Securities-Aggregate Fair Value of Investments with Continuous Unrealized Loss Position (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	$ 38,969		$ 45,453
Less than 12 months Unrealized losses	863		1,359
12 months or more Fair value	1,770		2,071
12 months or more Unrealized losses	412		478
Total Fair value	40,739		47,524
Total Unrealized losses	1,275		1,837
Securities available-for-sale
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	28,362		29,479
Less than 12 months Unrealized losses	639		1,020
12 months or more Fair value	1,478		1,745
12 months or more Unrealized losses	391		455
Total Fair value	29,840		31,224
Total Unrealized losses	1,030		1,475
Securities available-for-sale | U.S. Treasury
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	8,750		7,719
Less than 12 months Unrealized losses	336		605
12 months or more Fair value	0		0
12 months or more Unrealized losses	0		0
Total Fair value	8,750		7,719
Total Unrealized losses	336		605
Securities available-for-sale | U.S. Government agencies
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	98		97
Less than 12 months Unrealized losses	4		5
12 months or more Fair value	0		0
12 months or more Unrealized losses	0		0
Total Fair value	98		97
Total Unrealized losses	4		5
Securities available-for-sale | State and political subdivisions
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	1,875		2,374
Less than 12 months Unrealized losses	51		55
12 months or more Fair value	131		222
12 months or more Unrealized losses	6		37
Total Fair value	2,006		2,596
Total Unrealized losses	57		92
Securities available-for-sale | Agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	12,657		12,011
Less than 12 months Unrealized losses	169		226
12 months or more Fair value	76		83
12 months or more Unrealized losses	313		324
Total Fair value	12,733		12,094
Total Unrealized losses	482		550
Securities available-for-sale | Non-agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	22		102
Less than 12 months Unrealized losses	1		7
12 months or more Fair value	556		592
12 months or more Unrealized losses	38		43
Total Fair value	578		694
Total Unrealized losses	39		50
Securities available-for-sale | Other RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	80		93
Less than 12 months Unrealized losses	12		14
12 months or more Fair value	504		614
12 months or more Unrealized losses	27		43
Total Fair value	584		707
Total Unrealized losses	39		57
Securities available-for-sale | Commercial MBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	455		517
Less than 12 months Unrealized losses	13		21
12 months or more Fair value	155		174
12 months or more Unrealized losses	5		6
Total Fair value	610		691
Total Unrealized losses	18		27
Securities available-for-sale | Agency commercial MBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	1,364		1,390
Less than 12 months Unrealized losses	22		34
12 months or more Fair value	0		0
12 months or more Unrealized losses	0		0
Total Fair value	1,364		1,390
Total Unrealized losses	22		34
Securities available-for-sale | Asset-backed CLOs
Investments, Unrealized Loss Position [Line Items]
Total Unrealized losses	0		0
Securities available-for-sale | Other asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	1,181		1,529
Less than 12 months Unrealized losses	6		9
12 months or more Fair value	35		38
12 months or more Unrealized losses	0		0
Total Fair value	1,216		1,567
Total Unrealized losses	6		9
Securities available-for-sale | Corporate bonds
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	313		612
Less than 12 months Unrealized losses	15		25
12 months or more Fair value	0		0
12 months or more Unrealized losses	0		0
Total Fair value	313		612
Total Unrealized losses	15		25
Securities available-for-sale | Other debt securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	1,531		2,976
Less than 12 months Unrealized losses	9		18
12 months or more Fair value	0		0
12 months or more Unrealized losses	0		0
Total Fair value	1,531		2,976
Total Unrealized losses	9		18
Securities available-for-sale | Non-agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	36	[1]	59	[1]
Less than 12 months Unrealized losses	1	[1]	1	[1]
12 months or more Fair value	21	[1]	22	[1]
12 months or more Unrealized losses	2	[1]	2	[1]
Total Fair value	57	[1]	81	[1]
Total Unrealized losses	3	[1]	3	[1],[2]
Held-to-maturity:
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	10,607		15,974
Less than 12 months Unrealized losses	224		339
12 months or more Fair value	292		326
12 months or more Unrealized losses	21		23
Total Fair value	10,899		16,300
Total Unrealized losses	245		362
Held-to-maturity: | U.S. Treasury
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	2,301		2,278
Less than 12 months Unrealized losses	55		84
12 months or more Fair value	0		0
12 months or more Unrealized losses	0		0
Total Fair value	2,301		2,278
Total Unrealized losses	55		84
Held-to-maturity: | U.S. Government agencies
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	410		406
Less than 12 months Unrealized losses	9		13
12 months or more Fair value	0		0
12 months or more Unrealized losses	0		0
Total Fair value	410		406
Total Unrealized losses	9		13
Held-to-maturity: | State and political subdivisions
Investments, Unrealized Loss Position [Line Items]
Total Unrealized losses	0		0
Held-to-maturity: | Agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	7,885		12,639
Less than 12 months Unrealized losses	160		236
12 months or more Fair value	0		0
12 months or more Unrealized losses	0		0
Total Fair value	7,885		12,639
Total Unrealized losses	160		236
Held-to-maturity: | Non-agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	11		10
Less than 12 months Unrealized losses	0		0
12 months or more Fair value	36		65
12 months or more Unrealized losses	2		3
Total Fair value	47		75
Total Unrealized losses	2		3
Held-to-maturity: | Other RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	0		0
Less than 12 months Unrealized losses	0		0
12 months or more Fair value	256		261
12 months or more Unrealized losses	19		20
Total Fair value	256		261
Total Unrealized losses	19		20
Held-to-maturity: | Other securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value			641
Less than 12 months Unrealized losses			6
12 months or more Fair value			0
12 months or more Unrealized losses			0
Total Fair value			641
Total Unrealized losses	0		6
Held-to-maturity: | Commercial MBS
Investments, Unrealized Loss Position [Line Items]
Total Unrealized losses	$ 0		$ 0

[1] Previously included in the Grantor Trust. The Grantor Trust was dissolved in 2011.

[2] Previously included in the Grantor Trust. The Grantor Trust was dissolved in 2011