1.00%	3.00%
Gross Balance Reduction	$ 29	$ 1	$ 3
Balance Reduction | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	32.00%	18.00%	6.00%
Gross Balance Reduction	$ 3	$ 1	$ 2
Balance Reduction | Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
% of TDR Activity	7.00%	0.00%	1.00%
Gross Balance Reduction	$ 26	$ 0	$ 1
Balance Reduction | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0	$ 0
Geographic Distribution, Domestic [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 312	$ 293	$ 269
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%
Average Rate Reduction	13.19%	12.28%	11.59%
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%
Average Term Extension (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%
Gross Balance Reduction	$ 0	$ 0	$ 0
Geographic Distribution, Foreign [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 138	$ 121	$ 149
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%
Average Rate Reduction	25.87%	25.88%	25.39%
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%
Average Term Extension (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%
Gross Balance Reduction	$ 0	$ 0	$ 0