Loans - Credit Card: Risk Profile by Geographic Region and Delinquency Status (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 245,586	$ 229,851	$ 208,316
Credit Card Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 105,552	$ 96,125
Percentage of portfolio	100.00%	100.00%
Credit Card Portfolio Segment [Member] | California
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 11,068	$ 10,029
Percentage of portfolio	10.50%	10.50%
Credit Card Portfolio Segment [Member] | Texas
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 7,227	$ 6,344
Percentage of portfolio	6.80%	6.60%
Credit Card Portfolio Segment [Member] | New York
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 7,090	$ 6,446
Percentage of portfolio	6.70%	6.70%
Credit Card Portfolio Segment [Member] | Florida
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 6,540	$ 5,712
Percentage of portfolio	6.20%	5.90%
Credit Card Portfolio Segment [Member] | Illinois
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 4,492	$ 4,121
Percentage of portfolio	4.30%	4.30%
Credit Card Portfolio Segment [Member] | Pennsylvania
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 4,048	$ 3,764
Percentage of portfolio	3.80%	3.90%
Credit Card Portfolio Segment [Member] | Ohio
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 3,654	$ 3,371
Percentage of portfolio	3.50%	3.50%
Credit Card Portfolio Segment [Member] | New Jersey
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 3,488	$ 3,210
Percentage of portfolio	3.30%	3.30%
Credit Card Portfolio Segment [Member] | Michigan
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 3,164	$ 2,922
Percentage of portfolio	3.00%	3.00%
Credit Card Portfolio Segment [Member] | Other
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 46,349	$ 42,020
Percentage of portfolio	43.90%	43.80%
Credit Card Portfolio Segment [Member] | Canada
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 5,594	$ 4,889
Percentage of portfolio	5.30%	5.10%
Credit Card Portfolio Segment [Member] | United Kingdom
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 2,838	$ 3,297
Percentage of portfolio	2.70%	3.40%
Credit Card Portfolio Segment [Member] | Geographic Distribution, Domestic [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 97,120	$ 87,939
Percentage of portfolio	92.00%	91.50%
Credit Card Portfolio Segment [Member] | Geographic Distribution, Foreign [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans held for investment	$ 8,432	$ 8,186
Percentage of portfolio	8.00%	8.50%