Securities-Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Securities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Gain (Loss) on Investments [Line Items]
Amortized cost	$ 127,214		$ 117,868
Gross unrealized Gains	2,590		2,122
Gross unrealized Losses	411		533
Fair value	129,393		119,457
AOCI, transfers from AFS to HTM Securities, gross unrealized gains	101		60
AOCI, transfers from AFS to HTM Securities, gross unrealized losses	296		282
Available-for-sale
Gain (Loss) on Investments [Line Items]
Amortized cost	85,977	[1]	96,935	[2]
Gross unrealized Gains	2,123	[1]	1,854	[2]
Gross unrealized Losses	383	[1],[3]	459	[2],[4]
Fair value	87,717	[1]	98,330	[2]
Available-for-sale | U.S. Treasury
Gain (Loss) on Investments [Line Items]
Amortized cost	18,042		19,592
Gross unrealized Gains	548		420
Gross unrealized Losses	4		15
Fair value	18,586		19,997
Available-for-sale | U.S. Government agencies
Gain (Loss) on Investments [Line Items]
Amortized cost	383		342
Gross unrealized Gains	2		3
Gross unrealized Losses	0		2
Fair value	385		343
Available-for-sale | State and political subdivisions
Gain (Loss) on Investments [Line Items]
Amortized cost	5,053		5,176
Gross unrealized Gains	106		95
Gross unrealized Losses	20		24
Fair value	5,139		5,247
Available-for-sale | Agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	25,029		32,568
Gross unrealized Gains	445		357
Gross unrealized Losses	291		325
Fair value	25,183		32,600
Available-for-sale | Non-agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	908		942
Gross unrealized Gains	36		37
Gross unrealized Losses	24		26
Fair value	920		953
Available-for-sale | Other RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	1,382		1,551
Gross unrealized Gains	23		25
Gross unrealized Losses	19		25
Fair value	1,386		1,551
Available-for-sale | Commercial MBS
Gain (Loss) on Investments [Line Items]
Amortized cost	1,812		1,927
Gross unrealized Gains	44		39
Gross unrealized Losses	5		7
Fair value	1,851		1,959
Available-for-sale | Agency commercial MBS
Gain (Loss) on Investments [Line Items]
Amortized cost	3,728		3,105
Gross unrealized Gains	64		36
Gross unrealized Losses	7		9
Fair value	3,785		3,132
Available-for-sale | Asset-backed CLOs
Gain (Loss) on Investments [Line Items]
Amortized cost	2,250		2,128
Gross unrealized Gains	9		9
Gross unrealized Losses	1		7
Fair value	2,258		2,130
Available-for-sale | Other asset-backed securities
Gain (Loss) on Investments [Line Items]
Amortized cost	3,398		3,241
Gross unrealized Gains	6		5
Gross unrealized Losses	4		6
Fair value	3,400		3,240
Available-for-sale | Foreign covered bonds
Gain (Loss) on Investments [Line Items]
Amortized cost	2,732		2,788
Gross unrealized Gains	76		80
Gross unrealized Losses	0		0
Fair value	2,808		2,868
Available-for-sale | Corporate bonds
Gain (Loss) on Investments [Line Items]
Amortized cost	1,695		1,747
Gross unrealized Gains	52		45
Gross unrealized Losses	2		7
Fair value	1,745		1,785
Available-for-sale | Sovereign debt/sovereign guaranteed
Gain (Loss) on Investments [Line Items]
Amortized cost	14,988		17,062
Gross unrealized Gains	258		224
Gross unrealized Losses	3		2
Fair value	15,243		17,284
Available-for-sale | Other debt securities
Gain (Loss) on Investments [Line Items]
Amortized cost	2,057		2,162
Gross unrealized Gains	11		7
Gross unrealized Losses	0		0
Fair value	2,068		2,169
Available-for-sale | Equity securities
Gain (Loss) on Investments [Line Items]
Amortized cost	91		94
Gross unrealized Gains	1		1
Gross unrealized Losses	0		0
Fair value	92		95
Available-for-sale | Money market funds
Gain (Loss) on Investments [Line Items]
Amortized cost	730		763
Gross unrealized Gains	0		0
Gross unrealized Losses	0		0
Fair value	730		763
Available-for-sale | Non-agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	1,699	[5]	1,747	[5]
Gross unrealized Gains	442	[5]	471	[5]
Gross unrealized Losses	3	[5]	4	[5]
Fair value	2,138	[5]	2,214	[5]
Held-to-maturity
Gain (Loss) on Investments [Line Items]
Amortized cost	41,237		20,933
Gross unrealized Gains	467		268
Gross unrealized Losses	28		74
Fair value	41,676		21,127
Held-to-maturity | U.S. Treasury
Gain (Loss) on Investments [Line Items]
Amortized cost	10,372		5,047
Gross unrealized Gains	92		32
Gross unrealized Losses	2		16
Fair value	10,462		5,063
Held-to-maturity | U.S. Government agencies
Gain (Loss) on Investments [Line Items]
Amortized cost	1,168		344
Gross unrealized Gains	1		0
Gross unrealized Losses	0		3
Fair value	1,169		341
Held-to-maturity | State and political subdivisions
Gain (Loss) on Investments [Line Items]
Amortized cost	21		24
Gross unrealized Gains	0		1
Gross unrealized Losses	1		1
Fair value	20		24
Held-to-maturity | Agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	25,606		14,006
Gross unrealized Gains	326		200
Gross unrealized Losses	14		44
Fair value	25,918		14,162
Held-to-maturity | Non-agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	144		153
Gross unrealized Gains	8		9
Gross unrealized Losses	2		2
Fair value	150		160
Held-to-maturity | Other RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	267		315
Gross unrealized Gains	3		2
Gross unrealized Losses	9		8
Fair value	261		309
Held-to-maturity | Commercial MBS
Gain (Loss) on Investments [Line Items]
Amortized cost	11		13
Gross unrealized Gains	0		0
Gross unrealized Losses	0		0
Fair value	11		13
Held-to-maturity | Agency commercial MBS
Gain (Loss) on Investments [Line Items]
Amortized cost	359
Gross unrealized Gains	4
Gross unrealized Losses	0
Fair value	363
Held-to-maturity | Sovereign debt/sovereign guaranteed
Gain (Loss) on Investments [Line Items]
Amortized cost	3,289		1,031
Gross unrealized Gains	33		24
Gross unrealized Losses	0		0
Fair value	3,322		1,055
Held-to-maturity | Agency MBS, Sovereign Debt and U.S Treasury Securities
Gain (Loss) on Investments [Line Items]
Amortized cost	11,600
Fair value	$ 11,600

[1] 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.

[2] 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.

[3] 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.

[4] 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.

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