Loans and Allowance for Loan Losses - FICO Credit Scores and LTV Ratios Related to Loans in Consumer Portfolio Segment and Consumer Loans (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
720 and above percent	76.00%	76.00%
Below 720 percent	23.00%	22.00%
No FICO available percent	1.00%	2.00%
Total percent	100.00%	100.00%
Less than 80 percent	88.00%	77.00%
80-100 percent	9.00%	14.00%
Greater than 100 percent	3.00%	8.00%
No LTV available percent		1.00%
Total percent	100.00%	100.00%
Residential mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
720 and above	$ 17,824	$ 17,103
Below 720	4,909	4,666
No FICO available	208	395
Total	22,941	22,164
Less than 80 percent	20,609	17,771
80-100 percent	1,906	3,031
Greater than 100 percent	422	1,232
No LTV available	4	130
Total	22,941	22,164
Home equity and other consumer loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
720 and above	2,405	2,464
Below 720	921	986
No FICO available	54	122
Total	3,380	3,572
Home equity loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Less than 80 percent	2,470	2,216
80-100 percent	446	618
Greater than 100 percent	298	540
No LTV available	58	113
Total	3,272	3,487
Total consumer portfolio [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
720 and above	20,229	19,567
Below 720	5,830	5,652
No FICO available	262	517
Total	26,321	25,736
Less than 80 percent	23,079	19,987
80-100 percent	2,352	3,649
Greater than 100 percent	720	1,772
No LTV available	62	243
Total	26,213	25,651
Purchased Credit Impaired [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
720 and above	95	106
Below 720	164	172
No FICO available	12	10
Total	271	288
Less than 80 percent	158	72
80-100 percent	50	50
Greater than 100 percent	57	153
No LTV available		13
Total	265	288
Consumer portfolio [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
720 and above	20,324	19,673
Below 720	5,994	5,824
No FICO available	274	527
Total	26,592	26,024
Less than 80 percent	23,237	20,059
80-100 percent	2,402	3,699
Greater than 100 percent	777	1,925
No LTV available	62	256
Total	$ 26,478	$ 25,939