Fair Value Measurements - Carrying Value and Estimated Fair Value of Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value Of Other Financial Instrument [Line Items]
Commercial loans designated under fair value option and held for sale	$ 424	$ 377
Loans held for sale	1,056	3,670
Long-term debt designated under fair value option	7,700	5,000
Level 1 [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	1,385
Non-derivative trading assets	2,283
Total derivatives	14
Securities	38,004
Non-derivative trading liabilities	323
Derivatives	41
Level 2 [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	15,313
Federal funds sold and securities purchased under resale agreements	11,678
Non-derivative trading assets	23,928
Total derivatives	10,496
Securities	26,505
Commercial loans designated under fair value option and held for sale	424
Short-term financial liabilities	14,605
Deposits Without fixed maturities	107,721
Fixed maturities	4,261
Deposits in domestic offices	6,482
Non-derivative trading liabilities	6,891
Derivatives	14,871
Long-term debt	14,099
Long-term debt designated under fair value option	7,375
Level 3 [Member]
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	505
Non-derivative trading assets	3,032
Total derivatives	189
Commercial loans, net of allowance for credit losses	42,987
Consumer loans, net of allowance for credit losses	14,606
Deposits in domestic offices	2,880
Derivatives	213
Long-term debt designated under fair value option	321
Commercial Loans [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	443	965
Commercial Loans [Member] \| Level 3 [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	19
Consumer Loans [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	613	2,705
Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	548	2,058
Consumer Loans [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	65	231
Consumer Loans [Member] \| Level 3 [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	568
Consumer Loans [Member] \| Level 3 [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	65
Carrying Value
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	17,203	27,534
Federal funds sold and securities purchased under resale agreements	11,678	3,109
Non-derivative trading assets	29,243	30,028
Total derivatives	10,699	9,826
Securities	64,273	55,316
Commercial loans, net of allowance for credit losses	42,221	33,207
Commercial loans designated under fair value option and held for sale	424	378
Consumer loans, net of allowance for credit losses	18,594	17,917
Short-term financial liabilities	14,605	18,497
Deposits Without fixed maturities	107,721	123,720
Fixed maturities	4,252	6,210
Deposits in domestic offices	9,362	9,799
Non-derivative trading liabilities	7,214	7,342
Derivatives	15,125	8,440
Long-term debt	13,267	11,666
Long-term debt designated under fair value option	7,696	5,043
Carrying Value \| Commercial Loans [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	19	587
Carrying Value \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	548	2,058
Carrying Value \| Consumer Loans [Member] \| Credit Card Receivables [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale		416
Carrying Value \| Consumer Loans [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	65	231
Fair Value
Fair Value Of Other Financial Instrument [Line Items]
Short-term financial assets	17,203	27,534
Federal funds sold and securities purchased under resale agreements	11,678	3,104
Non-derivative trading assets	29,243	30,028
Total derivatives	10,699	9,826
Securities	64,509	55,579
Commercial loans, net of allowance for credit losses	42,897	33,535
Commercial loans designated under fair value option and held for sale	424	378
Consumer loans, net of allowance for credit losses	14,606	14,301
Short-term financial liabilities	14,605	18,497
Deposits Without fixed maturities	107,721	122,710
Fixed maturities	4,261	6,232
Deposits in domestic offices	9,362	9,799
Non-derivative trading liabilities	7,214	7,342
Derivatives	15,125	8,440
Long-term debt	14,099	11,653
Long-term debt designated under fair value option	7,696	5,043
Fair Value \| Commercial Loans [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	19	587
Fair Value \| Consumer Loans [Member] \| Residential Mortgage [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	568	2,071
Fair Value \| Consumer Loans [Member] \| Credit Card Receivables [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale		416
Fair Value \| Consumer Loans [Member] \| Other Consumer [Member]
Fair Value Of Other Financial Instrument [Line Items]
Loans held for sale	$ 65	$ 231

Deposits fixed maturities.

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Deposits without fixed maturities.

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

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Non-derivative trading assets fair value disclosure.

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Short-term financial assets fair value disclosure.

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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.

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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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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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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.

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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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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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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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