Comerica (CMA) 10-K 26 Feb 16 2015 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 19, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Amendment Flag	false
Entity Registrant Name	Comerica INC /NEW/
Entity Central Index Key	28,412
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		174,878,064
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 9,000,000,000

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
ASSETS
Cash and due from banks		$ 1,157	$ 1,026
Interest-bearing deposits with banks		4,990	5,045
Other short-term investments		113	99
Investment securities available-for-sale	[1]	10,519	8,116
Investment securities held-to-maturity		1,981	1,935
Commercial loans		31,659	31,520
Real estate construction loans		2,001	1,955
Commercial mortgage loans		8,977	8,604
Lease financing		724	805
International loans		1,368	1,496
Residential mortgage loans		1,870	1,831
Consumer loans		2,485	2,382
Total loans		49,084	48,593
Less allowance for loan losses		(634)	(594)
Net loans		48,450	47,999
Premises and equipment		550	532
Accrued income and other assets		4,117	4,434
Total assets		71,877	69,186
LIABILITIES AND SHAREHOLDERS' EQUITY
Noninterest-bearing deposits		30,839	27,224
Money market and interest-bearing checking deposits		23,532	23,954
Savings deposits		1,898	1,752
Customer certificates of deposit		3,552	4,421
Foreign office time deposits		32	135
Total interest-bearing deposits		29,014	30,262
Total deposits		59,853	57,486
Short-term borrowings		23	116
Accrued expenses and other liabilities		1,383	1,507
Medium- and long-term debt		3,058	2,675
Total liabilities		64,317	61,784
Common stock - $5 par value: Authorized - 325,000,000 shares; Issued - 228,164,824 shares		1,141	1,141
Capital surplus		2,173	2,188
Accumulated other comprehensive loss		(429)	(412)
Retained earnings		7,084	6,744
Less cost of common stock in treasury - 52,457,113 shares at 12/31/15 and 49,146,225 shares at 12/31/14		(2,409)	(2,259)
Total shareholders' equity		7,560	7,402
Total liabilities and shareholders' equity		$ 71,877	$ 69,186
[1]	Included auction-rate securities at amortized cost and fair value of $76 million and $77 million, respectively, as of December 31, 2015 and $137 million and $136 million, respectively, as of December 31, 2014.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Common stock, par value	$ 5	$ 5
Common stock, authorized shares	325,000,000	325,000,000
Common stock, issued shares	228,164,824	228,164,824
Shares in treasury	52,457,113	49,146,225

Consolidated Statements Of Inco

Consolidated Statements Of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
INTEREST INCOME
Interest and fees on loans	$ 1,551	$ 1,525	$ 1,556
Interest on investment securities	216	211	214
Interest on short-term investments	17	14	14
Total interest income	1,784	1,750	1,784
INTEREST EXPENSE
Interest on deposits	43	45	55
Interest on medium- and long-term debt	52	50	57
Total interest expense	95	95	112
Net interest income	1,689	1,655	1,672
Provision for credit losses	147	27	46
Net interest income after provision for credit losses	1,542	1,628	1,626
NONINTEREST INCOME
Card fees	290	92	86
Service charges on deposit accounts	223	215	214
Fiduciary income	187	180	171
Commercial lending fees	99	98	99
Letter of credit fees	53	57	64
Bank-owned life insurance	40	39	40
Foreign exchange income	40	40	36
Brokerage fees	17	17	17
Net securities losses	(2)	0	(1)
Other noninterest income	103	130	156
Total noninterest income	1,050	868	882
NONINTEREST EXPENSES
Salaries and benefits expense	1,009	980	1,009
Outside processing fee expense	332	122	119
Net occupancy expense	159	171	160
Equipment expense	53	57	60
Software expense	99	95	90
FDIC insurance expense	37	33	33
Advertising expense	24	23	21
Litigation-related expense	(32)	4	52
Gain on debt redemption	0	(32)	(1)
Other noninterest expenses	161	173	179
Total noninterest expenses	1,842	1,626	1,722
Income before income taxes	750	870	786
Provision for income taxes	229	277	245
Net Income	521	593	541
Less income allocated to participating securities	6	7	8
Net income attributable to common shares	$ 515	$ 586	$ 533
Basic earnings per common share	$ 2.93	$ 3.28	$ 2.92
Diluted earnings per common share	$ 2.84	$ 3.16	$ 2.85
Cash dividends declared on common stock	$ 148	$ 143	$ 126
Cash dividends declared per common share	$ 0.83	$ 0.79	$ 0.68

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 521	$ 593	$ 541
Net unrealized holding (losses) gains arising during the period	(55)	166	(343)
Less reclassification adjustment for net securities (losses) gains included in net income	(2)	1	1
Less net losses realized as a yield adjustment in interest on investment securities	(8)	0	0
Change in net unrealized (losses) gains before income taxes	(45)	165	(344)
Actuarial (loss) gain arising during the period	(57)	(240)	286
Prior service credit arising during the period	3	0	0
Amortization of actuarial net loss	70	39	89
Amortization of prior service cost	1	3	2
Change in defined benefit pension and other postretirement plans adjustment before income taxes	17	(198)	377
Total other comprehensive (loss) income before income taxes	(28)	(33)	33
(Benefit) provision for income taxes	(11)	(12)	11
Total other comprehensive (loss) income, net of tax	(17)	(21)	22
Comprehensive Income	$ 504	$ 572	$ 563

Consolidated Statements Of Chan

Consolidated Statements Of Changes In Shareholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Capital Surplus	Accumulated Other Comprehensive Loss	Retained Earnings	Treasury Stock
BALANCE at Dec. 31, 2012	$ 6,939	$ 1,141	$ 2,162	$ (413)	$ 5,928	$ (1,879)
BALANCE (in shares) at Dec. 31, 2012		188.3
Net income	541				541
Other comprehensive income (loss), net of tax	22			22
Cash dividends declared on common stock	(126)				(126)
Purchase of common stock	(291)					(291)
Purchase of common stock (in shares)		(7.5)
Net issuance of common stock under employee stock plans	30		(17)		(25)	72
Net issuance of common stock under employee stock plans (in shares)		1.5
Share-based compensation	35		35
Other	0		(1)			1
BALANCE at Dec. 31, 2013	7,150	$ 1,141	2,179	(391)	6,318	(2,097)
BALANCE (in shares) at Dec. 31, 2013		182.3
Net income	593				593
Other comprehensive income (loss), net of tax	(21)			(21)
Cash dividends declared on common stock	(143)				(143)
Purchase of common stock	(260)					(260)
Purchase of common stock (in shares)		(5.4)
Net issuance of common stock under employee stock plans	45		(27)		(24)	96
Net issuance of common stock under employee stock plans (in shares)		2.1
Share-based compensation	38		38
Other	0		2			(2)
BALANCE at Dec. 31, 2014	7,402	$ 1,141	2,188	(412)	6,744	(2,259)
BALANCE (in shares) at Dec. 31, 2014		179
Net income	521				521
Other comprehensive income (loss), net of tax	(17)			(17)
Cash dividends declared on common stock	(148)				(148)
Purchase of common stock	(240)					(240)
Purchase of common stock (in shares)		(5.3)
Purchase and retirement of warrants	(10)		(10)
Net issuance of common stock under employee stock plans	14		(22)		(11)	47
Net issuance of common stock under employee stock plans (in shares)		1
Net issuance of common stock for warrants	0		(21)		(22)	43
Net issuance of common stock for warrants (in shares)		1
Share-based compensation	38		38
BALANCE at Dec. 31, 2015	$ 7,560	$ 1,141	$ 2,173	$ (429)	$ 7,084	$ (2,409)
BALANCE (in shares) at Dec. 31, 2015		175.7

Consolidated Statements Of Cha7

Consolidated Statements Of Changes In Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Stockholders' Equity [Abstract]
Cash dividends declared on common stock, per share	$ 0.83	$ 0.79	$ 0.68

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
OPERATING ACTIVITIES
Net income	$ 521	$ 593	$ 541
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	147	27	46
(Benefit) provision for deferred income taxes	(71)	130	(20)
Depreciation and amortization	118	123	122
Net periodic defined benefit cost	48	40	88
Share-based compensation expense	38	38	35
Net amortization of securities	13	13	23
Accretion of loan purchase discount	(7)	(34)	(49)
Net securities losses	(2)	0	(1)
Net (gain) loss/writedown on foreclosed property	(2)	(4)	4
Gain on debt redemption	0	(32)	(1)
Excess tax benefits from share-based compensation arrangements	(3)	(7)	(3)
Net change in trading securities	0	13	6
Net change in accrued income receivable	(12)	(4)	7
Net change in accrued expenses payable	(35)	(14)	38
Other, net	105	(243)	(2)
Net cash provided by operating activities	862	639	836
INVESTING ACTIVITIES
Maturities and redemptions of investment securities available-for-sale	1,703	1,781	2,849
Sales of investment securities available-for-sale	54	0	0
Purchases of investment securities available-for-sale	(4,228)	(2,372)	(2,225)
Maturities and redemptions of investment securities held-to-maturity	324	0	0
Purchases of investment securities held-to-maturity	(362)	0	0
Net change in loans	(644)	(3,144)	549
Sales of Federal Home Loan Bank stock	0	41	41
Proceeds from sales of foreclosed property	12	20	55
Net increase in premises and equipment	(119)	(70)	(102)
Other, net	5	1	7
Net cash (used in) provided by investing activities	(3,255)	(3,743)	1,174
FINANCING ACTIVITIES
Net change in deposits	2,529	4,013	1,229
Net change in short-term borrowings	(93)	(137)	143
Maturities and redemptions of medium- and long-term debt	(606)	(1,406)	(1,080)
Issuances of medium- and long-term debt	1,016	596	0
Repurchases of common stock	(240)	(260)	(291)
Cash dividends paid on common stock	(147)	(137)	(123)
Issuances of common stock under employee stock plans	22	49	33
Purchase and retirement of warrants	(10)	0	0
Excess tax benefits from share-based compensation arrangements	3	7	3
Other, net	(5)	(1)	(7)
Net cash provided by (used in) financing activities	2,469	2,724	(93)
Net increase (decrease) in cash and cash equivalents	76	(380)	1,917
Cash and cash equivalents at beginning of period	6,071	6,451	4,534
Cash and cash equivalents at end of period	6,147	6,071	6,451
Interest paid	94	101	114
Income taxes paid	88	218	115
Noncash investing and financing activities:
Loans transferred to other real estate	12	16	14
Loans transferred from portfolio to held-for-sale	28	0	0
Lease residual transferred to other assets	16	0	0
Securities transferred from available-for-sale to held-to-maturity	$ 0	$ 1,958	$ 0

Basis of Presentation and Accou

Basis of Presentation and Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation and Accounting Policies	BASIS OF PRESENTATION AND ACCOUNTING POLICIES Organization Comerica Incorporated (the Corporation) is a registered financial holding company headquartered in Dallas, Texas. The Corporation’s major business segments are the Business Bank, the Retail Bank and Wealth Management. The Corporation operates in three primary geographic markets: Michigan, California and Texas. For further discussion of each business segment and primary geographic market, refer to Note 22 . The Corporation and its banking subsidiaries are regulated at both the state and federal levels. The accounting and reporting policies of the Corporation conform to United States (U.S.) generally accepted accounting principles (GAAP). The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect reported amounts and disclosures. Actual results could differ from these estimates. Certain items in prior periods were reclassified to conform to the current presentation. The following summarizes the significant accounting policies of the Corporation applied in the preparation of the accompanying consolidated financial statements. Principles of Consolidation The consolidated financial statements include the accounts of the Corporation and the accounts of those subsidiaries that are majority owned and in which the Corporation has a controlling financial interest. The Corporation consolidates entities not determined to be variable interest entities (VIEs) when it holds a controlling financial interest in the entity's outstanding voting stock and uses the cost or equity method when it holds less than a controlling financial interest. In consolidation, all significant intercompany accounts and transactions are eliminated. The results of operations of companies acquired are included from the date of acquisition. Certain amounts in the financial statements for prior years have been reclassified to conform to current financial statement presentation. The Corporation holds investments in certain legal entities that are considered VIEs. In general, a VIE is an entity that either (1) has an insufficient amount of equity to carry out its principal activities without additional subordinated financial support, (2) has a group of equity owners that are unable to make significant decisions about its activities, or (3) has a group of equity owners that do not have the obligation to absorb losses or the right to receive returns generated by its operations. If any of these characteristics are present, the entity is subject to a variable interests consolidation model, and consolidation is based on variable interests, not on ownership of the entity’s outstanding voting stock. Variable interests are defined as contractual ownership or other money interests in an entity that change with fluctuations in the entity’s net asset value. The primary beneficiary is required to consolidate the VIE. The primary beneficiary is defined as the party that has both the power to direct the activities of the VIE that most significantly impact the entity’s economic performance and the obligation to absorb losses or the right to receive benefits that could be significant to the VIE. The maximum potential exposure to losses relative to investments in VIEs is generally limited to the sum of the outstanding book basis and unfunded commitments for future investments. The Corporation evaluates its investments in VIEs, both at inception and when there is a change in circumstances that requires reconsideration, to determine if the Corporation is the primary beneficiary and consolidation is required. The Corporation accounts for unconsolidated VIEs using either the proportional, cost or equity method. These investments comprise investments in community development projects which generate tax credits to their investors and are included in "accrued income and other assets" on the consolidated balance sheets. The proportional method is used for investments in affordable housing projects that qualify for the low-income housing tax credit (LIHTC). The equity method is used for other investments where the Corporation has the ability to exercise significant influence over the entity’s operation and financial policies, which is generally presumed to exist if the Corporation owns more than a 20 percent voting interest in the entity. Other unconsolidated equity investments that do not meet the criteria to be accounted for under the equity method are accounted for under the cost method. Amortization and other write-downs of LIHTC investments are presented on a net basis as a component of the "provision for income taxes," while income, amortization and write-downs from cost and equity method investments are recorded in “other noninterest income” on the consolidated statements of income. Assets held in an agency or fiduciary capacity are not assets of the Corporation and are not included in the consolidated financial statements. See Note 9 for additional information about the Corporation’s involvement with VIEs. Fair Value Measurements The Corporation utilizes fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures. The determination of fair values of financial instruments often requires the use of estimates. In cases where quoted market values in an active market are not available, the Corporation uses present value techniques and other valuation methods to estimate the fair values of its financial instruments. These valuation methods require considerable judgment and the resulting estimates of fair value can be significantly affected by the assumptions made and methods used. Fair value is an estimate of the exchange price that would be received to sell an asset or paid to transfer a liability in an orderly transaction (i.e., not a forced transaction, such as a liquidation or distressed sale) between market participants at the measurement date. Fair value is based on the assumptions market participants would use when pricing an asset or liability. Trading securities, investment securities available-for-sale, derivatives and deferred compensation plan liabilities are recorded at fair value on a recurring basis. Additionally, from time to time, the Corporation may be required to record other assets and liabilities at fair value on a nonrecurring basis, such as impaired loans, other real estate (primarily foreclosed property), nonmarketable equity securities and certain other assets and liabilities. These nonrecurring fair value adjustments typically involve write-downs of individual assets or application of lower of cost or fair value accounting. Fair value measurements and disclosures guidance establishes a three-level fair value hierarchy based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. The fair value hierarchy gives the highest priority to quoted prices in active markets and the lowest priority to unobservable data. Fair value measurements are separately disclosed by level within the fair value hierarchy. For assets and liabilities recorded at fair value, it is the Corporation’s policy to maximize the use of observable inputs and minimize the use of unobservable inputs when developing fair value measurements. Level 1 Valuation is based upon quoted prices for identical instruments traded in active markets. Level 2 Valuation is based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-based valuation techniques for which all significant assumptions are observable in the market. Level 3 Valuation is generated from model-based techniques that use at least one significant assumption not observable in the market. These unobservable assumptions reflect estimates of assumptions that market participants would use in pricing the asset or liability. Valuation techniques include use of option pricing models, discounted cash flow models and similar techniques. The Corporation generally utilizes third-party pricing services to value Level 1 and Level 2 trading and investment securities, as well as certain derivatives designated as fair value hedges. Management reviews the methodologies and assumptions used by the third-party pricing services and evaluates the values provided, principally by comparison with other available market quotes for similar instruments and/or analysis based on internal models using available third-party market data. The Corporation may occasionally adjust certain values provided by the third-party pricing service when management believes, as the result of its review, that the adjusted price most appropriately reflects the fair value of the particular security. Fair value measurements for assets and liabilities where limited or no observable market data exists are based primarily upon estimates, often calculated based on the economic and competitive environment, the characteristics of the asset or liability and other factors. Therefore, the results cannot be determined with precision and may not be realized in an actual sale or immediate settlement of the asset or liability. Additionally, there may be inherent weaknesses in any calculation technique, and changes in the underlying assumptions used, including discount rates and estimates of future cash flows, could significantly affect the results of current or future values. Following are descriptions of the valuation methodologies and key inputs used to measure financial assets and liabilities recorded at fair value, as well as a description of the methods and significant assumptions used to estimate fair value disclosures for financial instruments not recorded at fair value in their entirety on a recurring basis. The descriptions include an indication of the level of the fair value hierarchy in which the assets or liabilities are classified. Transfers of assets or liabilities between levels of the fair value hierarchy are recognized at the beginning of the reporting period, when applicable. Cash and due from banks, federal funds sold and interest-bearing deposits with banks Due to their short-term nature, the carrying amount of these instruments approximates the estimated fair value. As such, the Corporation classifies the estimated fair value of these instruments as Level 1. Trading securities and associated deferred compensation plan liabilities Trading securities include securities held for trading purposes as well as assets held related to employee deferred compensation plans. Trading securities and associated deferred compensation plan liabilities are recorded at fair value on a recurring basis and included in “other short-term investments” and “accrued expenses and other liabilities,” respectively, on the consolidated balance sheets. Level 1 trading securities include assets related to employee deferred compensation plans, which are invested in mutual funds, U.S. Treasury securities that are traded by dealers or brokers in active over-the-counter markets and other securities traded on an active exchange, such as the New York Stock Exchange. Deferred compensation plan liabilities represent the fair value of the obligation to the employee, which corresponds to the fair value of the invested assets. Level 2 trading securities include municipal bonds and residential mortgage-backed securities issued by U.S. government-sponsored entities and corporate debt securities. The methods used to value trading securities are the same as the methods used to value investment securities, discussed below. Investment securities Investment securities available-for-sale are recorded at fair value on a recurring basis. The Corporation discloses estimated fair values of investment securities held-to-maturity, which is determined in the same manner as investment securities available-for-sale. Level 1 securities include those traded on an active exchange, such as the New York Stock Exchange, U.S. Treasury securities that are traded by dealers or brokers in active over-the-counter markets and money market funds. Level 2 securities include residential mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored entities and corporate debt securities. The fair value of Level 2 securities is determined using quoted prices of securities with similar characteristics, or pricing models based on observable market data inputs, primarily interest rates, spreads and prepayment information. Securities classified as Level 3 represent securities in less liquid markets requiring significant management assumptions when determining fair value. Auction-rate securities comprise Level 3 investment securities available-for-sale. The Corporate Development Department, with appropriate oversight and approval provided by senior management, is responsible for determining the valuation methodology for auction-rate securities and for updating significant inputs. Valuation results, including an analysis of changes to the valuation methodology and significant inputs, are provided to senior management for review on a quarterly basis. Loans held-for-sale Loans held-for-sale, included in “other short-term investments” on the consolidated balance sheets, are recorded at the lower of cost or fair value. Loans held-for-sale may be carried at fair value on a nonrecurring basis when fair value is less than cost. The fair value is based on what secondary markets are currently offering for portfolios with similar characteristics. As such, the Corporation classifies both loans held-for-sale subjected to nonrecurring fair value adjustments and the estimated fair value of loans held-for sale as Level 2. Loans The Corporation does not record loans at fair value on a recurring basis. However, the Corporation may establish a specific allowance for an impaired loan based on the fair value of the underlying collateral. Such loan values are reported as nonrecurring fair value measurements. Collateral values supporting individually evaluated impaired loans are evaluated quarterly. When management determines that the fair value of the collateral requires additional adjustments, either as a result of non-current appraisal value or when there is no observable market price, the Corporation classifies the impaired loan as Level 3. The Special Assets Group is responsible for performing quarterly credit quality reviews for all impaired loans as part of the quarterly allowance for loan losses process overseen by the Chief Credit Officer, during which valuation adjustments to updated collateral values are determined. The Corporation discloses fair value estimates for loans. The estimated fair value is determined based on characteristics such as loan category, repricing features and remaining maturity, and includes prepayment and credit loss estimates. For variable rate business loans that reprice frequently, the estimated fair value is based on carrying values adjusted for estimated credit losses inherent in the portfolio at the balance sheet date. For other business loans and retail loans, fair values are estimated using a discounted cash flow model that employs a discount rate that reflects the Corporation's current pricing for loans with similar characteristics and remaining maturity, adjusted by an amount for estimated credit losses inherent in the portfolio at the balance sheet date. The rates take into account the expected yield curve, as well as an adjustment for prepayment risk, when applicable. The Corporation classifies the estimated fair value of loans held for investment as Level 3. Customers’ liability on acceptances outstanding and acceptances outstanding Customers' liability on acceptances outstanding is included in "accrued income and other assets" and acceptances outstanding are included in "accrued expenses and other liabilities" on the consolidated balance sheets. Due to their short-term nature, the carrying amount of these instruments approximates the estimated fair value. As such, the Corporation classifies the estimated fair value of these instruments as Level 1. Derivative assets and derivative liabilities Derivative instruments held or issued for risk management or customer-initiated activities are traded in over-the-counter markets where quoted market prices are not readily available. Fair value for over-the-counter derivative instruments is measured on a recurring basis using internally developed models that use primarily market observable inputs, such as yield curves and option volatilities. The Corporation manages credit risk on its derivative positions based on whether the derivatives are being settled through a clearinghouse or bilaterally with each counterparty. For derivative positions settled on a counterparty-by-counterparty basis, the Corporation calculates credit valuation adjustments, included in the fair value of these instruments, on the basis of its relationships at the counterparty portfolio/master netting agreement level. These credit valuation adjustments are determined by applying a credit spread for the counterparty or the Corporation, as appropriate, to the total expected exposure of the derivative after considering collateral and other master netting arrangements. These adjustments, which are considered Level 3 inputs, are based on estimates of current credit spreads to evaluate the likelihood of default. When credit valuation adjustments are significant to the overall fair value of a derivative, the Corporation classifies the over-the-counter derivative valuation in Level 3 of the fair value hierarchy; otherwise, over-the-counter derivative valuations are classified in Level 2. Warrants which contain a net exercise provision or a non-contingent put right embedded in the warrant agreement are accounted for as derivatives and recorded at fair value on a recurring basis using a Black-Scholes valuation model. The Black-Scholes valuation model utilizes five inputs: risk-free rate, expected life, volatility, exercise price, and the per share market value of the underlying company. The Corporation holds a portfolio of warrants for generally nonmarketable equity securities with a fair value of $2 million at December 31, 2015 , included in "accrued income and other assets" on the consolidated balance sheets. These warrants are primarily from non-public technology companies obtained as part of the loan origination process. The Corporate Development Department is responsible for the warrant valuation process, which includes reviewing all significant inputs for reasonableness, and for providing valuation results to senior management. Increases in any of these inputs in isolation, with the exception of exercise price, would result in a higher fair value. Increases in exercise price in isolation would result in a lower fair value. The Corporation classifies warrants accounted for as derivatives as Level 3. Nonmarketable equity securities The Corporation has a portfolio of indirect (through funds) private equity and venture capital investments with a carrying value and unfunded commitments of $10 million and $4 million , respectively, at December 31, 2015 . These funds generally cannot be redeemed and the majority is not readily marketable. Distributions from these funds are received by the Corporation as a result of the liquidation of underlying investments of the funds and/or as income distributions. It is estimated that the underlying assets of the funds will be liquidated over a period of up to 12 years. Recently issued federal regulations may require the Corporation to sell certain of these funds prior to liquidation. The investments are accounted for either on the cost or equity method and are individually reviewed for impairment on a quarterly basis by comparing the carrying value to the estimated fair value. These investments may be carried at fair value on a nonrecurring basis when they are deemed to be impaired and written down to fair value. Where there is not a readily determinable fair value, the Corporation estimates fair value for indirect private equity and venture capital investments based on the net asset value, as reported by the fund, after indication that the fund adheres to applicable fair value measurement guidance. On a quarterly basis, the Corporate Development Department is responsible, with appropriate oversight and approval provided by senior management, for performing the valuation procedures and updating significant inputs, as are primarily provided by the underlying fund's management. The Corporation classifies fair value measurements of nonmarketable equity securities as Level 3. The Corporation also holds restricted equity investments, primarily Federal Home Loan Bank (FHLB) and Federal Reserve Bank (FRB) stock. Restricted equity securities are not readily marketable and are recorded at cost (par value) in "accrued income and other assets" on the consolidated balance sheets and evaluated for impairment based on the ultimate recoverability of the par value. No significant observable market data for these instruments is available. The Corporation considers the profitability and asset quality of the issuer, dividend payment history and recent redemption experience and believes its investments in FHLB and FRB stock are ultimately recoverable at par. Therefore, the carrying amount for these restricted equity investments approximates fair value. The Corporation classifies the estimated fair value of such investments as Level 1. The Corporation’s investment in FHLB stock totaled $7 million at both December 31, 2015 and 2014 , and its investment in FRB stock totaled $85 million at both December 31, 2015 and 2014 . Other real estate Other real estate is included in “accrued income and other assets” on the consolidated balance sheets and includes primarily foreclosed property. Foreclosed property is initially recorded at fair value, less costs to sell, at the date of foreclosure, establishing a new cost basis. Subsequently, foreclosed property is carried at the lower of cost or fair value, less costs to sell. Other real estate may be carried at fair value on a nonrecurring basis when fair value is less than cost. Fair value is based upon independent market prices, appraised value or management's estimate of the value of the property. The Special Assets Group obtains updated independent market prices and appraised values, as required by state regulation or deemed necessary based on market conditions, and determines if additional write-downs are necessary. On a quarterly basis, senior management reviews all other real estate and determines whether the carrying values are reasonable, based on the length of time elapsed since receipt of independent market price or appraised value and current market conditions. When management determines that the fair value of other real estate requires additional adjustments, either as a result of a non-current appraisal or when there is no observable market price, the Corporation classifies the other real estate as Level 3. Deposit liabilities The estimated fair value of checking, savings and certain money market deposit accounts is represented by the amounts payable on demand. The estimated fair value of term deposits is calculated by discounting the scheduled cash flows using the period-end rates offered on these instruments. As such, the Corporation classifies the estimated fair value of deposit liabilities as Level 2. Short-term borrowings The carrying amount of federal funds purchased, securities sold under agreements to repurchase and other short-term borrowings approximates the estimated fair value. As such, the Corporation classifies the estimated fair value of short-term borrowings as Level 1. Medium- and long-term debt The estimated fair value of the Corporation's medium- and long-term debt is based on quoted market values when available. If quoted market values are not available, the estimated fair value is based on the market values of debt with similar characteristics. The Corporation classifies the estimated fair value of medium- and long-term debt as Level 2. Credit-related financial instruments Credit-related financial instruments include unused commitments to extend credit and letters of credit. These instruments generate ongoing fees which are recognized over the term of the commitment. In situations where credit losses are probable, the Corporation records an allowance. The carrying value of these instruments included in "accrued expenses and other liabilities" on the consolidated balance sheets, which includes the carrying value of the deferred fees plus the related allowance, approximates the estimated fair value. The Corporation classifies the estimated fair value of credit-related financial instruments as Level 3. For further information about fair value measurements refer to Note 2 . Other Short-Term Investments Other short-term investments include trading securities and loans held-for-sale. Trading securities are carried at fair value. Realized and unrealized gains or losses on trading securities are included in “other noninterest income” on the consolidated statements of income. Loans held-for-sale, typically residential mortgages originated with the intent to sell and occasionally may include other loans transferred to held-for-sale, are carried at the lower of cost or fair value. Fair value is determined in the aggregate for each portfolio. Changes in fair value are included in “other noninterest income” on the consolidated statements of income. Investment Securities Securities not held for trading purposes are classified as available-for-sale or held-to-maturity. Debt securities for which management has the intent and ability to hold to maturity are classified as held-to-maturity and recorded at amortized cost. Securities available-for-sale are recorded at fair value, with unrealized gains and losses, net of income taxes, reported as a separate component of other comprehensive income (loss) (OCI). Securities transferred from available-for-sale to held-to-maturity are reclassified at fair value on the date of transfer. The net unrealized gain (loss) at the date of transfer is included in historical cost and amortized over the remaining life of the related securities as a yield adjustment consistent with the amortization of the net unrealized gain (loss) included in accumulated other comprehensive loss on the same securities, resulting in no impact to net income. Investment securities are reviewed quarterly for possible other-than-temporary impairment (OTTI). In determining whether OTTI exists for debt securities in an unrealized loss position, the Corporation assesses the likelihood of selling the security prior to the recovery of its amortized cost basis. If the Corporation intends to sell the debt security or it is more likely than not that the Corporation will be required to sell the debt security prior to the recovery of its amortized cost basis, the debt security is written down to fair value, and the full amount of any impairment charge is recorded as a loss in “net securities gains” in the consolidated statements of income. If the Corporation does not intend to sell the debt security and it is more likely than not that the Corporation will not be required to sell the debt security prior to recovery of its amortized cost basis, only the credit component of any impairment of a debt security is recognized as a loss in “net securities gains” on the consolidated statements of income, with the remaining impairment recorded in OCI. The OTTI review for equity securities includes an analysis of the facts and circumstances of each individual investment and focuses on the severity of loss, the length of time the fair value has been below cost, the expectation for that security’s performance, the financial condition and near-term prospects of the issuer, and management’s intent and ability to hold the security to recovery. A decline in value of an equity security that is considered to be other-than-temporary is recorded as a loss in “net securities (losses) gains” on the consolidated statements of income. Gains or losses on the sale of securities are computed based on the adjusted cost of the specific security sold. For further information on investment securities, refer to Note 3 . Loans Loans and leases originated and held for investment are recorded at the principal balance outstanding, net of unearned income, charge-offs and unamortized deferred fees and costs. Interest income is recognized on loans and leases using the interest method. Loans and leases acquired in business combinations are initially recorded at fair value with no carryover of any existing allowance for loan losses. Acquired loans with evidence of credit quality deterioration at acquisition are reviewed to determine if it is probable that the Corporation will not be able to collect all contractual amounts due, including both principal and interest. When both conditions exist, such loans are accounted for as purchased credit-impaired (PCI) loans. The Corporation generally aggregates PCI loans into pools of loans based on common risk characteristics. The Corporation estimates the total cash flows expected to be collected from the pools of acquired PCI loans, which include undiscounted expected principal and interest, using credit risk, interest rate and prepayment risk models that incorporate management's best estimate of current key assumptions such as default rates, loss severity and payment speeds. The excess of the undiscounted total cash flows expected to be collected over the fair value of the related PCI loans represents the accretable yield, which is recognized as interest income on a level-yield basis over the life of the related loan pools. For acquired loans not deemed credit-impaired at acquisition, the difference between the initial fair value and the unpaid principal balance is recognized as interest income on a level-yield basis over the lives of the related loans. The Corporation assesses all loan modifications to determine whether a restructuring constitutes a troubled debt restructuring (TDR). A restructuring is considered a TDR when a borrower is experiencing financial difficulty and the Corporation grants a concession to the borrower. TDRs on accrual status at the original contractual rate of interest are considered performing. Nonperforming TDRs include TDRs on nonaccrual status and loans which have been renegotiated to less than the original contractual rates (reduced-rate loans). All TDRs are considered impaired loans. Loan Origination Fees and Costs Substantially all loan origination fees and costs are deferred and amortized to net interest income over the life of the related loan or over the commitment period as a yield adjustment. Net deferred income on originated loans, including unearned income and unamortized costs, fees, premiums and discounts, totaled $226 million and $267 million at December 31, 2015 and 2014 , respectively. Loan fees on unused commitments and net origination fees related to loans sold are recognized in noninterest income. Allowance for Credit Losses The allowance for credit losses includes both the allowance for loan losses and the allowance for credit losses on lending-related commitments. The Corporation disaggregates the loan portfolio into segments for purposes of determining the allowance for credit losses. These segments are based on the level at which the Corporation develops, documents and applies a systematic methodology to determine the allowance for credit losses. The Corporation's portfolio segments are business loans and retail loans. Business loans include the commercial, real estate construction, commercial mortgage, lease financing and international loan portfolios. Retail loans consist of traditional residential mortgage, home equity and other consumer loans. For further information on the Allowance for Credit Losses, refer to Note 4 . Allowance for Loan Losses The allowance for loan losses represents management’s assessment of probable, estimable losses inherent in the Corporation’s loan portfolio. The allowance for loan losses includes specific allowances, based on individual evaluations of certain loans, and allowances for homogeneous pools of loans with similar risk characteristics. The Corporation individually evaluates certain impaired loans on a quarterly basis and establishes specific allowances for such loans, if required. A loan is considered impaired when it is probable that interest or principal payments will not be made in accordance with

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS The Corporation utilizes fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures. The determination of fair values of financial instruments often requires the use of estimates. In cases where quoted market values in an active market are not available, the Corporation uses present value techniques and other valuation methods to estimate the fair values of its financial instruments. These valuation methods require considerable judgment and the resulting estimates of fair value can be significantly affected by the assumptions made and methods used. Trading securities, investment securities available-for-sale, derivatives and deferred compensation plan liabilities are recorded at fair value on a recurring basis. Additionally, from time to time, the Corporation may be required to record other assets and liabilities at fair value on a nonrecurring basis, such as impaired loans, other real estate (primarily foreclosed property), nonmarketable equity securities and certain other assets and liabilities. These nonrecurring fair value adjustments typically involve write-downs of individual assets or application of lower of cost or fair value accounting. Refer to Note 1 for further information about the fair value hierarchy, descriptions of the valuation methodologies and key inputs used to measure financial assets and liabilities recorded at fair value, as well as a description of the methods and significant assumptions used to estimate fair value disclosures for financial instruments not recorded at fair value in their entirety on a recurring basis. ASSETS AND LIABLILITIES RECORDED AT FAIR VALUE ON A RECURRING BASIS The following tables present the recorded amount of assets and liabilities measured at fair value on a recurring basis as of December 31, 2015 and 2014 . (in millions) Total Level 1 Level 2 Level 3 December 31, 2015 Trading securities: Deferred compensation plan assets $ 89 $ 89 $ — $ — Equity and other non-debt securities 3 3 — — Total trading securities 92 92 — — Investment securities available-for-sale: U.S. Treasury and other U.S. government agency securities 2,763 2,763 — — Residential mortgage-backed securities (a) 7,545 — 7,545 — State and municipal securities 9 — — 9 (b) Corporate debt securities 1 — — 1 (b) Equity and other non-debt securities 201 134 — 67 (b) Total investment securities available-for-sale 10,519 2,897 7,545 77 Derivative assets: Interest rate contracts 286 — 277 9 Energy derivative contracts 475 — 475 — Foreign exchange contracts 57 — 57 — Warrants 2 — — 2 Total derivative assets 820 — 809 11 Total assets at fair value $ 11,431 $ 2,989 $ 8,354 $ 88 Derivative liabilities: Interest rate contracts $ 92 $ — $ 92 $ — Energy derivative contracts 472 — 472 — Foreign exchange contracts 46 — 46 — Total derivative liabilities 610 — 610 — Deferred compensation plan liabilities 89 89 — — Total liabilities at fair value $ 699 $ 89 $ 610 $ — (a) Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises. (b) Auction-rate securities. (in millions) Total Level 1 Level 2 Level 3 December 31, 2014 Trading securities: Deferred compensation plan assets $ 94 $ 94 $ — $ — Investment securities available-for-sale: U.S. Treasury and other U.S. government agency securities 526 526 — — Residential mortgage-backed securities (a) 7,274 — 7,274 — State and municipal securities 23 — — 23 (b) Corporate debt securities 51 — 50 1 (b) Equity and other non-debt securities 242 130 — 112 (b) Total investment securities available-for-sale 8,116 656 7,324 136 Derivative assets: Interest rate contracts 328 — 328 — Energy derivative contracts 527 — 527 — Foreign exchange contracts 39 — 39 — Warrants 4 — — 4 Total derivative assets 898 — 894 4 Total assets at fair value $ 9,108 $ 750 $ 8,218 $ 140 Derivative liabilities: Interest rate contracts $ 102 $ — $ 102 $ — Energy derivative contracts 525 — 525 — Foreign exchange contracts 34 — 34 — Total derivative liabilities 661 — 661 — Deferred compensation plan liabilities 94 94 — — Total liabilities at fair value $ 755 $ 94 $ 661 $ — (a) Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises. (b) Auction-rate securities. There were no transfers of assets or liabilities recorded at fair value on a recurring basis into or out of Level 1, Level 2 and Level 3 fair value measurements during the years ended December 31, 2015 and 2014 . The following table summarizes the changes in Level 3 assets measured at fair value on a recurring basis for the years ended December 31, 2015 and 2014 . Net Realized/Unrealized Gains (Losses) (Pretax) Balance at Beginning of Period Recorded in Earnings Recorded in Other Comprehensive Income (Loss) Balance at End of Period (in millions) Realized Unrealized Sales Year Ended December 31, 2015 Investment securities available-for-sale: State and municipal securities (a) $ 23 $ — $ — $ — $ (14 ) $ 9 Corporate debt securities (a) 1 — — — — 1 Equity and other non-debt securities (a) 112 (2 ) (b) — 1 (c) (44 ) 67 Total investment securities 136 (2 ) (b) — 1 (c) (58 ) 77 Derivative assets: Interest rate contracts — — 9 (d) — — 9 Warrants 4 6 (d) (1 ) (d) — (7 ) 2 Year Ended December 31, 2014 Investment securities available-for-sale: State and municipal securities (a) $ 22 $ — $ — $ 1 (c) $ — $ 23 Corporate debt securities (a) 1 — — — — 1 Equity and other non-debt securities (a) 136 2 (b) — 7 (c) (33 ) 112 Total investment securities 159 2 (b) — 8 (c) (33 ) 136 Derivative assets: Warrants 3 7 (d) 1 (d) — (7 ) 4 (a) Auction-rate securities. (b) Realized and unrealized gains and losses due to changes in fair value recorded in "net securities losses" on the consolidated statements of income. (c) Recorded in "net unrealized (losses) gains on investment securities available-for-sale" in other comprehensive income. (d) Realized and unrealized gains and losses due to changes in fair value recorded in "other noninterest income" on the consolidated statements of income. ASSETS AND LIABILITIES RECORDED AT FAIR VALUE ON A NONRECURRING BASIS The Corporation may be required, from time to time, to record certain assets and liabilities at fair value on a nonrecurring basis. These include assets that are recorded at the lower of cost or fair value, and were recognized at fair value since it was less than cost at the end of the period. The following table presents assets recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014 . No liabilities were recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014 . (in millions) Total Level 2 Level 3 December 31, 2015 Loans held-for-sale: Commercial $ 8 $ 8 $ — Loans: Commercial 134 — 134 Commercial mortgage 11 — 11 International 8 — 8 Total loans 153 — 153 Nonmarketable equity securities 1 — 1 Other real estate 2 — 2 Total assets at fair value $ 164 $ 8 $ 156 December 31, 2014 Loans: Commercial $ 38 $ — $ 38 Commercial mortgage 26 — 26 Total loans 64 — 64 Nonmarketable equity securities 2 — 2 Other real estate 2 — 2 Total assets at fair value $ 68 $ — $ 68 Level 3 assets recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014 included loans for which a specific allowance was established based on the fair value of collateral and other real estate for which fair value of the properties was less than the cost basis. For both asset classes, the unobservable inputs were the additional adjustments applied by management to the appraised values to reflect such factors as non-current appraisals and revisions to estimated time to sell. These adjustments are determined based on qualitative judgments made by management on a case-by-case basis and are not quantifiable inputs, although they are used in the determination of fair value. The following table presents quantitative information related to the significant unobservable inputs utilized in the Corporation's Level 3 recurring fair value measurement as of December 31, 2015 and December 31, 2014 . The Corporation's Level 3 recurring fair value measurements include auction-rate securities where fair value is determined using an income approach based on a discounted cash flow model. The inputs in the table below reflect management's expectation of continued illiquidity in the secondary auction-rate securities market due to a lack of market activity for the issuers remaining in the portfolio, a lack of market incentives for issuer redemptions, and the expectation for a continuing low interest rate environment. The December 31, 2015 workout periods reflect management's expectation of the pace at which short-term interest rates could rise. Discounted Cash Flow Model Unobservable Input Fair Value (in millions) Discount Rate Workout Period (in years) December 31, 2015 State and municipal securities (a) $ 9 3% - 8% 1 - 2 Equity and other non-debt securities (a) 67 4% - 9% 1 December 31, 2014 State and municipal securities (a) $ 23 3% - 9% 1 - 3 Equity and other non-debt securities (a) 112 4% - 8% 1 - 2 (a) Auction-rate securities. ESTIMATED FAIR VALUES OF FINANCIAL INSTRUMENTS NOT RECORDED AT FAIR VALUE ON A RECURRING BASIS The Corporation typically holds the majority of its financial instruments until maturity and thus does not expect to realize many of the estimated fair value amounts disclosed. The disclosures also do not include estimated fair value amounts for items that are not defined as financial instruments, but which have significant value. These include such items as core deposit intangibles, the future earnings potential of significant customer relationships and the value of trust operations and other fee generating businesses. The Corporation believes the imprecision of an estimate could be significant. The carrying amount and estimated fair value of financial instruments not recorded at fair value in their entirety on a recurring basis on the Corporation’s consolidated balance sheets are as follows: Carrying Amount Estimated Fair Value (in millions) Total Level 1 Level 2 Level 3 December 31, 2015 Assets Cash and due from banks $ 1,157 $ 1,157 $ 1,157 $ — $ — Interest-bearing deposits with banks 4,990 4,990 4,990 — — Investment securities held-to-maturity 1,981 1,973 — 1,973 — Loans held-for-sale (a) 21 21 — 21 — Total loans, net of allowance for loan losses (b) 48,450 48,269 — — 48,269 Customers’ liability on acceptances outstanding 5 5 5 — — Nonmarketable equity securities (c) 10 18 — — 18 Restricted equity investments 92 92 92 — — Liabilities Demand deposits (noninterest-bearing) 30,839 30,839 — 30,839 — Interest-bearing deposits 25,462 25,462 — 25,462 — Customer certificates of deposit 3,552 3,536 — 3,536 — Total deposits 59,853 59,837 — 59,837 — Short-term borrowings 23 23 23 — — Acceptances outstanding 5 5 5 — — Medium- and long-term debt 3,058 3,032 — 3,032 — Credit-related financial instruments (83 ) (83 ) — — (83 ) December 31, 2014 Assets Cash and due from banks $ 1,026 $ 1,026 $ 1,026 $ — $ — Interest-bearing deposits with banks 5,045 5,045 5,045 — — Investment securities held-to-maturity 1,935 1,933 — 1,933 — Loans held-for-sale (a) 5 5 — 5 — Total loans, net of allowance for loan losses (b) 47,999 47,932 — — 47,932 Customers’ liability on acceptances outstanding 10 10 10 — — Nonmarketable equity securities (c) 11 18 — — 18 Restricted equity investments 92 92 92 — — Liabilities Demand deposits (noninterest-bearing) 27,224 27,224 — 27,224 — Interest-bearing deposits 25,841 25,841 — 25,841 — Customer certificates of deposit 4,421 4,411 — 4,411 — Total deposits 57,486 57,476 — 57,476 — Short-term borrowings 116 116 116 — — Acceptances outstanding 10 10 10 — — Medium- and long-term debt 2,675 2,681 — 2,681 — Credit-related financial instruments (85 ) (85 ) — — (85 ) (a) Included $8 million and no impaired loans held-for-sale recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014 , respectively. (b) Included $153 million and $64 million of impaired loans recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014 , respectively. (c) Included $1 million and $2 million of nonmarketable equity securities recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014 , respectively.

Investment Securities

Investment Securities	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Investment Securities	INVESTMENT SECURITIES A summary of the Corporation’s investment securities follows: (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value December 31, 2015 Investment securities available-for-sale: U.S. Treasury and other U.S. government agency securities $ 2,769 $ 1 $ 7 $ 2,763 Residential mortgage-backed securities (a) 7,513 76 44 7,545 State and municipal securities 9 — — 9 Corporate debt securities 1 — — 1 Equity and other non-debt securities 199 2 — 201 Total investment securities available-for-sale (b) $ 10,491 $ 79 $ 51 $ 10,519 Investment securities held-to-maturity (c): Residential mortgage-backed securities (a) $ 1,981 $ 2 $ 10 $ 1,973 December 31, 2014 Investment securities available-for-sale: U.S. Treasury and other U.S. government agency securities $ 526 $ — $ — $ 526 Residential mortgage-backed securities (a) 7,192 122 40 7,274 State and municipal securities 24 — 1 23 Corporate debt securities 51 — — 51 Equity and other non-debt securities 242 1 1 242 Total investment securities available-for-sale (b) $ 8,035 $ 123 $ 42 $ 8,116 Investment securities held-to-maturity (c): Residential mortgage-backed securities (a) $ 1,935 $ — $ 2 $ 1,933 (a) Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises. (b) Included auction-rate securities at amortized cost and fair value of $76 million and $77 million , respectively, as of December 31, 2015 and $137 million and $136 million , respectively, as of December 31, 2014 . (c) The amortized cost of investment securities held-to-maturity included net unrealized losses of $15 million at December 31, 2015 and $23 million at December 31, 2014 related to securities transferred from available-for-sale, which are included in accumulated other comprehensive loss. During the fourth quarter 2014, the Corporation transferred residential mortgage-backed securities with a fair value of approximately $2.0 billion from available-for-sale to held-to-maturity. Accumulated other comprehensive loss included pretax net unrealized losses of $23 million at the date of transfer. A summary of the Corporation’s investment securities in an unrealized loss position as of December 31, 2015 and 2014 follows: Temporarily Impaired Less than 12 Months 12 Months or more Total (in millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses December 31, 2015 U.S. Treasury and other U.S. government agency securities $ 2,265 $ 7 $ — $ — $ 2,265 $ 7 Residential mortgage-backed securities (a) 2,665 21 1,976 51 4,641 72 State and municipal securities (b) — — 9 — (c) 9 — (c) Corporate debt securities (b) — — 1 — (c) 1 — (c) Equity and other non-debt securities (b) 14 — (c) — — 14 — (c) Total impaired securities $ 4,944 $ 28 $ 1,986 $ 51 $ 6,930 $ 79 December 31, 2014 U.S. Treasury and other U.S. government agency securities $ 298 $ — (c) $ — $ — $ 298 $ — (c) Residential mortgage-backed securities (a) 626 3 3,112 71 3,738 74 State and municipal securities (b) — — 22 1 22 1 Corporate debt securities (b) — — 1 — (c) 1 — (c) Equity and other non-debt securities (b) — — 112 1 112 1 Total impaired securities $ 924 $ 3 $ 3,247 $ 73 $ 4,171 $ 76 (a) Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises. (b) Primarily auction-rate securities. (c) Unrealized losses less than $0.5 million. At December 31, 2015 , the Corporation had 179 securities in an unrealized loss position with no credit impairment, including 26 U.S. Treasury securities, 124 residential mortgage-backed securities, 16 state and municipal auction-rate securities, one corporate auction-rate debt security and 12 equity and other non-debt auction-rate preferred securities. As of December 31, 2015 , approximately 94 percent of the aggregate par value of auction-rate securities have been redeemed or sold since acquisition, of which approximately 91 percent were redeemed at or above cost. The unrealized losses for these securities resulted from changes in market interest rates and liquidity. The Corporation ultimately expects full collection of the carrying amount of these securities, does not intend to sell the securities in an unrealized loss position, and it is not more-likely-than-not that the Corporation will be required to sell the securities in an unrealized loss position prior to recovery of amortized cost. The Corporation does not consider these securities to be other-than-temporarily impaired at December 31, 2015 . Sales, calls and write-downs of investment securities available-for-sale resulted in the following gains and losses recorded in “net securities losses” on the consolidated statements of income, computed based on the adjusted cost of the specific security. (in millions) Years Ended December 31 2015 2014 2013 Securities gains $ — $ 2 $ 1 Securities losses (2 ) (2 ) (2 ) Net securities losses $ (2 ) $ — $ (1 ) The following table summarizes the amortized cost and fair values of debt securities by contractual maturity. Securities with multiple maturity dates are classified in the period of final maturity. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. (in millions) Available-for-sale Held-to-maturity December 31, 2015 Amortized Cost Fair Value Amortized Cost Fair Value Contractual maturity Within one year $ 10 $ 10 $ — $ — After one year through five years 2,857 2,851 — — After five years through ten years 1,268 1,308 — — After ten years 6,157 6,149 1,981 1,973 Subtotal 10,292 10,318 1,981 1,973 Equity and other non-debt securities 199 201 — — Total investment securities $ 10,491 $ 10,519 $ 1,981 $ 1,973 Included in the contractual maturity distribution in the table above were residential mortgage-backed securities available-for-sale with a total amortized cost and fair value of $7.5 billion , and residential mortgage-backed securities held-to-maturity with a total amortized cost and fair value of $2.0 billion . The actual cash flows of mortgage-backed securities may differ from contractual maturity as the borrowers of the underlying loans may exercise prepayment options. At December 31, 2015 , investment securities with a carrying value of $2.4 billion were pledged where permitted or required by law to secure $1.2 billion of liabilities, primarily public and other deposits of state and local government agencies and derivative instruments.

