Changes in Fair Value for All Assets and Liabilities Measured at Fair Value on Recurring Basis using Significant Unobservable Inputs (Level 3) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended							3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended	9 Months Ended
	Sep. 30, 2012 Residential non-agency prime		Sep. 30, 2011 Residential non-agency prime		Sep. 30, 2012 Residential non-agency prime		Sep. 30, 2011 Residential non-agency prime		Sep. 30, 2012 Residential non-agency non-prime		Sep. 30, 2011 Residential non-agency non-prime		Sep. 30, 2012 Residential non-agency non-prime		Sep. 30, 2011 Residential non-agency non-prime		Sep. 30, 2012 Commercial Non-Agency Mortgage-Backed Securities	Sep. 30, 2011 Commercial Non-Agency Mortgage-Backed Securities	Sep. 30, 2012 Commercial Non-Agency Mortgage-Backed Securities	Sep. 30, 2011 Commercial Non-Agency Mortgage-Backed Securities	Sep. 30, 2012 Collateralized Loan Obligations	Sep. 30, 2011 Collateralized Loan Obligations	Sep. 30, 2012 Collateralized Loan Obligations	Sep. 30, 2011 Collateralized Loan Obligations	Sep. 30, 2012 Asset Backed Securities Other	Sep. 30, 2012 Asset Backed Securities Other	Sep. 30, 2012 Corporate debt securities	Jun. 30, 2012 Corporate debt securities	Dec. 31, 2011 Corporate debt securities	Sep. 30, 2011 Corporate debt securities	Jun. 30, 2011 Corporate debt securities	Dec. 31, 2010 Corporate debt securities	Sep. 30, 2012 Available-for-sale Securities		Sep. 30, 2011 Available-for-sale Securities		Sep. 30, 2012 Available-for-sale Securities		Sep. 30, 2011 Available-for-sale Securities		Sep. 30, 2012 Mortgage servicing rights		Sep. 30, 2011 Mortgage servicing rights		Sep. 30, 2012 Mortgage servicing rights		Sep. 30, 2011 Mortgage servicing rights		Sep. 30, 2012 Net derivative assets and liabilities		Sep. 30, 2011 Net derivative assets and liabilities		Sep. 30, 2012 Net derivative assets and liabilities		Sep. 30, 2011 Net derivative assets and liabilities		Sep. 30, 2011 Other asset-backed securities	Sep. 30, 2011 Other asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning of Period Balance	$ 713	[1]	$ 896	[1]	$ 803	[1]	$ 1,103	[1]	$ 796	[2]	$ 895	[2]	$ 802	[2]	$ 947	[2]	$ 37	$ 50	$ 42	$ 50	$ 102	$ 133	$ 120	$ 135	$ 112	$ 117	$ 9	$ 9	$ 9	$ 9	$ 9	$ 9	$ 1,769		$ 2,112		$ 1,893		$ 2,377		$ 1,594		$ 1,989		$ 1,519		$ 1,837		$ 1,360		$ 836		$ 1,228		$ 851		$ 129	$ 133
Net Gains (Losses) Included in Net Income	(4)	[1]	1	[1]	(5)	[1]	4	[1]	(8)	[2]	(2)	[2]	(18)	[2]	(4)	[2]		1	1	2	2	3	12	10	1	7							(9)	[3]	4	[4]	(3)	[5]	20	[6]	(275)	[7]	(629)	[7]	(705)	[7]	(803)	[7]	843	[8]	836	[9]	2,050	[10]	1,252	[11]	1	8
Net Gains (Losses) Included in Other Comprehensive Income (Loss)	23	[1]	(2)	[1]	60	[1]	22	[1]	132	[2]	(5)	[2]	197	[2]	27	[2]	2	(1)		(1)	(7)	(2)	(8)	6	(4)								146	[12]	(14)	[12]	249	[12]	52	[12]																	(4)	(2)
Purchases																									3	3							3				3				10		5		39		16		1				1
Sales	(61)	[1]			(109)	[1]	(115)	[1]	(562)	[2]			(562)	[2]	(12)	[2]	(39)	(4)	(39)	(4)	(96)		(103)		(93)	(93)							(851)		(4)		(906)		(131)										(1)		(2)		(3)		(5)
Principal Payments	(40)	[1]	(36)	[1]	(118)	[1]	(155)	[1]	(18)	[2]	(31)	[2]	(79)	[2]	(101)	[2]		(1)	(4)	(2)	(1)	(9)	(21)	(26)	(3)	(18)							(62)		(83)		(240)		(303)																		(6)	(19)
Issuances																																									224	[13]	101	[13]	700	[13]	416	[13]
Settlements																																																	(713)		(340)		(1,786)		(768)
End of Period Balance	631	[1]	859	[1]	631	[1]	859	[1]	340	[2]	857	[2]	340	[2]	857	[2]		45		45		125		125	16	16	9	9	9	9	9	9	996		2,015		996		2,015		1,553		1,466		1,553		1,466		1,490		1,330		1,490		1,330		120	120
Net Change in Unrealized Gains (Losses) Relating to Assets Still Held at End of Period	$ 26	[1]	$ (2)	[1]	$ 58	[1]	$ 14	[1]	$ 23	[2]	$ (5)	[2]	$ 52	[2]	$ 26	[2]						$ (2)		$ 7	$ 2	$ 2							$ 51		$ (13)		$ 112		$ 45		$ (275)	[7]	$ (629)	[7]	$ (705)	[7]	$ (803)	[7]	$ (557)	[14]	$ 77	[15]	$ (1,407)	[16]	$ (92)	[17]	$ (4)	$ (2)

[1] Prime securities are those designated as such by the issuer at origination. When an issuer designation is unavailable, the Company determines at acquisition date the categorization based on asset pool characteristics (such as weighted-average credit score, loan-to-value, loan type, prevalence of low documentation loans) and deal performance (such as pool delinquencies and security market spreads).

[2] Includes all securities not meeting the conditions to be designated as prime.

[3] Approximately $(15) million included in securities gains (losses) and $6 million included in interest income.

[4] Approximately $(9) million included in other securities gains (losses) and $13 million included in interest income.

[5] Approximately $(37) million included in securities gains (losses) and $34 million included in interest income.

[6] Approximately $(24) million included in securities gains (losses) and $44 million included in interest income.

[7] Included in mortgage banking revenue.

[8] Approximately $124 million included in other noninterest income and $719 million included in mortgage banking revenue.

[9] Approximately $445 million included in other noninterest income and $391 million included in mortgage banking revenue.

[10] Approximately $344 million included in other noninterest income and $1.7 billion included in mortgage banking revenue.

[11] Approximately $672 million included in other noninterest income and $580 million included in mortgage banking revenue.

[12] Included in changes in unrealized gains and losses on securities available-for-sale.

[13] Represents MSRs capitalized during the period.

[14] Approximately $7 million included in other noninterest income and $(564) million included in mortgage banking revenue.

[15] Approximately $317 million included in other noninterest income and $(240) million included in mortgage banking revenue.

[16] Approximately $6 million included in other noninterest income and $1.4 billion included in mortgage banking revenue.

[17] Approximately $303 million included in other noninterest income and $(395) million included in mortgage banking revenue.