Fair Value Measurements - Carrying Value and Estimated Fair Value of Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair Value Of Other Financial Instrument [Line Items]
Securities purchased under resale agreements	$ 6,361	$ 3,149
Commercial loans designated under fair value option and held for sale	3	465
Commercial loans held for sale	399	1,018
Long-term debt designated under fair value option	7,700	7,300
Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	58	481
Consumer Loans [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	341	537
Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	277	472
Consumer Loans [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	64	65
Level 1 [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	1,238	1,359
Securities purchased under resale agreements	0	0
Non-derivative trading assets	1,234	2,484
Derivatives	26	30
Securities	34,692	43,421
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
Without fixed maturities	0	0
Fixed maturities	0	0
Deposits in domestic offices	0	0
Non-derivative trading liabilities	841	207
Derivatives	17	21
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]
Commercial loans held for sale	0	0
Level 1 [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	0	0
Level 1 [Member] \| Consumer Loans [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	0	0
Level 2 [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	17,059	13,279
Securities purchased under resale agreements	6,361	3,149
Non-derivative trading assets	22,619	20,061
Derivatives	9,732	11,785
Securities	26,400	26,126
Commercial loans, net of allowance for credit losses	0	0
Commercial loans designated under fair value option and held for sale	3	465
Consumer loans, net of allowance for credit losses	0	0
Short-term financial liabilities	12,314	15,421
Without fixed maturities	105,074	104,414
Fixed maturities	3,604	4,574
Deposits in domestic offices	5,500	6,056
Non-derivative trading liabilities	6,186	5,767
Derivatives	13,437	15,054
Long-term debt	15,014	15,163
Long-term debt designated under fair value option	7,072	6,851
Level 2 [Member] \| Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	55	16
Level 2 [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	0	0
Level 2 [Member] \| Consumer Loans [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	0	0
Level 3 [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	462	436
Securities purchased under resale agreements	0	0
Non-derivative trading assets	2,453	2,946
Derivatives	149	171
Securities	0	0
Commercial loans, net of allowance for credit losses	45,051	45,153
Commercial loans designated under fair value option and held for sale	0	0
Consumer loans, net of allowance for credit losses	15,704	15,173
Short-term financial liabilities	0	0
Without fixed maturities	0	0
Fixed maturities	0	0
Deposits in domestic offices	2,876	2,636
Non-derivative trading liabilities	0	0
Derivatives	121	127
Long-term debt	0	0
Long-term debt designated under fair value option	618	429
Level 3 [Member] \| Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	0	0
Level 3 [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	282	485
Level 3 [Member] \| Consumer Loans [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	64	65
Carrying Value
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	18,759	15,074
Securities purchased under resale agreements	6,361	3,149
Non-derivative trading assets	26,306	25,491
Derivatives	9,907	11,986
Securities	60,892	69,336
Commercial loans, net of allowance for credit losses	43,370	43,833
Commercial loans designated under fair value option and held for sale	3	465
Consumer loans, net of allowance for credit losses	18,994	18,778
Short-term financial liabilities	12,314	15,421
Without fixed maturities	105,074	104,414
Fixed maturities	3,599	4,565
Deposits in domestic offices	8,376	8,692
Non-derivative trading liabilities	7,027	5,974
Derivatives	13,575	15,202
Long-term debt	14,349	14,465
Long-term debt designated under fair value option	7,690	7,280
Carrying Value \| Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	55	16
Carrying Value \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	277	472
Carrying Value \| Consumer Loans [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	64	65
Estimate of fair value [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	18,759	15,074
Securities purchased under resale agreements	6,361	3,149
Non-derivative trading assets	26,306	25,491
Derivatives	9,907	11,986
Securities	61,092	69,547
Commercial loans, net of allowance for credit losses	45,051	45,153
Commercial loans designated under fair value option and held for sale	3	465
Consumer loans, net of allowance for credit losses	15,704	15,173
Short-term financial liabilities	12,314	15,421
Without fixed maturities	105,074	104,414
Fixed maturities	3,604	4,574
Deposits in domestic offices	8,376	8,692
Non-derivative trading liabilities	7,027	5,974
Derivatives	13,575	15,202
Long-term debt	15,014	15,163
Long-term debt designated under fair value option	7,690	7,280
Estimate of fair value [Member] \| Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	55	16
Estimate of fair value [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	282	485
Estimate of fair value [Member] \| Consumer Loans [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans held for sale	$ 64	$ 65

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.

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- Definition

Non-derivative trading assets fair value disclosure.

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Non derivative trading liability.

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- Definition

Short-term financial assets fair value disclosure.

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No definition available.

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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. This item represents the aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits among others.

+ References

No definition available.

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- Definition

Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

+ References

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- Definition

Derivative instrument obligations meeting the definition of a liability which the Company is a party to as of the balance sheet date.

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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

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 loans held-for-sale as presented on the statement of financial position which may include mortgage loans held-for-sale, finance receivables held-for-sale, or any other loans classified as held-for-sale which are due the Company as of the balance sheet date.

+ References

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The aggregate carrying amount of loans receivable that will be sold to other entities. Includes mortgage and all other loans (collectively, loans) not classified as held for investment. Such loans are stated at the lower of cost or market, or elected fair value. Mortgage loans exclude mortgage-backed securities which are considered a debt security (other loan).

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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

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. This item represents the aggregate of securities borrowed from broker-dealers or institutions (a) to deliver them in place of securities not available because of short-sales or late or ineffective deliveries; (b) to lend them in connection with finder or conduit transactions; and (c) to be used for other purposes permitted under federal regulations.

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The carrying value of funds outstanding loaned in the form of security resale agreements if the agreement requires the purchaser to resell the identical security purchased or a security that meets the definition of "substantially the same." Also includes purchases of participations in pools of securities that are subject to a resale agreement.

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- Definition

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