Credit Quality And Allowance Fo

Credit Quality And Allowance For Credit Losses	12 Months Ended
	Dec. 31, 2015
Credit Quality And Allowance For Credit Losses [Abstract]
Credit Quality And Allowance For Credit Losses	CREDIT QUALITY AND ALLOWANCE FOR CREDIT LOSSES The following table presents an aging analysis of the recorded balance of loans. Loans Past Due and Still Accruing (in millions) 30-59 Days 60-89 Days 90 Days or More Total Nonaccrual Loans Current Loans Total Loans December 31, 2015 Business loans: Commercial $ 46 $ 12 $ 13 $ 71 $ 238 $ 31,350 $ 31,659 Real estate construction: Commercial Real Estate business line (a) 5 — — 5 — 1,676 1,681 Other business lines (b) 3 — — 3 1 316 320 Total real estate construction 8 — — 8 1 1,992 2,001 Commercial mortgage: Commercial Real Estate business line (a) 7 — 1 8 16 2,080 2,104 Other business lines (b) 7 5 3 15 44 6,814 6,873 Total commercial mortgage 14 5 4 23 60 8,894 8,977 Lease financing — — — — 6 718 724 International 2 — — 2 8 1,358 1,368 Total business loans 70 17 17 104 313 44,312 44,729 Retail loans: Residential mortgage 26 1 — 27 27 1,816 1,870 Consumer: Home equity 5 3 — 8 27 1,685 1,720 Other consumer 7 — — 7 — 758 765 Total consumer 12 3 — 15 27 2,443 2,485 Total retail loans 38 4 — 42 54 4,259 4,355 Total loans $ 108 $ 21 $ 17 $ 146 $ 367 $ 48,571 $ 49,084 December 31, 2014 Business loans: Commercial $ 58 $ 13 $ 1 $ 72 $ 109 $ 31,339 $ 31,520 Real estate construction: Commercial Real Estate business line (a) 3 — — 3 1 1,602 1,606 Other business lines (b) 12 — — 12 1 336 349 Total real estate construction 15 — — 15 2 1,938 1,955 Commercial mortgage: Commercial Real Estate business line (a) 8 1 1 10 22 1,758 1,790 Other business lines (b) 16 12 2 30 73 6,711 6,814 Total commercial mortgage 24 13 3 40 95 8,469 8,604 Lease financing — — — — — 805 805 International 9 — — 9 — 1,487 1,496 Total business loans 106 26 4 136 206 44,038 44,380 Retail loans: Residential mortgage 9 2 — 11 36 1,784 1,831 Consumer: Home equity 5 3 — 8 30 1,620 1,658 Other consumer 12 — 1 13 1 710 724 Total consumer 17 3 1 21 31 2,330 2,382 Total retail loans 26 5 1 32 67 4,114 4,213 Total loans $ 132 $ 31 $ 5 $ 168 $ 273 $ 48,152 $ 48,593 (a) Primarily loans to real estate developers. (b) Primarily loans secured by owner-occupied real estate. The following table presents loans by credit quality indicator, based on internal risk ratings assigned to each business loan at the time of approval and subjected to subsequent reviews, generally at least annually, and to pools of retail loans with similar risk characteristics. Internally Assigned Rating (in millions) Pass (a) Special Mention (b) Substandard (c) Nonaccrual (d) Total December 31, 2015 Business loans: Commercial $ 29,117 $ 1,293 $ 1,011 $ 238 $ 31,659 Real estate construction: Commercial Real Estate business line (e) 1,681 — — — 1,681 Other business lines (f) 318 1 — 1 320 Total real estate construction 1,999 1 — 1 2,001 Commercial mortgage: Commercial Real Estate business line (e) 2,031 31 26 16 2,104 Other business lines (f) 6,536 172 121 44 6,873 Total commercial mortgage 8,567 203 147 60 8,977 Lease financing 693 17 8 6 724 International 1,245 59 56 8 1,368 Total business loans 41,621 1,573 1,222 313 44,729 Retail loans: Residential mortgage 1,828 2 13 27 1,870 Consumer: Home equity 1,687 1 5 27 1,720 Other consumer 755 3 7 — 765 Total consumer 2,442 4 12 27 2,485 Total retail loans 4,270 6 25 54 4,355 Total loans $ 45,891 $ 1,579 $ 1,247 $ 367 $ 49,084 December 31, 2014 Business loans: Commercial $ 30,310 $ 560 $ 541 $ 109 $ 31,520 Real estate construction: Commercial Real Estate business line (e) 1,594 11 — 1 1,606 Other business lines (f) 336 7 5 1 349 Total real estate construction 1,930 18 5 2 1,955 Commercial mortgage: Commercial Real Estate business line (e) 1,652 69 47 22 1,790 Other business lines (f) 6,434 138 169 73 6,814 Total commercial mortgage 8,086 207 216 95 8,604 Lease financing 778 26 1 — 805 International 1,468 15 13 — 1,496 Total business loans 42,572 826 776 206 44,380 Retail loans: Residential mortgage 1,790 2 3 36 1,831 Consumer: Home equity 1,620 — 8 30 1,658 Other consumer 718 3 2 1 724 Total consumer 2,338 3 10 31 2,382 Total retail loans 4,128 5 13 67 4,213 Total loans $ 46,700 $ 831 $ 789 $ 273 $ 48,593 (a) Includes all loans not included in the categories of special mention, substandard or nonaccrual. (b) Special mention loans are accruing loans that have potential credit weaknesses that deserve management’s close attention, such as loans to borrowers who may be experiencing financial difficulties that may result in deterioration of repayment prospects from the borrower at some future date. This category is generally consistent with the "special mention" category as defined by regulatory authorities. (c) Substandard loans are accruing loans that have a well-defined weakness, or weaknesses, such as loans to borrowers who may be experiencing losses from operations or inadequate liquidity of a degree and duration that jeopardizes the orderly repayment of the loan. Substandard loans also are distinguished by the distinct possibility of loss in the future if these weaknesses are not corrected. PCI loans are included in the substandard category. This category is generally consistent with the "substandard" category as defined by regulatory authorities. (d) Nonaccrual loans are loans for which the accrual of interest has been discontinued. For further information regarding nonaccrual loans, refer to the Nonperforming Assets subheading in Note 1 - Basis of Presentation and Accounting Policies. A significant majority of nonaccrual loans are generally consistent with the "substandard" category and the remainder are generally consistent with the "doubtful" category as defined by regulatory authorities. (e) Primarily loans to real estate developers. (f) Primarily loans secured by owner-occupied real estate. The following table summarizes nonperforming assets. (in millions) December 31, 2015 December 31, 2014 Nonaccrual loans $ 367 $ 273 Reduced-rate loans (a) 12 17 Total nonperforming loans 379 290 Foreclosed property 12 10 Total nonperforming assets $ 391 $ 300 (a) There were no reduced-rate business loans at both December 31, 2015 and at December 31, 2014 . Reduced-rate retail loans totaled $12 million and $17 million at December 31, 2015 and 2014 , respectively. Nonaccrual loans included retail loans secured by residential real estate properties in process of foreclosure of $1 million at December 31, 2015 . Allowance for Credit Losses The following table details the changes in the allowance for loan losses and related loan amounts. 2015 2014 2013 (in millions) Business Loans Retail Loans Total Business Loans Retail Loans Total Business Loans Retail Loans Total Years Ended December 31 Allowance for loan losses: Balance at beginning of period $ 534 $ 60 $ 594 $ 531 $ 67 $ 598 $ 552 $ 77 $ 629 Loan charge-offs (157 ) (11 ) (168 ) (87 ) (15 ) (102 ) (130 ) (23 ) (153 ) Recoveries on loans previously charged-off 55 13 68 68 9 77 70 10 80 Net loan (charge-offs) recoveries (102 ) 2 (100 ) (19 ) (6 ) (25 ) (60 ) (13 ) (73 ) Provision for loan losses 149 (7 ) 142 23 (1 ) 22 39 3 42 Foreign currency translation adjustment (2 ) — (2 ) (1 ) — (1 ) — — — Balance at end of period $ 579 $ 55 $ 634 $ 534 $ 60 $ 594 $ 531 $ 67 $ 598 As a percentage of total loans 1.30 % 1.26 % 1.29 % 1.20 % 1.43 % 1.22 % 1.28 % 1.70 % 1.32 % December 31 Allowance for loan losses: Individually evaluated for impairment $ 53 $ — $ 53 $ 39 $ — $ 39 $ 57 $ — $ 57 Collectively evaluated for impairment 526 55 581 495 60 555 474 67 541 Total allowance for loan losses $ 579 $ 55 $ 634 $ 534 $ 60 $ 594 $ 531 $ 67 $ 598 Loans: Individually evaluated for impairment $ 393 $ 31 $ 424 $ 177 $ 42 $ 219 $ 223 $ 51 $ 274 Collectively evaluated for impairment 44,336 4,323 48,659 44,203 4,169 48,372 41,311 3,880 45,191 PCI loans (a) — 1 1 — 2 2 2 3 5 Total loans evaluated for impairment $ 44,729 $ 4,355 $ 49,084 $ 44,380 $ 4,213 $ 48,593 $ 41,536 $ 3,934 $ 45,470 (a) No allowance for loan losses was required for PCI loans at December 31, 2015 , 2014 and 2013 . Changes in the allowance for credit losses on lending-related commitments, included in "accrued expenses and other liabilities" on the consolidated balance sheets, are summarized in the following table. (in millions) Years Ended December 31 2015 2014 2013 Balance at beginning of period $ 41 $ 36 $ 32 Charge-offs on lending-related commitments (a) (1 ) — — Provision for credit losses on lending-related commitments 5 5 4 Balance at end of period $ 45 $ 41 $ 36 (a) Charge-offs result from the sale of unfunded lending-related commitments. Individually Evaluated Impaired Loans The following table presents additional information regarding individually evaluated impaired loans. Recorded Investment In: (in millions) Impaired Loans with No Related Allowance Impaired Loans with Related Allowance Total Impaired Loans Unpaid Principal Balance Related Allowance for Loan Losses December 31, 2015 Business loans: Commercial $ 82 $ 252 $ 334 $ 549 $ 45 Commercial mortgage: Commercial Real Estate business line (a) 7 8 15 38 1 Other business lines (b) 2 32 34 55 5 Total commercial mortgage 9 40 49 93 6 International — 10 10 17 2 Total business loans 91 302 393 659 53 Retail loans: Residential mortgage 13 — 13 13 — Consumer: Home equity 12 — 12 16 — Other consumer 6 — 6 10 — Total consumer 18 — 18 26 — Total retail loans (c) 31 — 31 39 — Total individually evaluated impaired loans $ 122 $ 302 $ 424 $ 698 $ 53 December 31, 2014 Business loans: Commercial $ 7 $ 103 $ 110 $ 148 $ 29 Real estate construction: Other business lines (b) — 1 1 1 — Commercial mortgage: Commercial Real Estate business line (a) — 19 19 41 8 Other business lines (b) 4 43 47 63 2 Total commercial mortgage 4 62 66 104 10 Total business loans 11 166 177 253 39 Retail loans: Residential mortgage 25 — 25 28 — Consumer: Home equity 12 — 12 16 — Other consumer 5 — 5 7 — Total consumer 17 — 17 23 — Total retail loans (c) 42 — 42 51 — Total individually evaluated impaired loans $ 53 $ 166 $ 219 $ 304 $ 39 (a) Primarily loans to real estate developers. (b) Primarily loans secured by owner-occupied real estate. (c) Individually evaluated retail loans had no related allowance for loan losses, primarily due to policy which results in direct write-downs of restructured retail loans. The following table presents information regarding average individually evaluated impaired loans and the related interest recognized. Interest income recognized for the period primarily related to reduced-rate loans. Individually Evaluated Impaired Loans 2015 2014 2013 (in millions) Average Balance for the Period Interest Income Recognized for the Period Average Balance for the Period Interest Income Recognized for the Period Average Balance for the Period Interest Income Recognized for the Period Years Ended December 31 Business loans: Commercial $ 206 $ 5 $ 77 $ 2 $ 99 $ 2 Real estate construction: Commercial Real Estate business line (a) — — 14 — 25 — Commercial mortgage: Commercial Real Estate business line (a) 16 — 48 — 81 — Other business lines (b) 39 1 64 2 105 3 Total commercial mortgage 55 1 112 2 186 3 International 6 — 2 — 1 — Total business loans 267 6 205 4 311 5 Retail loans: Residential mortgage 21 — 30 — 35 — Consumer: Home equity 12 — 12 — 8 — Other consumer 6 — 4 — 4 — Total consumer 18 — 16 — 12 — Total retail loans 39 — 46 — 47 — Total individually evaluated impaired loans $ 306 $ 6 $ 251 $ 4 $ 358 $ 5 (a) Primarily loans to real estate developers. (b) Primarily loans secured by owner-occupied real estate. Troubled Debt Restructurings The following tables detail the recorded balance at December 31, 2015 and 2014 of loans considered to be TDRs that were restructured during the years ended December 31, 2015 and 2014 , by type of modification. In cases of loans with more than one type of modification, the loans were categorized based on the most significant modification. 2015 2014 Type of Modification Type of Modification (in millions) Principal Deferrals (a) Interest Rate Reductions Total Modifications Principal Deferrals (a) Interest Rate Reductions Total Modifications Years Ended December 31 Business loans: Commercial $ 160 $ — $ 160 $ 22 $ — $ 22 Commercial mortgage: Commercial Real Estate business line (b) 8 — 8 — — — Other business lines (c) 6 — 6 6 — 6 Total commercial mortgage 14 — 14 6 — 6 International 2 — 2 — — — Total business loans 176 — 176 28 — 28 Retail loans: Residential mortgage — — — 1 (d) — 1 Consumer: Home equity 1 (d) 2 3 1 (d) 3 4 Other consumer — — — 1 (d) — 1 Total consumer 1 2 3 2 3 5 Total retail loans 1 2 3 3 3 6 Total loans $ 177 $ 2 $ 179 $ 31 $ 3 $ 34 (a) Primarily represents loan balances where terms were extended 90 days or more at or above contractual interest rates. (b) Primarily loans to real estate developers. (c) Primarily loans secured by owner-occupied real estate. (d) Includes bankruptcy loans for which the court has discharged the borrower's obligation and the borrower has not reaffirmed the debt. At December 31, 2015 and 2014 , commitments to lend additional funds to borrowers whose terms have been modified in TDRs totaled $6 million and $3 million , respectively. The majority of the modifications considered to be TDRs that occurred during the years ended December 31, 2015 and 2014 were principal deferrals. The Corporation charges interest on principal balances outstanding during deferral periods. Additionally, none of the modifications involved forgiveness of principal. As a result, the current and future financial effects of the recorded balance of loans considered to be TDRs that were restructured during the years ended December 31, 2015 and 2014 were insignificant. On an ongoing basis, the Corporation monitors the performance of modified loans to their restructured terms. In the event of a subsequent default, the allowance for loan losses continues to be reassessed on the basis of an individual evaluation of the loan. The following table presents information regarding the recorded balance at December 31, 2015 and 2014 of loans modified by principal deferral during the years ended December 31, 2015 and 2014 , and those principal deferrals which experienced a subsequent default during the same periods. For principal deferrals, incremental deterioration in the credit quality of the loan, represented by a downgrade in the risk rating of the loan, for example, due to missed interest payments or a reduction of collateral value, is considered a subsequent default. 2015 2014 (in millions) Balance at December 31 Subsequent Default in the Year Ended December 31 Balance at December 31 Subsequent Default in the Year Ended December 31 Principal deferrals: Business loans: Commercial $ 160 $ 16 $ 22 $ 1 Commercial mortgage: Commercial Real Estate business line (a) 8 1 — — Other business lines (b) 6 1 6 2 Total commercial mortgage 14 2 6 2 International 2 — — — Total business loans 176 18 28 3 Retail loans: Residential mortgage — — 1 (c) — Consumer: Home equity 1 (c) — 1 (c) — Other consumer — — 1 (c) — Total consumer 1 — 2 — Total retail loans 1 — 3 — Total principal deferrals $ 177 $ 18 $ 31 $ 3 (a) Primarily loans to real estate developers. (b) Primarily loans secured by owner-occupied real estate. (c) Includes bankruptcy loans for which the court has discharged the borrower's obligation and the borrower has not reaffirmed the debt. During the years ended December 31, 2015 and 2014 , loans with a carrying value of $2 million and $3 million at December 31, 2015 and 2014 , respectively, were modified by interest rate reduction. For reduced-rate loans , a subsequent payment default is defined in terms of delinquency, when a principal or interest payment is 90 days past due. There were no subsequent payment defaults of reduced rate loans during the years ended December 31, 2015 and 2014 .

Significant Group Concentration

Significant Group Concentrations of Credit Risk	12 Months Ended
	Dec. 31, 2015
Significant Group Concentrations of Credit Risk [Abstract]
Significant Group Concentrations of Credit Risk	SIGNIFICANT GROUP CONCENTRATIONS OF CREDIT RISK Concentrations of credit risk may exist when a number of borrowers are engaged in similar activities, or activities in the same geographic region, and have similar economic characteristics that would cause them to be similarly impacted by changes in economic or other conditions. Concentrations of both on-balance sheet and off-balance sheet credit risk are controlled and monitored as part of credit policies. The Corporation is a regional financial services holding company with a geographic concentration of its on-balance-sheet and off-balance-sheet activities in Michigan, California and Texas. As outlined below, the Corporation has a concentration of credit risk with the automotive industry. Loans to automotive dealers and to borrowers involved with automotive production are reported as automotive, as management believes these loans have similar economic characteristics that might cause them to react similarly to changes in economic conditions. This aggregation involves the exercise of judgment. Included in automotive production are: (a) original equipment manufacturers and Tier 1 and Tier 2 suppliers that produce components used in vehicles and whose primary revenue source is automotive-related (“primary” defined as greater than 50%) and (b) other manufacturers that produce components used in vehicles and whose primary revenue source is automotive-related. Loans less than $1 million and loans recorded in the Small Business loan portfolio were excluded from the definition. Outstanding loans, included in "commercial loans" on the consolidated balance sheets, and total exposure from loans, unused commitments and standby letters of credit to companies related to the automotive industry were as follows: (in millions) December 31 2015 2014 Automotive loans: Production $ 1,266 $ 1,236 Dealer 6,573 6,431 Total automotive loans $ 7,839 $ 7,667 Total automotive exposure: Production $ 2,452 $ 2,408 Dealer 8,209 7,763 Total automotive exposure $ 10,661 $ 10,171 Further, the Corporation’s portfolio of commercial real estate loans, which includes real estate construction and commercial mortgage loans, was as follows. (in millions) December 31 2015 2014 Real estate construction loans: Commercial Real Estate business line (a) $ 1,681 $ 1,606 Other business lines (b) 320 349 Total real estate construction loans 2,001 1,955 Commercial mortgage loans: Commercial Real Estate business line (a) 2,104 1,790 Other business lines (b) 6,873 6,814 Total commercial mortgage loans 8,977 8,604 Total commercial real estate loans $ 10,978 $ 10,559 Total unused commitments on commercial real estate loans $ 3,063 $ 2,335 (a) Primarily loans to real estate developers. (b) Primarily loans secured by owner-occupied real estate.

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Premises and Equipment	PREMISES AND EQUIPMENT A summary of premises and equipment by major category follows: (in millions) December 31 2015 2014 Land $ 87 $ 88 Buildings and improvements 862 808 Furniture and equipment 490 508 Total cost 1,439 1,404 Less: Accumulated depreciation and amortization (889 ) (872 ) Net book value $ 550 $ 532 The Corporation conducts a portion of its business from leased facilities and leases certain equipment. Rental expense for leased properties and equipment amounted to $79 million , $89 million and $78 million in 2015 , 2014 and 2013 , respectively. Rental expense in 2014 included approximately $10 million of lease termination charges. As of December 31, 2015 , future minimum rental payments under operating leases were as follows: (in millions) Years Ending December 31 2016 $ 73 2017 70 2018 62 2019 53 2020 44 Thereafter 154 Total $ 456

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Core Deposit Intangibles	GOODWILL AND CORE DEPOSIT INTANGIBLES The following table summarizes the carrying value of goodwill for the years ended December 31, 2015 , 2014 and 2013 . (in millions) December 31 2015 2014 2013 Business Bank $ 380 $ 380 $ 380 Retail Bank 194 194 194 Wealth Management 61 61 61 Total $ 635 $ 635 $ 635 The Corporation performs its annual evaluation of goodwill impairment in the third quarter of each year and on an interim basis if events or changes in circumstances between annual tests indicate goodwill might be impaired. In 2015 and 2014 , the annual test of goodwill impairment was performed as of the beginning of the third quarter. At the conclusion of the first step of the annual and interim goodwill impairment tests performed in 2015 and 2014 the estimated fair values of all reporting units exceeded their carrying amounts, including goodwill, indicating that goodwill was not impaired. There have been no events since the annual test performed in the third quarter 2015 that would indicate that it was more likely than not that goodwill had become impaired. A summary of core deposit intangible carrying value and related accumulated amortization follows: (in millions) December 31 2015 2014 Gross carrying amount $ 34 $ 34 Accumulated amortization (24 ) (21 ) Net carrying amount $ 10 $ 13 The Corporation recorded amortization expense related to the core deposit intangible of $3 million for both the years ended December 31, 2015 and 2014 . At December 31, 2015 , estimated future amortization expense was as follows: (in millions) Years Ending December 31 2016 $ 2 2017 2 2018 2 2019 2 2020 1 Thereafter 1 Total $ 10

Derivative And Credit-Related F

Derivative And Credit-Related Financial Instruments	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative And Credit-Related Financial Instruments	DERIVATIVE AND CREDIT-RELATED FINANCIAL INSTRUMENTS In the normal course of business, the Corporation enters into various transactions involving derivative and credit-related financial instruments to manage exposure to fluctuations in interest rate, foreign currency and other market risks and to meet the financing needs of customers (customer-initiated derivatives). These financial instruments involve, to varying degrees, elements of market and credit risk. Market and credit risk are included in the determination of fair value. Market risk is the potential loss that may result from movements in interest rates, foreign currency exchange rates or energy commodity prices that cause an unfavorable change in the value of a financial instrument. The Corporation manages this risk by establishing monetary exposure limits and monitoring compliance with those limits. Market risk inherent in interest rate and energy contracts entered into on behalf of customers is mitigated by taking offsetting positions, except in those circumstances when the amount, tenor and/or contract rate level results in negligible economic risk, whereby the cost of purchasing an offsetting contract is not economically justifiable. The Corporation mitigates most of the inherent market risk in foreign exchange contracts entered into on behalf of customers by taking offsetting positions and manages the remainder through individual foreign currency position limits and aggregate value-at-risk limits. These limits are established annually and reviewed quarterly. Market risk inherent in derivative instruments held or issued for risk management purposes is typically offset by changes in the fair value of the assets or liabilities being hedged. Credit risk is the possible loss that may occur in the event of nonperformance by the counterparty to a financial instrument. The Corporation attempts to minimize credit risk arising from customer-initiated derivatives by evaluating the creditworthiness of each customer, adhering to the same credit approval process used for traditional lending activities and obtaining collateral as deemed necessary. Derivatives with dealer counterparties are either cleared through a clearinghouse or settled directly with a single counterparty. For derivatives settled directly with dealer counterparties, the Corporation utilizes counterparty risk limits and monitoring procedures as well as master netting arrangements and bilateral collateral agreements to facilitate the management of credit risk. Master netting arrangements effectively reduce credit risk by permitting settlement of positive and negative positions and offset cash collateral held with the same counterparty on a net basis. Bilateral collateral agreements require daily exchange of cash or highly rated securities issued by the U.S. Treasury or other U.S. government entities to collateralize amounts due to either party beyond certain risk limits. At December 31, 2015 , counterparties with bilateral collateral agreements had pledged $139 million of marketable investment securities and deposited $354 million of cash with the Corporation to secure the fair value of contracts in an unrealized gain position, and the Corporation had pledged $3 million of investment securities and posted $3 million of cash as collateral for contracts in an unrealized loss position. For those counterparties not covered under bilateral collateral agreements, collateral is obtained, if deemed necessary, based on the results of management’s credit evaluation of the counterparty. Collateral varies, but may include cash, investment securities, accounts receivable, equipment or real estate. Included in the fair value of derivative instruments are credit valuation adjustments reflecting counterparty credit risk. These adjustments are determined by applying a credit spread for the counterparty or the Corporation, as appropriate, to the total expected exposure of the derivative. The aggregate fair value of all derivative instruments with credit-risk-related contingent features that were in a liability position on December 31, 2015 was $2 million , for which the Corporation had pledged collateral of $1 million in the normal course of business. The credit-risk-related contingent features require the Corporation’s debt to maintain an investment grade credit rating from each of the major credit rating agencies. If the Corporation’s debt were to fall below investment grade, the counterparties to the derivative instruments could require additional overnight collateral on derivative instruments in net liability positions. If the credit-risk-related contingent features underlying these agreements had been triggered on December 31, 2015 , the Corporation would have been required to assign an additional $1 million of collateral to its counterparties. Derivative Instruments Derivative instruments utilized by the Corporation are negotiated over-the-counter and primarily include swaps, caps and floors, forward contracts and options, each of which may relate to interest rates, energy commodity prices or foreign currency exchange rates. Swaps are agreements in which two parties periodically exchange cash payments based on specified indices applied to a specified notional amount until a stated maturity. Caps and floors are agreements which entitle the buyer to receive cash payments based on the difference between a specified reference rate or price and an agreed strike rate or price, applied to a specified notional amount until a stated maturity. Forward contracts are over-the-counter agreements to buy or sell an asset at a specified future date and price. Options are similar to forward contracts except the purchaser has the right, but not the obligation, to buy or sell the asset during a specified period or at a specified future date. Over-the-counter contracts are tailored to meet the needs of the counterparties involved and, therefore, contain a greater degree of credit risk and liquidity risk than exchange-traded contracts, which have standardized terms and readily available price information. The Corporation reduces exposure to market and liquidity risks from over-the-counter derivative instruments entered into for risk management purposes, and transactions entered into to mitigate the market risk associated with customer-initiated transactions, by conducting hedging transactions with investment grade domestic and foreign financial institutions and subjecting counterparties to credit approvals, limits and collateral monitoring procedures similar to those used in making other extensions of credit. In addition, certain derivative contracts executed bilaterally with a dealer counterparty in the over-the-counter market are cleared through a clearinghouse, whereby the clearinghouse becomes the counterparty to the transaction. The following table presents the composition of the Corporation’s derivative instruments held or issued for risk management purposes or in connection with customer-initiated and other activities at December 31, 2015 and 2014 . The table excludes commitments and warrants accounted for as derivatives. December 31, 2015 December 31, 2014 Fair Value Fair Value (in millions) Notional/ Contract Amount (a) Gross Derivative Assets Gross Derivative Liabilities Notional/ Contract Amount (a) Gross Derivative Assets Gross Derivative Liabilities Risk management purposes Derivatives designated as hedging instruments Interest rate contracts: Swaps - fair value - receive fixed/pay floating $ 2,525 $ 147 $ — $ 1,800 $ 175 $ — Derivatives used as economic hedges Foreign exchange contracts: Spot, forwards and swaps 593 3 — 508 4 — Total risk management purposes 3,118 150 — 2,308 179 — Customer-initiated and other activities Interest rate contracts: Caps and floors written 253 — — 274 — — Caps and floors purchased 253 — — 274 — — Swaps 11,722 139 92 11,780 153 102 Total interest rate contracts 12,228 139 92 12,328 153 102 Energy contracts: Caps and floors written 536 — 85 1,218 — 173 Caps and floors purchased 536 85 — 1,218 173 — Swaps 2,055 390 387 2,496 354 352 Total energy contracts 3,127 475 472 4,932 527 525 Foreign exchange contracts: Spot, forwards, options and swaps 2,291 54 46 1,994 35 34 Total customer-initiated and other activities 17,646 668 610 19,254 715 661 Total gross derivatives $ 20,764 818 610 $ 21,562 894 661 Amounts offset in the consolidated balance sheets: Netting adjustment - Offsetting derivative assets/liabilities (127 ) (127 ) (133 ) (133 ) Netting adjustment - Cash collateral received/posted (291 ) (3 ) (262 ) — Net derivatives included in the consolidated balance sheets (b) 400 480 499 528 Amounts not offset in the consolidated balance sheets: Marketable securities received/pledged under bilateral collateral agreements (137 ) (3 ) (239 ) (2 ) Net derivatives after deducting amounts not offset in the consolidated balance sheets $ 263 $ 477 $ 260 $ 526 (a) Notional or contractual amounts, which represent the extent of involvement in the derivatives market, are used to determine the contractual cash flows required in accordance with the terms of the agreement. These amounts are typically not exchanged, significantly exceed amounts subject to credit or market risk and are not reflected in the consolidated balance sheets. (b) Net derivative assets are included in “accrued income and other assets” and net derivative liabilities are included in “accrued expenses and other liabilities” on the consolidated balance sheets. Included in the fair value of net derivative assets and net derivative liabilities are credit valuation adjustments reflecting counterparty credit risk and credit risk of the Corporation. The fair value of net derivative assets included credit valuation adjustments for counterparty credit risk of $5 million at December 31, 2015 and $2 million at December 31, 2014 . Risk Management As an end-user, the Corporation employs a variety of financial instruments for risk management purposes, including cash instruments, such as investment securities, as well as derivative instruments. Activity related to these instruments is centered predominantly in the interest rate markets and mainly involves interest rate swaps. Various other types of instruments also may be used to manage exposures to market risks, including interest rate caps and floors, total return swaps, foreign exchange forward contracts and foreign exchange swap agreements. The Corporation entered into interest rate swap agreements related to medium- and long-term debt for interest rate risk management purposes. These interest rate swap agreements effectively modify the Corporation’s exposure to interest rate risk by converting fixed-rate debt to a floating rate. These agreements involve the receipt of fixed-rate interest amounts in exchange for floating-rate interest payments over the life of the agreement, without an exchange of the underlying principal amount. Risk management fair value interest rate swaps generated net interest income of $70 million and $72 million for the years ended December 31, 2015 and 2014 , respectively. The Corporation recognized $1 million of gain for the year ended December 31, 2015 and an insignificant amount of gain for the year ended December 31, 2014 in "other noninterest income" in the consolidated statements of income for the ineffective portion of risk management derivative instruments designated as fair value hedges of fixed-rate debt. Foreign exchange rate risk arises from changes in the value of certain assets and liabilities denominated in foreign currencies. The Corporation employs spot and forward contracts in addition to swap contracts to manage exposure to these and other risks. The Corporation recognized an insignificant amount of net losses for each of the years ended December 31, 2015 and December 31, 2014 on risk management derivative instruments used as economic hedges in "other noninterest income" in the consolidated statements of income. The following table summarizes the expected weighted average remaining maturity of the notional amount of risk management interest rate swaps and the weighted average interest rates associated with amounts expected to be received or paid on interest rate swap agreements as of December 31, 2015 and 2014 . Weighted Average (dollar amounts in millions) Notional Amount Remaining Maturity (in years) Receive Rate Pay Rate (a) December 31, 2015 Swaps - fair value - receive fixed/pay floating rate Medium- and long-term debt designation $ 2,525 5.1 3.89 % 1.11 % December 31, 2014 Swaps - fair value - receive fixed/pay floating rate Medium- and long-term debt designation 1,800 4.6 4.54 0.49 (a) Variable rates paid on receive fixed swaps are based on six-month LIBOR rates in effect at December 31, 2015 and 2014 . Management believes these hedging strategies achieve the desired relationship between the rate maturities of assets and funding sources which, in turn, reduce the overall exposure of net interest income to interest rate risk, although there can be no assurance that such strategies will be successful. Customer-Initiated and Other The Corporation enters into derivative transactions at the request of customers and generally takes offsetting positions with dealer counterparties to mitigate the inherent market risk. Income primarily results from the spread between the customer derivative and the offsetting dealer position. For customer-initiated foreign exchange contracts where offsetting positions have not been taken, the Corporation manages the remaining inherent market risk through individual foreign currency position limits and aggregate value-at-risk limits. These limits are established annually and reviewed quarterly. For those customer-initiated derivative contracts which were not offset or where the Corporation holds a speculative position within the limits described above, the Corporation recognized $1 million of net gains in “other noninterest income” in the consolidated statements of income for each of the years ended December 31, 2015 and 2014 . Fair values of customer-initiated and other derivative instruments represent the net unrealized gains or losses on such contracts and are recorded in the consolidated balance sheets. Changes in fair value are recognized in the consolidated statements of income. The net gains recognized in income on customer-initiated derivative instruments, net of the impact of offsetting positions, were as follows. (in millions) Years Ended December 31 Location of Gain 2015 2014 Interest rate contracts Other noninterest income $ 16 $ 20 Energy contracts Other noninterest income 2 2 Foreign exchange contracts Foreign exchange income 37 38 Total $ 55 $ 60 Credit-Related Financial Instruments The Corporation issues off-balance sheet financial instruments in connection with commercial and consumer lending activities. The Corporation’s credit risk associated with these instruments is represented by the contractual amounts indicated in the following table. (in millions) December 31 2015 2014 Unused commitments to extend credit: Commercial and other $ 26,115 $ 27,905 Bankcard, revolving check credit and home equity loan commitments 2,414 2,151 Total unused commitments to extend credit $ 28,529 $ 30,056 Standby letters of credit $ 3,985 $ 3,880 Commercial letters of credit 41 75 The Corporation maintains an allowance to cover probable credit losses inherent in lending-related commitments, including unused commitments to extend credit, letters of credit and financial guarantees. At December 31, 2015 and 2014 , the allowance for credit losses on lending-related commitments, included in “accrued expenses and other liabilities” on the consolidated balance sheets, was $45 million and $41 million , respectively. Unused Commitments to Extend Credit Commitments to extend credit are legally binding agreements to lend to a customer, provided there is no violation of any condition established in the contract. These commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. Since many commitments expire without being drawn upon, the total contractual amount of commitments does not necessarily represent future cash requirements of the Corporation. Commercial and other unused commitments are primarily variable rate commitments. The allowance for credit losses on lending-related commitments included $33 million and $30 million at December 31, 2015 and 2014 , respectively, for probable credit losses inherent in the Corporation’s unused commitments to extend credit. Standby and Commercial Letters of Credit Standby letters of credit represent conditional obligations of the Corporation which guarantee the performance of a customer to a third party. Standby letters of credit are primarily issued to support public and private borrowing arrangements, including commercial paper, bond financing and similar transactions. Commercial letters of credit are issued to finance foreign or domestic trade transactions. These contracts expire in decreasing amounts through the year 2022 . The Corporation may enter into participation arrangements with third parties that effectively reduce the maximum amount of future payments which may be required under standby and commercial letters of credit. These risk participations covered $287 million and $316 million at December 31, 2015 and 2014 , respectively, of the $4.0 billion of standby and commercial letters of credit outstanding at both December 31, 2015 and 2014 . The carrying value of the Corporation’s standby and commercial letters of credit, included in “accrued expenses and other liabilities” on the consolidated balance sheets, totaled $49 million at December 31, 2015 , including $37 million in deferred fees and $12 million in the allowance for credit losses on lending-related commitments. At December 31, 2014 , the comparable amounts were $55 million , $44 million and $11 million , respectively. The following table presents a summary of criticized standby and commercial letters of credit at December 31, 2015 and December 31, 2014 . The Corporation's criticized list is consistent with the Special mention, Substandard and Doubtful categories defined by regulatory authorities. The Corporation manages credit risk through underwriting, periodically reviewing and approving its credit exposures using Board committee approved credit policies and guidelines. (dollar amounts in millions) December 31, 2015 December 31, 2014 Total criticized standby and commercial letters of credit $ 110 $ 79 As a percentage of total outstanding standby and commercial letters of credit 2.7 % 2.0 % Other Credit-Related Financial Instruments The Corporation enters into credit risk participation agreements, under which the Corporation assumes credit exposure associated with a borrower’s performance related to certain interest rate derivative contracts. The Corporation is not a party to the interest rate derivative contracts and only enters into these credit risk participation agreements in instances in which the Corporation is also a party to the related loan participation agreement for such borrowers. The Corporation manages its credit risk on the credit risk participation agreements by monitoring the creditworthiness of the borrowers, which is based on the normal credit review process had it entered into the derivative instruments directly with the borrower. The notional amount of such credit risk participation agreement reflects the pro-rata share of the derivative instrument, consistent with its share of the related participated loan. As of December 31, 2015 and 2014 , the total notional amount of the credit risk participation agreements was approximately $559 million and $598 million , respectively, and the fair value, included in customer-initiated interest rate contracts recorded in "accrued expenses and other liabilities" on the consolidated balance sheets, was insignificant for each period. The maximum estimated exposure to these agreements, as measured by projecting a maximum value of the guaranteed derivative instruments, assuming 100 percent default by all obligors on the maximum values, was approximately $5 million and $7 million at December 31, 2015 and 2014 , respectively. In the event of default, the lead bank has the ability to liquidate the assets of the borrower, in which case the lead bank would be required to return a percentage of the recouped assets to the participating banks. As of December 31, 2015 , the weighted average remaining maturity of outstanding credit risk participation agreements was 2.4 years.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2015
Deposits [Abstract]
Deposits	DEPOSITS At December 31, 2015 , the scheduled maturities of certificates of deposit and other deposits with a stated maturity were as follows: (in millions) Years Ending December 31 2016 $ 2,792 2017 503 2018 132 2019 83 2020 51 Thereafter 23 Total $ 3,584 A maturity distribution of domestic certificates of deposit of $100,000 and over follows: (in millions) December 31 2015 2014 Three months or less $ 532 $ 822 Over three months to six months 385 456 Over six months to twelve months 659 733 Over twelve months 537 795 Total $ 2,113 $ 2,806 The aggregate amount of domestic certificates of deposit that meet or exceed the current FDIC insurance limit of $250,000 was $1.4 billion and $2.0 billion at December 31, 2015 and 2014 , respectively. All foreign office time deposits of $32 million and $135 million at December 31, 2015 and 2014 , respectively, were in denominations of $250,000 or more.

Net Income Per Common Share

Net Income Per Common Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Income Per Common Share	NET INCOME PER COMMON SHARE Basic and diluted net income per common share are presented in the following table. (in millions, except per share data) Years Ended December 31 2015 2014 2013 Basic and diluted Net income $ 521 $ 593 $ 541 Less income allocated to participating securities 6 7 8 Net income attributable to common shares $ 515 $ 586 $ 533 Basic average common shares 176 179 183 Basic net income per common share $ 2.93 $ 3.28 $ 2.92 Basic average common shares 176 179 183 Dilutive common stock equivalents: Net effect of the assumed exercise of stock options 2 2 1 Net effect of the assumed exercise of warrants 3 4 3 Diluted average common shares 181 185 187 Diluted net income per common share $ 2.84 $ 3.16 $ 2.85 The following average shares related to outstanding options to purchase shares of common stock were not included in the computation of diluted net income per common share because the prices of the options and warrants were greater than the average market price of common shares for the period. (shares in millions) Years Ended December 31 2015 2014 2013 Average outstanding options 5.1 7.2 10.8 Range of exercise prices $46.68 - $60.82 $47.24 - $61.94 $34.78 - $61.94

Variable Interest Entities (VIE

Variable Interest Entities (VIEs)	12 Months Ended
	Dec. 31, 2015
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Variable Interest Entities (VIEs)	VARIABLE INTEREST ENTITIES (VIEs) The Corporation evaluates its interest in certain entities to determine if these entities meet the definition of a VIE and whether the Corporation is the primary beneficiary and should consolidate the entity based on the variable interests it held both at inception and when there is a change in circumstances that requires a reconsideration. The Corporation holds ownership interests in funds in the form of limited partnerships or limited liability companies (LLCs) investing in affordable housing projects that qualify for the LIHTC. The Corporation also directly invests in limited partnerships and LLCs which invest in community development projects which generate similar tax credits to investors. As an investor, the Corporation obtains income tax credits and deductions from the operating losses of these tax credit entities. These tax credit entities meet the definition of a VIE; however, the Corporation is not the primary beneficiary of the entities, as the general partner or the managing member has both the power to direct the activities that most significantly impact the economic performance of the entities and the obligation to absorb losses or the right to receive benefits that could be significant to the entities. While the partnership/LLC agreements allow the limited partners/investor members, through a majority vote, to remove the general partner/managing member, this right is not deemed to be substantive as the general partner/managing member can only be removed for cause. The Corporation accounts for its interests in LIHTC entities using the proportional amortization method. Exposure to loss as a result of the Corporation’s involvement with LIHTC entities at December 31, 2015 was limited to approximately $405 million . Ownership interests in other community development projects which generate similar tax credits to investors (other tax credit entities) are accounted for under either the cost or equity method. Exposure to loss as a result of the Corporation's involvement in other tax credit entities at December 31, 2015 was limited to approximately $10 million . Investment balances, including all legally binding commitments to fund future investments, are included in “accrued income and other assets” on the consolidated balance sheets. A liability is recognized in “accrued expenses and other liabilities” on the consolidated balance sheets for all legally binding unfunded commitments to fund tax credit entities ( $143 million at December 31, 2015 ). Amortization and other write-downs of LIHTC investments are presented on a net basis as a component of the "provision for income taxes" on the consolidated statements of income, while amortization and write-downs of other tax credit investments are recorded in “other noninterest income." The income tax credits and deductions are recorded as a reduction of income tax expense and a reduction of federal income taxes payable. The Corporation provided no financial or other support that was not contractually required to any of the above VIEs during the years ended December 31, 2015 , 2014 and 2013 . The following table summarizes the impact of these tax credit entities on line items on the Corporation’s consolidated statements of income. (in millions) Years Ended December 31 2015 2014 2013 Other noninterest income: Amortization of other tax credit investments $ 1 $ (5 ) $ (1 ) Provision for income taxes: Amortization of LIHTC Investments 62 60 56 Low income housing tax credits (61 ) (59 ) (56 ) Other tax benefits related to tax credit entities (22 ) (28 ) (21 ) Total provision for income taxes $ (21 ) $ (27 ) $ (21 ) For further information on the Corporation’s consolidation policy, see Note 1.

Short-term Borrowings

Short-term Borrowings	12 Months Ended
	Dec. 31, 2015
Short-term Debt [Abstract]
Short-term Borrowings	SHORT-TERM BORROWINGS Federal funds purchased and securities sold under agreements to repurchase generally mature within one to four days from the transaction date. Other short-term borrowings, which may consist of borrowed securities and short-term notes, generally mature within one to 120 days from the transaction date. At December 31, 2015 , Comerica Bank (the Bank), a subsidiary of the Corporation, had pledged loans totaling $24 billion which provided for up to $18 billion of available collateralized borrowing with the FRB. The following table provides a summary of short-term borrowings. (dollar amounts in millions) Federal Funds Purchased and Securities Sold Under Agreements to Repurchase December 31, 2015 Amount outstanding at year-end $ 23 Weighted average interest rate at year-end 0.38 % Maximum month-end balance during the year $ 109 Average balance outstanding during the year 93 Weighted average interest rate during the year 0.05 % December 31, 2014 Amount outstanding at year-end $ 116 Weighted average interest rate at year-end 0.04 % Maximum month-end balance during the year $ 238 Average balance outstanding during the year 200 Weighted average interest rate during the year 0.04 % December 31, 2013 Amount outstanding at year-end $ 253 Weighted average interest rate at year-end 0.05 % Maximum month-end balance during the year $ 277 Average balance outstanding during the year 211 Weighted average interest rate during the year 0.07 %

Medium- And Long-Term Debt

Medium- And Long-Term Debt	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Medium- And Long-Term Debt	MEDIUM- AND LONG-TERM DEBT Medium- and long-term debt is summarized as follows: (in millions) December 31 2015 2014 Parent company Subordinated notes: 4.80% subordinated notes due 2015 (a) $ — $ 304 3.80% subordinated notes due 2026 (a) 259 257 Medium-term notes: 3.00% notes due 2015 — 300 2.125% notes due 2019 (a) 349 347 Total parent company 608 1,208 Subsidiaries Subordinated notes: 5.75% subordinated notes due 2016 (a) (b) 659 670 5.20% subordinated notes due 2017 (a) 530 548 4.00% subordinated notes due 2025 (a) 351 — 7.875% subordinated notes due 2026 (a) 223 227 Total subordinated notes 1,763 1,445 Medium-term notes: 2.50% notes due 2020 (a) 671 — Other notes: 6.0% - 6.4% fixed-rate notes due 2015 to 2020 16 22 Total subsidiaries 2,450 1,467 Total medium- and long-term debt $ 3,058 $ 2,675 (a) The fixed interest rates on these notes have been swapped to a variable rate and designated in a hedging relationship. Accordingly, carrying value has been adjusted to reflect the change in the fair value of the debt as a result of changes in the benchmark rate. (b) The fixed interest rate on $250 million of $600 million total par value of these notes have been swapped to a variable rate. Subordinated notes with remaining maturities greater than one year qualify as Tier 2 capital. In 2015, the Corporation early adopted accounting guidance that amended the presentation of debt issuance costs in the balance sheet as a direct deduction from the carrying amount of the related debt liability rather than as a deferred charge. The new guidance was retrospectively applied, which resulted in a decrease of $4 million to both "accrued income and other assets" and "medium- and long-term debt" on the consolidated balance sheets as of December 31, 2014. At December 31, 2015 , unamortized debt issuance costs deducted from the carrying amount of medium- and long-term debt totaled $8 million . The Bank is a member of the FHLB, which provides short- and long-term funding to its members through advances collateralized by real-estate related assets. Actual borrowing capacity is contingent upon the amount of collateral available to be pledged to the FHLB. At December 31, 2015 , $14 billion of real estate-related loans were pledged to the FHLB as blanket collateral for potential future borrowings of approximately $6 billion . At December 31, 2015 , the principal maturities of medium- and long-term debt were as follows: (in millions) Years Ending December 31 2016 $ 650 2017 500 2018 2 2019 357 2020 682 Thereafter 750 Total $ 2,941

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Stockholders' Equity	SHAREHOLDERS’ EQUITY The Federal Reserve completed its 2015 Comprehensive Capital Analysis and Review (CCAR) of the Corporation's 2015-2016 capital plan in March 2015 and did not object to the capital distributions contemplated in the plan. The capital plan provides for up to $393 million of equity repurchases for the five-quarter period ending June 30, 2016. During the year ended December 31, 2015 , the Corporation had repurchased $242 million under the equity repurchase program. Repurchases of common stock under the equity repurchase program authorized in 2010 by the Board of Directors of the Corporation totaled 5.1 million shares at an average price paid of $45.65 per share in 2015 , 5.2 million shares at an average price paid of $47.91 per share in 2014 and 7.4 million shares at an average price paid of $38.63 per share in 2013 . The Corporation also repurchased 500 thousand warrants at an average price paid of $20.70 in 2015 . There is no expiration date for the Corporation's equity repurchase program. At December 31, 2015 , the Corporation had 9.5 million warrants outstanding to purchase 8.5 million common shares at a weighted-average exercise price of $29.43 . Outstanding warrants were exercisable at the date of grant and expire in 2018 . Approximately 934 thousand and 361 thousand shares of common stock were issued upon exercise of warrants in 2015 and 2014 , respectively. There were no warrant exercises in 2013 . At December 31, 2015 , the Corporation had 8.5 million shares of common stock reserved for warrant exercises, 12.7 million shares of common stock reserved for stock option exercises and restricted stock unit vesting and 1.9 million shares of restricted stock outstanding to employees and directors under share-based compensation plans.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	ACCUMULATED OTHER COMPREHENSIVE LOSS The following table presents a reconciliation of the changes in the components of accumulated other comprehensive loss and details the components of other comprehensive income (loss) for the years ended December 31, 2015 , 2014 and 2013 , including the amount of income tax expense (benefit) allocated to each component of other comprehensive income (loss). (in millions) Years Ended December 31 2015 2014 2013 Accumulated net unrealized gains (losses) on investment securities: Balance at beginning of period, net of tax $ 37 $ (68 ) $ 150 Net unrealized holding (losses) gains arising during the period (55 ) 166 (343 ) Less: (Benefit) provision for income taxes (21 ) 60 (126 ) Net unrealized holding (losses) gains arising during the period, net of tax (34 ) 106 (217 ) Less: Net realized (losses) gains included in net securities (losses) gains (2 ) 1 1 Less: Benefit for income taxes (1 ) — — Reclassification adjustment for net securities (losses) gains included in net income, net of tax (1 ) 1 1 Less: Net losses realized as a yield adjustment in interest on investment securities (8 ) — — Less: Benefit for income taxes (3 ) — — Reclassification adjustment for net losses realized as a yield adjustment included in net income, net of tax (5 ) — — Change in net unrealized (losses) gains on investment securities, net of tax (28 ) 105 (218 ) Balance at end of period, net of tax $ 9 $ 37 $ (68 ) Accumulated defined benefit pension and other postretirement plans adjustment: Balance at beginning of period, net of tax $ (449 ) $ (323 ) $ (563 ) Actuarial (loss) gain arising during the period (57 ) (240 ) 286 Prior service credit arising during the period 3 — — Net defined benefit pension and other postretirement adjustment arising during the period (54 ) (240 ) 286 Less: (Benefit) provision for income taxes (19 ) (87 ) 103 Net defined benefit pension and other postretirement adjustment arising during the period, net of tax (35 ) (153 ) 183 Amounts recognized in salaries and benefits expense: Amortization of actuarial net loss 70 39 89 Amortization of prior service cost 1 3 2 Total amounts recognized in salaries and benefits expense 71 42 91 Less: Benefit for income taxes 25 15 34 Adjustment for amounts recognized as components of net periodic benefit cost during the period, net of tax 46 27 57 Change in defined benefit pension and other postretirement plans adjustment, net of tax 11 (126 ) 240 Balance at end of period, net of tax $ (438 ) $ (449 ) $ (323 ) Total accumulated other comprehensive loss at end of period, net of tax $ (429 ) $ (412 ) $ (391 )

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2015
Share-based Compensation [Abstract]
Share-based Compensation	SHARE-BASED COMPENSATION Share-based compensation expense is charged to “salaries and benefits” expense on the consolidated statements of income. The components of share-based compensation expense for all share-based compensation plans and related tax benefits are as follows. (in millions) Years Ended December 31 2015 2014 2013 Total share-based compensation expense $ 38 $ 38 $ 35 Related tax benefits recognized in net income $ 14 $ 14 $ 13 The following table summarizes unrecognized compensation expense for all share-based plans: (dollar amounts in millions) December 31, 2015 Total unrecognized share-based compensation expense $ 49 Weighted-average expected recognition period (in years) 2.8 The Corporation has share-based compensation plans under which it awards shares of restricted stock and restricted stock units to executive officers, directors and key personnel, and stock options to executive officers and key personnel of the Corporation and its subsidiaries. Restricted stock vests over periods ranging from three years to five years, restricted stock units vest over periods ranging from one year to three years, and stock options vest over periods ranging from one year to four years. The maturity of each option is determined at the date of grant; however, no options may be exercised later than ten years from the date of grant. The options may have restrictions regarding exercisability. The plans originally provided for a grant of up to 19.4 million common shares, plus shares under certain plans that are forfeited, expire or are canceled, which become available for re-grant. At December 31, 2015 , 9.8 million shares were available for grant. The Corporation used a binomial model to value stock options granted in the periods presented. Option valuation models require several inputs, including the expected stock price volatility, and changes in input assumptions can materially affect the fair value estimates. The model used may not necessarily provide a reliable single measure of the fair value of employee and director stock options. The risk-free interest rate assumption used in the binomial option-pricing model as outlined in the table below was based on the federal ten-year treasury interest rate. The expected dividend yield was based on the historical and projected dividend yield patterns of the Corporation’s common shares. Expected volatility assumptions considered both the historical volatility of the Corporation’s common stock over a ten-year period and implied volatility based on actively traded options on the Corporation’s common stock with pricing terms and trade dates similar to the stock options granted. The estimated weighted-average grant-date fair value per option and the underlying binomial option-pricing model assumptions are summarized in the following table: Years Ended December 31 2015 2014 2013 Weighted-average grant-date fair value per option $ 11.31 $ 13.21 $ 9.07 Weighted-average assumptions: Risk-free interest rates 1.83 % 2.95 % 1.94 % Expected dividend yield 3.00 3.00 3.00 Expected volatility factors of the market price of Comerica common stock 33 31 34 Expected option life (in years) 6.9 5.8 6.4 A summary of the Corporation’s stock option activity and related information for the year ended December 31, 2015 follows: Weighted-Average Number of Options (in thousands) Exercise Price per Share Remaining Contractual Term (in years) Aggregate Intrinsic Value (in millions) Outstanding-January 1, 2015 14,003 $ 44.28 Granted 1,035 42.32 Forfeited or expired (2,405 ) 53.88 Exercised (841 ) 33.46 Outstanding-December 31, 2015 11,792 42.92 4.1 $ 53 Outstanding, net of expected forfeitures-December 31, 2014 11,520 43.04 4.0 52 Exercisable-December 31, 2015 9,146 43.70 3.0 43 The aggregate intrinsic value of outstanding options shown in the table above represents the total pretax intrinsic value at December 31, 2015 , based on the Corporation’s closing stock price of $41.83 at December 31, 2015 . The total intrinsic value of stock options exercised was $12 million , $23 million and $14 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. A summary of the Corporation’s restricted stock activity and related information for the year ended December 31, 2015 follows: Number of Shares (in thousands) Weighted-Average Grant-Date Fair Value per Share Outstanding-January 1, 2015 2,140 $ 35.38 Granted 413 42.45 Forfeited (106 ) 37.02 Vested (537 ) 33.29 Outstanding-December 31, 2015 1,910 $ 37.41 The total fair value of restricted stock awards that fully vested was $18 million for the years ended both December 31, 2015 and 2014 and $10 million for the year ended December 31, 2013 . A summary of the Corporation's restricted stock unit activity and related information for the year ended December 31, 2015 follows: Service-Based Units Performance-Based Units Number of Units (in thousands) Weighted-Average Grant-Date Fair Value per Share Number of Units (in thousands) Weighted-Average Grant-Date Fair Value per Share Outstanding-January 1, 2015 387 $ 34.58 319 $ 45.44 Granted 18 46.83 266 42.32 Converted 41 33.79 (41 ) 33.79 Forfeited (33 ) 37.78 (34 ) 43.27 Outstanding-December 31, 2015 413 34.77 510 44.89 The Corporation expects to satisfy the exercise of stock options, the vesting of restricted stock units and future grants of restricted stock by issuing shares of common stock out of treasury. At December 31, 2015 , the Corporation held 52.5 million shares in treasury. For further information on the Corporation’s share-based compensation plans, refer to Note 1 .

