Carrying Amounts and Fair Values of the Company's Financial Instruments (Detail) - USD ($) $ in Millions		Jun. 30, 2016	Dec. 31, 2015
Financial assets
Trading assets	[1]	$ 6,850	$ 6,119
Available-for-sale Securities		29,336	27,825
Loans Held-for-sale, Fair Value Disclosure		2,176	1,494
Financial liabilities
Long-term Debt, Fair Value		970
Fair Value, Inputs, Level 1 [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure	[2]	5,265	5,599
Trading assets	[3]	909	866
Available-for-sale Securities	[3]	4,525	3,542
Loans Held-for-sale, Fair Value Disclosure	[4]	0	0
Loans Net Fair Value Disclosure	[5]	0	0
Financial liabilities
Consumer And Commercial Deposits, Fair Value Disclosure	[6]	0	0
Short-term Debt, Fair Value	[7]	0	0
Long-term Debt, Fair Value	[7]	0	0
Trading liabilities	[3]	637	664
Fair Value, Inputs, Level 2 [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure	[2]	0	0
Trading assets	[3]	5,868	5,143
Available-for-sale Securities	[3]	24,098	23,727
Loans Held-for-sale, Fair Value Disclosure	[4]	2,400	1,803
Loans Net Fair Value Disclosure	[5]	226	397
Financial liabilities
Consumer And Commercial Deposits, Fair Value Disclosure	[6]	152,734	149,889
Short-term Debt, Fair Value	[7]	4,857	4,627
Long-term Debt, Fair Value	[7]	11,557	7,772
Trading liabilities	[3]	595	593
Fair Value, Inputs, Level 3 [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure	[2]	0	0
Trading assets	[3]	73	110
Available-for-sale Securities	[3]	713	556
Loans Held-for-sale, Fair Value Disclosure	[4]	75	39
Loans Net Fair Value Disclosure	[5]	138,454	130,781
Financial liabilities
Consumer And Commercial Deposits, Fair Value Disclosure	[6]	0	0
Short-term Debt, Fair Value	[7]	0	0
Long-term Debt, Fair Value	[7]	682	602
Trading liabilities	[3]	13	6
Reported Value Measurement [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure	[2]	5,265	5,599
Trading assets	[3]	6,850	6,119
Available-for-sale Securities	[3]	29,336	27,825
Loans Held-for-sale, Fair Value Disclosure	[4]	2,468	1,838
Loans Net Fair Value Disclosure	[5]	139,882	134,690
Financial liabilities
Consumer And Commercial Deposits, Fair Value Disclosure	[6]	152,751	149,830
Short-term Debt, Fair Value	[7]	4,857	4,627
Long-term Debt, Fair Value	[7]	12,264	8,462
Trading liabilities	[3]	1,245	1,263
Estimate of Fair Value, Fair Value Disclosure [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure	[2]	5,265	5,599
Trading assets	[3]	6,850	6,119
Available-for-sale Securities	[3]	29,336	27,825
Loans Held-for-sale, Fair Value Disclosure	[4]	2,475	1,842
Loans Net Fair Value Disclosure	[5]	138,680	131,178
Financial liabilities
Consumer And Commercial Deposits, Fair Value Disclosure	[6]	152,734	149,889
Short-term Debt, Fair Value	[7]	4,857	4,627
Long-term Debt, Fair Value	[7]	12,239	8,374
Trading liabilities	[3]	$ 1,245	$ 1,263

[1] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,282 million and $1,377 million at June 30, 2016 and December 31, 2015, respectively

[2] Cash and cash equivalents are valued at their carrying amounts, which are reasonable estimates of fair value due to the relatively short period to maturity of the instruments.

[3] Trading assets and derivative instruments, securities AFS, and trading liabilities and derivative instruments 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 footnote.

[4] LHFS are generally valued based on observable current market prices or, if quoted market prices are not available, quoted market prices of similar instruments. Refer to the LHFS section within this footnote for further discussion. When 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 conditions.

[5] 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 nonexistent requires significant judgment.Generally, the Company measures fair value for LHFI based on estimated future discounted cash flows using current origination rates for loans with similar terms and credit quality, which derived an estimated value of 102% and 101% on the loan portfolio’s net carrying value at June 30, 2016 and December 31, 2015, respectively. The value derived from origination rates likely does not represent an exit price; therefore, an incremental market risk and liquidity discount was applied when estimating the fair value of these loans. 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.

[6] 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 approach 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 footnote.

[7] Fair values for short-term borrowings and certain long-term debt are based on quoted market prices for similar instruments or estimated discounted cash flows utilizing the Company’s current incremental borrowing rate 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 no similar instruments that can be used to value the instrument without using significant unobservable assumptions. In these situations, the Company reviews current borrowing rates along with the collateral levels that secure the debt in determining an appropriate fair value adjustment.