Fair Value Measurements - Carrying Value and Estimated Fair Value of Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value Of Other Financial Instrument [Line Items]
Securities purchased under resale agreements	$ 2,216	$ 3,149
Commercial loans designated under fair value option and held for sale	1	465
Loans held for sale	236	1,018
Long-term debt designated under fair value option	6,800	7,300
Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	42	481
Consumer Loans [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	194	537
Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	130	472
Consumer Loans [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	64	65
Level 1 [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	1,512	1,359
Securities purchased under resale agreements	0	0
Non-derivative trading assets	2,277	2,484
Derivatives	14	30
Securities	28,010	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 designated under fair value option	0	0
Non-derivative trading liabilities	457	207
Derivatives	15	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]
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	29,917	13,279
Securities purchased under resale agreements	2,216	3,149
Non-derivative trading assets	16,593	20,061
Derivatives	5,962	6,664
Securities	21,641	26,126
Commercial loans, net of allowance for credit losses	0	0
Commercial loans designated under fair value option and held for sale	1	465
Consumer loans, net of allowance for credit losses	0	0
Short-term financial liabilities	19,518	14,952
Without fixed maturities	102,950	104,414
Fixed maturities	2,125	4,574
Deposits designated under fair value option	5,182	6,056
Non-derivative trading liabilities	4,013	5,767
Derivatives	7,304	9,933
Long-term debt	15,718	15,163
Long-term debt designated under fair value option	6,286	6,851
Level 2 [Member] \| Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	41	16
Level 2 [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	0	0
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	66	81
Securities purchased under resale agreements	0	0
Non-derivative trading assets	2,071	2,946
Derivatives	69	171
Securities	0	0
Commercial loans, net of allowance for credit losses	49,619	45,153
Commercial loans designated under fair value option and held for sale	0	0
Consumer loans, net of allowance for credit losses	15,848	15,173
Short-term financial liabilities	66	81
Without fixed maturities	0	0
Fixed maturities	0	0
Deposits designated under fair value option	2,669	2,636
Non-derivative trading liabilities	0	0
Derivatives	58	127
Long-term debt	0	0
Long-term debt designated under fair value option	561	429
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	126	485
Level 3 [Member] \| Consumer Loans [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	64	65
Carrying Value
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	31,495	14,719
Securities purchased under resale agreements	2,216	3,149
Non-derivative trading assets	20,941	25,491
Derivatives	6,045	6,865
Securities	49,598	69,336
Commercial loans, net of allowance for credit losses	48,196	43,833
Commercial loans designated under fair value option and held for sale	1	465
Consumer loans, net of allowance for credit losses	18,919	18,778
Short-term financial liabilities	19,584	15,033
Without fixed maturities	102,950	104,414
Fixed maturities	2,119	4,565
Deposits designated under fair value option	7,851	8,692
Non-derivative trading liabilities	4,470	5,974
Derivatives	7,377	10,081
Long-term debt	15,304	14,465
Long-term debt designated under fair value option	6,847	7,280
Carrying Value \| Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	41	16
Carrying Value \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	130	472
Carrying Value \| Consumer Loans [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	64	65
Estimate of fair value [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	31,495	14,719
Securities purchased under resale agreements	2,216	3,149
Non-derivative trading assets	20,941	25,491
Derivatives	6,045	6,865
Securities	49,651	69,547
Commercial loans, net of allowance for credit losses	49,619	45,153
Commercial loans designated under fair value option and held for sale	1	465
Consumer loans, net of allowance for credit losses	15,848	15,173
Short-term financial liabilities	19,584	15,033
Without fixed maturities	102,950	104,414
Fixed maturities	2,125	4,574
Deposits designated under fair value option	7,851	8,692
Non-derivative trading liabilities	4,470	5,974
Derivatives	7,377	10,081
Long-term debt	15,718	15,163
Long-term debt designated under fair value option	6,847	7,280
Estimate of fair value [Member] \| Commercial Loan [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	41	16
Estimate of fair value [Member] \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	126	485
Estimate of fair value [Member] \| Consumer Loans [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
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.

+ 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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- 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.

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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.

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