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Employee Benefit Plans	EMPLOYEE BENEFIT PLANS Defined Benefit Pension and Postretirement Benefit Plans The Corporation has a qualified and a non-qualified defined benefit pension plan, which together provide benefits for substantially all full-time employees hired before January 1, 2007 who continue to meet the eligibility requirements of the plans. Salaries and benefits expense included defined benefit pension expense of $47 million , $39 million and $86 million in the years ended December 31, 2015 , 2014 and 2013 , respectively, for the plans. Benefits under the defined benefit plans are based primarily on years of service, age and compensation during the five highest paid consecutive calendar years occurring during the last ten years before retirement. The Corporation’s postretirement benefit plan continues to provide postretirement health care and life insurance benefits for retirees as of December 31, 1992. The plan also provides certain postretirement health care and life insurance benefits for a limited number of retirees who retired prior to January 1, 2000. For all other employees hired prior to January 1, 2000, a nominal benefit is provided. Employees hired on or after January 1, 2000 and prior to January 1, 2007 are eligible to participate in the plan on a full contributory basis until Medicare-eligible. Employees hired on or after January 1, 2007 are not eligible to participate in the plan. The Corporation funds the pre-1992 retiree plan benefits with bank-owned life insurance. Employee benefits expense included postretirement benefit expense of $1 million in each of the years ended December 31, 2015 and December 31, 2014 , and $2 million in the year ended December 31, 2013 . The following table sets forth reconciliations of plan assets and the projected benefit obligation, the weighted-average assumptions used to determine year-end benefit obligations, and the amounts recognized in accumulated other comprehensive income (loss) for the Corporation’s defined benefit pension plans and postretirement benefit plan at December 31, 2015 and 2014 . The Corporation used a measurement date of December 31, 2015 for these plans. Defined Benefit Pension Plans Qualified Non-Qualified Postretirement Benefit Plan (dollar amounts in millions) 2015 2014 2015 2014 2015 2014 Change in fair value of plan assets: Fair value of plan assets at January 1 $ 2,541 $ 2,035 $ — $ — $ 67 $ 67 Actual return on plan assets (73 ) 278 — — — 3 Employer contributions — 350 — — — 2 Benefits paid (122 ) (a) (122 ) (a) — — (6 ) (5 ) Fair value of plan assets at December 31 $ 2,346 $ 2,541 $ — $ — $ 61 $ 67 Change in projected benefit obligation: Projected benefit obligation at January 1 $ 2,070 $ 1,731 $ 235 $ 195 $ 73 $ 69 Service cost 35 29 4 3 — — Interest cost 88 88 10 10 3 3 Actuarial (gain) loss (155 ) 344 (16 ) 37 (8 ) 6 Benefits paid (122 ) (a) (122 ) (a) (11 ) (10 ) (6 ) (5 ) Plan amendment — — — — (3 ) — Projected benefit obligation at December 31 $ 1,916 $ 2,070 $ 222 $ 235 $ 59 $ 73 Accumulated benefit obligation $ 1,756 $ 1,905 $ 191 $ 203 $ 59 $ 73 Funded status at December 31 (b) (c) $ 430 $ 471 $ (222 ) $ (235 ) $ 2 $ (6 ) Weighted-average assumptions used: Discount rate 4.82 % 4.28 % 4.82 % 4.28 % 4.53 % 3.99 % Rate of compensation increase 3.75 3.75 3.75 3.75 n/a n/a Healthcare cost trend rate: Cost trend rate assumed for next year n/a n/a n/a n/a 7.00 7.00 Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) n/a n/a n/a n/a 5.00 5.00 Year when rate reaches the ultimate trend rate n/a n/a n/a n/a 2027 2026 Amounts recognized in accumulated other comprehensive income (loss) before income taxes: Net actuarial loss $ (586 ) $ (568 ) $ (78 ) $ (104 ) $ (22 ) $ (27 ) Prior service (cost) credit (21 ) (25 ) 21 25 1 (3 ) Balance at December 31 $ (607 ) $ (593 ) $ (57 ) $ (79 ) $ (21 ) $ (30 ) (a) Included $56 million and $63 million in benefit payments made to certain terminated vested eligible participants who elected to receive lump-sum settlements in 2015 and 2014, respectively. (b) Based on projected benefit obligation for defined benefit pension plans and accumulated benefit obligation for postretirement benefit plan. (c) The Corporation recognizes the overfunded and underfunded status of the plans in “accrued income and other assets” and “accrued expenses and other liabilities,” respectively, on the consolidated balance sheets. n/a - not applicable The accumulated benefit obligation exceeded the fair value of plan assets for the non-qualified defined benefit pension plan at December 31, 2015 and December 31, 2014 . The accumulated benefit obligation exceeded the fair value of plan assets for the postretirement benefit plan at December 31, 2014 . The following table details the changes in plan assets and benefit obligations recognized in other comprehensive income (loss) for the year ended December 31, 2015 . Defined Benefit Pension Plans (in millions) Qualified Non-Qualified Postretirement Benefit Plan Total Actuarial (loss) gain arising during the period $ (77 ) $ 16 $ 4 $ (57 ) Prior service credit arising during the period — — 3 3 Amortization of net actuarial loss 59 10 1 70 Amortization of prior service cost (credit) 4 (4 ) 1 1 Total recognized in other comprehensive income (loss) $ (14 ) $ 22 $ 9 $ 17 Components of net periodic defined benefit cost and postretirement benefit cost, the actual return on plan assets and the weighted-average assumptions used were as follows. Defined Benefit Pension Plans (dollar amounts in millions) Qualified Non-Qualified Years Ended December 31 2015 2014 2013 2015 2014 2013 Service cost $ 35 $ 29 $ 37 $ 4 $ 3 $ 4 Interest cost 88 88 80 10 10 9 Expected return on plan assets (159 ) (131 ) (132 ) — — — Amortization of prior service cost (credit) 4 6 7 (4 ) (4 ) (6 ) Amortization of net loss 59 31 76 10 7 11 Net periodic defined benefit cost $ 27 $ 23 $ 68 $ 20 $ 16 $ 18 Actual return on plan assets $ (73 ) $ 278 $ 136 n/a n/a n/a Actual rate of return on plan assets (2.95 )% 13.88 % 7.05 % n/a n/a n/a Weighted-average assumptions used: Discount rate 4.28 % 5.17 % 4.20 % 4.28 % 5.17 % 4.20 % Expected long-term return on plan assets 6.75 6.75 7.25 n/a n/a n/a Rate of compensation increase 3.75 4.00 4.00 3.75 4.00 4.00 n/a - not applicable (dollar amounts in millions) Postretirement Benefit Plan Years Ended December 31 2015 2014 2013 Interest cost $ 3 $ 3 $ 3 Expected return on plan assets (4 ) (4 ) (4 ) Amortization of prior service cost 1 1 1 Amortization of net loss 1 1 2 Net periodic postretirement benefit cost $ 1 $ 1 $ 2 Actual return on plan assets $ — $ 3 $ (2 ) Actual rate of return on plan assets (0.53 )% 4.62 % (2.29 )% Weighted-average assumptions used: Discount rate 3.99 % 4.59 % 3.81 % Expected long-term return on plan assets 5.00 5.00 5.00 Healthcare cost trend rate: Cost trend rate assumed 7.00 7.50 8.00 Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 5.00 5.00 5.00 Year that the rate reaches the ultimate trend rate 2026 2033 2033 The expected long-term rate of return of plan assets is the average rate of return expected to be realized on funds invested or expected to be invested over the life of the plan, which has an estimated average life of approximately 15 years as of December 31, 2015 . The expected long-term rate of return on plan assets is set after considering both long-term returns in the general market and long-term returns experienced by the assets in the plan. The returns on the various asset categories are blended to derive one long-term rate of return. The Corporation reviews its pension plan assumptions on an annual basis with its actuarial consultants to determine if assumptions are reasonable and adjusts the assumptions to reflect changes in future expectations. The estimated portion of balances remaining in accumulated other comprehensive income (loss) that are expected to be recognized as a component of net periodic benefit cost in the year ended December 31, 2016 are as follows. Defined Benefit Pension Plans (in millions) Qualified Non-Qualified Postretirement Benefit Plan Total Net loss $ 30 $ 7 $ 1 $ 38 Prior service cost (credit) 4 (4 ) — — Assumed healthcare cost trend rates have a significant effect on the amounts reported for the postretirement benefit plan. A one-percentage-point change in 2015 assumed healthcare and prescription drug cost trend rates would have the following effects. One-Percentage-Point (in millions) Increase Decrease Effect on postretirement benefit obligation $ 4 $ (3 ) Effect on total service and interest cost — — Plan Assets The Corporation’s overall investment goals for the qualified defined benefit pension plan are to maintain a portfolio of assets of appropriate liquidity and diversification; to generate investment returns (net of operating costs) that are reasonably anticipated to maintain the plan’s fully funded status or to reduce a funding deficit, after taking into account various factors, including reasonably anticipated future contributions and expense and the interest rate sensitivity of the plan’s assets relative to that of the plan’s liabilities; and to generate investment returns (net of operating costs) that meet or exceed a customized benchmark as defined in the plan investment policy. Derivative instruments are permissible for hedging and transactional efficiency, but only to the extent that the derivative use enhances the efficient execution of the plan’s investment policy. The plan does not directly invest in securities issued by the Corporation and its subsidiaries. The Corporation’s target allocations for plan investments are 36 percent to 56 percent equity securities and 44 percent to 64 percent fixed income, including cash. Equity securities include collective investment and mutual funds and common stock. Fixed income securities include U.S. Treasury and other U.S. government agency securities, mortgage-backed securities, corporate bonds and notes, municipal bonds, collateralized mortgage obligations and money market funds. Fair Value Measurements The Corporation’s qualified defined benefit pension plan utilizes fair value measurements to record fair value adjustments and to determine fair value disclosures. The Corporation’s qualified benefit pension plan categorizes investments recorded at fair value into a three-level hierarchy, based on the markets in which the investment are traded and the reliability of the assumptions used to determine fair value. Refer to Note 1 for a description of the three-level hierarchy. Following is a description of the valuation methodologies and key inputs used to measure the fair value of the Corporation’s qualified defined benefit pension plan investments, including an indication of the level of the fair value hierarchy in which the investments are classified. Collective investment funds Fair value measurement is based upon the net asset value (NAV) provided by the administrator of the fund. Collective investment fund NAVs are based primarily on observable inputs, generally the quoted prices for underlying assets owned by the fund, and are included in Level 2 of the fair value hierarchy. Mutual funds Fair value measurement is based upon the NAV provided by the administrator of the fund. Mutual fund NAVs are quoted in an active market exchange, such as the New York Stock Exchange, and are included in Level 1 of the fair value hierarchy. Common stock Fair value measurement is based upon the closing price quoted in an active market exchange, such as the New York Stock Exchange. Level 1 common stock includes domestic and foreign stock and real estate investment trusts. U.S. Treasury and other U.S. government agency securities Fair value measurement is based upon quoted prices in an active market exchange, such as the New York Stock Exchange. Level 1 securities include U.S. Treasury securities that are traded by dealers or brokers in active over-the-counter markets. Corporate and municipal bonds and notes Fair value measurement is based upon quoted prices of securities with similar characteristics or pricing models based on observable market data inputs, primarily interest rates, spreads and prepayment information. Level 2 securities include corporate bonds, municipal bonds, foreign bonds and foreign notes. Collateralized mortgage obligations, U.S. government agency mortgage-backed securities and TBA mortgage-backed securities Fair value measurement is based upon independent pricing models or other model-based valuation techniques such as the present value of future cash flows, adjusted for the security's credit rating, prepayment assumptions and other factors, such as credit loss and liquidity assumptions, and are included in Level 2 of the fair value hierarchy. Private placements Fair value is measured using the NAV provided by fund management as quoted prices in active markets are not available. Management considers additional discounts to the provided NAV for market and credit risk. Private placements are included in Level 3 of the fair value hierarchy. Fair Values The fair values of the Corporation’s qualified defined benefit pension plan investments measured at fair value on a recurring basis at December 31, 2015 and 2014 , by asset category and level within the fair value hierarchy, are detailed in the table below. (in millions) Total Level 1 Level 2 Level 3 December 31, 2015 Cash equivalent securities: Mutual funds $ 43 $ 43 $ — $ — Equity securities: Collective investment funds 527 — 527 — Mutual funds 69 69 — — Common stock 480 478 2 — Fixed income securities: U.S. Treasury and other U.S. government agency securities 356 356 — — Corporate and municipal bonds and notes 729 — 729 — Collateralized mortgage obligations 18 — 18 — U.S. government agency mortgage-backed securities 8 — 8 — Private placements 105 — — 105 Other assets: TBA mortgage-backed securities 12 — 12 — Total investments at fair value $ 2,347 $ 946 $ 1,296 $ 105 December 31, 2014 Cash equivalent securities: Mutual funds $ 390 $ 390 $ — $ — Equity securities: Collective investment funds 466 — 466 — Mutual funds 76 76 — — Common stock 499 499 — — Fixed income securities: U.S. Treasury and other U.S. government agency securities 359 359 — — Corporate and municipal bonds and notes 659 — 659 — Collateralized mortgage obligations 9 — 9 — Private placements 73 — 73 Total investments at fair value $ 2,531 $ 1,324 $ 1,134 $ 73 The table below provides a summary of changes in the Corporation’s qualified defined benefit pension plan’s Level 3 investments measured at fair value on a recurring basis for the years ended December 31, 2015 and 2014 . Balance at Beginning of Period Balance at End of Period Net Gains (Losses) (in millions) Realized Unrealized Purchases Sales Year Ended December 31, 2015 Private placements $ 73 $ — $ (5 ) $ 108 $ (71 ) $ 105 Year Ended December 31, 2014 Private placements $ 36 $ 1 $ 4 $ 60 $ (28 ) $ 73 There were no assets in the non-qualified defined benefit pension plan at December 31, 2015 and 2014 . The postretirement benefit plan is fully invested in bank-owned life insurance policies. The fair value of bank-owned life insurance policies is based on the cash surrender values of the policies as reported by the insurance companies and is classified in Level 2 of the fair value hierarchy. Cash Flows The Corporation currently expects to make no employer contributions to the qualified and non-qualified defined benefit pension plans and postretirement benefit plan for the year ended December 31, 2016 . Estimated Future Benefit Payments (in millions) Years Ended December 31 Qualified Defined Benefit Pension Plan Non-Qualified Defined Benefit Pension Plan Postretirement Benefit Plan (a) 2016 $ 72 $ 11 $ 6 2017 77 12 6 2018 83 12 6 2019 89 13 6 2020 94 13 6 2021 - 2025 550 70 24 (a) Estimated benefit payments in the postretirement benefit plan are net of estimated Medicare subsidies. Defined Contribution Plans Substantially all of the Corporation’s employees are eligible to participate in the Corporation’s principal defined contribution plan (a 401(k) plan). Under this plan, the Corporation makes core matching cash contributions of 100 percent of the first 4 percent of qualified earnings contributed by employees (up to the current IRS compensation limit), invested based on employee investment elections. Employee benefits expense included expense for the plan of $22 million for each of the years ended December 31, 2015 and December 31, 2014 , and $21 million for the year ended December 31, 2013 . The Corporation also provides a profit sharing plan for the benefit of substantially all employees who work at least 1,000 hours in a plan year and are not accruing a benefit in the defined benefit pension plan. Under the profit sharing plan, the Corporation makes an annual discretionary allocation to the individual account of each eligible employee ranging from 3 percent to 8 percent of annual compensation, determined based on combined age and years of service. The allocations are invested based on employee investment elections. The employee fully vests in the defined contribution pension plan after three years of service, at age 65 if still employed, or in the event of death while an employee. Before an employee is eligible to participate, the plan requires the equivalent of one year of service. The Corporation recognized $10 million in employee benefits expense for this plan for each of the years ended December 31, 2015 and December 31, 2014 , and $7 million for the year ended December 31, 2013 . Deferred Compensation Plans The Corporation offers optional deferred compensation plans under which certain employees may make an irrevocable election to defer incentive compensation and/or a portion of base salary until retirement or separation from the Corporation. The employee may direct deferred compensation into one or more deemed investment options. Although not required to do so, the Corporation invests actual funds into the deemed investments as directed by employees, resulting in a deferred compensation asset, recorded in “other short-term investments” on the consolidated balance sheets that offsets the liability to employees under the plan, recorded in “accrued expenses and other liabilities.” The earnings from the deferred compensation asset are recorded in “interest on short-term investments” and “other noninterest income” and the related change in the liability to employees under the plan is recorded in “salaries” expense on the consolidated statements of income.

Income Taxes And Tax-Related It

Income Taxes And Tax-Related Items	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes and Tax-Related Items	INCOME TAXES AND TAX-RELATED ITEMS The provision for income taxes is calculated as the sum of income taxes due for the current year and deferred taxes. Income taxes due for the current year is computed by applying federal and state tax statutes to current year taxable income. Deferred taxes arise from temporary differences between the income tax basis and financial accounting basis of assets and liabilities. Tax-related interest and penalties and foreign taxes are then added to the tax provision. The current and deferred components of the provision for income taxes were as follows: (in millions) December 31 2015 2014 2013 Current: Federal $ 275 $ 127 $ 242 Foreign 5 6 6 State and local 20 14 17 Total current 300 147 265 Deferred: Federal (68 ) 123 (20 ) State and local (3 ) 7 — Total deferred (71 ) 130 (20 ) Total $ 229 $ 277 $ 245 Income before income taxes of $750 million for the year ended December 31, 2015 included $34 million of foreign-source income. The income tax provision on securities transactions for the year ended December 31, 2015 was a benefit of $1 million and there was no tax provision on securities transactions for the years ended December 31, 2014 and December 31, 2013 . The provision for income taxes does not reflect the tax effects of unrealized gains and losses on investment securities available-for-sale or the change in defined benefit pension and other postretirement plans adjustment included in accumulated other comprehensive loss. Refer to Note 14 for additional information on accumulated other comprehensive loss. The income tax effects of transactions under the Corporation's share-based compensation plans reduced both shareholders’ equity and deferred tax assets by $12 million , $11 million and $5 million in 2015 , 2014 , and 2013 respectively. A reconciliation of expected income tax expense at the federal statutory rate to the Corporation’s provision for income taxes and effective tax rate follows: (dollar amounts in millions) 2015 2014 2013 Years Ended December 31 Amount Rate Amount Rate Amount Rate Tax based on federal statutory rate $ 262 35.0 % $ 305 35.0 % $ 275 35.0 % State income taxes 10 1.3 13 1.5 11 1.4 Affordable housing and historic credits (22 ) (2.9 ) (24 ) (2.8 ) (21 ) (2.6 ) Bank-owned life insurance (15 ) (2.0 ) (15 ) (1.7 ) (15 ) (1.9 ) Other changes in unrecognized tax benefits — — 2 0.2 (2 ) (0.2 ) Lease termination transactions (5 ) (0.7 ) — — — — Tax-related interest and penalties 1 0.1 (3 ) (0.3 ) (1 ) (0.1 ) Other (2 ) (0.3 ) (1 ) (0.1 ) (2 ) (0.4 ) Provision for income taxes $ 229 30.5 % $ 277 31.8 % $ 245 31.2 % The liability for tax-related interest and penalties included in “accrued expenses and other liabilities” on the consolidated balance sheets was $3 million and $2 million at December 31, 2015 and 2014 , respectively. In the ordinary course of business, the Corporation enters into certain transactions that have tax consequences. From time to time, the Internal Revenue Service (IRS) may review and/or challenge specific interpretive tax positions taken by the Corporation with respect to those transactions. The Corporation believes that its tax returns were filed based upon applicable statutes, regulations and case law in effect at the time of the transactions. The IRS, an administrative authority or a court, if presented with the transactions, could disagree with the Corporation’s interpretation of the tax law. A reconciliation of the beginning and ending amount of net unrecognized tax benefits follows: (in millions) 2015 2014 2013 Balance at January 1 $ 14 $ 11 $ 42 Increases as a result of tax positions taken during a prior period 8 3 — Decrease related to settlements with tax authorities — — (31 ) Balance at December 31 $ 22 $ 14 $ 11 The Corporation anticipates that it is reasonably possible that settlements with tax authorities will result in an $8 million decrease in net unrecognized tax benefits within the next twelve months. After consideration of the effect of the federal tax benefit available on unrecognized state tax benefits, the total amount of unrecognized tax benefits that, if recognized, would affect the Corporation’s effective tax rate was approximately $4 million at December 31, 2015 and $2 million at December 31, 2014 . The following tax years for significant jurisdictions remain subject to examination as of December 31, 2015 : Jurisdiction Tax Years Federal 2010-2014 California 2003-2014 Based on current knowledge and probability assessment of various potential outcomes, the Corporation believes that current tax reserves are adequate, and the amount of any potential incremental liability arising is not expected to have a material adverse effect on the Corporation’s consolidated financial condition or results of operations. Probabilities and outcomes are reviewed as events unfold, and adjustments to the reserves are made when necessary. The principal components of deferred tax assets and liabilities were as follows: (in millions) December 31 2015 2014 Deferred tax assets: Allowance for loan losses $ 223 $ 208 Deferred compensation 113 123 Loan purchase accounting adjustments 2 5 Deferred loan origination fees and costs 24 28 Other temporary differences, net 67 44 Total deferred tax asset before valuation allowance 429 408 Valuation allowance (3 ) — Total deferred tax assets 426 408 Deferred tax liabilities: Lease financing transactions (183 ) (206 ) Defined benefit plans (32 ) (38 ) Net unrealized gains on investment securities available-for-sale (5 ) (21 ) Allowance for depreciation (7 ) (13 ) Total deferred tax liabilities (227 ) (278 ) Net deferred tax asset $ 199 $ 130 Included in deferred tax assets at December 31, 2015 were $5 million of state net operating loss carryforwards, which expire between 2016 and 2026 . The Corporation believes it is more likely than not that the benefit from certain of these state net operating loss carryforwards will not be realized and, accordingly, established a valuation allowance of $3 million at December 31, 2015 . There was no valuation allowance on deferred tax assets at December 31, 2014 . The determination regarding valuation allowances was based on available evidence of loss carryback capacity, projected future reversals of existing taxable temporary differences and assumptions made regarding future events. For further information on the Corporation’s valuation policy for deferred tax assets, refer to Note 1 .

Transactions with Related Parti

Transactions with Related Parties	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Transactions with Related Parties	TRANSACTIONS WITH RELATED PARTIES The Corporation’s banking subsidiaries had, and expect to have in the future, transactions with the Corporation’s directors and executive officers, companies with which these individuals are associated, and certain related individuals. Such transactions were made in the ordinary course of business and included extensions of credit, leases and professional services. With respect to extensions of credit, all were made on substantially the same terms, including interest rates and collateral, as those prevailing at the same time for comparable transactions with other customers and did not, in management’s opinion, involve more than normal risk of collectibility or present other unfavorable features. The aggregate amount of loans attributable to persons who were related parties at December 31, 2015 , totaled $79 million at the beginning of 2015 and $121 million at the end of 2015 . During 2015 , new loans to related parties aggregated $453 million and repayments totaled $411 million .

Regulatory Capital and Reserve

Regulatory Capital and Reserve Requirements	12 Months Ended
	Dec. 31, 2015
Regulatory Capital Requirements [Abstract]
Regulatory Capital and Reserve Requirements	REGULATORY CAPITAL AND RESERVE REQUIREMENTS Reserves required to be maintained and/or deposited with the FRB are classified in interest-bearing deposits with banks. These reserve balances vary, depending on the level of customer deposits in the Corporation’s banking subsidiaries. The average required reserve balances were $473 million and $430 million for the years ended December 31, 2015 and 2014 , respectively. Banking regulations limit the transfer of assets in the form of dividends, loans or advances from the bank subsidiaries to the parent company. Under the most restrictive of these regulations, the aggregate amount of dividends which can be paid to the parent company, with prior approval from bank regulatory agencies, approximated $398 million at January 1, 2016 , plus 2016 net profits. Substantially all the assets of the Corporation’s banking subsidiaries are restricted from transfer to the parent company of the Corporation in the form of loans or advances. The Corporation’s subsidiary banks declared dividends of $437 million , $380 million and $480 million in 2015 , 2014 and 2013 , respectively. The Corporation and its U.S. banking subsidiaries are subject to various regulatory capital requirements administered by federal and state banking agencies. The U.S. adoption of the Basel III regulatory capital framework (Basel III) became effective for the Corporation on January 1, 2015; December 31, 2014 data is based on Basel I rules. Basel III sets forth two comprehensive methodologies for calculating risk-weighted assets (RWA), a standardized approach and an advanced approach. The Corporation and its U.S. banking subsidiaries are subject to the standardized approach under the rules. Under the standardized approach, RWA is generally based on supervisory risk-weightings which vary by counterparty type and asset class. Under the Basel III standardized approach, capital is required for credit risk RWA, to cover the risk of unexpected losses due to failure of a customer or counterparty to meet its financial obligations in accordance with contractual terms; and if trading assets and liabilities exceed certain thresholds, capital is also required for market risk RWA, to cover the risk of losses due to adverse market movements or from position-specific factors. Under Basel III, there are three categories of risk-based capital: CET1 capital, Tier 1 capital and Tier 2 capital. CET1 capital predominantly includes common shareholders' equity, less certain deductions for goodwill, intangible assets and deferred tax assets that arise from net operating losses and tax credit carry-forwards. Additionally, the Corporation has elected to permanently exclude capital in accumulated other comprehensive income related to debt and equity securities classified as available-for-sale as well as for defined benefit postretirement plans from CET1, an option available to standardized approach entities under Basel III. Tier 1 capital incrementally includes noncumulative perpetual preferred stock. Tier 2 capital includes Tier 1 capital as well as subordinated debt qualifying as Tier 2 and qualifying allowance for credit losses. Total capital is Tier 1 capital plus Tier 2 capital. Quantitative measures established by regulation to ensure capital adequacy require the maintenance of minimum amounts and ratios of CET1, Tier 1 and total capital (as defined in the regulations) to average and/or risk-weighted assets. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Corporation’s financial statements. At December 31, 2015 and 2014 , the Corporation and its U.S. banking subsidiaries exceeded the ratios required for an institution to be considered “well capitalized” For U.S. banking subsidiaries, those requirements were total risk-based capital, Tier 1 risk-based capital, CET1 risk-based capital and leverage ratios greater than 10 percent , 8 percent , 6.5 percent and 5 percent , respectively, at December 31, 2015 ; and total risk-based capital, Tier 1 risk-based capital and leverage ratios greater than 10 percent , 6 percent and 5 percent , respectively, at December 31, 2014 . For the Corporation, requirements to be considered "well capitalized" were total risk-based capital and Tier 1 risk-based capital ratios greater than 10 percent and 6 percent , respectively, at December 31, 2015 and 2014 . There have been no conditions or events since December 31, 2015 that management believes have changed the capital adequacy classification of the Corporation or its U.S. banking subsidiaries. The following is a summary of the capital position of the Corporation and Comerica Bank, its principal banking subsidiary. (dollar amounts in millions) Comerica Incorporated (Consolidated) Comerica Bank December 31, 2015 CET1 capital (minimum $3.1 billion (Consolidated)) $ 7,350 $ 7,081 Tier 1 capital (minimum-$4.2 billion (Consolidated)) 7,350 7,081 Total capital (minimum-$5.6 billion (Consolidated)) 8,852 8,366 Risk-weighted assets 69,731 69,438 Average assets (fourth quarter) 71,943 71,629 CET1 capital to risk-weighted assets (minimum-4.5%) 10.54 % 10.20 % Tier 1 capital to risk-weighted assets (minimum-6.0%) 10.54 10.20 Total capital to risk-weighted assets (minimum-8.0%) 12.69 12.05 Tier 1 capital to average assets (minimum-4.0%) 10.22 9.89 December 31, 2014 Tier 1 capital (minimum-$2.7 billion (Consolidated)) $ 7,169 $ 7,051 Total capital (minimum-$5.5 billion (Consolidated)) 8,543 8,175 Risk-weighted assets 68,273 68,037 Average assets (fourth quarter) 69,284 69,092 Tier 1 capital to risk-weighted assets (minimum-4.0%) 10.50 % 10.36 % Total capital to risk-weighted assets (minimum-8.0%) 12.51 12.02 Tier 1 capital to average assets (minimum-3.0%) 10.35 10.20

Contingent Liabilities

Contingent Liabilities	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Contingent Liabilities	CONTINGENT LIABILITIES Legal Proceedings Comerica Bank, a wholly owned subsidiary of the Corporation, was named in November 2011 as a third-party defendant in Butte Local Development v. Masters Group v. Comerica Bank (“the case”), for lender liability. The case was tried in January 2014, in the Montana Second District Judicial Court for Silver Bow County in Butte, Montana ("the court"). On January 17, 2014 , a jury awarded Masters $52 million against the Bank. On July 1, 2015, after an appeal filed by the Corporation, the Montana Supreme court ("the court") reversed the judgment against the Corporation and remanded the case for a new trial with instructions that Michigan law should apply. The court also reversed punitive and consequential damages previously awarded by the jury. The Corporation believes it has meritorious defenses to the remaining claims in this case and intends to continue to defend itself vigorously. Management believes that current reserves related to this case are adequate in the event of a negative outcome. The Corporation and certain of its subsidiaries are subject to various other pending or threatened legal proceedings arising out of the normal course of business or operations. The Corporation believes it has meritorious defenses to the claims asserted against it in its other currently outstanding legal proceedings and, with respect to such legal proceedings, intends to continue to defend itself vigorously, litigating or settling cases according to management’s judgment as to what is in the best interests of the Corporation and its shareholders. Settlement may result from the Corporation's determination that it may be more prudent financially to settle, rather than litigate, and should not be regarded as an admission of liability. On at least a quarterly basis, the Corporation assesses its potential liabilities and contingencies in connection with outstanding legal proceedings utilizing the latest information available. On a case-by-case basis, reserves are established for those legal claims for which it is probable that a loss will be incurred either as a result of a settlement or judgment, and the amount of such loss can be reasonably estimated. The actual costs of resolving these claims may be substantially higher or lower than the amounts reserved. Based on current knowledge, and after consultation with legal counsel, management believes that current reserves are adequate, and the amount of any incremental liability arising from these matters is not expected to have a material adverse effect on the Corporation’s consolidated financial condition, consolidated results of operations or consolidated cash flows. Legal fees of $21 million for the year ended December 31, 2015 , and $24 million for each of the years ended December 31, 2014 and 2013 , were included in "other noninterest expenses" on the consolidated statements of income. For matters where a loss is not probable, the Corporation has not established legal reserves. The Corporation believes the estimate of the aggregate range of reasonably possible losses, in excess of reserves established, for all legal proceedings in which it is involved is from zero to approximately $33 million at December 31, 2015 . This estimated aggregate range of reasonably possible losses is based upon currently available information for those proceedings in which the Corporation is involved, taking into account the Corporation’s best estimate of such losses for those cases for which such estimate can be made. For certain cases, the Corporation does not believe that an estimate can currently be made. The Corporation’s estimate involves significant judgment, given the varying stages of the proceedings (including the fact that many are currently in preliminary stages), the existence in certain proceedings of multiple defendants (including the Corporation) whose share of liability has yet to be determined, the numerous yet-unresolved issues in many of the proceedings (including issues regarding class certification and the scope of many of the claims) and the attendant uncertainty of the various potential outcomes of such proceedings. Accordingly, the Corporation’s estimate will change from time to time, and actual losses may be more or less than the current estimate. In the event of unexpected future developments, it is possible that the ultimate resolution of these matters, if unfavorable, may be material to the Corporation's consolidated financial condition, consolidated results of operations or consolidated cash flows. For information regarding income tax contingencies, refer to Note 18 .

Business Segment Information

Business Segment Information	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Business Segment Information	BUSINESS SEGMENT INFORMATION The Corporation has strategically aligned its operations into three major business segments: the Business Bank, the Retail Bank and Wealth Management. These business segments are differentiated based on the type of customer and the related products and services provided. In addition to the three major business segments, the Finance Division is also reported as a segment. Business segment results are produced by the Corporation’s internal management accounting system. This system measures financial results based on the internal business unit structure of the Corporation. The performance of the business segments is not comparable with the Corporation's consolidated results and is not necessarily comparable with similar information for any other financial institution. Additionally, because of the interrelationships of the various segments, the information presented is not indicative of how the segments would perform if they operated as independent entities. The management accounting system assigns balance sheet and income statement items to each business segment using certain methodologies, which are regularly reviewed and refined. From time to time, the Corporation may make reclassifications among the segments to more appropriately reflect management's current view of the segments, and methodologies may be modified as the management accounting system is enhanced and changes occur in the organizational structure and/or product lines. For comparability purposes, amounts in all periods are based on business unit structure and methodologies in effect at December 31, 2015 . Net interest income for each business segment is the total of interest income generated by earning assets less interest expense on interest-bearing liabilities plus the net impact from associated internal funds transfer pricing (FTP) funding credits and charges. The FTP methodology provides the business segments credits for deposits and other funds provided and charges the business segments for loans and other assets utilizing funds. This credit or charge is based on matching stated or implied maturities for these assets and liabilities. The FTP credit provided for deposits reflects the long-term value of deposits generated based on their implied maturity. The FTP charge for funding assets reflects a matched cost of funds based on the pricing and term characteristics of the assets. For acquired loans and deposits, matched maturity funding is determined based on origination date. Accordingly, the FTP process reflects the transfer of interest rate risk exposures to the Treasury group within the Finance segment, where such exposures are centrally managed. The allowance for loan losses is allocated to the business segments based on the methodology used to estimate the consolidated allowance for loan losses described in Note 1. The related provision for loan losses is assigned based on the amount necessary to maintain an allowance for loan losses appropriate for each business segment. Noninterest income and expenses directly attributable to a line of business are assigned to that business segment. Direct expenses incurred by areas whose services support the overall Corporation are allocated to the business segments as follows: product processing expenditures are allocated based on standard unit costs applied to actual volume measurements; administrative expenses are allocated based on estimated time expended; and corporate overhead is assigned 50 percent based on the ratio of the business segment’s noninterest expenses to total noninterest expenses incurred by all business segments and 50 percent based on the ratio of the business segment’s attributed equity to total attributed equity of all business segments. Equity is attributed based on credit, operational and interest rate risks. Most of the equity attributed relates to credit risk, which is determined based on the credit score and expected remaining life of each loan, letter of credit and unused commitment recorded in the business segments. Operational risk is allocated based on loans and letters of credit, deposit balances, non-earning assets, trust assets under management, certain noninterest income items, and the nature and extent of expenses incurred by business units. Virtually all interest rate risk is assigned to Finance, as are the Corporation’s hedging activities. In 2014, the Corporation enhanced the approach used to determine the standard reserve factors used in estimating the allowance for credit losses, which had the effect of capturing certain elements in the standard reserve component that had formerly been included in the qualitative assessment. The impact of the change was largely neutral to the total allowance for loan losses at June 30, 2014. However, because standard reserves are allocated to the segments at the loan level, while qualitative reserves are allocated at the portfolio level, the impact of the methodology change on the allowance of each segment reflected the characteristics of the individual loans within each segment's portfolio, causing segment reserves to increase or decrease accordingly. As a result, the 2014 provision for credit losses within each segment is not comparable to 2013 amounts. Effective January 1, 2015, changes to the terms of card program contract resulted in a change to the presentation of the related revenue and expenses. In 2015, under the current contract, total revenue before related expenses was recorded in noninterest income, and related expenses were recorded in noninterest expense; whereas in 2014, under the terms of the prior contract, revenue was recorded in noninterest income net of the related expenses. The effect of this change was an increase of $181 million to both noninterest income and noninterest expenses in the Business Bank and Other Markets in 2015 . The following discussion provides information about the activities of each business segment. A discussion of the financial results and the factors impacting 2015 performance can be found in the section entitled "Business Segments" in the financial review. The Business Bank meets the needs of middle market businesses, multinational corporations and governmental entities by offering various products and services, including commercial loans and lines of credit, deposits, cash management, capital market products, international trade finance, letters of credit, foreign exchange management services and loan syndication services. The Retail Bank includes small business banking and personal financial services, consisting of consumer lending, consumer deposit gathering and mortgage loan origination. In addition to a full range of financial services provided to small business customers, this business segment offers a variety of consumer products, including deposit accounts, installment loans, credit cards, student loans, home equity lines of credit and residential mortgage loans. Wealth Management offers products and services consisting of fiduciary services, private banking, retirement services, investment management and advisory services, investment banking and brokerage services. This business segment also offers the sale of annuity products, as well as life, disability and long-term care insurance products. The Finance segment includes the Corporation’s securities portfolio and asset and liability management activities. This segment is responsible for managing the Corporation’s funding, liquidity and capital needs, performing interest sensitivity analysis and executing various strategies to manage the Corporation’s exposure to liquidity, interest rate risk and foreign exchange risk. The Other category includes the income and expense impact of equity and cash, tax benefits not assigned to specific business segments, charges of an unusual or infrequent nature that are not reflective of the normal operations of the business segments and miscellaneous other expenses of a corporate nature. Business segment financial results are as follows: (dollar amounts in millions) Business Bank Retail Bank Wealth Management Finance Other Total Year Ended December 31, 2015 Earnings summary: Net interest income (expense) (FTE) $ 1,511 $ 626 $ 179 $ (632 ) $ 9 $ 1,693 Provision for credit losses 158 8 (20 ) — 1 147 Noninterest income 574 185 235 57 (1 ) 1,050 Noninterest expenses 786 734 305 9 8 1,842 Provision (benefit) for income taxes (FTE) 376 22 44 (209 ) — 233 Net income (loss) $ 765 $ 47 $ 85 $ (375 ) $ (1 ) $ 521 Net loan charge-offs (recoveries) $ 89 $ 28 $ (17 ) $ — $ — $ 100 Selected average balances: Assets $ 38,942 $ 6,474 $ 5,153 $ 12,180 $ 7,498 $ 70,247 Loans 37,883 5,792 4,953 — — 48,628 Deposits 30,882 22,876 4,151 149 268 58,326 Statistical data: Return on average assets (a) 1.96 % 0.20 % 1.65 % N/M N/M 0.74 % Efficiency ratio (b) 37.71 90.37 73.23 N/M N/M 67.10 (dollar amounts in millions) Business Bank Retail Bank Wealth Management Finance Other Total Year Ended December 31, 2014 Earnings summary: Net interest income (expense) (FTE) $ 1,507 $ 606 $ 181 $ (662 ) $ 27 $ 1,659 Provision for credit losses 56 (7 ) (21 ) — (1 ) 27 Noninterest income 392 169 241 60 6 868 Noninterest expenses 589 715 310 (21 ) 33 1,626 Provision (benefit) for income taxes (FTE) 432 23 49 (224 ) 1 281 Net income (loss) $ 822 $ 44 $ 84 $ (357 ) $ — $ 593 Net loan charge-offs (recoveries) $ 16 $ 10 $ (1 ) $ — $ — $ 25 Selected average balances: Assets $ 37,178 $ 6,255 $ 4,988 $ 11,359 $ 6,556 $ 66,336 Loans 36,198 5,585 4,805 — — 46,588 Deposits 28,526 21,967 3,805 233 253 54,784 Statistical data: Return on average assets (a) 2.21 % 0.19 % 1.69 % N/M N/M 0.89 % Efficiency ratio (b) 30.97 92.10 73.67 N/M N/M 64.31 (Table continues on following page) (dollar amounts in millions) Business Bank Retail Bank Wealth Management Finance Other Total Year Ended December 31, 2013 Earnings summary: Net interest income (expense) (FTE) $ 1,495 $ 622 $ 180 $ (653 ) $ 31 $ 1,675 Provision for credit losses 42 24 (17 ) — (3 ) 46 Noninterest income 398 176 235 61 12 882 Noninterest expenses 642 719 309 10 42 1,722 Provision (benefit) for income taxes (FTE) 410 19 44 (226 ) 1 248 Net income (loss) $ 799 $ 36 $ 79 $ (376 ) $ 3 $ 541 Net loan charge-offs $ 32 $ 33 $ 8 $ — $ — $ 73 Selected average balances: Assets $ 35,326 $ 6,185 $ 4,799 $ 11,422 $ 6,201 $ 63,933 Loans 34,268 5,500 4,644 — — 44,412 Deposits 26,131 21,513 3,547 312 208 51,711 Statistical data: Return on average assets (a) 2.26 % 0.16 % 1.64 % N/M N/M 0.85 % Efficiency ratio (b) 33.89 89.77 74.86 N/M N/M 67.32 (a) Return on average assets is calculated based on the greater of average assets or average liabilities and attributed equity. (b) Noninterest expenses as a percentage of the sum of net interest income (FTE) and noninterest income excluding net securities gains. FTE – Fully Taxable Equivalent N/M – not meaningful The Corporation operates in three primary markets - Texas, California, and Michigan, as well as in Arizona and Florida, with select businesses operating in several other states, and in Canada and Mexico. The Corporation produces market segment results for the Corporation’s three primary geographic markets as well as Other Markets. Other Markets includes Florida, Arizona, the International Finance division and businesses with a national perspective. The Finance & Other category includes the Finance segment and the Other category as previously described. Market segment results are provided as supplemental information to the business segment results and may not meet all operating segment criteria as set forth in GAAP. For comparability purposes, amounts in all periods are based on market segments and methodologies in effect at December 31, 2015 . A discussion of the financial results and the factors impacting performance can be found in the section entitled "Market Segments" in the financial review. Market segment financial results are as follows: (dollar amounts in millions) Michigan California Texas Other Markets Finance & Other Total Year Ended December 31, 2015 Earnings summary: Net interest income (expense) (FTE) $ 720 $ 736 $ 521 $ 339 $ (623 ) $ 1,693 Provision for credit losses (27 ) 17 131 25 1 147 Noninterest income 333 153 133 375 56 1,050 Noninterest expenses 598 408 389 430 17 1,842 Provision (benefit) for income taxes (FTE) 157 167 55 63 (209 ) 233 Net income (loss) $ 325 $ 297 $ 79 $ 196 $ (376 ) $ 521 Net loan charge-offs $ 8 $ 18 $ 45 $ 29 $ — $ 100 Selected average balances: Assets $ 13,761 $ 16,881 $ 11,778 $ 8,149 $ 19,678 $ 70,247 Loans 13,180 16,613 11,168 7,667 — 48,628 Deposits 21,872 17,763 10,882 7,392 417 58,326 Statistical data: Return on average assets (a) 1.42 % 1.57 % 0.63 % 2.41 % N/M 0.74 % Efficiency ratio (b) 56.72 45.96 59.52 59.97 N/M 67.10 (Table continues on following page) (dollar amounts in millions) Michigan California Texas Other Markets Finance & Other Total Year Ended December 31, 2014 Earnings summary: Net interest income (expense) (FTE) $ 718 $ 722 $ 542 $ 312 $ (635 ) $ 1,659 Provision for credit losses (32 ) 28 50 (18 ) (1 ) 27 Noninterest income 345 147 142 168 66 868 Noninterest expenses 643 398 370 203 12 1,626 Provision (benefit) for income taxes (FTE) 164 169 96 75 (223 ) 281 Net income (loss) $ 288 $ 274 $ 168 $ 220 $ (357 ) $ 593 Net loan charge-offs (recoveries) $ 8 $ 22 $ 9 $ (14 ) $ — $ 25 Selected average balances: Assets $ 13,749 $ 15,668 $ 11,645 $ 7,359 $ 17,915 $ 66,336 Loans 13,336 15,390 10,954 6,908 — 46,588 Deposits 21,023 16,142 10,764 6,369 486 54,784 Statistical data: Return on average assets (a) 1.31 % 1.59 % 1.39 % 3.00 % N/M 0.89 % Efficiency ratio (b) 60.48 45.79 54.00 42.30 N/M 64.31 (dollar amounts in millions) Michigan California Texas Other Markets Finance & Other Total Year Ended December 31, 2013 Earnings summary: Net interest income (expense) (FTE) $ 751 $ 692 $ 541 $ 313 $ (622 ) $ 1,675 Provision for credit losses (11 ) 17 35 8 (3 ) 46 Noninterest income 343 151 142 173 73 882 Noninterest expenses 713 396 364 197 52 1,722 Provision (benefit) for income taxes (FTE) 140 160 101 72 (225 ) 248 Net income (loss) $ 252 $ 270 $ 183 $ 209 $ (373 ) $ 541 Net loan charge-offs $ 6 $ 27 $ 20 $ 20 $ — $ 73 Selected average balances: Assets $ 13,879 $ 14,233 $ 10,694 $ 7,504 $ 17,623 $ 63,933 Loans 13,461 13,979 9,988 6,984 — 44,412 Deposits 20,346 14,705 10,247 5,893 520 51,711 Statistical data: Return on average assets (a) 1.18 % 1.72 % 1.59 % 2.79 % N/M 0.85 % Efficiency ratio (b) 65.09 47.00 53.22 40.52 N/M 67.32 (a) Return on average assets is calculated based on the greater of average assets or average liabilities and attributed equity. (b) Noninterest expenses as a percentage of the sum of net interest income (FTE) and noninterest income excluding net securities gains. FTE – Fully Taxable Equivalent N/M – not meaningful

Parent Company FInancial Statem

Parent Company FInancial Statements	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Parent Company Financial Statments	PARENT COMPANY FINANCIAL STATEMENTS BALANCE SHEETS - COMERICA INCORPORATED (in millions, except share data) December 31 2015 2014 Assets Cash and due from subsidiary bank $ 4 $ — Short-term investments with subsidiary bank 569 1,133 Other short-term investments 89 94 Investment in subsidiaries, principally banks 7,523 7,411 Premises and equipment 3 2 Other assets 137 138 Total assets $ 8,325 $ 8,778 Liabilities and Shareholders’ Equity Medium- and long-term debt $ 608 $ 1,208 Other liabilities 157 168 Total liabilities 765 1,376 Common stock - $5 par value: Authorized - 325,000,000 shares Issued - 228,164,824 shares 1,141 1,141 Capital surplus 2,173 2,188 Accumulated other comprehensive loss (429 ) (412 ) Retained earnings 7,084 6,744 Less cost of common stock in treasury - 52,457,113 shares at 12/31/15 and 49,146,225 shares at 12/31/14 (2,409 ) (2,259 ) Total shareholders’ equity 7,560 7,402 Total liabilities and shareholders’ equity $ 8,325 $ 8,778 STATEMENTS OF INCOME - COMERICA INCORPORATED (in millions) Years Ended December 31 2015 2014 2013 Income Income from subsidiaries: Dividends from subsidiaries $ 441 $ 384 $ 490 Other interest income 1 1 1 Intercompany management fees 123 118 110 Other noninterest income 1 7 14 Total income 566 510 615 Expenses Interest on medium- and long-term debt 14 14 11 Salaries and benefits expense 112 114 118 Net occupancy expense 5 5 4 Equipment expense 1 1 1 Other noninterest expenses 70 70 78 Total expenses 202 204 212 Income before benefit for income taxes and equity in undistributed earnings of subsidiaries 364 306 403 Benefit for income taxes (27 ) (27 ) (30 ) Income before equity in undistributed earnings of subsidiaries 391 333 433 Equity in undistributed earnings of subsidiaries, principally banks 130 260 108 Net income 521 593 541 Less income allocated to participating securities 6 7 8 Net income attributable to common shares $ 515 $ 586 $ 533 STATEMENTS OF CASH FLOWS - COMERICA INCORPORATED (in millions) Years Ended December 31 2015 2014 2013 Operating Activities Net income $ 521 $ 593 $ 541 Adjustments to reconcile net income to net cash provided by operating activities: Undistributed earnings of subsidiaries, principally banks (130 ) (260 ) (108 ) Depreciation and amortization 1 1 1 Net periodic defined benefit cost 5 4 8 Share-based compensation expense 14 16 14 Provision for deferred income taxes — — 3 Excess tax benefits from share-based compensation arrangements (3 ) (7 ) (3 ) Other, net 5 16 2 Net cash provided by operating activities 413 363 458 Investing Activities Net change in premises and equipment (1 ) 2 — Net cash (used in) provided by investing activities (1 ) 2 — Financing Activities Medium- and long-term debt: Maturities and redemptions (600 ) — — Issuances — 596 — Common Stock: Repurchases (240 ) (260 ) (291 ) Cash dividends paid (147 ) (137 ) (123 ) Issuances of common stock under employee stock plans 22 49 33 Purchase and retirement of warrants (10 ) — — Excess tax benefits from share-based compensation arrangements 3 7 3 Net cash (used in) provided by financing activities (972 ) 255 (378 ) Net (decrease) increase in cash and cash equivalents (560 ) 620 80 Cash and cash equivalents at beginning of period 1,133 513 433 Cash and cash equivalents at end of period $ 573 $ 1,133 $ 513 Interest paid $ 16 $ 12 $ 11 Income taxes recovered $ (62 ) $ (33 ) $ (27 )

Summary of Quarterly Financial

Summary of Quarterly Financial Statements (Unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Statements (Unaudited)	SUMMARY OF QUARTERLY FINANCIAL STATEMENTS (UNAUDITED) The following quarterly information is unaudited. However, in the opinion of management, the information reflects all adjustments, which are necessary for the fair presentation of the results of operations, for the periods presented. 2015 (in millions, except per share data) Fourth Quarter Third Quarter Second Quarter First Quarter Interest income $ 457 $ 448 $ 444 $ 435 Interest expense 24 26 23 22 Net interest income 433 422 421 413 Provision for credit losses 60 26 47 14 Net securities losses — — — (2 ) Noninterest income excluding net securities losses 270 264 261 257 Noninterest expenses 486 461 436 459 Provision for income taxes 41 63 64 61 Net income 116 136 135 134 Less income allocated to participating securities 1 2 1 2 Net income attributable to common shares $ 115 $ 134 $ 134 $ 132 Earnings per common share: Basic $ 0.65 $ 0.76 $ 0.76 $ 0.75 Diluted 0.64 0.74 0.73 0.73 Comprehensive income 31 187 109 176 2014 (in millions, except per share data) Fourth Quarter Third Quarter Second Quarter First Quarter Interest income $ 438 $ 436 $ 441 $ 435 Interest expense 23 22 25 25 Net interest income 415 414 416 410 Provision for credit losses 2 5 11 9 Net securities (losses) gains — (1 ) — 1 Noninterest income excluding net securities (losses) gains 225 216 220 207 Noninterest expenses 419 397 404 406 Provision for income taxes 70 73 70 64 Net income 149 154 151 139 Less income allocated to participating securities 1 2 2 2 Net income attributable to common shares $ 148 $ 152 $ 149 $ 137 Earnings per common share: Basic $ 0.83 $ 0.85 $ 0.83 $ 0.76 Diluted 0.80 0.82 0.80 0.73 Comprehensive income 54 141 172 205

Subsequent Event

Subsequent Event	12 Months Ended
	Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Events [Text Block]	SUBSEQUENT EVENTS As disclosed on February 16, 2016 , the Corporation's previously reported results for the fourth quarter and full year 2015 were reduced by $14 million ($22 million, pre-tax) for recently discovered irregularities with a single customer loan relationship in the Retail Bank. The Corporation increased its provision for credit losses and recorded a charge-off for $25 million, and decreased incentive compensation expense by approximately $3 million based on the revised results. The results reported in this Annual Report reflect the impact of this event. Subsequent to December 31, 2015, oil and gas prices dropped significantly. The allowance for loan losses allocation for energy and energy-related loans was based upon energy prices and conditions in existence at the balance sheet date.

