M&T Bank (MTB) 10-K22 Feb 182017 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	MTB
Entity Registrant Name	M&T BANK CORP
Entity Central Index Key	36,270
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		150,176,904
Entity Public Float			$ 22,601,176,633

Consolidated Balance Sheet

Consolidated Balance Sheet - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and due from banks	$ 1,420,888	$ 1,320,549
Interest-bearing deposits at banks	5,078,903	5,000,638
Trading account	132,909	323,867
Investment securities (includes pledged securities that can be sold or repledged of $487,151 at December 31, 2017; $1,203,473 at December 31, 2016)
Available for sale (cost: $10,938,796 at December 31, 2017; $13,338,301 at December 31, 2016)	10,896,284	13,332,072
Held to maturity (fair value: $3,341,762 at December 31, 2017; $2,451,222 at December 31, 2016)	3,353,213	2,457,278
Other (fair value: $415,028 at December 31, 2017; $461,118 at December 31, 2016)	415,028	461,118
Total investment securities	14,664,525	16,250,468
Loans and leases	88,242,886	91,101,677
Unearned discount	(253,903)	(248,261)
Loans and leases, net of unearned discount	87,988,983	90,853,416
Allowance for credit losses	(1,017,198)	(988,997)
Loans and leases, net	86,971,785	89,864,419
Premises and equipment	646,451	675,263
Goodwill	4,593,112	4,593,112
Core deposit and other intangible assets	71,589	97,655
Accrued interest and other assets	5,013,325	5,323,235
Total assets	118,593,487	123,449,206
Liabilities
Noninterest-bearing deposits	33,975,180	32,813,896
Savings and interest-checking deposits	51,698,008	52,346,207
Time deposits	6,580,962	10,131,846
Deposits at Cayman Islands office	177,996	201,927
Total deposits	92,432,146	95,493,876
Short-term borrowings	175,099	163,442
Accrued interest and other liabilities	1,593,993	1,811,431
Long-term borrowings	8,141,430	9,493,835
Total liabilities	102,342,668	106,962,584
Shareholders' equity
Preferred stock, $1.00 par, 1,000,000 shares authorized; Issued and outstanding: Liquidation preference of $1,000 per share: 731,500 shares at December 31, 2016 and December 31, 2015; Liquidation preference of $10,000 per share: 50,000 shares at December 31, 2016 and December 31, 2015	1,231,500	1,231,500
Common stock, $.50 par, 250,000,000 shares authorized, 159,945,678 shares issued at December 31, 2016; 159,563,512 shares issued at December 31, 2015	79,909	79,973
Common stock issuable, 32,403 shares at December 31, 2016; 36,644 shares at December 31, 2015	1,847	2,145
Additional paid-in capital	6,590,855	6,676,948
Retained earnings	10,164,804	9,222,488
Accumulated other comprehensive income (loss), net	(363,814)	(294,636)
Treasury stock — common, at cost — 9,733,115 shares at December 31, 2017; 3,764,742 shares at December 31, 2016	(1,454,282)	(431,796)
Total shareholders’ equity	16,250,819	16,486,622
Total liabilities and shareholders’ equity	$ 118,593,487	$ 123,449,206

Consolidated Balance Sheet (Par

Consolidated Balance Sheet (Parenthetical) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Pledged securities that can be sold or repledged	$ 487,151,000	$ 1,203,473,000
Investment securities, available for sale, amortized cost	10,938,796,000	13,338,301,000
Investment securities, held to maturity, fair value	3,341,762,000	2,451,222,000
Other, fair value	$ 415,028,000	$ 461,118,000
Preferred stock, par value	$ 1	$ 1
Preferred stock, shares authorized	1,000,000	1,000,000
Common stock, par value	$ 0.50	$ 0.50
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	159,817,518	159,945,678
Common stock issuable, shares	27,138	32,403
Treasury stock, common shares	9,733,115	3,764,742
Series A and Series C [Member]
Preferred stock, shares issued	731,500	731,500
Preferred stock, shares outstanding	731,500	731,500
Preferred stock, liquidation preference per share	$ 1,000	$ 1,000
Series D Preferred Stock [Member]
Preferred stock, shares issued	50,000	50,000
Preferred stock, shares outstanding	50,000	50,000
Preferred stock, liquidation preference per share	$ 10,000	$ 10,000

Consolidated Statement of Incom

Consolidated Statement of Income - USD ($) $ in Thousands	12 Months Ended
Consolidated Statement of Income - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income
Loans and leases, including fees	$ 3,742,867	$ 3,485,050	$ 2,778,151
Investment securities
Fully taxable	361,157	361,494	372,162
Exempt from federal taxes	1,431	2,606	4,263
Deposits at banks	61,326	45,516	15,252
Other	1,014	1,205	1,016
Total interest income	4,167,795	3,895,871	3,170,844
Interest expense
Savings and interest-checking deposits	133,177	87,704	46,140
Time deposits	61,505	102,841	27,059
Deposits at Cayman Islands office	1,186	797	615
Short-term borrowings	1,511	3,625	1,677
Long-term borrowings	189,372	231,017	252,766
Total interest expense	386,751	425,984	328,257
Net interest income	3,781,044	3,469,887	2,842,587
Provision for credit losses	168,000	190,000	170,000
Net interest income after provision for credit losses	3,613,044	3,279,887	2,672,587
Other income
Mortgage banking revenues	363,827	373,697	375,738
Service charges on deposit accounts	427,372	419,102	420,608
Trust income	501,381	472,184	470,640
Brokerage services income	61,445	63,423	64,770
Trading account and foreign exchange gains	35,301	41,126	30,577
Gain (loss) on bank investment securities	21,279	30,314	(130)
Other revenues from operations	440,538	426,150	462,834
Total other income	1,851,143	1,825,996	1,825,037
Other expense
Salaries and employee benefits	1,650,729	1,623,600	1,549,530
Equipment and net occupancy	295,084	295,141	272,539
Outside data processing and software	184,670	172,389	164,133
FDIC assessments	101,871	105,045	52,113
Advertising and marketing	69,203	87,137	59,227
Printing, postage and supplies	35,960	39,546	38,491
Amortization of core deposit and other intangible assets	31,366	42,613	26,424
Other costs of operations	771,442	682,014	660,475
Total other expense	3,140,325	3,047,485	2,822,932
Income before taxes	2,323,862	2,058,398	1,674,692
Income taxes	915,556	743,284	595,025
Net income	1,408,306	1,315,114	1,079,667
Net income available to common shareholders
Basic	1,327,503	1,223,459	987,689
Diluted	$ 1,327,517	$ 1,223,481	$ 987,724
Net income per common share
Basic	$ 8.72	$ 7.80	$ 7.22
Diluted	$ 8.70	$ 7.78	$ 7.18

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Partners Capital [Abstract]
Net income	$ 1,408,306	$ 1,315,114	$ 1,079,667
Other comprehensive income (loss), net of tax and reclassification adjustments:
Net unrealized losses on investment securities	(19,766)	(64,406)	(79,114)
Cash flow hedges adjustments	(9,912)	(94)	796
Foreign currency translation adjustment	2,241	(2,614)	(925)
Defined benefit plans liability adjustments	22,288	24,105	8,610
Total other comprehensive loss	(5,149)	(43,009)	(70,633)
Total comprehensive income	$ 1,403,157	$ 1,272,105	$ 1,009,034

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net income	$ 1,408,306	$ 1,315,114	$ 1,079,667
Adjustments to reconcile net income to net cash provided by operating activities
Provision for credit losses	168,000	190,000	170,000
Depreciation and amortization of premises and equipment	109,587	106,996	99,019
Amortization of capitalized servicing rights	56,172	50,982	49,906
Amortization of core deposit and other intangible assets	31,366	42,613	26,424
Provision for deferred income taxes	400,790	174,013	396,596
Asset write-downs	15,429	21,036	9,029
Net gain on sales of assets	(53,467)	(63,222)	(67,759)
Net change in accrued interest receivable, payable	(17,896)	(12,282)	(46,338)
Net change in other accrued income and expense	(201,981)	60,263	(289,139)
Net change in loans originated for sale	711,657	(665,649)	323,330
Net change in trading account assets and liabilities	153,972	(36,453)	(8,327)
Net cash provided by operating activities	2,781,935	1,183,411	1,742,408
Cash flows from investing activities
Proceeds from sales of investment securities Available for sale	534,160	63,513	5,654,850
Proceeds from sales of investment securities Other	178,468	94,749	183,892
Proceeds from maturities of investment securities Available for sale	2,131,118	2,309,208	2,392,331
Proceeds from maturities of investment securities Held to maturity	528,585	609,080	662,959
Purchases of investment securities Available for sale	(251,185)	(3,562,711)	(3,614,324)
Purchases of investment securities Held to maturity	(1,425,690)	(214,791)	(29,431)
Purchases of investment securities Other	(132,378)	(1,808)	(99,317)
Net (increase) decrease in loans and leases	1,931,492	(2,952,129)	(2,326,744)
Net (increase) decrease in interest-bearing deposits at banks	(78,265)	2,593,712	6,445,451
Capital expenditures, net	(78,966)	(107,693)	(81,936)
Net decrease in loan servicing advances	37,761	170,141	448,271
Acquisition of bank and bank holding company, net of cash acquired			(1,932,596)
Other, net	19,825	277,961	10,876
Net cash provided (used) by investing activities	3,394,925	(720,768)	7,714,282
Cash flows from financing activities
Net increase (decrease) in deposits	(3,075,322)	3,554,673	504,393
Net increase (decrease) in short-term borrowings	11,657	(1,937,105)	(2,167,405)
Proceeds from long-term borrowings	2,145,950		1,500,000
Payments on long-term borrowings	(3,433,440)	(1,119,898)	(8,912,474)
Purchases of treasury stock	(1,205,905)	(641,334)
Dividends paid — common	(457,402)	(441,891)	(375,017)
Dividends paid — preferred	(72,734)	(81,270)	(81,270)
Redemption of Series D preferred stock		(500,000)
Other, net	10,675	161,691	69,766
Net cash used by financing activities	(6,076,521)	(510,134)	(9,462,007)
Net increase (decrease) in cash and cash equivalents	100,339	(47,491)	(5,317)
Cash and cash equivalents at beginning of year	1,320,549	1,368,040	1,373,357
Cash and cash equivalents at end of year	1,420,888	1,320,549	1,368,040
Supplemental disclosure of cash flow information
Interest received during the year	4,155,723	3,903,374	3,134,311
Interest paid during the year	405,290	498,951	400,329
Income taxes paid during the year	494,205	276,866	378,660
Supplemental schedule of noncash investing and financing activities
Real estate acquired in settlement of loans	121,292	124,033	67,753
Acquisition of bank and bank holding company
Common stock issued			3,110,581
Common stock awards converted			28,243
Fair value of Assets acquired (noncash)			36,567,632
Fair value of Liabilities assumed			31,496,212
Securitization of residential mortgage loans allocated to Available-for-sale investment securities	36,747	24,233	65,023
Securitization of residential mortgage loans allocated to capitalized servicing rights	$ 422	248	$ 646
Series F Preferred Stock [Member]
Cash flows from financing activities
Proceeds from issuance of Series F preferred stock		$ 495,000

Consolidated Statement of Chang

Consolidated Statement of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Series D Preferred Stock [Member]	Series F Preferred Stock [Member]	Series A Warrants [Member]	Preferred Stock [Member]	Preferred Stock [Member]Series D Preferred Stock [Member]	Preferred Stock [Member]Series F Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member]Series A Warrants [Member]	Common Stock Issuable [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]Series F Preferred Stock [Member]	Additional Paid-in Capital [Member]Series A Warrants [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), Net [Member]	Treasury Stock [Member]	Treasury Stock [Member]Series A Warrants [Member]
Beginning balance at Dec. 31, 2014	$ 12,335,896				$ 1,231,500			$ 66,157		$ 2,608	$ 3,409,506			$ 7,807,119	$ (180,994)
Total comprehensive income	1,009,034													1,079,667	(70,633)
Acquisition of Hudson City Bancorp, Inc, common stock issued	3,110,581							12,977			3,097,604
Acquisition of Hudson City Bancorp, Inc, common stock awards converted	28,243										28,243
Preferred stock cash dividends	(81,270)													(81,270)
Exercise of stock warrants into common stock									$ 1				$ (1)
Stock-based compensation plans:
Compensation expense, net	43,195							155			43,040
Exercises of stock options, net	88,893							438			88,455
Stock purchase plan	10,346							45			10,301
Directors’ stock plan	1,761							7			1,754
Deferred compensation plans, net, including dividend equivalents	(51)							2		(244)	293			(102)
Other	1,573										1,573
Common stock cash dividends - $2.80 per share	(374,912)													(374,912)
Ending balance at Dec. 31, 2015	16,173,289				1,231,500			79,782		2,364	6,680,768			8,430,502	(251,627)
Total comprehensive income	1,272,105													1,315,114	(43,009)
Preferred stock cash dividends	(81,270)													(81,270)
Redemption of Series D Preferred Stock		$ (500,000)				$ (500,000)
Issuance of preferred stock			$ 495,000				$ 500,000					$ (5,000)
Exercise of stock warrants into common stock				$ (2)									(4,750)				$ 4,748
Purchases of treasury stock	(641,334)															$ (641,334)
Stock-based compensation plans:
Compensation expense, net	27,290							169			16,132					10,989
Exercises of stock options, net	169,617							18			(12,190)					181,789
Stock purchase plan	10,594										275					10,319
Directors’ stock plan	2,080							2			535					1,543
Deferred compensation plans, net, including dividend equivalents	3							2		(219)	163			(93)		150
Other	1,015										1,015
Common stock cash dividends - $2.80 per share	(441,765)													(441,765)
Ending balance at Dec. 31, 2016	16,486,622				1,231,500			79,973		2,145	6,676,948			9,222,488	(294,636)	(431,796)
Total comprehensive income	1,403,157													1,408,306	(5,149)
Reclassification of income tax effects to retained earnings	(64,029)													64,029	(64,029)
Preferred stock cash dividends	(72,734)													(72,734)
Exercise of stock warrants into common stock													$ (28,746)				$ 28,746
Purchases of treasury stock	(1,205,905)															(1,205,905)
Stock-based compensation plans:
Compensation expense, net	12,004							(64)			(47,670)					59,738
Exercises of stock options, net	72,274										(12,142)					84,416
Stock purchase plan	10,831										2,563					8,268
Directors’ stock plan	1,926										270					1,656
Deferred compensation plans, net, including dividend equivalents	(156)									(298)	(368)			(85)		595
Common stock cash dividends - $2.80 per share	(457,200)													(457,200)
Ending balance at Dec. 31, 2017	$ 16,250,819				$ 1,231,500			$ 79,909		$ 1,847	$ 6,590,855			$ 10,164,804	$ (363,814)	$ (1,454,282)

Consolidated Statement of Chan8

Consolidated Statement of Changes in Shareholders' Equity (Parenthetical) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retained Earnings [Member]
Common stock per share dividend amount	$ 3	$ 2.80	$ 2.80
Series A Warrants [Member] \| Common Stock [Member]
Exercise of warrants into shares of common stock			2,315
Exercise of warrants into shares of common stock			904
Series A Warrants [Member] \| Treasury Stock [Member]
Exercise of warrants into shares of common stock	374,786	87,381
Exercise of warrants into shares of common stock	204,133	41,439

Significant accounting policies

Significant accounting policies	12 Months Ended
Significant accounting policies	Dec. 31, 2017
Accounting Policies [Abstract]
Significant accounting policies	1. Significant accounting policies M&T Bank Corporation (“M&T”) is a bank holding company headquartered in Buffalo, New York. Through subsidiaries, M&T provides individuals, corporations and other businesses, and institutions with commercial and retail banking services, including loans and deposits, trust, mortgage banking, asset management, insurance and other financial services. Banking activities are largely focused on consumers residing in New York State, Maryland, New Jersey, Pennsylvania, Delaware, Connecticut, Virginia, West Virginia and the District of Columbia and on small and medium-size businesses based in those areas. Certain subsidiaries also conduct activities in other areas. The accounting and reporting policies of M&T and subsidiaries (“the Company”) are in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and to general practices within the banking industry. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The significant accounting policies are as follows: Consolidation The consolidated financial statements include M&T and all of its subsidiaries. All significant intercompany accounts and transactions of consolidated subsidiaries have been eliminated in consolidation. The financial statements of M&T included in note 25 report investments in subsidiaries under the equity method. Information about some limited purpose entities that are affiliates of the Company but are not included in the consolidated financial statements appears in note 19. Consolidated Statement of Cash Flows For purposes of this statement, cash and due from banks and federal funds sold are considered cash and cash equivalents. Securities purchased under agreements to resell and securities sold under agreements to repurchase Securities purchased under agreements to resell and securities sold under agreements to repurchase are treated as collateralized financing transactions and are recorded at amounts equal to the cash or other consideration exchanged. It is generally the Company’s policy to take possession of collateral pledged to secure agreements to resell. Trading account Financial instruments used for trading purposes are stated at fair value. Realized gains and losses and unrealized changes in fair value of financial instruments utilized in trading activities are included in “trading account and foreign exchange gains” in the consolidated statement of income. Investment securities Investments in debt securities are classified as held to maturity and stated at amortized cost when management has the positive intent and ability to hold such securities to maturity. Investments in other debt securities and equity securities having readily determinable fair values are classified as available for sale and stated at estimated fair value. Amortization of premiums and accretion of discounts for investment securities available for sale and held to maturity are included in interest income. Other securities are stated at cost and include stock of the Federal Reserve Bank of New York and the Federal Home Loan Bank (“FHLB”) of New York. Individual securities are written down through a charge to earnings when declines in value below the cost basis of a security are considered to be other than temporary. In cases where fair value is less than amortized cost and the Company intends to sell a debt security, it is more likely than not to be required to sell a debt security before recovery of its amortized cost basis, or the Company does not expect to recover the entire amortized cost basis of a debt security, an other-than-temporary impairment is considered to have occurred. If the Company intends to sell the debt security or more likely than not will be required to sell the security before recovery of its amortized cost basis, the other-than-temporary impairment is recognized in earnings equal to the entire difference between the debt security’s amortized cost basis and its fair value. If the Company does not expect to recover the entire amortized cost basis of the security, the Company does not intend to sell the security and it is not more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis, the other-than-temporary impairment is separated into (a) the amount representing the credit loss and (b) the amount related to all other factors. The amount of the other-than-temporary impairment related to the credit loss is recognized in earnings while the amount related to other factors is recognized in other comprehensive income, net of applicable taxes. Subsequently, the Company accounts for the other-than-temporarily impaired debt security as if the security had been purchased on the measurement date of the other-than-temporary impairment at an amortized cost basis equal to the previous amortized cost basis less the other-than-temporary impairment recognized in earnings. Realized gains and losses on the sales of investment securities are determined using the specific identification method. Loans and leases The Company’s accounting methods for loans depends on whether the loans were originated by the Company or were acquired in a business combination. Originated loans and leases Interest income on loans is accrued on a level yield method. Loans are placed on nonaccrual status and previously accrued interest thereon is charged against income when principal or interest is delinquent 90 days, unless management determines that the loan status clearly warrants other treatment. Nonaccrual commercial loans and commercial real estate loans are returned to accrual status when borrowers have demonstrated an ability to repay their loans and there are no delinquent principal and interest payments. Consumer loans not secured by residential real estate are returned to accrual status when all past due principal and interest payments have been paid by the borrower. Loans secured by residential real estate are returned to accrual status when they are deemed to have an insignificant delay in payments of 90 days or less. Loan balances are charged off when it becomes evident that such balances are not fully collectible. For commercial loans and commercial real estate loans, charge-offs are recognized after an assessment by credit personnel of the capacity and willingness of the borrower to repay, the estimated value of any collateral, and any other potential sources of repayment. A charge-off is recognized when, after such assessment, it becomes evident that the loan balance is not fully collectible. For loans secured by residential real estate, the excess of the loan balances over the net realizable value of the property collateralizing the loan is charged-off when the loan becomes 150 days delinquent. Consumer loans are generally charged-off when the loans are 91 to 180 days past due, depending on whether the loan is collateralized and the status of repossession activities with respect to such collateral. Loan fees and certain direct loan origination costs are deferred and recognized as an interest yield adjustment over the life of the loan. Net deferred fees have been included in unearned discount as a reduction of loans outstanding. Commitments to sell real estate loans are utilized by the Company to hedge the exposure to changes in fair value of real estate loans held for sale. The carrying value of hedged real estate loans held for sale recorded in the consolidated balance sheet includes changes in estimated fair market value during the hedge period, typically from the date of close through the sale date. Valuation adjustments made on these loans and commitments are included in “mortgage banking revenues.” Except for consumer and residential mortgage loans that are considered smaller balance homogenous loans and are evaluated collectively, the Company considers a loan to be impaired for purposes of applying GAAP when, based on current information and events, it is probable that the Company will be unable to collect all amounts according to the contractual terms of the loan agreement or the loan is delinquent 90 days. Regardless of loan type, the Company considers a loan to be impaired if it qualifies as a troubled debt restructuring. Impaired loans are classified as either nonaccrual or as loans renegotiated at below market rates which continue to accrue interest, provided that a credit assessment of the borrower’s financial condition results in an expectation of full repayment under the modified contractual terms. Certain loans greater than 90 days delinquent are not considered impaired if they are well-secured and in the process of collection. Loans less than 90 days delinquent are deemed to have an insignificant delay in payment and are generally not considered impaired. Impairment of a loan is measured based on the present value of expected future cash flows discounted at the loan’s effective interest rate, the loan’s observable market price, or the fair value of collateral if the loan is collateral-dependent. Interest received on impaired loans placed on nonaccrual status is generally applied to reduce the carrying value of the loan or, if principal is considered fully collectible, recognized as interest income. Residual value estimates for commercial leases are generally determined through internal or external reviews of the leased property. The Company reviews commercial lease residual values at least annually and recognizes residual value impairments deemed to be other than temporary. Loans and leases acquired in a business combination Loans acquired in a business combination subsequent to December 31, 2008 are initially recorded at fair value with no carry-over of an acquired entity’s previously established allowance for credit losses. Purchased impaired loans represent specifically identified loans with evidence of credit deterioration for which it was probable at acquisition that the Company would be unable to collect all contractual principal and interest payments. For purchased impaired loans and other loans acquired at a discount that was, in part, attributable to credit quality, the excess of cash flows expected at acquisition over the estimated fair value of acquired loans is recognized as interest income over the remaining lives of the loans. Subsequent decreases in the expected principal cash flows require the Company to evaluate the need for additions to the Company’s allowance for credit losses. Subsequent improvements in expected cash flows result first in the recovery of any related allowance for credit losses and then in recognition of additional interest income over the then-remaining lives of the loans. For all other acquired loans, the difference between the fair value and outstanding principal balance of the loans is recognized as an adjustment to interest income over the lives of those loans. Those loans are then accounted for in a manner that is similar to originated loans. Allowance for credit losses The allowance for credit losses represents, in management’s judgment, the amount of losses inherent in the loan and lease portfolio as of the balance sheet date. The allowance is determined by management’s evaluation of the loan and lease portfolio based on such factors as the differing economic risks associated with each loan category, the current financial condition of specific borrowers, the economic environment in which borrowers operate, the level of delinquent loans, the value of any collateral and, where applicable, the existence of any guarantees or indemnifications. The effects of probable decreases in expected principal cash flows on loans acquired at a discount are also considered in the establishment of the allowance for credit losses. Assets taken in foreclosure of defaulted loans Assets taken in foreclosure of defaulted loans are primarily comprised of commercial and residential real property and are included in “other assets” in the consolidated balance sheet. An in-substance repossession or foreclosure occurs and a creditor is considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan upon either (1) the creditor obtaining legal title to the residential real estate property upon completion of a foreclosure or (2) the borrower conveying all interest in the residential real estate property to the creditor to satisfy that loan through completion of a deed in lieu of foreclosure or through a similar legal agreement. Upon acquisition of assets taken in satisfaction of a defaulted loan, the excess of the remaining loan balance over the asset’s estimated fair value less costs to sell is charged-off against the allowance for credit losses. Subsequent declines in value of the assets are recognized as “other costs of operations” in the consolidated statement of income. Premises and equipment Premises and equipment are stated at cost less accumulated depreciation. Depreciation expense is computed principally using the straight-line method over the estimated useful lives of the assets. Capitalized servicing rights Capitalized servicing assets are included in “other assets” in the consolidated balance sheet. Separately recognized servicing assets are initially measured at fair value. The Company uses the amortization method to subsequently measure servicing assets. Under that method, capitalized servicing assets are charged to expense in proportion to and over the period of estimated net servicing income. To estimate the fair value of servicing rights, the Company considers market prices for similar assets and the present value of expected future cash flows associated with the servicing rights calculated using assumptions that market participants would use in estimating future servicing income and expense. Such assumptions include estimates of the cost of servicing loans, loan default rates, an appropriate discount rate, and prepayment speeds. For purposes of evaluating and measuring impairment of capitalized servicing rights, the Company stratifies such assets based on the predominant risk characteristics of the underlying financial instruments that are expected to have the most impact on projected prepayments, cost of servicing and other factors affecting future cash flows associated with the servicing rights. Such factors may include financial asset or loan type, note rate and term. The amount of impairment recognized is the amount by which the carrying value of the capitalized servicing rights for a stratum exceeds estimated fair value. Impairment is recognized through a valuation allowance. Sales and securitizations of financial assets Transfers of financial assets for which the Company has surrendered control of the financial assets are accounted for as sales. Interests in a sale of financial assets that continue to be held by the Company, including servicing rights, are measured at fair value. The fair values of retained debt securities are generally determined through reference to independent pricing information. The fair values of retained servicing rights and any other retained interests are determined based on the present value of expected future cash flows associated with those interests and by reference to market prices for similar assets. Securitization structures typically require the use of special-purpose trusts that are considered variable interest entities. A variable interest entity is included in the consolidated financial statements if the Company has the power to direct the activities that most significantly impact the variable interest entity’s economic performance and has the obligation to absorb losses or the right to receive benefits of the variable interest entity that could potentially be significant to that entity. Goodwill and core deposit and other intangible assets Goodwill represents the excess of the cost of an acquired entity over the fair value of the identifiable net assets acquired. Goodwill is not amortized, but rather is tested for impairment at least annually at the reporting unit level, which is either at the same level or one level below an operating segment. Other acquired intangible assets with finite lives, such as core deposit intangibles, are initially recorded at estimated fair value and are amortized over their estimated lives. Core deposit and other intangible assets are generally amortized using accelerated methods over estimated useful lives of five to ten years. The Company periodically assesses whether events or changes in circumstances indicate that the carrying amounts of core deposit and other intangible assets may be impaired. Derivative financial instruments The Company accounts for derivative financial instruments at fair value. If certain conditions are met, a derivative may be specifically designated as (a) a hedge of the exposure to changes in the fair value of a recognized asset or liability or an unrecognized firm commitment, (b) a hedge of the exposure to variable cash flows of a forecasted transaction or (c) a hedge of the foreign currency exposure of a net investment in a foreign operation, an unrecognized firm commitment, an available-for-sale security, or a foreign currency denominated forecasted transaction. The Company utilizes interest rate swap agreements as part of the management of interest rate risk to modify the repricing characteristics of certain portions of its portfolios of earning assets and interest-bearing liabilities. For such agreements, amounts receivable or payable are recognized as accrued under the terms of the agreement and the net differential is recorded as an adjustment to interest income or expense of the related asset or liability. Interest rate swap agreements may be designated as either fair value hedges or cash flow hedges. In a fair value hedge, the fair values of the interest rate swap agreements and changes in the fair values of the hedged items are recorded in the Company’s consolidated balance sheet with the corresponding gain or loss recognized in current earnings. The difference between changes in the fair values of interest rate swap agreements and the hedged items represents hedge ineffectiveness and is recorded in “other revenues from operations” in the consolidated statement of income. In a cash flow hedge, the effective portion of the derivative’s unrealized gain or loss is initially recorded as a component of other comprehensive income and subsequently reclassified into earnings when the forecasted transaction affects earnings. The ineffective portion of the unrealized gain or loss is reported in “other revenues from operations” immediately. The Company utilizes commitments to sell real estate loans to hedge the exposure to changes in the fair value of real estate loans held for sale. Commitments to originate real estate loans to be held for sale and commitments to sell real estate loans are generally recorded in the consolidated balance sheet at estimated fair value. Derivative instruments not related to mortgage banking activities, including financial futures commitments and interest rate swap agreements, that do not satisfy the hedge accounting requirements are recorded at fair value and are generally classified as trading account assets or liabilities with resultant changes in fair value being recognized in “trading account and foreign exchange gains” in the consolidated statement of income. Stock-based compensation Stock-based compensation expense is recognized over the vesting period of the stock-based grant based on the estimated grant date value of the stock-based compensation, except that the recognition of compensation costs is accelerated for stock-based awards granted to retirement-eligible employees and employees who will become retirement-eligible prior to full vesting of the award because the Company’s incentive compensation plan allows for vesting at the time an employee retires. As discussed in note 26 herein, effective January 2017 the Company adopted amended accounting guidance which requires excess tax benefits or deficiencies associated with stock-based compensation be recognized in income tax expense. Previously, tax effects resulting from changes in M&T’s share price were recorded through shareholders’ equity. Income taxes Deferred tax assets and liabilities are recognized for the future tax effects attributable to differences between the financial statement value of existing assets and liabilities and their respective tax bases and carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates and laws. The Company evaluates uncertain tax positions using the two-step process required by GAAP. The first step requires a determination of whether it is more likely than not that a tax position will be sustained upon examination, including resolution of any related appeals or litigation processes, based on the technical merits of the position. Under the second step, a tax position that meets the more-likely-than-not recognition threshold is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. The Company accounts for its investments in qualified affordable housing projects using the proportional amortization method. Under that method, the Company amortizes the initial cost of the investment in proportion to the tax credits and other tax benefits received and recognizes the net investment performance in the income statement as a component of income tax expense. Earnings per common share Basic earnings per common share exclude dilution and are computed by dividing income available to common shareholders by the weighted-average number of common shares outstanding (exclusive of shares represented by the unvested portion of restricted stock and restricted stock unit grants) and common shares issuable under deferred compensation arrangements during the period. Diluted earnings per common share reflect shares represented by the unvested portion of restricted stock and restricted stock unit grants and the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock or resulted in the issuance of common stock that then shared in earnings. Proceeds assumed to have been received on such exercise or conversion are assumed to be used to purchase shares of M&T common stock at the average market price during the period, as required by the “treasury stock method” of accounting. GAAP requires that unvested share-based payment awards that contain nonforfeitable rights to dividends or dividend equivalents (whether paid or unpaid) shall be considered participating securities and shall be included in the computation of earnings per common share pursuant to the two-class method. The Company has issued stock-based compensation awards in the form of restricted stock and restricted stock units that contain such rights and, accordingly, the Company’s earnings per common share are calculated using the two-class method. Treasury stock Repurchases of shares of M&T common stock are recorded at cost as a reduction of shareholders’ equity. Reissuances of shares of treasury stock are recorded at average cost.

