Securities-Aggregate Fair Value of Investments with Continuous Unrealized Loss Position (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	$ 8,519		$ 17,297
Less than 12 months Unrealized losses	48		71
12 months or more Fair value	6,845		14,046
12 months or more Unrealized losses	363		462
Total Fair value	15,364		31,343
Total Unrealized losses	411		533
Securities available-for-sale
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	6,329	[1]	15,635	[2]
Less than 12 months Unrealized losses	42	[1]	61	[2]
12 months or more Fair value	3,996	[1]	8,087	[2]
12 months or more Unrealized losses	341	[1]	398	[2]
Total Fair value	10,325	[1]	23,722	[2]
Total Unrealized losses	383	[1],[3]	459	[2],[4]
Securities available-for-sale | U.S. Treasury
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	643		6,049
Less than 12 months Unrealized losses	4		15
12 months or more Fair value	0		0
12 months or more Unrealized losses	0		0
Total Fair value	643		6,049
Total Unrealized losses	4		15
Securities available-for-sale | U.S. Government agencies
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value			32
Less than 12 months Unrealized losses			0
12 months or more Fair value			100
12 months or more Unrealized losses			2
Total Fair value			132
Total Unrealized losses	0		2
Securities available-for-sale | State and political subdivisions
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	260		410
Less than 12 months Unrealized losses	15		18
12 months or more Fair value	300		393
12 months or more Unrealized losses	5		6
Total Fair value	560		803
Total Unrealized losses	20		24
Securities available-for-sale | Agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	789		3,385
Less than 12 months Unrealized losses	13		13
12 months or more Fair value	1,575		5,016
12 months or more Unrealized losses	278		312
Total Fair value	2,364		8,401
Total Unrealized losses	291		325
Securities available-for-sale | Non-agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	198		143
Less than 12 months Unrealized losses	1		1
12 months or more Fair value	367		382
12 months or more Unrealized losses	23		25
Total Fair value	565		525
Total Unrealized losses	24		26
Securities available-for-sale | 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	392		449
12 months or more Unrealized losses	19		25
Total Fair value	392		449
Total Unrealized losses	19		25
Securities available-for-sale | Commercial MBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	123		175
Less than 12 months Unrealized losses	0		1
12 months or more Fair value	221		394
12 months or more Unrealized losses	5		6
Total Fair value	344		569
Total Unrealized losses	5		7
Securities available-for-sale | Agency commercial MBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	853		719
Less than 12 months Unrealized losses	3		1
12 months or more Fair value	410		550
12 months or more Unrealized losses	4		8
Total Fair value	1,263		1,269
Total Unrealized losses	7		9
Securities available-for-sale | Asset-backed CLOs
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	806		1,376
Less than 12 months Unrealized losses	1		7
12 months or more Fair value	0		0
12 months or more Unrealized losses	0		0
Total Fair value	806		1,376
Total Unrealized losses	1		7
Securities available-for-sale | Other asset-backed securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	865		1,078
Less than 12 months Unrealized losses	1		2
12 months or more Fair value	505		539
12 months or more Unrealized losses	3		4
Total Fair value	1,370		1,617
Total Unrealized losses	4		6
Securities available-for-sale | Corporate bonds
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	2		51
Less than 12 months Unrealized losses	0		0
12 months or more Fair value	192		230
12 months or more Unrealized losses	2		7
Total Fair value	194		281
Total Unrealized losses	2		7
Securities available-for-sale | Sovereign debt/sovereign guaranteed
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	1,736		2,175
Less than 12 months Unrealized losses	3		2
12 months or more Fair value	0		0
12 months or more Unrealized losses	0		0
Total Fair value	1,736		2,175
Total Unrealized losses	3		2
Securities available-for-sale | Non-agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	54	[5]	42	[5]
Less than 12 months Unrealized losses	1	[5]	1	[5]
12 months or more Fair value	34	[5]	34	[5]
12 months or more Unrealized losses	2	[5]	3	[5]
Total Fair value	88	[5]	76	[5]
Total Unrealized losses	3	[5]	4	[5]
Held-to-maturity
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	2,190		1,662
Less than 12 months Unrealized losses	6		10
12 months or more Fair value	2,849		5,959
12 months or more Unrealized losses	22		64
Total Fair value	5,039		7,621
Total Unrealized losses	28		74
Held-to-maturity | U.S. Treasury
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	1,316		1,066
Less than 12 months Unrealized losses	2		6
12 months or more Fair value	198		1,559
12 months or more Unrealized losses	0		10
Total Fair value	1,514		2,625
Total Unrealized losses	2		16
Held-to-maturity | U.S. Government agencies
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value			0
Less than 12 months Unrealized losses			0
12 months or more Fair value			340
12 months or more Unrealized losses			3
Total Fair value			340
Total Unrealized losses	0		3
Held-to-maturity | State and political subdivisions
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	4		5
Less than 12 months Unrealized losses	1		1
12 months or more Fair value	0		0
12 months or more Unrealized losses	0		0
Total Fair value	4		5
Total Unrealized losses	1		1
Held-to-maturity | Agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	826		551
Less than 12 months Unrealized losses	3		3
12 months or more Fair value	2,434		3,808
12 months or more Unrealized losses	11		41
Total Fair value	3,260		4,359
Total Unrealized losses	14		44
Held-to-maturity | Non-agency RMBS
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair value	44		40
Less than 12 months Unrealized losses	0		0
12 months or more Fair value	32		33
12 months or more Unrealized losses	2		2
Total Fair value	76		73
Total Unrealized losses	2		2
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	185		219
12 months or more Unrealized losses	9		8
Total Fair value	185		219
Total Unrealized losses	9		8
Held-to-maturity | Commercial MBS
Investments, Unrealized Loss Position [Line Items]
Total Unrealized losses	0		0
Held-to-maturity | Agency commercial MBS
Investments, Unrealized Loss Position [Line Items]
Total Unrealized losses	0
Held-to-maturity | Sovereign debt/sovereign guaranteed
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 related to investment securities that were transferred from available-for-sale to held-to-maturity. The unrealized losses primarily related to Agency RMBS and 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 $282 million recorded in accumulated other comprehensive income related to investment securities that were transferred from available-for-sale to held-to-maturity. The unrealized losses primarily related to Agency RMBS and will be amortized into net interest revenue over the estimated lives of the securities.

[3] Includes gross unrealized gains of $101 million and gross unrealized losses of $296 million recorded in accumulated other comprehensive income related to investment securities that were transferred from available-for-sale to held-to-maturity. The unrealized gains and losses primarily related to Agency RMBS and will be amortized into net interest revenue over the estimated lives of the securities.

[4] Includes gross unrealized gains of $60 million and gross unrealized losses of $282 million recorded in accumulated other comprehensive income related to investment securities that were transferred from available-for-sale to held-to-maturity. The unrealized gains and losses primarily related to Agency RMBS and 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.