Basis of Presentation and Acc34

Basis of Presentation and Accounting Policies Basis of Presentation and Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the Corporation and the accounts of those subsidiaries that are majority owned and in which the Corporation has a controlling financial interest. The Corporation consolidates entities not determined to be variable interest entities (VIEs) when it holds a controlling financial interest in the entity's outstanding voting stock and uses the cost or equity method when it holds less than a controlling financial interest. In consolidation, all significant intercompany accounts and transactions are eliminated. The results of operations of companies acquired are included from the date of acquisition. Certain amounts in the financial statements for prior years have been reclassified to conform to current financial statement presentation. The Corporation holds investments in certain legal entities that are considered VIEs. In general, a VIE is an entity that either (1) has an insufficient amount of equity to carry out its principal activities without additional subordinated financial support, (2) has a group of equity owners that are unable to make significant decisions about its activities, or (3) has a group of equity owners that do not have the obligation to absorb losses or the right to receive returns generated by its operations. If any of these characteristics are present, the entity is subject to a variable interests consolidation model, and consolidation is based on variable interests, not on ownership of the entity’s outstanding voting stock. Variable interests are defined as contractual ownership or other money interests in an entity that change with fluctuations in the entity’s net asset value. The primary beneficiary is required to consolidate the VIE. The primary beneficiary is defined as the party that has both the power to direct the activities of the VIE that most significantly impact the entity’s economic performance and the obligation to absorb losses or the right to receive benefits that could be significant to the VIE. The maximum potential exposure to losses relative to investments in VIEs is generally limited to the sum of the outstanding book basis and unfunded commitments for future investments. The Corporation evaluates its investments in VIEs, both at inception and when there is a change in circumstances that requires reconsideration, to determine if the Corporation is the primary beneficiary and consolidation is required. The Corporation accounts for unconsolidated VIEs using either the proportional, cost or equity method. These investments comprise investments in community development projects which generate tax credits to their investors and are included in "accrued income and other assets" on the consolidated balance sheets. The proportional method is used for investments in affordable housing projects that qualify for the low-income housing tax credit (LIHTC). The equity method is used for other investments where the Corporation has the ability to exercise significant influence over the entity’s operation and financial policies, which is generally presumed to exist if the Corporation owns more than a 20 percent voting interest in the entity. Other unconsolidated equity investments that do not meet the criteria to be accounted for under the equity method are accounted for under the cost method. Amortization and other write-downs of LIHTC investments are presented on a net basis as a component of the "provision for income taxes," while income, amortization and write-downs from cost and equity method investments are recorded in “other noninterest income” on the consolidated statements of income. Assets held in an agency or fiduciary capacity are not assets of the Corporation and are not included in the consolidated financial statements.
Fair Value Measurements	Fair Value Measurements The Corporation utilizes fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures. The determination of fair values of financial instruments often requires the use of estimates. In cases where quoted market values in an active market are not available, the Corporation uses present value techniques and other valuation methods to estimate the fair values of its financial instruments. These valuation methods require considerable judgment and the resulting estimates of fair value can be significantly affected by the assumptions made and methods used. Fair value is an estimate of the exchange price that would be received to sell an asset or paid to transfer a liability in an orderly transaction (i.e., not a forced transaction, such as a liquidation or distressed sale) between market participants at the measurement date. Fair value is based on the assumptions market participants would use when pricing an asset or liability. Trading securities, investment securities available-for-sale, derivatives and deferred compensation plan liabilities are recorded at fair value on a recurring basis. Additionally, from time to time, the Corporation may be required to record other assets and liabilities at fair value on a nonrecurring basis, such as impaired loans, other real estate (primarily foreclosed property), nonmarketable equity securities and certain other assets and liabilities. These nonrecurring fair value adjustments typically involve write-downs of individual assets or application of lower of cost or fair value accounting. Fair value measurements and disclosures guidance establishes a three-level fair value hierarchy based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. The fair value hierarchy gives the highest priority to quoted prices in active markets and the lowest priority to unobservable data. Fair value measurements are separately disclosed by level within the fair value hierarchy. For assets and liabilities recorded at fair value, it is the Corporation’s policy to maximize the use of observable inputs and minimize the use of unobservable inputs when developing fair value measurements. Level 1 Valuation is based upon quoted prices for identical instruments traded in active markets. Level 2 Valuation is based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-based valuation techniques for which all significant assumptions are observable in the market. Level 3 Valuation is generated from model-based techniques that use at least one significant assumption not observable in the market. These unobservable assumptions reflect estimates of assumptions that market participants would use in pricing the asset or liability. Valuation techniques include use of option pricing models, discounted cash flow models and similar techniques. The Corporation generally utilizes third-party pricing services to value Level 1 and Level 2 trading and investment securities, as well as certain derivatives designated as fair value hedges. Management reviews the methodologies and assumptions used by the third-party pricing services and evaluates the values provided, principally by comparison with other available market quotes for similar instruments and/or analysis based on internal models using available third-party market data. The Corporation may occasionally adjust certain values provided by the third-party pricing service when management believes, as the result of its review, that the adjusted price most appropriately reflects the fair value of the particular security. Fair value measurements for assets and liabilities where limited or no observable market data exists are based primarily upon estimates, often calculated based on the economic and competitive environment, the characteristics of the asset or liability and other factors. Therefore, the results cannot be determined with precision and may not be realized in an actual sale or immediate settlement of the asset or liability. Additionally, there may be inherent weaknesses in any calculation technique, and changes in the underlying assumptions used, including discount rates and estimates of future cash flows, could significantly affect the results of current or future values. Following are descriptions of the valuation methodologies and key inputs used to measure financial assets and liabilities recorded at fair value, as well as a description of the methods and significant assumptions used to estimate fair value disclosures for financial instruments not recorded at fair value in their entirety on a recurring basis. The descriptions include an indication of the level of the fair value hierarchy in which the assets or liabilities are classified. Transfers of assets or liabilities between levels of the fair value hierarchy are recognized at the beginning of the reporting period, when applicable. Cash and due from banks, federal funds sold and interest-bearing deposits with banks Due to their short-term nature, the carrying amount of these instruments approximates the estimated fair value. As such, the Corporation classifies the estimated fair value of these instruments as Level 1. Trading securities and associated deferred compensation plan liabilities Trading securities include securities held for trading purposes as well as assets held related to employee deferred compensation plans. Trading securities and associated deferred compensation plan liabilities are recorded at fair value on a recurring basis and included in “other short-term investments” and “accrued expenses and other liabilities,” respectively, on the consolidated balance sheets. Level 1 trading securities include assets related to employee deferred compensation plans, which are invested in mutual funds, U.S. Treasury securities that are traded by dealers or brokers in active over-the-counter markets and other securities traded on an active exchange, such as the New York Stock Exchange. Deferred compensation plan liabilities represent the fair value of the obligation to the employee, which corresponds to the fair value of the invested assets. Level 2 trading securities include municipal bonds and residential mortgage-backed securities issued by U.S. government-sponsored entities and corporate debt securities. The methods used to value trading securities are the same as the methods used to value investment securities, discussed below. Investment securities Investment securities available-for-sale are recorded at fair value on a recurring basis. The Corporation discloses estimated fair values of investment securities held-to-maturity, which is determined in the same manner as investment securities available-for-sale. Level 1 securities include those traded on an active exchange, such as the New York Stock Exchange, U.S. Treasury securities that are traded by dealers or brokers in active over-the-counter markets and money market funds. Level 2 securities include residential mortgage-backed securities issued by U.S. government agencies and U.S. government-sponsored entities and corporate debt securities. The fair value of Level 2 securities is determined using quoted prices of securities with similar characteristics, or pricing models based on observable market data inputs, primarily interest rates, spreads and prepayment information. Securities classified as Level 3 represent securities in less liquid markets requiring significant management assumptions when determining fair value. Auction-rate securities comprise Level 3 investment securities available-for-sale. The Corporate Development Department, with appropriate oversight and approval provided by senior management, is responsible for determining the valuation methodology for auction-rate securities and for updating significant inputs. Valuation results, including an analysis of changes to the valuation methodology and significant inputs, are provided to senior management for review on a quarterly basis. Loans held-for-sale Loans held-for-sale, included in “other short-term investments” on the consolidated balance sheets, are recorded at the lower of cost or fair value. Loans held-for-sale may be carried at fair value on a nonrecurring basis when fair value is less than cost. The fair value is based on what secondary markets are currently offering for portfolios with similar characteristics. As such, the Corporation classifies both loans held-for-sale subjected to nonrecurring fair value adjustments and the estimated fair value of loans held-for sale as Level 2. Loans The Corporation does not record loans at fair value on a recurring basis. However, the Corporation may establish a specific allowance for an impaired loan based on the fair value of the underlying collateral. Such loan values are reported as nonrecurring fair value measurements. Collateral values supporting individually evaluated impaired loans are evaluated quarterly. When management determines that the fair value of the collateral requires additional adjustments, either as a result of non-current appraisal value or when there is no observable market price, the Corporation classifies the impaired loan as Level 3. The Special Assets Group is responsible for performing quarterly credit quality reviews for all impaired loans as part of the quarterly allowance for loan losses process overseen by the Chief Credit Officer, during which valuation adjustments to updated collateral values are determined. The Corporation discloses fair value estimates for loans. The estimated fair value is determined based on characteristics such as loan category, repricing features and remaining maturity, and includes prepayment and credit loss estimates. For variable rate business loans that reprice frequently, the estimated fair value is based on carrying values adjusted for estimated credit losses inherent in the portfolio at the balance sheet date. For other business loans and retail loans, fair values are estimated using a discounted cash flow model that employs a discount rate that reflects the Corporation's current pricing for loans with similar characteristics and remaining maturity, adjusted by an amount for estimated credit losses inherent in the portfolio at the balance sheet date. The rates take into account the expected yield curve, as well as an adjustment for prepayment risk, when applicable. The Corporation classifies the estimated fair value of loans held for investment as Level 3. Customers’ liability on acceptances outstanding and acceptances outstanding Customers' liability on acceptances outstanding is included in "accrued income and other assets" and acceptances outstanding are included in "accrued expenses and other liabilities" on the consolidated balance sheets. Due to their short-term nature, the carrying amount of these instruments approximates the estimated fair value. As such, the Corporation classifies the estimated fair value of these instruments as Level 1. Derivative assets and derivative liabilities Derivative instruments held or issued for risk management or customer-initiated activities are traded in over-the-counter markets where quoted market prices are not readily available. Fair value for over-the-counter derivative instruments is measured on a recurring basis using internally developed models that use primarily market observable inputs, such as yield curves and option volatilities. The Corporation manages credit risk on its derivative positions based on whether the derivatives are being settled through a clearinghouse or bilaterally with each counterparty. For derivative positions settled on a counterparty-by-counterparty basis, the Corporation calculates credit valuation adjustments, included in the fair value of these instruments, on the basis of its relationships at the counterparty portfolio/master netting agreement level. These credit valuation adjustments are determined by applying a credit spread for the counterparty or the Corporation, as appropriate, to the total expected exposure of the derivative after considering collateral and other master netting arrangements. These adjustments, which are considered Level 3 inputs, are based on estimates of current credit spreads to evaluate the likelihood of default. When credit valuation adjustments are significant to the overall fair value of a derivative, the Corporation classifies the over-the-counter derivative valuation in Level 3 of the fair value hierarchy; otherwise, over-the-counter derivative valuations are classified in Level 2. Warrants which contain a net exercise provision or a non-contingent put right embedded in the warrant agreement are accounted for as derivatives and recorded at fair value on a recurring basis using a Black-Scholes valuation model. The Black-Scholes valuation model utilizes five inputs: risk-free rate, expected life, volatility, exercise price, and the per share market value of the underlying company. The Corporation holds a portfolio of warrants for generally nonmarketable equity securities with a fair value of $2 million at December 31, 2015 , included in "accrued income and other assets" on the consolidated balance sheets. These warrants are primarily from non-public technology companies obtained as part of the loan origination process. The Corporate Development Department is responsible for the warrant valuation process, which includes reviewing all significant inputs for reasonableness, and for providing valuation results to senior management. Increases in any of these inputs in isolation, with the exception of exercise price, would result in a higher fair value. Increases in exercise price in isolation would result in a lower fair value. The Corporation classifies warrants accounted for as derivatives as Level 3. Nonmarketable equity securities The Corporation has a portfolio of indirect (through funds) private equity and venture capital investments with a carrying value and unfunded commitments of $10 million and $4 million , respectively, at December 31, 2015 . These funds generally cannot be redeemed and the majority is not readily marketable. Distributions from these funds are received by the Corporation as a result of the liquidation of underlying investments of the funds and/or as income distributions. It is estimated that the underlying assets of the funds will be liquidated over a period of up to 12 years. Recently issued federal regulations may require the Corporation to sell certain of these funds prior to liquidation. The investments are accounted for either on the cost or equity method and are individually reviewed for impairment on a quarterly basis by comparing the carrying value to the estimated fair value. These investments may be carried at fair value on a nonrecurring basis when they are deemed to be impaired and written down to fair value. Where there is not a readily determinable fair value, the Corporation estimates fair value for indirect private equity and venture capital investments based on the net asset value, as reported by the fund, after indication that the fund adheres to applicable fair value measurement guidance. On a quarterly basis, the Corporate Development Department is responsible, with appropriate oversight and approval provided by senior management, for performing the valuation procedures and updating significant inputs, as are primarily provided by the underlying fund's management. The Corporation classifies fair value measurements of nonmarketable equity securities as Level 3. The Corporation also holds restricted equity investments, primarily Federal Home Loan Bank (FHLB) and Federal Reserve Bank (FRB) stock. Restricted equity securities are not readily marketable and are recorded at cost (par value) in "accrued income and other assets" on the consolidated balance sheets and evaluated for impairment based on the ultimate recoverability of the par value. No significant observable market data for these instruments is available. The Corporation considers the profitability and asset quality of the issuer, dividend payment history and recent redemption experience and believes its investments in FHLB and FRB stock are ultimately recoverable at par. Therefore, the carrying amount for these restricted equity investments approximates fair value. The Corporation classifies the estimated fair value of such investments as Level 1. The Corporation’s investment in FHLB stock totaled $7 million at both December 31, 2015 and 2014 , and its investment in FRB stock totaled $85 million at both December 31, 2015 and 2014 . Other real estate Other real estate is included in “accrued income and other assets” on the consolidated balance sheets and includes primarily foreclosed property. Foreclosed property is initially recorded at fair value, less costs to sell, at the date of foreclosure, establishing a new cost basis. Subsequently, foreclosed property is carried at the lower of cost or fair value, less costs to sell. Other real estate may be carried at fair value on a nonrecurring basis when fair value is less than cost. Fair value is based upon independent market prices, appraised value or management's estimate of the value of the property. The Special Assets Group obtains updated independent market prices and appraised values, as required by state regulation or deemed necessary based on market conditions, and determines if additional write-downs are necessary. On a quarterly basis, senior management reviews all other real estate and determines whether the carrying values are reasonable, based on the length of time elapsed since receipt of independent market price or appraised value and current market conditions. When management determines that the fair value of other real estate requires additional adjustments, either as a result of a non-current appraisal or when there is no observable market price, the Corporation classifies the other real estate as Level 3. Deposit liabilities The estimated fair value of checking, savings and certain money market deposit accounts is represented by the amounts payable on demand. The estimated fair value of term deposits is calculated by discounting the scheduled cash flows using the period-end rates offered on these instruments. As such, the Corporation classifies the estimated fair value of deposit liabilities as Level 2. Short-term borrowings The carrying amount of federal funds purchased, securities sold under agreements to repurchase and other short-term borrowings approximates the estimated fair value. As such, the Corporation classifies the estimated fair value of short-term borrowings as Level 1. Medium- and long-term debt The estimated fair value of the Corporation's medium- and long-term debt is based on quoted market values when available. If quoted market values are not available, the estimated fair value is based on the market values of debt with similar characteristics. The Corporation classifies the estimated fair value of medium- and long-term debt as Level 2. Credit-related financial instruments Credit-related financial instruments include unused commitments to extend credit and letters of credit. These instruments generate ongoing fees which are recognized over the term of the commitment. In situations where credit losses are probable, the Corporation records an allowance. The carrying value of these instruments included in "accrued expenses and other liabilities" on the consolidated balance sheets, which includes the carrying value of the deferred fees plus the related allowance, approximates the estimated fair value. The Corporation classifies the estimated fair value of credit-related financial instruments as Level 3.
Other Short-Term Investments	Other Short-Term Investments Other short-term investments include trading securities and loans held-for-sale. Trading securities are carried at fair value. Realized and unrealized gains or losses on trading securities are included in “other noninterest income” on the consolidated statements of income. Loans held-for-sale, typically residential mortgages originated with the intent to sell and occasionally may include other loans transferred to held-for-sale, are carried at the lower of cost or fair value. Fair value is determined in the aggregate for each portfolio. Changes in fair value are included in “other noninterest income” on the consolidated statements of income.
Investment Securities	Investment Securities Securities not held for trading purposes are classified as available-for-sale or held-to-maturity. Debt securities for which management has the intent and ability to hold to maturity are classified as held-to-maturity and recorded at amortized cost. Securities available-for-sale are recorded at fair value, with unrealized gains and losses, net of income taxes, reported as a separate component of other comprehensive income (loss) (OCI). Securities transferred from available-for-sale to held-to-maturity are reclassified at fair value on the date of transfer. The net unrealized gain (loss) at the date of transfer is included in historical cost and amortized over the remaining life of the related securities as a yield adjustment consistent with the amortization of the net unrealized gain (loss) included in accumulated other comprehensive loss on the same securities, resulting in no impact to net income. Investment securities are reviewed quarterly for possible other-than-temporary impairment (OTTI). In determining whether OTTI exists for debt securities in an unrealized loss position, the Corporation assesses the likelihood of selling the security prior to the recovery of its amortized cost basis. If the Corporation intends to sell the debt security or it is more likely than not that the Corporation will be required to sell the debt security prior to the recovery of its amortized cost basis, the debt security is written down to fair value, and the full amount of any impairment charge is recorded as a loss in “net securities gains” in the consolidated statements of income. If the Corporation does not intend to sell the debt security and it is more likely than not that the Corporation will not be required to sell the debt security prior to recovery of its amortized cost basis, only the credit component of any impairment of a debt security is recognized as a loss in “net securities gains” on the consolidated statements of income, with the remaining impairment recorded in OCI. The OTTI review for equity securities includes an analysis of the facts and circumstances of each individual investment and focuses on the severity of loss, the length of time the fair value has been below cost, the expectation for that security’s performance, the financial condition and near-term prospects of the issuer, and management’s intent and ability to hold the security to recovery. A decline in value of an equity security that is considered to be other-than-temporary is recorded as a loss in “net securities (losses) gains” on the consolidated statements of income. Gains or losses on the sale of securities are computed based on the adjusted cost of the specific security sold.
Loans	Loans Loans and leases originated and held for investment are recorded at the principal balance outstanding, net of unearned income, charge-offs and unamortized deferred fees and costs. Interest income is recognized on loans and leases using the interest method.
Acquired Loans, Impaired	Loans and leases acquired in business combinations are initially recorded at fair value with no carryover of any existing allowance for loan losses. Acquired loans with evidence of credit quality deterioration at acquisition are reviewed to determine if it is probable that the Corporation will not be able to collect all contractual amounts due, including both principal and interest. When both conditions exist, such loans are accounted for as purchased credit-impaired (PCI) loans. The Corporation generally aggregates PCI loans into pools of loans based on common risk characteristics. The Corporation estimates the total cash flows expected to be collected from the pools of acquired PCI loans, which include undiscounted expected principal and interest, using credit risk, interest rate and prepayment risk models that incorporate management's best estimate of current key assumptions such as default rates, loss severity and payment speeds. The excess of the undiscounted total cash flows expected to be collected over the fair value of the related PCI loans represents the accretable yield, which is recognized as interest income on a level-yield basis over the life of the related loan pools.
Acquired Loans, Not Impaired	For acquired loans not deemed credit-impaired at acquisition, the difference between the initial fair value and the unpaid principal balance is recognized as interest income on a level-yield basis over the lives of the related loans.
Loans, Troubled Debt Restructuring	The Corporation assesses all loan modifications to determine whether a restructuring constitutes a troubled debt restructuring (TDR). A restructuring is considered a TDR when a borrower is experiencing financial difficulty and the Corporation grants a concession to the borrower. TDRs on accrual status at the original contractual rate of interest are considered performing. Nonperforming TDRs include TDRs on nonaccrual status and loans which have been renegotiated to less than the original contractual rates (reduced-rate loans). All TDRs are considered impaired loans.
Loan Origination Fees and Costs	Loan Origination Fees and Costs Substantially all loan origination fees and costs are deferred and amortized to net interest income over the life of the related loan or over the commitment period as a yield adjustment. Net deferred income on originated loans, including unearned income and unamortized costs, fees, premiums and discounts, totaled $226 million and $267 million at December 31, 2015 and 2014 , respectively. Loan fees on unused commitments and net origination fees related to loans sold are recognized in noninterest income.
Allowance for Credit Losses	Allowance for Credit Losses The allowance for credit losses includes both the allowance for loan losses and the allowance for credit losses on lending-related commitments. The Corporation disaggregates the loan portfolio into segments for purposes of determining the allowance for credit losses. These segments are based on the level at which the Corporation develops, documents and applies a systematic methodology to determine the allowance for credit losses. The Corporation's portfolio segments are business loans and retail loans. Business loans include the commercial, real estate construction, commercial mortgage, lease financing and international loan portfolios. Retail loans consist of traditional residential mortgage, home equity and other consumer loans.
Allowance for Loan Losses	Allowance for Loan Losses The allowance for loan losses represents management’s assessment of probable, estimable losses inherent in the Corporation’s loan portfolio. The allowance for loan losses includes specific allowances, based on individual evaluations of certain loans, and allowances for homogeneous pools of loans with similar risk characteristics. The Corporation individually evaluates certain impaired loans on a quarterly basis and establishes specific allowances for such loans, if required. A loan is considered impaired when it is probable that interest or principal payments will not be made in accordance with the contractual terms of the loan agreement. Consistent with this definition, all loans for which the accrual of interest has been discontinued (nonaccrual loans) are considered impaired. The Corporation individually evaluates nonaccrual loans with book balances of $2 million or more and accruing loans whose terms have been modified in a TDR. The threshold for individual evaluation is revised on an infrequent basis, generally when economic circumstances change significantly. Specific allowances for impaired loans are estimated using one of several methods, including the estimated fair value of underlying collateral, observable market value of similar debt or discounted expected future cash flows. Collateral values supporting individually evaluated impaired loans are evaluated quarterly. Either appraisals are obtained or appraisal assumptions are updated at least annually unless conditions dictate increased frequency. The Corporation may reduce the collateral value based upon the age of the appraisal and adverse developments in market conditions. Loans which do not meet the criteria to be evaluated individually are evaluated in homogeneous pools of loans with similar risk characteristics. Business loans are assigned to pools based on the Corporation's internal risk rating system. Internal risk ratings are assigned to each business loan at the time of approval and are subjected to subsequent periodic reviews by the Corporation’s senior management, generally at least annually or more frequently upon the occurrence of a circumstance that affects the credit risk of the loan. For business loans not individually evaluated, losses inherent to the pool are estimated by applying standard reserve factors to outstanding principal balances. Standard reserve factors are based on estimated probabilities of default for each internal risk rating, set to a default horizon based on an estimated loss emergence period, and loss given default. These factors are evaluated quarterly and updated annually, unless economic conditions necessitate a change, giving consideration to count-based borrower risk rating migration experience and trends, recent charge-off experience, current economic conditions and trends, changes in collateral values of properties securing loans, and trends with respect to past due and nonaccrual amounts. The allowance for business loans not individually evaluated also includes qualitative adjustments to bring the allowance to the level management believes is appropriate based on factors that have not otherwise been fully accounted for, including adjustments for (i) risk factors that have not been fully addressed in internal risk ratings, (ii) imprecision in the risk rating system resulting from inaccuracy in assigning and/or entering risk ratings in the loan accounting system, (iii) market conditions and (iv) model imprecision. Risk factors that have not been fully addressed in internal risk ratings may include portfolios where recent historical losses exceed expected losses or known recent events are expected to alter risk ratings once evidence is acquired, portfolios where a certain level of concentration introduces added risk, or changes in the level and quality of experience held by lending management. An additional allowance for risk rating errors is calculated based on the results of risk rating accuracy assessments performed on samples of business loans conducted by the Corporation's asset quality review function, a function independent of the lending and credit groups responsible for assigning the initial internal risk rating at the time of approval. Qualitative adjustments for market conditions are determined based on an established framework. The determination of the appropriate adjustment is based on management's analysis of observable macroeconomic metrics, including consideration of regional metrics within the Corporation's footprint, internal credit risk movement and a qualitative assessment of the lending environment, including underwriting standards, current economic and political conditions, and other factors affecting credit quality. Management recognizes the sensitivity of various assumptions made in the quantitative modeling of expected losses and may adjust reserves depending upon the level of uncertainty that currently exists in one or more assumption. In the second quarter 2014, the Corporation enhanced the approach used to determine the standard reserve factors used in estimating the allowance for credit losses, which had the effect of capturing certain elements in the standard reserve component that had formerly been included in the qualitative assessment. The impact of the change was largely neutral to the total allowance for loan losses at June 30, 2014. However, because standard reserves are allocated to the segments at the loan level, while qualitative reserves are allocated at the portfolio level, the impact of the methodology change on the allowance of each segment reflected the characteristics of the individual loans within each segment's portfolio, causing segment reserves to increase or decrease accordingly. In the first quarter 2013, the Corporation enhanced the approach utilized for determining standard reserve factors by changing from a dollar-based migration method for developing probability of default statistics to a count-based method. Under the dollar-based method, each dollar that moved to default received equal weight in the determination of standard reserve factors for each internal risk rating. As a result, the movement of larger loans impacted standard reserve factors more than the movement of smaller loans. By moving to a count-based approach, where each loan that moves to default receives equal weighting, unusually large or small loans will not have a disproportionate influence on the standard reserve factors. The change resulted in a $40 million increase to the allowance for loan losses at March 31, 2013. The allowance for retail loans not individually evaluated is determined by applying estimated loss rates to various pools of loans within the portfolios with similar risk characteristics. Estimated loss rates for all pools are updated quarterly, incorporating factors such as recent charge-off experience, current economic conditions and trends, changes in collateral values of properties securing loans (using index-based estimates), and trends with respect to past due and nonaccrual amounts. Loans acquired in business combinations are initially recorded at fair value, which includes an estimate of credit losses expected to be realized over the remaining lives of the loans, and therefore no corresponding allowance for loan losses is recorded for these loans at acquisition. Methods utilized to estimate any subsequently required allowance for loan losses for acquired loans not deemed credit-impaired at acquisition are similar to originated loans; however, the estimate of loss is based on the unpaid principal balance less any remaining purchase discount. The total allowance for loan losses is sufficient to absorb incurred losses inherent in the total portfolio. Unanticipated economic events, including political, economic and regulatory instability in countries where the Corporation has loans, could cause changes in the credit characteristics of the portfolio and result in an unanticipated increase in the allowance. Significant increases in current portfolio exposures, as well as the inclusion of additional industry-specific portfolio exposures in the allowance, could also increase the amount of the allowance. Any of these events, or some combination thereof, may result in the need for additional provision for credit losses in order to maintain an allowance that complies with credit risk and accounting policies. Loans deemed uncollectible are charged off and deducted from the allowance. Recoveries on loans previously charged off are added to the allowance.
Allowance for Credit Losses on Lending-Related Commitments	Allowance for Credit Losses on Lending-Related Commitments The allowance for credit losses on lending-related commitments provides for probable losses inherent in lending-related commitments, including unused commitments to extend credit and letters of credit. The allowance for credit losses on lending-related commitments includes allowances based on homogeneous pools of letters of credit and unused commitments to extend credit within each internal risk rating. A probability of draw estimate is applied to the commitment amount, and the result is multiplied by standard reserve factors consistent with business loans. In general, the probability of draw for letters of credit is considered certain for all letters of credit supporting loans and for letters of credit assigned an internal risk rating generally consistent with regulatory defined substandard or doubtful. Other letters of credit and all unfunded commitments have a lower probability of draw. The allowance for credit losses on lending-related commitments is included in “accrued expenses and other liabilities” on the consolidated balance sheets, with the corresponding charge reflected in the “provision for credit losses” on the consolidated statements of income.
Nonperforming Loans	A loan is considered past due when the contractually required principal or interest payment is not received by the specified due date or, for certain loans, when a scheduled monthly payment is past due and unpaid for 30 days or more. Business loans are generally placed on nonaccrual status when management determines full collection of principal or interest is unlikely or when principal or interest payments are 90 days past due, unless the loan is fully collateralized and in the process of collection. The past-due status of a business loan is one of many indicative factors considered in determining the collectibility of the credit. The primary driver of when the principal amount of a business loan should be fully or partially charged-off is based on a qualitative assessment of the recoverability of the principal amount from collateral and other cash flow sources. Residential mortgage and home equity loans are generally placed on nonaccrual status once they become 90 days past due and are charged off to current appraised values less costs to sell no later than 180 days past due. In addition, junior lien home equity loans less than 90 days past due are placed on nonaccrual status if they have underlying risk characteristics that place full collection of the loan in doubt, such as when the related senior lien position is identified as seriously delinquent. Residential mortgage and consumer loans in bankruptcy for which the court has discharged the borrower's obligation and the borrower has not reaffirmed the debt are placed on nonaccrual status and written down to estimated collateral value, without regard to the actual payment status of the loan, and are classified as TDRs. All other consumer loans are generally placed on nonaccrual status at 90 days past due and are charged off at no later than 120 days past due, earlier if deemed uncollectible. At the time a loan is placed on nonaccrual status, interest previously accrued but not collected is charged against current income. Principal and interest payments received on such loans are generally first applied as a reduction of principal. Income on nonaccrual loans is then recognized only to the extent that cash is received after principal has been fully repaid or future collection of principal is probable. Generally, a loan may be returned to accrual status when all delinquent principal and interest have been received and the Corporation expects repayment of the remaining contractual principal and interest, or when the loan or debt security is both well secured and in the process of collection. PCI loans are recorded at fair value at acquisition date. Although the PCI loans may be contractually delinquent, the Corporation does not classify these loans as past due or nonperforming as the loans were written down to fair value at the acquisition date and the accretable yield is recognized in interest income over the remaining life of the loan.
Foreclosed Assets	Foreclosed property (primarily real estate) is initially recorded at fair value, less costs to sell, at the date of foreclosure and subsequently carried at the lower of cost or fair value, less estimated costs to sell. Loans are reclassified to foreclosed property upon obtaining legal title to the collateral. Independent appraisals are obtained to substantiate the fair value of foreclosed property at the time of foreclosure and updated at least annually or upon evidence of deterioration in the property’s value. At the time of foreclosure, the adjustment for the difference between the related loan balance and fair value (less estimated costs to sell) of the property acquired is charged or credited to the allowance for loan losses. Subsequent write-downs, operating expenses and losses upon sale, if any, are charged to noninterest expenses. Foreclosed property is included in “accrued income and other assets” on the consolidated balance sheets.
Premises and Equipment	Premises and Equipment Premises and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation, computed on the straight-line method, is charged to operations over the estimated useful lives of the assets. Estimated useful lives are generally 3 years to 33 years for premises that the Corporation owns and 3 years to 8 years for furniture and equipment. Leasehold improvements are generally amortized over the terms of their respective leases or 10 years, whichever is shorter.
Software	Software Capitalized software is stated at cost, less accumulated amortization. Capitalized software includes purchased software and capitalizable application development costs associated with internally-developed software. Amortization, computed on the straight-line method, is charged to operations over 5 years, the estimated useful life of the software. Capitalized software is included in “accrued income and other assets” on the consolidated balance sheets.
Goodwill	Goodwill, included in "accrued income and other assets" on the consolidated balance sheets, is initially recorded as the excess of the purchase price over the fair value of net assets acquired in a business combination and is subsequently evaluated at least annually for impairment. Goodwill impairment testing is performed at the reporting unit level, equivalent to a business segment or one level below. The Corporation has three reporting units: the Business Bank, the Retail Bank and Wealth Management. The Corporation performs its annual evaluation of goodwill impairment in the third quarter of each year and on an interim basis if events or changes in circumstances between annual tests suggest additional testing may be warranted to determine if goodwill might be impaired. The goodwill impairment test is a two-step test. The first step of the goodwill impairment test compares the estimated fair value of identified reporting units with their carrying amount, including goodwill. If the estimated fair value of the reporting unit is less than the carrying value, the second step must be performed to determine the implied fair value of the reporting unit's goodwill and the amount of goodwill impairment, if any. The implied fair value of goodwill is determined as if the reporting unit were being acquired in a business combination. If the implied fair value of goodwill exceeds the goodwill assigned to the reporting unit, there is no impairment. If the goodwill assigned to a reporting unit exceeds the implied fair value of goodwill, an impairment charge would be recorded for the excess. In performing the annual impairment test, the carrying value of each reporting unit is the greater of economic or regulatory capital. The Corporation assigns economic capital using internal management methodologies on the basis of each reporting unit's credit, operational and interest rate risks, as well as goodwill. To determine regulatory capital, each reporting unit is assigned sufficient capital such that their respective Tier 1 ratio, based on allocated risk-weighted assets, is the same as that of the Corporation. Using this two-pronged approach, the Corporation's equity is fully allocated to its reporting units except for capital held primarily for the risk associated with the securities portfolio which is assigned to the Finance segment of the Corporation. The estimated fair values of the reporting units are determined using a blend of two commonly used valuation techniques: the market approach and the income approach. For the market approach, valuations of reporting units consider a combination of earnings, equity and other multiples from companies with characteristics similar to the reporting unit. Since the fair values determined under the market approach are representative of noncontrolling interests, the valuations accordingly incorporate a control premium. For the income approach, estimated future cash flows and terminal value are discounted. Estimated future cash flows are derived from internal forecasts and economic expectations for each reporting unit which incorporate uncertainty factors inherent to long-term projections. The applicable discount rate is based on the imputed cost of equity capital appropriate for each reporting unit, which incorporates the risk-free rate of return, the level of non-diversified risk associated with companies with characteristics similar to the reporting unit, an entity-specific risk premium and a market equity risk premium. Determining the fair value of reporting units is a subjective process involving the use of estimates and judgments related to the selection of inputs such as future cash flows, discount rates, comparable public company multiples, applicable control premiums and economic expectations used in determining the interest rate environment. The Corporation may choose to perform a qualitative assessment to determine whether the first step of the impairment test should be performed in future periods if certain factors indicate that impairment is unlikely. Factors which could be considered in the assessment of the likelihood of impairment include macroeconomic conditions, industry and market considerations, stock performance of the Corporation and its peers, financial performance, events affecting the Corporation as a whole or its reporting units individually and previous results of goodwill impairment tests.
Core Deposit Intangibles	Core deposit intangibles are amortized on an accelerated basis, based on the estimated period the economic benefits are expected to be received. Core deposit intangibles are reviewed for impairment when events or changes in circumstances indicate that their carrying amounts may not be recoverable. Impairment for a finite-lived intangible asset exists if the sum of the undiscounted cash flows expected to result from the use of the asset exceeds its carrying value.
Nonmarketable Equity Securities	Nonmarketable Equity Securities The Corporation has certain investments that are not readily marketable. These investments include a portfolio of investments in indirect private equity and venture capital funds and restricted equity investments, which are securities the Corporation is required to hold for various reasons, primarily Federal Home Loan Bank of Dallas (FHLB) and Federal Reserve Bank (FRB) stock. These investments are accounted for on the cost or equity method and are included in “accrued income and other assets” on the consolidated balance sheets. The investments are individually reviewed for impairment on a quarterly basis. Indirect private equity and venture capital funds are evaluated by comparing the carrying value to the estimated fair value. The amount by which the carrying value exceeds the fair value that is determined to be other-than-temporary impairment is charged to current earnings and the carrying value of the investment is written down accordingly. FHLB and FRB stock are recorded at cost (par value) and evaluated for impairment based on the ultimate recoverability of the par value. If the Corporation does not expect to recover the full par value, the amount by which the par value exceeds the ultimately recoverable value would be charged to current earnings and the carrying value of the investment would be written down accordingly.
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities Derivative instruments are carried at fair value in either “accrued income and other assets” or “accrued expenses and other liabilities” on the consolidated balance sheets. The accounting for changes in the fair value (i.e., gains or losses) of a derivative instrument is determined by whether it has been designated and qualifies as part of a hedging relationship and, further, by the type of hedging relationship. The Corporation presents derivative instruments at fair value in the consolidated balance sheets on a net basis when a right of offset exists, based on transactions with a single counterparty and any cash collateral paid to and/or received from that counterparty for derivative contracts that are subject to legally enforceable master netting arrangements. For derivative instruments designated and qualifying as fair value hedges (i.e., hedging the exposure to changes in the fair value of an asset or a liability or an identified portion thereof that is attributable to a particular risk), the gain or loss on the derivative instrument, as well as the offsetting loss or gain on the hedged item attributable to the hedged risk, are recognized in current earnings during the period of the change in fair values. For derivative instruments that are designated and qualify as cash flow hedges (i.e., hedging the exposure to variability in expected future cash flows that is attributable to a particular risk), the effective portion of the gain or loss on the derivative instrument is reported as a component of other comprehensive income and reclassified into earnings in the same period or periods during which the hedged transaction affects earnings. The remaining gain or loss on the derivative instrument in excess of the cumulative change in the present value of future cash flows of the hedged item (i.e., the ineffective portion), if any, is recognized in current earnings during the period of change. For derivative instruments not designated as hedging instruments, the gain or loss is recognized in current earnings during the period of change. For derivatives designated as hedging instruments at inception, the Corporation uses either the short-cut method or applies statistical regression analysis to assess effectiveness. The short-cut method is used for $400 million notional of fair value hedges of medium and long-term debt issued prior to 2006. This method allows for the assumption of zero hedge ineffectiveness and eliminates the requirement to further assess hedge effectiveness on these transactions. For hedge relationships to which the Corporation does not apply the short-cut method, statistical regression analysis is used at inception and for each reporting period thereafter to assess whether the derivative used has been and is expected to be highly effective in offsetting changes in the fair value or cash flows of the hedged item. All components of each derivative instrument’s gain or loss are included in the assessment of hedge effectiveness. Net hedge ineffectiveness is recorded in “other noninterest income” on the consolidated statements of income.
Derivative Instruments Fair Value Amounts Offset	The Corporation presents derivative instruments at fair value in the consolidated balance sheets on a net basis when a right of offset exists, based on transactions with a single counterparty and any cash collateral paid to and/or received from that counterparty for derivative contracts that are subject to legally enforceable master netting arrangements.
Short-Term Borrowings	Short-Term Borrowings Securities sold under agreements to repurchase are treated as collateralized borrowings and are recorded at amounts equal to the cash received. The contractual terms of the agreements to repurchase may require the Corporation to provide additional collateral if the fair value of the securities underlying the borrowings declines during the term of the agreement.
Financial Guarantees	Financial Guarantees Certain guarantee contracts or indemnification agreements that contingently require the Corporation, as guarantor, to make payments to the guaranteed party are initially measured at fair value and included in “accrued expenses and other liabilities” on the consolidated balance sheets. The subsequent accounting for the liability depends on the nature of the underlying guarantee. The release from risk is accounted for under a particular guarantee when the guarantee expires or is settled, or by a systematic and rational amortization method.
Share-Based Compensation	Share-Based Compensation The Corporation recognizes share-based compensation expense using the straight-line method over the requisite service period for all stock awards, including those with graded vesting. The requisite service period is the period an employee is required to provide service in order to vest in the award, which cannot extend beyond the date at which the employee is no longer required to perform any service to receive the share-based compensation (the retirement-eligible date). Certain awards are contingent upon performance and/or market conditions, which affect the number of shares ultimately issued. The Corporation periodically evaluates the probable outcome of the performance conditions and makes cumulative adjustments to compensation expense as appropriate. Market conditions are included in the determination of the fair value of the award on the date of grant. Subsequent to the grant date, market conditions have no impact on the amount of compensation expense the Corporation will recognize over the life of the award.
Revenue Recognition	Revenue Recognition The following summarizes the Corporation’s revenue recognition policies as they relate to certain noninterest income line items in the consolidated statements of income. Card fees includes primarily bankcard interchange revenue which is recorded as revenue when earned. Effective January 1, 2015, the Corporation entered into a new contract for an existing debit card program. Guidance provided in Accounting Standards Code 605-45, " Principal Agent Considerations," indicates whether revenue should be reported gross or net for this type of arrangement. Management assessed various principal versus agent indicators provided in the guidance and concluded that the Corporation bears the risks and rewards of providing the services for the card program based on the new contract terms and, therefore, gross presentation of revenues and expenses is appropriate. This change in presentation resulted in increases of $181 million to both "card fees" in noninterest income and "outside processing fee expense" in noninterest expenses for the year ended December 31, 2015. Service charges on deposit accounts include fees for banking services provided, overdrafts and non-sufficient funds. Revenue is generally recognized in accordance with published deposit account agreements for retail accounts or contractual agreements for commercial accounts. Fiduciary income includes fees and commissions from asset management, custody, recordkeeping, investment advisory and other services provided to personal and institutional trust customers. Revenue is recognized on an accrual basis at the time the services are performed and are based on either the market value of the assets managed or the services provided. Commercial lending fees primarily include fees assessed on the unused portion of commercial lines of credit ("unused commitment fees") and syndication agent fees. Unused commitment fees are recognized when earned. Syndication agent fees are generally recognized when the transaction is complete.
Defined Benefit Pension and Other Postretirement Costs	Defined Benefit Pension and Other Postretirement Costs Defined benefit pension costs are included in “salaries and benefits expense" on the consolidated statements of income and are funded consistent with the requirements of federal laws and regulations. Inherent in the determination of defined benefit pension costs are assumptions concerning future events that will affect the amount and timing of required benefit payments under the plans. These assumptions include demographic assumptions such as retirement age and mortality, a compensation rate increase, a discount rate used to determine the current benefit obligation and a long-term expected rate of return on plan assets. Net periodic defined benefit pension expense includes service cost, interest cost based on the assumed discount rate, an expected return on plan assets based on an actuarially derived market-related value of assets, amortization of prior service cost and amortization of net actuarial gains or losses. The market-related value of plan assets is determined by amortizing the current year’s investment gains and losses (the actual investment return net of the expected investment return) over 5 years. The amortization adjustment cannot exceed 10 percent of the fair value of assets. Prior service costs include the impact of plan amendments on the liabilities and are amortized over the future service periods of active employees expected to receive benefits under the plan. Actuarial gains and losses result from experience different from that assumed and from changes in assumptions (excluding asset gains and losses not yet reflected in market-related value). Amortization of actuarial gains and losses is included as a component of net periodic defined benefit pension cost for a year if the actuarial net gain or loss exceeds 10 percent of the greater of the projected benefit obligation or the market-related value of plan assets. If amortization is required, the excess is amortized over the average remaining service period of participating employees expected to receive benefits under the plan. Postretirement benefits are recognized in “salaries and benefits expense" on the consolidated statements of income during the average remaining service period of participating employees expected to receive benefits under the plan or the average remaining future lifetime of retired participants currently receiving benefits under the plan.
Income Taxes	Income Taxes The provision for income taxes is the sum of income taxes due for the current year and deferred taxes. Deferred taxes arise from temporary differences between the income tax basis and financial accounting basis of assets and liabilities. Deferred tax assets are evaluated for realization based on available evidence of loss carry-back capacity, future reversals of existing taxable temporary differences, and assumptions made regarding future events. A valuation allowance is provided when it is more likely than not that some portion of the deferred tax asset will not be realized. The Corporation classifies interest and penalties on income tax liabilities in the “provision for income taxes” on the consolidated statements of income.
Earnings Per Share	Earnings Per Share Basic net income per common share is calculated using the two-class method. The two-class method is an earnings allocation formula that determines earnings per share for each share of common stock and participating securities according to dividends declared (distributed earnings) and participation rights in undistributed earnings. Distributed and undistributed earnings are allocated between common and participating security shareholders based on their respective rights to receive dividends. Nonvested share-based payment awards that contain nonforfeitable rights to dividends or dividend equivalents are considered participating securities (e.g., nonvested restricted stock and service-based restricted stock units). Undistributed net losses are not allocated to nonvested restricted shareholders, as these shareholders do not have a contractual obligation to fund the losses incurred by the Corporation. Net income attributable to common shares is then divided by the weighted-average number of common shares outstanding during the period. Diluted net income per common share is calculated using the more dilutive of either the treasury method or the two-class method. The dilutive calculation considers common stock issuable under the assumed exercise of stock options and performance-based restricted stock units granted under the Corporation’s stock plans and warrants using the treasury stock method, if dilutive. Net income attributable to common shares is then divided by the total of weighted-average number of common shares and common stock equivalents outstanding during the period.
Statements Of Cash Flows	Statements of Cash Flows Cash and cash equivalents are defined as those amounts included in “cash and due from banks”, “federal funds sold” and “interest-bearing deposits with banks” on the consolidated balance sheets.
Comprehensive Income (Loss)	Comprehensive Income (Loss) The Corporation presents on an annual basis the components of net income and other comprehensive income in two separate, but consecutive statements and presents on an interim basis the components of net income and a total for comprehensive income in one continuous consolidated statement of comprehensive income.
Pending Accounting Pronouncements	Pending Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, “Revenue from Contracts with Customers (Topic 606),” (ASU 2014-09), which is intended to improve and converge the financial reporting requirements for revenue contracts with customers. Previous GAAP comprised broad revenue recognition concepts along with numerous industry-specific requirements. The new guidance establishes a five-step model which entities must follow to recognize revenue and removes inconsistencies and weaknesses in existing guidance. The guidance under ASU 2014-09 is effective for annual and interim periods beginning after December 15, 2017, and must be retrospectively applied. Entities will have the option of presenting prior periods as impacted by the new guidance or presenting the cumulative effect of initial application along with supplementary disclosures. Early adoption is permitted, but not before annual and interim periods beginning after December 15, 2016. The Corporation is currently evaluating the impact of adopting ASU 2014-09. In February 2015, the FASB issued ASU No. 2015-02, "Consolidation (Topic 810): Amendments to the Consolidation Analysis," (ASU 2015-02), which makes targeted amendments to the considerations applied by reporting entities when determining if a legal entity should be consolidated, including placing more emphasis on risk of loss when determining a controlling financial interest. Low-income housing tax credit investments that meet the criteria for the proportional amortization method are not impacted by these amendments. ASU 2015-02 is effective for annual and interim periods beginning after December 15, 2015, and must be retrospectively applied. Early adoption is permitted. The adoption of the ASU will have no impact to the Corporation's financial condition or results of operations. In April 2015, the FASB issued ASU No. 2015-05, "Goodwill and Other - Internal-Use Software (Subtopic 350-40)," (ASU 2015-05), which defines specific criteria entities must apply to determine if a cloud computing arrangement includes an in-substance software license. The result of the assessment will direct the entity to apply either software licensing or service contract guidance to record the related costs. ASU 2015-05 is effective for annual and interim periods beginning after December 15, 2015, and can be prospectively or retrospectively applied. Early adoption is permitted. The adoption of the ASU is expected to have an immaterial impact to the Corporation's financial condition or results of operations. In May 2015, the FASB issued ASU No. 2015-07, “Fair Value Measurement (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent),” (ASU 2015-07), which amends disclosure requirements for entities that utilize net asset value per share (or its equivalent) to measure fair value as a practical expedient. The update eliminates the requirement to classify these investments within the fair value hierarchy and instead requires disclosure of sufficient information about these investments to permit reconciliation of the fair value of investments categorized within the fair value hierarchy to the investments presented in the consolidated balance sheet. ASU 2015-07 is effective for annual and interim periods beginning after December 15, 2015 and must be applied retrospectively. Early adoption is permitted. The adoption of ASU 2015-07 will impact disclosures, but will have no impact on the Corporation's financial condition or results of operations. In January, 2016, the FASB issued ASU No. 2016-01, "Financial Instruments - Overall (Subtopic 825-10): Recognition of Financial Assets and Financial Liabilities," (ASU 2016-01), which makes targeted amendments to fair value measurement and disclosure guidance. ASU 2016-01 requires equity investments (other than equity method investments) to be measured at fair value with changes in fair value recognized in net income. This change is only applied if a readily determinable fair value can be obtained. The update also requires the use of exit prices to measure fair value for disclosure purposes as well as other enhanced disclosure requirements. The guidance under ASU 2016-01 is effective for annual and interim periods beginning after December 15, 2017, and early adoption is generally not permitted. At adoption on January 1, 2018, cumulative net unrealized gains and losses on equity investments other than equity method investments will be recognized as an adjustment to beginning retained earnings and accumulated other comprehensive income (loss). Amendments related to equity securities without a readily determinable fair value will be applied prospectively. The Corporation is currently evaluating the impact of adopting ASU 2016-01.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Assets And Liabilities Recorded At Fair Value On A Recurring Basis	The following tables present the recorded amount of assets and liabilities measured at fair value on a recurring basis as of December 31, 2015 and 2014 . (in millions) Total Level 1 Level 2 Level 3 December 31, 2015 Trading securities: Deferred compensation plan assets $ 89 $ 89 $ — $ — Equity and other non-debt securities 3 3 — — Total trading securities 92 92 — — Investment securities available-for-sale: U.S. Treasury and other U.S. government agency securities 2,763 2,763 — — Residential mortgage-backed securities (a) 7,545 — 7,545 — State and municipal securities 9 — — 9 (b) Corporate debt securities 1 — — 1 (b) Equity and other non-debt securities 201 134 — 67 (b) Total investment securities available-for-sale 10,519 2,897 7,545 77 Derivative assets: Interest rate contracts 286 — 277 9 Energy derivative contracts 475 — 475 — Foreign exchange contracts 57 — 57 — Warrants 2 — — 2 Total derivative assets 820 — 809 11 Total assets at fair value $ 11,431 $ 2,989 $ 8,354 $ 88 Derivative liabilities: Interest rate contracts $ 92 $ — $ 92 $ — Energy derivative contracts 472 — 472 — Foreign exchange contracts 46 — 46 — Total derivative liabilities 610 — 610 — Deferred compensation plan liabilities 89 89 — — Total liabilities at fair value $ 699 $ 89 $ 610 $ — (a) Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises. (b) Auction-rate securities. (in millions) Total Level 1 Level 2 Level 3 December 31, 2014 Trading securities: Deferred compensation plan assets $ 94 $ 94 $ — $ — Investment securities available-for-sale: U.S. Treasury and other U.S. government agency securities 526 526 — — Residential mortgage-backed securities (a) 7,274 — 7,274 — State and municipal securities 23 — — 23 (b) Corporate debt securities 51 — 50 1 (b) Equity and other non-debt securities 242 130 — 112 (b) Total investment securities available-for-sale 8,116 656 7,324 136 Derivative assets: Interest rate contracts 328 — 328 — Energy derivative contracts 527 — 527 — Foreign exchange contracts 39 — 39 — Warrants 4 — — 4 Total derivative assets 898 — 894 4 Total assets at fair value $ 9,108 $ 750 $ 8,218 $ 140 Derivative liabilities: Interest rate contracts $ 102 $ — $ 102 $ — Energy derivative contracts 525 — 525 — Foreign exchange contracts 34 — 34 — Total derivative liabilities 661 — 661 — Deferred compensation plan liabilities 94 94 — — Total liabilities at fair value $ 755 $ 94 $ 661 $ — (a) Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises. (b) Auction-rate securities.
Changes In Level 3 Assets And Liabilities Measured At Fair Value On A Recurring Basis	The following table summarizes the changes in Level 3 assets measured at fair value on a recurring basis for the years ended December 31, 2015 and 2014 . Net Realized/Unrealized Gains (Losses) (Pretax) Balance at Beginning of Period Recorded in Earnings Recorded in Other Comprehensive Income (Loss) Balance at End of Period (in millions) Realized Unrealized Sales Year Ended December 31, 2015 Investment securities available-for-sale: State and municipal securities (a) $ 23 $ — $ — $ — $ (14 ) $ 9 Corporate debt securities (a) 1 — — — — 1 Equity and other non-debt securities (a) 112 (2 ) (b) — 1 (c) (44 ) 67 Total investment securities 136 (2 ) (b) — 1 (c) (58 ) 77 Derivative assets: Interest rate contracts — — 9 (d) — — 9 Warrants 4 6 (d) (1 ) (d) — (7 ) 2 Year Ended December 31, 2014 Investment securities available-for-sale: State and municipal securities (a) $ 22 $ — $ — $ 1 (c) $ — $ 23 Corporate debt securities (a) 1 — — — — 1 Equity and other non-debt securities (a) 136 2 (b) — 7 (c) (33 ) 112 Total investment securities 159 2 (b) — 8 (c) (33 ) 136 Derivative assets: Warrants 3 7 (d) 1 (d) — (7 ) 4 (a) Auction-rate securities. (b) Realized and unrealized gains and losses due to changes in fair value recorded in "net securities losses" on the consolidated statements of income. (c) Recorded in "net unrealized (losses) gains on investment securities available-for-sale" in other comprehensive income. (d) Realized and unrealized gains and losses due to changes in fair value recorded in "other noninterest income" on the consolidated statements of income.
Assets And Liabilities Recorded At Fair Value On A Nonrecurring Basis	The following table presents assets recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014 . No liabilities were recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014 . (in millions) Total Level 2 Level 3 December 31, 2015 Loans held-for-sale: Commercial $ 8 $ 8 $ — Loans: Commercial 134 — 134 Commercial mortgage 11 — 11 International 8 — 8 Total loans 153 — 153 Nonmarketable equity securities 1 — 1 Other real estate 2 — 2 Total assets at fair value $ 164 $ 8 $ 156 December 31, 2014 Loans: Commercial $ 38 $ — $ 38 Commercial mortgage 26 — 26 Total loans 64 — 64 Nonmarketable equity securities 2 — 2 Other real estate 2 — 2 Total assets at fair value $ 68 $ — $ 68
Quantitative Information About Level 3 Measurements	The following table presents quantitative information related to the significant unobservable inputs utilized in the Corporation's Level 3 recurring fair value measurement as of December 31, 2015 and December 31, 2014 . The Corporation's Level 3 recurring fair value measurements include auction-rate securities where fair value is determined using an income approach based on a discounted cash flow model. The inputs in the table below reflect management's expectation of continued illiquidity in the secondary auction-rate securities market due to a lack of market activity for the issuers remaining in the portfolio, a lack of market incentives for issuer redemptions, and the expectation for a continuing low interest rate environment. The December 31, 2015 workout periods reflect management's expectation of the pace at which short-term interest rates could rise. Discounted Cash Flow Model Unobservable Input Fair Value (in millions) Discount Rate Workout Period (in years) December 31, 2015 State and municipal securities (a) $ 9 3% - 8% 1 - 2 Equity and other non-debt securities (a) 67 4% - 9% 1 December 31, 2014 State and municipal securities (a) $ 23 3% - 9% 1 - 3 Equity and other non-debt securities (a) 112 4% - 8% 1 - 2 (a) Auction-rate securities.
Estimated Fair Values Of Financial Instruments Not Recorded At Fair Value In Their Entirety On A Recurring Basis	The carrying amount and estimated fair value of financial instruments not recorded at fair value in their entirety on a recurring basis on the Corporation’s consolidated balance sheets are as follows: Carrying Amount Estimated Fair Value (in millions) Total Level 1 Level 2 Level 3 December 31, 2015 Assets Cash and due from banks $ 1,157 $ 1,157 $ 1,157 $ — $ — Interest-bearing deposits with banks 4,990 4,990 4,990 — — Investment securities held-to-maturity 1,981 1,973 — 1,973 — Loans held-for-sale (a) 21 21 — 21 — Total loans, net of allowance for loan losses (b) 48,450 48,269 — — 48,269 Customers’ liability on acceptances outstanding 5 5 5 — — Nonmarketable equity securities (c) 10 18 — — 18 Restricted equity investments 92 92 92 — — Liabilities Demand deposits (noninterest-bearing) 30,839 30,839 — 30,839 — Interest-bearing deposits 25,462 25,462 — 25,462 — Customer certificates of deposit 3,552 3,536 — 3,536 — Total deposits 59,853 59,837 — 59,837 — Short-term borrowings 23 23 23 — — Acceptances outstanding 5 5 5 — — Medium- and long-term debt 3,058 3,032 — 3,032 — Credit-related financial instruments (83 ) (83 ) — — (83 ) December 31, 2014 Assets Cash and due from banks $ 1,026 $ 1,026 $ 1,026 $ — $ — Interest-bearing deposits with banks 5,045 5,045 5,045 — — Investment securities held-to-maturity 1,935 1,933 — 1,933 — Loans held-for-sale (a) 5 5 — 5 — Total loans, net of allowance for loan losses (b) 47,999 47,932 — — 47,932 Customers’ liability on acceptances outstanding 10 10 10 — — Nonmarketable equity securities (c) 11 18 — — 18 Restricted equity investments 92 92 92 — — Liabilities Demand deposits (noninterest-bearing) 27,224 27,224 — 27,224 — Interest-bearing deposits 25,841 25,841 — 25,841 — Customer certificates of deposit 4,421 4,411 — 4,411 — Total deposits 57,486 57,476 — 57,476 — Short-term borrowings 116 116 116 — — Acceptances outstanding 10 10 10 — — Medium- and long-term debt 2,675 2,681 — 2,681 — Credit-related financial instruments (85 ) (85 ) — — (85 ) (a) Included $8 million and no impaired loans held-for-sale recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014 , respectively. (b) Included $153 million and $64 million of impaired loans recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014 , respectively. (c) Included $1 million and $2 million of nonmarketable equity securities recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014 , respectively.