Acquisition and divestiture

Acquisition and divestiture	12 Months Ended
Acquisition and divestiture	Dec. 31, 2017
Business Combinations [Abstract]
Acquisition and divestiture	2. Acquisition and divestiture Hudson City Bancorp, Inc. On November 1, 2015, M&T completed the acquisition of Hudson City Bancorp, Inc. (“Hudson City”), headquartered in Paramus, New Jersey. On that date, Hudson City Savings Bank, the banking subsidiary of Hudson City, was merged into M&T Bank, a wholly owned banking subsidiary of M&T. Hudson City Savings Bank operated 135 banking offices in New Jersey, Connecticut and New York at the date of acquisition. The results of operations acquired in the Hudson City transaction have been included in the Company’s financial results since November 1, 2015. After application of the election, allocation and proration procedures contained in the merger agreement with Hudson City, M&T paid $2.1 billion in cash and issued 25,953,950 shares of M&T common stock in exchange for Hudson City shares outstanding at the time of the acquisition. The purchase price was approximately $5.2 billion based on the cash paid to Hudson City shareholders, the fair value of M&T stock exchanged and the estimated fair value of Hudson City stock awards converted into M&T stock awards. The acquisition of Hudson City expanded the Company’s presence in New Jersey, Connecticut and New York, and management expects that the Company will benefit from greater geographic diversity and the advantages of scale associated with a larger company. The Hudson City transaction was accounted for using the acquisition method of accounting and, accordingly, assets acquired, liabilities assumed and consideration exchanged were recorded at estimated fair value on the acquisition date. Assets acquired totaled approximately $36.7 billion, including $19.0 billion of loans (predominantly residential real estate loans) and $7.9 billion of investment securities. Liabilities assumed aggregated $31.5 billion, including $17.9 billion of deposits and $13.2 billion of borrowings. Immediately following the acquisition, the Company restructured its balance sheet by selling $5.8 billion of investment securities obtained in the acquisition and repaying $10.6 billion of borrowings assumed in the transaction. In connection with the acquisition, the Company recorded approximately $1.1 billion of goodwill and $132 million of core deposit intangible. The core deposit intangible asset is being amortized over a period of seven years using an accelerated method. The following table discloses the impact of Hudson City since the acquisition on November 1, 2015 through the end of 2015. The table also presents certain pro forma information as if Hudson City had been included in the Company’s consolidated financial statements for all of 2015. These results combine the historical results of Hudson City into the Company’s consolidated statement of income and, while certain adjustments were made for the estimated impact of certain fair valuation adjustments and other acquisition-related activity, they are not necessarily indicative of what would have occurred had the acquisition taken place on the indicated date. Actual Since Acquisition Pro Forma Through Year Ended December 31, 2015 December 31, 2015 (In thousands) Total revenues(a) $ 111,168 $ 5,132,662 Net income (loss) (21,175 ) 1,011,463 (a) Represents net interest income plus other income. In connection with the Hudson City acquisition, the Company incurred merger-related expenses of $36 million in 2016 and $97 million in 2015 related to systems conversions and other costs of integrating and conforming acquired operations with and into the Company. Those expenses consisted largely of professional services and other temporary help fees associated with preparing for systems conversions and/or integration of operations; costs related to termination of existing contractual arrangements for various services; initial marketing and promotion expenses designed to introduce M&T Bank to its new customers; severance (for former Hudson City employees); travel costs; and other costs of completing the transaction and commencing operations in new markets and offices. In 2015, the Company also recognized a $21 million provision for credit losses related to the $18.3 billion of Hudson City loans acquired at a premium. GAAP does not allow the credit loss component of the net premium associated with those loans to be bifurcated and accounted for as a nonaccreting difference as is the case with purchased impaired loans and other loans acquired at a discount. Nevertheless, GAAP requires that an allowance for credit losses be recognized for incurred losses in loans acquired at a premium even though in a relatively homogenous portfolio of residential mortgage loans the specific loans to which the losses relate cannot be individually identified at the acquisition date. Given the recognition of such losses above and beyond the impact of forecasted losses used in determining the fair value of the loans acquired at a premium, the initial $21 million provision for credit losses has been noted as a merger-related expense. There were no merger related expenses in 2017. A summary of merger-related expenses included in the consolidated statement of income for the years ended December 31, 2016 and 2015 follows: 2016 2015 (In thousands) Salaries and employee benefits $ 5,334 $ 51,287 Equipment and net occupancy 1,278 3 Outside data processing and software 1,067 785 Advertising and marketing 10,522 79 Printing, postage and supplies 1,482 504 Other costs of operations 16,072 23,318 Other expense 35,755 75,976 Provision for credit losses — 21,000 Total $ 35,755 $ 96,976 Sale of trust accounts In April 2015, the Company sold the trade processing business within the retirement services division of its Institutional Client Services business. That sale resulted in an after-tax gain of $23 million ($45 million pre-tax) that reflected the allocation of approximately $11 million of previously recorded goodwill to the divested business. Revenues of the sold business had been included in “trust income” and were $9 million during 2015. After considering related expenses, net income attributable to the business that was sold was not material to the consolidated results of operations of the Company in 2015.

Investment securities

Investment securities	12 Months Ended
Investment securities	Dec. 31, 2017
Investments Debt And Equity Securities [Abstract]
Investment securities	3. Investment securities The amortized cost and estimated fair value of investment securities were as follows: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value (In thousands) December 31, 2017 Investment securities available for sale: U.S. Treasury and federal agencies $ 1,965,665 $ — $ 18,178 $ 1,947,487 Obligations of states and political subdivisions 2,555 36 2 2,589 Mortgage-backed securities: Government issued or guaranteed 8,755,482 59,497 98,587 8,716,392 Privately issued 28 — — 28 Other debt securities 136,905 2,402 10,475 128,832 Equity securities 78,161 23,219 424 100,956 10,938,796 85,154 127,666 10,896,284 Investment securities held to maturity: Obligations of states and political subdivisions 24,562 109 49 24,622 Mortgage-backed securities: Government issued or guaranteed 3,187,953 27,236 13,746 3,201,443 Privately issued 135,688 2,574 27,575 110,687 Other debt securities 5,010 — — 5,010 3,353,213 29,919 41,370 3,341,762 Other securities 415,028 — — 415,028 Total $ 14,707,037 $ 115,073 $ 169,036 $ 14,653,074 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value (In thousands) December 31, 2016 Investment securities available for sale: U.S. Treasury and federal agencies $ 1,912,110 $ 386 $ 9,952 $ 1,902,544 Obligations of states and political subdivisions 3,570 77 6 3,641 Mortgage-backed securities: Government issued or guaranteed 10,980,507 88,343 113,989 10,954,861 Privately issued 45 — 1 44 Other debt securities 134,105 1,407 16,996 118,516 Equity securities 307,964 45,073 571 352,466 13,338,301 135,286 141,515 13,332,072 Investment securities held to maturity: Obligations of states and political subdivisions 60,858 267 224 60,901 Mortgage-backed securities: Government issued or guaranteed 2,233,173 37,498 7,374 2,263,297 Privately issued 157,704 897 37,120 121,481 Other debt securities 5,543 — — 5,543 2,457,278 38,662 44,718 2,451,222 Other securities 461,118 — — 461,118 Total $ 16,256,697 $ 173,948 $ 186,233 $ 16,244,412 No investment in securities of a single non-U.S. Government, government agency or government guaranteed issuer exceeded ten percent of shareholders’ equity at December 31, 2017. As of December 31, 2017, the latest available investment ratings of all obligations of states and political subdivisions, privately issued mortgage-backed securities and other debt securities were: Average Credit Rating of Fair Value Amount Amortized Cost Estimated Fair Value A or Better BBB BB B or Less Not Rated (In thousands) Obligations of states and political subdivisions $ 27,117 $ 27,211 $ 15,874 $ — $ — $ — $ 11,337 Privately issued mortgage-backed securities 135,716 110,715 23,459 16 — 87,233 7 Other debt securities 141,915 133,842 6,980 61,054 32,684 — 33,124 Total $ 304,748 $ 271,768 $ 46,313 $ 61,070 $ 32,684 $ 87,233 $ 44,468 The amortized cost and estimated fair value of collateralized mortgage obligations included in mortgage-backed securities were as follows: December 31 2017 2016 (In thousands) Collateralized mortgage obligations: Amortized cost $ 138,527 $ 162,027 Estimated fair value 113,516 125,848 Gross realized gains on investment securities were $23,251,000 in 2017 and $30,545,000 in 2016. During 2017, the Company sold a portion of its Fannie Mae and Freddie Mac preferred stock holdings held in the available-for-sale investment securities portfolio for a gain of $18 million. During 2016, the Company sold its collateralized debt obligations held in the available-for-sale portfolio for a gain of $30 million. There were no significant gross realized losses from sales of investment securities in 2017 or 2016. There were no significant gross realized gains or losses from sales of investment securities in 2015. At December 31, 2017, the amortized cost and estimated fair value of debt securities by contractual maturity were as follows: Amortized Cost Estimated Fair Value (In thousands) Debt securities available for sale: Due in one year or less $ 616,908 613,866 Due after one year through five years 1,356,410 1,341,344 Due after five years through ten years 72,642 72,580 Due after ten years 59,165 51,118 2,105,125 2,078,908 Mortgage-backed securities available for sale 8,755,510 8,716,420 $ 10,860,635 10,795,328 Debt securities held to maturity: Due in one year or less $ 14,622 14,656 Due after one year through five years 9,844 9,865 Due after five years through ten years 96 101 Due after ten years 5,010 5,010 29,572 29,632 Mortgage-backed securities held to maturity 3,323,641 3,312,130 $ 3,353,213 3,341,762 A summary of investment securities that as of December 31, 2017 and 2016 had been in a continuous unrealized loss position for less than twelve months and those that had been in a continuous unrealized loss position for twelve months or longer follows: Less Than 12 Months 12 Months or More Fair Value Unrealized Losses Fair Value Unrealized Losses (In thousands) December 31, 2017 Investment securities available for sale: U.S. Treasury and federal agencies $ 278,132 (1,761 ) 1,669,355 (16,417 ) Obligations of states and political subdivisions — — 474 (2 ) Mortgage-backed securities: Government issued or guaranteed 2,106,142 (13,695 ) 3,138,841 (84,892 ) Other debt securities 3,067 (26 ) 61,159 (10,449 ) Equity securities — — 18,162 (424 ) 2,387,341 (15,482 ) 4,887,991 (112,184 ) Investment securities held to maturity: Obligations of states and political subdivisions 2,954 (4 ) 6,110 (45 ) Mortgage-backed securities: Government issued or guaranteed 1,331,759 (7,036 ) 265,695 (6,710 ) Privately issued 5,061 (1,216 ) 55,255 (26,359 ) 1,339,774 (8,256 ) 327,060 (33,114 ) Total $ 3,727,115 (23,738 ) 5,215,051 (145,298 ) December 31, 2016 Investment securities available for sale: U.S. Treasury and federal agencies $ 1,710,241 (9,950 ) 2,295 (2 ) Obligations of states and political subdivisions — — 593 (6 ) Mortgage-backed securities: Government issued or guaranteed 6,730,829 (113,374 ) 81,003 (615 ) Privately issued — — 27 (1 ) Other debt securities 100 (1 ) 85,400 (16,995 ) Equity securities 17,776 (422 ) 151 (149 ) 8,458,946 (123,747 ) 169,469 (17,768 ) Investment securities held to maturity: Obligations of states and political subdivisions 17,988 (126 ) 11,891 (98 ) Mortgage-backed securities: Government issued or guaranteed 618,832 (6,842 ) 17,481 (532 ) Privately issued 17,911 (1,222 ) 57,016 (35,898 ) 654,731 (8,190 ) 86,388 (36,528 ) Total $ 9,113,677 (131,937 ) 255,857 (54,296 ) The Company owned 1,163 individual investment securities with aggregate gross unrealized losses of $169 million at December 31, 2017. Based on a review of each of the securities in the investment securities portfolio at December 31, 2017, the Company concluded that it expected to recover the amortized cost basis of its investment. As of December 31, 2017, the Company does not intend to sell nor is it anticipated that it would be required to sell any of its impaired investment securities at a loss. At December 31, 2017, the Company has not identified events or changes in circumstances which may have a significant adverse effect on the fair value of the $415 million of cost method investment securities. At December 31, 2017, investment securities with a carrying value of $2,401,871,000, including $1,942,287,000 of investment securities available for sale, were pledged to secure borrowings from various FHLBs, repurchase agreements, governmental deposits, interest rate swap agreements and available lines of credit as described in note 9. Investment securities pledged by the Company to secure obligations whereby the secured party is permitted by contract or custom to sell or repledge such collateral totaled $487,151,000 at December 31, 2017. The pledged securities included securities of the U.S. Treasury and federal agencies and mortgage-backed securities.

