Fair Value Measurements - Carrying Value and Estimated Fair Value of Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair Value Of Other Financial Instrument [Line Items]
Securities purchased under resale agreements	$ 1,352	$ 2,119
Commercial loans designated under fair value option and held for sale	753	58
Loans held for sale	969	230
Deposits designated under fair value option	7,637	7,740
Long-term debt designated under fair value option	7,700	7,600
Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	864	76
Consumer Loans [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	105	154
Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	42	91
Consumer Loans [Member] \| Other consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	63	63
Level 1 [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	1,155	961
Securities purchased under resale agreements	0	0
Non-derivative trading assets	2,140	1,344
Derivatives	13	26
Securities	39,153	39,553
Commercial loans, net of allowance for credit losses	0	0
Commercial loans designated under fair value option and held for sale	0	0
Consumer loans, net of allowance for credit losses	0	0
Short-term financial liabilities	0	0
Deposits without fixed maturities	0	0
Deposits with fixed maturities	0	0
Deposits designated under fair value option	0	0
Non-derivative trading liabilities	367	308
Derivatives	5	5
Long-term debt	0	0
Long-term debt designated under fair value option	0	0
Level 1 [Member] \| Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	0	0
Level 1 [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	0	0
Level 1 [Member] \| Consumer Loans [Member] \| Other consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	0	0
Level 2 [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	23,466	19,614
Securities purchased under resale agreements	1,352	2,119
Non-derivative trading assets	18,025	18,924
Derivatives	5,391	7,467
Securities	15,868	16,852
Commercial loans, net of allowance for credit losses	0	0
Commercial loans designated under fair value option and held for sale	753	58
Consumer loans, net of allowance for credit losses	68	492
Short-term financial liabilities	28,785	19,154
Deposits without fixed maturities	95,950	102,584
Deposits with fixed maturities	1,949	2,289
Deposits designated under fair value option	5,393	5,406
Non-derivative trading liabilities	3,993	3,826
Derivatives	5,611	7,294
Long-term debt	15,805	15,729
Long-term debt designated under fair value option	6,959	6,686
Level 2 [Member] \| Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	111	18
Level 2 [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	14	36
Level 2 [Member] \| Consumer Loans [Member] \| Other consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	0	0
Level 3 [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	43	51
Securities purchased under resale agreements	0	0
Non-derivative trading assets	3,183	2,635
Derivatives	52	76
Securities	0	0
Commercial loans, net of allowance for credit losses	51,156	49,897
Commercial loans designated under fair value option and held for sale	0	0
Consumer loans, net of allowance for credit losses	16,321	15,559
Short-term financial liabilities	42	51
Deposits without fixed maturities	0	0
Deposits with fixed maturities	0	0
Deposits designated under fair value option	2,244	2,334
Non-derivative trading liabilities	0	0
Derivatives	32	49
Long-term debt	0	0
Long-term debt designated under fair value option	732	900
Level 3 [Member] \| Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	0	0
Level 3 [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	29	56
Level 3 [Member] \| Consumer Loans [Member] \| Other consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	63	63
Carrying Value [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	24,664	20,626
Securities purchased under resale agreements	1,352	2,119
Non-derivative trading assets	23,348	22,903
Derivatives	5,456	7,569
Securities	54,974	56,368
Commercial loans, net of allowance for credit losses	49,585	48,186
Commercial loans designated under fair value option and held for sale	753	58
Consumer loans, net of allowance for credit losses	18,738	18,903
Short-term financial liabilities	28,827	19,205
Deposits without fixed maturities	95,950	102,584
Deposits with fixed maturities	1,944	2,284
Deposits designated under fair value option	7,637	7,740
Non-derivative trading liabilities	4,360	4,134
Derivatives	5,648	7,348
Long-term debt	15,262	15,261
Long-term debt designated under fair value option	7,691	7,586
Carrying Value [Member] \| Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	111	18
Carrying Value [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	42	91
Carrying Value [Member] \| Consumer Loans [Member] \| Other consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	63	63
Estimate of fair value [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	24,664	20,626
Securities purchased under resale agreements	1,352	2,119
Non-derivative trading assets	23,348	22,903
Derivatives	5,456	7,569
Securities	55,021	56,405
Commercial loans, net of allowance for credit losses	51,156	49,897
Commercial loans designated under fair value option and held for sale	753	58
Consumer loans, net of allowance for credit losses	16,389	16,051
Short-term financial liabilities	28,827	19,205
Deposits without fixed maturities	95,950	102,584
Deposits with fixed maturities	1,949	2,289
Deposits designated under fair value option	7,637	7,740
Non-derivative trading liabilities	4,360	4,134
Derivatives	5,648	7,348
Long-term debt	15,805	15,729
Long-term debt designated under fair value option	7,691	7,586
Estimate of fair value [Member] \| Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	111	18
Estimate of fair value [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	43	92
Estimate of fair value [Member] \| Consumer Loans [Member] \| Other consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	$ 63	$ 63

Deposits fixed maturities.

No definition available.

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- Definition

Deposits without fixed maturities.

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No definition available.

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- Definition

This element represents the portion of long term debt that the entity has elected to value at fair value under the fair value option.

+ References

No definition available.

+ Details

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- Definition

Non-derivative trading assets fair value disclosure.

+ References

No definition available.

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- Definition

Non derivative trading liability.

+ References

No definition available.

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- Definition

Short-term financial assets fair value disclosure.

+ References

No definition available.

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- Definition

Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

+ References

No definition available.

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- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

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- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

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Period Type:	instant

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- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of commercial loans and leases receivable including, but not limited to, commercial and industrial loans, agricultural loans, mortgage loans, promissory notes, interbank and other loans to financial institutions, draws against credit facilities, trade financing, lease financings. Excludes loans and leases covered under loss sharing agreements.

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- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of consumer loans, including, but not limited to, mortgage, home equity, vehicles, credit card, installment, and lease financing. Excludes loans and leases covered under loss sharing agreements.

+ References

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- Definition

Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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- Definition

Amount of loans held for sale, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

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- Definition

Fair value portion of securities borrowed from other entities.

+ References

No definition available.

+ Details

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- Definition

Amount, after the effects of master netting arrangements, of funds outstanding loaned in the form of a security resale agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes purchases of participations in pools of securities that are subject to a resale agreement and assets not subject to a master netting arrangement.

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of short-term debt existing as of the balance sheet date.

+ References

No definition available.

+ Details

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