Investment Securities (Tables)

Investment Securities (Tables)	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Summary Of Investment Securities	A summary of the Corporation’s investment securities follows: (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value December 31, 2015 Investment securities available-for-sale: U.S. Treasury and other U.S. government agency securities $ 2,769 $ 1 $ 7 $ 2,763 Residential mortgage-backed securities (a) 7,513 76 44 7,545 State and municipal securities 9 — — 9 Corporate debt securities 1 — — 1 Equity and other non-debt securities 199 2 — 201 Total investment securities available-for-sale (b) $ 10,491 $ 79 $ 51 $ 10,519 Investment securities held-to-maturity (c): Residential mortgage-backed securities (a) $ 1,981 $ 2 $ 10 $ 1,973 December 31, 2014 Investment securities available-for-sale: U.S. Treasury and other U.S. government agency securities $ 526 $ — $ — $ 526 Residential mortgage-backed securities (a) 7,192 122 40 7,274 State and municipal securities 24 — 1 23 Corporate debt securities 51 — — 51 Equity and other non-debt securities 242 1 1 242 Total investment securities available-for-sale (b) $ 8,035 $ 123 $ 42 $ 8,116 Investment securities held-to-maturity (c): Residential mortgage-backed securities (a) $ 1,935 $ — $ 2 $ 1,933 (a) Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises. (b) Included auction-rate securities at amortized cost and fair value of $76 million and $77 million , respectively, as of December 31, 2015 and $137 million and $136 million , respectively, as of December 31, 2014 . (c) The amortized cost of investment securities held-to-maturity included net unrealized losses of $15 million at December 31, 2015 and $23 million at December 31, 2014 related to securities transferred from available-for-sale, which are included in accumulated other comprehensive loss.
Summary Of Investment Securities In Unrealized Loss Positions	A summary of the Corporation’s investment securities in an unrealized loss position as of December 31, 2015 and 2014 follows: Temporarily Impaired Less than 12 Months 12 Months or more Total (in millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses December 31, 2015 U.S. Treasury and other U.S. government agency securities $ 2,265 $ 7 $ — $ — $ 2,265 $ 7 Residential mortgage-backed securities (a) 2,665 21 1,976 51 4,641 72 State and municipal securities (b) — — 9 — (c) 9 — (c) Corporate debt securities (b) — — 1 — (c) 1 — (c) Equity and other non-debt securities (b) 14 — (c) — — 14 — (c) Total impaired securities $ 4,944 $ 28 $ 1,986 $ 51 $ 6,930 $ 79 December 31, 2014 U.S. Treasury and other U.S. government agency securities $ 298 $ — (c) $ — $ — $ 298 $ — (c) Residential mortgage-backed securities (a) 626 3 3,112 71 3,738 74 State and municipal securities (b) — — 22 1 22 1 Corporate debt securities (b) — — 1 — (c) 1 — (c) Equity and other non-debt securities (b) — — 112 1 112 1 Total impaired securities $ 924 $ 3 $ 3,247 $ 73 $ 4,171 $ 76 (a) Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises. (b) Primarily auction-rate securities. (c) Unrealized losses less than $0.5 million.
Summary of Net Securities Gains (Losses)	Sales, calls and write-downs of investment securities available-for-sale resulted in the following gains and losses recorded in “net securities losses” on the consolidated statements of income, computed based on the adjusted cost of the specific security. (in millions) Years Ended December 31 2015 2014 2013 Securities gains $ — $ 2 $ 1 Securities losses (2 ) (2 ) (2 ) Net securities losses $ (2 ) $ — $ (1 )
Contractual Maturity Distribution Of Debt Securities	The following table summarizes the amortized cost and fair values of debt securities by contractual maturity. Securities with multiple maturity dates are classified in the period of final maturity. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. (in millions) Available-for-sale Held-to-maturity December 31, 2015 Amortized Cost Fair Value Amortized Cost Fair Value Contractual maturity Within one year $ 10 $ 10 $ — $ — After one year through five years 2,857 2,851 — — After five years through ten years 1,268 1,308 — — After ten years 6,157 6,149 1,981 1,973 Subtotal 10,292 10,318 1,981 1,973 Equity and other non-debt securities 199 201 — — Total investment securities $ 10,491 $ 10,519 $ 1,981 $ 1,973

Credit Quality And Allowance 37

Credit Quality And Allowance For Credit Losses (Tables)	12 Months Ended
	Dec. 31, 2015
Credit Quality And Allowance For Credit Losses [Abstract]
Aging Analysis Of Loans	The following table presents an aging analysis of the recorded balance of loans. Loans Past Due and Still Accruing (in millions) 30-59 Days 60-89 Days 90 Days or More Total Nonaccrual Loans Current Loans Total Loans December 31, 2015 Business loans: Commercial $ 46 $ 12 $ 13 $ 71 $ 238 $ 31,350 $ 31,659 Real estate construction: Commercial Real Estate business line (a) 5 — — 5 — 1,676 1,681 Other business lines (b) 3 — — 3 1 316 320 Total real estate construction 8 — — 8 1 1,992 2,001 Commercial mortgage: Commercial Real Estate business line (a) 7 — 1 8 16 2,080 2,104 Other business lines (b) 7 5 3 15 44 6,814 6,873 Total commercial mortgage 14 5 4 23 60 8,894 8,977 Lease financing — — — — 6 718 724 International 2 — — 2 8 1,358 1,368 Total business loans 70 17 17 104 313 44,312 44,729 Retail loans: Residential mortgage 26 1 — 27 27 1,816 1,870 Consumer: Home equity 5 3 — 8 27 1,685 1,720 Other consumer 7 — — 7 — 758 765 Total consumer 12 3 — 15 27 2,443 2,485 Total retail loans 38 4 — 42 54 4,259 4,355 Total loans $ 108 $ 21 $ 17 $ 146 $ 367 $ 48,571 $ 49,084 December 31, 2014 Business loans: Commercial $ 58 $ 13 $ 1 $ 72 $ 109 $ 31,339 $ 31,520 Real estate construction: Commercial Real Estate business line (a) 3 — — 3 1 1,602 1,606 Other business lines (b) 12 — — 12 1 336 349 Total real estate construction 15 — — 15 2 1,938 1,955 Commercial mortgage: Commercial Real Estate business line (a) 8 1 1 10 22 1,758 1,790 Other business lines (b) 16 12 2 30 73 6,711 6,814 Total commercial mortgage 24 13 3 40 95 8,469 8,604 Lease financing — — — — — 805 805 International 9 — — 9 — 1,487 1,496 Total business loans 106 26 4 136 206 44,038 44,380 Retail loans: Residential mortgage 9 2 — 11 36 1,784 1,831 Consumer: Home equity 5 3 — 8 30 1,620 1,658 Other consumer 12 — 1 13 1 710 724 Total consumer 17 3 1 21 31 2,330 2,382 Total retail loans 26 5 1 32 67 4,114 4,213 Total loans $ 132 $ 31 $ 5 $ 168 $ 273 $ 48,152 $ 48,593 (a) Primarily loans to real estate developers. (b) Primarily loans secured by owner-occupied real estate.
Loans By Credit Quality Indicator	The following table presents loans by credit quality indicator, based on internal risk ratings assigned to each business loan at the time of approval and subjected to subsequent reviews, generally at least annually, and to pools of retail loans with similar risk characteristics. Internally Assigned Rating (in millions) Pass (a) Special Mention (b) Substandard (c) Nonaccrual (d) Total December 31, 2015 Business loans: Commercial $ 29,117 $ 1,293 $ 1,011 $ 238 $ 31,659 Real estate construction: Commercial Real Estate business line (e) 1,681 — — — 1,681 Other business lines (f) 318 1 — 1 320 Total real estate construction 1,999 1 — 1 2,001 Commercial mortgage: Commercial Real Estate business line (e) 2,031 31 26 16 2,104 Other business lines (f) 6,536 172 121 44 6,873 Total commercial mortgage 8,567 203 147 60 8,977 Lease financing 693 17 8 6 724 International 1,245 59 56 8 1,368 Total business loans 41,621 1,573 1,222 313 44,729 Retail loans: Residential mortgage 1,828 2 13 27 1,870 Consumer: Home equity 1,687 1 5 27 1,720 Other consumer 755 3 7 — 765 Total consumer 2,442 4 12 27 2,485 Total retail loans 4,270 6 25 54 4,355 Total loans $ 45,891 $ 1,579 $ 1,247 $ 367 $ 49,084 December 31, 2014 Business loans: Commercial $ 30,310 $ 560 $ 541 $ 109 $ 31,520 Real estate construction: Commercial Real Estate business line (e) 1,594 11 — 1 1,606 Other business lines (f) 336 7 5 1 349 Total real estate construction 1,930 18 5 2 1,955 Commercial mortgage: Commercial Real Estate business line (e) 1,652 69 47 22 1,790 Other business lines (f) 6,434 138 169 73 6,814 Total commercial mortgage 8,086 207 216 95 8,604 Lease financing 778 26 1 — 805 International 1,468 15 13 — 1,496 Total business loans 42,572 826 776 206 44,380 Retail loans: Residential mortgage 1,790 2 3 36 1,831 Consumer: Home equity 1,620 — 8 30 1,658 Other consumer 718 3 2 1 724 Total consumer 2,338 3 10 31 2,382 Total retail loans 4,128 5 13 67 4,213 Total loans $ 46,700 $ 831 $ 789 $ 273 $ 48,593 (a) Includes all loans not included in the categories of special mention, substandard or nonaccrual. (b) Special mention loans are accruing loans that have potential credit weaknesses that deserve management’s close attention, such as loans to borrowers who may be experiencing financial difficulties that may result in deterioration of repayment prospects from the borrower at some future date. This category is generally consistent with the "special mention" category as defined by regulatory authorities. (c) Substandard loans are accruing loans that have a well-defined weakness, or weaknesses, such as loans to borrowers who may be experiencing losses from operations or inadequate liquidity of a degree and duration that jeopardizes the orderly repayment of the loan. Substandard loans also are distinguished by the distinct possibility of loss in the future if these weaknesses are not corrected. PCI loans are included in the substandard category. This category is generally consistent with the "substandard" category as defined by regulatory authorities. (d) Nonaccrual loans are loans for which the accrual of interest has been discontinued. For further information regarding nonaccrual loans, refer to the Nonperforming Assets subheading in Note 1 - Basis of Presentation and Accounting Policies. A significant majority of nonaccrual loans are generally consistent with the "substandard" category and the remainder are generally consistent with the "doubtful" category as defined by regulatory authorities. (e) Primarily loans to real estate developers. (f) Primarily loans secured by owner-occupied real estate.
Schedule Of Nonaccrual, Reduced-Rate Loans And Foreclosed Property	The following table summarizes nonperforming assets. (in millions) December 31, 2015 December 31, 2014 Nonaccrual loans $ 367 $ 273 Reduced-rate loans (a) 12 17 Total nonperforming loans 379 290 Foreclosed property 12 10 Total nonperforming assets $ 391 $ 300 (a) There were no reduced-rate business loans at both December 31, 2015 and at December 31, 2014 . Reduced-rate retail loans totaled $12 million and $17 million at December 31, 2015 and 2014 , respectively.
Changes In The Allowance For Loan Losses And Related Loan Amounts	The following table details the changes in the allowance for loan losses and related loan amounts. 2015 2014 2013 (in millions) Business Loans Retail Loans Total Business Loans Retail Loans Total Business Loans Retail Loans Total Years Ended December 31 Allowance for loan losses: Balance at beginning of period $ 534 $ 60 $ 594 $ 531 $ 67 $ 598 $ 552 $ 77 $ 629 Loan charge-offs (157 ) (11 ) (168 ) (87 ) (15 ) (102 ) (130 ) (23 ) (153 ) Recoveries on loans previously charged-off 55 13 68 68 9 77 70 10 80 Net loan (charge-offs) recoveries (102 ) 2 (100 ) (19 ) (6 ) (25 ) (60 ) (13 ) (73 ) Provision for loan losses 149 (7 ) 142 23 (1 ) 22 39 3 42 Foreign currency translation adjustment (2 ) — (2 ) (1 ) — (1 ) — — — Balance at end of period $ 579 $ 55 $ 634 $ 534 $ 60 $ 594 $ 531 $ 67 $ 598 As a percentage of total loans 1.30 % 1.26 % 1.29 % 1.20 % 1.43 % 1.22 % 1.28 % 1.70 % 1.32 % December 31 Allowance for loan losses: Individually evaluated for impairment $ 53 $ — $ 53 $ 39 $ — $ 39 $ 57 $ — $ 57 Collectively evaluated for impairment 526 55 581 495 60 555 474 67 541 Total allowance for loan losses $ 579 $ 55 $ 634 $ 534 $ 60 $ 594 $ 531 $ 67 $ 598 Loans: Individually evaluated for impairment $ 393 $ 31 $ 424 $ 177 $ 42 $ 219 $ 223 $ 51 $ 274 Collectively evaluated for impairment 44,336 4,323 48,659 44,203 4,169 48,372 41,311 3,880 45,191 PCI loans (a) — 1 1 — 2 2 2 3 5 Total loans evaluated for impairment $ 44,729 $ 4,355 $ 49,084 $ 44,380 $ 4,213 $ 48,593 $ 41,536 $ 3,934 $ 45,470 (a) No allowance for loan losses was required for PCI loans at December 31, 2015 , 2014 and 2013 .
Changes In the Allowance For Credit Losses On Lending-Related Commitments	Changes in the allowance for credit losses on lending-related commitments, included in "accrued expenses and other liabilities" on the consolidated balance sheets, are summarized in the following table. (in millions) Years Ended December 31 2015 2014 2013 Balance at beginning of period $ 41 $ 36 $ 32 Charge-offs on lending-related commitments (a) (1 ) — — Provision for credit losses on lending-related commitments 5 5 4 Balance at end of period $ 45 $ 41 $ 36 (a) Charge-offs result from the sale of unfunded lending-related commitments.
Individually Evaluated Impaired Loans	The following table presents additional information regarding individually evaluated impaired loans. Recorded Investment In: (in millions) Impaired Loans with No Related Allowance Impaired Loans with Related Allowance Total Impaired Loans Unpaid Principal Balance Related Allowance for Loan Losses December 31, 2015 Business loans: Commercial $ 82 $ 252 $ 334 $ 549 $ 45 Commercial mortgage: Commercial Real Estate business line (a) 7 8 15 38 1 Other business lines (b) 2 32 34 55 5 Total commercial mortgage 9 40 49 93 6 International — 10 10 17 2 Total business loans 91 302 393 659 53 Retail loans: Residential mortgage 13 — 13 13 — Consumer: Home equity 12 — 12 16 — Other consumer 6 — 6 10 — Total consumer 18 — 18 26 — Total retail loans (c) 31 — 31 39 — Total individually evaluated impaired loans $ 122 $ 302 $ 424 $ 698 $ 53 December 31, 2014 Business loans: Commercial $ 7 $ 103 $ 110 $ 148 $ 29 Real estate construction: Other business lines (b) — 1 1 1 — Commercial mortgage: Commercial Real Estate business line (a) — 19 19 41 8 Other business lines (b) 4 43 47 63 2 Total commercial mortgage 4 62 66 104 10 Total business loans 11 166 177 253 39 Retail loans: Residential mortgage 25 — 25 28 — Consumer: Home equity 12 — 12 16 — Other consumer 5 — 5 7 — Total consumer 17 — 17 23 — Total retail loans (c) 42 — 42 51 — Total individually evaluated impaired loans $ 53 $ 166 $ 219 $ 304 $ 39 (a) Primarily loans to real estate developers. (b) Primarily loans secured by owner-occupied real estate. (c) Individually evaluated retail loans had no related allowance for loan losses, primarily due to policy which results in direct write-downs of restructured retail loans.
Average Individually Evaluated Impaired Loans And Related Interest Recognized	The following table presents information regarding average individually evaluated impaired loans and the related interest recognized. Interest income recognized for the period primarily related to reduced-rate loans. Individually Evaluated Impaired Loans 2015 2014 2013 (in millions) Average Balance for the Period Interest Income Recognized for the Period Average Balance for the Period Interest Income Recognized for the Period Average Balance for the Period Interest Income Recognized for the Period Years Ended December 31 Business loans: Commercial $ 206 $ 5 $ 77 $ 2 $ 99 $ 2 Real estate construction: Commercial Real Estate business line (a) — — 14 — 25 — Commercial mortgage: Commercial Real Estate business line (a) 16 — 48 — 81 — Other business lines (b) 39 1 64 2 105 3 Total commercial mortgage 55 1 112 2 186 3 International 6 — 2 — 1 — Total business loans 267 6 205 4 311 5 Retail loans: Residential mortgage 21 — 30 — 35 — Consumer: Home equity 12 — 12 — 8 — Other consumer 6 — 4 — 4 — Total consumer 18 — 16 — 12 — Total retail loans 39 — 46 — 47 — Total individually evaluated impaired loans $ 306 $ 6 $ 251 $ 4 $ 358 $ 5 (a) Primarily loans to real estate developers. (b) Primarily loans secured by owner-occupied real estate.
Troubled Debt Restructurings By Type Of Modification	The following tables detail the recorded balance at December 31, 2015 and 2014 of loans considered to be TDRs that were restructured during the years ended December 31, 2015 and 2014 , by type of modification. In cases of loans with more than one type of modification, the loans were categorized based on the most significant modification. 2015 2014 Type of Modification Type of Modification (in millions) Principal Deferrals (a) Interest Rate Reductions Total Modifications Principal Deferrals (a) Interest Rate Reductions Total Modifications Years Ended December 31 Business loans: Commercial $ 160 $ — $ 160 $ 22 $ — $ 22 Commercial mortgage: Commercial Real Estate business line (b) 8 — 8 — — — Other business lines (c) 6 — 6 6 — 6 Total commercial mortgage 14 — 14 6 — 6 International 2 — 2 — — — Total business loans 176 — 176 28 — 28 Retail loans: Residential mortgage — — — 1 (d) — 1 Consumer: Home equity 1 (d) 2 3 1 (d) 3 4 Other consumer — — — 1 (d) — 1 Total consumer 1 2 3 2 3 5 Total retail loans 1 2 3 3 3 6 Total loans $ 177 $ 2 $ 179 $ 31 $ 3 $ 34 (a) Primarily represents loan balances where terms were extended 90 days or more at or above contractual interest rates. (b) Primarily loans to real estate developers. (c) Primarily loans secured by owner-occupied real estate. (d) Includes bankruptcy loans for which the court has discharged the borrower's obligation and the borrower has not reaffirmed the debt.
Troubled Debt Restructuring Subsequent Default	The following table presents information regarding the recorded balance at December 31, 2015 and 2014 of loans modified by principal deferral during the years ended December 31, 2015 and 2014 , and those principal deferrals which experienced a subsequent default during the same periods. For principal deferrals, incremental deterioration in the credit quality of the loan, represented by a downgrade in the risk rating of the loan, for example, due to missed interest payments or a reduction of collateral value, is considered a subsequent default. 2015 2014 (in millions) Balance at December 31 Subsequent Default in the Year Ended December 31 Balance at December 31 Subsequent Default in the Year Ended December 31 Principal deferrals: Business loans: Commercial $ 160 $ 16 $ 22 $ 1 Commercial mortgage: Commercial Real Estate business line (a) 8 1 — — Other business lines (b) 6 1 6 2 Total commercial mortgage 14 2 6 2 International 2 — — — Total business loans 176 18 28 3 Retail loans: Residential mortgage — — 1 (c) — Consumer: Home equity 1 (c) — 1 (c) — Other consumer — — 1 (c) — Total consumer 1 — 2 — Total retail loans 1 — 3 — Total principal deferrals $ 177 $ 18 $ 31 $ 3 (a) Primarily loans to real estate developers. (b) Primarily loans secured by owner-occupied real estate. (c) Includes bankruptcy loans for which the court has discharged the borrower's obligation and the borrower has not reaffirmed the debt.

Significant Group Concentrati38

Significant Group Concentrations of Credit Risk Significant Group Concentrations of Credit Risk (Tables)	12 Months Ended
	Dec. 31, 2015
Significant Group Concentrations of Credit Risk [Abstract]
Schedule of Automotive Industry Outstanding Loans and Total Exposure	Outstanding loans, included in "commercial loans" on the consolidated balance sheets, and total exposure from loans, unused commitments and standby letters of credit to companies related to the automotive industry were as follows: (in millions) December 31 2015 2014 Automotive loans: Production $ 1,266 $ 1,236 Dealer 6,573 6,431 Total automotive loans $ 7,839 $ 7,667 Total automotive exposure: Production $ 2,452 $ 2,408 Dealer 8,209 7,763 Total automotive exposure $ 10,661 $ 10,171
Schedule of Commercial Real Estate Loans and Unused Commitments	Further, the Corporation’s portfolio of commercial real estate loans, which includes real estate construction and commercial mortgage loans, was as follows. (in millions) December 31 2015 2014 Real estate construction loans: Commercial Real Estate business line (a) $ 1,681 $ 1,606 Other business lines (b) 320 349 Total real estate construction loans 2,001 1,955 Commercial mortgage loans: Commercial Real Estate business line (a) 2,104 1,790 Other business lines (b) 6,873 6,814 Total commercial mortgage loans 8,977 8,604 Total commercial real estate loans $ 10,978 $ 10,559 Total unused commitments on commercial real estate loans $ 3,063 $ 2,335 (a) Primarily loans to real estate developers. (b) Primarily loans secured by owner-occupied real estate.

Premises and Equipment Premises

Premises and Equipment Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Summary of Premises and Equipment [Table Text Block]	A summary of premises and equipment by major category follows: (in millions) December 31 2015 2014 Land $ 87 $ 88 Buildings and improvements 862 808 Furniture and equipment 490 508 Total cost 1,439 1,404 Less: Accumulated depreciation and amortization (889 ) (872 ) Net book value $ 550 $ 532
Schedule of Future Minimum Lease Payments [Table Text Block]	As of December 31, 2015 , future minimum rental payments under operating leases were as follows: (in millions) Years Ending December 31 2016 $ 73 2017 70 2018 62 2019 53 2020 44 Thereafter 154 Total $ 456

Goodwill and Intangible Assets

Goodwill and Intangible Assets Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Changes in Carrying Value of Goodwill	The following table summarizes the carrying value of goodwill for the years ended December 31, 2015 , 2014 and 2013 . (in millions) December 31 2015 2014 2013 Business Bank $ 380 $ 380 $ 380 Retail Bank 194 194 194 Wealth Management 61 61 61 Total $ 635 $ 635 $ 635
Summary of Core Deposit Intangible Carrying Value and Amortization	A summary of core deposit intangible carrying value and related accumulated amortization follows: (in millions) December 31 2015 2014 Gross carrying amount $ 34 $ 34 Accumulated amortization (24 ) (21 ) Net carrying amount $ 10 $ 13
Schedule of Core Deposit Intangible Estimated Future Amortization Expense	At December 31, 2015 , estimated future amortization expense was as follows: (in millions) Years Ending December 31 2016 $ 2 2017 2 2018 2 2019 2 2020 1 Thereafter 1 Total $ 10

Derivative And Credit-Related41

Derivative And Credit-Related Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule Of Derivative Instruments	The following table presents the composition of the Corporation’s derivative instruments held or issued for risk management purposes or in connection with customer-initiated and other activities at December 31, 2015 and 2014 . The table excludes commitments and warrants accounted for as derivatives. December 31, 2015 December 31, 2014 Fair Value Fair Value (in millions) Notional/ Contract Amount (a) Gross Derivative Assets Gross Derivative Liabilities Notional/ Contract Amount (a) Gross Derivative Assets Gross Derivative Liabilities Risk management purposes Derivatives designated as hedging instruments Interest rate contracts: Swaps - fair value - receive fixed/pay floating $ 2,525 $ 147 $ — $ 1,800 $ 175 $ — Derivatives used as economic hedges Foreign exchange contracts: Spot, forwards and swaps 593 3 — 508 4 — Total risk management purposes 3,118 150 — 2,308 179 — Customer-initiated and other activities Interest rate contracts: Caps and floors written 253 — — 274 — — Caps and floors purchased 253 — — 274 — — Swaps 11,722 139 92 11,780 153 102 Total interest rate contracts 12,228 139 92 12,328 153 102 Energy contracts: Caps and floors written 536 — 85 1,218 — 173 Caps and floors purchased 536 85 — 1,218 173 — Swaps 2,055 390 387 2,496 354 352 Total energy contracts 3,127 475 472 4,932 527 525 Foreign exchange contracts: Spot, forwards, options and swaps 2,291 54 46 1,994 35 34 Total customer-initiated and other activities 17,646 668 610 19,254 715 661 Total gross derivatives $ 20,764 818 610 $ 21,562 894 661 Amounts offset in the consolidated balance sheets: Netting adjustment - Offsetting derivative assets/liabilities (127 ) (127 ) (133 ) (133 ) Netting adjustment - Cash collateral received/posted (291 ) (3 ) (262 ) — Net derivatives included in the consolidated balance sheets (b) 400 480 499 528 Amounts not offset in the consolidated balance sheets: Marketable securities received/pledged under bilateral collateral agreements (137 ) (3 ) (239 ) (2 ) Net derivatives after deducting amounts not offset in the consolidated balance sheets $ 263 $ 477 $ 260 $ 526 (a) Notional or contractual amounts, which represent the extent of involvement in the derivatives market, are used to determine the contractual cash flows required in accordance with the terms of the agreement. These amounts are typically not exchanged, significantly exceed amounts subject to credit or market risk and are not reflected in the consolidated balance sheets. (b) Net derivative assets are included in “accrued income and other assets” and net derivative liabilities are included in “accrued expenses and other liabilities” on the consolidated balance sheets. Included in the fair value of net derivative assets and net derivative liabilities are credit valuation adjustments reflecting counterparty credit risk and credit risk of the Corporation. The fair value of net derivative assets included credit valuation adjustments for counterparty credit risk of $5 million at December 31, 2015 and $2 million at December 31, 2014 .
Schedule Of Weighted Average Maturity And Interest Rates On Risk Management Interest Rate Swaps	The following table summarizes the expected weighted average remaining maturity of the notional amount of risk management interest rate swaps and the weighted average interest rates associated with amounts expected to be received or paid on interest rate swap agreements as of December 31, 2015 and 2014 . Weighted Average (dollar amounts in millions) Notional Amount Remaining Maturity (in years) Receive Rate Pay Rate (a) December 31, 2015 Swaps - fair value - receive fixed/pay floating rate Medium- and long-term debt designation $ 2,525 5.1 3.89 % 1.11 % December 31, 2014 Swaps - fair value - receive fixed/pay floating rate Medium- and long-term debt designation 1,800 4.6 4.54 0.49 (a) Variable rates paid on receive fixed swaps are based on six-month LIBOR rates in effect at December 31, 2015 and 2014 .
Schedule Of Net Gains Recognized In Income On Customer-Initiated Derivatives	The net gains recognized in income on customer-initiated derivative instruments, net of the impact of offsetting positions, were as follows. (in millions) Years Ended December 31 Location of Gain 2015 2014 Interest rate contracts Other noninterest income $ 16 $ 20 Energy contracts Other noninterest income 2 2 Foreign exchange contracts Foreign exchange income 37 38 Total $ 55 $ 60
Schedule Of Financial Instruments With Off-Balance Sheet Credit Risk	The Corporation’s credit risk associated with these instruments is represented by the contractual amounts indicated in the following table. (in millions) December 31 2015 2014 Unused commitments to extend credit: Commercial and other $ 26,115 $ 27,905 Bankcard, revolving check credit and home equity loan commitments 2,414 2,151 Total unused commitments to extend credit $ 28,529 $ 30,056 Standby letters of credit $ 3,985 $ 3,880 Commercial letters of credit 41 75
Summary Of Criticized Letters Of Credit	The following table presents a summary of criticized standby and commercial letters of credit at December 31, 2015 and December 31, 2014 . The Corporation's criticized list is consistent with the Special mention, Substandard and Doubtful categories defined by regulatory authorities. The Corporation manages credit risk through underwriting, periodically reviewing and approving its credit exposures using Board committee approved credit policies and guidelines. (dollar amounts in millions) December 31, 2015 December 31, 2014 Total criticized standby and commercial letters of credit $ 110 $ 79 As a percentage of total outstanding standby and commercial letters of credit 2.7 % 2.0 %

Deposits Deposits (Tables)

Deposits Deposits (Tables)	12 Months Ended
	Dec. 31, 2015
Deposits [Abstract]
Schedule Of Maturities Of Certificates of Deposit and Other Deposits with a Stated Maturity	At December 31, 2015 , the scheduled maturities of certificates of deposit and other deposits with a stated maturity were as follows: (in millions) Years Ending December 31 2016 $ 2,792 2017 503 2018 132 2019 83 2020 51 Thereafter 23 Total $ 3,584
Schedule Of Maturities Of Domestic Deposits Of $100,000 Or More	A maturity distribution of domestic certificates of deposit of $100,000 and over follows: (in millions) December 31 2015 2014 Three months or less $ 532 $ 822 Over three months to six months 385 456 Over six months to twelve months 659 733 Over twelve months 537 795 Total $ 2,113 $ 2,806

Net Income Per Common Share (Ta

Net Income Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Basic And Diluted Net Income Per Common Share	Basic and diluted net income per common share are presented in the following table. (in millions, except per share data) Years Ended December 31 2015 2014 2013 Basic and diluted Net income $ 521 $ 593 $ 541 Less income allocated to participating securities 6 7 8 Net income attributable to common shares $ 515 $ 586 $ 533 Basic average common shares 176 179 183 Basic net income per common share $ 2.93 $ 3.28 $ 2.92 Basic average common shares 176 179 183 Dilutive common stock equivalents: Net effect of the assumed exercise of stock options 2 2 1 Net effect of the assumed exercise of warrants 3 4 3 Diluted average common shares 181 185 187 Diluted net income per common share $ 2.84 $ 3.16 $ 2.85
Schedule of Average Shares Excluded From Diluted Net Income Per Common Share Computation	The following average shares related to outstanding options to purchase shares of common stock were not included in the computation of diluted net income per common share because the prices of the options and warrants were greater than the average market price of common shares for the period. (shares in millions) Years Ended December 31 2015 2014 2013 Average outstanding options 5.1 7.2 10.8 Range of exercise prices $46.68 - $60.82 $47.24 - $61.94 $34.78 - $61.94

Variable Interest Entities (V44

Variable Interest Entities (VIEs) (Tables)	12 Months Ended
	Dec. 31, 2015
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Impact of VIEs on the Consolidated Statements of Income	The following table summarizes the impact of these tax credit entities on line items on the Corporation’s consolidated statements of income. (in millions) Years Ended December 31 2015 2014 2013 Other noninterest income: Amortization of other tax credit investments $ 1 $ (5 ) $ (1 ) Provision for income taxes: Amortization of LIHTC Investments 62 60 56 Low income housing tax credits (61 ) (59 ) (56 ) Other tax benefits related to tax credit entities (22 ) (28 ) (21 ) Total provision for income taxes $ (21 ) $ (27 ) $ (21 )

Short-term Borrowings Short-ter

Short-term Borrowings Short-term Borrowings (Tables)	12 Months Ended
	Dec. 31, 2015
Short-term Debt [Abstract]
Summary of Short-term Borrowings	The following table provides a summary of short-term borrowings. (dollar amounts in millions) Federal Funds Purchased and Securities Sold Under Agreements to Repurchase December 31, 2015 Amount outstanding at year-end $ 23 Weighted average interest rate at year-end 0.38 % Maximum month-end balance during the year $ 109 Average balance outstanding during the year 93 Weighted average interest rate during the year 0.05 % December 31, 2014 Amount outstanding at year-end $ 116 Weighted average interest rate at year-end 0.04 % Maximum month-end balance during the year $ 238 Average balance outstanding during the year 200 Weighted average interest rate during the year 0.04 % December 31, 2013 Amount outstanding at year-end $ 253 Weighted average interest rate at year-end 0.05 % Maximum month-end balance during the year $ 277 Average balance outstanding during the year 211 Weighted average interest rate during the year 0.07 %

Medium- And Long-Term Debt (Tab

Medium- And Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Schedule Of Medium- And Long-Term Debt	Medium- and long-term debt is summarized as follows: (in millions) December 31 2015 2014 Parent company Subordinated notes: 4.80% subordinated notes due 2015 (a) $ — $ 304 3.80% subordinated notes due 2026 (a) 259 257 Medium-term notes: 3.00% notes due 2015 — 300 2.125% notes due 2019 (a) 349 347 Total parent company 608 1,208 Subsidiaries Subordinated notes: 5.75% subordinated notes due 2016 (a) (b) 659 670 5.20% subordinated notes due 2017 (a) 530 548 4.00% subordinated notes due 2025 (a) 351 — 7.875% subordinated notes due 2026 (a) 223 227 Total subordinated notes 1,763 1,445 Medium-term notes: 2.50% notes due 2020 (a) 671 — Other notes: 6.0% - 6.4% fixed-rate notes due 2015 to 2020 16 22 Total subsidiaries 2,450 1,467 Total medium- and long-term debt $ 3,058 $ 2,675 (a) The fixed interest rates on these notes have been swapped to a variable rate and designated in a hedging relationship. Accordingly, carrying value has been adjusted to reflect the change in the fair value of the debt as a result of changes in the benchmark rate. (b) The fixed interest rate on $250 million of $600 million total par value of these notes have been swapped to a variable rate.
Schedule of Maturities of Medium- and Long-term Debt	At December 31, 2015 , the principal maturities of medium- and long-term debt were as follows: (in millions) Years Ending December 31 2016 $ 650 2017 500 2018 2 2019 357 2020 682 Thereafter 750 Total $ 2,941

Accumulated Other Comprehensi47

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule Of Accumulated Other Comprehensive Income (Loss)	The following table presents a reconciliation of the changes in the components of accumulated other comprehensive loss and details the components of other comprehensive income (loss) for the years ended December 31, 2015 , 2014 and 2013 , including the amount of income tax expense (benefit) allocated to each component of other comprehensive income (loss). (in millions) Years Ended December 31 2015 2014 2013 Accumulated net unrealized gains (losses) on investment securities: Balance at beginning of period, net of tax $ 37 $ (68 ) $ 150 Net unrealized holding (losses) gains arising during the period (55 ) 166 (343 ) Less: (Benefit) provision for income taxes (21 ) 60 (126 ) Net unrealized holding (losses) gains arising during the period, net of tax (34 ) 106 (217 ) Less: Net realized (losses) gains included in net securities (losses) gains (2 ) 1 1 Less: Benefit for income taxes (1 ) — — Reclassification adjustment for net securities (losses) gains included in net income, net of tax (1 ) 1 1 Less: Net losses realized as a yield adjustment in interest on investment securities (8 ) — — Less: Benefit for income taxes (3 ) — — Reclassification adjustment for net losses realized as a yield adjustment included in net income, net of tax (5 ) — — Change in net unrealized (losses) gains on investment securities, net of tax (28 ) 105 (218 ) Balance at end of period, net of tax $ 9 $ 37 $ (68 ) Accumulated defined benefit pension and other postretirement plans adjustment: Balance at beginning of period, net of tax $ (449 ) $ (323 ) $ (563 ) Actuarial (loss) gain arising during the period (57 ) (240 ) 286 Prior service credit arising during the period 3 — — Net defined benefit pension and other postretirement adjustment arising during the period (54 ) (240 ) 286 Less: (Benefit) provision for income taxes (19 ) (87 ) 103 Net defined benefit pension and other postretirement adjustment arising during the period, net of tax (35 ) (153 ) 183 Amounts recognized in salaries and benefits expense: Amortization of actuarial net loss 70 39 89 Amortization of prior service cost 1 3 2 Total amounts recognized in salaries and benefits expense 71 42 91 Less: Benefit for income taxes 25 15 34 Adjustment for amounts recognized as components of net periodic benefit cost during the period, net of tax 46 27 57 Change in defined benefit pension and other postretirement plans adjustment, net of tax 11 (126 ) 240 Balance at end of period, net of tax $ (438 ) $ (449 ) $ (323 ) Total accumulated other comprehensive loss at end of period, net of tax $ (429 ) $ (412 ) $ (391 )

Share-Based Compensation Share-

Share-Based Compensation Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Share-based Compensation [Abstract]
Summary of Components of Share-Based Compensation Expense	The components of share-based compensation expense for all share-based compensation plans and related tax benefits are as follows. (in millions) Years Ended December 31 2015 2014 2013 Total share-based compensation expense $ 38 $ 38 $ 35 Related tax benefits recognized in net income $ 14 $ 14 $ 13
Schedule of Unrecognized Compensation Expense	The following table summarizes unrecognized compensation expense for all share-based plans: (dollar amounts in millions) December 31, 2015 Total unrecognized share-based compensation expense $ 49 Weighted-average expected recognition period (in years) 2.8
Estimated Weighted-Average Grant-Date Fair Value per Option and the Underlying Model Assumptions	The estimated weighted-average grant-date fair value per option and the underlying binomial option-pricing model assumptions are summarized in the following table: Years Ended December 31 2015 2014 2013 Weighted-average grant-date fair value per option $ 11.31 $ 13.21 $ 9.07 Weighted-average assumptions: Risk-free interest rates 1.83 % 2.95 % 1.94 % Expected dividend yield 3.00 3.00 3.00 Expected volatility factors of the market price of Comerica common stock 33 31 34 Expected option life (in years) 6.9 5.8 6.4
Summary of Stock Option Activity and Related Information	A summary of the Corporation’s stock option activity and related information for the year ended December 31, 2015 follows: Weighted-Average Number of Options (in thousands) Exercise Price per Share Remaining Contractual Term (in years) Aggregate Intrinsic Value (in millions) Outstanding-January 1, 2015 14,003 $ 44.28 Granted 1,035 42.32 Forfeited or expired (2,405 ) 53.88 Exercised (841 ) 33.46 Outstanding-December 31, 2015 11,792 42.92 4.1 $ 53 Outstanding, net of expected forfeitures-December 31, 2014 11,520 43.04 4.0 52 Exercisable-December 31, 2015 9,146 43.70 3.0 43
Summary of Restricted Stock Activity and Related Information	A summary of the Corporation’s restricted stock activity and related information for the year ended December 31, 2015 follows: Number of Shares (in thousands) Weighted-Average Grant-Date Fair Value per Share Outstanding-January 1, 2015 2,140 $ 35.38 Granted 413 42.45 Forfeited (106 ) 37.02 Vested (537 ) 33.29 Outstanding-December 31, 2015 1,910 $ 37.41
Summary of Restricted Stock Unit Activity and Related Information	A summary of the Corporation's restricted stock unit activity and related information for the year ended December 31, 2015 follows: Service-Based Units Performance-Based Units Number of Units (in thousands) Weighted-Average Grant-Date Fair Value per Share Number of Units (in thousands) Weighted-Average Grant-Date Fair Value per Share Outstanding-January 1, 2015 387 $ 34.58 319 $ 45.44 Granted 18 46.83 266 42.32 Converted 41 33.79 (41 ) 33.79 Forfeited (33 ) 37.78 (34 ) 43.27 Outstanding-December 31, 2015 413 34.77 510 44.89

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Schedule of Defined Benefit Plans Disclosures	The following table sets forth reconciliations of plan assets and the projected benefit obligation, the weighted-average assumptions used to determine year-end benefit obligations, and the amounts recognized in accumulated other comprehensive income (loss) for the Corporation’s defined benefit pension plans and postretirement benefit plan at December 31, 2015 and 2014 . The Corporation used a measurement date of December 31, 2015 for these plans. Defined Benefit Pension Plans Qualified Non-Qualified Postretirement Benefit Plan (dollar amounts in millions) 2015 2014 2015 2014 2015 2014 Change in fair value of plan assets: Fair value of plan assets at January 1 $ 2,541 $ 2,035 $ — $ — $ 67 $ 67 Actual return on plan assets (73 ) 278 — — — 3 Employer contributions — 350 — — — 2 Benefits paid (122 ) (a) (122 ) (a) — — (6 ) (5 ) Fair value of plan assets at December 31 $ 2,346 $ 2,541 $ — $ — $ 61 $ 67 Change in projected benefit obligation: Projected benefit obligation at January 1 $ 2,070 $ 1,731 $ 235 $ 195 $ 73 $ 69 Service cost 35 29 4 3 — — Interest cost 88 88 10 10 3 3 Actuarial (gain) loss (155 ) 344 (16 ) 37 (8 ) 6 Benefits paid (122 ) (a) (122 ) (a) (11 ) (10 ) (6 ) (5 ) Plan amendment — — — — (3 ) — Projected benefit obligation at December 31 $ 1,916 $ 2,070 $ 222 $ 235 $ 59 $ 73 Accumulated benefit obligation $ 1,756 $ 1,905 $ 191 $ 203 $ 59 $ 73 Funded status at December 31 (b) (c) $ 430 $ 471 $ (222 ) $ (235 ) $ 2 $ (6 ) Weighted-average assumptions used: Discount rate 4.82 % 4.28 % 4.82 % 4.28 % 4.53 % 3.99 % Rate of compensation increase 3.75 3.75 3.75 3.75 n/a n/a Healthcare cost trend rate: Cost trend rate assumed for next year n/a n/a n/a n/a 7.00 7.00 Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) n/a n/a n/a n/a 5.00 5.00 Year when rate reaches the ultimate trend rate n/a n/a n/a n/a 2027 2026 Amounts recognized in accumulated other comprehensive income (loss) before income taxes: Net actuarial loss $ (586 ) $ (568 ) $ (78 ) $ (104 ) $ (22 ) $ (27 ) Prior service (cost) credit (21 ) (25 ) 21 25 1 (3 ) Balance at December 31 $ (607 ) $ (593 ) $ (57 ) $ (79 ) $ (21 ) $ (30 ) (a) Included $56 million and $63 million in benefit payments made to certain terminated vested eligible participants who elected to receive lump-sum settlements in 2015 and 2014, respectively. (b) Based on projected benefit obligation for defined benefit pension plans and accumulated benefit obligation for postretirement benefit plan. (c) The Corporation recognizes the overfunded and underfunded status of the plans in “accrued income and other assets” and “accrued expenses and other liabilities,” respectively, on the consolidated balance sheets. n/a - not applicable
Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss)	The following table details the changes in plan assets and benefit obligations recognized in other comprehensive income (loss) for the year ended December 31, 2015 . Defined Benefit Pension Plans (in millions) Qualified Non-Qualified Postretirement Benefit Plan Total Actuarial (loss) gain arising during the period $ (77 ) $ 16 $ 4 $ (57 ) Prior service credit arising during the period — — 3 3 Amortization of net actuarial loss 59 10 1 70 Amortization of prior service cost (credit) 4 (4 ) 1 1 Total recognized in other comprehensive income (loss) $ (14 ) $ 22 $ 9 $ 17
Components of Net Periodic Defined Benefit Cost	Components of net periodic defined benefit cost and postretirement benefit cost, the actual return on plan assets and the weighted-average assumptions used were as follows. Defined Benefit Pension Plans (dollar amounts in millions) Qualified Non-Qualified Years Ended December 31 2015 2014 2013 2015 2014 2013 Service cost $ 35 $ 29 $ 37 $ 4 $ 3 $ 4 Interest cost 88 88 80 10 10 9 Expected return on plan assets (159 ) (131 ) (132 ) — — — Amortization of prior service cost (credit) 4 6 7 (4 ) (4 ) (6 ) Amortization of net loss 59 31 76 10 7 11 Net periodic defined benefit cost $ 27 $ 23 $ 68 $ 20 $ 16 $ 18 Actual return on plan assets $ (73 ) $ 278 $ 136 n/a n/a n/a Actual rate of return on plan assets (2.95 )% 13.88 % 7.05 % n/a n/a n/a Weighted-average assumptions used: Discount rate 4.28 % 5.17 % 4.20 % 4.28 % 5.17 % 4.20 % Expected long-term return on plan assets 6.75 6.75 7.25 n/a n/a n/a Rate of compensation increase 3.75 4.00 4.00 3.75 4.00 4.00 n/a - not applicable (dollar amounts in millions) Postretirement Benefit Plan Years Ended December 31 2015 2014 2013 Interest cost $ 3 $ 3 $ 3 Expected return on plan assets (4 ) (4 ) (4 ) Amortization of prior service cost 1 1 1 Amortization of net loss 1 1 2 Net periodic postretirement benefit cost $ 1 $ 1 $ 2 Actual return on plan assets $ — $ 3 $ (2 ) Actual rate of return on plan assets (0.53 )% 4.62 % (2.29 )% Weighted-average assumptions used: Discount rate 3.99 % 4.59 % 3.81 % Expected long-term return on plan assets 5.00 5.00 5.00 Healthcare cost trend rate: Cost trend rate assumed 7.00 7.50 8.00 Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 5.00 5.00 5.00 Year that the rate reaches the ultimate trend rate 2026 2033 2033
Balances Remaining in Accumulated Other Comprehensive Income (Loss) to be Recognized over Next Fiscal Year	The estimated portion of balances remaining in accumulated other comprehensive income (loss) that are expected to be recognized as a component of net periodic benefit cost in the year ended December 31, 2016 are as follows. Defined Benefit Pension Plans (in millions) Qualified Non-Qualified Postretirement Benefit Plan Total Net loss $ 30 $ 7 $ 1 $ 38 Prior service cost (credit) 4 (4 ) — —
Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates	Assumed healthcare cost trend rates have a significant effect on the amounts reported for the postretirement benefit plan. A one-percentage-point change in 2015 assumed healthcare and prescription drug cost trend rates would have the following effects. One-Percentage-Point (in millions) Increase Decrease Effect on postretirement benefit obligation $ 4 $ (3 ) Effect on total service and interest cost — —
Fair Value of Defined Benefit Plan Investments	The fair values of the Corporation’s qualified defined benefit pension plan investments measured at fair value on a recurring basis at December 31, 2015 and 2014 , by asset category and level within the fair value hierarchy, are detailed in the table below. (in millions) Total Level 1 Level 2 Level 3 December 31, 2015 Cash equivalent securities: Mutual funds $ 43 $ 43 $ — $ — Equity securities: Collective investment funds 527 — 527 — Mutual funds 69 69 — — Common stock 480 478 2 — Fixed income securities: U.S. Treasury and other U.S. government agency securities 356 356 — — Corporate and municipal bonds and notes 729 — 729 — Collateralized mortgage obligations 18 — 18 — U.S. government agency mortgage-backed securities 8 — 8 — Private placements 105 — — 105 Other assets: TBA mortgage-backed securities 12 — 12 — Total investments at fair value $ 2,347 $ 946 $ 1,296 $ 105 December 31, 2014 Cash equivalent securities: Mutual funds $ 390 $ 390 $ — $ — Equity securities: Collective investment funds 466 — 466 — Mutual funds 76 76 — — Common stock 499 499 — — Fixed income securities: U.S. Treasury and other U.S. government agency securities 359 359 — — Corporate and municipal bonds and notes 659 — 659 — Collateralized mortgage obligations 9 — 9 — Private placements 73 — 73 Total investments at fair value $ 2,531 $ 1,324 $ 1,134 $ 73
Changes in Level 3 Defined Benefit Plan Investments	The table below provides a summary of changes in the Corporation’s qualified defined benefit pension plan’s Level 3 investments measured at fair value on a recurring basis for the years ended December 31, 2015 and 2014 . Balance at Beginning of Period Balance at End of Period Net Gains (Losses) (in millions) Realized Unrealized Purchases Sales Year Ended December 31, 2015 Private placements $ 73 $ — $ (5 ) $ 108 $ (71 ) $ 105 Year Ended December 31, 2014 Private placements $ 36 $ 1 $ 4 $ 60 $ (28 ) $ 73
Estimated Future Benefit Payments	The Corporation currently expects to make no employer contributions to the qualified and non-qualified defined benefit pension plans and postretirement benefit plan for the year ended December 31, 2016 . Estimated Future Benefit Payments (in millions) Years Ended December 31 Qualified Defined Benefit Pension Plan Non-Qualified Defined Benefit Pension Plan Postretirement Benefit Plan (a) 2016 $ 72 $ 11 $ 6 2017 77 12 6 2018 83 12 6 2019 89 13 6 2020 94 13 6 2021 - 2025 550 70 24 (a) Estimated benefit payments in the postretirement benefit plan are net of estimated Medicare subsidies.

