Securities - Amortized Cost, Gross Unrealized Gains and Losses and Fair Value of Securities (Detail) - USD ($) $ in Millions	Mar. 31, 2016		Dec. 31, 2015
Gain (Loss) on Investments [Line Items]
Amortized cost	$ 116,563		$ 118,422
Gross unrealized Gains	2,370		1,461
Gross unrealized Losses	408		812
Fair value	118,525		119,071
AOCI, transfers from AFS to HTM Securities, gross unrealized gains	78		84
AOCI, transfers from AFS to HTM Securities, gross unrealized losses	234		248
Available-for-sale
Gain (Loss) on Investments [Line Items]
Amortized cost	74,846	[1]	75,110	[2]
Gross unrealized Gains	1,828	[1]	1,274	[2]
Gross unrealized Losses	380	[1],[3]	517	[2],[4]
Fair value	76,294	[1]	75,867	[2]
Available-for-sale | U.S. Treasury
Gain (Loss) on Investments [Line Items]
Amortized cost	12,476		12,693
Gross unrealized Gains	500		175
Gross unrealized Losses	4		36
Fair value	12,972		12,832
Available-for-sale | U.S. Government agencies
Gain (Loss) on Investments [Line Items]
Amortized cost	402		386
Gross unrealized Gains	8		2
Gross unrealized Losses	0		1
Fair value	410		387
Available-for-sale | State and political subdivisions
Gain (Loss) on Investments [Line Items]
Amortized cost	3,631		3,968
Gross unrealized Gains	104		91
Gross unrealized Losses	14		13
Fair value	3,721		4,046
Available-for-sale | Agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	23,721		23,549
Gross unrealized Gains	318		239
Gross unrealized Losses	243		287
Fair value	23,796		23,501
Available-for-sale | Non-agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	746		782
Gross unrealized Gains	26		31
Gross unrealized Losses	23		20
Fair value	749		793
Available-for-sale | Other RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	993		1,072
Gross unrealized Gains	8		10
Gross unrealized Losses	21		21
Fair value	980		1,061
Available-for-sale | Commercial MBS
Gain (Loss) on Investments [Line Items]
Amortized cost	1,258		1,400
Gross unrealized Gains	17		8
Gross unrealized Losses	10		16
Fair value	1,265		1,392
Available-for-sale | Agency commercial MBS
Gain (Loss) on Investments [Line Items]
Amortized cost	4,225		4,031
Gross unrealized Gains	81		24
Gross unrealized Losses	11		35
Fair value	4,295		4,020
Available-for-sale | CLOs
Gain (Loss) on Investments [Line Items]
Amortized cost	2,441		2,363
Gross unrealized Gains	2		1
Gross unrealized Losses	19		13
Fair value	2,424		2,351
Available-for-sale | Other asset-backed securities
Gain (Loss) on Investments [Line Items]
Amortized cost	2,420		2,909
Gross unrealized Gains	3		1
Gross unrealized Losses	15		17
Fair value	2,408		2,893
Available-for-sale | Foreign covered bonds
Gain (Loss) on Investments [Line Items]
Amortized cost	2,164		2,125
Gross unrealized Gains	42		46
Gross unrealized Losses	1		3
Fair value	2,205		2,168
Available-for-sale | Corporate bonds
Gain (Loss) on Investments [Line Items]
Amortized cost	1,690		1,740
Gross unrealized Gains	49		26
Gross unrealized Losses	2		14
Fair value	1,737		1,752
Available-for-sale | Sovereign debt/sovereign guaranteed
Gain (Loss) on Investments [Line Items]
Amortized cost	13,494		13,036
Gross unrealized Gains	293		211
Gross unrealized Losses	5		30
Fair value	13,782		13,217
Available-for-sale | Other debt securities
Gain (Loss) on Investments [Line Items]
Amortized cost	2,947		2,732
Gross unrealized Gains	55		46
Gross unrealized Losses	1		3
Fair value	3,001		2,775
Available-for-sale | Equity securities
Gain (Loss) on Investments [Line Items]
Amortized cost	2		3
Gross unrealized Gains	0		1
Gross unrealized Losses	0		0
Fair value	2		4
Available-for-sale | Money market funds
Gain (Loss) on Investments [Line Items]
Amortized cost	862		886
Gross unrealized Gains	0		0
Gross unrealized Losses	0		0
Fair value	862		886
Available-for-sale | Non-agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	1,374	[5]	1,435	[6]
Gross unrealized Gains	322	[5]	362	[6]
Gross unrealized Losses	11	[5],[7]	8	[6],[8]
Fair value	1,685	[5]	1,789	[6]
Held-to-maturity
Gain (Loss) on Investments [Line Items]
Amortized cost	41,717		43,312
Gross unrealized Gains	542		187
Gross unrealized Losses	28		295
Fair value	42,231		43,204
Held-to-maturity | U.S. Treasury
Gain (Loss) on Investments [Line Items]
Amortized cost	11,327		11,326
Gross unrealized Gains	141		25
Gross unrealized Losses	0		51
Fair value	11,468		11,300
Held-to-maturity | U.S. Government agencies
Gain (Loss) on Investments [Line Items]
Amortized cost	1,488		1,431
Gross unrealized Gains	2		0
Gross unrealized Losses	0		6
Fair value	1,490		1,425
Held-to-maturity | State and political subdivisions
Gain (Loss) on Investments [Line Items]
Amortized cost	20		20
Gross unrealized Gains	0		0
Gross unrealized Losses	1		1
Fair value	19		19
Held-to-maturity | Agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	25,747		26,036
Gross unrealized Gains	338		134
Gross unrealized Losses	11		205
Fair value	26,074		25,965
Held-to-maturity | Non-agency RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	112		118
Gross unrealized Gains	4		5
Gross unrealized Losses	3		2
Fair value	113		121
Held-to-maturity | Other RMBS
Gain (Loss) on Investments [Line Items]
Amortized cost	210		224
Gross unrealized Gains	0		1
Gross unrealized Losses	13		10
Fair value	197		215
Held-to-maturity | Commercial MBS
Gain (Loss) on Investments [Line Items]
Amortized cost	9		9
Gross unrealized Gains	0		0
Gross unrealized Losses	0		0
Fair value	9		9
Held-to-maturity | Agency commercial MBS
Gain (Loss) on Investments [Line Items]
Amortized cost	562		503
Gross unrealized Gains	10		0
Gross unrealized Losses	0		9
Fair value	572		494
Held-to-maturity | Foreign covered bonds
Gain (Loss) on Investments [Line Items]
Amortized cost	80		76
Gross unrealized Gains	1		0
Gross unrealized Losses	0		0
Fair value	81		76
Held-to-maturity | Sovereign debt/sovereign guaranteed
Gain (Loss) on Investments [Line Items]
Amortized cost	2,132		3,538
Gross unrealized Gains	46		22
Gross unrealized Losses	0		11
Fair value	2,178		3,549
Held-to-maturity | Other debt securities
Gain (Loss) on Investments [Line Items]
Amortized cost	30		31
Gross unrealized Gains	0		0
Gross unrealized Losses	0		0
Fair value	$ 30		$ 31

[1] Includes gross unrealized gains of $78 million and gross unrealized losses of $234 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 are 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 $84 million and gross unrealized losses of $248 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 are primarily related to Agency RMBS and will be amortized into net interest revenue over the estimated lives of the securities.

[3] There were no gross unrealized losses for less than 12 months and gross unrealized losses for 12 months or more of $234 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 less than 12 months of $8 million and gross unrealized losses for 12 months or more of $240 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.

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

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

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