Loans and leases

Loans and leases	12 Months Ended
Loans and leases	Dec. 31, 2017
Receivables [Abstract]
Loans and leases	4. Loans and leases Total loans and leases outstanding were comprised of the following: December 31 2017 2016 (In thousands) Loans Commercial, financial, etc. $ 20,474,696 $ 21,351,119 Real estate: Residential 19,619,259 22,584,141 Commercial 25,345,779 25,550,057 Construction 8,125,925 8,066,756 Consumer 13,251,665 12,130,094 Total loans 86,817,324 89,682,167 Leases Commercial 1,425,562 1,419,510 Total loans and leases 88,242,886 91,101,677 Less: unearned discount (253,903 ) (248,261 ) Total loans and leases, net of unearned discount $ 87,988,983 $ 90,853,416 One-to-four family residential mortgage loans held for sale were $356 million at December 31, 2017 and $414 million at December 31, 2016. Commercial real estate loans held for sale were $22 million at December 31, 2017 and $643 million at December 31, 2016. As of December 31, 2017, approximately $3.3 billion of commercial real estate loan balances serviced for others had been sold with recourse in conjunction with the Company’s participation in the Fannie Mae Delegated Underwriting and Servicing (“DUS”) program. At December 31, 2017, the Company estimated that the recourse obligations described above were not material to the Company’s consolidated financial position. There have been no material losses incurred as a result of those credit recourse arrangements. In addition to recourse obligations, as described in note 21, the Company is contractually obligated to repurchase previously sold residential real estate loans that do not ultimately meet investor sale criteria related to underwriting procedures or loan documentation. When required to do so, the Company may reimburse loan purchasers for losses incurred or may repurchase certain loans. Charges incurred for such obligation, which are recorded as a reduction of mortgage banking revenues, were not material in 2017, 2016 or 2015. A summary of current, past due and nonaccrual loans as of December 31, 2017 and 2016 follows: Current 30-89 Days Past Due Accruing Loans Past Due 90 Days or More (a) Accruing Loans Acquired at a Discount Past Due 90 days or More (b) Purchased Impaired (c) Nonaccrual Total (In thousands) December 31, 2017 Commercial, financial, leasing, etc. $ 21,332,234 167,756 1,322 327 21 240,991 $ 21,742,651 Real estate: Commercial 24,910,381 166,305 4,444 6,016 16,815 184,982 25,288,943 Residential builder and developer 1,618,973 5,159 — — 1,135 6,451 1,631,718 Other commercial construction 6,407,451 23,467 — — 4,706 10,088 6,445,712 Residential 15,376,759 474,372 233,437 7,582 282,102 235,834 16,610,086 Residential — limited documentation 2,718,019 83,898 — — 105,236 96,105 3,003,258 Consumer: Home equity lines and loans 5,171,345 38,546 — 9,391 — 74,500 5,293,782 Automobile 3,441,371 78,511 — — — 23,781 3,543,663 Other 4,349,071 40,929 5,202 24,102 — 9,866 4,429,170 Total $ 85,325,604 1,078,943 244,405 47,418 410,015 882,598 $ 87,988,983 December 31, 2016 Commercial, financial, leasing, etc. $ 22,287,857 53,503 6,195 417 641 261,434 $ 22,610,047 Real estate: Commercial 25,076,684 183,531 7,054 12,870 31,404 176,201 25,487,744 Residential builder and developer 1,884,989 4,667 5 1,952 14,006 16,707 1,922,326 Other commercial construction 5,985,118 77,701 922 198 14,274 18,111 6,096,324 Residential 17,631,377 485,468 281,298 11,537 378,549 229,242 19,017,471 Residential — limited documentation 3,239,344 88,366 — — 139,158 106,573 3,573,441 Consumer: Home equity lines and loans 5,502,091 44,565 — 12,678 — 81,815 5,641,149 Automobile 2,869,232 56,158 — 1 — 18,674 2,944,065 Other 3,491,629 31,286 5,185 21,491 — 11,258 3,560,849 Total $ 87,968,321 1,025,245 300,659 61,144 578,032 920,015 $ 90,853,416 (a) Excludes loans acquired at a discount. (b) Loans acquired at a discount that were recorded at fair value at acquisition date. This category does not include purchased impaired loans that are presented separately. (c) Accruing loans acquired at a discount that were impaired at acquisition date and recorded at fair value. If nonaccrual and renegotiated loans had been accruing interest at their originally contracted terms, interest income on such loans would have amounted to $63,872,000 in 2017, $68,371,000 in 2016 and $56,784,000 in 2015. The actual amounts included in interest income during 2017, 2016 and 2015 on such loans were $31,425,000, $33,941,000 and $30,735,000, respectively. The outstanding principal balance and the carrying amount of loans acquired at a discount that were recorded at fair value at the acquisition date and included in the consolidated balance sheet were as follows: December 31 2017 2016 (In thousands) Outstanding principal balance $ 1,394,188 $ 2,311,699 Carrying amount: Commercial, financial, leasing, etc. 31,105 59,928 Commercial real estate 228,054 456,820 Residential real estate 620,827 799,802 Consumer 123,413 487,721 $ 1,003,399 $ 1,804,271 Purchased impaired loans included in the table above totaled $410 million at December 31, 2017 and $578 million at December 31, 2016, representing less than 1% of the Company’s assets as of each date. A summary of changes in the accretable yield for loans acquired at a discount for the years ended December 31, 2017, 2016 and 2015 follows: For the Year Ended December 31, 2017 2016 2015 Purchased Other Purchased Other Purchased Other Impaired Acquired Impaired Acquired Impaired Acquired (In thousands) Balance at beginning of period $ 154,233 $ 201,153 $ 184,618 $ 296,434 $ 76,518 $ 397,379 Additions — — — — 117,251 — Interest income (47,452 ) (82,605 ) (52,769 ) (123,044 ) (28,551 ) (158,260 ) Reclassifications from nonaccretable balance 51,137 16,437 22,384 22,677 19,400 49,930 Other(a) — (1,823 ) — 5,086 — 7,385 Balance at end of period $ 157,918 $ 133,162 $ 154,233 $ 201,153 $ 184,618 $ 296,434 (a) Other changes in expected cash flows including changes in interest rates and prepayment assumptions. During the normal course of business, the Company modifies loans to maximize recovery efforts. If the borrower is experiencing financial difficulty and a concession is granted, the Company considers such modifications as troubled debt restructurings and classifies those loans as either nonaccrual loans or renegotiated loans. The types of concessions that the Company grants typically include principal deferrals and interest rate concessions, but may also include other types of concessions. The tables that follow summarize the Company’s loan modification activities that were considered troubled debt restructurings for the years ended December 31, 2017, 2016 and 2015: Post-modification (a) Number Pre- modification recorded investment Principal Deferral Other Combination of Concession Types Total Year Ended December 31, 2017 (Dollars in thousands) Commercial, financial, leasing, etc. 217 $ 111,036 $ 25,051 $ 6,459 $ 57,153 $ 88,663 Real estate: Commercial 83 44,924 17,039 868 22,975 40,882 Residential builder and developer 3 12,291 — — 10,879 10,879 Other commercial construction 2 168 168 — — 168 Residential 141 31,827 16,633 — 17,974 34,607 Residential — limited documentation 20 4,230 911 — 3,661 4,572 Consumer: Home equity lines and loans 110 10,049 1,137 491 8,585 10,213 Automobile 69 1,378 1,203 — 175 1,378 Other 9 160 160 — — 160 Total 654 $ 216,063 $ 62,302 $ 7,818 $ 121,402 $ 191,522 Year Ended December 31, 2016 Commercial, financial, leasing, etc. 164 $ 154,093 $ 102,446 $ — $ 41,673 $ 144,119 Real estate: Commercial 81 44,870 23,558 4,576 15,603 43,737 Residential builder and developer 6 39,660 22,958 — 15,123 38,081 Other commercial construction 3 3,113 250 — 2,782 3,032 Residential 119 20,057 11,771 — 9,367 21,138 Residential — limited documentation 21 3,560 1,047 — 2,917 3,964 Consumer: Home equity lines and loans 103 11,870 761 — 11,110 11,871 Automobile 163 1,264 1,124 55 85 1,264 Other 79 1,209 968 45 196 1,209 Total 739 $ 279,696 $ 164,883 $ 4,676 $ 98,856 $ 268,415 Post-modification (a) Number Pre- modification recorded investment Principal Deferral Other Combination of Concession Types Total Year Ended December 31, 2015 (Dollars in thousands) Commercial, financial, leasing, etc. 127 $ 101,129 $ 50,807 $ 12,926 $ 31,439 $ 95,172 Real estate: Commercial 58 56,893 48,388 4,087 3,242 55,717 Residential builder and developer 2 10,650 10,598 — — 10,598 Other commercial construction 6 10,743 460 — 10,375 10,835 Residential 85 10,485 6,528 267 4,277 11,072 Residential — limited documentation 11 1,962 437 — 1,635 2,072 Consumer: Home equity lines and loans 71 7,378 2,175 — 5,204 7,379 Automobile 302 3,053 1,818 287 948 3,053 Other 155 2,507 1,995 116 396 2,507 Total 817 $ 204,800 $ 123,206 $ 17,683 $ 57,516 $ 198,405 (a) Financial effects impacting the recorded investment included principal payments or advances, charge-offs and capitalized escrow arrearages. The present value of interest rate concessions, discounted at the effective rate of the original loan, was not material. Troubled debt restructurings are considered to be impaired loans and for purposes of establishing the allowance for credit losses are evaluated for impairment giving consideration to the impact of the modified loan terms on the present value of the loan’s expected cash flows. Impairment of troubled debt restructurings that have subsequently defaulted may also be measured based on the loan’s observable market price or the fair value of collateral if the loan is collateral-dependent. Charge-offs may also be recognized on troubled debt restructurings that have subsequently defaulted. Loans that were modified as troubled debt restructurings during the twelve months ended December 31, 2017, 2016 and 2015 and for which there was a subsequent payment default during the respective year were not material. Borrowings by directors and certain officers of M&T and its banking subsidiaries, and by associates of such persons, exclusive of loans aggregating less than $60,000, amounted to $93,103,000 and $63,543,000 at December 31, 2017 and 2016, respectively. During 2017, new borrowings by such persons amounted to $88,077,000 (including any borrowings of new directors or officers that were outstanding at the time of their election) and repayments and other reductions (including reductions resulting from individuals ceasing to be directors or officers) were $58,517,000. At December 31, 2017, approximately $11.9 billion of commercial loans and leases, $12.7 billion of commercial real estate loans, $15.3 billion of one-to-four family residential real estate loans, $2.3 billion of home equity loans and lines of credit and $5.2 billion of other consumer loans were pledged to secure outstanding borrowings from the FHLB of New York and available lines of credit as described in note 9. The Company’s loan and lease portfolio includes commercial lease financing receivables consisting of direct financing and leveraged leases for machinery and equipment, railroad equipment, commercial trucks and trailers, and aircraft. A summary of lease financing receivables follows: December 31 2017 2016 (In thousands) Commercial leases: Direct financings: Lease payments receivable $ 1,159,584 $ 1,136,815 Estimated residual value of leased assets 89,666 79,449 Unearned income (110,261 ) (107,535 ) Investment in direct financings 1,138,989 1,108,729 Leveraged leases: Lease payments receivable 87,821 92,918 Estimated residual value of leased assets 88,491 110,328 Unearned income (35,792 ) (38,760 ) Investment in leveraged leases 140,520 164,486 Total investment in leases $ 1,279,509 $ 1,273,215 Deferred taxes payable arising from leveraged leases $ 81,359 $ 139,067 Included within the estimated residual value of leased assets at December 31, 2017 and 2016 were $37 million and $47 million, respectively, in residual value associated with direct financing leases that are guaranteed by the lessees or others. At December 31, 2017, the minimum future lease payments to be received from lease financings were as follows: (In thousands) Year ending December 31: 2018 $ 310,207 2019 297,599 2020 208,613 2021 150,553 2022 96,871 Later years 183,562 $ 1,247,405 The amount of foreclosed residential real estate property held by the Company was $108 million and $129 million at December 31, 2017 and 2016, respectively. There were $497 million and $506 million at December 31, 2017 and 2016, respectively, in loans secured by residential real estate that were in the process of foreclosure. Of all loans in the process of foreclosure at December 31, 2017, approximately 45% were classified as purchased impaired and 19% were government guaranteed.

Allowance for credit losses

Allowance for credit losses	12 Months Ended
Allowance for credit losses	Dec. 31, 2017
Receivables [Abstract]
Allowance for credit losses	5. Allowance for credit losses Changes in the allowance for credit losses for the years ended December 31, 2017, 2016 and 2015 were as follows: Commercial, Financial, Real Estate Leasing, etc. Commercial Residential Consumer Unallocated Total (In thousands) 2017 Beginning balance $ 330,833 362,719 61,127 156,288 78,030 $ 988,997 Provision for credit losses 41,511 6,715 16,094 103,410 270 168,000 Net charge-offs Charge-offs (64,941 ) (7,931 ) (20,799 ) (130,927 ) — (224,598 ) Recoveries 21,196 12,582 8,983 42,038 — 84,799 Net (charge-offs) recoveries (43,745 ) 4,651 (11,816 ) (88,889 ) — (139,799 ) Ending balance $ 328,599 374,085 65,405 170,809 78,300 $ 1,017,198 2016 Beginning balance $ 300,404 326,831 72,238 178,320 78,199 $ 955,992 Provision for credit losses 59,506 33,627 6,902 90,134 (169 ) 190,000 Net charge-offs Charge-offs (59,244 ) (4,805 ) (26,133 ) (141,073 ) — (231,255 ) Recoveries 30,167 7,066 8,120 28,907 — 74,260 Net (charge-offs) recoveries (29,077 ) 2,261 (18,013 ) (112,166 ) — (156,995 ) Ending balance $ 330,833 362,719 61,127 156,288 78,030 $ 988,997 2015 Beginning balance $ 288,038 307,927 61,910 186,033 75,654 $ 919,562 Provision for credit losses 43,065 25,768 19,133 79,489 2,545 170,000 Net charge-offs Charge-offs (60,983 ) (16,487 ) (13,116 ) (107,787 ) — (198,373 ) Recoveries 30,284 9,623 4,311 20,585 — 64,803 Net charge-offs (30,699 ) (6,864 ) (8,805 ) (87,202 ) — (133,570 ) Ending balance $ 300,404 326,831 72,238 178,320 78,199 $ 955,992 Despite the above allocation, the allowance for credit losses is general in nature and is available to absorb losses from any loan or lease type. In establishing the allowance for credit losses, the Company estimates losses attributable to specific troubled credits identified through both normal and targeted credit review processes and also estimates losses inherent in other loans and leases on a collective basis. For purposes of determining the level of the allowance for credit losses, the Company evaluates its loan and lease portfolio by loan type. The amounts of loss components in the Company’s loan and lease portfolios are determined through a loan-by-loan analysis of larger balance commercial loans and commercial real estate loans that are in nonaccrual status and by applying loss factors to groups of loan balances based on loan type and management’s classification of such loans under the Company’s loan grading system. Measurement of the specific loss components is typically based on expected future cash flows, collateral values and other factors that may impact the borrower’s ability to pay. In determining the allowance for credit losses, the Company utilizes a loan grading system which is applied to commercial and commercial real estate credits on an individual loan basis. Loan grades are assigned loss component factors that reflect the Company’s loss estimate for each group of loans and leases. Factors considered in assigning loan grades and loss component factors include borrower-specific information related to expected future cash flows and operating results, collateral values, geographic location, financial condition and performance, payment status, and other information; levels of and trends in portfolio charge-offs and recoveries; levels of and trends in portfolio delinquencies and impaired loans; changes in the risk profile of specific portfolios; trends in volume and terms of loans; effects of changes in credit concentrations; and observed trends and practices in the banking industry. The following tables provide information with respect to loans and leases that were considered impaired as of December 31, 2017 and 2016 and for the years ended December 31, 2017, 2016 and 2015. December 31, 2017 December 31, 2016 Recorded Investment Unpaid Principal Balance Related Allowance Recorded Investment Unpaid Principal Balance Related Allowance (In thousands) With an allowance recorded: Commercial, financial, leasing, etc. $ 177,250 194,257 45,488 168,072 184,432 48,480 Real estate: Commercial 67,199 75,084 9,140 71,862 86,666 11,620 Residential builder and developer 5,320 5,641 308 7,396 8,361 506 Other commercial construction 4,817 20,357 647 2,475 2,731 448 Residential 101,724 122,602 4,000 86,680 105,944 3,457 Residential — limited documentation 77,277 92,439 3,900 82,547 97,718 6,000 Consumer: Home equity lines and loans 48,847 53,914 8,812 44,693 48,965 8,027 Automobile 13,498 15,737 2,811 16,982 18,272 3,740 Other 3,220 5,872 656 3,791 5,296 776 499,152 585,903 75,762 484,498 558,385 83,054 With no related allowance recorded: Commercial, financial, leasing, etc. 89,126 115,327 — 100,805 124,786 — Real estate: Commercial 138,356 149,716 — 113,276 121,846 — Residential builder and developer 5,057 5,296 — 14,368 21,124 — Other commercial construction 5,456 9,130 — 15,933 35,281 — Residential 13,574 18,980 — 16,823 24,161 — Residential — limited documentation 9,588 16,138 — 15,429 24,590 — 261,157 314,587 — 276,634 351,788 — Total: Commercial, financial, leasing, etc. 266,376 309,584 45,488 268,877 309,218 48,480 Real estate: Commercial 205,555 224,800 9,140 185,138 208,512 11,620 Residential builder and developer 10,377 10,937 308 21,764 29,485 506 Other commercial construction 10,273 29,487 647 18,408 38,012 448 Residential 115,298 141,582 4,000 103,503 130,105 3,457 Residential — limited documentation 86,865 108,577 3,900 97,976 122,308 6,000 Consumer: Home equity lines and loans 48,847 53,914 8,812 44,693 48,965 8,027 Automobile 13,498 15,737 2,811 16,982 18,272 3,740 Other 3,220 5,872 656 3,791 5,296 776 Total $ 760,309 900,490 75,762 761,132 910,173 83,054 Year Ended December 31, 2017 Year Ended December 31, 2016 Interest Income Recognized Interest Income Recognized Average Recorded Investment Total Cash Basis Average Recorded Investment Total Cash Basis (In thousands) Commercial, financial, leasing, etc. $ 240,157 3,894 3,894 277,647 8,342 8,342 Real estate: Commercial 207,616 4,497 4,497 175,877 4,878 4,878 Residential builder and developer 16,209 6,419 6,419 29,237 2,300 2,300 Other commercial construction 15,142 1,001 1,001 19,697 644 644 Residential 110,646 7,177 3,406 98,394 6,227 3,154 Residential — limited documentation 93,097 5,981 1,607 103,060 5,999 1,975 Consumer: Home equity lines and loans 47,323 1,681 400 36,493 1,325 410 Automobile 15,045 1,025 81 19,636 1,242 99 Other 3,363 308 11 9,218 440 83 Total $ 748,598 31,983 21,316 769,259 31,397 21,885 Year Ended December 31, 2015 Interest Income Recognized Average Recorded Investment Total Cash Basis (In thousands) Commercial, financial, leasing, etc. $ 236,201 2,933 2,933 Real estate: Commercial 166,628 6,243 6,243 Residential builder and developer 59,457 335 335 Other commercial construction 20,276 2,311 2,311 Residential 101,483 6,188 4,037 Residential — 118,449 6,380 2,638 Consumer: Home equity lines and loans 21,523 905 261 Automobile 25,675 1,619 175 Other 18,809 729 113 Total $ 768,501 27,643 19,046 Commercial loans and commercial real estate loans with a lower expectation of default are assigned one of ten possible “pass” loan grades and are generally ascribed lower loss factors when determining the allowance for credit losses. Loans with an elevated level of credit risk are classified as “criticized” and are ascribed a higher loss factor when determining the allowance for credit losses. Criticized loans may be classified as “nonaccrual” if the Company no longer expects to collect all amounts according to the contractual terms of the loan agreement or the loan is delinquent 90 days or more. Furthermore, criticized nonaccrual commercial loans and commercial real estate loans are considered impaired and, as a result, specific loss allowances on such loans are established within the allowance for credit losses to the extent appropriate in each individual instance. The following table summarizes the loan grades applied to the various classes of the Company’s commercial loans and commercial real estate loans. Real Estate Commercial, Residential Other Financial, Builder and Commercial Leasing, etc. Commercial Developer Construction (In thousands) December 31, 2017 Pass $ 20,490,486 24,380,184 1,485,148 6,270,812 Criticized accrual 1,011,174 723,777 140,119 164,812 Criticized nonaccrual 240,991 184,982 6,451 10,088 Total $ 21,742,651 25,288,943 1,631,718 6,445,712 December 31, 2016 Pass $ 21,398,581 24,570,269 1,789,071 5,912,351 Criticized accrual 950,032 741,274 116,548 165,862 Criticized nonaccrual 261,434 176,201 16,707 18,111 Total $ 22,610,047 25,487,744 1,922,326 6,096,324 In determining the allowance for credit losses, residential real estate loans and consumer loans are generally evaluated collectively after considering such factors as payment performance and recent loss experience and trends, which are mainly driven by current collateral values in the market place as well as the amount of loan defaults. Loss rates on such loans are determined by reference to recent charge-off history and are evaluated (and adjusted if deemed appropriate) through consideration of other factors including near-term forecasted loss estimates developed by the Company’s credit department. In arriving at such forecasts, the Company considers the current estimated fair value of its collateral based on geographical adjustments for home price depreciation/appreciation and overall borrower repayment performance. With regard to collateral values, the realizability of such values by the Company contemplates repayment of any first lien position prior to recovering amounts on a second lien position. However, residential real estate loans and outstanding balances of home equity loans and lines of credit that are more than 150 days past due are generally evaluated for collectibility on a loan-by-loan basis giving consideration to estimated collateral values. The carrying value of residential real estate loans and home equity loans and lines of credit for which a partial charge-off has been recognized aggregated $34 million and $25 million, respectively, at December 31, 2017 and $44 million and $32 million, respectively, at December 31, 2016. Residential real estate loans and home equity loans and lines of credit that were more than 150 days past due but did not require a partial charge-off because the net realizable value of the collateral exceeded the outstanding customer balance totaled $20 million and $32 million, respectively, at December 31, 2017 and $16 million and $39 million, respectively, at December 31, 2016. The Company also measures additional losses for purchased impaired loans when it is probable that the Company will be unable to collect all cash flows expected at acquisition plus additional cash flows expected to be collected arising from changes in estimates after acquisition. Given the inherent subjectivity and potential imprecision involved in determining the allocated portion of the allowance for credit losses, the Company also provides an inherent unallocated portion of the allowance. The unallocated portion of the allowance is intended to recognize probable losses that are not otherwise identifiable and includes management’s subjective determination of amounts necessary to provide for the possible use of imprecise estimates in determining the allocated portion of the allowance. Therefore, the level of the unallocated portion of the allowance is primarily reflective of the inherent imprecision in the various calculations used in determining the allocated portion of the allowance for credit losses. Other factors that could also lead to changes in the unallocated portion include the effects of expansion into new markets for which the Company does not have the same degree of familiarity and experience regarding portfolio performance in changing market conditions, the introduction of new loan and lease product types, and other risks associated with the Company’s loan portfolio that may not be specifically identifiable. The allocation of the allowance for credit losses summarized on the basis of the Company’s impairment methodology was as follows: Commercial, Financial, Real Estate Leasing, etc. Commercial Residential Consumer Total (In thousands) December 31, 2017 Individually evaluated for impairment $ 45,488 10,095 7,900 12,279 $ 75,762 Collectively evaluated for impairment 283,111 363,990 47,645 158,530 853,276 Purchased impaired — — 9,860 — 9,860 Allocated $ 328,599 374,085 65,405 170,809 938,898 Unallocated 78,300 Total $ 1,017,198 December 31, 2016 Individually evaluated for impairment $ 48,480 12,500 9,457 12,543 $ 82,980 Collectively evaluated for impairment 282,353 348,301 47,993 143,745 822,392 Purchased impaired — 1,918 3,677 — 5,595 Allocated $ 330,833 362,719 61,127 156,288 910,967 Unallocated 78,030 Total $ 988,997 The recorded investment in loans and leases summarized on the basis of the Company’s impairment methodology was as follows: Commercial, Financial, Real Estate Leasing, etc. Commercial Residential Consumer Total (In thousands) December 31, 2017 Individually evaluated for impairment $ 266,376 226,205 202,163 65,565 $ 760,309 Collectively evaluated for impairment 21,476,254 33,117,512 19,023,843 13,201,050 86,818,659 Purchased impaired 21 22,656 387,338 — 410,015 Total $ 21,742,651 33,366,373 19,613,344 13,266,615 $ 87,988,983 December 31, 2016 Individually evaluated for impairment $ 268,877 224,630 201,479 65,466 $ 760,452 Collectively evaluated for impairment 22,340,529 33,222,080 21,871,726 12,080,597 89,514,932 Purchased impaired 641 59,684 517,707 — 578,032 Total $ 22,610,047 33,506,394 22,590,912 12,146,063 $ 90,853,416

Premises and equipment

Premises and equipment	12 Months Ended
Premises and equipment	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Premises and equipment	6. Premises and equipment The detail of premises and equipment was as follows: December 31 2017 2016 (In thousands) Land $ 98,077 $ 104,671 Buildings 454,610 448,442 Leasehold improvements 239,956 232,936 Furniture and equipment — owned 676,665 636,219 Furniture and equipment — capital leases 18,039 14,849 1,487,347 1,437,117 Less: accumulated depreciation and amortization Owned assets 830,832 756,245 Capital leases 10,064 5,609 840,896 761,854 Premises and equipment, net $ 646,451 $ 675,263 Net lease expense for all operating leases totaled $114,362,000 in 2017, $113,663,000 in 2016 and $102,356,000 in 2015. Minimum lease payments under noncancelable operating leases are presented in note 21. Minimum lease payments required under capital leases are not material.

Capitalized servicing assets

Capitalized servicing assets	12 Months Ended
Capitalized servicing assets	Dec. 31, 2017
Transfers And Servicing [Abstract]
Capitalized servicing assets	7. Capitalized servicing assets Changes in capitalized servicing assets were as follows: Residential Mortgage Loans Commercial Mortgage Loans For the Year Ended December 31, 2017 2016 2015 2017 2016 2015 (In thousands) Beginning balance $ 117,351 $ 118,303 $ 109,871 $ 103,764 $ 83,692 $ 72,939 Originations 28,792 28,618 35,556 34,620 40,117 29,914 Purchases 699 638 243 — — — Amortization (31,864 ) (30,208 ) (27,367 ) (24,308 ) (20,045 ) (19,161 ) 114,978 117,351 118,303 114,076 103,764 83,692 Valuation allowance — — — — — — Ending balance, net $ 114,978 $ 117,351 $ 118,303 $ 114,076 $ 103,764 $ 83,692 Other Total For the Year Ended December 31, 2017 2016 2015 2017 2016 2015 (In thousands) Beginning balance $ — $ 729 $ 4,107 $ 221,115 $ 202,724 $ 186,917 Originations — — — 63,412 68,735 65,470 Purchases — — — 699 638 243 Amortization — (729 ) (3,378 ) (56,172 ) (50,982 ) (49,906 ) — — 729 229,054 221,115 202,724 Valuation allowance — — — — — — Ending balance, net $ — $ — $ 729 $ 229,054 $ 221,115 $ 202,724 Residential mortgage loans serviced for others were $22.6 billion at December 31, 2017, $22.8 billion at December 31, 2016 and $23.9 billion at December 31, 2015. Excluded from residential mortgage loans serviced for others were loans sub-serviced for others of $56.6 billion, $30.4 billion and $37.8 billion at December 31, 2017, 2016, and 2015, respectively. Commercial mortgage loans serviced for others were $13.6 billion at December 31, 2017, $11.8 billion at December 31, 2016 and $11.0 billion at December 31, 2015. Excluded from commercial mortgage loans serviced for others were loans sub-serviced for others of $2.6 billion at December 31, 2017. The estimated fair value of capitalized residential mortgage loan servicing assets was approximately $234 million at December 31, 2017 and $235 million at December 31, 2016. The fair value of capitalized residential mortgage loan servicing assets was estimated using weighted-average discount rates of 12.2% at each of December 31, 2017 and 2016 and contemporaneous prepayment assumptions that vary by loan type. At December 31, 2017 and 2016, the discount rate represented a weighted-average option-adjusted spread (“OAS”) of 1,067 basis points (hundredths of one percent) and 1,095 basis points, respectively, over market implied forward London Interbank Offered Rates (“LIBOR”). The estimated fair value of capitalized residential mortgage loan servicing rights may vary significantly in subsequent periods due to changing interest rates and the effect thereof on prepayment speeds. The estimated fair value of capitalized commercial mortgage loan servicing assets was approximately $132 million and $119 million at December 31, 2017 and 2016, respectively. An 18% discount rate was used to estimate the fair value of capitalized commercial mortgage loan servicing rights at December 31, 2017 and 2016 with no prepayment assumptions because, in general, the servicing agreements allow the Company to share in customer loan prepayment fees and thereby recover the remaining carrying value of the capitalized servicing rights associated with such loan. The Company’s ability to realize the carrying value of capitalized commercial mortgage servicing rights is more dependent on the borrowers’ abilities to repay the underlying loans than on prepayments or changes in interest rates. The key economic assumptions used to determine the fair value of significant portfolios of capitalized servicing rights at December 31, 2017 and the sensitivity of such value to changes in those assumptions are summarized in the table that follows. Those calculated sensitivities are hypothetical and actual changes in the fair value of capitalized servicing rights may differ significantly from the amounts presented herein. The effect of a variation in a particular assumption on the fair value of the servicing rights is calculated without changing any other assumption. In reality, changes in one factor may result in changes in another which may magnify or counteract the sensitivities. The changes in assumptions are presumed to be instantaneous. Residential Commercial Weighted-average prepayment speeds 12.16 % Impact on fair value of 10% adverse change $ (8,935,000 ) Impact on fair value of 20% adverse change (17,159,000 ) Weighted-average OAS 10.67 % Impact on fair value of 10% adverse change $ (6,838,000 ) Impact on fair value of 20% adverse change (13,267,000 ) Weighted-average discount rate 18.00 % Impact on fair value of 10% adverse change $ (5,885,000 ) Impact on fair value of 20% adverse change (11,342,000 )

