Loans Held for Investment portfolio and Related Allowance for Loan and Lease Losses (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012	Dec. 31, 2011
Individually evaluated	$ 3,071		$ 3,078
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	361		364
Collectively evaluated	117,373		118,013
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,791		1,810
Total evaluated	120,444		121,091
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans	2,152		2,174
Loans carried at fair value	360	[1]	379	[1]
Total	120,804	[1]	121,470	[1]
Loans and Leases Receivable, Allowance	2,152		2,174		2,348	2,457
Commercial Portfolio Segment [Member]
Individually evaluated	133		138
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	3		7
Collectively evaluated	59,105		58,750
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	918		895
Total evaluated	59,238		58,888
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans	921		902
Loans carried at fair value	0		0
Total	59,238		58,888
Loans and Leases Receivable, Allowance	921		902		901	964
Residential Portfolio Segment [Member]
Individually evaluated	2,845		2,859
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	349		348
Collectively evaluated	39,076		39,961
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	738		783
Total evaluated	41,921		42,820
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans	1,087		1,131
Loans carried at fair value	360		379
Total	42,281		43,199
Loans and Leases Receivable, Allowance	1,087		1,131		1,315	1,354
Consumer Portfolio Segment [Member]
Individually evaluated	93		81
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	9		9
Collectively evaluated	19,192		19,302
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	135		132
Total evaluated	19,285		19,383
Loans And Leases Receivable Allowance Loans Evaluated For Impairment Excluding Fair Value Loans	144		141
Loans carried at fair value	0		0
Total	19,285		19,383
Loans and Leases Receivable, Allowance	$ 144		$ 141		$ 132	$ 139

[1] 2 Includes loans of consolidated VIEs355 365