Loans - TDR Disclosures in Progress Financial Impact of Modification (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 272	$ 228
Commercial Banking
Financing Receivable, Modifications [Line Items]
Total Loans Modified	72	24
Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
Total Loans Modified	72	24
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
Total Loans Modified	25	3
Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Total Loans Modified	47	21
Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Modifications [Line Items]
Total Loans Modified	0	0
Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	98	104
Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	102	100
Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
Total Loans Modified	86	88
Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
Total Loans Modified	13	7
Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 3	$ 5
Reduced Interest Rate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	52.00%	65.00%
Average Rate Reduction	13.21%	12.19%
Reduced Interest Rate | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Average Rate Reduction	0.00%	2.02%
Reduced Interest Rate | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	0.00%
Average Rate Reduction	0.00%	2.02%
Reduced Interest Rate | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	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%	2.02%
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%
Reduced Interest Rate | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	100.00%	100.00%
Average Rate Reduction	17.52%	16.39%
Reduced Interest Rate | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
% of TDR Activity	44.00%	44.00%
Average Rate Reduction	3.72%	2.36%
Reduced Interest Rate | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	42.00%	41.00%
Average Rate Reduction	3.93%	1.71%
Reduced Interest Rate | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity	62.00%	67.00%
Average Rate Reduction	2.63%	2.85%
Reduced Interest Rate | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	21.00%	61.00%
Average Rate Reduction	6.30%	9.36%
Term Extension
Financing Receivable, Modifications [Line Items]
% of TDR Activity	42.00%	33.00%
Average Term Extension (Months)	29 months	20 months
Term Extension | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	54.00%	13.00%
Average Term Extension (Months)	10 months	29 months
Term Extension | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	54.00%	13.00%
Average Term Extension (Months)	10 months	29 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)	8 months	35 months
Term Extension | Commercial Banking | Commercial and industrial
Financing Receivable, Modifications [Line Items]
% of TDR Activity	30.00%	3.00%
Average Term Extension (Months)	12 months	7 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
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	74.00%	72.00%
Average Term Extension (Months)	39 months	20 months
Term Extension | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	73.00%	71.00%
Average Term Extension (Months)	7 months	9 months
Term Extension | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity	75.00%	66.00%
Average Term Extension (Months)	249 months	171 months
Term Extension | Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	87.00%	91.00%
Average Term Extension (Months)	11 months	4 months
Balance Reduction
Financing Receivable, Modifications [Line Items]
% of TDR Activity	8.00%	12.00%
Gross Balance Reduction	$ 21	$ 23
Balance Reduction | Commercial Banking
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	8.00%
Gross Balance Reduction	$ 0	$ 1
Balance Reduction | Commercial Banking | Total commercial lending
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	8.00%
Gross Balance Reduction	$ 0	$ 1
Balance Reduction | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Modifications [Line Items]
% of TDR Activity	0.00%	77.00%
Gross Balance Reduction	$ 0	$ 1
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
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	23.00%	24.00%
Gross Balance Reduction	$ 21	$ 22
Balance Reduction | Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Modifications [Line Items]
% of TDR Activity	27.00%	28.00%
Gross Balance Reduction	$ 21	$ 22
Balance Reduction | Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Modifications [Line Items]
% of TDR Activity	1.00%	0.00%
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
Geographic Distribution, Domestic [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Total Loans Modified	$ 62	$ 72
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	12.85%	12.13%
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	$ 36	$ 32
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	25.66%	25.79%
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
Performing
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	1,900		$ 1,800
Performing | Commercial Banking
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	305		334
Performing | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	$ 1,000		$ 1,000