Goodwill and other intangible a

Goodwill and other intangible assets	12 Months Ended
Goodwill and other intangible assets	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and other intangible assets	8. Goodwill and other intangible assets In accordance with GAAP, the Company does not amortize goodwill, however, core deposit and other intangible assets are amortized over the estimated life of each respective asset. Total amortizing intangible assets were comprised of the following: Gross Carrying Amount Accumulated Amortization Net Carrying Amount (In thousands) December 31, 2017 Core deposit $ 887,459 $ 820,110 $ 67,349 Other 182,568 178,328 4,240 Total $ 1,070,027 $ 998,438 $ 71,589 December 31, 2016 Core deposit $ 887,459 $ 789,988 $ 97,471 Other 177,268 177,084 184 Total $ 1,064,727 $ 967,072 $ 97,655 Amortization of core deposit and other intangible assets was generally computed using accelerated methods over original amortization periods of five to ten years. The weighted-average original amortization period was approximately eight years. Amortization expense for core deposit and other intangible assets was $31,366,000, $42,613,000 and $26,424,000 for the years ended December 31, 2017, 2016 and 2015, respectively. Estimated amortization expense in future years for such intangible assets is as follows: (In thousands) Year ending December 31: 2018 $ 24,522 2019 19,086 2020 14,383 2021 9,681 2022 3,917 $ 71,589 In accordance with GAAP, the Company completed annual goodwill impairment tests as of October 1, 2017, 2016 and 2015. For purposes of testing for impairment, the Company assigned all recorded goodwill to the reporting units originally intended to benefit from past business combinations, which has historically been the Company’s core relationship business reporting units. Goodwill was generally assigned based on the implied fair value of the acquired goodwill applicable to the benefited reporting units at the time of each respective acquisition. The implied fair value of the goodwill was determined as the difference between the estimated incremental overall fair value of the reporting unit and the estimated fair value of the net assets assigned to the reporting unit as of each respective acquisition date. To test for goodwill impairment at each evaluation date, the Company compared the estimated fair value of each of its reporting units to their respective carrying amounts and certain other assets and liabilities assigned to the reporting unit, including goodwill and core deposit and other intangible assets. The methodologies used to estimate fair values of reporting units as of the acquisition dates and as of the evaluation dates were similar. For the Company’s core customer relationship business reporting units, fair value was estimated as the present value of the expected future cash flows of the reporting unit. Based on the results of the goodwill impairment tests, the Company concluded that the amount of recorded goodwill was not impaired at the respective testing dates. A summary of goodwill assigned to each of the Company’s reportable segments as of December 31, 2017 and 2016 for purposes of testing for impairment is as follows: (In thousands) Business Banking $ 864,366 Commercial Banking 1,401,873 Commercial Real Estate 654,389 Discretionary Portfolio — Residential Mortgage Banking — Retail Banking 1,309,191 All Other 363,293 Total $ 4,593,112

Borrowings

Borrowings	12 Months Ended
Borrowings	Dec. 31, 2017
Debt Disclosure [Abstract]
Borrowings	9. Borrowings The amounts and interest rates of short-term borrowings were as follows: Federal Funds Purchased and Repurchase Agreements Other Short-term Borrowings Total (Dollars in thousands) At December 31, 2017 Amount outstanding $ 175,099 $ — $ 175,099 Weighted-average interest rate 0.92 % — 0.92 % For the year ended December 31, 2017 Highest amount at a month-end $ 204,977 $ 1,500,000 Daily-average amount outstanding 188,459 16,164 $ 204,623 Weighted-average interest rate 0.69 % 1.27 % 0.74 % At December 31, 2016 Amount outstanding $ 163,442 $ — $ 163,442 Weighted-average interest rate 0.32 % — 0.32 % For the year ended December 31, 2016 Highest amount at a month-end $ 225,940 $ 1,974,013 Daily-average amount outstanding 203,853 689,969 $ 893,822 Weighted-average interest rate 0.28 % 0.44 % 0.41 % At December 31, 2015 Amount outstanding $ 150,546 $ 1,981,636 $ 2,132,182 Weighted-average interest rate 0.06 % 0.43 % 0.40 % For the year ended December 31, 2015 Highest amount at a month-end $ 202,951 $ 1,989,257 Daily-average amount outstanding 187,167 360,838 $ 548,005 Weighted-average interest rate 0.08 % 0.43 % 0.31 % Short-term borrowings have a stated maturity of one year or less at the date the Company enters into the obligation. In general, federal funds purchased and short-term repurchase agreements outstanding at December 31, 2017 matured on the next business day following year-end. Other short-term borrowings at December 31, 2015 represent borrowings from the FHLB of New York that were assumed in the acquisition of Hudson City. Those borrowings matured at various dates during 2016. At December 31, 2017, M&T Bank had lines of credit under formal agreements as follows: (In thousands) Outstanding borrowings $ 576,954 Unused 31,624,206 At December 31, 2017, M&T Bank had borrowing facilities available with the FHLBs whereby M&T Bank could borrow up to approximately $20.2 billion. Additionally, M&T Bank had an available line of credit with the Federal Reserve Bank of New York totaling approximately $12.0 billion at December 31, 2017. M&T Bank is required to pledge loans and investment securities as collateral for these borrowing facilities. Long-term borrowings were as follows: December 31, 2017 2016 (In thousands) Senior notes of M&T Bank: Variable rate due 2017 $ — $ 550,000 Variable rate due 2022 249,558 — 1.25% due 2017 — 499,999 1.40% due 2017 — 749,946 1.45% due 2018 499,907 501,829 2.25% due 2019 644,977 649,012 2.30% due 2019 746,919 749,473 2.10% due 2020 743,788 749,735 2.05% due 2020 739,961 — 2.50% due 2022 638,872 — 2.90% due 2025 749,404 749,320 Advances from FHLB: Fixed rates 576,876 1,154,737 Agreements to repurchase securities 421,771 1,084,694 Subordinated notes of Wilmington Trust Corporation (a wholly owned subsidiary of M&T): 8.50% due 2018 200,000 207,651 Subordinated notes of M&T Bank: 6.625% due 2017 — 409,526 5.585% due 2020, variable rate commenced 2015 409,361 409,361 5.629% due 2021, variable rate commenced 2016 500,000 500,000 3.40% due 2027 491,176 — Junior subordinated debentures of M&T associated with preferred capital securities: Fixed rates: BSB Capital Trust I — 8.125%, due 2028 15,682 15,659 Provident Trust I — 8.29%, due 2028 26,847 26,293 Southern Financial Statutory Trust I — 10.60%, due 2030 6,664 6,620 Variable rates: First Maryland Capital I — due 2027 146,794 146,256 First Maryland Capital II — due 2027 148,617 147,954 Allfirst Asset Trust — due 2029 96,640 96,494 BSB Capital Trust III — due 2033 15,464 15,464 Provident Statutory Trust III — due 2033 54,466 53,834 Southern Financial Capital Trust III — due 2033 8,051 7,968 Other 9,635 12,010 $ 8,141,430 $ 9,493,835 The variable rate senior notes of M&T Bank pay interest quarterly at rates that are indexed to the three-month LIBOR. The contractual interest rates for those notes were 2.05% at December 31, 2017 and ranged from 1.18% to 1.26% at December 31, 2016. The weighted-average contractual interest rate was Long-term fixed rate advances from the FHLB had contractual interest rates ranging from 1.97% to 5.98% at December 31, 2017 and from 1.17% to 7.32% at December 31, 2016. The weighted-average contractual interest rate was 2.06% at December 31, 2017 and 1.65% at December 31, 2016. Advances from the FHLB mature at various dates through 2035 and are secured by residential real estate loans, commercial real estate loans and investment securities. Long-term agreements to repurchase securities had contractual interest rates that ranged from 4.09% to 4.58% at December 31, 2017 and from 3.65% to 4.58% at December 31, 2016. The weighted-average contractual interest rates payable were 4.31% at December 31, 2017 and 4.05% at December 31, 2016. The agreements reflect various repurchase dates through 2020, however, the contractual maturities of the underlying investment securities extend beyond such repurchase dates. The agreements are subject to legally enforceable master netting arrangements, however, the Company has not offset any amounts related to these agreements in its consolidated financial statements. The Company posted collateral consisting primarily of government guaranteed mortgage-backed securities of $442 million and $1.1 billion at December 31, 2017 and 2016, respectively. The subordinated notes of M&T Bank and Wilmington Trust Corporation are unsecured and are subordinate to the claims of other creditors of those entities. The subordinated notes of M&T Bank that mature in 2020 converted to variable rate notes in December 2015. These notes now pay interest monthly at a rate that is indexed to the one-month LIBOR. The contractual interest rates were 2.78% and 1.97% at December 31, 2017 and 2016, respectively. The subordinated notes of M&T Bank that mature in 2021 converted to variable rate notes in December 2016. Those notes now pay interest quarterly at a rate that is indexed to the three-month LIBOR. The contractual interest rate was 2.12% at December 31, 2017 and 1.57% at December 31, 2016. The fixed and variable rate junior subordinated deferrable interest debentures of M&T (“Junior Subordinated Debentures”) are held by various trusts and were issued in connection with the issuance by those trusts of preferred capital securities (“Capital Securities”) and common securities (“Common Securities”). The proceeds from the issuances of the Capital Securities and the Common Securities were used by the trusts to purchase the Junior Subordinated Debentures. The Common Securities of each of those trusts are wholly owned by M&T and are the only class of each trust’s securities possessing general voting powers. The Capital Securities represent preferred undivided interests in the assets of the corresponding trust. Under the Federal Reserve Board’s risk-based capital guidelines, the Capital Securities qualify for inclusion in Tier 2 regulatory capital. The variable rate Junior Subordinated Debentures pay interest quarterly at rates that are indexed to the three-month LIBOR. Those rates ranged from 2.23% to 4.71% at December 31, 2017 and from 1.74% to 4.23% at December 31, 2016. The weighted-average variable rates payable on those Junior Subordinated Debentures were 2.83% at December 31, 2017 and 2.33% at December 31, 2016. Holders of the Capital Securities receive preferential cumulative cash distributions unless M&T exercises its right to extend the payment of interest on the Junior Subordinated Debentures as allowed by the terms of each such debenture, in which case payment of distributions on the respective Capital Securities will be deferred for comparable periods. During an extended interest period, M&T may not pay dividends or distributions on, or repurchase, redeem or acquire any shares of its capital stock. In general, the agreements governing the Capital Securities, in the aggregate, provide a full, irrevocable and unconditional guarantee by M&T of the payment of distributions on, the redemption of, and any liquidation distribution with respect to the Capital Securities. The obligations under such guarantee and the Capital Securities are subordinate and junior in right of payment to all senior indebtedness of M&T. The Capital Securities will remain outstanding until the Junior Subordinated Debentures are repaid at maturity, are redeemed prior to maturity or are distributed in liquidation to the trusts. The Capital Securities are mandatorily redeemable in whole, but not in part, upon repayment at the stated maturity dates (ranging from 2027 to 2033) of the Junior Subordinated Debentures or the earlier redemption of the Junior Subordinated Debentures in whole upon the occurrence of one or more events set forth in the indentures relating to the Capital Securities, and in whole or in part at any time after an optional redemption prior to contractual maturity contemporaneously with the optional redemption of the related Junior Subordinated Debentures in whole or in part, subject to possible regulatory approval. Long-term borrowings at December 31, 2017 mature as follows: (In thousands) Year ending December 31: 2018 $ 701,256 2019 2,282,016 2020 2,005,383 2021 502,487 2022 888,430 Later years 1,761,858 $ 8,141,430

Shareholders' equity

Shareholders' equity	12 Months Ended
Shareholders' equity	Dec. 31, 2017
Equity [Abstract]
Shareholders' equity	10. Shareholders’ equity M&T is authorized to issue 1,000,000 shares of preferred stock with a $1.00 par value per share. Preferred shares outstanding rank senior to common shares both as to dividends and liquidation preference, but have no general voting rights. Issued and outstanding preferred stock of M&T as of December 31, 2017 and 2016 is presented below: Shares Issued and Outstanding Carrying Value (Dollars in thousands) Series A (a) Fixed Rate Cumulative Perpetual Preferred Stock, $1,000 liquidation preference per share 230,000 $ 230,000 Series C (a) Fixed Rate Cumulative Perpetual Preferred Stock, $1,000 liquidation preference per share 151,500 $ 151,500 Series E (b) Fixed-to-Floating Rate Non-cumulative Perpetual Preferred Stock, $1,000 liquidation preference per share 350,000 $ 350,000 Series F (c) Fixed-to-Floating Rate Non-cumulative Perpetual Preferred Stock, $10,000 liquidation preference per share 50,000 $ 500,000 (a) Dividends, if declared, are paid at 6.375%. Warrants to purchase M&T common stock at $73.77 per share issued in connection with the Series A preferred stock expire December 23, 2018 and totaled 257,008 at December 31, 2017. (b) Dividends, if declared, are paid semi-annually at a rate of 6.45% through February 14, 2024 and thereafter will be paid quarterly at a rate of the three-month LIBOR plus 361 basis points. The shares are redeemable in whole or in part on or after February 15, 2024. Notwithstanding M&T’s option to redeem the shares, if an event occurs such that the shares no longer qualify as Tier 1 capital, M&T may redeem all of the shares within 90 days following that occurrence. (c) Dividends, if declared, are paid semi-annually at a rate of 5.125% through October 31, 2026 and thereafter will be paid quarterly at a rate of the three-month LIBOR plus 352 basis points. The shares are redeemable in whole or in part on or after November 1, 2026. Notwithstanding M&T’s option to redeem the shares, if an event occurs such that the shares no longer qualify as Tier 1 capital, M&T may redeem all of the shares within 90 days following that occurrence. In addition to the Series A warrants, a warrant to purchase 95,500 shares of M&T common stock at $518.32 per share was outstanding at December 31, 2017. The obligation under that warrant was assumed by M&T in an acquisition and expires on December 12, 2018.

Stock-based compensation plans

Stock-based compensation plans	12 Months Ended
Stock-based compensation plans	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based compensation plans	11. Stock-based compensation plans Stock-based compensation expense was $61 million in 2017, $65 million in 2016 and $67 million in 2015. The Company recognized income tax benefits related to stock-based compensation of $35 million in 2017, $31 million in 2016 and $29 million in The Company’s equity incentive compensation plan allows for the issuance of various forms of stock-based compensation, including stock options, restricted stock, restricted stock units and performance-based awards. At December 31, 2017 and 2016, respectively, there were 3,278,036 and 3,667,800 shares available for future grant under the Company’s equity incentive compensation plan. Restricted stock awards Restricted stock awards are comprised of restricted stock and restricted stock units. Restricted stock awards granted since 2014 vest over three years. Restricted stock awards granted prior to 2014 vested over four years. A portion of restricted stock awards granted after 2013 require a performance condition to be met before such awards vest. Unrecognized compensation expense associated with restricted stock was $15 million as of December 31, 2017 and is expected to be recognized over a weighted-average period of approximately one year. The Company may issue restricted shares from treasury stock to the extent available or issue new shares. The number of restricted shares issued was 181,939 in 2017, 218,341 in 2016 and 218,183 in 2015, with a weighted-average grant date fair value of $29,557,000 in 2017, $24,085,000 in 2016 and $24,726,000 in 2015. Unrecognized compensation expense associated with restricted stock units was $6 million as of December 31, 2017 and is expected to be recognized over a weighted-average period of approximately one year. The number of restricted stock units issued was 235,983 in 2017, 348,297 in 2016 and 324,772 in 2015, with a weighted-average grant date fair value of $38,364,000, $38,795,000 and $37,070,000, respectively. A summary of restricted stock and restricted stock unit activity follows: Restricted Stock Units Outstanding Weighted- Average Grant Price Restricted Stock Outstanding Weighted- Average Grant Price Unvested at January 1, 2017 739,350 $ 111.21 499,324 $ 109.92 Granted 235,983 162.57 181,939 162.46 Vested (481,002 ) 114.06 (290,935 ) 108.97 Cancelled (11,774 ) 129.15 (16,584 ) 128.64 Unvested at December 31, 2017 482,557 $ 133.05 373,744 $ 135.41 Stock option awards Stock options issued generally vested over four years and are exercisable over terms not exceeding ten years and one day. The Company used an option pricing model to estimate the grant date present value of stock options granted. Stock options granted in 2017, 2016 and 2015 were not significant. A summary of stock option activity follows: Weighted-Average Stock Options Outstanding Exercise Price Life (In Years) Aggregate Intrinsic Value (In thousands) Outstanding at January 1, 2017 1,594,591 $ 139.60 Granted 200 162.57 Exercised (658,400 ) 116.20 Expired (270,979 ) 165.46 Outstanding at December 31, 2017 665,412 $ 152.23 0.8 $ 18,086 Exercisable at December 31, 2017 665,010 $ 152.23 0.8 $ 18,072 For 2017, 2016 and 2015, M&T received $72 million, $172 million and $93 million, respectively, in cash and realized tax benefits from the exercise of stock options of $10 million, $15 million and $6 million, respectively. The intrinsic value of stock options exercised during those periods was $31 million, $42 million and $17 million, respectively. As of December 31, 2017, the amount of unrecognized compensation cost related to non-vested stock options was not significant. The total grant date fair value of stock options vested during 2017, 2016 and 2015 was not significant. Upon the exercise of stock options, the Company may issue shares from treasury stock to the extent available or issue new shares. Stock purchase plan The stock purchase plan provides eligible employees of the Company with the right to purchase shares of M&T common stock at a discount through accumulated payroll deductions. In connection with the employee stock purchase plan, 2,500,000 shares of M&T common stock were authorized for issuance under a plan adopted in 2013. There were 66,504 shares issued in 2017, 97,880 shares issued in 2016 and 89,384 shares issued in 2015. For 2017, 2016 and 2015, M&T received $9,730,000, $9,528,000 and $9,296,000, respectively, in cash for shares purchased through the employee stock purchase plan. Compensation expense recognized for the stock purchase plan was not significant in 2017, 2016 or 2015. Deferred bonus plan The Company provided a deferred bonus plan pursuant to which eligible employees could elect to defer all or a portion of their annual incentive compensation awards and allocate such awards to several investment options, including M&T common stock. Participants could elect the timing of distributions from the plan. Such distributions are payable in cash with the exception of balances allocated to M&T common stock which are distributable in the form of M&T common stock. Shares of M&T common stock distributable pursuant to the terms of the deferred bonus plan were 19,633 and 23,188 at December 31, 2017 and 2016, respectively. The obligation to issue shares is included in “common stock issuable” in the consolidated balance sheet. Directors’ stock plan The Company maintains a compensation plan for non-employee members of the Company’s boards of directors and directors advisory councils that allows such members to receive all or a portion of their compensation in shares of M&T common stock. Through December 31, 2017, 255,816 shares had been issued in connection with the directors’ stock plan. Through acquisitions, the Company assumed obligations to issue shares of M&T common stock related to deferred directors compensation plans. Shares of common stock issuable under such plans were 7,505 and 9,215 at December 31, 2017 and 2016, respectively. The obligation to issue shares is included in “common stock issuable” in the consolidated balance sheet.