Income Taxes And Tax-Related 50

Income Taxes And Tax-Related Items Income Taxes And Tax-Related Items (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Current and Deferred Components of the Provision for Income Taxes	The current and deferred components of the provision for income taxes were as follows: (in millions) December 31 2015 2014 2013 Current: Federal $ 275 $ 127 $ 242 Foreign 5 6 6 State and local 20 14 17 Total current 300 147 265 Deferred: Federal (68 ) 123 (20 ) State and local (3 ) 7 — Total deferred (71 ) 130 (20 ) Total $ 229 $ 277 $ 245
Reconciliation of Expected Income Tax Expense at the Federal Statutory Rate to the Provision for Income Taxes	A reconciliation of expected income tax expense at the federal statutory rate to the Corporation’s provision for income taxes and effective tax rate follows: (dollar amounts in millions) 2015 2014 2013 Years Ended December 31 Amount Rate Amount Rate Amount Rate Tax based on federal statutory rate $ 262 35.0 % $ 305 35.0 % $ 275 35.0 % State income taxes 10 1.3 13 1.5 11 1.4 Affordable housing and historic credits (22 ) (2.9 ) (24 ) (2.8 ) (21 ) (2.6 ) Bank-owned life insurance (15 ) (2.0 ) (15 ) (1.7 ) (15 ) (1.9 ) Other changes in unrecognized tax benefits — — 2 0.2 (2 ) (0.2 ) Lease termination transactions (5 ) (0.7 ) — — — — Tax-related interest and penalties 1 0.1 (3 ) (0.3 ) (1 ) (0.1 ) Other (2 ) (0.3 ) (1 ) (0.1 ) (2 ) (0.4 ) Provision for income taxes $ 229 30.5 % $ 277 31.8 % $ 245 31.2 %
Reconciliation of Beginning and Ending Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of net unrecognized tax benefits follows: (in millions) 2015 2014 2013 Balance at January 1 $ 14 $ 11 $ 42 Increases as a result of tax positions taken during a prior period 8 3 — Decrease related to settlements with tax authorities — — (31 ) Balance at December 31 $ 22 $ 14 $ 11
Tax Years Remaining Open for Examination for Significant Tax Jurisdictions	The following tax years for significant jurisdictions remain subject to examination as of December 31, 2015 : Jurisdiction Tax Years Federal 2010-2014 California 2003-2014
Principal Components of Deferred Tax Assets and Liabilities	The principal components of deferred tax assets and liabilities were as follows: (in millions) December 31 2015 2014 Deferred tax assets: Allowance for loan losses $ 223 $ 208 Deferred compensation 113 123 Loan purchase accounting adjustments 2 5 Deferred loan origination fees and costs 24 28 Other temporary differences, net 67 44 Total deferred tax asset before valuation allowance 429 408 Valuation allowance (3 ) — Total deferred tax assets 426 408 Deferred tax liabilities: Lease financing transactions (183 ) (206 ) Defined benefit plans (32 ) (38 ) Net unrealized gains on investment securities available-for-sale (5 ) (21 ) Allowance for depreciation (7 ) (13 ) Total deferred tax liabilities (227 ) (278 ) Net deferred tax asset $ 199 $ 130

Regulatory Capital and Reserv51

Regulatory Capital and Reserve Requirements Regulatory Capital and Reserve Requirements (Tables)	12 Months Ended
	Dec. 31, 2015
Regulatory Capital Requirements [Abstract]
Summary of Capital Position	The following is a summary of the capital position of the Corporation and Comerica Bank, its principal banking subsidiary. (dollar amounts in millions) Comerica Incorporated (Consolidated) Comerica Bank December 31, 2015 CET1 capital (minimum $3.1 billion (Consolidated)) $ 7,350 $ 7,081 Tier 1 capital (minimum-$4.2 billion (Consolidated)) 7,350 7,081 Total capital (minimum-$5.6 billion (Consolidated)) 8,852 8,366 Risk-weighted assets 69,731 69,438 Average assets (fourth quarter) 71,943 71,629 CET1 capital to risk-weighted assets (minimum-4.5%) 10.54 % 10.20 % Tier 1 capital to risk-weighted assets (minimum-6.0%) 10.54 10.20 Total capital to risk-weighted assets (minimum-8.0%) 12.69 12.05 Tier 1 capital to average assets (minimum-4.0%) 10.22 9.89 December 31, 2014 Tier 1 capital (minimum-$2.7 billion (Consolidated)) $ 7,169 $ 7,051 Total capital (minimum-$5.5 billion (Consolidated)) 8,543 8,175 Risk-weighted assets 68,273 68,037 Average assets (fourth quarter) 69,284 69,092 Tier 1 capital to risk-weighted assets (minimum-4.0%) 10.50 % 10.36 % Total capital to risk-weighted assets (minimum-8.0%) 12.51 12.02 Tier 1 capital to average assets (minimum-3.0%) 10.35 10.20

Business Segment Information (T

Business Segment Information (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Business Segment Financial Results	Business segment financial results are as follows: (dollar amounts in millions) Business Bank Retail Bank Wealth Management Finance Other Total Year Ended December 31, 2015 Earnings summary: Net interest income (expense) (FTE) $ 1,511 $ 626 $ 179 $ (632 ) $ 9 $ 1,693 Provision for credit losses 158 8 (20 ) — 1 147 Noninterest income 574 185 235 57 (1 ) 1,050 Noninterest expenses 786 734 305 9 8 1,842 Provision (benefit) for income taxes (FTE) 376 22 44 (209 ) — 233 Net income (loss) $ 765 $ 47 $ 85 $ (375 ) $ (1 ) $ 521 Net loan charge-offs (recoveries) $ 89 $ 28 $ (17 ) $ — $ — $ 100 Selected average balances: Assets $ 38,942 $ 6,474 $ 5,153 $ 12,180 $ 7,498 $ 70,247 Loans 37,883 5,792 4,953 — — 48,628 Deposits 30,882 22,876 4,151 149 268 58,326 Statistical data: Return on average assets (a) 1.96 % 0.20 % 1.65 % N/M N/M 0.74 % Efficiency ratio (b) 37.71 90.37 73.23 N/M N/M 67.10 (dollar amounts in millions) Business Bank Retail Bank Wealth Management Finance Other Total Year Ended December 31, 2014 Earnings summary: Net interest income (expense) (FTE) $ 1,507 $ 606 $ 181 $ (662 ) $ 27 $ 1,659 Provision for credit losses 56 (7 ) (21 ) — (1 ) 27 Noninterest income 392 169 241 60 6 868 Noninterest expenses 589 715 310 (21 ) 33 1,626 Provision (benefit) for income taxes (FTE) 432 23 49 (224 ) 1 281 Net income (loss) $ 822 $ 44 $ 84 $ (357 ) $ — $ 593 Net loan charge-offs (recoveries) $ 16 $ 10 $ (1 ) $ — $ — $ 25 Selected average balances: Assets $ 37,178 $ 6,255 $ 4,988 $ 11,359 $ 6,556 $ 66,336 Loans 36,198 5,585 4,805 — — 46,588 Deposits 28,526 21,967 3,805 233 253 54,784 Statistical data: Return on average assets (a) 2.21 % 0.19 % 1.69 % N/M N/M 0.89 % Efficiency ratio (b) 30.97 92.10 73.67 N/M N/M 64.31 (Table continues on following page) (dollar amounts in millions) Business Bank Retail Bank Wealth Management Finance Other Total Year Ended December 31, 2013 Earnings summary: Net interest income (expense) (FTE) $ 1,495 $ 622 $ 180 $ (653 ) $ 31 $ 1,675 Provision for credit losses 42 24 (17 ) — (3 ) 46 Noninterest income 398 176 235 61 12 882 Noninterest expenses 642 719 309 10 42 1,722 Provision (benefit) for income taxes (FTE) 410 19 44 (226 ) 1 248 Net income (loss) $ 799 $ 36 $ 79 $ (376 ) $ 3 $ 541 Net loan charge-offs $ 32 $ 33 $ 8 $ — $ — $ 73 Selected average balances: Assets $ 35,326 $ 6,185 $ 4,799 $ 11,422 $ 6,201 $ 63,933 Loans 34,268 5,500 4,644 — — 44,412 Deposits 26,131 21,513 3,547 312 208 51,711 Statistical data: Return on average assets (a) 2.26 % 0.16 % 1.64 % N/M N/M 0.85 % Efficiency ratio (b) 33.89 89.77 74.86 N/M N/M 67.32 (a) Return on average assets is calculated based on the greater of average assets or average liabilities and attributed equity. (b) Noninterest expenses as a percentage of the sum of net interest income (FTE) and noninterest income excluding net securities gains. FTE – Fully Taxable Equivalent N/M – not meaningful
Market Segment Financial Results	Market segment financial results are as follows: (dollar amounts in millions) Michigan California Texas Other Markets Finance & Other Total Year Ended December 31, 2015 Earnings summary: Net interest income (expense) (FTE) $ 720 $ 736 $ 521 $ 339 $ (623 ) $ 1,693 Provision for credit losses (27 ) 17 131 25 1 147 Noninterest income 333 153 133 375 56 1,050 Noninterest expenses 598 408 389 430 17 1,842 Provision (benefit) for income taxes (FTE) 157 167 55 63 (209 ) 233 Net income (loss) $ 325 $ 297 $ 79 $ 196 $ (376 ) $ 521 Net loan charge-offs $ 8 $ 18 $ 45 $ 29 $ — $ 100 Selected average balances: Assets $ 13,761 $ 16,881 $ 11,778 $ 8,149 $ 19,678 $ 70,247 Loans 13,180 16,613 11,168 7,667 — 48,628 Deposits 21,872 17,763 10,882 7,392 417 58,326 Statistical data: Return on average assets (a) 1.42 % 1.57 % 0.63 % 2.41 % N/M 0.74 % Efficiency ratio (b) 56.72 45.96 59.52 59.97 N/M 67.10 (Table continues on following page) (dollar amounts in millions) Michigan California Texas Other Markets Finance & Other Total Year Ended December 31, 2014 Earnings summary: Net interest income (expense) (FTE) $ 718 $ 722 $ 542 $ 312 $ (635 ) $ 1,659 Provision for credit losses (32 ) 28 50 (18 ) (1 ) 27 Noninterest income 345 147 142 168 66 868 Noninterest expenses 643 398 370 203 12 1,626 Provision (benefit) for income taxes (FTE) 164 169 96 75 (223 ) 281 Net income (loss) $ 288 $ 274 $ 168 $ 220 $ (357 ) $ 593 Net loan charge-offs (recoveries) $ 8 $ 22 $ 9 $ (14 ) $ — $ 25 Selected average balances: Assets $ 13,749 $ 15,668 $ 11,645 $ 7,359 $ 17,915 $ 66,336 Loans 13,336 15,390 10,954 6,908 — 46,588 Deposits 21,023 16,142 10,764 6,369 486 54,784 Statistical data: Return on average assets (a) 1.31 % 1.59 % 1.39 % 3.00 % N/M 0.89 % Efficiency ratio (b) 60.48 45.79 54.00 42.30 N/M 64.31 (dollar amounts in millions) Michigan California Texas Other Markets Finance & Other Total Year Ended December 31, 2013 Earnings summary: Net interest income (expense) (FTE) $ 751 $ 692 $ 541 $ 313 $ (622 ) $ 1,675 Provision for credit losses (11 ) 17 35 8 (3 ) 46 Noninterest income 343 151 142 173 73 882 Noninterest expenses 713 396 364 197 52 1,722 Provision (benefit) for income taxes (FTE) 140 160 101 72 (225 ) 248 Net income (loss) $ 252 $ 270 $ 183 $ 209 $ (373 ) $ 541 Net loan charge-offs $ 6 $ 27 $ 20 $ 20 $ — $ 73 Selected average balances: Assets $ 13,879 $ 14,233 $ 10,694 $ 7,504 $ 17,623 $ 63,933 Loans 13,461 13,979 9,988 6,984 — 44,412 Deposits 20,346 14,705 10,247 5,893 520 51,711 Statistical data: Return on average assets (a) 1.18 % 1.72 % 1.59 % 2.79 % N/M 0.85 % Efficiency ratio (b) 65.09 47.00 53.22 40.52 N/M 67.32 (a) Return on average assets is calculated based on the greater of average assets or average liabilities and attributed equity. (b) Noninterest expenses as a percentage of the sum of net interest income (FTE) and noninterest income excluding net securities gains. FTE – Fully Taxable Equivalent N/M – not meaningful

Parent Company FInancial Stat53

Parent Company FInancial Statements Parent Company Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Balance Sheets - Comerica Incorporated	BALANCE SHEETS - COMERICA INCORPORATED (in millions, except share data) December 31 2015 2014 Assets Cash and due from subsidiary bank $ 4 $ — Short-term investments with subsidiary bank 569 1,133 Other short-term investments 89 94 Investment in subsidiaries, principally banks 7,523 7,411 Premises and equipment 3 2 Other assets 137 138 Total assets $ 8,325 $ 8,778 Liabilities and Shareholders’ Equity Medium- and long-term debt $ 608 $ 1,208 Other liabilities 157 168 Total liabilities 765 1,376 Common stock - $5 par value: Authorized - 325,000,000 shares Issued - 228,164,824 shares 1,141 1,141 Capital surplus 2,173 2,188 Accumulated other comprehensive loss (429 ) (412 ) Retained earnings 7,084 6,744 Less cost of common stock in treasury - 52,457,113 shares at 12/31/15 and 49,146,225 shares at 12/31/14 (2,409 ) (2,259 ) Total shareholders’ equity 7,560 7,402 Total liabilities and shareholders’ equity $ 8,325 $ 8,778
Statements of Income - Comerica Incorporated	STATEMENTS OF INCOME - COMERICA INCORPORATED (in millions) Years Ended December 31 2015 2014 2013 Income Income from subsidiaries: Dividends from subsidiaries $ 441 $ 384 $ 490 Other interest income 1 1 1 Intercompany management fees 123 118 110 Other noninterest income 1 7 14 Total income 566 510 615 Expenses Interest on medium- and long-term debt 14 14 11 Salaries and benefits expense 112 114 118 Net occupancy expense 5 5 4 Equipment expense 1 1 1 Other noninterest expenses 70 70 78 Total expenses 202 204 212 Income before benefit for income taxes and equity in undistributed earnings of subsidiaries 364 306 403 Benefit for income taxes (27 ) (27 ) (30 ) Income before equity in undistributed earnings of subsidiaries 391 333 433 Equity in undistributed earnings of subsidiaries, principally banks 130 260 108 Net income 521 593 541 Less income allocated to participating securities 6 7 8 Net income attributable to common shares $ 515 $ 586 $ 533
Statements of Cash Flows - Comerica Incorporated	STATEMENTS OF CASH FLOWS - COMERICA INCORPORATED (in millions) Years Ended December 31 2015 2014 2013 Operating Activities Net income $ 521 $ 593 $ 541 Adjustments to reconcile net income to net cash provided by operating activities: Undistributed earnings of subsidiaries, principally banks (130 ) (260 ) (108 ) Depreciation and amortization 1 1 1 Net periodic defined benefit cost 5 4 8 Share-based compensation expense 14 16 14 Provision for deferred income taxes — — 3 Excess tax benefits from share-based compensation arrangements (3 ) (7 ) (3 ) Other, net 5 16 2 Net cash provided by operating activities 413 363 458 Investing Activities Net change in premises and equipment (1 ) 2 — Net cash (used in) provided by investing activities (1 ) 2 — Financing Activities Medium- and long-term debt: Maturities and redemptions (600 ) — — Issuances — 596 — Common Stock: Repurchases (240 ) (260 ) (291 ) Cash dividends paid (147 ) (137 ) (123 ) Issuances of common stock under employee stock plans 22 49 33 Purchase and retirement of warrants (10 ) — — Excess tax benefits from share-based compensation arrangements 3 7 3 Net cash (used in) provided by financing activities (972 ) 255 (378 ) Net (decrease) increase in cash and cash equivalents (560 ) 620 80 Cash and cash equivalents at beginning of period 1,133 513 433 Cash and cash equivalents at end of period $ 573 $ 1,133 $ 513 Interest paid $ 16 $ 12 $ 11 Income taxes recovered $ (62 ) $ (33 ) $ (27 )

Summary of Quarterly Financia54

Summary of Quarterly Financial Statements (Unaudited) Summary of Quarterly Financial Statements (Unaudited ) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Statements	The following quarterly information is unaudited. However, in the opinion of management, the information reflects all adjustments, which are necessary for the fair presentation of the results of operations, for the periods presented. 2015 (in millions, except per share data) Fourth Quarter Third Quarter Second Quarter First Quarter Interest income $ 457 $ 448 $ 444 $ 435 Interest expense 24 26 23 22 Net interest income 433 422 421 413 Provision for credit losses 60 26 47 14 Net securities losses — — — (2 ) Noninterest income excluding net securities losses 270 264 261 257 Noninterest expenses 486 461 436 459 Provision for income taxes 41 63 64 61 Net income 116 136 135 134 Less income allocated to participating securities 1 2 1 2 Net income attributable to common shares $ 115 $ 134 $ 134 $ 132 Earnings per common share: Basic $ 0.65 $ 0.76 $ 0.76 $ 0.75 Diluted 0.64 0.74 0.73 0.73 Comprehensive income 31 187 109 176 2014 (in millions, except per share data) Fourth Quarter Third Quarter Second Quarter First Quarter Interest income $ 438 $ 436 $ 441 $ 435 Interest expense 23 22 25 25 Net interest income 415 414 416 410 Provision for credit losses 2 5 11 9 Net securities (losses) gains — (1 ) — 1 Noninterest income excluding net securities (losses) gains 225 216 220 207 Noninterest expenses 419 397 404 406 Provision for income taxes 70 73 70 64 Net income 149 154 151 139 Less income allocated to participating securities 1 2 2 2 Net income attributable to common shares $ 148 $ 152 $ 149 $ 137 Earnings per common share: Basic $ 0.83 $ 0.85 $ 0.83 $ 0.76 Diluted 0.80 0.82 0.80 0.73 Comprehensive income 54 141 172 205

Basis of Presentation and Acc55

Basis of Presentation and Accounting Policies Basis of Presentation and Accounting Policies (Narrative) (Details) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2013USD ($)	Dec. 31, 2015USD ($)markets	Dec. 31, 2014USD ($)
Number of Primary Geographic Markets | markets			3
Minimum Ownership Percentage to Qualify for Equity Method			20.00%
Derivative assets			$ 818	$ 894
Commitments to fund additional investments in nonmarketable equity securities			$ 4
Estimated liquidation period of assets underlying indirect private equity and venture capital funds			12 years
Federal Home Loan Bank Stock			$ 7	7
Federal Reserve Bank Stock			85	85
Net Deferred Income on Originated Loans			226	267
Allowance for Credit Losses, Threshold for Individual Evaluation, Nonaccrual Loans			$ 2
Increase in Allowance due to Enhancements to Methodology		$ 40
Delinquency Status, Period of Unpaid Scheduled Monthly Payment			30 days
Number of Reporting Units			3
Notional Amount	[1]		$ 20,764	21,562
Defined Benefit Plan Market-related Value Plan Assets, Amortization Period			5 years
Defined Benefit Plan Investment Gain Loss Amortization Adjustment, Allowable Percentage			10.00%
Defined Benefit Plan Actuarial Gain Loss Amortization Adjustment, Allowable Percentage			10.00%
Premises the Corporation owns | Minimum
Premises and Equipment, Useful Life			3 years
Premises the Corporation owns | Maximum
Premises and Equipment, Useful Life			33 years
Furniture and equipment | Minimum
Premises and Equipment, Useful Life			3 years
Furniture and equipment | Maximum
Premises and Equipment, Useful Life			8 years
Leasehold improvements | Maximum
Premises and Equipment, Useful Life			10 years
Software
Premises and Equipment, Useful Life			5 years
Recurring
Derivative assets			$ 820	898
Carrying Amount
Nonmarketable equity securities			10	11	[2]
Warrants | Recurring
Derivative assets			$ 2	$ 4
Retail loans | Real estate
Past Due Period Residential Mortgage And Home Equity Loans Placed On Nonaccrual Status			90 days
Past Due Threshold For Charge-Off			180 days
Short-Cut Method | Designated as Hedging Instrument | Interest Rate Swaps | Fair Value Hedging
Notional Amount			$ 400
Commercial borrower | Business loans
Past Due Period Business Loans Placed On Nonaccrual Status			90 days
Consumer borrower | Retail loans | Home equity
Maximum Past Due Status Junior Lien Home Equity Placed On Nonaccrual Status			90 days
Consumer borrower | Retail loans | Other consumer
Past Due Threshold For Charge-Off			120 days
Threshold, Days Past Due, Other Consumer Placed On Nonaccrual Status			90 days
[1]	Notional or contractual amounts, which represent the extent of involvement in the derivatives market, are used to determine the contractual cash flows required in accordance with the terms of the agreement. These amounts are typically not exchanged, significantly exceed amounts subject to credit or market risk and are not reflected in the consolidated balance sheets.
[2]	Included $1 million and $2 million of nonmarketable equity securities recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014, respectively.

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Recurring
Transfers into or out of Level 1 or Level 2 or Level 3	$ 0	$ 0
Total liabilities at fair value	699	755
Nonrecurring
Total liabilities at fair value	$ 0	$ 0

Fair Value Measurements (Assets

Fair Value Measurements (Assets And Liabilities Recorded At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions		Dec. 31, 2015		Dec. 31, 2014
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale	[1]	$ 10,519		$ 8,116
Derivative assets		818		894
Derivative liabilities	[2]	480		528
Equity and other non-debt securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		201		242
U.S. Treasury and other U.S. government agency securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		2,763		526
Residential mortgage-backed securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale	[3]	7,545		7,274
State and municipal securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		9		23
Corporate debt securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		1		51
Recurring
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		92
Investment securities available-for-sale		10,519		8,116
Derivative assets		820		898
Total assets at fair value		11,431		9,108
Derivative liabilities		610		661
Deferred compensation plan liabilities		89		94
Total liabilities at fair value		699		755
Recurring | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		92
Investment securities available-for-sale		2,897		656
Derivative assets		0		0
Total assets at fair value		2,989		750
Derivative liabilities		0		0
Deferred compensation plan liabilities		89		94
Total liabilities at fair value		89		94
Recurring | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		0
Investment securities available-for-sale		7,545		7,324
Derivative assets		809		894
Total assets at fair value		8,354		8,218
Derivative liabilities		610		661
Deferred compensation plan liabilities		0		0
Total liabilities at fair value		610		661
Recurring | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		0
Investment securities available-for-sale		77		136
Derivative assets		11		4
Total assets at fair value		88		140
Derivative liabilities		0		0
Deferred compensation plan liabilities		0		0
Total liabilities at fair value		0		0
Recurring | Interest rate contracts
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		286		328
Derivative liabilities		92		102
Recurring | Interest rate contracts | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		0		0
Derivative liabilities		0		0
Recurring | Interest rate contracts | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		277		328
Derivative liabilities		92		102
Recurring | Interest rate contracts | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		9		0
Derivative liabilities		0		0
Recurring | Energy derivative contracts
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		475		527
Derivative liabilities		472		525
Recurring | Energy derivative contracts | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		0		0
Derivative liabilities		0		0
Recurring | Energy derivative contracts | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		475		527
Derivative liabilities		472		525
Recurring | Energy derivative contracts | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		0		0
Derivative liabilities		0		0
Recurring | Foreign exchange contracts
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		57		39
Derivative liabilities		46		34
Recurring | Foreign exchange contracts | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		0		0
Derivative liabilities		0		0
Recurring | Foreign exchange contracts | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		57		39
Derivative liabilities		46		34
Recurring | Foreign exchange contracts | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		0		0
Derivative liabilities		0		0
Recurring | Warrants
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		2		4
Recurring | Warrants | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		0		0
Recurring | Warrants | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		0		0
Recurring | Warrants | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		2		4
Recurring | Deferred compensation plan assets
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		89		94
Recurring | Deferred compensation plan assets | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		89		94
Recurring | Deferred compensation plan assets | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		0		0
Recurring | Deferred compensation plan assets | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		0		0
Recurring | Equity and other non-debt securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		3
Investment securities available-for-sale		201		242
Recurring | Equity and other non-debt securities | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		3
Investment securities available-for-sale		134		130
Recurring | Equity and other non-debt securities | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		0
Investment securities available-for-sale		0		0
Recurring | Equity and other non-debt securities | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		0
Investment securities available-for-sale		67	[4]	112	[5]
Recurring | U.S. Treasury and other U.S. government agency securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		2,763		526
Recurring | U.S. Treasury and other U.S. government agency securities | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		2,763		526
Recurring | U.S. Treasury and other U.S. government agency securities | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		0		0
Recurring | U.S. Treasury and other U.S. government agency securities | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		0		0
Recurring | Residential mortgage-backed securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		7,545	[6]	7,274	[7]
Recurring | Residential mortgage-backed securities | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		0	[6]	0	[7]
Recurring | Residential mortgage-backed securities | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		7,545	[6]	7,274	[7]
Recurring | Residential mortgage-backed securities | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		0	[6]	0	[7]
Recurring | State and municipal securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		9		23
Recurring | State and municipal securities | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		0		0
Recurring | State and municipal securities | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		0		0
Recurring | State and municipal securities | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		9	[4]	23	[5]
Recurring | Corporate debt securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		1		51
Recurring | Corporate debt securities | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		0		0
Recurring | Corporate debt securities | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		0		50
Recurring | Corporate debt securities | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		$ 1	[4]	$ 1	[5]
[1]	Included auction-rate securities at amortized cost and fair value of $76 million and $77 million, respectively, as of December 31, 2015 and $137 million and $136 million, respectively, as of December 31, 2014.
[2]	Net derivative assets are included in “accrued income and other assets” and net derivative liabilities are included in “accrued expenses and other liabilities” on the consolidated balance sheets. Included in the fair value of net derivative assets and net derivative liabilities are credit valuation adjustments reflecting counterparty credit risk and credit risk of the Corporation. The fair value of net derivative assets included credit valuation adjustments for counterparty credit risk of $5 million at December 31, 2015 and $2 million at December 31, 2014.
[3]	Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.
[4]	Auction-rate securities.
[5]	Auction-rate securities.
[6]	Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.
[7]	Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.

Fair Value Measurements (Change

Fair Value Measurements (Changes In Level 3 Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Interest rate contracts
Balance at beginning of period		$ 0
Realized gains (losses) recorded in earnings		0
Unrealized gains (losses) recorded in earnings	[1]	9
Gains (losses) recorded in other comprehensive income (loss)		0
Sales		0
Balance at end of period		9	$ 0
Warrants
Balance at beginning of period		4	3
Realized gains (losses) recorded in earnings	[1]	6	7
Unrealized gains (losses) recorded in earnings	[1]	(1)	1
Gains (losses) recorded in other comprehensive income (loss)		0	0
Sales		(7)	(7)
Balance at end of period		2	4
Investment securities available-for-sale
Balance at beginning of period		136	159
Realized gains (losses) recorded in earnings	[2]	(2)	2
Unrealized gains (losses) recorded in earnings		0	0
Gains (losses) recorded in other comprehensive income (loss)	[3]	1	8
Sales		(58)	(33)
Balance at end of period		77	136
State and municipal securities | Investment securities available-for-sale
Balance at beginning of period	[4]	23	22
Realized gains (losses) recorded in earnings	[4]	0	0
Unrealized gains (losses) recorded in earnings	[4]	0	0
Gains (losses) recorded in other comprehensive income (loss)	[4]	0	1	[3]
Sales	[4]	(14)	0
Balance at end of period	[4]	9	23
Corporate debt securities | Investment securities available-for-sale
Balance at beginning of period	[4]	1	1
Realized gains (losses) recorded in earnings	[4]	0	0
Unrealized gains (losses) recorded in earnings	[4]	0	0
Gains (losses) recorded in other comprehensive income (loss)	[4]	0	0
Sales	[4]	0	0
Balance at end of period	[4]	1	1
Equity and other non-debt securities | Investment securities available-for-sale
Balance at beginning of period	[4]	112	136
Realized gains (losses) recorded in earnings	[2],[4]	(2)	2
Unrealized gains (losses) recorded in earnings	[4]	0	0
Gains (losses) recorded in other comprehensive income (loss)	[3],[4]	1	7
Sales	[4]	(44)	(33)
Balance at end of period	[4]	$ 67	$ 112
[1]	Realized and unrealized gains and losses due to changes in fair value recorded in "other noninterest income" on the consolidated statements of income.
[2]	Realized and unrealized gains and losses due to changes in fair value recorded in "net securities losses" on the consolidated statements of income.
[3]	Recorded in "net unrealized (losses) gains on investment securities available-for-sale" in other comprehensive income.
[4]	Auction-rate securities.

Fair Value Measurements (Asse59

Fair Value Measurements (Assets And Liabilities Recorded At Fair Value On A Nonrecurring Basis) (Details) - Nonrecurring - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans	$ 153	$ 64
Nonmarketable equity securities	1	2
Other real estate	2	2
Total assets at fair value	164	68
Level 2
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans	0	0
Nonmarketable equity securities	0	0
Other real estate	0	0
Total assets at fair value	8	0
Level 3
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans	153	64
Nonmarketable equity securities	1	2
Other real estate	2	2
Total assets at fair value	156	68
Commercial borrower | Domestic loans
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans held-for-sale	8
Loans	134	38
Commercial borrower | Domestic loans | Level 2
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans held-for-sale	8
Loans	0	0
Commercial borrower | Domestic loans | Level 3
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans held-for-sale	0
Loans	134	38
Commercial borrower | International loans
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans	8
Commercial borrower | International loans | Level 2
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans	0
Commercial borrower | International loans | Level 3
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans	8
Commercial borrower | Commercial mortgage loans | Domestic loans
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans	11	26
Commercial borrower | Commercial mortgage loans | Domestic loans | Level 2
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans	0	0
Commercial borrower | Commercial mortgage loans | Domestic loans | Level 3
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Line Items]
Loans	$ 11	$ 26

Fair Value Measurements (Quanti

Fair Value Measurements (Quantitative Information About Level 3 Measurements) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investment securities available-for-sale	[1]	$ 10,519	$ 8,116
Recurring
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investment securities available-for-sale		10,519	8,116
Recurring | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investment securities available-for-sale		77	136
Recurring | State and municipal securities | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investment securities available-for-sale	[2]	$ 9	$ 23
Recurring | State and municipal securities | Minimum | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Unobservable Input, Discount rate	[2]	3.00%	3.00%
Unobservable Input, Workout period	[2]	1 year	1 year
Recurring | State and municipal securities | Maximum | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Unobservable Input, Discount rate	[2]	8.00%	9.00%
Unobservable Input, Workout period	[2]	2 years	3 years
Recurring | Equity and other non-debt securities | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investment securities available-for-sale	[2]	$ 67	$ 112
Recurring | Equity and other non-debt securities | Minimum | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Unobservable Input, Discount rate	[2]	4.00%	4.00%
Unobservable Input, Workout period	[2]	1 year	1 year
Recurring | Equity and other non-debt securities | Maximum | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Unobservable Input, Discount rate	[2]	9.00%	8.00%
Unobservable Input, Workout period	[2]	1 year	2 years
[1]	Included auction-rate securities at amortized cost and fair value of $76 million and $77 million, respectively, as of December 31, 2015 and $137 million and $136 million, respectively, as of December 31, 2014.
[2]	Auction-rate securities.

Fair Value Measurements (Estima

Fair Value Measurements (Estimated Fair Values Of Financial Instruments Not Recorded At Fair Value In Their Entirety On A Recurring Basis) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Cash and due from banks		$ 1,157	$ 1,026
Interest-bearing deposits with banks		4,990	5,045
Investment securities held-to-maturity		1,981	1,935
Total loans, net of allowance for loan losses		48,450	47,999
Demand deposits (noninterest-bearing)		30,839	27,224
Customer certificates of deposit		3,552	4,421
Total deposits		59,853	57,486
Short-term borrowings		23	116
Medium- and long-term debt		3,058	2,675
Carrying Amount
Cash and due from banks		1,157	1,026
Interest-bearing deposits with banks		4,990	5,045
Investment securities held-to-maturity		1,981	1,935
Loans held-for-sale	[1]	21	5
Total loans, net of allowance for loan losses	[2]	48,450	47,999
Customers' liability on acceptances outstanding		5	10
Nonmarketable equity securities		10	11	[3]
Restricted equity investments		92	92
Demand deposits (noninterest-bearing)		30,839	27,224
Interest-bearing deposits		25,462	25,841
Customer certificates of deposit		3,552	4,421
Total deposits		59,853	57,486
Short-term borrowings		23	116
Acceptances outstanding		5	10
Medium- and long-term debt		3,058	2,675
Credit-related financial instruments		(83)	(85)
Estimated Fair Value
Cash and due from banks		1,157	1,026
Interest-bearing deposits with banks		4,990	5,045
Investment securities held-to-maturity		1,973	1,933
Loans held-for-sale	[1]	21	5
Total loans, net of allowance for loan losses	[2]	48,269	47,932
Customers' liability on acceptances outstanding		5	10
Nonmarketable equity securities	[3]	18	18
Restricted equity investments		92	92
Demand deposits (noninterest-bearing)		30,839	27,224
Interest-bearing deposits		25,462	25,841
Customer certificates of deposit		3,536	4,411
Total deposits		59,837	57,476
Short-term borrowings		23	116
Acceptances outstanding		5	10
Medium- and long-term debt		3,032	2,681
Credit-related financial instruments		(83)	(85)
Level 1 | Estimated Fair Value
Cash and due from banks		1,157	1,026
Interest-bearing deposits with banks		4,990	5,045
Investment securities held-to-maturity		0	0
Loans held-for-sale	[1]	0	0
Total loans, net of allowance for loan losses	[2]	0	0
Customers' liability on acceptances outstanding		5	10
Nonmarketable equity securities	[3]	0	0
Restricted equity investments		92	92
Demand deposits (noninterest-bearing)		0	0
Interest-bearing deposits		0	0
Customer certificates of deposit		0	0
Total deposits		0	0
Short-term borrowings		23	116
Acceptances outstanding		5	10
Medium- and long-term debt		0	0
Credit-related financial instruments		0	0
Level 2 | Estimated Fair Value
Cash and due from banks		0	0
Interest-bearing deposits with banks		0	0
Investment securities held-to-maturity		1,973	1,933
Loans held-for-sale	[1]	21	5
Total loans, net of allowance for loan losses	[2]	0	0
Customers' liability on acceptances outstanding		0	0
Nonmarketable equity securities	[3]	0	0
Restricted equity investments		0	0
Demand deposits (noninterest-bearing)		30,839	27,224
Interest-bearing deposits		25,462	25,841
Customer certificates of deposit		3,536	4,411
Total deposits		59,837	57,476
Short-term borrowings		0	0
Acceptances outstanding		0	0
Medium- and long-term debt		3,032	2,681
Credit-related financial instruments		0	0
Level 3 | Estimated Fair Value
Cash and due from banks		0	0
Interest-bearing deposits with banks		0	0
Investment securities held-to-maturity		0	0
Loans held-for-sale	[1]	0	0
Total loans, net of allowance for loan losses	[2]	48,269	47,932
Customers' liability on acceptances outstanding		0	0
Nonmarketable equity securities	[3]	18	18
Restricted equity investments		0	0
Demand deposits (noninterest-bearing)		0	0
Interest-bearing deposits		0	0
Customer certificates of deposit		0	0
Total deposits		0	0
Short-term borrowings		0	0
Acceptances outstanding		0	0
Medium- and long-term debt		0	0
Credit-related financial instruments		(83)	(85)
Nonrecurring
Loans held-for-sale		8	0
Nonmarketable equity securities		1	2
Loans		153	64
Nonrecurring | Level 2
Nonmarketable equity securities		0	0
Loans		0	0
Nonrecurring | Level 3
Nonmarketable equity securities		1	2
Loans		$ 153	$ 64
[1]	Included $8 million and no impaired loans held-for-sale recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014, respectively.
[2]	Included $153 million and $64 million of impaired loans recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014, respectively.
[3]	Included $1 million and $2 million of nonmarketable equity securities recorded at fair value on a nonrecurring basis at December 31, 2015 and 2014, respectively.

Investment Securities (Narrativ

Investment Securities (Narrative) (Details) $ in Millions		12 Months Ended
		Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Available-for-sale Securities, Amortized Cost	[1]	$ 10,491	$ 8,035
Unrealized losses on available-for-sale securities transferred to held-to-maturity		$ 15	23
Securities with no credit impairment in unrealized loss position		179
ARS portfolio redeemed or sold since acquisition		94.00%
ARS portfolio redeemed or sold since acquisition at or above cost		91.00%
Investment securities available-for-sale, Amortized Cost		$ 10,292
Investment securities available-for-sale, Fair Value	[1]	10,519	8,116
Held-to-maturity securities, Amortized Cost		1,981	1,935
Held-to-maturity securities, Fair Value		1,973
Carrying value of securities pledged		2,400
Liabilities secured by pledged collateral		$ 1,200
Residential mortgage-backed securities
Available-for-sale Securities, Amortized Cost	[2]		7,192
Available-for-sale securities transferred to held-to-maturity			2,000
Securities with no credit impairment in unrealized loss position		124
Investment securities available-for-sale, Fair Value	[2]	$ 7,545	7,274
Held-to-maturity securities, Amortized Cost	[2],[3]		1,935
Held-to-maturity securities, Fair Value	[2],[3]	$ 1,973	1,933
Auction-rate preferred securities
Securities with no credit impairment in unrealized loss position		12
Auction-rate state and municipal securities
Securities with no credit impairment in unrealized loss position		16
Auction-rate corporate debt securities
Securities with no credit impairment in unrealized loss position		1
U.S. Treasury and other U.S. government agency securities
Available-for-sale Securities, Amortized Cost		$ 2,769	526
Securities with no credit impairment in unrealized loss position		26
Investment securities available-for-sale, Fair Value		$ 2,763	$ 526
Prepayment options | Residential mortgage-backed securities
Investment securities available-for-sale, Amortized Cost		7,500
Investment securities available-for-sale, Fair Value		7,500
Held-to-maturity securities, Amortized Cost	[2],[3]	1,981
Held-to-maturity securities, Fair Value		$ 2,000
[1]	Included auction-rate securities at amortized cost and fair value of $76 million and $77 million, respectively, as of December 31, 2015 and $137 million and $136 million, respectively, as of December 31, 2014.
[2]	Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.
[3]	The amortized cost of investment securities held-to-maturity included net unrealized losses of $15 million at December 31, 2015 and $23 million at December 31, 2014 related to securities transferred from available-for-sale, which are included in accumulated other comprehensive loss.

Investment Securities (Summary

Investment Securities (Summary Of Investment Securities Available-For-Sale) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Available-for-sale Securities, Amortized Cost	[1]	$ 10,491	$ 8,035
Available-for-sale securities, Gross Unrealized Gains	[1]	79	123
Available-for-sale Securities, Gross Unrealized Losses	[1]	51	42
Investment securities available-for-sale, Fair Value	[1]	10,519	8,116
Available-for-sale Debt Securities, Amortized Cost Basis		10,292
Held-to-maturity securities, Amortized Cost		1,981	1,935
Held-to-maturity securities, Fair Value		1,973
Unrealized losses on available-for-sale securities transferred to held-to-maturity		15	23
U.S. Treasury and other U.S. government agency securities
Available-for-sale Securities, Amortized Cost		2,769	526
Available-for-sale securities, Gross Unrealized Gains		1	0
Available-for-sale Securities, Gross Unrealized Losses		7	0
Investment securities available-for-sale, Fair Value		2,763	526
Residential mortgage-backed securities
Available-for-sale Securities, Amortized Cost	[2]		7,192
Available-for-sale securities, Gross Unrealized Gains	[2]	76	122
Available-for-sale Securities, Gross Unrealized Losses	[2]	44	40
Investment securities available-for-sale, Fair Value	[2]	7,545	7,274
Held-to-maturity securities, Amortized Cost	[2],[3]		1,935
Held-to-maturity securities, Gross Unrealized Gains	[2],[3]	2	0
Held-to-maturity securities, Gross Unrealized Losses	[2],[3]	10	2
Held-to-maturity securities, Fair Value	[2],[3]	1,973	1,933
State and municipal securities
Available-for-sale Securities, Amortized Cost		9	24
Available-for-sale securities, Gross Unrealized Gains		0	0
Available-for-sale Securities, Gross Unrealized Losses		0	1
Investment securities available-for-sale, Fair Value		9	23
Corporate debt securities
Available-for-sale Securities, Amortized Cost		1	51
Available-for-sale securities, Gross Unrealized Gains		0	0
Available-for-sale Securities, Gross Unrealized Losses		0	0
Investment securities available-for-sale, Fair Value		1	51
Equity and other non-debt securities
Available-for-sale Securities, Amortized Cost		199	242
Available-for-sale securities, Gross Unrealized Gains		2	1
Available-for-sale Securities, Gross Unrealized Losses		0	1
Investment securities available-for-sale, Fair Value		201	242
Held-to-maturity securities, Amortized Cost		0
Held-to-maturity securities, Fair Value		0
Auction-rate securities
Available-for-sale Securities, Amortized Cost		76	137
Investment securities available-for-sale, Fair Value		$ 77	$ 136
[1]	Included auction-rate securities at amortized cost and fair value of $76 million and $77 million, respectively, as of December 31, 2015 and $137 million and $136 million, respectively, as of December 31, 2014.
[2]	Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.
[3]	The amortized cost of investment securities held-to-maturity included net unrealized losses of $15 million at December 31, 2015 and $23 million at December 31, 2014 related to securities transferred from available-for-sale, which are included in accumulated other comprehensive loss.

Investment Securities (Summar64

Investment Securities (Summary Of Investment Securities Available-For-Sale In Unrealized Loss Positions) (Details) - USD ($) $ in Millions		Dec. 31, 2015		Dec. 31, 2014
Temporarily Impaired Less than 12 Months, Fair Value		$ 4,944		$ 924
Temporarily Impaired, Less than 12 Months, Unrealized Losses		28		3
Temporarily Impaired 12 Months or more, Fair Value		1,986		3,247
Temporarily Impaired, 12 Months or more, Unrealized Losses		51		73
Temporarily Impaired Total, Fair Value		6,930		4,171
Temporarily Impaired Total, Unrealized Losses		79		76
U.S. Treasury and other U.S. government agency securities
Temporarily Impaired Less than 12 Months, Fair Value		2,265		298
Temporarily Impaired, Less than 12 Months, Unrealized Losses		7		0	[1]
Temporarily Impaired 12 Months or more, Fair Value		0		0
Temporarily Impaired, 12 Months or more, Unrealized Losses		0		0
Temporarily Impaired Total, Fair Value		2,265		298
Temporarily Impaired Total, Unrealized Losses		7		0	[1]
Residential mortgage-backed securities
Temporarily Impaired Less than 12 Months, Fair Value	[2]	2,665		626
Temporarily Impaired, Less than 12 Months, Unrealized Losses	[2]	21		3
Temporarily Impaired 12 Months or more, Fair Value	[2]	1,976		3,112
Temporarily Impaired, 12 Months or more, Unrealized Losses	[2]	51		71
Temporarily Impaired Total, Fair Value	[2]	4,641		3,738
Temporarily Impaired Total, Unrealized Losses	[2]	72		74
State and municipal securities
Temporarily Impaired Less than 12 Months, Fair Value	[3]	0		0
Temporarily Impaired, Less than 12 Months, Unrealized Losses	[3]	0		0
Temporarily Impaired 12 Months or more, Fair Value	[3]	9		22
Temporarily Impaired, 12 Months or more, Unrealized Losses	[3]	0	[1]	1
Temporarily Impaired Total, Fair Value	[3]	9		22
Temporarily Impaired Total, Unrealized Losses	[3]	0	[1]	1
Corporate debt securities
Temporarily Impaired Less than 12 Months, Fair Value	[3]	0		0
Temporarily Impaired, Less than 12 Months, Unrealized Losses	[3]	0		0
Temporarily Impaired 12 Months or more, Fair Value	[3]	1		1
Temporarily Impaired, 12 Months or more, Unrealized Losses	[1],[3]	0		0
Temporarily Impaired Total, Fair Value	[3]	1		1
Temporarily Impaired Total, Unrealized Losses	[1],[3]	0		0
Equity and other non-debt securities
Temporarily Impaired Less than 12 Months, Fair Value	[3]	14		0
Temporarily Impaired, Less than 12 Months, Unrealized Losses	[3]	0	[1]	0
Temporarily Impaired 12 Months or more, Fair Value	[3]	0		112
Temporarily Impaired, 12 Months or more, Unrealized Losses	[3]	0		1
Temporarily Impaired Total, Fair Value	[3]	14		112
Temporarily Impaired Total, Unrealized Losses	[3]	$ 0	[1]	$ 1
[1]	Unrealized losses less than $0.5 million.
[2]	Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.
[3]	Primarily auction-rate securities.

Investment Securities (Gains An

Investment Securities (Gains And Losses On Available-For-Sale Securities) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Securities gains									$ 0	$ 2	$ 1
Securities losses									(2)	(2)	(2)
Net securities losses	$ 0	$ 0	$ 0	$ (2)	$ 0	$ (1)	$ 0	$ 1	$ (2)	$ 0	$ (1)

Investment Securities (Contract

Investment Securities (Contractual Maturity Distribution Of Debt Securities) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Available-for-Sale, Within one year, Amortized Cost		$ 10
Available-for-Sale, After one year through five years, Amortized Cost		2,857
Available-for-Sale, After five years through ten years, Amortized Cost		1,268
Available-for-Sale, After ten years, Amortized Cost		6,157
Available-for-Sale, Subtotal, Amortized Cost		10,292
Available-for-Sale, Within one year, Fair Value		10
Available-for-Sale, After one year through five years, Fair Value		2,851
Available-for-Sale, After five years through ten years, Fair Value		1,308
Availabie-for-Sale, After ten years, Fair Value		6,149
Available-for-Sale, Subtotal, Fair Value		10,318
Total investment securities available-for-sale, Amortized Cost	[1]	10,491	$ 8,035
Investment securities available-for-sale, Fair Value	[1]	10,519	8,116
Held-to-maturity, Within one year, Net Carrying Amount		0
Held-to-maturity, After one year through five years, Net Carrying Amount		0
Held-to-maturity, After five years through ten years, Net Carrying Amount		0
Held-to-maturity, After ten years, Net Carrying Amount		1,981
Total investment securities held-to-maturity, Net Carrying Amount		1,981	1,935
Held-to-maturity, Within one year, Fair Value		0
Held-to-maturity, After one year through five years, Fair Value		0
Held-to-maturity, After five years through ten years, Fair Value		0
Held-to-maturity, After ten years, Fair Value		1,973
Investment securities held-to-maturity, Fair Value		1,973
Equity and other non-debt securities
Total investment securities available-for-sale, Amortized Cost		199	242
Investment securities available-for-sale, Fair Value		201	$ 242
Total investment securities held-to-maturity, Net Carrying Amount		0
Investment securities held-to-maturity, Fair Value		$ 0
[1]	Included auction-rate securities at amortized cost and fair value of $76 million and $77 million, respectively, as of December 31, 2015 and $137 million and $136 million, respectively, as of December 31, 2014.

Credit Quality And Allowance 67

Credit Quality And Allowance For Credit Losses (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Reduced-rate loans	[1]	$ 12	$ 17
Retail loans secured by residential real estate in process of foreclosure		1
Commitments to lend additional funds to TDR borrowers		6	3
Interest rate reductions
Carrying value at period end of loans modified during the period		$ 2	$ 3
Days past due when a loan is said to be in subsequent payment default		90 days	90 days
Subsequent Default During Period		$ 0	$ 0
Business loans
Reduced-rate loans		0	0
Retail loans
Reduced-rate loans		$ 12	$ 17
[1]	There were no reduced-rate business loans at both December 31, 2015 and at December 31, 2014. Reduced-rate retail loans totaled $12 million and $17 million at December 31, 2015 and 2014, respectively.

