Securities - Amortized Cost and Fair Value of Asset Backed Securities (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Sep. 30, 2014		Dec. 31, 2013
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	$ 29,238	[1]	$ 54,935	[1]
Unrealized Gains, Available-for-sale securities	729		698
Unrealized Losses, Available-for-sale securities	(166)		(727)
Fair Value, Available-for-sale securities	29,801		54,906
Amortized Cost, Held-to-Maturity Securities	12,133	[1]	1,462	[1]
Non-Credit Loss Component of OTTI Securities, Held-to-Maturity Securities	(88)		(104)
Unrealized Gains, Held-to-maturity securities	177		141
Unrealized Losses, Held-to-maturity securities	(1)		0
Held-to-maturity Securities, Fair Value	12,221		1,499
Available-for-sale Securities, Transfers to Held-to-maturity Securities, Fair Value	10,985
Accumulated Other Comprehensive Income (Loss), Net Unrealized Gains (Losses) on Transfers from Available-for-Sale to Held-to Maturity Securities, Before Tax	234
U.S. Treasury [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	13,088	[1]	27,716	[1]
Unrealized Gains, Available-for-sale securities	351		391
Unrealized Losses, Available-for-sale securities	(34)		(113)
Fair Value, Available-for-sale securities	13,405		27,994
Mortgage-backed securities [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	506	[1],[2]	159	[1],[2]
Unrealized Gains, Available-for-sale securities	0	[2]	0	[2]
Unrealized Losses, Available-for-sale securities	(5)	[2]	(14)	[2]
Fair Value, Available-for-sale securities	501	[2]	145	[2]
Amortized Cost, Held-to-Maturity Securities	4,402	[1],[3]	845	[1],[3]
Non-Credit Loss Component of OTTI Securities, Held-to-Maturity Securities	0	[3]
Unrealized Gains, Held-to-maturity securities	79	[3]	88	[3]
Unrealized Losses, Held-to-maturity securities	(1)	[3]	0	[3]
Held-to-maturity Securities, Fair Value	4,480	[3]	933	[3]
Collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	29	[1],[2]	41	[1],[2]
Unrealized Gains, Available-for-sale securities	0	[2]	0	[2]
Unrealized Losses, Available-for-sale securities	0	[2]	(1)	[2]
Fair Value, Available-for-sale securities	29	[2]	40	[2]
Direct agency obligations [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	3,977	[1],[2]	4,115	[1],[2]
Unrealized Gains, Available-for-sale securities	251	[2]	225	[2]
Unrealized Losses, Available-for-sale securities	(8)	[2]	(16)	[2]
Fair Value, Available-for-sale securities	4,220	[2]	4,324	[2]
Mortgage-backed securities, issued or guaranteed by US Government agency [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	5,887	[1]	10,304	[1]
Unrealized Gains, Available-for-sale securities	101		40
Unrealized Losses, Available-for-sale securities	(79)		(342)
Fair Value, Available-for-sale securities	5,909		10,002
Amortized Cost, Held-to-Maturity Securities	3,028	[1]	52	[1]
Non-Credit Loss Component of OTTI Securities, Held-to-Maturity Securities	0
Unrealized Gains, Held-to-maturity securities	9		8
Unrealized Losses, Held-to-maturity securities	0		0
Held-to-maturity Securities, Fair Value	3,037		60
Collateralized mortgage obligations, issued or guaranteed by US Government agency [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	290	[1]	6,584	[1]
Unrealized Gains, Available-for-sale securities	3		17
Unrealized Losses, Available-for-sale securities	(4)		(154)
Fair Value, Available-for-sale securities	289		6,447
Amortized Cost, Held-to-Maturity Securities	4,503	[1]	214	[1]
Non-Credit Loss Component of OTTI Securities, Held-to-Maturity Securities	0
Unrealized Gains, Held-to-maturity securities	26		24
Unrealized Losses, Held-to-maturity securities	0		0
Held-to-maturity Securities, Fair Value	4,529		238
Obligations of U.S. states and political subdivision [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	702	[1]	755	[1]
Unrealized Gains, Available-for-sale securities	11		12
Unrealized Losses, Available-for-sale securities	(7)		(25)
Fair Value, Available-for-sale securities	706		742
Amortized Cost, Held-to-Maturity Securities	24	[1]	29	[1]
Non-Credit Loss Component of OTTI Securities, Held-to-Maturity Securities	0
Unrealized Gains, Held-to-maturity securities	1		1
Unrealized Losses, Held-to-maturity securities	0		0
Held-to-maturity Securities, Fair Value	25		30
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	1	[1]	1	[1]
Unrealized Gains, Available-for-sale securities	0		0
Unrealized Losses, Available-for-sale securities	0		0
Fair Value, Available-for-sale securities	1		1
Amortized Cost, Held-to-Maturity Securities	12	[1]	18	[1]
Non-Credit Loss Component of OTTI Securities, Held-to-Maturity Securities	0
Unrealized Gains, Held-to-maturity securities	1		1
Unrealized Losses, Held-to-maturity securities	0		0
Held-to-maturity Securities, Fair Value	13		19
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	60	[1]	125	[1]
Unrealized Gains, Available-for-sale securities	0		1
Unrealized Losses, Available-for-sale securities	0		0
Fair Value, Available-for-sale securities	60		126
Home Equity Backed Securities [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	100	[1]	263	[1]
Unrealized Gains, Available-for-sale securities	0		0
Unrealized Losses, Available-for-sale securities	(8)		(36)
Fair Value, Available-for-sale securities	92		227
Other securities [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	106	[1]	100	[1]
Unrealized Gains, Available-for-sale securities	0		0
Unrealized Losses, Available-for-sale securities	(11)		(6)
Fair Value, Available-for-sale securities	95		94
Foreign debt securities [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	4,327	[1],[4]	4,607	[1],[4]
Unrealized Gains, Available-for-sale securities	9	[4]	10	[4]
Unrealized Losses, Available-for-sale securities	(7)	[4]	(15)	[4]
Fair Value, Available-for-sale securities	4,329	[4]	4,602	[4]
Foreign debt securities [Member] | Foreign Government [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	1,040		1,101
Equity securities [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	165	[1]	165	[1]
Unrealized Gains, Available-for-sale securities	3		2
Unrealized Losses, Available-for-sale securities	(3)		(5)
Fair Value, Available-for-sale securities	165		162
Asset-backed securities and other debt securities held by a consolidated VIE [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Held-to-Maturity Securities	164	[1],[5]	304	[1],[5]
Non-Credit Loss Component of OTTI Securities, Held-to-Maturity Securities	(88)	[5]	(104)	[5]
Unrealized Gains, Held-to-maturity securities	61	[5]	19	[5]
Unrealized Losses, Held-to-maturity securities	0	[5]	0	[5]
Held-to-maturity Securities, Fair Value	137	[5]	219	[5]
US Government sponsored enterprises [Member] | Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	507		167
Amortized Cost, Held-to-Maturity Securities	2,776		398
US Government sponsored enterprises [Member] | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]
Schedule of Available-for-sale Securities and Held-to-Maturity Securities [Line Items]
Amortized Cost, Available-for-sale securities	28		33
Amortized Cost, Held-to-Maturity Securities	$ 1,626		$ 447

