Investment Securities Available For Sale Securities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 38,520	[1]	$ 51,356	[1]
Unrealized Gains	1,345	[1]	1,272	[1]
Unrealized Losses Other-than-Temporary	(86)	[1],[2]	(318)	[1],[2]
Unrealized Losses Other	(143)	[1],[3]	(373)	[1],[3]
Fair Value	39,636	[1],[4]	51,937	[1],[4]
U.S. Treasury and Agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	728	[1]	1,045	[1]
Unrealized Gains	15	[1]	13	[1]
Unrealized Losses Other			(1)	[1],[3]
Fair Value	743	[1]	1,057	[1]
Collateralized debt/loan obligation asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	33	[1]	180	[1]
Unrealized Gains	9	[1]	31	[1]
Unrealized Losses Other-than-Temporary			(3)	[1],[2]
Unrealized Losses Other			(2)	[1],[3]
Fair Value	42	[1]	206	[1]
Asset Backed Securities Other
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	585	[1]	694	[1]
Unrealized Gains	14	[1]	16	[1]
Unrealized Losses Other-than-Temporary			(5)	[1],[2]
Unrealized Losses Other	(1)	[1],[3]	(24)	[1],[3]
Fair Value	598	[1]	681	[1]
Obligations of state and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,085	[1]	6,394	[1]
Unrealized Gains	372	[1]	167	[1]
Unrealized Losses Other			(22)	[1],[3]
Fair Value	6,457	[1]	6,539	[1]
Obligations of Foreign Governments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6	[1]	6	[1]
Fair Value	6	[1]	6	[1]
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	813	[1]	1,000	[1]
Unrealized Gains	2	[1]	1	[1]
Unrealized Losses Other	(106)	[1],[3]	(174)	[1],[3]
Fair Value	709	[1]	827	[1]
Perpetual preferred securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	268	[1]	379	[1]
Unrealized Gains	29	[1]	25	[1]
Unrealized Losses Other	(19)	[1],[3]	(86)	[1],[3]
Fair Value	278	[1]	318	[1]
Other Investment [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	248	[1]	188	[1]
Unrealized Gains	20	[1]	15	[1]
Unrealized Losses Other			(1)	[1],[3]
Fair Value	268	[1]	202	[1]
Residential Agency | Residential
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	28,494	[1]	39,337	[1]
Unrealized Gains	874	[1]	981	[1]
Unrealized Losses Other	(6)	[1],[3]	(4)	[1],[3]
Fair Value	29,362	[1]	40,314	[1]
Residential non-agency prime | Residential
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	679	[1],[5]	911	[1],[5]
Unrealized Gains			5	[1],[5]
Unrealized Losses Other-than-Temporary	(38)	[1],[2],[5]	(63)	[1],[2],[5]
Unrealized Losses Other	(10)	[1],[3],[5]	(50)	[1],[3],[5]
Fair Value	631	[1],[5]	803	[1],[5]
Residential non-agency non-prime | Residential
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	388	[1],[6]	1,047	[1],[6]
Unrealized Gains	1	[1],[6]	9	[1],[6]
Unrealized Losses Other-than-Temporary	(48)	[1],[2],[6]	(247)	[1],[2],[6]
Unrealized Losses Other	(1)	[1],[3],[6]	(7)	[1],[3],[6]
Fair Value	340	[1],[6]	802	[1],[6]
Commercial Agency | Commercial Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	193	[1]	133	[1]
Unrealized Gains	9	[1]	7	[1]
Fair Value	202	[1]	140	[1]
Non-agency | Commercial Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost			42	[1]
Unrealized Gains			2	[1]
Unrealized Losses Other			(2)	[1],[3]
Fair Value			$ 42	[1]

[1] Available-for-sale investment securities are carried at fair value with unrealized net gains or losses reported within accumulated other comprehensive income (loss) in shareholders' equity.

[2] Represents impairment not related to credit for those investment securities that have been determined to be other-than-temporarily impaired.

[3] Represents unrealized losses on investment securities that have not been determined to be other-than-temporarily impaired.

[4] Includes only collateral pledged by the Company where counterparties have the right to sell or pledge the collateral.

[5] 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). When the Company determines the designation, prime securities typically have a weighted average credit score of 725 or higher and a loan-to-value of 80 percent or lower; however, other pool characteristics may result in designations that deviate from these credit score and loan-to-value thresholds.

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