Pension plans and other postret

Pension plans and other postretirement benefits	12 Months Ended
Pension plans and other postretirement benefits	Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
Pension plans and other postretirement benefits	12. Pension plans and other postretirement benefits The Company provides defined benefit pension and other postretirement benefits (including health care and life insurance benefits) to qualified retired employees. The Company uses a December 31 measurement date for all of its plans. Net periodic pension expense for defined benefit plans consisted of the following: Year Ended December 31 2017 2016 2015 (In thousands) Service cost $ 20,193 $ 25,037 $ 24,372 Interest cost on benefit obligation 79,270 83,410 72,731 Expected return on plan assets (108,524 ) (108,473 ) (96,155 ) Amortization of prior service cost (credit) 557 (3,228 ) (6,005 ) Recognized net actuarial loss 29,263 30,145 44,825 Net periodic pension expense $ 20,759 $ 26,891 $ 39,768 Net other postretirement benefits expense for defined benefit plans consisted of the following: Year Ended December 31 2017 2016 2015 (In thousands) Service cost $ 1,172 $ 1,595 $ 914 Interest cost on benefit obligation 3,716 4,971 2,995 Amortization of prior service credit (1,359 ) (1,359 ) (1,359 ) Recognized net actuarial (gain) loss (988 ) 60 106 Net other postretirement benefits expense $ 2,541 $ 5,267 $ 2,656 Data relating to the funding position of the defined benefit plans were as follows: Pension Benefits Other Postretirement Benefits 2017 2016 2017 2016 (In thousands) Change in benefit obligation: Benefit obligation at beginning of year $ 2,007,158 $ 2,004,531 $ 109,922 $ 121,497 Service cost 20,193 25,037 1,172 1,595 Interest cost 79,270 83,410 3,716 4,971 Plan participants’ contributions — — 2,929 3,085 Amendments and curtailments — (28,308 ) (30,088 ) — Actuarial (gain) loss 172,180 4,827 (8,511 ) (10,553 ) Medicare Part D reimbursement — — 630 592 Benefits paid (90,065 ) (82,339 ) (11,133 ) (11,265 ) Benefit obligation at end of year 2,188,736 2,007,158 68,637 109,922 Change in plan assets: Fair value of plan assets at beginning of year 1,642,131 1,625,134 — — Actual return on plan assets 251,381 88,564 — — Employer contributions 211,444 10,772 7,574 7,588 Plan participants’ contributions — — 2,929 3,085 Medicare Part D reimbursement — — 630 592 Benefits paid (90,065 ) (82,339 ) (11,133 ) (11,265 ) Fair value of plan assets at end of year 2,014,891 1,642,131 — — Funded status $ (173,845 ) $ (365,027 ) $ (68,637 ) $ (109,922 ) Accrued liabilities recognized in the consolidated balance sheet $ (173,845 ) $ (365,027 ) $ (68,637 ) $ (109,922 ) Amounts recognized in accumulated other comprehensive income (“AOCI”) were: Net loss (gain) $ 460,622 $ 460,562 $ (13,936 ) $ (6,413 ) Net prior service cost (credit) 2,948 3,505 (36,466 ) (7,737 ) Pre-tax adjustment to AOCI 463,570 464,067 (50,402 ) (14,150 ) Taxes (121,873 ) (182,611 ) 13,251 5,568 Net adjustment to AOCI $ 341,697 $ 281,456 $ (37,151 ) $ (8,582 ) The Company has an unfunded supplemental pension plan for certain key executives and others. The projected benefit obligation and accumulated benefit obligation included in the preceding data related to such plan were $165,210,000 as of December 31, 2017 and $160,433,000 as of December 31, 2016. The accumulated benefit obligation for all defined benefit pension plans was $2,158,601,000 and $1,979,225,000 at December 31, 2017 and 2016, respectively. GAAP requires an employer to recognize in its balance sheet as an asset or liability the overfunded or underfunded status of a defined benefit postretirement plan, measured as the difference between the fair value of plan assets and the benefit obligation. For a pension plan, the benefit obligation is the projected benefit obligation; for any other postretirement benefit plan, such as a retiree health care plan, the benefit obligation is the accumulated postretirement benefit obligation. Gains or losses and prior service costs or credits that arise during the period, but are not included as components of net periodic benefit expense, are recognized as a component of other comprehensive income. Amortization of net gains and losses is included in annual net periodic benefit expense if, as of the beginning of the year, the net gain or loss exceeds 10% of the greater of the benefit obligation or the fair value of the plan assets. As indicated in the preceding table, as of December 31, 2017 the Company recorded a minimum liability adjustment of $413,168,000 ($463,570,000 related to pension plans and $(50,402,000) related to other postretirement benefits) with a corresponding reduction of shareholders’ equity, net of applicable deferred taxes, of $304,546,000. In aggregate, the benefit plans realized a net gain during 2017 that allowed the Company to decrease its minimum liability adjustment from that which was recorded at December 31, 2016 by $36,749,000. Pension Plans Other Postretirement Benefit Plans Total (In thousands) 2017 Net loss (gain) $ 29,323 $ (8,511 ) $ 20,812 Amendments and curtailments — (30,088 ) (30,088 ) Amortization of prior service (cost) credit (557 ) 1,359 802 Amortization of actuarial (loss) gain (29,263 ) 988 (28,275 ) Total recognized in other comprehensive income, pre-tax $ (497 ) $ (36,252 ) $ (36,749 ) 2016 Net loss (gain) $ 24,736 $ (10,553 ) $ 14,183 Amendments and curtailments (28,308 ) — (28,308 ) Amortization of prior service credit 3,228 1,359 4,587 Amortization of actuarial loss (30,145 ) (60 ) (30,205 ) Total recognized in other comprehensive income, pre-tax $ (30,489 ) $ (9,254 ) $ (39,743 ) The following table reflects the amortization of amounts in accumulated other comprehensive income expected to be recognized as components of net periodic benefit expense during 2018: Pension Plans Other Postretirement Benefit Plans (In thousands) Amortization of net prior service cost (credit) $ 557 $ (4,729 ) Amortization of net loss (gain) 44,416 (830 ) The Company also provides a qualified defined contribution pension plan to eligible employees who were not participants in the defined benefit pension plan as of December 31, 2005 and to other employees who have elected to participate in the defined contribution plan. The Company makes contributions to the defined contribution plan each year in an amount that is based on an individual participant’s total compensation (generally defined as total wages, incentive compensation, commissions and bonuses) and years of service. Participants do not contribute to the defined contribution pension plan. Pension expense recorded in 2017, 2016 and 2015 associated with the defined contribution pension plan was approximately $30 million, $25 million and $23 million, respectively. Assumptions The assumed weighted-average rates used to determine benefit obligations at December 31 were: Pension Benefits Other Postretirement Benefits 2017 2016 2017 2016 Discount rate 3.50 % 4.00 % 3.50 % 4.00 % Rate of increase in future compensation levels 4.33 % 4.39 % — — The assumed weighted-average rates used to determine net benefit expense for the years ended December 31 were: Pension Benefits Other Postretirement Benefits 2017 2016 2015 2017 2016 2015 Discount rate 4.00 % 4.25 % 4.00 % 4.00 % 4.25 % 4.00 % Long-term rate of return on plan assets 6.50 % 6.50 % 6.50 % — — — Rate of increase in future compensation levels 4.39 % 4.37 % 4.39 % — — — The discount rate used by the Company to determine the present value of the Company’s future benefit obligations reflects specific market yields for a hypothetical portfolio of highly rated corporate bonds that would produce cash flows similar to the Company’s benefit plan obligations and the level of market interest rates in general as of the year-end. The expected long-term rate of return assumption as of each measurement date was developed through analysis of historical market returns, current market conditions, anticipated future asset allocations, the funds’ past experience, and expectations on potential future market returns. The expected rate of return assumption represents a long-term average view of the performance of the plan assets, a return that may or may not be achieved during any one calendar year. The company’s defined benefit pension plan is sensitive to the long-term rate of return on plan assets and the discount rate. To demonstrate the sensitivity of pension expense to changes in these assumptions, with all other assumptions held constant, 25 basis point increases in: the rate of return on plan assets would have resulted in a decrease in pension expense of approximately $4 million; and the discount rate would have resulted in a decrease in pension expense of approximately $7 million. Decreases of 25 basis points in those assumptions would have resulted in similar changes in amount, but in the opposite direction from the changes presented in the preceding sentence. Additionally, an increase of 25 basis points in the discount rate would have decreased the benefit obligation by $76 million and a decrease of 25 basis points in the discount rate would have increased the benefit obligation by $80 million at December 31, 2017. For measurement of other postretirement benefits, a 6.50% annual rate of increase in the per capita cost of covered health care benefits was assumed for 2018. The rate was assumed to decrease to 5.00% over 11 years. A one-percentage point change in assumed health care cost trend rates would have had the following effects: +1% -1% (In thousands) Increase (decrease) in: Service and interest cost $ 63 $ (57 ) Accumulated postretirement benefit obligation 1,454 (1,316 ) Plan assets The Company’s policy is to invest the pension plan assets in a prudent manner for the purpose of providing benefit payments to participants and mitigating reasonable expenses of administration. The Company’s investment strategy is designed to provide a total return that, over the long-term, places an emphasis on the preservation of capital. The strategy attempts to maximize investment returns on assets at a level of risk deemed appropriate by the Company while complying with applicable regulations and laws. The investment strategy utilizes asset diversification as a principal determinant for establishing an appropriate risk profile while emphasizing total return realized from capital appreciation, dividends and interest income. The target allocations for plan assets are generally 25 to 60 percent equity securities, 10 to 65 percent debt securities, and 10 to 85 percent money-market investments/cash equivalents and other investments, although holdings could be more or less than these general guidelines based on market conditions at the time and actions taken or recommended by the investment managers providing advice to the Company. Assets are managed by a combination of internal and external investment managers. Equity securities may include investments in domestic and international equities, through individual securities, mutual funds and exchange-traded funds. Debt securities may include investments in corporate bonds of companies from diversified industries, mortgage-backed securities guaranteed by government agencies and U.S. Treasury securities, through individual securities and mutual funds. Additionally, the Company’s defined benefit pension plan held $304,463,000 (15% of total assets) of real estate funds, private investments, hedge funds and other investments at December 31, 2017. Returns on invested assets are periodically compared with target market indices for each asset type to aid management in evaluating such returns. Furthermore, management regularly reviews the investment policy and may, if deemed appropriate, make changes to the target allocations noted above. The fair values of the Company’s pension plan assets at December 31, 2017 and 2016, by asset category, were as follows: Fair Value Measurement of Plan Assets At December 31, 2017 Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Asset category: Money-market investments $ 117,648 $ 62,706 $ 54,942 $ — Equity securities: M&T 154,818 154,818 — — Domestic(a) 240,763 240,763 — — International(b) 13,349 13,349 — — Mutual funds: Domestic(a) 205,509 205,509 — — International(b) 405,200 405,200 — — 1,019,639 1,019,639 — — Debt securities: Corporate(c) 89,751 — 89,751 — Government 235,984 — 235,984 — International 2,176 — 2,176 — Mutual funds: Domestic(d) 243,456 243,456 — — 571,367 243,456 327,911 — Other: Diversified mutual fund 80,227 80,227 — — Real estate partnerships 3,747 842 — 2,905 Private equity 31,484 — — 31,484 Hedge funds 178,080 125,966 — 52,114 Guaranteed deposit fund 10,925 — — 10,925 304,463 207,035 — 97,428 Total(e) $ 2,013,117 $ 1,532,836 $ 382,853 $ 97,428 Fair Value Measurement of Plan Assets At December 31, 2016 Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Asset category: Money-market investments $ 39,556 $ 35,562 $ 3,994 $ — Equity securities: M&T 164,474 164,474 — — Domestic(a) 200,595 200,595 — — International(b) 14,364 14,364 — — Mutual funds: Domestic(a) 250,472 250,472 — — International(b) 290,172 290,172 — — 920,077 920,077 — — Debt securities: Corporate(c) 104,909 — 104,909 — Government 121,869 — 121,869 — International 13,073 — 13,073 — Mutual funds: Domestic(d) 205,847 205,847 — — 445,698 205,847 239,851 — Other: Diversified mutual fund 92,691 92,691 — — Real estate partnerships 3,112 768 — 2,344 Private equity 21,924 — — 21,924 Hedge funds 106,250 85,270 — 20,980 Guaranteed deposit fund 10,992 — — 10,992 234,969 178,729 — 56,240 Total(e) $ 1,640,300 $ 1,340,215 $ 243,845 $ 56,240 (a) This category is mainly comprised of equities of companies primarily within the mid-cap and large-cap sectors of the U.S. economy and range across diverse industries. (b) This category is comprised of equities in companies primarily within the mid-cap and large-cap sectors of international markets mainly in developed markets in Europe and the Pacific Rim. (c) This category represents investment grade bonds of U.S. issuers from diverse industries. (d) Approximately 77% of the mutual funds were invested in investment grade bonds and 23% in high-yielding bonds at December 31, 2017. Approximately 75% of the mutual funds were invested in investment grade bonds and 25% in high-yielding bonds at December 31, 2016. The holdings within the funds were spread across diverse industries. (e) Excludes dividends and interest receivable totaling $1,774,000 and $1,831,000 at December 31, 2017 and 2016, respectively. Pension plan assets included common stock of M&T with a fair value of $154,818,000 (7.7% of total plan assets) at December 31, 2017 and $164,474,000 (10.0% of total plan assets) at December 31, 2016. No investment in securities of a non-U.S. Government or government agency issuer exceeded ten percent of plan assets at December 31, 2017. Assets subject to Level 3 valuations did not constitute a significant portion of plan assets at December 31, 2017 or December 31, 2016. The changes in Level 3 pension plan assets measured at estimated fair value on a recurring basis during the year ended December 31, 2017 were as follows: Balance – January 1, 2017 Purchases (Sales) Total Realized/ Unrealized Gains (Losses) Balance – December 31, 2017 (In thousands) Other Real estate partnerships $ 2,344 $ 365 $ 196 $ 2,905 Private equity 21,924 6,821 2,739 31,484 Hedge funds 20,980 29,839 1,295 52,114 Guaranteed deposit fund 10,992 — (67 ) 10,925 Total $ 56,240 $ 37,025 $ 4,163 $ 97,428 The Company makes contributions to its funded qualified defined benefit pension plan as required by government regulation or as deemed appropriate by management after considering factors such as the fair value of plan assets, expected returns on such assets, and the present value of benefit obligations of the plan. The Company made voluntary contributions of $200 million to the qualified defined benefit pension plan in 2017. Estimated benefits expected to be paid in future years related to the Company’s defined benefit pension and other postretirement benefits plans are as follows: Pension Benefits Other Postretirement Benefits (In thousands) Year ending December 31: 2018 $ 88,407 $ 7,318 2019 94,317 7,207 2020 98,753 7,055 2021 103,968 4,402 2022 107,298 4,302 2023 through 2027 594,900 19,830 The Company has a retirement savings plan (“RSP”) that is a defined contribution plan in which eligible employees of the Company may defer up to 50% of qualified compensation via contributions to the plan. The Company makes an employer matching contribution in an amount equal to 75% of an employee’s contribution, up to 4.5% of the employee’s qualified compensation. Employees’ accounts, including employee contributions, employer matching contributions and accumulated earnings thereon, are at all times fully vested and nonforfeitable. Employee benefits expense resulting from the Company’s contributions to the RSP totaled $38,229,000, $36,766,000 and $34,145,000 in 2017, 2016 and 2015, respectively.

Income taxes

Income taxes	12 Months Ended
Income taxes	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income taxes	13. Income taxes The components of income tax expense were as follows: Year Ended December 31 2017 2016 2015 (In thousands) Current Federal $ 363,043 $ 428,750 $ 130,349 State and local 94,714 95,426 21,549 Total current 457,757 524,176 151,898 Deferred Federal 367,308 147,662 324,317 State and local 33,482 26,351 72,279 Total deferred 400,790 174,013 396,596 Amortization of investments in qualified affordable housing projects 57,009 45,095 46,531 Total income taxes applicable to pre-tax income $ 915,556 $ 743,284 $ 595,025 The Company files a consolidated federal income tax return reflecting taxable income earned by all domestic subsidiaries. In prior years, applicable federal tax law allowed certain financial institutions the option of deducting as bad debt expense for tax purposes amounts in excess of actual losses. In accordance with GAAP, such financial institutions were not required to provide deferred income taxes on such excess. Recapture of the excess tax bad debt reserve established under the previously allowed method will result in taxable income if M&T Bank fails to maintain bank status as defined in the Internal Revenue Code or charges are made to the reserve for other than bad debt losses. At December 31, 2017, M&T Bank’s tax bad debt reserve for which no federal income taxes have been provided was $137,121,000. No actions are planned that would cause this reserve to become wholly or partially taxable. Income taxes attributable to gains or losses on bank investment securities were an expense of $7,195,000 in 2017 and $11,925,000 in 2016. There were no significant gains or losses on bank investment securities in 2015. No alternative minimum tax expense was recognized in 2017, 2016 or 2015. The Tax Cuts and Jobs Act (“Tax Act”) was signed into law on December 22, 2017, reducing the corporate Federal income tax rate from 35% to 21% effective January 1, 2018 and making other changes to U.S. corporate income tax laws. GAAP requires that the impact of the provisions of the Tax Act be accounted for in the period of enactment. Accordingly, the estimated incremental income tax expense recorded by the Company in the fourth quarter of 2017 related to the Tax Act was $85 million. That additional expense was largely attributable to the reduction in carrying value of net deferred tax assets reflecting lower future tax benefits resulting from the lower corporate income tax rate. During preparation of the Company’s 2017 income tax returns in 2018, additional adjustments related to enactment of the Tax Act may be identified. Any such adjustments are not expected to be material, but will be recognized in accordance with guidance contained in Staff Accounting Bulletin No. 118 from the U.S. Securities and Exchange Commission. The Company also adopted new accounting guidance for share-based transactions during the first quarter of 2017. That guidance requires that all excess tax benefits and tax deficiencies associated with share-based compensation be recognized as a component of income tax expense in the income statement. Previously, tax effects resulting from changes in M&T’s share price subsequent to the grant date were recorded through shareholders’ equity at the time of vesting or exercise. The adoption of the amended accounting guidance resulted in a $22 million reduction of income tax expense in 2017. Total income taxes differed from the amount computed by applying the statutory federal income tax rate to pre-tax income as follows: Year Ended December 31 2017 2016 2015 (In thousands) Income taxes at statutory federal income tax rate $ 813,352 $ 720,439 $ 586,142 Increase (decrease) in taxes: Tax-exempt income (40,778 ) (35,364 ) (33,102 ) State and local income taxes, net of federal income tax effect 83,327 79,155 60,988 Qualified affordable housing project federal tax credits, net (16,015 ) (15,091 ) (15,297 ) Initial impact of enactment of Tax Act 85,431 — — Other (9,761 ) (5,855 ) (3,706 ) $ 915,556 $ 743,284 $ 595,025 Deferred tax assets (liabilities) were comprised of the following at December 31: 2017 2016 2015 (In thousands) Losses on loans and other assets $ 345,609 $ 590,288 $ 637,955 Retirement benefits 45,322 143,067 148,722 Postretirement and other employee benefits 26,009 52,512 55,962 Incentive and other compensation plans 25,050 36,616 60,337 Interest on loans 37,900 61,266 57,640 Stock-based compensation 26,676 52,181 72,090 Unrealized losses — 10,741 — Other 66,247 106,876 162,086 Gross deferred tax assets 572,813 1,053,547 1,194,792 Leasing transactions (181,159 ) (266,268 ) (285,074 ) Unrealized gains (94,285 ) — (31,121 ) Capitalized servicing rights (51,781 ) (71,108 ) (59,171 ) Depreciation and amortization (52,733 ) (63,959 ) (56,731 ) Other (21,599 ) (87,200 ) (55,611 ) Gross deferred tax liabilities (401,557 ) (488,535 ) (487,708 ) Net deferred tax asset $ 171,256 $ 565,012 $ 707,084 The Company believes that it is more likely than not that the deferred tax assets will be realized through taxable earnings or alternative tax strategies. The income tax credits shown in the statement of income of M&T in note 25 arise principally from operating losses before dividends from subsidiaries. A reconciliation of the beginning and ending amount of unrecognized tax benefits follows: Federal, State and Local Tax Accrued Interest Unrecognized Income Tax Benefits (In thousands) Gross unrecognized tax benefits at January 1, 2015 $ 10,712 $ 3,869 $ 14,581 Increases as a result of tax positions taken during 2015 8,108 — 8,108 Increases as a result of tax positions taken in prior years — 807 807 Decreases as a result of settlements with taxing authorities (1,515 ) (274 ) (1,789 ) Unrealized tax benefits acquired in a business combination 7,232 3,567 10,799 Gross unrecognized tax benefits at December 31, 2015 24,537 7,969 32,506 Increases as a result of tax positions taken during 2016 12,237 — 12,237 Increases as a result of tax positions taken in prior years — 656 656 Decreases as a result of tax positions in prior years (885 ) (710 ) (1,595 ) Gross unrecognized tax benefits at December 31, 2016 35,889 7,915 43,804 Increases as a result of tax positions taken during 2017 13,019 — 13,019 Increases as a result of tax positions taken in prior years — 1,379 1,379 Decreases as a result of settlements with taxing authorities (332 ) (168 ) (500 ) Decreases as a result of tax positions taken in prior years (3,144 ) (3,475 ) (6,619 ) Gross unrecognized tax benefits at December 31, 2017 $ 45,432 $ 5,651 51,083 Less: Federal, state and local income tax benefits (10,727 ) Net unrecognized tax benefits at December 31, 2017 that, if recognized, would impact the effective income tax rate $ 40,356 The Company’s policy is to recognize interest and penalties, if any, related to unrecognized tax benefits in income taxes in the consolidated statement of income. The balance of accrued interest at December 31, 2017 is included in the table above. The Company’s federal, state and local income tax returns are routinely subject to examinations from various governmental taxing authorities. Such examinations may result in challenges to the tax return treatment applied by the Company to specific transactions. Management believes that the assumptions and judgment used to record tax-related assets or liabilities have been appropriate. Should determinations rendered by tax authorities ultimately indicate that management’s assumptions were inappropriate, the result and adjustments required could have a material effect on the Company’s results of operations. Examinations by the Internal Revenue Service of the Company’s federal income tax returns have been largely concluded through 2016, although under statute the income tax returns from 2014 through 2016 could be adjusted. The Company also files income tax returns in over forty states and numerous local jurisdictions. Substantially all material state and local matters have been concluded for years through 2013. It is not reasonably possible to estimate when examinations for any subsequent years will be completed.

Earnings per common share

Earnings per common share	12 Months Ended
Earnings per common share	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings per common share	14. Earnings per common share The computations of basic earnings per common share follow: Year Ended December 31 2017 2016 2015 (In thousands, except per share) Income available to common shareholders: Net income $ 1,408,306 $ 1,315,114 $ 1,079,667 Less: Preferred stock dividends(a) (72,734 ) (81,270 ) (81,270 ) Net income available to common equity 1,335,572 1,233,844 998,397 Less: Income attributable to unvested stock-based compensation awards (8,069 ) (10,385 ) (10,708 ) Net income available to common shareholders $ 1,327,503 $ 1,223,459 $ 987,689 Weighted-average shares outstanding: Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards 153,092 158,121 138,285 Less: Unvested stock-based compensation awards (933 ) (1,341 ) (1,482 ) Weighted-average shares outstanding 152,159 156,780 136,803 Basic earnings per common share $ 8.72 $ 7.80 $ 7.22 (a) Including impact of not as yet declared cumulative dividends. The computations of diluted earnings per common share follow: Year Ended December 31 2017 2016 2015 (In thousands, except per share) Net income available to common equity $ 1,335,572 $ 1,233,844 $ 998,397 Less: Income attributable to unvested stock-based compensation awards (8,055 ) (10,363 ) (10,673 ) Net income available to common shareholders $ 1,327,517 $ 1,223,481 $ 987,724 Adjusted weighted-average shares outstanding: Common and unvested stock-based compensation awards 153,092 158,121 138,285 Less: Unvested stock-based compensation awards (933 ) (1,341 ) (1,482 ) Plus: Incremental shares from assumed conversion of stock-based compensation awards and warrants to purchase common stock 392 524 730 Adjusted weighted-average shares outstanding 152,551 157,304 137,533 Diluted earnings per common share $ 8.70 $ 7.78 $ 7.18 GAAP defines unvested share-based awards that contain nonforfeitable rights to dividends or dividend equivalents (whether Stock-based compensation awards and warrants to purchase common stock of M&T representing common shares of

Comprehensive income

Comprehensive income	12 Months Ended
Comprehensive income	Dec. 31, 2017
Equity [Abstract]
Comprehensive income	15. Comprehensive income In February 2018, the Financial Accounting Standards Board issued accounting guidance related to reclassification of certain tax effects from AOCI so that following enactment of the Tax Act the tax effects of items within AOCI reflect the appropriate tax. The guidance provided for a reclassification from AOCI to retained earnings for the effect of remeasuring deferred tax assets and liabilities related to items within AOCI at the 21 percent corporate tax rate established by the Tax Act. The impact of that reclassification was an increase in retained earnings as of December 31, 2017 resulting from items remaining in AOCI as of that date as follows: (In thousands) Net unrealized losses on investment securities $ 8,065 Defined benefit plans liability adjustments 53,960 Cash flow hedges and other 2,004 Increase to retained earnings $ 64,029 The following tables display the components of other comprehensive income (loss) and amounts reclassified from accumulated other Total Defined Amount Investment Securities Benefit Before Income With OTTI (a) All Other Plans Other Tax Tax Net (In thousands) Balance — January 1, 2017 $ 46,725 (73,785 ) (449,917 ) (8,268 ) $ (485,245 ) 190,609 $ (294,636 ) Other comprehensive income before reclassifications: Unrealized holding gains (losses), net (8,746 ) (6,259 ) — — (15,005 ) 7,269 (7,736 ) Foreign currency translation adjustment — — — 4,447 4,447 (2,206 ) 2,241 Unrealized losses on cash flow hedges — — — (12,291 ) (12,291 ) 4,837 (7,454 ) Current year benefit plans gains — — 9,276 — 9,276 (3,650 ) 5,626 Total other comprehensive income (loss) before reclassifications (8,746 ) (6,259 ) 9,276 (7,844 ) (13,573 ) 6,250 (7,323 ) Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income: Amortization of unrealized holding losses on held-to-maturity (“HTM”) securities — 3,387 — — 3,387 (b) (1,333 ) 2,054 Gains realized in net income (18,351 ) (2,928 ) — — (21,279 ) (c) 7,195 (14,084 ) Accretion of net gain on terminated cash flow hedges — — — (137 ) (137 ) (d) 54 (83 ) Net yield adjustment from cash flow hedges currently in effect — — — (3,916 ) (3,916 ) (b) 1,541 (2,375 ) Amortization of prior service credit — — (802 ) — (802 ) (e) 315 (487 ) Amortization of actuarial losses — — 28,275 — 28,275 (e) (11,126 ) 17,149 Total (27,097 ) (5,800 ) 36,749 (11,897 ) (8,045 ) 2,896 (5,149 ) Reclassification of income tax effects to retained earnings — — — — — (64,029 ) (64,029 ) Balance — December 31, 2017 $ 19,628 (79,585 ) (413,168 ) (20,165 ) $ (493,290 ) 129,476 $ (363,814 ) Total Defined Amount Investment Securities Benefit Before Income With OTTI (a) All Other Plans Other Tax Tax Net (In thousands) Balance — January 1, 2016 $ 16,359 62,849 (489,660 ) (4,093 ) $ (414,545 ) 162,918 $ (251,627 ) Other comprehensive income before reclassifications: Unrealized holding gains (losses), net 30,366 (110,316 ) — — (79,950 ) 31,509 (48,441 ) Foreign currency translation adjustment — — — (4,020 ) (4,020 ) 1,406 (2,614 ) Current year benefit plans gains — — 14,125 — 14,125 (5,557 ) 8,568 Total other comprehensive income (loss) before reclassifications 30,366 (110,316 ) 14,125 (4,020 ) (69,845 ) 27,358 (42,487 ) Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income: Amortization of unrealized holding losses on HTM securities — 3,996 — — 3,996 (b) (1,572 ) 2,424 Gains realized in net income — (30,314 ) — — (30,314 ) (c) 11,925 (18,389 ) Accretion of net gain on terminated cash flow hedges — — — (155 ) (155 ) (d) 61 (94 ) Amortization of prior service credit — — (4,587 ) — (4,587 ) (e) 1,805 (2,782 ) Amortization of actuarial losses — — 30,205 — 30,205 (e) (11,886 ) 18,319 Total reclassifications — (26,318 ) 25,618 (155 ) (855 ) 333 (522 ) Total gain (loss) during the period 30,366 (136,634 ) 39,743 (4,175 ) (70,700 ) 27,691 (43,009 ) Balance — December 31, 2016 $ 46,725 (73,785 ) (449,917 ) (8,268 ) $ (485,245 ) 190,609 $ (294,636 ) Balance — January 1, 2015 $ 7,438 201,828 (503,027 ) (4,082 ) $ (297,843 ) 116,849 $ (180,994 ) Other comprehensive income before reclassifications: Unrealized holding gains (losses), net 8,921 (142,623 ) — — (133,702 ) 52,376 (81,326 ) Foreign currency translation adjustment — — — (1,323 ) (1,323 ) 398 (925 ) Gains on cash flow hedges — — — 1,453 1,453 (572 ) 881 Current year benefit plans losses — — (24,200 ) — (24,200 ) 8,612 (15,588 ) Total other comprehensive income (loss) before reclassifications 8,921 (142,623 ) (24,200 ) 130 (157,772 ) 60,814 (96,958 ) Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income: Amortization of unrealized holding losses on HTM securities — 3,514 — — 3,514 (b) (1,383 ) 2,131 Losses realized in net income — 130 — — 130 (c) (49 ) 81 Accretion of net gain on terminated cash flow hedges — — — (141 ) (141 ) (d) 56 (85 ) Amortization of prior service credit — — (7,364 ) — (7,364 ) (e) 2,620 (4,744 ) Amortization of actuarial losses — — 44,931 — 44,931 (e) (15,989 ) 28,942 Total reclassifications — 3,644 37,567 (141 ) 41,070 (14,745 ) 26,325 Total gain (loss) during the period 8,921 (138,979 ) 13,367 (11 ) (116,702 ) 46,069 (70,633 ) Balance — December 31, 2015 $ 16,359 62,849 (489,660 ) (4,093 ) $ (414,545 ) 162,918 $ (251,627 ) (a) Other-than-temporary impairment. (b) Included in interest income. (c) Included in gain (loss) on bank investment securities. (d) Included in interest expense. (e) Included in salaries and employee benefits expense. Accumulated other comprehensive income (loss), net consisted of the following: Investment Securities Defined With OTTI All Other Benefit Plans Other Total (In thousands) Balance at January 1, 2015 $ 4,518 $ 122,683 $ (305,589 ) $ (2,606 ) $ (180,994 ) Net gain (loss) during 2015 5,403 (84,517 ) 8,610 (129 ) (70,633 ) Balance at December 31, 2015 9,921 38,166 (296,979 ) (2,735 ) (251,627 ) Net gain (loss) during 2016 18,417 (82,823 ) 24,105 (2,708 ) (43,009 ) Balance at December 31, 2016 28,338 (44,657 ) (272,874 ) (5,443 ) (294,636 ) Net gain (loss) during 2017 (10,755 ) (9,011 ) 22,288 (7,671 ) (5,149 ) Reclassification of income tax effects to retained earnings (3,115 ) (4,950 ) (53,960 ) (2,004 ) (64,029 ) Balance at December 31, 2017 $ 14,468 $ (58,618 ) $ (304,546 ) $ (15,118 ) $ (363,814 )

Other income and other expense

Other income and other expense	12 Months Ended
Other income and other expense	Dec. 31, 2017
Other Income And Expenses [Abstract]
Other income and other expense	16. Other income and other expense The following items, which exceeded 1% of total interest income and other income in the respective period, were included in either “other revenues from operations” or “other costs of operations” in the consolidated statement of income: Year Ended December 31 2017 2016 2015 (In thousands) Other income: Credit-related fee income $ 77,580 $ 70,424 $ 81,558 Letter of credit fees 52,724 Bank owned life insurance 52,984 Other expense: Professional services 289,862 268,060 267,540 Amortization of capitalized servicing rights 49,906

International activities

International activities	12 Months Ended
International activities	Dec. 31, 2017
International Activities [Abstract]
International Activities	17. International activities The Company engages in limited international activities including certain trust-related services in Europe, collecting Eurodollar deposits, engaging in foreign currency transactions associated with customer activity, providing credit to support the international activities of domestic companies and holding certain loans to foreign borrowers. Assets and revenues associated with international activities represent less than 1% of the Company’s consolidated assets and revenues. International assets included $159 million and $292 million of loans to foreign borrowers at December 31, 2017 and 2016, respectively. Deposits at M&T Bank’s Cayman Islands office were $178 million and $202 million at December 31, 2017 and 2016, respectively. The Company uses such deposits to facilitate customer demand and as an alternative to short-term borrowings when the costs of such deposits seem reasonable. Deposits at M&T Bank’s office in Ontario, Canada were $45 million at December 31, 2017 and $50 million at December 31, 2016. Revenues from providing international trust-related services were approximately $24 million in 2017, $25 million in 2016 and $26 million in 2015.

