Loans and Allowance for Loan Losses - FICO Credit Scores and LTV Ratios Related to Loans in Consumer Portfolio Segment (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
FICO scores:
720 and above	$ 18,405		$ 17,086
720 and above, in percent	76.00%		75.00%
Below 720	5,272		5,363
Below 720, in percent	22.00%		24.00%
No FICO available	486	[1]	316	[1]
No FICO available, in percent	2.00%	[1]	1.00%	[1]
Total	24,163		22,765
Total Scores, in percent	100.00%		100.00%
LTV ratios:
Less than 80 percent, percent	77.00%		64.00%
Less than 80 percent	18,458		14,492
80-100 percent, percent	15.00%		22.00%
80-100 percent	3,570		5,027
Greater than 100 percent, percent	7.00%		12.00%
Greater than 100 percent	1,886		2,821
No LTV available, percent	1.00%	[2]	2.00%	[2]
No LTV available	164	[2]	330	[2]
Total, percent	100.00%		100.00%
Total	24,078		22,670
Residential mortgage [Member]
FICO scores:
720 and above	16,024		14,553
Below 720	4,305		4,319
No FICO available	418	[1]	247	[1]
Total	20,747		19,119
LTV ratios:
Less than 80 percent	16,369		12,464
80-100 percent	2,984		4,415
Greater than 100 percent	1,296		2,146
No LTV available	99	[2]	94	[2]
Total	20,748		19,119
Home equity and other consumer loans [Member]
FICO scores:
720 and above	2,381		2,533
Below 720	967		1,044
No FICO available	68	[1]	69	[1]
Total	3,416		3,646
Home Equity Line of Credit [Member]
LTV ratios:
Less than 80 percent	2,089		2,028
80-100 percent	586		612
Greater than 100 percent	590		675
No LTV available	65	[2]	236	[2]
Total	$ 3,330		$ 3,551

[1] Represents loans for which management was not able to obtain an updated FICO score (e.g., due to recent profile changes).

[2] Represents loans for which management was not able to obtain refreshed property values.