Credit Quality And Allowance 68

Credit Quality And Allowance For Credit Losses (Aging Analysis Of Loans) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		$ 146	$ 168
Nonaccrual loans		367	273
Current loans		48,571	48,152
Total loans		49,084	48,593
30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		108	132
60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		21	31
90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		17	5
Real estate construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		2,001	1,955
Real estate construction | Commercial Real Estate business line
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[1]	1,681	1,606
Real estate construction | Other business lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[2]	320	349
Real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans		8,977	8,604
Real estate | Commercial Real Estate business line
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[1]	2,104	1,790
Real estate | Other business lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	[2]	6,873	6,814
Business loans | Commercial borrower
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		104	136
Nonaccrual loans		313	206
Current loans		44,312	44,038
Total loans		44,729	44,380
Business loans | Commercial borrower | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		70	106
Business loans | Commercial borrower | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		17	26
Business loans | Commercial borrower | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		17	4
Business loans | Commercial borrower | Domestic loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		71	72
Nonaccrual loans		238	109
Current loans		31,350	31,339
Total loans		31,659	31,520
Business loans | Commercial borrower | Domestic loans | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		46	58
Business loans | Commercial borrower | Domestic loans | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		12	13
Business loans | Commercial borrower | Domestic loans | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		13	1
Business loans | Commercial borrower | International loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		2	9
Nonaccrual loans		8	0
Current loans		1,358	1,487
Total loans		1,368	1,496
Business loans | Commercial borrower | International loans | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		2	9
Business loans | Commercial borrower | International loans | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		0	0
Business loans | Commercial borrower | International loans | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		0	0
Business loans | Real estate construction | Commercial borrower | Domestic loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		8	15
Nonaccrual loans		1	2
Current loans		1,992	1,938
Total loans		2,001	1,955
Business loans | Real estate construction | Commercial borrower | Domestic loans | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		8	15
Business loans | Real estate construction | Commercial borrower | Domestic loans | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		0	0
Business loans | Real estate construction | Commercial borrower | Domestic loans | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		0	0
Business loans | Real estate construction | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[3]	5	3
Nonaccrual loans	[3]	0	1
Current loans	[3]	1,676	1,602
Total loans	[3],[4]	1,681	1,606
Business loans | Real estate construction | Commercial borrower | Domestic loans | Commercial Real Estate business line | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[3]	5	3
Business loans | Real estate construction | Commercial borrower | Domestic loans | Commercial Real Estate business line | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[3]	0	0
Business loans | Real estate construction | Commercial borrower | Domestic loans | Commercial Real Estate business line | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[3]	0	0
Business loans | Real estate construction | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[5]	3	12
Nonaccrual loans	[5]	1	1
Current loans	[5]	316	336
Total loans	[5],[6]	320	349
Business loans | Real estate construction | Commercial borrower | Domestic loans | Other business lines | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[5]	3	12
Business loans | Real estate construction | Commercial borrower | Domestic loans | Other business lines | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[5]	0	0
Business loans | Real estate construction | Commercial borrower | Domestic loans | Other business lines | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[5]	0	0
Business loans | Real estate | Commercial borrower | Domestic loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		23	40
Nonaccrual loans		60	95
Current loans		8,894	8,469
Total loans		8,977	8,604
Business loans | Real estate | Commercial borrower | Domestic loans | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		14	24
Business loans | Real estate | Commercial borrower | Domestic loans | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		5	13
Business loans | Real estate | Commercial borrower | Domestic loans | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		4	3
Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[3]	8	10
Nonaccrual loans	[3]	16	22
Current loans	[3]	2,080	1,758
Total loans	[3],[4]	2,104	1,790
Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[3]	7	8
Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[3]	0	1
Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[3]	1	1
Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[5]	15	30
Nonaccrual loans	[5]	44	73
Current loans	[5]	6,814	6,711
Total loans	[5],[6]	6,873	6,814
Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[5]	7	16
Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[5]	5	12
Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing	[5]	3	2
Business loans | Lease financing | Commercial borrower | Domestic loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		0	0
Nonaccrual loans		6	0
Current loans		718	805
Total loans		724	805
Business loans | Lease financing | Commercial borrower | Domestic loans | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		0	0
Business loans | Lease financing | Commercial borrower | Domestic loans | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		0	0
Business loans | Lease financing | Commercial borrower | Domestic loans | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		0	0
Retail loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		42	32
Nonaccrual loans		54	67
Current loans		4,259	4,114
Total loans		4,355	4,213
Retail loans | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		38	26
Retail loans | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		4	5
Retail loans | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		0	1
Retail loans | Consumer borrower
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		15	21
Nonaccrual loans		27	31
Current loans		2,443	2,330
Total loans		2,485	2,382
Retail loans | Consumer borrower | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		12	17
Retail loans | Consumer borrower | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		3	3
Retail loans | Consumer borrower | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		0	1
Retail loans | Real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		27	11
Nonaccrual loans		27	36
Current loans		1,816	1,784
Total loans		1,870	1,831
Retail loans | Real estate | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		26	9
Retail loans | Real estate | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		1	2
Retail loans | Real estate | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		0	0
Retail loans | Home equity | Consumer borrower
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		8	8
Nonaccrual loans		27	30
Current loans		1,685	1,620
Total loans		1,720	1,658
Retail loans | Home equity | Consumer borrower | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		5	5
Retail loans | Home equity | Consumer borrower | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		3	3
Retail loans | Home equity | Consumer borrower | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		0	0
Retail loans | Other consumer | Consumer borrower
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		7	13
Nonaccrual loans		0	1
Current loans		758	710
Total loans		765	724
Retail loans | Other consumer | Consumer borrower | 30 to 59 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		7	12
Retail loans | Other consumer | Consumer borrower | 60 to 89 days past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		0	0
Retail loans | Other consumer | Consumer borrower | 90 days or more past due and still accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans past due and still accruing		$ 0	$ 1
[1]	Primarily loans to real estate developers.
[2]	Primarily loans secured by owner-occupied real estate.
[3]	Primarily loans to real estate developers.
[4]	Primarily loans to real estate developers.
[5]	Primarily loans secured by owner-occupied real estate.
[6]	Primarily loans secured by owner-occupied real estate.

Credit Quality And Allowance 69

Credit Quality And Allowance For Credit Losses (Loans By Credit Quality Indicator) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Total loans		$ 49,084	$ 48,593
Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1]	45,891	46,700
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	1,579	831
Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3]	1,247	789
Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4]	367	273
Real estate construction
Financing Receivable, Recorded Investment [Line Items]
Total loans		2,001	1,955
Real estate construction | Commercial Real Estate business line
Financing Receivable, Recorded Investment [Line Items]
Total loans	[5]	1,681	1,606
Real estate construction | Other business lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	[6]	320	349
Real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans		8,977	8,604
Real estate | Commercial Real Estate business line
Financing Receivable, Recorded Investment [Line Items]
Total loans	[5]	2,104	1,790
Real estate | Other business lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	[6]	6,873	6,814
Business loans | Commercial borrower
Financing Receivable, Recorded Investment [Line Items]
Total loans		44,729	44,380
Business loans | Commercial borrower | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1]	41,621	42,572
Business loans | Commercial borrower | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	1,573	826
Business loans | Commercial borrower | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3]	1,222	776
Business loans | Commercial borrower | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4]	313	206
Business loans | Commercial borrower | Domestic loans
Financing Receivable, Recorded Investment [Line Items]
Total loans		31,659	31,520
Business loans | Commercial borrower | Domestic loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1]	29,117	30,310
Business loans | Commercial borrower | Domestic loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	1,293	560
Business loans | Commercial borrower | Domestic loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3]	1,011	541
Business loans | Commercial borrower | Domestic loans | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4]	238	109
Business loans | Commercial borrower | International loans
Financing Receivable, Recorded Investment [Line Items]
Total loans		1,368	1,496
Business loans | Commercial borrower | International loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1]	1,245	1,468
Business loans | Commercial borrower | International loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	59	15
Business loans | Commercial borrower | International loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3]	56	13
Business loans | Commercial borrower | International loans | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4]	8	0
Business loans | Real estate construction | Commercial borrower | Domestic loans
Financing Receivable, Recorded Investment [Line Items]
Total loans		2,001	1,955
Business loans | Real estate construction | Commercial borrower | Domestic loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1]	1,999	1,930
Business loans | Real estate construction | Commercial borrower | Domestic loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	1	18
Business loans | Real estate construction | Commercial borrower | Domestic loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3]	0	5
Business loans | Real estate construction | Commercial borrower | Domestic loans | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4]	1	2
Business loans | Real estate construction | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Recorded Investment [Line Items]
Total loans	[7],[8]	1,681	1,606
Business loans | Real estate construction | Commercial borrower | Domestic loans | Commercial Real Estate business line | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1],[7]	1,681	1,594
Business loans | Real estate construction | Commercial borrower | Domestic loans | Commercial Real Estate business line | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2],[7]	0	11
Business loans | Real estate construction | Commercial borrower | Domestic loans | Commercial Real Estate business line | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3],[7]	0	0
Business loans | Real estate construction | Commercial borrower | Domestic loans | Commercial Real Estate business line | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4],[7]	0	1
Business loans | Real estate construction | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	[9],[10]	320	349
Business loans | Real estate construction | Commercial borrower | Domestic loans | Other business lines | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1],[9]	318	336
Business loans | Real estate construction | Commercial borrower | Domestic loans | Other business lines | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2],[9]	1	7
Business loans | Real estate construction | Commercial borrower | Domestic loans | Other business lines | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3],[9]	0	5
Business loans | Real estate construction | Commercial borrower | Domestic loans | Other business lines | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4],[9]	1	1
Business loans | Real estate | Commercial borrower | Domestic loans
Financing Receivable, Recorded Investment [Line Items]
Total loans		8,977	8,604
Business loans | Real estate | Commercial borrower | Domestic loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1]	8,567	8,086
Business loans | Real estate | Commercial borrower | Domestic loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	203	207
Business loans | Real estate | Commercial borrower | Domestic loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3]	147	216
Business loans | Real estate | Commercial borrower | Domestic loans | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4]	60	95
Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Recorded Investment [Line Items]
Total loans	[7],[8]	2,104	1,790
Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1],[7]	2,031	1,652
Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2],[7]	31	69
Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3],[7]	26	47
Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4],[7]	16	22
Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Recorded Investment [Line Items]
Total loans	[9],[10]	6,873	6,814
Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1],[9]	6,536	6,434
Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2],[9]	172	138
Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3],[9]	121	169
Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4],[9]	44	73
Business loans | Lease financing | Commercial borrower | Domestic loans
Financing Receivable, Recorded Investment [Line Items]
Total loans		724	805
Business loans | Lease financing | Commercial borrower | Domestic loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1]	693	778
Business loans | Lease financing | Commercial borrower | Domestic loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	17	26
Business loans | Lease financing | Commercial borrower | Domestic loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3]	8	1
Business loans | Lease financing | Commercial borrower | Domestic loans | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4]	6	0
Retail loans
Financing Receivable, Recorded Investment [Line Items]
Total loans		4,355	4,213
Retail loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1]	4,270	4,128
Retail loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	6	5
Retail loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3]	25	13
Retail loans | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4]	54	67
Retail loans | Consumer borrower
Financing Receivable, Recorded Investment [Line Items]
Total loans		2,485	2,382
Retail loans | Consumer borrower | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1]	2,442	2,338
Retail loans | Consumer borrower | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	4	3
Retail loans | Consumer borrower | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3]	12	10
Retail loans | Consumer borrower | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4]	27	31
Retail loans | Real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans		1,870	1,831
Retail loans | Real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1]	1,828	1,790
Retail loans | Real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	2	2
Retail loans | Real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3]	13	3
Retail loans | Real estate | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4]	27	36
Retail loans | Home equity | Consumer borrower
Financing Receivable, Recorded Investment [Line Items]
Total loans		1,720	1,658
Retail loans | Home equity | Consumer borrower | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1]	1,687	1,620
Retail loans | Home equity | Consumer borrower | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	1	0
Retail loans | Home equity | Consumer borrower | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3]	5	8
Retail loans | Home equity | Consumer borrower | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4]	27	30
Retail loans | Other consumer | Consumer borrower
Financing Receivable, Recorded Investment [Line Items]
Total loans		765	724
Retail loans | Other consumer | Consumer borrower | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	[1]	755	718
Retail loans | Other consumer | Consumer borrower | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	[2]	3	3
Retail loans | Other consumer | Consumer borrower | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	[3]	7	2
Retail loans | Other consumer | Consumer borrower | Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	[4]	$ 0	$ 1
[1]	Includes all loans not included in the categories of special mention, substandard or nonaccrual.
[2]	Special mention loans are accruing loans that have potential credit weaknesses that deserve management’s close attention, such as loans to borrowers who may be experiencing financial difficulties that may result in deterioration of repayment prospects from the borrower at some future date. This category is generally consistent with the "special mention" category as defined by regulatory authorities.
[3]	Substandard loans are accruing loans that have a well-defined weakness, or weaknesses, such as loans to borrowers who may be experiencing losses from operations or inadequate liquidity of a degree and duration that jeopardizes the orderly repayment of the loan. Substandard loans also are distinguished by the distinct possibility of loss in the future if these weaknesses are not corrected. PCI loans are included in the substandard category. This category is generally consistent with the "substandard" category as defined by regulatory authorities.
[4]	Nonaccrual loans are loans for which the accrual of interest has been discontinued. For further information regarding nonaccrual loans, refer to the Nonperforming Assets subheading in Note 1 - Basis of Presentation and Accounting Policies. A significant majority of nonaccrual loans are generally consistent with the "substandard" category and the remainder are generally consistent with the "doubtful" category as defined by regulatory authorities.
[5]	Primarily loans to real estate developers.
[6]	Primarily loans secured by owner-occupied real estate.
[7]	Primarily loans to real estate developers.
[8]	Primarily loans to real estate developers.
[9]	Primarily loans secured by owner-occupied real estate.
[10]	Primarily loans secured by owner-occupied real estate.

Credit Quality And Allowance 70

Credit Quality And Allowance For Credit Losses (Schedule Of Nonaccrual, Reduced-Rate Loans And Foreclosed Property) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Nonaccrual loans		$ 367	$ 273
Reduced-rate loans	[1]	12	17
Total nonperforming loans		379	290
Foreclosed property		12	10
Total nonperforming assets		391	300
Business loans
Reduced-rate loans		0	0
Retail loans
Nonaccrual loans		54	67
Reduced-rate loans		$ 12	$ 17
[1]	There were no reduced-rate business loans at both December 31, 2015 and at December 31, 2014. Reduced-rate retail loans totaled $12 million and $17 million at December 31, 2015 and 2014, respectively.

Credit Quality And Allowance 71

Credit Quality And Allowance For Credit Losses (Changes In The Allowance For Loan Losses And Related Loan Amounts) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		$ 60	$ 26	$ 47	$ 14	$ 2	$ 5	$ 11	$ 9	$ 147	$ 27	$ 46
Total loans													$ 49,084	$ 48,593
Allowance for loan losses on PCI loans													$ 0	$ 0	$ 0
Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period					594				598	594	598	629
Loan charge-offs										(168)	(102)	(153)
Recoveries on loans previously charged-off										68	77	80
Net loan (charge-offs) recoveries										(100)	(25)	(73)
Provision for loan losses										142	22	42
Foreign currency translation adjustment										(2)	(1)	0
Balance at end of period		634				594				634	594	598
Allowance for loan losses as a percentage of total loans													1.29%	1.22%	1.32%
Allowance for loan losses individually evaluated for impairment													$ 53	$ 39	$ 57
Allowance for loan losses collectively evaluated for impairment													581	555	541
Total allowance for loan losses		634			594	594			598	594	598	629	634	594	598
Loans individually evaluated for impairment													424	219	274
Loans collectively evaluated for impairment													48,659	48,372	45,191
PCI loans	[1]												1	2	5
Total loans													$ 49,084	$ 48,593	$ 45,470
Business loans | Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period					534				531	534	531	552
Loan charge-offs										(157)	(87)	(130)
Recoveries on loans previously charged-off										55	68	70
Net loan (charge-offs) recoveries										(102)	(19)	(60)
Provision for loan losses										149	23	39
Foreign currency translation adjustment										(2)	(1)	0
Balance at end of period		579				534				579	534	531
Allowance for loan losses as a percentage of total loans													1.30%	1.20%	1.28%
Allowance for loan losses individually evaluated for impairment													$ 53	$ 39	$ 57
Allowance for loan losses collectively evaluated for impairment													526	495	474
Total allowance for loan losses		579			534	534			531	534	531	552	579	534	531
Loans individually evaluated for impairment													393	177	223
Loans collectively evaluated for impairment													44,336	44,203	41,311
PCI loans	[1]												0	0	2
Total loans													44,729	44,380	$ 41,536
Retail loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans													$ 4,355	$ 4,213
Retail loans | Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period					60				67	60	67	77
Loan charge-offs										(11)	(15)	(23)
Recoveries on loans previously charged-off										13	9	10
Net loan (charge-offs) recoveries										2	(6)	(13)
Provision for loan losses										(7)	(1)	3
Foreign currency translation adjustment										0	0	0
Balance at end of period		55				60				55	60	67
Allowance for loan losses as a percentage of total loans													1.26%	1.43%	1.70%
Allowance for loan losses individually evaluated for impairment													$ 0	$ 0	$ 0
Allowance for loan losses collectively evaluated for impairment													55	60	67
Total allowance for loan losses		$ 55			$ 60	$ 60			$ 67	$ 60	$ 67	$ 77	55	60	67
Loans individually evaluated for impairment													31	42	51
Loans collectively evaluated for impairment													4,323	4,169	3,880
PCI loans	[1]												1	2	3
Total loans													$ 4,355	$ 4,213	$ 3,934
[1]	No allowance for loan losses was required for PCI loans at December 31, 2015, 2014 and 2013.

Credit Quality And Allowance 72

Credit Quality And Allowance For Credit Losses (Changes In The Allowance For Credit Losses On Lending-Related Commitments) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for credit losses on lending-related commitments		$ 60	$ 26	$ 47	$ 14	$ 2	$ 5	$ 11	$ 9	$ 147	$ 27	$ 46
Lending-related commitments
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period					$ 41				$ 36	41	36	32
Charge-offs on lending related commitments	[1]									(1)	0	0
Provision for credit losses on lending-related commitments										5	5	4
Balance at end of period		$ 45				$ 41				$ 45	$ 41	$ 36
[1]	(a) Charge-offs result from the sale of unfunded lending-related commitments.

Credit Quality And Allowance 73

Credit Quality And Allowance For Credit Losses (Individually Evaluated Impaired Loans) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Recorded investment in impaired loans with no related allowance		$ 122	$ 53
Recorded investment in impaired loans with related allowance		302	166
Recorded investment total impaired loans		424	219
Unpaid principal balance		698	304
Related allowance for loan losses		53	39
Business loans | Commercial borrower
Financing Receivable, Impaired [Line Items]
Recorded investment in impaired loans with no related allowance		91	11
Recorded investment in impaired loans with related allowance		302	166
Recorded investment total impaired loans		393	177
Unpaid principal balance		659	253
Related allowance for loan losses		53	39
Business loans | Commercial borrower | Domestic loans
Financing Receivable, Impaired [Line Items]
Recorded investment in impaired loans with no related allowance		82	7
Recorded investment in impaired loans with related allowance		252	103
Recorded investment total impaired loans		334	110
Unpaid principal balance		549	148
Related allowance for loan losses		45	29
Business loans | Commercial borrower | International loans
Financing Receivable, Impaired [Line Items]
Recorded investment in impaired loans with no related allowance		0
Recorded investment in impaired loans with related allowance		10
Recorded investment total impaired loans		10
Unpaid principal balance		17
Related allowance for loan losses		2
Business loans | Real estate construction | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Impaired [Line Items]
Recorded investment in impaired loans with no related allowance	[1]		0
Recorded investment in impaired loans with related allowance	[1]		1
Recorded investment total impaired loans	[1]		1
Unpaid principal balance	[1]		1
Related allowance for loan losses	[1]		0
Business loans | Real estate | Commercial borrower | Domestic loans
Financing Receivable, Impaired [Line Items]
Recorded investment in impaired loans with no related allowance		9	4
Recorded investment in impaired loans with related allowance		40	62
Recorded investment total impaired loans		49	66
Unpaid principal balance		93	104
Related allowance for loan losses		6	10
Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Impaired [Line Items]
Recorded investment in impaired loans with no related allowance	[2]	7	0
Recorded investment in impaired loans with related allowance	[2]	8	19
Recorded investment total impaired loans	[2]	15	19
Unpaid principal balance	[2]	38	41
Related allowance for loan losses	[2]	1	8
Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Impaired [Line Items]
Recorded investment in impaired loans with no related allowance	[1]	2	4
Recorded investment in impaired loans with related allowance	[1]	32	43
Recorded investment total impaired loans	[1]	34	47
Unpaid principal balance	[1]	55	63
Related allowance for loan losses	[1]	5	2
Retail loans
Financing Receivable, Impaired [Line Items]
Recorded investment in impaired loans with no related allowance	[3]	31	42
Recorded investment in impaired loans with related allowance	[3]	0	0
Recorded investment total impaired loans	[3]	31	42
Unpaid principal balance	[3]	39	51
Related allowance for loan losses	[3]	0	0
Retail loans | Consumer borrower
Financing Receivable, Impaired [Line Items]
Recorded investment in impaired loans with no related allowance		18	17
Recorded investment in impaired loans with related allowance		0	0
Recorded investment total impaired loans		18	17
Unpaid principal balance		26	23
Related allowance for loan losses		0	0
Retail loans | Real estate
Financing Receivable, Impaired [Line Items]
Recorded investment in impaired loans with no related allowance		13	25
Recorded investment in impaired loans with related allowance		0	0
Recorded investment total impaired loans		13	25
Unpaid principal balance		13	28
Related allowance for loan losses		0	0
Retail loans | Home equity | Consumer borrower
Financing Receivable, Impaired [Line Items]
Recorded investment in impaired loans with no related allowance		12	12
Recorded investment in impaired loans with related allowance		0	0
Recorded investment total impaired loans		12	12
Unpaid principal balance		16	16
Related allowance for loan losses		0	0
Retail loans | Other consumer | Consumer borrower
Financing Receivable, Impaired [Line Items]
Recorded investment in impaired loans with no related allowance		6	5
Recorded investment in impaired loans with related allowance		0	0
Recorded investment total impaired loans		6	5
Unpaid principal balance		10	7
Related allowance for loan losses		$ 0	$ 0
[1]	Primarily loans secured by owner-occupied real estate.
[2]	Primarily loans to real estate developers.
[3]	Individually evaluated retail loans had no related allowance for loan losses, primarily due to policy which results in direct write-downs of restructured retail loans.

Credit Quality And Allowance 74

Credit Quality And Allowance For Credit Losses (Average Individually Evaluated Impaired Loans And Related Interest Recognized) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Individually Evaluated Impaired Loans Average Balance for the Period		$ 306	$ 251	$ 358
Individually Evaluated Impaired Loans Interest Income Recognized for the Period		6	4	5
Business loans | Commercial borrower
Financing Receivable, Impaired [Line Items]
Individually Evaluated Impaired Loans Average Balance for the Period		267	205	311
Individually Evaluated Impaired Loans Interest Income Recognized for the Period		6	4	5
Business loans | Commercial borrower | Domestic loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated Impaired Loans Average Balance for the Period		206	77	99
Individually Evaluated Impaired Loans Interest Income Recognized for the Period		5	2	2
Business loans | Commercial borrower | International loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated Impaired Loans Average Balance for the Period		6	2	1
Individually Evaluated Impaired Loans Interest Income Recognized for the Period		0	0	0
Business loans | Real estate construction | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Impaired [Line Items]
Individually Evaluated Impaired Loans Average Balance for the Period	[1]	0	14	25
Individually Evaluated Impaired Loans Interest Income Recognized for the Period	[1]	0	0	0
Business loans | Real estate | Commercial borrower | Domestic loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated Impaired Loans Average Balance for the Period		55	112	186
Individually Evaluated Impaired Loans Interest Income Recognized for the Period		1	2	3
Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Impaired [Line Items]
Individually Evaluated Impaired Loans Average Balance for the Period	[1]	16	48	81
Individually Evaluated Impaired Loans Interest Income Recognized for the Period	[1]	0	0	0
Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Impaired [Line Items]
Individually Evaluated Impaired Loans Average Balance for the Period	[2]	39	64	105
Individually Evaluated Impaired Loans Interest Income Recognized for the Period	[2]	1	2	3
Retail loans
Financing Receivable, Impaired [Line Items]
Individually Evaluated Impaired Loans Average Balance for the Period		39	46	47
Individually Evaluated Impaired Loans Interest Income Recognized for the Period		0	0	0
Retail loans | Consumer borrower
Financing Receivable, Impaired [Line Items]
Individually Evaluated Impaired Loans Average Balance for the Period		18	16	12
Individually Evaluated Impaired Loans Interest Income Recognized for the Period		0	0	0
Retail loans | Real estate
Financing Receivable, Impaired [Line Items]
Individually Evaluated Impaired Loans Average Balance for the Period		21	30	35
Individually Evaluated Impaired Loans Interest Income Recognized for the Period		0	0	0
Retail loans | Home equity | Consumer borrower
Financing Receivable, Impaired [Line Items]
Individually Evaluated Impaired Loans Average Balance for the Period		12	12	8
Individually Evaluated Impaired Loans Interest Income Recognized for the Period		0	0	0
Retail loans | Other consumer | Consumer borrower
Financing Receivable, Impaired [Line Items]
Individually Evaluated Impaired Loans Average Balance for the Period		6	4	4
Individually Evaluated Impaired Loans Interest Income Recognized for the Period		$ 0	$ 0	$ 0
[1]	Primarily loans to real estate developers.
[2]	Primarily loans secured by owner-occupied real estate.

Credit Quality And Allowance 75

Credit Quality And Allowance For Credit Losses (Troubled Debt Restructurings By Type Of Modification) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		$ 179	$ 34
Business loans | Commercial borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		176	28
Business loans | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		160	22
Business loans | Commercial borrower | International loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		2	0
Business loans | Real estate | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		14	6
Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[1]	8	0
Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[2]	6	6
Retail loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		3	6
Retail loans | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		3	5
Retail loans | Real estate
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	1
Retail loans | Home equity | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		3	4
Retail loans | Other consumer | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	1
Principal deferrals
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	$ 177	$ 31
Minimum period loan terms were extended		90 days	90 days
Principal deferrals | Business loans | Commercial borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	$ 176	$ 28
Principal deferrals | Business loans | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	160	22
Principal deferrals | Business loans | Commercial borrower | International loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	2	0
Principal deferrals | Business loans | Real estate | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	14	6
Principal deferrals | Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[1],[3]	8	0
Principal deferrals | Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[2],[3]	6	6
Principal deferrals | Retail loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	1	3
Principal deferrals | Retail loans | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	1	2
Principal deferrals | Retail loans | Real estate
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	0	1	[4]
Principal deferrals | Retail loans | Home equity | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3],[4]	1	1
Principal deferrals | Retail loans | Other consumer | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	0	1	[4]
Interest rate reductions
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		2	3
Interest rate reductions | Business loans | Commercial borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	0
Interest rate reductions | Business loans | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	0
Interest rate reductions | Business loans | Commercial borrower | International loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	0
Interest rate reductions | Business loans | Real estate | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	0
Interest rate reductions | Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[1]	0	0
Interest rate reductions | Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[2]	0	0
Interest rate reductions | Retail loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		2	3
Interest rate reductions | Retail loans | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		2	3
Interest rate reductions | Retail loans | Real estate
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	0
Interest rate reductions | Retail loans | Home equity | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		2	3
Interest rate reductions | Retail loans | Other consumer | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		$ 0	$ 0
[1]	Primarily loans to real estate developers.
[2]	Primarily loans secured by owner-occupied real estate.
[3]	Primarily represents loan balances where terms were extended 90 days or more at or above contractual interest rates.
[4]	Includes bankruptcy loans for which the court has discharged the borrower's obligation and the borrower has not reaffirmed the debt.

Credit Quality And Allowance 76

Credit Quality And Allowance For Credit Losses Credit Quality And Allowance For Credit Losses (Troubled Debt Restructuring Subsequent Default) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Principal deferrals
Financing Receivable, Modifications [Line Items]
Balance		$ 177	$ 31
Subsequent Default During Period		18	3
Principal deferrals | Business loans | Commercial borrower
Financing Receivable, Modifications [Line Items]
Balance		176	28
Subsequent Default During Period		18	3
Principal deferrals | Business loans | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Balance		160	22
Subsequent Default During Period		16	1
Principal deferrals | Business loans | Commercial borrower | International loans
Financing Receivable, Modifications [Line Items]
Balance		2	0
Subsequent Default During Period		0	0
Principal deferrals | Business loans | Real estate | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Balance		14	6
Subsequent Default During Period		2	2
Principal deferrals | Business loans | Real estate | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Modifications [Line Items]
Balance	[1]	8	0
Subsequent Default During Period	[1]	1	0
Principal deferrals | Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Modifications [Line Items]
Balance	[2]	6	6
Subsequent Default During Period	[2]	1	2
Principal deferrals | Retail loans
Financing Receivable, Modifications [Line Items]
Balance		1	3
Subsequent Default During Period		0	0
Principal deferrals | Retail loans | Consumer borrower
Financing Receivable, Modifications [Line Items]
Balance		1	2
Subsequent Default During Period		0	0
Principal deferrals | Retail loans | Home equity | Consumer borrower
Financing Receivable, Modifications [Line Items]
Balance	[3]	1	1
Subsequent Default During Period		0	0
Principal deferrals | Retail loans | Real estate
Financing Receivable, Modifications [Line Items]
Balance		0	1	[3]
Subsequent Default During Period		0	0
Principal deferrals | Retail loans | Other consumer | Consumer borrower
Financing Receivable, Modifications [Line Items]
Balance		0	1	[3]
Subsequent Default During Period		0	0
Interest rate reductions
Financing Receivable, Modifications [Line Items]
Balance		2	3
Subsequent Default During Period		$ 0	$ 0
[1]	Primarily loans to real estate developers.
[2]	Primarily loans secured by owner-occupied real estate.
[3]	Includes bankruptcy loans for which the court has discharged the borrower's obligation and the borrower has not reaffirmed the debt.

Significant Group Concentrati77

Significant Group Concentrations of Credit Risk Significant Group Concentrations of Credit Risk (Schedule of Automotive Industry Outstanding Loans and Total Exposure) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Concentration Risk [Line Items]
Total automotive loans	$ 7,839	$ 7,667
Total automotive exposure	10,661	10,171
Automotive Production
Concentration Risk [Line Items]
Total automotive loans	1,266	1,236
Total automotive exposure	2,452	2,408
Automotive Dealer
Concentration Risk [Line Items]
Total automotive loans	6,573	6,431
Total automotive exposure	$ 8,209	$ 7,763

Significant Group Concentrati78

Significant Group Concentrations of Credit Risk Significant Group Concentrations of Credit Risk (Commercial Real Estate Exposure) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		$ 49,084	$ 48,593
Real estate construction loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		2,001	1,955
Commercial mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		8,977	8,604
Total commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		10,978	10,559
Total unused commitments		3,063	2,335
Commercial Real Estate business line | Real estate construction loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	[1]	1,681	1,606
Commercial Real Estate business line | Commercial mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	[1]	2,104	1,790
Other business lines | Real estate construction loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	[2]	320	349
Other business lines | Commercial mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	[2]	$ 6,873	$ 6,814
[1]	Primarily loans to real estate developers.
[2]	Primarily loans secured by owner-occupied real estate.

Premises and Equipment (Narrati

Premises and Equipment (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Abstract]
Rental expense for leased properties and equipment	$ 79	$ 89	$ 78
Lease termination charges included in rental expense		$ 10

Premises and Equipment (Summary

Premises and Equipment (Summary of Premises and Equipment) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Land	$ 87	$ 88
Buildings and improvements	862	808
Furniture and equipment	490	508
Total cost	1,439	1,404
Accumulated depreciation and amortization	(889)	(872)
Net book value	$ 550	$ 532

Premises and Equipment (Schedul

Premises and Equipment (Schedule of Future Minimum Lease Payments) (Details) $ in Millions	Dec. 31, 2015USD ($)
Property, Plant and Equipment [Abstract]
2,016	$ 73
2,017	70
2,018	62
2,019	53
2,020	44
Thereafter	154
Total	$ 456

Goodwill and Intangible Asset82

Goodwill and Intangible Assets Goodwill and Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Core deposit intangible
Amortization expense of core deposit intangible	$ 3	$ 3

Goodwill and Intangible Asset83

Goodwill and Intangible Assets Goodwill and Intangible Assets (Summary of Changes in Carrying Value of Goodwill) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Balance	$ 635	$ 635	$ 635
Business Bank
Goodwill [Line Items]
Balance	380	380	380
Retail Bank
Goodwill [Line Items]
Balance	194	194	194
Wealth Management
Goodwill [Line Items]
Balance	$ 61	$ 61	$ 61

Goodwill and Intangible Asset84

Goodwill and Intangible Assets Goodwill and Intangible Assets (Summary of CDI Carrying Value and Amortization) (Details) - Core deposit intangible - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Acquired Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 34	$ 34
Accumulated amortization	(24)	(21)
Net carrying amount	$ 10	$ 13

Goodwill and Intangible Asset85

Goodwill and Intangible Assets Goodwill and Intangible Assets (Schedule of Core Deposit Intangible Estimated Future Amortization Expense (Details) - Core deposit intangible - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Acquired Finite-Lived Intangible Assets [Line Items]
2,016	$ 2
2,017	2
2,018	2
2,019	2
2,020	1
Thereafter	1
Total	$ 10	$ 13

Derivative And Credit-Related86

Derivative And Credit-Related Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair value of securities received as collateral for derivative assets	$ 139
Cash received as collateral for derivative assets	354
Fair value of securities pledged as collateral for derivative liabilities	3
Cash posted as collateral for derivative liabilities	3
Aggregate fair value of all derivative instruments with credit-risk contingent features that were in a liability position	2
Aggregate fair value of collateral already posted for derivative instruments with credit-risk-related contingent features	1
Additional collateral that would be required to be posted as collateral if the credit-risk-related contingent features were triggered	1
Net interest income generated by risk management fair value interest rate swaps	70	$ 72
Net gain on interest rate fair value hedge ineffectiveness	1
Net gain (loss) on interest rate fair value hedge ineffectiveness is insignificant		an insignificant amount
Gain (loss) on foreign currency derivatives used as economic hedges	0	$ 0
Net gain on open foreign currency positions	1	1
Allowance for credit losses on lending-related commitments	45	41
Allowance for credit losses on lending-related commitments, unused commitments to extend credit	$ 33	30
Final year of expiration for outstanding letters of credit	2,022
Risk participation agreements covering standby and commercial letters of credit	$ 287	316
Standby and commercial letters of credit outstanding	4,000	4,000
Carrying value of standby and commercial letters of credit included in accrued expenses and other liabilities	49	55
Deferred fees on standby and commercial letters of credit included in accrued expenses and other liabilities	37	44
Allowance for credit losses on lending-related commitments, amount related to standby and commercial letters of credit	12	11
Notional Amount of Derivative Credit Risk Participation Agreements	559	598
Maximum estimated exposure to credit risk participation agreements assuming 100% default	$ 5	$ 7
Weighted average remaining maturity of credit risk participation agreements, in years	2 years 11 months

Derivative And Credit-Related87

Derivative And Credit-Related Financial Instruments (Schedule Of Derivative Instruments) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	$ 20,764	$ 21,562
Fair Value of Gross Derivative Assets		818	894
Fair Value of Gross Derivative Liabilities		610	661
Derivative Assets, Netting Adjustment - Offsetting Liabilities		(127)	(133)
Derivative Liabilities, Netting Adjustment - Offsetting Assets		(127)	(133)
Derivative Assets, Netting Adjustment - Cash Collateral Received		(291)	(262)
Derivative Liabilities, Netting Adjustment - Cash Collateral Posted		(3)	0
Net Derivative Assets Included In Consolidated Balance Sheets	[2]	400	499
Net Derivative Liabilities Included In Consolidated Balance Sheets	[2]	480	528
Derivative Assets, Securities Received As Collateral		(137)	(239)
Derivative Liabilities, Securities Pledged As Collateral		(3)	(2)
Net Derivative Assets After Deducting Amounts Not Offset In Consolidated Balance Sheets		263	260
Net Derivative Liabilities After Deducting Amounts Not Offset In Consolidated Balance Sheets		477	526
Derivative Credit Risk Valuation Adjustment, Derivative Assets		5	2
Risk Management Purposes
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	3,118	2,308
Fair Value of Gross Derivative Assets		150	179
Fair Value of Gross Derivative Liabilities		0	0
Risk Management Purposes | Designated as Hedging Instrument | Fair Value Hedging | Interest Rate Swaps
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	2,525	1,800
Fair Value of Gross Derivative Assets		147	175
Fair Value of Gross Derivative Liabilities		0	0
Risk Management Purposes | Derivatives Used As Economic Hedges | Foreign Exchange Spot, Forwards And Swaps
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	593	508
Fair Value of Gross Derivative Assets		3	4
Fair Value of Gross Derivative Liabilities		0	0
Customer-Initiated And Other Activities
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	17,646	19,254
Fair Value of Gross Derivative Assets		668	715
Fair Value of Gross Derivative Liabilities		610	661
Customer-Initiated And Other Activities | Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	12,228	12,328
Fair Value of Gross Derivative Assets		139	153
Fair Value of Gross Derivative Liabilities		92	102
Customer-Initiated And Other Activities | Interest Rate Caps And Floors Written
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	253	274
Fair Value of Gross Derivative Assets		0	0
Fair Value of Gross Derivative Liabilities		0	0
Customer-Initiated And Other Activities | Interest Rate Caps and Floors Purchased
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	253	274
Fair Value of Gross Derivative Assets		0	0
Fair Value of Gross Derivative Liabilities		0	0
Customer-Initiated And Other Activities | Interest Rate Swaps
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	11,722	11,780
Fair Value of Gross Derivative Assets		139	153
Fair Value of Gross Derivative Liabilities		92	102
Customer-Initiated And Other Activities | Energy Contracts
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	3,127	4,932
Fair Value of Gross Derivative Assets		475	527
Fair Value of Gross Derivative Liabilities		472	525
Customer-Initiated And Other Activities | Energy Caps and Floors Written
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	536	1,218
Fair Value of Gross Derivative Assets		0	0
Fair Value of Gross Derivative Liabilities		85	173
Customer-Initiated And Other Activities | Energy Caps and Floors Purchased
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	536	1,218
Fair Value of Gross Derivative Assets		85	173
Fair Value of Gross Derivative Liabilities		0	0
Customer-Initiated And Other Activities | Energy Swaps
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	2,055	2,496
Fair Value of Gross Derivative Assets		390	354
Fair Value of Gross Derivative Liabilities		387	352
Customer-Initiated And Other Activities | Foreign Exchange Spot, Forwards, Options and Swaps
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	2,291	1,994
Fair Value of Gross Derivative Assets		54	35
Fair Value of Gross Derivative Liabilities		$ 46	$ 34
[1]	Notional or contractual amounts, which represent the extent of involvement in the derivatives market, are used to determine the contractual cash flows required in accordance with the terms of the agreement. These amounts are typically not exchanged, significantly exceed amounts subject to credit or market risk and are not reflected in the consolidated balance sheets.
[2]	Net derivative assets are included in “accrued income and other assets” and net derivative liabilities are included in “accrued expenses and other liabilities” on the consolidated balance sheets. Included in the fair value of net derivative assets and net derivative liabilities are credit valuation adjustments reflecting counterparty credit risk and credit risk of the Corporation. The fair value of net derivative assets included credit valuation adjustments for counterparty credit risk of $5 million at December 31, 2015 and $2 million at December 31, 2014.

Derivative And Credit-Related88

Derivative And Credit-Related Financial Instruments (Schedule Of Weighted Average Maturity And Interest Rates On Risk Management Interest Rate Swaps) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Notional Amount	[1]	$ 20,764	$ 21,562
Risk Management Purposes
Notional Amount	[1]	3,118	2,308
Medium- and Long-term Debt | Swaps - Fair Value Hedge - Receive Fixed/Pay Floating | Risk Management Purposes | Interest Rate Swaps
Notional Amount		$ 2,525	$ 1,800
Weighted Average Remaining Maturity		5 years 1 month	4 years 7 months
Weighted Average Receive Rate		3.89%	4.54%
Weighted Average Pay Rate	[2]	1.11%	0.49%
[1]	Notional or contractual amounts, which represent the extent of involvement in the derivatives market, are used to determine the contractual cash flows required in accordance with the terms of the agreement. These amounts are typically not exchanged, significantly exceed amounts subject to credit or market risk and are not reflected in the consolidated balance sheets.
[2]	Variable rates paid on receive fixed swaps are based on six-month LIBOR rates in effect at December 31, 2015 and 2014.

Derivative And Credit-Related89

Derivative And Credit-Related Financial Instruments (Schedule Of Net Gains Recognized In Income On Customer-Initiated Derivatives) (Details) - Not Designated as Hedging Instrument - Customer-Initiated And Other Activities - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Net derivative gain recognized in income	$ 55	$ 60
Interest Rate Contracts | Other Noninterest Income
Net derivative gain recognized in income	16	20
Energy Contracts | Other Noninterest Income
Net derivative gain recognized in income	2	2
Foreign Exchange Contracts | Foreign Exchange Income
Net derivative gain recognized in income	$ 37	$ 38

Derivative And Credit-Related90

Derivative And Credit-Related Financial Instruments (Schedule Of Financial Instruments With Off-Balance Sheet Credit Risk) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Unused Commitments to Extend Credit
Loss contingency, range of possible loss, maximum	$ 28,529	$ 30,056
Commercial And Other | Unused Commitments to Extend Credit
Loss contingency, range of possible loss, maximum	26,115	27,905
Bankcard, Revolving Check Credit And Home Equity Loan Commitments | Unused Commitments to Extend Credit
Loss contingency, range of possible loss, maximum	2,414	2,151
Standby Letters Of Credit
Loss contingency, range of possible loss, maximum	3,985	3,880
Commercial Letters Of Credit
Loss contingency, range of possible loss, maximum	$ 41	$ 75

Derivative And Credit-Related91

Derivative And Credit-Related Financial Instruments (Summary Of Criticized Letters Of Credit) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Total criticized standby and commercial letters of credit	$ 110	$ 79
As a percentage of total outstanding standby and commercial letters of credit	2.70%	2.00%

Deposits Deposits (Narrative) (

Deposits Deposits (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Deposits [Abstract]
Domestic certificates of deposit of $250,000 or more	$ 1,400	$ 2,000
Foreign office time deposits in denominations of $250,000 or more	$ 32	$ 135

Net Income Per Common Share (Ba

Net Income Per Common Share (Basic And Diluted Net Income Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income	$ 116	$ 136	$ 135	$ 134	$ 149	$ 154	$ 151	$ 139	$ 521	$ 593	$ 541
Less income allocated to participating securities	1	2	1	2	1	2	2	2	6	7	8
Net income attributable to common shares	$ 115	$ 134	$ 134	$ 132	$ 148	$ 152	$ 149	$ 137	$ 515	$ 586	$ 533
Basic average common shares									176	179	183
Basic net income per common share	$ 0.65	$ 0.76	$ 0.76	$ 0.75	$ 0.83	$ 0.85	$ 0.83	$ 0.76	$ 2.93	$ 3.28	$ 2.92
Basic average common shares									176	179	183
Net effect of the assumed exercise of stock options									2	2	1
Net effect of the assumed exercise of warrants									3	4	3
Diluted average common shares									181	185	187
Diluted net income per common share	$ 0.64	$ 0.74	$ 0.73	$ 0.73	$ 0.80	$ 0.82	$ 0.80	$ 0.73	$ 2.84	$ 3.16	$ 2.85

Variable Interest Entities (V94

Variable Interest Entities (VIEs) (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Unfunded commitments to fund tax credit entities	$ 143
Amount of financial or other support not contractually required provided by the Corporation to VIEs	0	$ 0	$ 0
Low Income Housing Tax Credit Entities
Variable Interest Entity [Line Items]
Exposure to loss as a result of involvement with VIEs	405
Other Tax Credit Entities
Variable Interest Entity [Line Items]
Exposure to loss as a result of involvement with VIEs	$ 10

Deposits Deposits (Schedule of

Deposits Deposits (Schedule of Maturities of Certificates of Deposit and Other Deposits with a Stated Maturity) (Details) $ in Millions	Dec. 31, 2015USD ($)
Deposits [Abstract]
2,016	$ 2,792
2,017	503
2,018	132
2,019	83
2,020	51
Thereafter	23
Total	$ 3,584

Net Income Per Common Share (Sc

Net Income Per Common Share (Schedule of Average Shares Excluded From Diluted Net Income Per Common Share Computation) (Details) - Stock Options - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Average outstanding options	5.1	7.2	10.8
Minimum
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Range of exercise prices	$ 46.68	$ 47.24	$ 34.78
Maximum
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Range of exercise prices	$ 60.82	$ 61.94	$ 61.94

Variable Interest Entities (V97

Variable Interest Entities (VIEs) (Impact Of VIEs On The Consolidated Statements Of Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Other noninterest income									$ 103	$ 130	$ 156
Provision for income taxes	$ 41	$ 63	$ 64	$ 61	$ 70	$ 73	$ 70	$ 64	229	277	245
Variable Interest Entity
Variable Interest Entity [Line Items]
Other noninterest income									1	(5)	(1)
Provision for income taxes, amortization of LIHTC investments									62	60	56
Provision for income taxes									(21)	(27)	(21)
Low income housing tax credits | Variable Interest Entity
Variable Interest Entity [Line Items]
Provision for income taxes, affordable housing tax credits and other tax benefits									(61)	(59)	(56)
Other tax benefits related to tax credit entities | Variable Interest Entity
Variable Interest Entity [Line Items]
Provision for income taxes, affordable housing tax credits and other tax benefits									$ (22)	$ (28)	$ (21)

Deposits Deposits (Schedule o98

Deposits Deposits (Schedule of Maturities of Domestic Deposits of One Hundred Thousand or More) (Details) - Domestic Certificates of Deposit and Other Deposits [Member] - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Three Months or Less	$ 532	$ 822
Over three months to six months	385	456
Over six months to twelve months	659	733
Over twelve months	537	795
Total	$ 2,113	$ 2,806

Short-term Borrowings Short-t99

Short-term Borrowings Short-term Borrowings (Narrative) (Details) $ in Billions	Dec. 31, 2015USD ($)
Short-term Debt [Abstract]
Pledged loans to provide collateralized borrowing with the FRB	$ 24
Available collateralized borrowing with the FRB	$ 18

Short-term Borrowings Short-100

Short-term Borrowings Short-term Borrowings (Summary of Short-term Borrowings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Short-term Debt [Line Items]
Amount outstanding at year-end	$ 23	$ 116
Federal Funds Purchased and Securities Sold Under Agreements to Repurchase
Short-term Debt [Line Items]
Amount outstanding at year-end	$ 23	$ 116	$ 253
Weighted average interest rate at year-end	0.38%	0.04%	0.05%
Maximum month-end balance during the year	$ 109	$ 238	$ 277
Average balance outstanding during the year	$ 93	$ 200	$ 211
Weighted average interest rate during the year	0.05%	0.04%	0.07%

Medium- And Long-Term Debt (Nar

Medium- And Long-Term Debt (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
Unamortized debt issuance costs	$ 8
Blanket lien on real-estate related loans securing FHLB advances	14,000
FHLB potential future borrowings	6,000
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in medium- and long-term debt due to early adoption of ASU 2015-03	3,058	$ 2,675
Decrease in other assets due to early adoption of ASU 2015-03	$ 4,117	4,434
Restatement Adjustment | Effect of Early Adoption of ASU 2015-03
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in medium- and long-term debt due to early adoption of ASU 2015-03		4
Decrease in other assets due to early adoption of ASU 2015-03		$ 4

Medium- And Long-Term Debt (Sch

Medium- And Long-Term Debt (Schedule Of Medium- And Long-Term Debt) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Debt Instruments [Line Items]
Total medium- and long-term debt		$ 3,058	$ 2,675
Parent Company
Debt Instruments [Line Items]
Total medium- and long-term debt		608	1,208
Subsidiaries
Debt Instruments [Line Items]
Subordinated notes		1,763	1,445
Total medium- and long-term debt		2,450	1,467
4.80% subordinated notes due 2015 | Parent Company
Debt Instruments [Line Items]
Subordinated notes	[1]	$ 0	$ 304
Stated interest rate		4.80%	4.80%
Maturity date		May 1, 2015	May 1, 2015
3.80% subordinated notes due 2026 | Parent Company
Debt Instruments [Line Items]
Subordinated notes	[1]	$ 259	$ 257
Stated interest rate		3.80%	3.80%
Maturity date		Jul. 22, 2026	Jul. 22, 2026
3.00% notes due 2015 | Parent Company
Debt Instruments [Line Items]
Medium-term notes		$ 0	$ 300
Stated interest rate		3.00%	3.00%
Maturity date		Sep. 16, 2015	Sep. 16, 2015
2.125% notes due 2019 | Parent Company
Debt Instruments [Line Items]
Medium-term notes	[1]	$ 349	$ 347
Stated interest rate		2.125%	2.125%
Maturity date		May 23, 2019	May 23, 2019
5.75% subordinated notes due 2016 | Subsidiaries
Debt Instruments [Line Items]
Subordinated notes	[1],[2]	$ 659	$ 670
Stated interest rate		5.75%	5.75%
Maturity date		Nov. 21, 2016	Nov. 21, 2016
Par value swapped to variable rate		$ 250
Total par value outstanding		600
5.20% subordinated notes due 2017 | Subsidiaries
Debt Instruments [Line Items]
Subordinated notes	[1]	$ 530	$ 548
Stated interest rate		5.20%	5.20%
Maturity date		Aug. 22, 2017	Aug. 22, 2017
4.00% subordinated notes due 2025 | Subsidiaries
Debt Instruments [Line Items]
Subordinated notes	[1]	$ 351	$ 0
Stated interest rate		4.00%
Maturity date		Jul. 27, 2025
7.875% subordinated notes due 2026 | Subsidiaries
Debt Instruments [Line Items]
Subordinated notes	[1]	$ 223	$ 227
Stated interest rate		7.875%	7.875%
Maturity date		Sep. 15, 2026	Sep. 15, 2026
2.50% notes due 2020 | Subsidiaries
Debt Instruments [Line Items]
Medium-term notes	[1]	$ 671	$ 0
Stated interest rate		2.50%
Maturity date		Jun. 2, 2020
6.0% - 6.4% fixed-rate notes due 2015 to 2020 | Subsidiaries
Debt Instruments [Line Items]
Other notes		$ 16	$ 22
Fixed interest rate - minimum		6.00%	6.00%
Fixed interest rate - maximum		6.40%	6.40%
Earliest maturity date		Jun. 30, 2016	Jun. 30, 2015
Latest maturity date		Jun. 30, 2020	Jun. 30, 2020
[1]	The fixed interest rates on these notes have been swapped to a variable rate and designated in a hedging relationship. Accordingly, carrying value has been adjusted to reflect the change in the fair value of the debt as a result of changes in the benchmark rate.
[2]	The fixed interest rate on $250 million of $600 million total par value of these notes have been swapped to a variable rate.Subordinated notes with remaining maturities greater than one year qualify as Tier 2 capital.