Derivative financial instrument

Derivative financial instruments	12 Months Ended
Derivative financial instruments	Dec. 31, 2017
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative financial instruments	18. Derivative financial instruments As part of managing interest rate risk, the Company enters into interest rate swap agreements to modify the repricing characteristics of certain portions of the Company’s portfolios of earning assets and interest-bearing liabilities. The Company designates interest rate swap agreements utilized in the management of interest rate risk as either fair value hedges or cash flow hedges. Interest rate swap agreements are generally entered into with counterparties that meet established credit standards and most contain master netting, collateral and/or settlement provisions protecting the at-risk party. Based on adherence to the Company’s credit standards and the presence of the netting, collateral or settlement provisions, the Company believes that the credit risk inherent in these contracts was not significant as of December 31, 2017. The net effect of interest rate swap agreements was to increase net interest income by $25 million in 2017, $37 million in 2016 and $44 million in 2015. Information about interest rate swap agreements entered into for interest rate risk management purposes summarized by type of financial instrument the swap agreements were intended to hedge follows: Weighted- Average Rate Notional Amount Average Maturity Fixed Variable Estimated Fair Value Gain (a) (In (In (In December 31, 2017 Fair value hedges: Fixed rate long-term borrowings(b) $ 4,550,000 2.9 2.27 % 2.09 % $ 573 Cash flow hedges: Variable rate commercial real estate loans(b)( c) 4,850,000 2.0 1.52 % 1.36 % 66 Total $ 9,400,000 2.5 $ 639 December 31, 2016 Fair value hedges: Fixed rate long-term borrowings(b) $ 900,000 1.1 3.75 % 2.08 % $ 11,892 (a) Effective January 2017 certain clearinghouse exchanges revised their rules such that certain required payments by counterparties for variation margin on derivative instruments that had been treated as collateral are now treated as settlements of those positions. The impact of such rule changes at December 31, 2017 was a reduction of the estimated fair value losses on interest rate swap agreements designated as fair value hedges of $41.1 million and on interest rate swap agreements designated as cash flow hedges of $16.3 million. (b) Under the terms of these agreements, the Company receives settlement amounts at a fixed rate and pays at a variable rate. (c) Includes notional amount and terms of $2.0 billion of forward-starting interest rate swap agreements that will become effective upon maturity in 2019 of $2.0 billion of agreements currently in effect. The notional amount of interest rate swap agreements entered into for risk management purposes that were outstanding at December 31, 2017 mature as follows: (In thousands) Year ending December 31: 2018 $ 500,000 2019 4,250,000 2020 3,500,000 2021 — 2022 650,000 2023 through 2027 500,000 $ 9,400,000 The Company utilizes commitments to sell residential and commercial real estate loans to hedge the exposure to changes in the fair value of real estate loans held for sale. Such commitments have generally been designated as fair value hedges. The Company also utilizes commitments to sell real estate loans to offset the exposure to changes in fair value of certain commitments to originate real estate loans for sale. Derivative financial instruments used for trading account purposes included interest rate contracts, foreign exchange and other option contracts, foreign exchange forward and spot contracts, and financial futures. Interest rate contracts entered into for trading account purposes had notional values of $29.9 billion and $21.6 billion at December 31, 2017 and 2016, respectively. The notional amounts of foreign currency and other option and futures contracts entered into for trading account purposes aggregated $530 million and $471 million at December 31, 2017 and 2016, respectively. Information about the fair values of derivative instruments in the Company’s consolidated balance sheet and consolidated statement of income follows: Asset Derivatives Liability Derivatives Fair Value Fair Value December 31 December 31 2017 2016 2017 2016 (In thousands) Derivatives designated and qualifying as hedging instruments Interest rate swap agreements (a) $ 639 $ 11,892 $ — $ — Commitments to sell real estate loans (a) 734 33,189 283 1,347 1,373 45,081 283 1,347 Derivatives not designated and qualifying as hedging instruments Mortgage-related commitments to originate real estate loans for sale (a) 8,797 8,060 494 735 Commitments to sell real estate loans (a) 2,526 5,210 1,019 399 Trading: Interest rate contracts (b) 74,164 228,810 132,104 167,737 Foreign exchange and other option and futures contracts (b) 5,657 7,908 5,286 6,639 91,144 249,988 138,903 175,510 Total derivatives $ 92,517 $ 295,069 $ 139,186 $ 176,857 (a) Asset derivatives are reported in other assets and liability derivatives are reported in other liabilities. (b) Asset derivatives are reported in trading account assets and liability derivatives are reported in other liabilities. The impact of the variation margin rule change at December 31, 2017 was a reduction of the estimated fair value of interest rate contracts in the trading account in an asset position of $136.2 million and in a liability position of $12.2 million. Amount of Gain (Loss) Recognized Year Ended December 31, 2017 Year Ended December 31, 2016 Year Ended December 31, 2015 Derivative Hedged Item Derivative Hedged Item Derivative Hedged Item (In thousands) Derivatives in fair value hedging relationships Interest rate swap agreements: Fixed rate long-term borrowings (a) $ (52,392 ) 51,628 $ (32,000 ) 30,906 $ (29,359 ) 28,719 Derivatives not designated as hedging Trading: Interest rate contracts (b) $ 5,398 $ 14,042 $ 10,755 Foreign exchange and other option and futures contracts (b) 6,821 7,665 9,337 Total $ 12,219 $ 21,707 $ 20,092 (a) Reported as other revenues from operations. (b) Reported as trading account and foreign exchange gains. The amount of gain (loss) recognized in the consolidated statement of income associated with derivatives designated as cash flow hedges was not material. The Company also has commitments to sell and commitments to originate residential and commercial real estate loans that are considered derivatives. The Company designates certain of the commitments to sell real estate loans as fair value hedges of real estate loans held for sale. The Company also utilizes commitments to sell real estate loans to offset the exposure to changes in the fair value of certain commitments to originate real estate loans for sale. As a result of these activities, net unrealized pre-tax gains related to hedged loans held for sale, commitments to originate loans for sale and commitments to sell loans were approximately $16 million and $28 million at December 31, 2017 and 2016, respectively. Changes in unrealized gains and losses are included in mortgage banking revenues and, in general, are realized in subsequent periods as the related loans are sold and commitments satisfied. The Company does not offset derivative asset and liability positions in its consolidated financial statements. The Company’s exposure to credit risk by entering into derivative contracts is mitigated through master netting agreements and collateral posting or settlement requirements. Master netting agreements covering interest rate and foreign exchange contracts with the same party include a right to set-off that becomes enforceable in the event of default, early termination or under other specific conditions. The aggregate fair value of derivative financial instruments in a liability position, which are subject to enforceable master netting arrangements, was $13 million and $34 million at December 31, 2017 and 2016, respectively. After consideration of such netting arrangements, for purposes of posting collateral, the net liability positions with counterparties aggregated $13 million and $30 million at December 31, 2017 and 2016, respectively. The Company was required to post collateral relating to those positions of $12 million and $27 million at December 31, 2017 and 2016, respectively. Certain of the Company’s derivative financial instruments contain provisions that require the Company to maintain specific credit ratings from credit rating agencies to avoid higher collateral posting requirements. If the Company’s debt ratings were to fall below specified ratings, the counterparties of the derivative financial instruments could demand immediate incremental collateralization on those instruments in a net liability position. The aggregate fair value of all derivative financial instruments with such credit risk-related contingent features in a net liability position on December 31, 2017 was less than $1 million, for which the Company was not required to post collateral in the normal course of business. If the credit risk-related contingent features had been triggered on December 31, 2017, the Company would not have been required to post any additional collateral with counterparties. The aggregate fair value of derivative financial instruments in an asset position, which are subject to enforceable master netting arrangements, was $13 million and $15 million at December 31, 2017 and 2016, respectively. After consideration of such netting arrangements, for purposes of posting collateral, the net asset positions with counterparties aggregated $13 million and $11 million at December 31, 2017 and 2016, respectively. Counterparties posted collateral relating to those positions of $12 million and $9 million at December 31, 2017 and 2016, respectively. Trading account interest rate swap agreements entered into with customers are subject to the Company’s credit risk standards and often contain collateral provisions. In addition to the derivative contracts noted above, the Company clears certain derivative transactions through a clearinghouse, rather than directly with counterparties. Those transactions cleared through a clearinghouse require initial margin collateral and variation margin payments depending on the contracts being in a net asset or liability position. The amount of initial margin collateral posted by the Company was $52 million and $111 million at December 31, 2017 and 2016, respectively. The fair value asset and liability amounts of derivative contracts at December 31, 2017 have been reduced by variation margin payments treated as settlements of $136 million and $70 million, respectively. Variation margin on derivative contracts not treated as settlements continues to represent collateral posted or received by the Company. For those contracts, the net fair value of derivative financial instruments cleared through clearinghouses for which variation margin is required was a net asset position of $2 million and $63 million at December 31, 2017 and December 31, 2016, respectively. Collateral posted by the clearinghouses associated with that net asset position was $2 million and $81 million at December 31, 2017 and 2016, respectively.

Variable interest entities

Variable interest entities	12 Months Ended
Variable interest entities	Dec. 31, 2017
Text Block [Abstract]
Variable interest entities	19. Variable interest entities As described in note 9, M&T has issued junior subordinated debentures payable to various trusts that have issued Capital Securities. M&T owns the common securities of those trust entities. The Company is not considered to be the primary beneficiary of those entities and, accordingly, the trusts are not included in the Company’s consolidated financial statements. At December 31, 2017 and 2016, the Company included the junior subordinated debentures as “long-term borrowings” in its consolidated balance sheet and recognized $23 million and $24 million, respectively, in other assets for its “investment” in the common securities of the trusts that will be concomitantly repaid to M&T by the respective trust from the proceeds of M&T’s repayment of the junior subordinated debentures associated with preferred capital securities described in note 9. The Company has invested as a limited partner in various partnerships that collectively had total assets of approximately $1.0 billion at each of December 31, 2017 and December 31, 2016. Those partnerships generally construct or acquire properties for which the investing partners are eligible to receive certain federal income tax credits in accordance with government guidelines. Such investments may also provide tax deductible losses to the partners. The partnership investments also assist the Company in achieving its community reinvestment initiatives. As a limited partner, there is no recourse to the Company by creditors of the partnerships. However, the tax credits that result from the Company’s investments in such partnerships are generally subject to recapture should a partnership fail to comply with the respective government regulations. The Company’s maximum exposure to loss of its investments in such partnerships was $420 million, including $201 million of unfunded commitments, at December 31, 2017 and $294 million, including $102 million of unfunded commitments, at December 31, 2016. Contingent commitments to provide additional capital contributions to these partnerships were not material at December 31, 2017. The Company has not provided financial or other support to the partnerships that was not contractually required. Management currently estimates that no material losses are probable as a result of the Company’s involvement with such entities. The Company, in its position as limited partner, does not direct the activities that most significantly impact the economic performance of the partnerships and, therefore, in accordance with the accounting provisions for variable interest entities, the partnership entities are not included in the Company’s consolidated financial statements. The Company’s investment cost is amortized to income taxes in the consolidated statement of income as tax credits and other tax benefits resulting from deductible losses associated with the projects are received. The Company serves as investment advisor for certain registered money-market funds. The Company has no explicit arrangement to provide support to those funds, but may waive portions of its allowable management fees as a result of market conditions.

Fair value measurements

Fair value measurements	12 Months Ended
Fair value measurements	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair value measurements	20. Fair value measurements GAAP permits an entity to choose to measure eligible financial instruments and other items at fair value. The Company has not made any fair value elections at December 31, 2017. Pursuant to GAAP, fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. A three-level hierarchy exists in GAAP for fair value measurements based upon the inputs to the valuation of an asset or liability. • Level 1 — Valuation is based on quoted prices in active markets for identical assets and liabilities. • Level 2 — Valuation is determined from quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar instruments in markets that are not active or by model-based techniques in which all significant inputs are observable in the market. • Level 3 — Valuation is derived from model-based and other techniques in which at least one significant input is unobservable and which may be based on the Company’s own estimates about the assumptions that market participants would use to value the asset or liability. When available, the Company attempts to use quoted market prices in active markets to determine fair value and classifies such items as Level 1 or Level 2. If quoted market prices in active markets are not available, fair value is often determined using model-based techniques incorporating various assumptions including interest rates, prepayment speeds and credit losses. Assets and liabilities valued using model-based techniques are classified as either Level 2 or Level 3, depending on the lowest level classification of an input that is considered significant to the overall valuation. The following is a description of the valuation methodologies used for the Company’s assets and liabilities that are measured on a recurring basis at estimated fair value. Trading account assets and liabilities Trading account assets and liabilities include interest rate contracts and foreign exchange contracts with customers who require such services with offsetting positions with third parties to minimize the Company’s risk with respect to such transactions. The Company generally determines the fair value of its derivative trading account assets and liabilities using externally developed pricing models based on market observable inputs and, therefore, classifies such valuations as Level 2. Mutual funds held in connection with deferred compensation and other arrangements have been classified as Level 1 valuations. Valuations of investments in municipal and other bonds can generally be obtained through reference to quoted prices in less active markets for the same or similar securities or through model-based techniques in which all significant inputs are observable and, therefore, such valuations have been classified as Level 2. Investment securities available for sale The majority of the Company’s available-for-sale investment securities have been valued by reference to prices for similar securities or through model-based techniques in which all significant inputs are observable and, therefore, such valuations have been classified as Level 2. Certain investments in mutual funds and equity securities are actively traded and, therefore, have been classified as Level 1 valuations. Real estate loans held for sale The Company utilizes commitments to sell real estate loans to hedge the exposure to changes in fair value of real estate loans held for sale. The carrying value of hedged real estate loans held for sale includes changes in estimated fair value during the hedge period. Typically, the Company attempts to hedge real estate loans held for sale from the date of close through the sale date. The fair value of hedged real estate loans held for sale is generally calculated by reference to quoted prices in secondary markets for commitments to sell real estate loans with similar characteristics and, accordingly, such loans have been classified as a Level 2 valuation. Commitments to originate real estate loans for sale and commitments to sell real estate loans The Company enters into various commitments to originate real estate loans for sale and commitments to sell real estate loans. Such commitments are considered to be derivative financial instruments and, therefore, are carried at estimated fair value on the consolidated balance sheet. The estimated fair values of such commitments were generally calculated by reference to quoted prices in secondary markets for commitments to sell real estate loans to certain government-sponsored entities and other parties. The fair valuations of commitments to sell real estate loans generally result in a Level 2 classification. The estimated fair value of commitments to originate real estate loans for sale is adjusted to reflect the Company’s anticipated commitment expirations. The estimated commitment expirations are considered significant unobservable inputs contributing to the Level 3 classification of commitments to originate real estate loans for sale. Significant unobservable inputs used in the determination of estimated fair value of commitments to originate real estate loans for sale are included in the accompanying table of significant unobservable inputs to Level 3 measurements. Interest rate swap agreements used for interest rate risk management The Company utilizes interest rate swap agreements as part of the management of interest rate risk to modify the repricing characteristics of certain portions of its portfolios of earning assets and interest-bearing liabilities. The Company generally determines the fair value of its interest rate swap agreements using externally developed pricing models based on market observable inputs and, therefore, classifies such valuations as Level 2. The Company has considered counterparty credit risk in the valuation of its interest rate swap agreement assets and has considered its own credit risk in the valuation of its interest rate swap agreement liabilities . The following tables present assets and liabilities at December 31, 2017 and 2016 measured at estimated fair value on a recurring basis: Fair Value Measurements Level 1 (a) Level 2 (a) Level 3 (In thousands) December 31, 2017 Trading account assets $ 132,909 $ 47,873 $ 85,036 $ — Investment securities available for sale: U.S. Treasury and federal agencies 1,947,487 — 1,947,487 — Obligations of states and political subdivisions 2,589 — 2,589 — Mortgage-backed securities: Government issued or guaranteed 8,716,392 — 8,716,392 — Privately issued 28 — — 28 Other debt securities 128,832 — 128,832 — Equity securities 100,956 73,232 27,724 — 10,896,284 73,232 10,823,024 28 Real estate loans held for sale 378,047 — 378,047 — Other assets (b) 12,696 — 3,899 8,797 Total assets $ 11,419,936 $ 121,105 $ 11,290,006 $ 8,825 Trading account liabilities $ 137,390 $ — $ 137,390 $ — Other liabilities (b) 1,796 — 1,302 494 Total liabilities $ 139,186 $ — $ 138,692 $ 494 December 31, 2016 Trading account assets $ 323,867 $ 46,135 $ 277,732 $ — Investment securities available for sale: U.S. Treasury and federal agencies 1,902,544 — 1,902,544 — Obligations of states and political subdivisions 3,641 — 3,641 — Mortgage-backed securities: Government issued or guaranteed 10,954,861 — 10,954,861 — Privately issued 44 — — 44 Other debt securities 118,516 — 118,516 — Equity securities 352,466 301,711 50,755 — 13,332,072 301,711 13,030,317 44 Real estate loans held for sale 1,056,180 — 1,056,180 — Other assets (b) 58,351 — 50,291 8,060 Total assets $ 14,770,470 $ 347,846 $ 14,414,520 $ 8,104 Trading account liabilities $ 174,376 $ — $ 174,376 $ — Other liabilities (b) 2,481 — 1,746 735 Total liabilities $ 176,857 $ — $ 176,122 $ 735 (a) There were no significant transfers between Level 1 and Level 2 of the fair value hierarchy during the years ended December 31, 2017 and 2016. (b) Comprised predominantly of interest rate swap agreements used for interest rate risk management (Level 2), commitments to sell real estate loans (Level 2) and commitments to originate real estate loans to be held for sale (Level 3). The changes in Level 3 assets and liabilities measured at estimated fair value on a recurring basis during the years ended December 31, 2017, 2016 and 2015 were as follows: Investment Securities Available for Sale Privately Issued Mortgage-Backed Other Assets (In thousands) 2017 Balance — January 1, 2017 $ 44 $ 7,325 Total gains (losses) realized/unrealized: Included in earnings — 77,832 (b) Sales — — Settlements (16 ) — Transfers out of Level 3 (a) — (76,854 ) (e) Balance — December 31, 2017 $ 28 8,303 Changes in unrealized gains included in earnings related to assets still held at December 31, 2017 $ — 7,978 (b) Investment Securities Available for Sale Privately Issued Mortgage-Backed Collateralized Other Assets (In thousands) 2016 Balance — January 1, 2016 $ 74 47,393 9,879 Total gains (losses) realized/unrealized: Included in earnings — 30,041 (c) 110,937 (b) Included in other comprehensive income — (18,268 ) (d) — Sales — (58,296 ) — Settlements (30 ) (870 ) — Transfers out of Level 3 (a) — — (113,491 ) (e) Balance — December 31, 2016 $ 44 — 7,325 Changes in unrealized gains included in earnings related to assets still held at December 31, 2016 $ — — 7,256 (b) 2015 Balance — January 1, 2015 $ 103 50,316 17,347 Total gains realized/unrealized: Included in earnings — — 87,061 (b) Included in other comprehensive income — 3,254 (d) — Settlements (29 ) (6,177 ) — Transfers out of Level 3 (a) — — (94,529 ) (e) Balance — December 31, 2015 $ 74 47,393 9,879 Changes in unrealized gains included in earnings related to assets still held at December 31, 2015 $ — — 8,850 (b) (a) The Company’s policy for transfers between fair value levels is to recognize the transfer as of the actual date of the event or change in circumstances that caused the transfer. (b) Reported as mortgage banking revenues in the consolidated statement of income and includes the fair value of commitment issuances and expirations. (c) Reported as gain on bank investment securities in the consolidated statement of income. (d) Reported as net unrealized gains (losses) on investment securities in the consolidated statement of comprehensive income. (e) Transfers out of Level 3 consist of interest rate locks transferred to closed loans. The Company is required, on a nonrecurring basis, to adjust the carrying value of certain assets or provide valuation allowances related to certain assets using fair value measurements. The more significant of those assets follow. Loans Loans are generally not recorded at fair value on a recurring basis. Periodically, the Company records nonrecurring adjustments to the carrying value of loans based on fair value measurements for partial charge-offs of the uncollectible portions of those loans. Nonrecurring adjustments also include certain impairment amounts for collateral-dependent loans when establishing the allowance for credit losses. Such amounts are generally based on the fair value of the underlying collateral supporting the loan and, as a result, the carrying value of the loan less the calculated valuation amount does not necessarily represent the fair value of the loan. Real estate collateral is typically valued using appraisals or other indications of value based on recent comparable sales of similar properties or assumptions generally observable in the marketplace and the related nonrecurring fair value measurement adjustments have generally been classified as Level 2, unless significant adjustments have been made to the valuation that are not readily observable by market participants. Non-real estate collateral supporting commercial loans generally consists of business assets such as receivables, inventory and equipment. Fair value estimations are typically determined by discounting recorded values of those assets to reflect estimated net realizable value considering specific borrower facts and circumstances and the experience of credit personnel in their dealings with similar borrower collateral liquidations. Such discounts were generally in the range of 10% to 85% at December 31, 2017. As these discounts are not readily observable and are considered significant, the valuations have been classified as Level 3. Automobile collateral is typically valued by reference to independent pricing sources based on recent sales transactions of similar vehicles, and the related non-recurring fair value measurement adjustments have been classified as Level 2. Collateral values for other consumer installment loans are generally estimated based on historical recovery rates for similar types of loans. As these recovery rates are not readily observable by market participants, such valuation adjustments have been classified as Level 3. Loans subject to nonrecurring fair value measurement were $210 Assets taken in foreclosure of defaulted loans Assets taken in foreclosure of defaulted loans are primarily comprised of commercial and residential real property and are generally measured at the lower of cost or fair value less costs to sell. The fair value of the real property is generally determined using appraisals or other indications of value based on recent comparable sales of similar properties or assumptions generally observable in the marketplace, and the related nonrecurring fair value measurement adjustments have generally been classified as Level 2. Assets taken in foreclosure of defaulted loans subject to nonrecurring fair value measurement were $53 Significant unobservable inputs to level 3 measurements The following tables present quantitative information about significant unobservable inputs used in the fair value measurements for Level 3 assets and liabilities at December 31, 2017 and 2016: Fair Value Valuation Technique Unobservable Inputs/Assumptions Range (Weighted- Average) (In December 31, 2017 Recurring fair value measurements Privately issued mortgage-backed securities $ 28 Two independent pricing quotes — — Net other assets (liabilities) (a) 8,303 Discounted Commitment expirations 0%-78% (22%) December 31, 2016 Recurring fair value measurements Privately issued mortgage-backed securities $ 44 Two independent pricing quotes — — Net other assets (liabilities) (a) 7,325 Discounted Commitment expirations 0%-77% (30%) (a) Other Level 3 assets (liabilities) consist of commitments to originate real estate loans. Sensitivity of fair value measurements to changes in unobservable inputs An increase (decrease) in the estimate of expirations for commitments to originate real estate loans would generally result in a lower (higher) fair value measurement. Estimated commitment expirations are derived considering loan type, changes in interest rates and remaining length of time until closing. Disclosures of fair value of financial instruments The carrying amounts and estimated fair value for financial instrument assets (liabilities) are presented in the following table: December 31, 2017 Carrying Amount Estimated Fair Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Cash and cash equivalents $ 1,420,888 1,420,888 1,352,035 68,853 — Interest-bearing deposits at banks 5,078,903 5,078,903 — 5,078,903 — Trading account assets 132,909 132,909 47,873 85,036 — Investment securities 14,664,525 14,653,074 73,232 14,469,127 110,715 Loans and leases: Commercial loans and leases 21,742,651 21,321,282 — — 21,321,282 Commercial real estate loans 33,366,373 32,950,724 — 22,130 32,928,594 Residential real estate loans 19,613,344 19,596,826 — 4,440,645 15,156,181 Consumer loans 13,266,615 13,161,517 — — 13,161,517 Allowance for credit losses (1,017,198 ) — — — — Loans and leases, net 86,971,785 87,030,349 — 4,462,775 82,567,574 Accrued interest receivable 327,170 327,170 — 327,170 — Financial liabilities: Noninterest-bearing deposits $ (33,975,180 ) (33,975,180 ) — (33,975,180 ) — Savings and interest-checking deposits (51,698,008 ) (51,698,008 ) — (51,698,008 ) — Time deposits (6,580,962 ) (6,635,048 ) — (6,635,048 ) — Deposits at Cayman Islands office (177,996 ) (177,996 ) — (177,996 ) — Short-term borrowings (175,099 ) (175,099 ) — (175,099 ) — Long-term borrowings (8,141,430 ) (8,193,783 ) — (8,193,783 ) — Accrued interest payable (75,641 ) (75,641 ) — (75,641 ) — Trading account liabilities (137,390 ) (137,390 ) — (137,390 ) — Other financial instruments: Commitments to originate real estate loans for sale $ 8,303 8,303 — — 8,303 Commitments to sell real estate loans 1,958 1,958 — 1,958 — Other credit-related commitments (125,281 ) (125,281 ) — — (125,281 ) Interest rate swap agreements used for interest rate risk management 639 639 — 639 — December 31, 2016 Carrying Amount Estimated Fair Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Cash and cash equivalents $ 1,320,549 1,320,549 1,249,654 70,895 — Interest-bearing deposits at banks 5,000,638 5,000,638 — 5,000,638 — Trading account assets 323,867 323,867 46,135 277,732 — Investment securities 16,250,468 16,244,412 301,711 15,821,176 121,525 Loans and leases: Commercial loans and leases 22,610,047 22,239,428 — — 22,239,428 Commercial real estate loans 33,506,394 33,129,428 — 642,590 32,486,838 Residential real estate loans 22,590,912 22,638,167 — 4,912,488 17,725,679 Consumer loans 12,146,063 12,061,590 — — 12,061,590 Allowance for credit losses (988,997 ) — — — — Loans and leases, net 89,864,419 90,068,613 — 5,555,078 84,513,535 Accrued interest receivable 308,805 308,805 — 308,805 — Financial liabilities: Noninterest-bearing deposits $ (32,813,896 ) (32,813,896 ) — (32,813,896 ) — Savings and interest-checking deposits (52,346,207 ) (52,346,207 ) — (52,346,207 ) — Time deposits (10,131,846 ) (10,222,585 ) — (10,222,585 ) — Deposits at Cayman Islands office (201,927 ) (201,927 ) — (201,927 ) — Short-term borrowings (163,442 ) (163,442 ) — (163,442 ) — Long-term borrowings (9,493,835 ) (9,473,844 ) — (9,473,844 ) — Accrued interest payable (75,172 ) (75,172 ) — (75,172 ) — Trading account liabilities (174,376 ) (174,376 ) — (174,376 ) — Other financial instruments: Commitments to originate real estate loans for sale $ 7,325 7,325 — — 7,325 Commitments to sell real estate loans 36,653 36,653 — 36,653 — Other credit-related commitments (136,295 ) (136,295 ) — — (136,295 ) Interest rate swap agreements used for interest rate risk management 11,892 11,892 — 11,892 — With the exception of marketable securities, certain off-balance sheet financial instruments and mortgage loans originated for sale, the Company’s financial instruments are not readily marketable and market prices do not exist. The Company, in attempting to comply with the provisions of GAAP that require disclosures of fair value of financial instruments, has not attempted to market its financial instruments to potential buyers, if any exist. Since negotiated prices in illiquid markets depend greatly upon the then present motivations of the buyer and seller, it is reasonable to assume that actual sales prices could vary widely from any estimate of fair value made without the benefit of negotiations. Additionally, changes in market interest rates can dramatically impact the value of financial instruments in a short period of time. The following assumptions, methods and calculations were used in determining the estimated fair value of financial instruments not measured at fair value in the consolidated balance sheet. Cash and cash equivalents, interest-bearing deposits at banks, deposits at Cayman Islands office, short-term borrowings, accrued interest receivable and accrued interest payable Due to the nature of cash and cash equivalents and the near maturity of interest-bearing deposits at banks, deposits at Cayman Islands office, short-term borrowings, accrued interest receivable and accrued interest payable, the Company estimated that the carrying amount of such instruments approximated estimated fair value. Investment securities Estimated fair values of investments in readily marketable securities were generally based on quoted market prices. Investment securities that were not readily marketable were assigned amounts based on estimates provided by outside parties or modeling techniques that relied upon discounted calculations of projected cash flows or, in the case of other investment securities, which include capital stock of the Federal Reserve Bank of New York and the Federal Home Loan Bank of New York, at an amount equal to the carrying amount. Loans and leases In general, discount rates used to calculate values for loan products were based on the Company’s pricing at the respective period end. A higher discount rate was assumed with respect to estimated cash flows associated with nonaccrual loans. Projected loan cash flows were adjusted for estimated credit losses. However, such estimates made by the Company may not be indicative of assumptions and adjustments that a purchaser of the Company’s loans and leases would seek. Deposits Pursuant to GAAP, the estimated fair value ascribed to noninterest-bearing deposits, savings deposits and interest-checking deposits must be established at carrying value because of the customers’ ability to withdraw funds immediately. Time deposit accounts are required to be revalued based upon prevailing market interest rates for similar maturity instruments. As a result, amounts assigned to time deposits were based on discounted cash flow calculations using prevailing market interest rates based on the Company’s pricing at the respective date for deposits with comparable remaining terms to maturity. The Company believes that deposit accounts have a value greater than that prescribed by GAAP. The Company feels, however, that the value associated with these deposits is greatly influenced by characteristics of the buyer, such as the ability to reduce the costs of servicing the deposits and deposit attrition which often occurs following an acquisition. Long-term borrowings The amounts assigned to long-term borrowings were based on quoted market prices, when available, or were based on discounted cash flow calculations using prevailing market interest rates for borrowings of similar terms and credit risk. Other commitments and contingencies As described in note 21, in the normal course of business, various commitments and contingent liabilities are outstanding, such as loan commitments, credit guarantees and letters of credit. The Company’s pricing of such financial instruments is based largely on credit quality and relationship, probability of funding and other requirements. Loan commitments often have fixed expiration dates and contain termination and other clauses which provide for relief from funding in the event of significant deterioration in the credit quality of the customer. The rates and terms of the Company’s loan commitments, credit guarantees and letters of credit are competitive with other financial institutions operating in markets served by the Company. The Company believes that the carrying amounts, which are included in other liabilities, are reasonable estimates of the fair value of these financial instruments. The Company does not believe that the estimated information presented herein is representative of the earnings power or value of the Company. The preceding analysis, which is inherently limited in depicting fair value, also does not consider any value associated with existing customer relationships nor the ability of the Company to create value through loan origination, deposit gathering or fee generating activities. Many of the estimates presented herein are based upon the use of highly subjective information and assumptions and, accordingly, the results may not be precise. Management believes that fair value estimates may not be comparable between financial institutions due to the wide range of permitted valuation techniques and numerous estimates which must be made. Furthermore, because the disclosed fair value amounts were estimated as of the balance sheet date, the amounts actually realized or paid upon maturity or settlement of the various financial instruments could be significantly different.

