Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Securities (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Gain (Loss) on Investments [Line Items]
Amortized cost	$ 91,552		$ 80,945
Gross unrealized Gains	2,545		2,063
Gross unrealized Losses	688		1,001
Fair value	93,409		82,007
Available-for-sale
Gain (Loss) on Investments [Line Items]
Amortized cost	82,758		77,424
Gross unrealized Gains	2,357		1,917
Gross unrealized Losses	575		874
Fair value	84,540		78,467
Available-for-sale | U.S. Treasury
Gain (Loss) on Investments [Line Items]
Amortized cost	13,915		16,814
Gross unrealized Gains	555		514
Gross unrealized Losses			2
Fair value	14,470		17,326
Available-for-sale | U.S. Government Agencies
Gain (Loss) on Investments [Line Items]
Amortized cost	1,066		932
Gross unrealized Gains	31		26
Fair value	1,097		958
Available-for-sale | State And Political Subdivisions
Gain (Loss) on Investments [Line Items]
Amortized cost	5,561		2,724
Gross unrealized Gains	78		62
Gross unrealized Losses	37		47
Fair value	5,602		2,739
Available-for-sale | Agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	32,262		26,232
Gross unrealized Gains	774		575
Gross unrealized Losses	4		11
Fair value	33,032		26,796
Available-for-sale | Alt-A RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	267		306
Gross unrealized Gains	16		9
Gross unrealized Losses	25		42
Fair value	258		273
Available-for-sale | Prime RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	816		916
Gross unrealized Gains	2		1
Gross unrealized Losses	54		102
Fair value	764		815
Available-for-sale | Subprime RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	555		606
Gross unrealized Gains	3		2
Gross unrealized Losses	136		190
Fair value	422		418
Available-for-sale | Other RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	2,654		1,133
Gross unrealized Gains	9
Gross unrealized Losses	176		230
Fair value	2,487		903
Available-for-sale | Commercial MBS
Gain (Loss) on Investments [Line Items]
Amortized cost	3,269		3,327
Gross unrealized Gains	123		89
Gross unrealized Losses	72		77
Fair value	3,320		3,339
Available-for-sale | Asset-Backed CLOs
Gain (Loss) on Investments [Line Items]
Amortized cost	1,103		1,480
Gross unrealized Gains	2		1
Gross unrealized Losses	25		37
Fair value	1,080		1,444
Available-for-sale | Other Asset-Backed Securities
Gain (Loss) on Investments [Line Items]
Amortized cost	1,182		527
Gross unrealized Gains	10		8
Gross unrealized Losses	3		3
Fair value	1,189		532
Available-for-sale | Foreign Covered Bonds
Gain (Loss) on Investments [Line Items]
Amortized cost	3,870		2,410
Gross unrealized Gains	60		18
Gross unrealized Losses	2		3
Fair value	3,928		2,425
Available-for-sale | Corporate Bonds
Gain (Loss) on Investments [Line Items]
Amortized cost	1,571		1,696
Gross unrealized Gains	59		47
Gross unrealized Losses	2		5
Fair value	1,628		1,738
Available-for-sale | Other Debt Securities
Gain (Loss) on Investments [Line Items]
Amortized cost	10,980		14,320
Gross unrealized Gains	301		292
Gross unrealized Losses	1		33
Fair value	11,280	[1]	14,579	[2]
Available-for-sale | Equity Securities
Gain (Loss) on Investments [Line Items]
Amortized cost	24		26
Gross unrealized Gains	4		4
Fair value	28		30
Available-for-sale | Money Market Funds
Gain (Loss) on Investments [Line Items]
Amortized cost	918		973
Fair value	918		973
Available-for-sale | Grantor Trust Alt-A RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	1,677	[3]	1,790	[3]
Gross unrealized Gains	213	[3]	157	[3]
Gross unrealized Losses	27	[3]	68	[3]
Fair value	1,863	[3]	1,879	[3]
Available-for-sale | Grantor Trust Prime RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	956	[3]	1,090	[3]
Gross unrealized Gains	111	[3]	106	[3]
Gross unrealized Losses	8	[3]	21	[3]
Fair value	1,059	[3]	1,175	[3]
Available-for-sale | Grantor Trust Sub Prime RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	112	[3]	122	[3]
Gross unrealized Gains	6	[3]	6	[3]
Gross unrealized Losses	3	[3]	3	[3]
Fair value	115	[3]	125	[3]
Held-to-maturity
Gain (Loss) on Investments [Line Items]
Amortized cost	8,794		3,521
Gross unrealized Gains	188		146
Gross unrealized Losses	113		127
Fair value	8,869		3,540
Held-to-maturity | U.S. Treasury
Gain (Loss) on Investments [Line Items]
Amortized cost	862		813
Gross unrealized Gains	60		53
Fair value	922		866
Held-to-maturity | State And Political Subdivisions
Gain (Loss) on Investments [Line Items]
Amortized cost	79		100
Gross unrealized Gains	3		3
Fair value	82		103
Held-to-maturity | Agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	6,336		658
Gross unrealized Gains	79		39
Gross unrealized Losses	6
Fair value	6,409		697
Held-to-maturity | Alt-A RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	126		153
Gross unrealized Gains	6		4
Gross unrealized Losses	12		19
Fair value	120		138
Held-to-maturity | Prime RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	108		121
Gross unrealized Gains	1
Gross unrealized Losses	6		10
Fair value	103		111
Held-to-maturity | Subprime RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	28		28
Gross unrealized Losses	3		3
Fair value	25		25
Held-to-maturity | Other RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	1,226		1,617
Gross unrealized Gains	39		47
Gross unrealized Losses	83		93
Fair value	1,182		1,571
Held-to-maturity | Commercial MBS
Gain (Loss) on Investments [Line Items]
Amortized cost	26		28
Gross unrealized Losses	3		2
Fair value	23		26
Held-to-maturity | Other Securities
Gain (Loss) on Investments [Line Items]
Amortized cost	3		3
Fair value	$ 3		$ 3

[1] Includes $9.0 billion, at fair value, of government-sponsored and guaranteed entities, and sovereign debt.

[2] Includes $13.1 billion, at fair value, of government-sponsored and guaranteed entities, and sovereign debt.

[3] Previously included in the Grantor Trust. The Grantor Trust was dissolved in the first quarter of 2011.