Securities-Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Securities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Gain (Loss) on Investments [Line Items]
Amortized cost	$ 104,365		$ 98,332
Gross unrealized Gains	2,716		3,039
Gross unrealized Losses	358		363
Fair value	106,723		101,008
Available-for-sale
Gain (Loss) on Investments [Line Items]
Amortized cost	92,687		90,127
Gross unrealized Gains	2,495		2,793
Gross unrealized Losses	304		301
Fair value	94,878		92,619
Available-for-sale | U.S. Treasury
Gain (Loss) on Investments [Line Items]
Amortized cost	17,480		17,539
Gross unrealized Gains	348		467
Gross unrealized Losses	36		3
Fair value	17,792		18,003
Available-for-sale | U.S. Government agencies
Gain (Loss) on Investments [Line Items]
Amortized cost	1,034		1,044
Gross unrealized Gains	26		30
Gross unrealized Losses	0		0
Fair value	1,060		1,074
Available-for-sale | State and political subdivisions
Gain (Loss) on Investments [Line Items]
Amortized cost	6,162		6,039
Gross unrealized Gains	116		112
Gross unrealized Losses	28		29
Fair value	6,250		6,122
Available-for-sale | Agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	35,763		33,355
Gross unrealized Gains	720		846
Gross unrealized Losses	30		8
Fair value	36,453		34,193
Available-for-sale | Alt-A RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	249		255
Gross unrealized Gains	49		40
Gross unrealized Losses	13		16
Fair value	285		279
Available-for-sale | Prime RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	613		728
Gross unrealized Gains	10		9
Gross unrealized Losses	7		9
Fair value	616		728
Available-for-sale | Subprime RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	472		508
Gross unrealized Gains	5		6
Gross unrealized Losses	41		62
Fair value	436		452
Available-for-sale | Other RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	2,672		2,850
Gross unrealized Gains	57		53
Gross unrealized Losses	94		109
Fair value	2,635		2,794
Available-for-sale | Commercial MBS
Gain (Loss) on Investments [Line Items]
Amortized cost	2,856		3,031
Gross unrealized Gains	123		153
Gross unrealized Losses	39		45
Fair value	2,940		3,139
Available-for-sale | Asset-backed CLOs
Gain (Loss) on Investments [Line Items]
Amortized cost	1,449		1,285
Gross unrealized Gains	12		7
Gross unrealized Losses	5		10
Fair value	1,456		1,282
Available-for-sale | Other asset-backed securities
Gain (Loss) on Investments [Line Items]
Amortized cost	2,019		2,123
Gross unrealized Gains	10		11
Gross unrealized Losses	3		3
Fair value	2,026		2,131
Available-for-sale | Foreign covered bonds
Gain (Loss) on Investments [Line Items]
Amortized cost	3,349		3,596
Gross unrealized Gains	41		122
Gross unrealized Losses	0		0
Fair value	3,390		3,718
Available-for-sale | Corporate bonds
Gain (Loss) on Investments [Line Items]
Amortized cost	1,517		1,525
Gross unrealized Gains	60		63
Gross unrealized Losses	5		3
Fair value	1,572		1,585
Available-for-sale | Other debt securities
Gain (Loss) on Investments [Line Items]
Amortized cost	12,154		11,516
Gross unrealized Gains	245		276
Gross unrealized Losses	0		0
Fair value	12,399	[1]	11,792	[2]
Available-for-sale | Equity securities
Gain (Loss) on Investments [Line Items]
Amortized cost	22		23
Gross unrealized Gains	6		4
Gross unrealized Losses	0		0
Fair value	28		27
Available-for-sale | Money market funds
Gain (Loss) on Investments [Line Items]
Amortized cost	2,457		2,190
Gross unrealized Gains	0		0
Gross unrealized Losses	0		0
Fair value	2,457		2,190
Available-for-sale | Alt-A RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	1,514	[3]	1,574	[3]
Gross unrealized Gains	457	[3]	400	[3]
Gross unrealized Losses	3	[3]	4	[3]
Fair value	1,968	[3]	1,970	[3]
Available-for-sale | Prime RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	791	[3]	833	[3]
Gross unrealized Gains	190	[3]	177	[3]
Gross unrealized Losses	0	[3]	0	[3]
Fair value	981	[3]	1,010	[3]
Available-for-sale | Sub Prime RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	114	[3]	113	[3]
Gross unrealized Gains	20	[3]	17	[3]
Gross unrealized Losses	0	[3]	0	[3]
Fair value	134	[3]	130	[3]
Held-to-maturity
Gain (Loss) on Investments [Line Items]
Amortized cost	11,678		8,205
Gross unrealized Gains	221		246
Gross unrealized Losses	54		62
Fair value	11,845		8,389
Held-to-maturity | U.S. Treasury
Gain (Loss) on Investments [Line Items]
Amortized cost	2,206		1,011
Gross unrealized Gains	71		59
Gross unrealized Losses	0		0
Fair value	2,277		1,070
Held-to-maturity | State and political subdivisions
Gain (Loss) on Investments [Line Items]
Amortized cost	53		67
Gross unrealized Gains	2		2
Gross unrealized Losses	0		0
Fair value	55		69
Held-to-maturity | Agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	8,246		5,879
Gross unrealized Gains	107		139
Gross unrealized Losses	2		1
Fair value	8,351		6,017
Held-to-maturity | Alt-A RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	102		111
Gross unrealized Gains	10		9
Gross unrealized Losses	6		6
Fair value	106		114
Held-to-maturity | Prime RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	91		97
Gross unrealized Gains	1		1
Gross unrealized Losses	0		1
Fair value	92		97
Held-to-maturity | Subprime RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	28		28
Gross unrealized Gains	0		0
Gross unrealized Losses	0		1
Fair value	28		27
Held-to-maturity | Other RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	804		983
Gross unrealized Gains	29		36
Gross unrealized Losses	45		52
Fair value	788		967
Held-to-maturity | Commercial MBS
Gain (Loss) on Investments [Line Items]
Amortized cost	21		26
Gross unrealized Gains	0		0
Gross unrealized Losses	1		1
Fair value	20		25
Held-to-maturity | Other securities
Gain (Loss) on Investments [Line Items]
Amortized cost	127		3
Gross unrealized Gains	1		0
Gross unrealized Losses	0		0
Fair value	$ 128		$ 3

[1] Includes $10.2 billion, at fair value, of government-sponsored and guaranteed entities, and sovereign debt.

[2] Includes $9.4 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 2011.