Commitments and contingencies

Commitments and contingencies	12 Months Ended
Commitments and contingencies	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and contingencies	21. Commitments and contingencies In the normal course of business, various commitments and contingent liabilities are outstanding. The following table presents the Company’s significant commitments. Certain of these commitments are not included in the Company’s consolidated balance sheet. December 31 2017 2016 (In thousands) Commitments to extend credit Home equity lines of credit $ 5,482,622 5,499,609 Commercial real estate loans to be sold 194,763 70,100 Other commercial real estate 6,050,569 6,451,709 Residential real estate loans to be sold 347,113 478,950 Other residential real estate 201,426 232,721 Commercial and other 12,733,815 12,298,473 Standby letters of credit 2,497,844 2,987,091 Commercial letters of credit 46,739 44,723 Financial guarantees and indemnification contracts 3,434,381 3,043,580 Commitments to sell real estate loans 812,217 1,489,237 Commitments to extend credit are agreements to lend to customers, generally having fixed expiration dates or other termination clauses that may require payment of a fee. Standby and commercial letters of credit are conditional commitments issued to guarantee the performance of a customer to a third party. Standby letters of credit generally are contingent upon the failure of the customer to perform according to the terms of the underlying contract with the third party, whereas commercial letters of credit are issued to facilitate commerce and typically result in the commitment being funded when the underlying transaction is consummated between the customer and a third party. The credit risk associated with commitments to extend credit and standby and commercial letters of credit is essentially the same as that involved with extending loans to customers and is subject to normal credit policies. Collateral may be obtained based on management’s assessment of the customer’s creditworthiness. Financial guarantees and indemnification contracts are oftentimes similar to standby letters of credit and include mandatory purchase agreements issued to ensure that customer obligations are fulfilled, recourse obligations associated with sold loans, and other guarantees of customer performance or compliance with designated rules and regulations. Included in financial guarantees and indemnification contracts are loan principal amounts sold with recourse in conjunction with the Company’s involvement in the Fannie Mae DUS program. The Company’s maximum credit risk for recourse associated with loans sold under this program totaled approximately $3.3 billion and $2.8 billion at December 31, 2017 and 2016, respectively. Since many loan commitments, standby letters of credit, and guarantees and indemnification contracts expire without being funded in whole or in part, the contract amounts are not necessarily indicative of future cash flows. The Company utilizes commitments to sell real estate loans to hedge exposure to changes in the fair value of real estate loans held for sale. Such commitments are considered derivatives and along with commitments to originate real estate loans to be held for sale are generally recorded in the consolidated balance sheet at estimated fair market value. The Company occupies certain banking offices and uses certain equipment under noncancelable operating lease agreements expiring at various dates over the next 21 years. Minimum lease payments under noncancelable operating leases are summarized in the following table: (In thousands) Year ending December 31: 2018 $ 92,824 2019 87,298 2020 70,490 2021 54,685 2022 41,953 Later years 82,195 $ 429,445 The Company is contractually obligated to repurchase previously sold residential real estate loans that do not ultimately meet investor sale criteria related to underwriting procedures or loan documentation. When required to do so, the Company may reimburse loan purchasers for losses incurred or may repurchase certain loans. The Company reduces residential mortgage banking revenues by an estimate for losses related to its obligations to loan purchasers. The amount of those charges is based on the volume of loans sold, the level of reimbursement requests received from loan purchasers and estimates of losses that may be associated with previously sold loans. At December 31, 2017, the Company believes that its obligation to loan purchasers was not material to the Company’s consolidated financial position. Prior to M&T’s acquisition of Wilmington Trust Corporation, the Department of Justice (“DOJ”) commenced an investigation of Wilmington Trust Corporation relating to Wilmington Trust Corporation’s financial reporting and securities filings, as well as certain commercial real estate lending relationships involving its subsidiary bank, Wilmington Trust Company, all of which relate to filings and activities occurring prior to the acquisition of Wilmington Trust Corporation by M&T. On January 6, 2016, the U.S. Attorney for the District of Delaware obtained an indictment against Wilmington Trust Corporation relating to alleged conduct that occurred prior to M&T’s acquisition of Wilmington Trust Corporation in May 2011 ( United States v. Wilmington Trust Corp M&T and its subsidiaries are subject in the normal course of business to various pending and threatened legal proceedings and other matters in which claims for monetary damages are asserted. On an on-going basis management, after consultation with legal counsel, assesses the Company’s liabilities and contingencies in connection with such proceedings. For those matters where it is probable that the Company will incur losses and the amounts of the losses can be reasonably estimated, the Company records an expense and corresponding liability in its consolidated financial statements. To the extent the pending or threatened litigation could result in exposure in excess of that liability, the amount of such excess is not currently estimable. Although not considered probable, the range of reasonably possible losses for such matters in the aggregate, beyond the existing recorded liability, was between $0 and $50 million. Although the Company does not believe that the outcome of pending litigations will be material to the Company’s consolidated financial position, it cannot rule out the possibility that such outcomes will be material to the consolidated results of operations for a particular reporting period in the future.

Segment information

Segment information	12 Months Ended
Segment information	Dec. 31, 2017
Segment Reporting [Abstract]
Segment information	22. Segment information Reportable segments have been determined based upon the Company’s internal profitability reporting system, which is organized by strategic business unit. Certain strategic business units have been combined for segment information reporting purposes where the nature of the products and services, the type of customer and the distribution of those products and services are similar. The reportable segments are Business Banking, Commercial Banking, Commercial Real Estate, Discretionary Portfolio, Residential Mortgage Banking and Retail Banking. The financial information of the Company’s segments was compiled utilizing the accounting policies described in note 1 with certain exceptions. The more significant of these exceptions are described herein. The Company allocates interest income or interest expense using a methodology that charges users of funds (assets) interest expense and credits providers of funds (liabilities) with income based on the maturity, prepayment and/or repricing characteristics of the assets and liabilities. A provision for credit losses is allocated to segments in an amount based largely on actual net charge-offs incurred by the segment during the period plus or minus an amount necessary to adjust the segment’s allowance for credit losses due to changes in loan balances. In contrast, the level of the consolidated provision for credit losses is determined using the methodologies described in notes 1 and 5. The net effects of these allocations are recorded in the “All Other” category. Indirect fixed and variable expenses incurred by certain centralized support areas are allocated to segments based on actual usage (for example, volume measurements) and other criteria. Certain types of administrative expenses and bankwide expense accruals (including amortization of core deposit and other intangible assets associated with acquisitions of financial institutions) are generally not allocated to segments. Income taxes are allocated to segments based on the Company’s marginal statutory tax rate adjusted for any tax-exempt income or non-deductible expenses. Equity is allocated to the segments based on regulatory capital requirements and in proportion to an assessment of the inherent risks associated with the business of the segment (including interest, credit and operating risk). The management accounting policies and processes utilized in compiling segment financial information are highly subjective and, unlike financial accounting, are not based on authoritative guidance similar to GAAP. As a result, reported segment results are not necessarily comparable with similar information reported by other financial institutions. Furthermore, changes in management structure or allocation methodologies and procedures may result in changes in reported segment financial data. During 2017, the Company revised its funds transfer pricing allocation related to certain deposit categories. Accordingly, financial information presented herein for 2016 and 2015 has been reclassified to provide segment information on a comparable basis, as noted in the following tables. For the Year Ended December 31, 2016 Net Interest Income as Previously Reported Impact of Changes Net Interest Income as Reclassified Net Income (Loss) as Previously Reported Impact of Changes Net Income (Loss) as Reclassified (In thousands) Business Banking $ 354,333 17,556 371,889 $ 93,346 10,412 103,758 Commercial Banking 785,874 (535 ) 785,339 411,696 (317 ) 411,379 Commercial Real Estate 608,385 — 608,385 350,358 — 350,358 Discretionary Portfolio 345,926 — 345,926 163,538 — 163,538 Residential Mortgage Banking 70,655 (40,846 ) 29,809 79,678 (24,225 ) 55,453 Retail Banking 1,074,125 33,263 1,107,388 274,646 19,727 294,373 All Other 230,589 (9,438 ) 221,151 (58,148 ) (5,597 ) (63,745 ) Total $ 3,469,887 — 3,469,887 $ 1,315,114 — 1,315,114 For the Year Ended December 31, 2015 Net Interest Income as Previously Reported Impact of Changes Net Interest Income as Reclassified Net Income (Loss) as Previously Reported Impact of Changes Net Income (Loss) as Reclassified (In thousands) Business Banking $ 338,855 18,523 357,378 $ 98,758 10,986 109,744 Commercial Banking 753,604 (242 ) 753,362 431,030 (144 ) 430,886 Commercial Real Estate 577,922 — 577,922 340,641 — 340,641 Discretionary Portfolio 97,626 — 97,626 59,272 — 59,272 Residential Mortgage Banking 63,939 (23,970 ) 39,969 88,578 (14,216 ) 74,362 Retail Banking 917,041 34,699 951,740 267,518 20,579 288,097 All Other 93,600 (29,010 ) 64,590 (206,130 ) (17,205 ) (223,335 ) Total $ 2,842,587 — 2,842,587 $ 1,079,667 — 1,079,667 Information about the Company’s segments is presented in the accompanying table. Income statement amounts are in thousands of dollars. Balance sheet amounts are in millions of dollars. For the Years Ended December 31, 2017, 2016 and 2015 Business Banking Commercial Banking Commercial Real Estate Discretionary Portfolio 2017 2016 2015 2017 2016 2015 2017 2016 2015 2017 2016 2015 Net interest income(a) $ 393,948 $ 371,889 $ 357,378 $ 809,301 $ 785,339 $ 753,362 $ 649,378 $ 608,385 $ 577,922 $ 277,095 $ 345,926 $ 97,626 Noninterest income 112,512 108,783 108,195 283,447 274,923 290,142 169,966 179,706 142,948 23,851 26,075 28,114 506,460 480,672 465,573 1,092,748 1,060,262 1,043,504 819,344 788,091 720,870 300,946 372,001 125,740 Provision for credit losses 15,598 12,709 15,513 11,876 34,903 25,089 (7,524 ) (3,447 ) (8,003 ) 31,119 32,925 7,599 Amortization of core deposit and other intangible assets — — — — — — 1,060 — — — — — Depreciation and other amortization 393 404 407 509 520 566 24,410 20,120 19,247 279 472 679 Other noninterest expense 294,493 292,124 264,163 339,936 327,616 288,303 207,493 204,965 169,688 76,021 95,300 49,839 Income (loss) before taxes 195,976 175,435 185,490 740,427 697,223 729,546 593,905 566,453 539,938 193,527 243,304 67,623 Income tax expense (benefit) 80,043 71,677 75,746 303,556 285,844 298,660 229,770 216,095 199,297 58,559 79,766 8,351 Net income (loss) $ 115,933 $ 103,758 $ 109,744 $ 436,871 $ 411,379 $ 430,886 $ 364,135 $ 350,358 $ 340,641 $ 134,968 $ 163,538 $ 59,272 Average total assets (in millions) $ 5,602 $ 5,456 $ 5,339 $ 26,573 $ 25,592 $ 24,143 $ 22,741 $ 21,131 $ 18,827 $ 37,203 $ 40,867 $ 26,648 Capital expenditures (in millions) $ — $ — $ — $ — $ — $ — $ 1 $ — $ — $ — $ — $ — For the Years Ended December 31, 2017, 2016 and 2015 Residential Mortgage Banking Retail Banking All Other Total 2017 2016 2015 2017 2016 2015 2017 2016 2015 2017 2016 2015 Net interest income(a) $ 30,328 $ 29,809 $ 39,969 $ 1,210,066 $ 1,107,388 $ 951,740 $ 410,928 $ 221,151 $ 64,590 $ 3,781,044 $ 3,469,887 $ 2,842,587 Noninterest income 321,589 342,858 336,099 329,833 323,176 324,953 609,945 570,475 594,586 1,851,143 1,825,996 1,825,037 351,917 372,667 376,068 1,539,899 1,430,564 1,276,693 1,020,873 791,626 659,176 5,632,187 5,295,883 4,667,624 Provision for credit losses 1,254 (3,617 ) (5,225 ) 107,412 120,437 72,953 8,265 (3,910 ) 62,074 168,000 190,000 170,000 Amortization of core deposit and other intangible assets — — — — — — 30,306 42,613 26,424 31,366 42,613 26,424 Depreciation and other amortization 32,011 30,264 27,883 38,234 37,657 35,291 69,923 68,541 64,852 165,759 157,978 148,925 Other noninterest expense 247,639 258,141 233,651 758,153 776,123 682,594 1,019,465 892,625 959,345 2,943,200 2,846,894 2,647,583 Income (loss) before taxes 71,013 87,879 119,759 636,100 496,347 485,855 (107,086 ) (208,243 ) (453,519 ) 2,323,862 2,058,398 1,674,692 Income tax expense (benefit) 25,446 32,426 45,397 258,934 201,974 197,758 (40,752 ) (144,498 ) (230,184 ) 915,556 743,284 595,025 Net income (loss) $ 45,567 $ 55,453 $ 74,362 $ 377,166 $ 294,373 $ 288,097 $ (66,334 ) $ (63,745 ) $ (223,335 ) $ 1,408,306 $ 1,315,114 $ 1,079,667 Average total assets (in millions) $ 2,355 $ 2,569 $ 2,918 $ 12,702 $ 11,840 $ 11,035 $ 13,684 $ 16,885 $ 12,870 $ 120,860 $ 124,340 $ 101,780 Capital expenditures (in millions) $ — $ — $ — $ 34 $ 46 $ 14 $ 44 $ 62 $ 68 $ 79 $ 108 $ 82 (a) Net interest income is the difference between actual taxable-equivalent interest earned on assets and interest paid on liabilities by a segment and a funding charge (credit) based on the Company’s internal funds transfer pricing methodology. Segments are charged a cost to fund any assets (e.g. loans) and are paid a funding credit for any funds provided (e.g. deposits). The taxable-equivalent adjustment aggregated $34,570,000 in 2017, $26,962,000 in 2016 and $24,463,000 in 2015 and is eliminated in “All Other” net interest income and income tax expense (benefit). The Business Banking segment provides deposit, lending, cash management and other financial services to small businesses and professionals through the Company’s banking office network and several other delivery channels, including business banking centers, telephone banking, Internet banking and automated teller machines. The Commercial Banking segment provides a wide range of credit products and banking services to middle-market and large commercial customers, mainly within the markets the Company serves. Among the services provided by this segment are commercial lending and leasing, letters of credit, deposit products and cash management services. The Commercial Real Estate segment provides credit services which are secured by various types of multifamily residential and commercial real estate and deposit services to its customers. Activities of this segment include the origination, sales and servicing of commercial real estate loans. Commercial real estate loans held for sale are included in the Commercial Real Estate Segment. The Discretionary Portfolio segment includes securities; residential real estate loans and other assets; short-term and long-term borrowed funds; brokered deposits; and Cayman Islands branch deposits. This segment also provides foreign exchange services to customers. Residential real estate loans obtained in the Hudson City acquisition on November 1, 2015 are included in this segment. The Residential Mortgage Banking segment originates and services residential real estate loans for consumers and sells substantially all originated loans in the secondary market to investors or to the Discretionary Portfolio segment. The segment periodically purchases servicing rights to loans that have been originated by other entities. Residential real estate loans held for sale are included in the Residential Mortgage Banking segment. The Retail Banking segment offers a variety of services to consumers through several delivery channels that include banking offices, automated teller machines, and telephone, mobile and Internet banking. Consumer loans and deposits obtained in the acquisition of Hudson City have been included in this segment. The “All Other” category includes other operating activities of the Company that are not directly attributable to the reported segments; the difference between the provision for credit losses and the calculated provision allocated to the reportable segments; goodwill and core deposit and other intangible assets resulting from acquisitions of financial institutions; merger-related gains and expenses resulting from acquisitions; the net impact of the Company’s internal funds transfer pricing methodology; eliminations of transactions between reportable segments; certain nonrecurring transactions; the residual effects of unallocated support systems and general and administrative expenses; and the impact of interest rate risk management strategies. The amount of intersegment activity eliminated in arriving at consolidated totals was included in the “All Other” category as follows: Year Ended December 31 2017 2016 2015 (In thousands) Revenues $ (43,941 ) $ (48,625 ) $ (48,972 ) Expenses (32,623 ) (40,422 ) (13,332 ) Income taxes (benefit) (4,606 ) (3,338 ) (14,503 ) Net income (loss) (6,712 ) (4,865 ) (21,137 ) The Company conducts substantially all of its operations in the United States. There are no transactions with a single customer that in the aggregate result in revenues that exceed ten percent of consolidated total revenues.

