Loans - Credit Card: Risk Profile by Geographic Region and Delinquency Status (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	$ 77,967	$ 91,755
Amount, 30+ day delinquencies	2,807	3,388
Amount, 90+ day delinquencies	1,209	1,563
% of Total	100.00%	100.00%
Percentage, 30+ day delinquencies	3.60%	3.69%
Percentage, 90+ day delinquencies	1.55%	1.70%
California [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	7,592	9,276
% of Total	9.70%	10.10%
New York [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	5,067	5,869
% of Total	6.50%	6.40%
Texas [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	4,762	5,933
% of Total	6.10%	6.50%
Florida [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	4,090	4,852
% of Total	5.20%	5.30%
Illinois [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	3,444	4,115
% of Total	4.40%	4.50%
Pennsylvania [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	3,256	3,875
% of Total	4.20%	4.20%
Ohio [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	2,814	3,363
% of Total	3.60%	3.60%
New Jersey [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	2,609	3,070
% of Total	3.40%	3.30%
Michigan [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	2,480	2,928
% of Total	3.20%	3.20%
Other [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	33,822	39,860
% of Total	43.40%	43.50%
Total Domestic Credit Card and Installment Loans [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	69,936	83,141
% of Total	89.70%	90.60%
United Kingdom [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	3,447	3,678
% of Total	4.40%	4.00%
Canada [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	4,584	4,936
% of Total	5.90%	5.40%
Total International Credit Card [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	8,031	8,614
% of Total	10.30%	9.40%
Loans [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	77,894	91,467
Amount, 30+ day delinquencies	2,786	3,326
Amount, 90+ day delinquencies	1,201	1,530
% of Total	99.90%	99.70%
Percentage, 30+ day delinquencies	3.57%	3.62%
Percentage, 90+ day delinquencies	1.54%	1.67%
Loans [Member] | California [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	7,585	9,245
% of Total	9.70%	10.00%
Loans [Member] | New York [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	5,060	5,846
% of Total	6.50%	6.40%
Loans [Member] | Texas [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	4,757	5,910
% of Total	6.10%	6.50%
Loans [Member] | Florida [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	4,086	4,835
% of Total	5.20%	5.30%
Loans [Member] | Illinois [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	3,441	4,100
% of Total	4.40%	4.50%
Loans [Member] | Pennsylvania [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	3,253	3,861
% of Total	4.20%	4.20%
Loans [Member] | Ohio [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	2,811	3,351
% of Total	3.60%	3.60%
Loans [Member] | New Jersey [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	2,607	3,060
% of Total	3.40%	3.30%
Loans [Member] | Michigan [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	2,478	2,917
% of Total	3.20%	3.20%
Loans [Member] | Other [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	33,785	39,728
% of Total	43.30%	43.30%
Loans [Member] | Total Domestic Credit Card and Installment Loans [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	69,863	82,853
% of Total	89.60%	90.30%
Loans [Member] | United Kingdom [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	3,447	3,678
% of Total	4.40%	4.00%
Loans [Member] | Canada [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	4,584	4,936
% of Total	5.90%	5.40%
Loans [Member] | Total International Credit Card [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	8,031	8,614
% of Total	10.30%	9.40%
Acquired Loans [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	73	288
Amount, 30+ day delinquencies	21	62
Amount, 90+ day delinquencies	8	33
% of Total	0.10%	0.30%
Percentage, 30+ day delinquencies	0.03%	0.07%
Percentage, 90+ day delinquencies	0.01%	0.03%
Acquired Loans [Member] | California [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	7	31
% of Total	0.00%	0.10%
Acquired Loans [Member] | New York [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	7	23
% of Total	0.00%	0.00%
Acquired Loans [Member] | Texas [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	5	23
% of Total	0.00%	0.00%
Acquired Loans [Member] | Florida [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	4	17
% of Total	0.00%	0.00%
Acquired Loans [Member] | Illinois [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	3	15
% of Total	0.00%	0.00%
Acquired Loans [Member] | Pennsylvania [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	3	14
% of Total	0.00%	0.00%
Acquired Loans [Member] | Ohio [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	3	12
% of Total	0.00%	0.00%
Acquired Loans [Member] | New Jersey [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	2	10
% of Total	0.00%	0.00%
Acquired Loans [Member] | Michigan [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	2	11
% of Total	0.00%	0.00%
Acquired Loans [Member] | Other [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	37	132
% of Total	0.10%	0.20%
Acquired Loans [Member] | Total Domestic Credit Card and Installment Loans [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	73	288
% of Total	0.10%	0.30%
Acquired Loans [Member] | United Kingdom [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	0	0
% of Total	0.00%	0.00%
Acquired Loans [Member] | Canada [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	0	0
% of Total	0.00%	0.00%
Acquired Loans [Member] | Total International Credit Card [Member]
Credit Card Risk Profile By Geographic Region And Delinquency Status [Line Items]
Total credit card and installment loans	$ 0	$ 0
% of Total	0.00%	0.00%