Carrying Amounts and Fair Values of the Company's Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Financial assets
Trading assets	$ 6,202	[1]	$ 5,040	[1]
Available-for-sale Securities	26,770	[2]	22,542	[2]
Loans Held-for-sale, Fair Value Disclosure	1,892		1,378
Financial liabilities
Long-term Debt, Fair Value	1,283		1,556
Trading liabilities	1,227		1,181
Estimate of Fair Value, Fair Value Disclosure [Member]
Financial assets
Cash and cash equivalents	8,229	[3]	5,263	[3]
Trading assets	6,202	[4]	5,040	[4]
Available-for-sale Securities	26,770	[4]	22,542	[4]
Loans Held-for-sale, Fair Value Disclosure	3,240	[5]	1,700	[5]
Loans Net Fair Value Disclosure	126,855	[6]	121,341	[6]
Financial liabilities
Consumer and commercial deposits	140,562	[7]	129,801	[7]
Short-term borrowings	9,186	[8]	8,739	[8]
Long-term Debt, Fair Value	13,056	[8]	10,678	[8]
Trading liabilities	1,227	[4]	1,181	[4]
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets
Cash and cash equivalents	8,229	[3]	5,263	[3]
Trading assets	1,000	[4]	1,156	[4]
Available-for-sale Securities	2,059	[4]	1,396	[4]
Loans Held-for-sale, Fair Value Disclosure	0		0
Loans Net Fair Value Disclosure	0		0
Financial liabilities
Consumer and commercial deposits	0		0
Short-term borrowings	0		0
Long-term Debt, Fair Value	0		0
Trading liabilities	929	[4]	979	[4]
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Financial assets
Cash and cash equivalents	0		0
Trading assets	5,177	[4]	3,812	[4]
Available-for-sale Securities	23,765	[4]	20,193	[4]
Loans Held-for-sale, Fair Value Disclosure	2,063	[5]	1,666	[5]
Loans Net Fair Value Disclosure	545	[6]	2,860	[6]
Financial liabilities
Consumer and commercial deposits	140,562	[7]	129,801	[7]
Short-term borrowings	9,186	[8]	8,739	[8]
Long-term Debt, Fair Value	12,398	[8]	10,086	[8]
Trading liabilities	293	[4]	198	[4]
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 3 [Member]
Financial assets
Cash and cash equivalents	0		0
Trading assets	25	[4]	72	[4]
Available-for-sale Securities	946	[4]	953	[4]
Loans Held-for-sale, Fair Value Disclosure	1,177	[5]	34	[5]
Loans Net Fair Value Disclosure	126,310	[6]	118,481	[6]
Financial liabilities
Consumer and commercial deposits	0		0
Short-term borrowings	0		0
Long-term Debt, Fair Value	658	[8]	592	[8]
Trading liabilities	5		4
Carrying (Reported) Amount, Fair Value Disclosure
Financial assets
Cash and cash equivalents	8,229		5,263
Trading assets	6,202		5,040
Available-for-sale Securities	26,770		22,542
Loans Held-for-sale, Fair Value Disclosure	3,232		1,699
Loans Net Fair Value Disclosure	131,175		125,833
Financial liabilities
Consumer and commercial deposits	140,567		129,759
Short-term borrowings	9,186		8,739
Long-term Debt, Fair Value	13,022		10,700
Trading liabilities	$ 1,227		$ 1,181

[1] Includes loans held for sale, at fair value, of consolidated VIEs of $0 million and $261 million at December 31, 2014 and December 31, 2013, respectively.

[2] Includes loans of consolidated VIEs of $288 million and $327 million at December 31, 2014 and December 31, 2013, respectively.

[3] (a)Cash and cash equivalents are valued at their carrying amounts reported in the balance sheet, which are reasonable estimates of fair value due to the relatively short period to maturity of the instrume

[4] ecurities AFS, and trading liabilities and derivatives that are classified as level 1 are valued based on quoted market prices. For those instruments classified as level 2 or 3, refer to the respective valuation discussions within this footn

[5] LHFS are generally valued based on observable current market prices or, if quoted market prices are not available, on quoted market prices of similar instruments. Refer to the LHFS section within this footnote for further discussion of the LHFS carried at fair value. In instances for which significant valuation assumptions are not readily observable in the market, instruments are valued based on the best available data to approximate fair value. This data may be internally-developed and considers risk premiums that a market participant would require under then-current market conditio

[6] LHFI fair values are based on a hypothetical exit price, which does not represent the estimated intrinsic value of the loan if held for investment. The assumptions used are expected to approximate those that a market participant purchasing the loans would use to value the loans, including a market risk premium and liquidity discount. Estimating the fair value of the loan portfolio when loan sales and trading markets are illiquid, or for certain loan types, nonexistent, requires significant judgment. Therefore, the estimated fair value can vary significantly depending on a market participant’s ultimate considerations and assumptions. The final value yields a market participant’s expected return on investment that is indicative of the current market conditions, but it does not take into consideration the Company’s estimated value from continuing to hold these loans or its lack of willingness to transact at these estimated values.The Company generally estimated fair value for LHFI based on estimated future cash flows discounted, initially, at current origination rates for loans with similar terms and credit quality, which derived an estimated value of 100% and 99% on the loan portfolio’s net carrying value at December 31, 2014 and 2013, respectively. The value derived from origination rates likely does not represent an exit price; therefore, an incremental market risk and liquidity discount was subtracted from the initial value at December 31, 2014 and 2013. The discounted value is a function of a market participant’s required yield in the current environment and is not a reflection of the expected cumulative losses on the loans. Loan prepayments are used to adjust future cash flows based on historical experience and prepayment model forecasts. The value of related accrued interest on loans approximates fair value; however, it is not included in the carrying amount or fair value of loans. The value of long-term customer relationships is not permitted under current U.S. GAAP to be included in the estimated fair va

[7] (e)Deposit liabilities with no defined maturity such as DDAs, NOW/money market accounts, and savings accounts have a fair value equal to the amount payable on demand at the reporting date (i.e., their carrying amounts). Fair values for CDs are estimated using a discounted cash flow measurement that applies current interest rates to a schedule of aggregated expected maturities. The assumptions used in the discounted cash flow analysis are expected to approximate those that market participants would use in valuing deposits. The value of long-term relationships with depositors is not taken into account in estimating fair values. For valuation of brokered time deposits that the Company measures at fair value as well as those that are carried at amortized cost, refer to the respective valuation section within this footno

[8] (f)Fair values for short-term borrowings and certain long-term debt are based on quoted market prices for similar instruments or estimated using discounted cash flow analysis and the Company’s current incremental borrowing rates for similar types of instruments. For long-term debt that the Company measures at fair value, refer to the respective valuation section within this footnote. For level 3 debt, the terms are unique in nature or there are otherwise no similar instruments that can be used to value the instrument without using significant unobservable assumptions. In this situation, the Company reviews current borrowing rates along with the collateral levels that secure the debt in determining an appropriate fair value adjustme