Securities-Aggregate Fair Value of Investments with Continuous Unrealized Loss Position (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	$ 21,635		$ 45,453
Less than 12 months Unrealized losses	88		1,359
12 months or more Fair value	21,350		2,071
12 months or more Unrealized losses	696		478
Total Fair value	42,985		47,524
Total Unrealized losses	784		1,837
Securities available-for-sale
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	18,974	[1]	29,479	[2]
Less than 12 months Unrealized losses	71	[1]	1,020	[2]
12 months or more Fair value	13,713	[1]	1,745	[2]
12 months or more Unrealized losses	556	[1]	455	[2]
Total Fair value	32,687	[1]	31,224	[2]
Total Unrealized losses	627	[1],[3]	1,475	[2],[4]
Securities available-for-sale | U.S. Treasury
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	8,717		7,719
Less than 12 months Unrealized losses	20		605
12 months or more Fair value	2,870		0
12 months or more Unrealized losses	69		0
Total Fair value	11,587		7,719
Total Unrealized losses	89		605
Securities available-for-sale | U.S. Government agencies
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	0		97
Less than 12 months Unrealized losses	0		5
12 months or more Fair value	98		0
12 months or more Unrealized losses	3		0
Total Fair value	98		97
Total Unrealized losses	3		5
Securities available-for-sale | State and political subdivisions
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	126		2,374
Less than 12 months Unrealized losses	18		55
12 months or more Fair value	471		222
12 months or more Unrealized losses	7		37
Total Fair value	597		2,596
Total Unrealized losses	25		92
Securities available-for-sale | Agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	6,492		12,011
Less than 12 months Unrealized losses	26		226
12 months or more Fair value	7,136		83
12 months or more Unrealized losses	379		324
Total Fair value	13,628		12,094
Total Unrealized losses	405		550
Securities available-for-sale | Non-agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	48		102
Less than 12 months Unrealized losses	0		7
12 months or more Fair value	400		592
12 months or more Unrealized losses	26		43
Total Fair value	448		694
Total Unrealized losses	26		50
Securities available-for-sale | Other RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	159		93
Less than 12 months Unrealized losses	0		14
12 months or more Fair value	512		614
12 months or more Unrealized losses	25		43
Total Fair value	671		707
Total Unrealized losses	25		57
Securities available-for-sale | Commercial MBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	208		517
Less than 12 months Unrealized losses	1		21
12 months or more Fair value	441		174
12 months or more Unrealized losses	11		6
Total Fair value	649		691
Total Unrealized losses	12		27
Securities available-for-sale | Agency commercial MBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	631		1,390
Less than 12 months Unrealized losses	2		34
12 months or more Fair value	592		0
12 months or more Unrealized losses	12		0
Total Fair value	1,223		1,390
Total Unrealized losses	14		34
Securities available-for-sale | Other asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	636		1,529
Less than 12 months Unrealized losses	1		9
12 months or more Fair value	586		38
12 months or more Unrealized losses	5		0
Total Fair value	1,222		1,567
Total Unrealized losses	6		9
Securities available-for-sale | Foreign covered bonds
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	342
Less than 12 months Unrealized losses	1
12 months or more Fair value	0
12 months or more Unrealized losses	0
Total Fair value	342
Total Unrealized losses	1		0
Securities available-for-sale | Corporate bonds
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	22		612
Less than 12 months Unrealized losses	0		25
12 months or more Fair value	236		0
12 months or more Unrealized losses	10		0
Total Fair value	258		612
Total Unrealized losses	10		25
Securities available-for-sale | Other debt securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	1,568		2,976
Less than 12 months Unrealized losses	1		18
12 months or more Fair value	326		0
12 months or more Unrealized losses	6		0
Total Fair value	1,894		2,976
Total Unrealized losses	7		18
Securities available-for-sale | Non-agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	25	[5]	59	[5]
Less than 12 months Unrealized losses	1	[5]	1	[5]
12 months or more Fair value	45	[5]	22	[5]
12 months or more Unrealized losses	3	[5]	2	[5]
Total Fair value	70	[5]	81	[5]
Total Unrealized losses	4	[5]	3	[5],[6]
Held-to-maturity:
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	2,661		15,974
Less than 12 months Unrealized losses	17		339
12 months or more Fair value	7,637		326
12 months or more Unrealized losses	140		23
Total Fair value	10,298		16,300
Total Unrealized losses	157		362
Held-to-maturity: | U.S. Treasury
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	1,009		2,278
Less than 12 months Unrealized losses	9		84
12 months or more Fair value	1,782		0
12 months or more Unrealized losses	35		0
Total Fair value	2,791		2,278
Total Unrealized losses	44		84
Held-to-maturity: | U.S. Government agencies
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	0		406
Less than 12 months Unrealized losses	0		13
12 months or more Fair value	337		0
12 months or more Unrealized losses	6		0
Total Fair value	337		406
Total Unrealized losses	6		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	1,651		12,639
Less than 12 months Unrealized losses	8		236
12 months or more Fair value	5,260		0
12 months or more Unrealized losses	86		0
Total Fair value	6,911		12,639
Total Unrealized losses	94		236
Held-to-maturity: | Non-agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	1		10
Less than 12 months Unrealized losses	0		0
12 months or more Fair value	25		65
12 months or more Unrealized losses	2		3
Total Fair value	26		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	233		261
12 months or more Unrealized losses	11		20
Total Fair value	233		261
Total Unrealized losses	11		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] Includes gross unrealized losses for 12 months or more of $296 million recorded in accumulated other comprehensive income primarily related to Agency RMBS that were transferred from available-for-sale to held-to-maturity in 2013. The unrealized gains and losses will be amortized into net interest revenue over the estimated lives of the securities.

[2] Includes gross unrealized losses for 12 months or more of $343 million recorded in accumulated other comprehensive income primarily related to Agency RMBS that were transferred from available-for-sale to held-to-maturity in 2013. The unrealized gains and losses will be amortized into net interest revenue over the estimated lives of the securities.

[3] Includes gross unrealized gains of $64 million and gross unrealized losses of $296 million recorded in accumulated other comprehensive income primarily related to Agency RMBS that were transferred from available-for-sale to held-to-maturity in 2013. The unrealized gains and losses will be amortized into net interest revenue over the estimated lives of the securities.

[4] Includes gross unrealized gains of $74 million and gross unrealized losses of $343 million recorded in accumulated other comprehensive income primarily related to Agency RMBS that were transferred from available-for-sale to held-to-maturity in 2013. The unrealized gains and losses will be amortized into net interest revenue over the estimated lives of the securities.

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

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