Medium- And Long-Term Debt Sche

Medium- And Long-Term Debt Schedule of Maturities of Medium- and Long-term Debt (Details) $ in Millions	Dec. 31, 2015USD ($)
Debt Disclosure [Abstract]
2,016	$ 650
2,017	500
2,018	2
2,019	357
2,020	682
Thereafter	750
Total	$ 2,941

Shareholders' Equity Shareholde

Shareholders' Equity Shareholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity Repurchases Authorized per Capital Plan	$ 393
Equity Repurchases per Capital Plan	$ 242
Stock Option
Common stock shares reserved for future issuance	12,700
Restricted Stock
Shares of non-vested restricted stock outstanding	1,910	2,140
Common Stock
Shares repurchased under equity repurchase program	5,300	5,400	7,500
Warrants
Number of warrants to purchase common stock outstanding	9,500
Number of shares of common stock issuable under outstanding warrants	8,500
Average exercise price for outstanding warrants	$ 29.43
Year of expiration for outstanding warrants	2,018
Shares of common stock issued upon exercise of warrants	934	361	0
Common stock shares reserved for future issuance	8,500
Equity Repurchase Program | Common Stock
Shares repurchased under equity repurchase program	5,100	5,200	7,400
Average cost per share of shares repurchased under equity repurchase program	$ 45.65	$ 47.91	$ 38.63
Equity Repurchase Program | Warrants
Warrants repurchased under equity repurchase program	500
Average cost per warrant repurchased under the equity repurchase program	$ 20.70

Accumulated Other Comprehens105

Accumulated Other Comprehensive Income (Loss) (Schedule Of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Investment securities, Balance at beginning of period, net of tax	$ 37	$ (68)	$ 150
Investment securities, Net unrealized holding (losses) gains arising during the period	(55)	166	(343)
Investment securities, Less: (Benefit) provision for income taxes	(21)	60	(126)
Investment securities, Net unrealized holding (losses) gains arising during period, net of tax	(34)	106	(217)
Investment securities, Net realized (losses) gains included in net securities gains	(2)	1	1
Investment securities, Less: Benefit for income taxes	(1)	0	0
Investment securities, Reclassification adjustment for net securities (losses) gains included in net income, net of tax	(1)	1	1
Investment securities, Net losses realized as a yield adjustment in interest on investment securities	(8)	0	0
Investment securities, Less: Benefit for income taxes	(3)	0	0
Investment securities, Reclassification adjustment for net losses realized as a yield adjustment included in net income, net of tax	(5)	0	0
Investment securities, Change in net unrealized (losses) gains on investment securities available-for-sale, net of tax	(28)	105	(218)
Investment securities, Balance at end of period, net of tax	9	37	(68)
Benefit plans, Balance at beginning of period, net of tax	(449)	(323)	(563)
Benefit plans, Actuarial (loss) gain arising during the period	(57)	(240)	286
Benefit plans, Prior service credit arising during the period	3	0	0
Benefit plans, Net defined benefit pension and other postretirement adjustment arising during the period	(54)	(240)	286
Benefit plans, Less: (Benefit) provision for income taxes	(19)	(87)	103
Benefit plans, Net defined benefit pension and other postretirement adjustment arising during the period, net of tax	(35)	(153)	183
Benefit plans, Amortization of actuarial net loss	70	39	89
Benefit plans, Amortization of prior service cost	1	3	2
Benefit plans, Total amounts recognized in employee benefits expense	71	42	91
Benefit plans, Less: Benefit for income taxes	25	15	34
Benefit plans, Adjustment for amounts recognized as components of net periodic benefit cost during the period, net of tax	46	27	57
Benefit plans, Change in defined benefit pension and other postretirement plans adjustment, net of tax	11	(126)	240
Benefit plans, Balance at end of period, net of tax	(438)	(449)	(323)
Total accumulated other comprehensive loss at end of period, net of tax	$ (429)	$ (412)	$ (391)

Share-Based Compensation Sha106

Share-Based Compensation Share-Based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of shares originally available for grant	19,400,000
Shares available for grant	9,800,000
Total intrinsic value of stock options exercised	$ 12	$ 23	$ 14
Shares in treasury	52,457,113	49,146,225
Restricted Stock
Total fair value of restricted stock awards that fully vested	$ 18	$ 18	$ 10
Restricted Stock | Minimum
Share-based compensation vesting period	3 years
Restricted Stock | Maximum
Share-based compensation vesting period	5 years
Restricted Stock Units (RSUs) | Minimum
Share-based compensation vesting period	1 year
Restricted Stock Units (RSUs) | Maximum
Share-based compensation vesting period	3 years
Stock Options | Minimum
Share-based compensation vesting period	1 year
Stock Options | Maximum
Share-based compensation vesting period	4 years
Comerica Incorporated
Closing stock price per share	$ 41.83

Share-Based Compensation (Summa

Share-Based Compensation (Summary of Components of Share-Based Compensation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation [Abstract]
Total share-based compensation expense	$ 38	$ 38	$ 35
Related tax benefits recognized in net income	$ 14	$ 14	$ 13

Share-Based Compensation (Unrec

Share-Based Compensation (Unrecognized Compensation Expense) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Share-based Compensation [Abstract]
Total unrecognized share-based compensation expense	$ 49
Weighted-average expected recognition period (in years)	2 years 9 months 2 days

Share-Based Compensation (Estim

Share-Based Compensation (Estimated Weighted-Average Grant-Date Fair Value Per Option Share and the Underlying Binomial Option-Pricing Model Assumptions) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation [Abstract]
Weighted-average grant-date fair value per option	$ 11.31	$ 13.21	$ 9.07
Risk-free interest rates	1.83%	2.95%	1.94%
Expected dividend yield	3.00%	3.00%	3.00%
Expected volatility factors of the market price of Comerica common stock	33.00%	31.00%	34.00%
Expected option life (in years)	6 years 10 months 24 days	5 years 9 months 18 days	6 years 4 months 24 days

Share-Based Compensation (Su110

Share-Based Compensation (Summary of the Corporation's Stock Option Activity and Related Information) (Details) - Stock Options $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)$ / sharesshares
Number of options outstanding at January 1, 2015 | shares	14,003
Options granted | shares	1,035
Options forfeited or expired | shares	(2,405)
Options exercised | shares	(841)
Number of options outstanding at December 31, 2015 | shares	11,792
Number of options outstanding net of expected forfeitures at December 31, 2015 | shares	11,520
Number of options exercisable at December 31, 2015 | shares	9,146
Options outstanding at January 1, 2015 (Weighted-average exercise price) | $ / shares	$ 44.28
Options granted (Weighted-average exercise price) | $ / shares	42.32
Options forfeited or expired (Weighted-average exercise price) | $ / shares	53.88
Options exercised (Weighted-average exercise price) | $ / shares	33.46
Options outstanding at December 31, 2015 (Weighted-average exercise price) | $ / shares	42.92
Options outstanding, net of expected forfeitures, at December 31, 2015 (Weighted-average exercise price) | $ / shares	43.04
Options exercisable at December 31, 2015 (Weighted-average exercise price) | $ / shares	$ 43.70
Weighted-average remaining contractual term in years at December 31, 2015	4 years 1 month 5 days
Weighted-average remaining contractual term in years net of expected forfeitures at December 31, 2015	4 years
Weighted-average remaining contractual term in years exercisable at December 31, 2015	3 years
Aggregate intrinsic value outstanding at December 31, 2015 | $	$ 53
Aggregate intrinsic value outstanding, net of expected forfeitures at December 31, 2015 | $	52
Aggregate intrinsic value exercisable at December 31, 2015 | $	$ 43

Share-Based Compensation (Su111

Share-Based Compensation (Summary of the Corporation's Restricted Stock Activity and Related Information) (Details) - Restricted Stock shares in Thousands	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Non-vested shares outstanding at January 1, 2015 | shares	2,140
Non-vested shares granted | shares	413
Non-vested shares forfeited | shares	(106)
Shares vested | shares	(537)
Non-vested shares outstanding at December 31, 2015 | shares	1,910
Non-vested shares outstanding at January 1, 2015 (Weighted-average grant-date fair value) | $ / shares	$ 35.38
Non-vested shares granted (Weighted-average grant-date fair value) | $ / shares	42.45
Non-vested shares forfeited (Weighted-average grant-date fair value) | $ / shares	37.02
Shares vested (Weighted-average grant-date fair value) | $ / shares	33.29
Non-vested shares outstanding at December 31, 2015 (Weighted-average grant-date fair value) | $ / shares	$ 37.41

Share-Based Compensation Summar

Share-Based Compensation Summary of the Corporation's Restricted Stock Unit Activity and Related Information (Details) - Restricted Stock Units (RSUs) shares in Thousands	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Service-Based Units
Non-vested shares outstanding at January 1, 2015 | shares	387
Non-vested shares granted | shares	18
Non-vested shares converted | shares	41
Non-vested shares forfeited | shares	(33)
Non-vested shares outstanding at December 31, 2015 | shares	413
Non-vested shares outstanding at January 1, 2015 (Weighted-average grant-date fair value) | $ / shares	$ 34.58
Non-vested shares granted (Weighted-average grant-date fair value) | $ / shares	46.83
Non-vested shares converted (Weighted-average grant-date fair value) | $ / shares	33.79
Non-vested shares forfeited (Weighted-average grant-date fair value) | $ / shares	37.78
Non-vested shares outstanding at December 31, 2015 (Weighted-average grant-date fair value) | $ / shares	$ 34.77
Performance-Based Units
Non-vested shares outstanding at January 1, 2015 | shares	319
Non-vested shares granted | shares	266
Non-vested shares converted | shares	(41)
Non-vested shares forfeited | shares	(34)
Non-vested shares outstanding at December 31, 2015 | shares	510
Non-vested shares outstanding at January 1, 2015 (Weighted-average grant-date fair value) | $ / shares	$ 45.44
Non-vested shares granted (Weighted-average grant-date fair value) | $ / shares	42.32
Non-vested shares converted (Weighted-average grant-date fair value) | $ / shares	33.79
Non-vested shares forfeited (Weighted-average grant-date fair value) | $ / shares	43.27
Non-vested shares outstanding at December 31, 2015 (Weighted-average grant-date fair value) | $ / shares	$ 44.89

Employee Benefit Plans (Narrati

Employee Benefit Plans (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit pension expense	$ 47,000,000	$ 39,000,000	$ 86,000,000
Postretirement benefit expense	48,000,000	40,000,000	88,000,000
Fair value of plan assets in defined benefit pension plan	2,347,000,000	2,531,000,000
Estimated employer contributions for defined benefit plans in year 2016	$ 0
Employer core matching cash contribution as percent of employee contribution	100.00%
Percent of qualified earnings contributed by employee matched by the Corporation	4.00%
Defined contribution plan expense	$ 22,000,000	22,000,000	21,000,000
Profit sharing plan annual contribution to the individual account of each eligible employee, minimum percent of annual compensation	3.00%
Profit sharing plan annual contribution to the individual account of each eligible employee, maximum percent of annual compensation	8.00%
Profit sharing plan expense included in employee benefits expense	$ 10,000,000	10,000,000	7,000,000
Qualified Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Postretirement benefit expense	$ 27,000,000	23,000,000	68,000,000
Estimated average life of pension plan in years	15
Fair value of plan assets in defined benefit pension plan	$ 2,346,000,000	2,541,000,000	2,035,000,000
Qualified Plan | Equity securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation, minimum percent	36.00%
Target allocation, maximum percent	56.00%
Qualified Plan | Debt securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation, minimum percent	44.00%
Target allocation, maximum percent	64.00%
Non-Qualified Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Postretirement benefit expense	$ 20,000,000	16,000,000	18,000,000
Fair value of plan assets in defined benefit pension plan	0	0
Postretirement Benefit Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Postretirement benefit expense	1,000,000	1,000,000	2,000,000
Fair value of plan assets in defined benefit pension plan	$ 61,000,000	$ 67,000,000	$ 67,000,000

Employee Benefit Plans (Reconci

Employee Benefit Plans (Reconciliations of Plan assets and the Projected Benefit Obligation, the Weighted-Average Assumptions Used to Determine Year-End Benefit Obligations, and the Amounts Recognized in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair value of plan assets at January 1		$ 2,531,000,000
Fair value of plan assets at December 31		2,347,000,000	$ 2,531,000,000
Qualified Plan
Fair value of plan assets at January 1		2,541,000,000	2,035,000,000
Actual return on plan assets		(73,000,000)	278,000,000	$ 136,000,000
Employer contributions		0	350,000,000
Benefits paid	[1]	(122,000,000)	(122,000,000)
Fair value of plan assets at December 31		2,346,000,000	2,541,000,000	2,035,000,000
Projected benefit obligation at January 1		2,070,000,000	1,731,000,000
Service cost		35,000,000	29,000,000	37,000,000
Interest cost		88,000,000	88,000,000	80,000,000
Actuarial (gain) loss		(155,000,000)	344,000,000
Plan amendment		0	0
Projected benefit obligation at December 31		1,916,000,000	2,070,000,000	1,731,000,000
Accumulated benefit obligation		1,756,000,000	1,905,000,000
Funded Status at December 31	[2],[3]	$ 430,000,000	$ 471,000,000
Weighted-average assumptions, discount rate, percent		4.82%	4.28%
Weighted-average assumptions, rate of compensation increase, percent		3.75%	3.75%
Accumulated other comprehensive income (loss), net actuarial loss		$ (586,000,000)	$ (568,000,000)
Accumulated other comprehensive income (loss), net prior service (cost) credit		(21,000,000)	(25,000,000)
Balance at December 31		(607,000,000)	(593,000,000)
Lump sum settlements included in benefits paid		56,000,000	63,000,000
Non-Qualified Plan
Fair value of plan assets at January 1		0
Benefits paid		(11,000,000)	(10,000,000)
Fair value of plan assets at December 31		0	0
Projected benefit obligation at January 1		235,000,000	195,000,000
Service cost		4,000,000	3,000,000	4,000,000
Interest cost		10,000,000	10,000,000	9,000,000
Actuarial (gain) loss		(16,000,000)	37,000,000
Plan amendment		0	0
Projected benefit obligation at December 31		222,000,000	235,000,000	195,000,000
Accumulated benefit obligation		191,000,000	203,000,000
Funded Status at December 31	[2],[3]	$ (222,000,000)	$ (235,000,000)
Weighted-average assumptions, discount rate, percent		4.82%	4.28%
Weighted-average assumptions, rate of compensation increase, percent		3.75%	3.75%
Accumulated other comprehensive income (loss), net actuarial loss		$ (78,000,000)	$ (104,000,000)
Accumulated other comprehensive income (loss), net prior service (cost) credit		21,000,000	25,000,000
Balance at December 31		(57,000,000)	(79,000,000)
Postretirement Benefit Plan
Fair value of plan assets at January 1		67,000,000	67,000,000
Actual return on plan assets		0	3,000,000	(2,000,000)
Employer contributions		0	2,000,000
Benefits paid		(6,000,000)	(5,000,000)
Fair value of plan assets at December 31		61,000,000	67,000,000	67,000,000
Projected benefit obligation at January 1		73,000,000	69,000,000
Service cost		0	0
Interest cost		3,000,000	3,000,000	3,000,000
Actuarial (gain) loss		(8,000,000)	6,000,000
Plan amendment		(3,000,000)	0
Projected benefit obligation at December 31		59,000,000	73,000,000	$ 69,000,000
Accumulated benefit obligation		59,000,000	73,000,000
Funded Status at December 31	[2],[3]	$ 2,000,000	$ (6,000,000)
Weighted-average assumptions, discount rate, percent		4.53%	3.99%
Healthcare cost trend rate assumed for next year		7.00%	7.00%
Rate to which the healthcare cost trend rate is assumed to decline (the ultimate trend rate), percent		5.00%	5.00%	5.00%
Year when healthcare cost trend rate reaches the ultimate trend rate		2,027	2,026
Accumulated other comprehensive income (loss), net actuarial loss		$ (22,000,000)	$ (27,000,000)
Accumulated other comprehensive income (loss), net prior service (cost) credit		1,000,000	(3,000,000)
Balance at December 31		$ (21,000,000)	$ (30,000,000)
[1]	Included $56 million and $63 million in benefit payments made to certain terminated vested eligible participants who elected to receive lump-sum settlements in 2015 and 2014, respectively.
[2]	Based on projected benefit obligation for defined benefit pension plans and accumulated benefit obligation for postretirement benefit plan.
[3]	The Corporation recognizes the overfunded and underfunded status of the plans in “accrued income and other assets” and “accrued expenses and other liabilities,” respectively, on the consolidated balance sheets.

Employee Benefit Plans (Schedul

Employee Benefit Plans (Schedule of Changes, Net of Tax, in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Actuarial (loss) gain arising during the period	$ (57)	$ (240)	$ 286
Prior service credit arising during the period	3	0	0
Amortization of actuarial net loss	70	39	89
Amortization of prior service cost (credit)	1	3	2
Total recognized in other comprehensive income (loss)	17	$ (198)	$ 377
Qualified Plan
Actuarial (loss) gain arising during the period	(77)
Prior service credit arising during the period	0
Amortization of actuarial net loss	59
Amortization of prior service cost (credit)	4
Total recognized in other comprehensive income (loss)	(14)
Non-Qualified Plan
Actuarial (loss) gain arising during the period	16
Prior service credit arising during the period	0
Amortization of actuarial net loss	10
Amortization of prior service cost (credit)	(4)
Total recognized in other comprehensive income (loss)	22
Postretirement Benefit Plan
Actuarial (loss) gain arising during the period	4
Prior service credit arising during the period	3
Amortization of actuarial net loss	1
Amortization of prior service cost (credit)	1
Total recognized in other comprehensive income (loss)	$ 9

Employee Benefit Plans Employee

Employee Benefit Plans Employee Benefit Plans (Net Periodic Defined Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Net periodic defined benefit cost	$ 48	$ 40	$ 88
Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	35	29	37
Interest cost	88	88	80
Expected return on plan assets	(159)	(131)	(132)
Amortization of prior service cost (credit)	4	6	7
Amortization of net loss	59	31	76
Net periodic defined benefit cost	27	23	68
Actual return on plan assets	$ (73)	$ 278	$ 136
Actual rate of return on plan assets, percent	(2.95%)	13.88%	7.05%
Weighted-average assumptions, discount rate, percent	4.28%	5.17%	4.20%
Weighted-average assumptions, expected long-term return on plan assets, percent	6.75%	6.75%	7.25%
Weighted-average assumptions, rate of compensation increase, percent	3.75%	4.00%	4.00%
Non-Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4	$ 3	$ 4
Interest cost	10	10	9
Expected return on plan assets	0	0	0
Amortization of prior service cost (credit)	(4)	(4)	(6)
Amortization of net loss	10	7	11
Net periodic defined benefit cost	$ 20	$ 16	$ 18
Weighted-average assumptions, discount rate, percent	4.28%	5.17%	4.20%
Weighted-average assumptions, rate of compensation increase, percent	3.75%	4.00%	4.00%
Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0
Interest cost	3	3	$ 3
Expected return on plan assets	(4)	(4)	(4)
Amortization of prior service cost (credit)	1	1	1
Amortization of net loss	1	1	2
Net periodic defined benefit cost	1	1	2
Actual return on plan assets	$ 0	$ 3	$ (2)
Actual rate of return on plan assets, percent	(0.53%)	4.62%	(2.29%)
Weighted-average assumptions, discount rate, percent	3.99%	4.59%	3.81%
Weighted-average assumptions, expected long-term return on plan assets, percent	5.00%	5.00%	5.00%
Health care cost trend rate assumed	7.00%	7.50%	8.00%
Rate to which the healthcare cost trend rate is assumed to decline (the ultimate trend rate), percent	5.00%	5.00%	5.00%
Defined Benefit Plan Year That Reaches Ultimate Trend Rate In Current Expense	2,026	2,033	2,033

Employee Benefit Plans (The Est

Employee Benefit Plans (The Estimated Portion of Balances Remaining in Accumulated Other Comprehensive Income (Loss) that are Expected to be Recognized as a Component of Net Periodic Benefit Cost) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Net loss	$ 38
Prior service cost (credit)	0
Qualified Plan
Net loss	30
Prior service cost (credit)	4
Non-Qualified Plan
Net loss	7
Prior service cost (credit)	(4)
Postretirement Benefit Plan
Net loss	1
Prior service cost (credit)	$ 0

Employee Benefit Plans (Effect

Employee Benefit Plans (Effect of One-Percentage-Point Change in 2014 Assumed Healthcare and Prescription Drug Cost Trend Rates) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Effect on postretirement benefit obligation, Increase	$ 4
Effect on postretirement benefit obligation, Decrease	(3)
Effect on total service and interest cost, Increase	0
Effect on total service and interest cost, Decrease	$ 0

Employee Benefit Plans (Fair Va

Employee Benefit Plans (Fair Values of the Corporation's Qualified Defined Benefit Pension Plan Investments Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair value of plan assets in qualified defined benefit pension plan	$ 2,347	$ 2,531
Cash equivalent securities, mutual funds
Fair value of plan assets in qualified defined benefit pension plan	43	390
Equity securities | Collective investments funds
Fair value of plan assets in qualified defined benefit pension plan	527	466
Equity securities | Mutual funds
Fair value of plan assets in qualified defined benefit pension plan	69	76
Equity securities | Common stock
Fair value of plan assets in qualified defined benefit pension plan	480	499
Debt securities | U.S. Treasury and other U.S. government agency securities
Fair value of plan assets in qualified defined benefit pension plan	356	359
Debt securities | Corporate and municipal bonds and notes
Fair value of plan assets in qualified defined benefit pension plan	729	659
Debt securities | Collateralized mortgage obligations
Fair value of plan assets in qualified defined benefit pension plan	18	9
Debt securities | U.S. government agency mortgage-backed securities
Fair value of plan assets in qualified defined benefit pension plan	8
Debt securities | TBA mortgage-backed securities
Fair value of plan assets in qualified defined benefit pension plan	12
Private placements
Fair value of plan assets in qualified defined benefit pension plan	105	73
Level 1
Fair value of plan assets in qualified defined benefit pension plan	946	1,324
Level 1 | Cash equivalent securities, mutual funds
Fair value of plan assets in qualified defined benefit pension plan	43	390
Level 1 | Equity securities | Collective investments funds
Fair value of plan assets in qualified defined benefit pension plan	0	0
Level 1 | Equity securities | Mutual funds
Fair value of plan assets in qualified defined benefit pension plan	69	76
Level 1 | Equity securities | Common stock
Fair value of plan assets in qualified defined benefit pension plan	478	499
Level 1 | Debt securities | U.S. Treasury and other U.S. government agency securities
Fair value of plan assets in qualified defined benefit pension plan	356	359
Level 1 | Debt securities | Corporate and municipal bonds and notes
Fair value of plan assets in qualified defined benefit pension plan	0	0
Level 1 | Debt securities | Collateralized mortgage obligations
Fair value of plan assets in qualified defined benefit pension plan	0	$ 0
Level 1 | Debt securities | U.S. government agency mortgage-backed securities
Fair value of plan assets in qualified defined benefit pension plan	0
Level 1 | Debt securities | TBA mortgage-backed securities
Fair value of plan assets in qualified defined benefit pension plan	0
Level 1 | Private placements
Fair value of plan assets in qualified defined benefit pension plan	0
Level 2
Fair value of plan assets in qualified defined benefit pension plan	1,296	$ 1,134
Level 2 | Cash equivalent securities, mutual funds
Fair value of plan assets in qualified defined benefit pension plan	0	0
Level 2 | Equity securities | Collective investments funds
Fair value of plan assets in qualified defined benefit pension plan	527	466
Level 2 | Equity securities | Mutual funds
Fair value of plan assets in qualified defined benefit pension plan	0	0
Level 2 | Equity securities | Common stock
Fair value of plan assets in qualified defined benefit pension plan	2	0
Level 2 | Debt securities | U.S. Treasury and other U.S. government agency securities
Fair value of plan assets in qualified defined benefit pension plan	0	0
Level 2 | Debt securities | Corporate and municipal bonds and notes
Fair value of plan assets in qualified defined benefit pension plan	729	659
Level 2 | Debt securities | Collateralized mortgage obligations
Fair value of plan assets in qualified defined benefit pension plan	18	9
Level 2 | Debt securities | U.S. government agency mortgage-backed securities
Fair value of plan assets in qualified defined benefit pension plan	8
Level 2 | Debt securities | TBA mortgage-backed securities
Fair value of plan assets in qualified defined benefit pension plan	12
Level 2 | Private placements
Fair value of plan assets in qualified defined benefit pension plan	0	0
Level 3
Fair value of plan assets in qualified defined benefit pension plan	105	73
Level 3 | Cash equivalent securities, mutual funds
Fair value of plan assets in qualified defined benefit pension plan	0	0
Level 3 | Equity securities | Collective investments funds
Fair value of plan assets in qualified defined benefit pension plan	0	0
Level 3 | Equity securities | Mutual funds
Fair value of plan assets in qualified defined benefit pension plan	0	0
Level 3 | Equity securities | Common stock
Fair value of plan assets in qualified defined benefit pension plan	0	0
Level 3 | Debt securities | U.S. Treasury and other U.S. government agency securities
Fair value of plan assets in qualified defined benefit pension plan	0	0
Level 3 | Debt securities | Corporate and municipal bonds and notes
Fair value of plan assets in qualified defined benefit pension plan	0	0
Level 3 | Debt securities | Collateralized mortgage obligations
Fair value of plan assets in qualified defined benefit pension plan	0	0
Level 3 | Debt securities | U.S. government agency mortgage-backed securities
Fair value of plan assets in qualified defined benefit pension plan	0
Level 3 | Debt securities | TBA mortgage-backed securities
Fair value of plan assets in qualified defined benefit pension plan	0
Level 3 | Private placements
Fair value of plan assets in qualified defined benefit pension plan	$ 105	$ 73

Employee Benefit Plans (Summary

Employee Benefit Plans (Summary of Changes in the Corporation's Qualified Defined Benefit Pension Plan's Level 3 Investments Measured at Fair Value on a Recurring Basis) (Details) - Private placements - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Balance at beginning of period	$ 73	$ 36
Gains (Losses) Realized	0	1
Gains (Losses) Unrealized	(5)	4
Purchases	108	60
Sales	(71)	(28)
Balance at end of period	$ 105	$ 73

Employee Benefit Plans (Sche121

Employee Benefit Plans (Schedule of Estimated Future Employer Contributions) (Details) $ in Millions	Dec. 31, 2015USD ($)
Qualified Plan
2,016	$ 72
2,017	77
2,018	83
2,019	89
2,020	94
2021 - 2025	550
Non-Qualified Plan
2,016	11
2,017	12
2,018	12
2,019	13
2,020	13
2021 - 2025	70
Postretirement Benefit Plan
2,016	6	[1]
2,017	6	[1]
2,018	6	[1]
2,019	6	[1]
2,020	6	[1]
2021 - 2025	$ 24	[1]
[1]	Estimated benefit payments in the postretirement benefit plan are net of estimated Medicare subsidies.

Income Taxes And Tax-Related122

Income Taxes And Tax-Related Items Income Taxes And Tax-Related Items (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income before income taxes									$ 750	$ 870	$ 786
Foreign-source income									34
Provision for income taxes	$ 41	$ 63	$ 64	$ 61	$ 70	$ 73	$ 70	$ 64	229	277	245
Decrease in shareholders' equity and deferred tax assets due to income tax effect of transactions under share-based compensation plans									12	11	5
Liability for tax-related interest and penalties	3				2				3	2
Reasonably possible change in unrecognized tax benefits in next 12 months	8								8
Unrecognized tax benefits that would impact the effective tax rate	4				2				4	2
State net operating loss carryforwards	5								5
Deferred tax asset valuation allowance	$ 3				$ 0				3	0
Available-for-sale Securities
Provision for income taxes									$ (1)	$ 0	$ 0
Minimum
Years state net operating loss carryforwards expire									Dec. 31, 2016
Maximum
Years state net operating loss carryforwards expire									Dec. 31, 2026

Income Taxes And Tax-Related123

Income Taxes And Tax-Related Items Current and Deferred Components of the Provision for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Current federal income tax									$ 275	$ 127	$ 242
Current foreign income tax									5	6	6
Current state and local income tax									20	14	17
Total current income tax									300	147	265
Deferred federal income tax									(68)	123	(20)
Deferred state and local income tax									(3)	7	0
Total deferred income tax									(71)	130	(20)
Provision for income taxes	$ 41	$ 63	$ 64	$ 61	$ 70	$ 73	$ 70	$ 64	$ 229	$ 277	$ 245

Income Taxes And Tax-Related124

Income Taxes And Tax-Related Items Reconciliation of Expected Income Tax Expense at the Federal Statutory Rate to the Corporation's Provision for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Tax based on federal statutory rate, amount									$ 262	$ 305	$ 275
Tax based on federal statutory rate, percent									35.00%	35.00%	35.00%
State income tax, amount									$ 10	$ 13	$ 11
State income tax, percent									1.30%	1.50%	1.40%
Affordable housing and historic credits, amount									$ (22)	$ (24)	$ (21)
Affordable housing and historic credits, percent									(2.90%)	(2.80%)	(2.60%)
Bank-owned life insurance, amount									$ (15)	$ (15)	$ (15)
Bank-owned life insurance, percent									(2.00%)	(1.70%)	(1.90%)
Other changes in unrecognized tax benefits, amount									$ 0	$ 2	$ (2)
Other changes in unrecognized tax benefits, percent									0.00%	0.20%	(0.20%)
Lease termination transactions, amount									$ (5)	$ 0	$ 0
lease termination transactions, percent									(0.70%)	0.00%	0.00%
Tax-related interest and penalties, amount									$ 1	$ (3)	$ (1)
Tax-related interest and penalties, percent									0.10%	(0.30%)	(0.10%)
Other, amount									$ (2)	$ (1)	$ (2)
Other, percent									(0.30%)	(0.10%)	(0.40%)
Provision for income taxes, amount	$ 41	$ 63	$ 64	$ 61	$ 70	$ 73	$ 70	$ 64	$ 229	$ 277	$ 245
Provision for income taxes, percent									30.50%	31.80%	31.20%

Income Taxes And Tax-Related125

Income Taxes And Tax-Related Items Reconciliation of the Beginning and Ending Amounts of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Balance at January 1	$ 14	$ 11	$ 42
Increases as a result of tax positions taken during a prior period	8	3	0
Decrease related to settlements with tax authorities	0	0	(31)
Balance at December 31	$ 22	$ 14	$ 11

Income Taxes And Tax-Related126

Income Taxes And Tax-Related Items Tax Years for Significant Jurisdictions That Remain Subject to Examination (Details)	12 Months Ended
	Dec. 31, 2015
Federal | Minimum
Open Tax Year	2,010
Federal | Maximum
Open Tax Year	2,014
California | Minimum
Open Tax Year	2,003
California | Maximum
Open Tax Year	2,014

Income Taxes And Tax-Related127

Income Taxes And Tax-Related Items Principal Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Allowance for loan losses	$ 223	$ 208
Deferred compensation	113	123
Loan purchase accounting adjustments	2	5
Deferred loan origination fees and costs	24	28
Other temporary differences, net	67	44
Total deferred tax asset before valuation allowance	429	408
Valuation allowance	(3)	0
Total deferred tax assets	426	408
Deferred tax liabilities:
Lease financing transactions	(183)	(206)
Defined benefit plans	(32)	(38)
Net unrealized gains on investment securities available-for-sale	(5)	(21)
Allowance for depreciation	(7)	(13)
Total deferred tax liabilities	(227)	(278)
Net deferred tax asset	$ 199	$ 130

Transactions with Related Pa128

Transactions with Related Parties Transactions with Related Parties (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Related Party Transactions [Abstract]
Loans attributed to persons who were related parties at beginning of period	$ 79
New loans to related parties	453
Repayments on loans to related parties	411
Loans attributed to persons who were related parties at end of period	$ 121

Regulatory Capital and Reser129

Regulatory Capital and Reserve Requirements Regulatory Capital and Reserve Requirements (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Federal Reserve Bank average reserve requirement	$ 473	$ 430
Dividends available to be paid to parent company without obtaining prior approval from bank regulatory agencies	398
Dividends from bank subsidiaries	$ 437	$ 380	$ 480
Total risk-based capital minimum to be well capitalized	10.00%	10.00%
Tier 1 risk-based capital minimum to be well capitalized	6.00%	6.00%
U.S. Banking Subsidiaries
Total risk-based capital minimum to be well capitalized	10.00%	10.00%
Tier 1 risk-based capital minimum to be well capitalized	8.00%	6.00%
Common equity tier 1 risk-based capital minimum to be well capitalized	6.50%
Leverage ratio minimum to be well capitalized	5.00%	5.00%

Regulatory Capital and Reser130

Regulatory Capital and Reserve Requirements Regulatory Capital and Reserve Requirements (Summary of Capital Position) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Comerica Incorporated
Summary of Capital Position [Line Items]
CET 1 capital	$ 7,350
Tier 1 capital	7,350	$ 7,169
Total capital	8,852	8,543
Risk-weighted assets	69,731	68,273
Average assets (fourth quarter)	$ 71,943	$ 69,284
CET 1 capital to risk-weighted assets	10.54%
Tier 1 capital to risk-weighted assets	10.54%	10.50%
Total capital to risk-weighted assets	12.69%	12.51%
Tier 1 capital to average assets	10.22%	10.35%
CET 1 capital - minimum (Consolidated)	$ 3,100
Tier 1 capital - minimum (Consolidated)	4,200	$ 2,700
Total capital - minimum (Consolidated)	$ 5,600	$ 5,500
CET 1 capital to risk-weighted assets - minimum	4.50%
Tier 1 capital to risk-weighted assets - minimum	6.00%	4.00%
Total capital to risk-weighted assets - minimum	8.00%	8.00%
Tier 1 capital to average assets - minimum	4.00%	3.00%
Comerica Bank
Summary of Capital Position [Line Items]
CET 1 capital	$ 7,081
Tier 1 capital	7,081	$ 7,051
Total capital	8,366	8,175
Risk-weighted assets	69,438	68,037
Average assets (fourth quarter)	$ 71,629	$ 69,092
CET 1 capital to risk-weighted assets	10.20%
Tier 1 capital to risk-weighted assets	10.20%	10.36%
Total capital to risk-weighted assets	12.05%	12.02%
Tier 1 capital to average assets	9.89%	10.20%
Tier 1 capital to risk-weighted assets - minimum	6.00%	4.00%
Total capital to risk-weighted assets - minimum	8.00%	8.00%
Tier 1 capital to average assets - minimum	4.00%	3.00%

Contingent Liabilities (Narrati

Contingent Liabilities (Narrative) (Details) - USD ($)	Jan. 17, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Loss Contingencies [Line Items]
Legal fees		$ 21,000,000	$ 24,000,000	$ 24,000,000
Pending Litigation
Loss Contingencies [Line Items]
Minimum amount of reasonably possible losses		0
Estimated maximum amount of reasonably possible losses		$ 33,000,000
Butte Local Development v. Masters Group v. Comerica Bank
Loss Contingencies [Line Items]
Amount of damages awarded by the jury	$ 52,000,000

Business Segment Information (N

Business Segment Information (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)marketssegments
Segment Reporting Information [Line Items]
Number of Major Business Segments | segments	3
Number of Primary Market Segments | markets	3
Business Bank
Segment Reporting Information [Line Items]
Increase In Noninterest Income Due To Presentation Change	$ 181
Increase In Noninterest Expense Due to Presentation Change	181
Other Markets
Segment Reporting Information [Line Items]
Increase In Noninterest Income Due To Presentation Change	181
Increase In Noninterest Expense Due to Presentation Change	$ 181

Business Segment Information (B

Business Segment Information (Business Segment Financial Results) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net interest income (expense) (FTE)										$ 1,693	$ 1,659	$ 1,675
Provision for credit losses										147	27	46
Noninterest income										1,050	868	882
Noninterest expenses		$ 486	$ 461	$ 436	$ 459	$ 419	$ 397	$ 404	$ 406	1,842	1,626	1,722
Provision (benefit) for income taxes (FTE)										233	281	248
Net income (loss)		$ 116	$ 136	$ 135	$ 134	$ 149	$ 154	$ 151	$ 139	521	593	541
Net loan charge-offs (recoveries)										100	25	73
Assets, average										70,247	66,336	63,933
Loans, average										48,628	46,588	44,412
Deposits, average										$ 58,326	$ 54,784	$ 51,711
Return on average assets	[1],[2]									0.74%	0.89%	0.85%
Efficiency ratio	[3],[4]									67.10%	64.31%	67.32%
Business Bank
Net interest income (expense) (FTE)										$ 1,511	$ 1,507	$ 1,495
Provision for credit losses										158	56	42
Noninterest income										574	392	398
Noninterest expenses										786	589	642
Provision (benefit) for income taxes (FTE)										376	432	410
Net income (loss)										765	822	799
Net loan charge-offs (recoveries)										89	16	32
Assets, average										38,942	37,178	35,326
Loans, average										37,883	36,198	34,268
Deposits, average										$ 30,882	$ 28,526	$ 26,131
Return on average assets	[1]									1.96%	2.21%	2.26%
Efficiency ratio	[3]									37.71%	30.97%	33.89%
Retail Bank
Net interest income (expense) (FTE)										$ 626	$ 606	$ 622
Provision for credit losses										8	(7)	24
Noninterest income										185	169	176
Noninterest expenses										734	715	719
Provision (benefit) for income taxes (FTE)										22	23	19
Net income (loss)										47	44	36
Net loan charge-offs (recoveries)										28	10	33
Assets, average										6,474	6,255	6,185
Loans, average										5,792	5,585	5,500
Deposits, average										$ 22,876	$ 21,967	$ 21,513
Return on average assets	[1]									0.20%	0.19%	0.16%
Efficiency ratio	[3]									90.37%	92.10%	89.77%
Wealth Management
Net interest income (expense) (FTE)										$ 179	$ 181	$ 180
Provision for credit losses										(20)	(21)	(17)
Noninterest income										235	241	235
Noninterest expenses										305	310	309
Provision (benefit) for income taxes (FTE)										44	49	44
Net income (loss)										85	84	79
Net loan charge-offs (recoveries)										(17)	(1)	8
Assets, average										5,153	4,988	4,799
Loans, average										4,953	4,805	4,644
Deposits, average										$ 4,151	$ 3,805	$ 3,547
Return on average assets	[1]									1.65%	1.69%	1.64%
Efficiency ratio	[3]									73.23%	73.67%	74.86%
Finance
Net interest income (expense) (FTE)										$ (632)	$ (662)	$ (653)
Provision for credit losses										0	0	0
Noninterest income										57	60	61
Noninterest expenses										9	(21)	10
Provision (benefit) for income taxes (FTE)										(209)	(224)	(226)
Net income (loss)										(375)	(357)	(376)
Net loan charge-offs (recoveries)										0	0	0
Assets, average										12,180	11,359	11,422
Loans, average										0	0	0
Deposits, average										149	233	312
Other
Net interest income (expense) (FTE)										9	27	31
Provision for credit losses										1	(1)	(3)
Noninterest income										(1)	6	12
Noninterest expenses										8	33	42
Provision (benefit) for income taxes (FTE)										0	1	1
Net income (loss)										(1)	0	3
Net loan charge-offs (recoveries)										0	0	0
Assets, average										7,498	6,556	6,201
Loans, average										0	0	0
Deposits, average										$ 268	$ 253	$ 208
[1]	Return on average assets is calculated based on the greater of average assets or average liabilities and attributed equity.
[2]	Return on average assets is calculated based on the greater of average assets or average liabilities and attributed equity.
[3]	Noninterest expenses as a percentage of the sum of net interest income (FTE) and noninterest income excluding net securities gains.
[4]	Noninterest expenses as a percentage of the sum of net interest income (FTE) and noninterest income excluding net securities gains.

Business Segment Information (M

Business Segment Information (Market Segment Financial Results) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net interest income (expense) (FTE)										$ 1,693	$ 1,659	$ 1,675
Provision for credit losses										147	27	46
Noninterest income										1,050	868	882
Noninterest expenses		$ 486	$ 461	$ 436	$ 459	$ 419	$ 397	$ 404	$ 406	1,842	1,626	1,722
Provision (benefit) for income taxes (FTE)										233	281	248
Net income (loss)		$ 116	$ 136	$ 135	$ 134	$ 149	$ 154	$ 151	$ 139	521	593	541
Net loan charge-offs (recoveries)										100	25	73
Assets, average										70,247	66,336	63,933
Loans, average										48,628	46,588	44,412
Deposits, average										$ 58,326	$ 54,784	$ 51,711
Return on average assets	[1],[2]									0.74%	0.89%	0.85%
Efficiency ratio	[3],[4]									67.10%	64.31%	67.32%
Michigan
Net interest income (expense) (FTE)										$ 720	$ 718	$ 751
Provision for credit losses										(27)	(32)	(11)
Noninterest income										333	345	343
Noninterest expenses										598	643	713
Provision (benefit) for income taxes (FTE)										157	164	140
Net income (loss)										325	288	252
Net loan charge-offs (recoveries)										8	8	6
Assets, average										13,761	13,749	13,879
Loans, average										13,180	13,336	13,461
Deposits, average										$ 21,872	$ 21,023	$ 20,346
Return on average assets	[2]									1.42%	1.31%	1.18%
Efficiency ratio	[4]									56.72%	60.48%	65.09%
California
Net interest income (expense) (FTE)										$ 736	$ 722	$ 692
Provision for credit losses										17	28	17
Noninterest income										153	147	151
Noninterest expenses										408	398	396
Provision (benefit) for income taxes (FTE)										167	169	160
Net income (loss)										297	274	270
Net loan charge-offs (recoveries)										18	22	27
Assets, average										16,881	15,668	14,233
Loans, average										16,613	15,390	13,979
Deposits, average										$ 17,763	$ 16,142	$ 14,705
Return on average assets	[2]									1.57%	1.59%	1.72%
Efficiency ratio	[4]									45.96%	45.79%	47.00%
Texas
Net interest income (expense) (FTE)										$ 521	$ 542	$ 541
Provision for credit losses										131	50	35
Noninterest income										133	142	142
Noninterest expenses										389	370	364
Provision (benefit) for income taxes (FTE)										55	96	101
Net income (loss)										79	168	183
Net loan charge-offs (recoveries)										45	9	20
Assets, average										11,778	11,645	10,694
Loans, average										11,168	10,954	9,988
Deposits, average										$ 10,882	$ 10,764	$ 10,247
Return on average assets	[2]									0.63%	1.39%	1.59%
Efficiency ratio	[4]									59.52%	54.00%	53.22%
Other Markets
Net interest income (expense) (FTE)										$ 339	$ 312	$ 313
Provision for credit losses										25	(18)	8
Noninterest income										375	168	173
Noninterest expenses										430	203	197
Provision (benefit) for income taxes (FTE)										63	75	72
Net income (loss)										196	220	209
Net loan charge-offs (recoveries)										29	(14)	20
Assets, average										8,149	7,359	7,504
Loans, average										7,667	6,908	6,984
Deposits, average										$ 7,392	$ 6,369	$ 5,893
Return on average assets	[2]									2.41%	3.00%	2.79%
Efficiency ratio	[4]									59.97%	42.30%	40.52%
Finance & Other
Net interest income (expense) (FTE)										$ (623)	$ (635)	$ (622)
Provision for credit losses										1	(1)	(3)
Noninterest income										56	66	73
Noninterest expenses										17	12	52
Provision (benefit) for income taxes (FTE)										(209)	(223)	(225)
Net income (loss)										(376)	(357)	(373)
Net loan charge-offs (recoveries)										0	0	0
Assets, average										19,678	17,915	17,623
Loans, average										0	0	0
Deposits, average										$ 417	$ 486	$ 520
[1]	Return on average assets is calculated based on the greater of average assets or average liabilities and attributed equity.
[2]	Return on average assets is calculated based on the greater of average assets or average liabilities and attributed equity.
[3]	Noninterest expenses as a percentage of the sum of net interest income (FTE) and noninterest income excluding net securities gains.
[4]	Noninterest expenses as a percentage of the sum of net interest income (FTE) and noninterest income excluding net securities gains.

Parent Company FInancial Sta135

Parent Company FInancial Statements Parent Company Financial Statements (Balance Sheets) (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Cash and due from subsidiary bank	$ 1,157	$ 1,026
Other short-term investments	113	99
Premises and equipment	550	532
Accrued income and other assets	4,117	4,434
Total assets	71,877	69,186
Medium- and long-term debt	3,058	2,675
Other liabilities	1,383	1,507
Total liabilities	64,317	61,784
Common stock - $5 par value: Authorized - 325,000,000 shares; Issued - 228,164,824 shares	1,141	1,141
Capital surplus	2,173	2,188
Accumulated other comprehensive loss	(429)	(412)	$ (391)
Retained earnings	7,084	6,744
Less cost of common stock in treasury - 52,457,113 shares at 12/31/15 and 49,146,225 shares at 12/31/14	(2,409)	(2,259)
Total shareholders' equity	7,560	7,402	$ 7,150	$ 6,939
Total liabilities and shareholders' equity	$ 71,877	$ 69,186
Common stock, par value	$ 5	$ 5
Common stock, authorized shares	325,000,000	325,000,000
Common stock, issued shares	228,164,824	228,164,824
Shares in treasury	52,457,113	49,146,225
Parent Company
Condensed Financial Statements, Captions [Line Items]
Cash and due from subsidiary bank	$ 4	$ 0
Short-term investments with subsidiary bank	569	1,133
Other short-term investments	89	94
Investments in subsidiaries, principally banks	7,523	7,411
Premises and equipment	3	2
Accrued income and other assets	137	138
Total assets	8,325	8,778
Medium- and long-term debt	608	1,208
Other liabilities	157	168
Total liabilities	765	1,376
Common stock - $5 par value: Authorized - 325,000,000 shares; Issued - 228,164,824 shares	1,141	1,141
Capital surplus	2,173	2,188
Accumulated other comprehensive loss	(429)	(412)
Retained earnings	7,084	6,744
Less cost of common stock in treasury - 52,457,113 shares at 12/31/15 and 49,146,225 shares at 12/31/14	(2,409)	(2,259)
Total shareholders' equity	7,560	7,402
Total liabilities and shareholders' equity	$ 8,325	$ 8,778

Parent Company FInancial Sta136

Parent Company FInancial Statements Parent Company Financial Statements (Statements of Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Other interest income									$ 17	$ 14	$ 14
Other noninterest income									103	130	156
Interest on medium- and long-term debt									52	50	57
Salaries and benefits expense									1,009	980	1,009
Net occupancy expense									159	171	160
Equipment expense									53	57	60
Other noninterest expenses									161	173	179
Benefit for income taxes	$ 41	$ 63	$ 64	$ 61	$ 70	$ 73	$ 70	$ 64	229	277	245
Net Income	116	136	135	134	149	154	151	139	521	593	541
Less income allocated to participating securities	1	2	1	2	1	2	2	2	6	7	8
Net income attributable to common shares	$ 115	$ 134	$ 134	$ 132	$ 148	$ 152	$ 149	$ 137	515	586	533
Parent Company
Condensed Financial Statements, Captions [Line Items]
Dividends from subsidiaries									441	384	490
Other interest income									1	1	1
Intercompany management fees									123	118	110
Other noninterest income									1	7	14
Total income									566	510	615
Interest on medium- and long-term debt									14	14	11
Salaries and benefits expense									112	114	118
Net occupancy expense									5	5	4
Equipment expense									1	1	1
Other noninterest expenses									70	70	78
Total expenses									202	204	212
Income before benefit for income taxes and equity in undistributed earnings of subsidiaries									364	306	403
Benefit for income taxes									(27)	(27)	(30)
Income before equity in undistributed earnings of subsidiaries									391	333	433
Equity in undistributed earnings of subsidiaries, principally banks									130	260	108
Net Income									521	593	541
Less income allocated to participating securities									6	7	8
Net income attributable to common shares									$ 515	$ 586	$ 533

Parent Company FInancial Sta137

Parent Company FInancial Statements Parent Company Financial Statements (Statements of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Net income	$ 116	$ 136	$ 135	$ 134	$ 149	$ 154	$ 151	$ 139	$ 521	$ 593	$ 541
Depreciation and amortization									118	123	122
Net periodic defined benefit cost									48	40	88
Share-based compensation expense									38	38	35
Provision for deferred income taxes									(71)	130	(20)
Excess tax benefits from share-based compensation arrangements									(3)	(7)	(3)
Other, net									105	(243)	(2)
Net cash provided by operating activities									862	639	836
Net change in premises and equipment									(119)	(70)	(102)
Net cash (used in) provided by investing activities									(3,255)	(3,743)	1,174
Maturities and redemptions of medium- and long-term debt									(606)	(1,406)	(1,080)
Issuances of medium- and long-term debt									1,016	596	0
Repurchases of common stock									(240)	(260)	(291)
Cash dividends paid on common stock									(147)	(137)	(123)
Issuances of common stock under employee stock plans									22	49	33
Purchase and retirement of warrants									(10)	0	0
Excess tax benefits from share-based compensation arrangements									3	7	3
Net cash (used in) provided by financing activities									2,469	2,724	(93)
Net (decrease) increase in cash and cash equivalents									76	(380)	1,917
Cash and cash equivalents at beginning of period				6,071				6,451	6,071	6,451	4,534
Cash and cash equivalents at end of period	6,147				6,071				6,147	6,071	6,451
Interest paid									94	101	114
Income taxes recovered									88	218	115
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net income									521	593	541
Undistributed earnings of subsidiaries, principally banks									(130)	(260)	(108)
Depreciation and amortization									1	1	1
Net periodic defined benefit cost									5	4	8
Share-based compensation expense									14	16	14
Provision for deferred income taxes									0	0	3
Excess tax benefits from share-based compensation arrangements									(3)	(7)	(3)
Other, net									5	16	2
Net cash provided by operating activities									413	363	458
Net change in premises and equipment									(1)	2	0
Net cash (used in) provided by investing activities									(1)	2	0
Maturities and redemptions of medium- and long-term debt									(600)	0	0
Issuances of medium- and long-term debt									0	596	0
Repurchases of common stock									(240)	(260)	(291)
Cash dividends paid on common stock									(147)	(137)	(123)
Issuances of common stock under employee stock plans									22	49	33
Purchase and retirement of warrants									(10)	0	0
Excess tax benefits from share-based compensation arrangements									3	7	3
Net cash (used in) provided by financing activities									(972)	255	(378)
Net (decrease) increase in cash and cash equivalents									(560)	620	80
Cash and cash equivalents at beginning of period				$ 1,133				$ 513	1,133	513	433
Cash and cash equivalents at end of period	$ 573				$ 1,133				573	1,133	513
Interest paid									16	12	11
Income taxes recovered									$ (62)	$ (33)	$ (27)

Summary of Quarterly Financi138

Summary of Quarterly Financial Statements (Unaudited) Summary of Quarterly Financial Statements (Unaudited) (Summary of Quarterly Financial Statements) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 457	$ 448	$ 444	$ 435	$ 438	$ 436	$ 441	$ 435	$ 1,784	$ 1,750	$ 1,784
Interest expense	24	26	23	22	23	22	25	25	95	95	112
Net interest income	433	422	421	413	415	414	416	410	1,689	1,655	1,672
Provision for credit losses	60	26	47	14	2	5	11	9	147	27	46
Net securities (losses) gains	0	0	0	(2)	0	(1)	0	1	(2)	0	(1)
Noninterest income excluding net securities (losses) gains	270	264	261	257	225	216	220	207
Noninterest expenses	486	461	436	459	419	397	404	406	1,842	1,626	1,722
Provision for income taxes	41	63	64	61	70	73	70	64	229	277	245
Net Income	116	136	135	134	149	154	151	139	521	593	541
Less income allocated to participating securities	1	2	1	2	1	2	2	2	6	7	8
Net income attributable to common shares	$ 115	$ 134	$ 134	$ 132	$ 148	$ 152	$ 149	$ 137	$ 515	$ 586	$ 533
Basic earnings per common share	$ 0.65	$ 0.76	$ 0.76	$ 0.75	$ 0.83	$ 0.85	$ 0.83	$ 0.76	$ 2.93	$ 3.28	$ 2.92
Diluted earnings per common share	$ 0.64	$ 0.74	$ 0.73	$ 0.73	$ 0.80	$ 0.82	$ 0.80	$ 0.73	$ 2.84	$ 3.16	$ 2.85
Comprehensive income	$ 31	$ 187	$ 109	$ 176	$ 54	$ 141	$ 172	$ 205	$ 504	$ 572	$ 563

Subsequent Events Subsequent Ev

Subsequent Events Subsequent Events Narrative Details (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Subsequent Event [Line Items]
Increase in provision for loan and lease losses		$ 147	$ 27	$ 46
Drop in oil and gas prices subsequent to year-end.		Subsequent to December 31, 2015, oil and gas prices dropped significantly. The allowance for loan losses allocation for energy and energy-related loans was based upon energy prices and conditions in existence at the balance sheet date.
Adjustment To Previously Reported Results [Member]
Subsequent Event [Line Items]
After-tax charge resulting from recently discovered irregularities	$ 14	$ 14
Pretax charge resulting from recently discovered irregularities	22	22
Increase in provision for loan and lease losses	25	25
Increase in loan charge-offs	25	25
Decrease in incentive compensation expense	$ 3	$ 3