[1] During the third quarter of 2014, we transferred U.S. government sponsored and U.S. government agency mortgage-backed securities with a fair value of $10,985 million from available-for-sale to held-to-maturity. These securities were transferred to held-to-maturity at fair value as of the transfer date with the fair value amount becoming the amortized cost basis for the transferred securities. The difference between the par value of the securities and their fair value at the date of transfer will be amortized as an adjustment to yield over the remaining contractual life of each security. At the date of the transfer, AOCI included net pretax unrealized losses of $234 million related to the transferred securities which will be amortized over the remaining contractual life of each security as an adjustment of yield in a manner consistent with the amortization of any premium or discount. The transfers reflect our intent to hold the securities to maturity and will reduce the impact of price volatility on AOCI and regulatory capital under Basel III.

[2] Includes securities at amortized cost of $507 million and $167 million issued or guaranteed by FNMA at September 30, 2014 and December 31, 2013, respectively, and $28 million and $33 million issued or guaranteed by FHLMC at September 30, 2014 and December 31, 2013, respectively.

[3] Includes securities at amortized cost of $2,776 million and $398 million issued or guaranteed by FNMA at September 30, 2014 and December 31, 2013, respectively, and $1,626 million and $447 million issued and guaranteed by FHLMC at September 30, 2014 and December 31, 2013, respectively.

[4] At September 30, 2014 and December 31, 2013, foreign debt securities consisted of $1,040 million and $1,101 million, respectively, of securities fully backed by foreign governments. The remainder of foreign debt securities represents public sector entity, bank or corporate debt.

[5] Relates to securities held by Bryant Park Funding LLC ("Bryant Park"), a variable interest entity which was consolidated in the second quarter of 2013. See Note 16, "Variable Interest Entities" for additional information.