Loans - Credit Card: Risk Profile by Geographic Region and Delinquency Status (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 213,329	$ 208,316	$ 201,592
Past due	$ 6,294	$ 6,070
30 Plus day delinquencies (as percent)	2.95%	2.91%
Credit Card Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 90,135	$ 85,876
Percentage of portfolio	100.00%	100.00%
Past due	$ 2,967	$ 2,832
Credit Card Portfolio Segment [Member] | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 9,310	$ 8,574
Percentage of portfolio	10.30%	10.00%
Credit Card Portfolio Segment [Member] | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 6,042	$ 5,610
Percentage of portfolio	6.70%	6.50%
Credit Card Portfolio Segment [Member] | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 5,901	$ 5,382
Percentage of portfolio	6.50%	6.30%
Credit Card Portfolio Segment [Member] | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 5,260	$ 4,794
Percentage of portfolio	5.80%	5.60%
Credit Card Portfolio Segment [Member] | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 3,870	$ 3,747
Percentage of portfolio	4.30%	4.40%
Credit Card Portfolio Segment [Member] | Pennsylvania
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 3,521	$ 3,581
Percentage of portfolio	3.90%	4.20%
Credit Card Portfolio Segment [Member] | Ohio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 3,136	$ 3,075
Percentage of portfolio	3.50%	3.60%
Credit Card Portfolio Segment [Member] | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 3,004	$ 2,868
Percentage of portfolio	3.30%	3.30%
Credit Card Portfolio Segment [Member] | Michigan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 2,754	$ 2,681
Percentage of portfolio	3.10%	3.10%
Credit Card Portfolio Segment [Member] | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 39,380	$ 37,392
Percentage of portfolio	43.80%	43.50%
Credit Card Portfolio Segment [Member] | Canada
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 4,698	$ 4,747
Percentage of portfolio	5.20%	5.50%
Credit Card Portfolio Segment [Member] | United Kingdom
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 3,259	$ 3,425
Percentage of portfolio	3.60%	4.00%
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 1,849	$ 1,805
30 Plus day delinquencies (as percent)	0.87%	0.87%
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 1,294	$ 1,292
Geographic Distribution, Domestic [Member] | Credit Card Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 82,178	$ 77,704
Percentage of portfolio	91.20%	90.50%
Past due	$ 2,697	$ 2,538
Geographic Distribution, Domestic [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	1,196	1,181
Geographic Distribution, Foreign [Member] | Credit Card Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 7,957	$ 8,172
Percentage of portfolio	8.80%	9.50%
Past due	$ 270	$ 294
Geographic Distribution, Foreign [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Credit Card Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 98	$ 111