Regulatory matters

Regulatory matters	12 Months Ended
Regulatory matters	Dec. 31, 2017
Banking And Thrift [Abstract]
Regulatory matters	23. Regulatory matters Payment of dividends by M&T’s banking subsidiaries is restricted by various legal and regulatory limitations. Dividends from any banking subsidiary to M&T are limited by the amount of earnings of the banking subsidiary in the current year and the preceding two years. For purposes of this test, at December 31, 2017, approximately $397 Banking regulations prohibit extensions of credit by the subsidiary banks to M&T unless appropriately secured by assets. Securities of affiliates are not eligible as collateral for this purpose. The bank subsidiaries are required to maintain reserves against certain deposit liabilities. During the maintenance periods that included December 31, 2017 and 2016, cash and due from banks and interest-earning deposits at banks included a daily average of $679,401,000 and $594,831,000, respectively, for such purpose. M&T and its subsidiary banks are required to comply with applicable capital adequacy regulations established by the federal banking agencies. Failure to meet minimum capital requirements can result in certain mandatory, and possibly additional discretionary, actions by regulators that, if undertaken, could have a material effect on the Company’s financial statements. Pursuant to the rules in effect as of December 31, 2017, the required minimum and well capitalized capital ratios are as follows: Well Minimum Capitalized ● Common equity Tier 1 ("CET1") to risk-weighted assets 4.5 % 6.5 % ● Tier 1 capital to risk-weighted assets 6.0 % 8.0 % ● Total capital to risk-weighted assets 8.0 % 10.0 % ● Leverage — Tier 1 capital to average total assets, as defined 4.0 % 5.0 % In addition, capital regulations provide for the phase-in of a “capital conservation buffer” composed entirely of CET1 on top of these minimum risk-weighted asset ratios. When fully phased-in on January 1, 2019 the capital conservation buffer will be 2.5%. For 2017 and 2016, the phase-in transition portion of that buffer was 1.25% and .625%, respectively. The capital ratios and amounts of the Company and its banking subsidiaries as of December 31, 2017 and 2016 are presented below: M&T (Consolidated) M&T Bank Wilmington Trust, N.A. (Dollars in thousands) December 31, 2017: Common equity Tier 1 capital Amount $ 10,675,735 $ 9,978,163 $ 529,988 Ratio(a) 10.99 % 10.30 % 48.16 % Tier 1 capital Amount 11,908,166 9,978,163 529,988 Ratio(a) 12.26 % 10.30 % 48.16 % Total capital Amount 14,328,467 12,012,171 534,235 Ratio(a) 14.75 % 12.40 % 48.54 % Leverage Amount 11,908,166 9,978,163 529,988 Ratio(b) 10.31 % 8.68 % 13.03 % December 31, 2016: Common equity Tier 1 capital Amount $ 10,849,642 $ 10,115,688 $ 496,801 Ratio(a) 10.70 % 10.02 % 57.08 % Tier 1 capital Amount 12,083,948 10,115,688 496,801 Ratio(a) 11.92 % 10.02 % 57.08 % Total capital Amount 14,282,492 11,812,114 501,111 Ratio(a) 14.09 % 11.70 % 57.57 % Leverage Amount 12,083,948 10,115,688 496,801 Ratio(b) 9.99 % 8.41 % 15.31 % (a) The ratio of capital to risk-weighted assets, as defined by regulation. (b) The ratio of capital to average assets, as defined by regulation.

Relationship with Bayview Lendi

Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P.	12 Months Ended
	Dec. 31, 2017
Text Block [Abstract]
Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P.	24. Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P. M&T holds a 20% minority interest in Bayview Lending Group LLC (“BLG”), a privately-held commercial mortgage company. M&T recognizes income or loss from BLG using the equity method of accounting. That investment had no remaining carrying value at December 31, 2017 as a result of cumulative losses recognized and cash distributions received. Bayview Financial Holdings, L.P. (together with its affiliates, “Bayview Financial”), a privately-held specialty financial company, is BLG’s majority investor. In addition to their common investment in BLG, the Company and Bayview Financial conduct other business activities with each other. The Company has obtained loan servicing rights for mortgage loans from BLG and Bayview Financial having outstanding principal balances of $3.0 billion and $3.5 billion at December 31, 2017 and 2016, respectively. Revenues from those servicing rights were $17 million, $19 million and $23 million during 2017, 2016 and 2015, respectively. The Company sub-services residential mortgage loans for Bayview Financial having outstanding principal balances of $56.6 billion and $30.4 billion at December 31, 2017 and 2016, respectively. Revenues earned for sub-servicing loans for Bayview Financial were $103 million, $98 million and $115 million in 2017, 2016 and 2015, respectively. In addition, the Company held $136 million and $158 million of mortgage-backed securities in its held-to-maturity portfolio at December 31, 2017 and 2016, respectively, that were securitized by Bayview Financial. In April 2017, the Company provided a loan to Bayview Financial for $100 million at terms consistent with those offered to nonaffiliated customers. That loan was subsequently paid in full in June 2017. Also in June 2017, a new syndicated loan facility was entered into by Bayview Financial for $750 million, of which the Company held $88 million at December 31, 2017.

Parent company financial statem

Parent company financial statements	12 Months Ended
Parent company financial statements	Dec. 31, 2017
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
Parent company financial statements	25. Parent company financial statements Condensed Balance Sheet December 31 2017 2016 (In thousands) Assets Cash in subsidiary bank $ 13,379 $ 15,003 Due from consolidated bank subsidiaries Money-market savings 1,616,147 1,767,184 Current income tax receivable 4,437 3,061 Total due from consolidated bank subsidiaries 1,620,584 1,770,245 Investments in consolidated subsidiaries Banks 14,841,794 15,003,964 Other 253,904 161,201 Investments in unconsolidated subsidiaries (note 19) 23,453 23,643 Investment in Bayview Lending Group LLC — 11,908 Other assets 66,023 71,687 Total assets $ 16,819,137 $ 17,057,651 Liabilities Accrued expenses and other liabilities $ 49,093 $ 54,487 Long-term borrowings 519,225 516,542 Total liabilities 568,318 571,029 Shareholders’ equity 16,250,819 16,486,622 Total liabilities and shareholders’ equity $ 16,819,137 $ 17,057,651 Condensed Statement of Income Year Ended December 31 2017 2016 2015 (In thousands, except per share) Income Dividends from consolidated bank subsidiaries $ 1,540,000 $ 1,930,000 $ 480,000 Equity in earnings of Bayview Lending Group LLC 352 (10,752 ) (14,267 ) Other income 9,493 5,530 2,364 Total income 1,549,845 1,924,778 468,097 Expense Interest on long-term borrowings 21,591 18,963 24,453 Other expense 19,636 21,361 16,793 Total expense 41,227 40,324 41,246 Income before income taxes and equity in undistributed income of subsidiaries 1,508,618 1,884,454 426,851 Income tax credits 26,453 17,247 19,965 Income before equity in undistributed income of subsidiaries 1,535,071 1,901,701 446,816 Equity in undistributed income of subsidiaries Net income of subsidiaries 1,413,235 1,343,413 1,112,851 Less: dividends received (1,540,000 ) (1,930,000 ) (480,000 ) Equity in undistributed income of subsidiaries (126,765 ) (586,587 ) 632,851 Net income $ 1,408,306 $ 1,315,114 $ 1,079,667 Net income per common share Basic $ 8.72 $ 7.80 $ 7.22 Diluted 8.70 7.78 7.18 Condensed Statement of Cash Flows Year Ended December 31 2017 2016 2015 (In thousands) Cash flows from operating activities Net income $ 1,408,306 $ 1,315,114 $ 1,079,667 Adjustments to reconcile net income to net cash provided by operating activities Equity in undistributed income of subsidiaries 126,765 586,587 (632,851 ) Benefit (provision) for deferred income taxes 4,543 (3,157 ) (3,655 ) Net change in accrued income and expense (170 ) 12,898 21,780 Loss (gain) on sale of assets (2,995 ) (2,342 ) 119 Net cash provided by operating activities 1,536,449 1,909,100 465,060 Cash flows from investing activities Proceeds from sales or maturities of investment securities — 51 755 Other, net 12,407 13,619 14,038 Net cash provided by investing activities 12,407 13,670 14,793 Cash flows from financing activities Payments on long-term borrowings — — (322,621 ) Purchases of treasury stock (1,205,905 ) (641,334 ) — Dividends paid — common (457,402 ) (441,891 ) (375,017 ) Dividends paid — preferred (72,734 ) (81,270 ) (81,270 ) Redemption of Series D preferred stock — (500,000 ) — Proceeds from issuance of Series F preferred stock — 495,000 — Other, net 34,524 143,764 76,364 Net cash used by financing activities (1,701,517 ) (1,025,731 ) (702,544 ) Net increase (decrease) in cash and cash equivalents (152,661 ) 897,039 (222,691 ) Cash and cash equivalents at beginning of year 1,782,187 885,148 1,107,839 Cash and cash equivalents at end of year $ 1,629,526 $ 1,782,187 $ 885,148 Supplemental disclosure of cash flow information Interest received during the year $ 2,313 $ 1,931 $ 1,905 Interest paid during the year 18,498 15,918 30,420 Income taxes received during the year 21,740 8,877 16,696

Recent accounting developments

Recent accounting developments	12 Months Ended
Recent accounting developments	Dec. 31, 2017
Accounting Changes And Error Corrections [Abstract]
Recent accounting developments	26. Recent accounting developments The following table provides a description of accounting standards that were adopted by the company in 2017 as well as standards that are not effective that could have an impact to M&T’s consolidated financial statements upon adoption. Standard Description Required date of adoption Effect on consolidated financial statements Standards Adopted in 2017 Improvements to Employee Share-Based Payment Accounting The amended guidance requires that all excess tax benefits and tax deficiencies related to share-based compensation be recognized in income tax expense in the income statement and that such amounts be recognized in the period in which the tax deduction arises or in the period in which an expiration of an award occurs. January The adoption of this guidance resulted in a $22 million reduction of income tax expense for the year ended December 31, 2017 that under previous accounting guidance would have been recognized directly in shareholders’ equity. Simplifying the Transition to Equity Method of Accounting The amended guidance eliminates the requirement that an investor retroactively apply the equity method of accounting as a result of an increase in the level of ownership interest or degree of influence. The amended guidance instead requires the investor to adopt the equity method of accounting as of the date the investment first qualifies for such accounting. January 1, 2017 The adoption of this guidance did not have a material effect on the Company’s consolidated financial position or results of operations. Derivatives and Hedging Amendments One amendment clarifies that a change in the counterparty to a derivative instrument that has been designated as the hedging instrument does not, in and of itself, require dedesignation of that hedging relationship provided that all other hedge accounting criteria continue to be met. A second amendment clarifies the requirements for assessing whether contingent call (put) options that can accelerate the payment of principal on debt instruments are clearly and closely related to their debt hosts. January 1, 2017 The adoption of this guidance did not have a material effect on the Company’s consolidated financial position or results of operations. Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income The amended guidance allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the newly enacted federal corporate income tax rate. The amount of reclassification would be the difference between the historical corporate income tax and the new enacted 21 percent corporate income tax rate. January 1, 2018 Early adoption permitted The Company early adopted the amended guidance following enactment of the Tax Act in 2017. The adoption of this guidance resulted in a $64 million reclassification from AOCI to retained earnings. Standard Description Required date of adoption Effect on consolidated financial statements Standards Not Yet Adopted as of December 31, 2017 Revenue from Contracts with Customers The core principle of the accounting guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. January The Company adopted the revenue recognition guidance effective January 1, 2018, and expects to apply the modified retrospective approach for reporting purposes. A significant amount of the Company’s revenues are derived from net interest income on financial assets and liabilities, which are excluded from the scope of the amended guidance. With respect to noninterest income, under the new guidance credit card interchange revenue will be presented net of rewards expense in other revenues from operations. For the years ended December 31, 2017 and 2016, M&T recognized $13 million and $6 million, respectively, of credit card rewards expense in other costs of operations. The adjustment to beginning retained earnings as well as the impact of any changes in the timing of revenue recognition of noninterest income items within the scope of this guidance will not be material to the Company’s financial position or results of operations. Recognition and Measurement of Financial Assets and Financial Liabilities The amended guidance requires equity investments (excluding those accounted for under the equity method of accounting or those that result in consolidation of the investee) be measured at fair value with changes in fair value recognized in net income, public entities to use the exit price when measuring the fair value of financial instruments for disclosure purposes, and an entity to present separately in other comprehensive income a change in the instrument-specific credit risk when the entity has elected to measure a liability at fair value in accordance with the fair value option. January 1, 2018 The Company held marketable equity securities with a fair value of $101 million in its available-for-sale portfolio at December 31, 2017. Effective January 1, 2018, fair value changes in such equity securities will be recognized in the consolidated statement of income as opposed to AOCI where they had been recognized under previous accounting guidance. Although those securities have historically fluctuated in value, how those securities could change in value in the future is not predictable. Improvements to Accounting for Hedging Activities The amended guidance expands and clarifies hedge accounting for nonfinancial and financial risk components, aligns the recognition and presentation of the effects of the hedging instrument and hedged item in the financial statements, and simplifies the requirements for assessing effectiveness in a hedging relationship. January 1, 2019 Early adoption permitted The Company adopted the amended guidance on January 1, 2018 and does not expect such adoption will have a material impact on its consolidated financial statements. Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost The amended guidance requires the service cost component of the net periodic pension cost and net periodic postretirement benefit cost to be reported in the same line item in the income statement as other compensation costs arising from services rendered by the pertinent employees during the period. The amendments also require that the other components of net benefit costs be presented separately from the service cost component. January 1, 2018 The Company adopted the new reporting requirements effective January 1, 2018. The Company has previously reported all of its net periodic pension and postretirement benefit costs in salaries and employee benefits within the consolidated statement of income. Information about net periodic pension and postretirement benefit costs that were not service cost-related is included in note 12. Scope of Modification Accounting for Share-Based Payment Awards The amended guidance addresses which changes to the terms and conditions of a share-based payment award require an entity to apply modification accounting. January 1, 2018 The Company adopted the amended guidance on January 1, 2018. The guidance is to be applied on a prospective basis for awards modified on or after the adoption date. Restricted Cash The amended guidance requires that restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. In addition, when cash, cash equivalents, and restricted cash or restricted cash equivalents are presented in more than one line item within the statement of financial position, the line items and amounts must be presented on the face of the statement of cash flows or disclosed in the notes to the financial statements. Information about the nature of restrictions on an entity’s cash and cash equivalents must also be disclosed. January 1, 2018 The guidance will be applied using a retrospective transition method beginning with first quarter 2018 reporting. Classification of Certain Cash Receipts and Cash Payments This amendment provides clarifying guidance for classifying cash inflows or outflows on the statement of cash flows where current guidance is unclear or silent. January 1, 2018 The guidance will be applied using a retrospective transition method beginning with first quarter 2018 reporting. Clarifying the Definition of a Business The amended guidance clarifies the definition of a business for purposes of evaluating whether transactions would be accounted for as acquisitions (or disposals) of assets or businesses. January 1, 2018 The guidance should be applied using a prospective transition method. The Company does not expect the guidance to have a material impact on its consolidated financial statements. Leases The new guidance requires lessees to record a right-of-use asset and a lease liability for all leases with a term greater than 12 months. While the guidance requires all leases to be recognized in the balance sheet, there continues to be a differentiation between finance leases and operating leases for purposes of income statement recognition and cash flow statement presentation. For finance leases, interest on the lease liability and amortization of the right-of-use asset will be recognized separately in the statement of income. Repayments of principal on those lease liabilities will be classified within financing activities and payments of interest on the lease liability will be classified within operating activities in the statement of cash flows. For operating leases, a single lease cost is recognized in the statement of income and allocated over the lease term, generally on a straight-line basis. All cash payments are presented within operating activities in the statement of cash flows. The accounting applied by lessors is largely unchanged from existing GAAP, however, the guidance eliminates the accounting model for leveraged leases for leases that commence after the effective date of the guidance. January 1, 2019 Early adoption permitted The Company occupies certain banking offices and uses certain equipment under noncancelable operating lease agreements which currently are not reflected in its consolidated balance sheet. Upon adoption of the guidance, the Company expects to report increased assets and increased liabilities as a result of recognizing right-of-use assets and lease liabilities on its consolidated balance sheet. The Company was committed to $429 million of minimum lease payments under noncancelable operating lease agreements at December 31, 2017. The Company does not expect the new guidance will have a material impact to its consolidated statement of income. Premium Amortization on Purchased Callable Debt Securities The amended guidance requires the premium on callable debt securities to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. January 1, 2019 Early adoption permitted The amendments should be applied on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company does not expect the guidance to have a material impact on its consolidated financial statements. Measurement of Credit Losses on Financial Instruments The amended guidance replaces the current incurred loss model for determining the allowance for credit losses. The guidance requires financial assets measured at amortized cost to be presented at the net amount expected to be collected. The allowance for credit losses will represent a valuation account that is deducted from the amortized cost basis of the financial assets to present their net carrying value at the amount expected to be collected. The income statement will reflect the measurement of credit losses for newly recognized financial assets as well as expected increases or decreases of expected credit losses that have taken place during the period. When determining the allowance, expected credit losses over the contractual term of the financial asset(s) (taking into account prepayments) will be estimated considering relevant information about past events, current conditions, and reasonable and supportable forecasts that affect the collectibility of the reported amount. The amended guidance also requires recording an allowance for credit losses for purchased financial assets with a more-than-insignificant amount of credit deterioration since origination. The initial allowance for these assets will be added to the purchase price at acquisition rather than being reported as an expense. Subsequent changes in the allowance will be recorded through the income statement as an expense adjustment. In addition, the amended guidance requires credit losses relating to available-for-sale debt securities to be recorded through an allowance for credit losses. The calculation of credit losses for available-for-sale securities will be similar to how it is determined under existing guidance. January 1, 2020 Early adoption permitted as of January 1, 2019 The Company is assessing the new guidance to determine what modifications to existing credit estimation processes may be required. The Company expects that the new guidance will result in an increase in its allowance for credit losses as a result of considering credit losses over the expected life of its loan portfolios. Increases in the level of allowances will also reflect new requirements to include the nonaccretable principal difference on purchased credit impaired loans and estimated credit losses on investment securities classified as held-to-maturity, if any. The Company is still evaluating the extent of the increase to the allowance for credit losses and the impact to its financial statements. Simplifying the Test for Goodwill Impairment The amended guidance eliminates step 2 from the goodwill impairment test. January 1, 2020 Early adoption permitted The amendments should be applied using a prospective transition method. The Company does not expect the guidance will have a material impact on its consolidated financial statements, unless at some point in the future one of its reporting units were to fail step 1 of the goodwill impairment test.

Significant accounting polici35

Significant accounting policies (Policies)	12 Months Ended
Significant accounting policies (Policies)	Dec. 31, 2017
Accounting Policies [Abstract]
Consolidation	Consolidation The consolidated financial statements include M&T and all of its subsidiaries. All significant intercompany accounts and transactions of consolidated subsidiaries have been eliminated in consolidation. The financial statements of M&T included in note 25 report investments in subsidiaries under the equity method. Information about some limited purpose entities that are affiliates of the Company but are not included in the consolidated financial statements appears in note 19.
Consolidated Statement of Cash Flows	Consolidated Statement of Cash Flows For purposes of this statement, cash and due from banks and federal funds sold are considered cash and cash equivalents.
Securities purchased under agreements to resell and securities sold under agreements to repurchase	Securities purchased under agreements to resell and securities sold under agreements to repurchase Securities purchased under agreements to resell and securities sold under agreements to repurchase are treated as collateralized financing transactions and are recorded at amounts equal to the cash or other consideration exchanged. It is generally the Company’s policy to take possession of collateral pledged to secure agreements to resell.
Trading account	Trading account Financial instruments used for trading purposes are stated at fair value. Realized gains and losses and unrealized changes in fair value of financial instruments utilized in trading activities are included in “trading account and foreign exchange gains” in the consolidated statement of income.
Investment securities	Investment securities Investments in debt securities are classified as held to maturity and stated at amortized cost when management has the positive intent and ability to hold such securities to maturity. Investments in other debt securities and equity securities having readily determinable fair values are classified as available for sale and stated at estimated fair value. Amortization of premiums and accretion of discounts for investment securities available for sale and held to maturity are included in interest income. Other securities are stated at cost and include stock of the Federal Reserve Bank of New York and the Federal Home Loan Bank (“FHLB”) of New York. Individual securities are written down through a charge to earnings when declines in value below the cost basis of a security are considered to be other than temporary. In cases where fair value is less than amortized cost and the Company intends to sell a debt security, it is more likely than not to be required to sell a debt security before recovery of its amortized cost basis, or the Company does not expect to recover the entire amortized cost basis of a debt security, an other-than-temporary impairment is considered to have occurred. If the Company intends to sell the debt security or more likely than not will be required to sell the security before recovery of its amortized cost basis, the other-than-temporary impairment is recognized in earnings equal to the entire difference between the debt security’s amortized cost basis and its fair value. If the Company does not expect to recover the entire amortized cost basis of the security, the Company does not intend to sell the security and it is not more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis, the other-than-temporary impairment is separated into (a) the amount representing the credit loss and (b) the amount related to all other factors. The amount of the other-than-temporary impairment related to the credit loss is recognized in earnings while the amount related to other factors is recognized in other comprehensive income, net of applicable taxes. Subsequently, the Company accounts for the other-than-temporarily impaired debt security as if the security had been purchased on the measurement date of the other-than-temporary impairment at an amortized cost basis equal to the previous amortized cost basis less the other-than-temporary impairment recognized in earnings. Realized gains and losses on the sales of investment securities are determined using the specific identification method.
Loans and leases	Loans and leases The Company’s accounting methods for loans depends on whether the loans were originated by the Company or were acquired in a business combination. Originated loans and leases Interest income on loans is accrued on a level yield method. Loans are placed on nonaccrual status and previously accrued interest thereon is charged against income when principal or interest is delinquent 90 days, unless management determines that the loan status clearly warrants other treatment. Nonaccrual commercial loans and commercial real estate loans are returned to accrual status when borrowers have demonstrated an ability to repay their loans and there are no delinquent principal and interest payments. Consumer loans not secured by residential real estate are returned to accrual status when all past due principal and interest payments have been paid by the borrower. Loans secured by residential real estate are returned to accrual status when they are deemed to have an insignificant delay in payments of 90 days or less. Loan balances are charged off when it becomes evident that such balances are not fully collectible. For commercial loans and commercial real estate loans, charge-offs are recognized after an assessment by credit personnel of the capacity and willingness of the borrower to repay, the estimated value of any collateral, and any other potential sources of repayment. A charge-off is recognized when, after such assessment, it becomes evident that the loan balance is not fully collectible. For loans secured by residential real estate, the excess of the loan balances over the net realizable value of the property collateralizing the loan is charged-off when the loan becomes 150 days delinquent. Consumer loans are generally charged-off when the loans are 91 to 180 days past due, depending on whether the loan is collateralized and the status of repossession activities with respect to such collateral. Loan fees and certain direct loan origination costs are deferred and recognized as an interest yield adjustment over the life of the loan. Net deferred fees have been included in unearned discount as a reduction of loans outstanding. Commitments to sell real estate loans are utilized by the Company to hedge the exposure to changes in fair value of real estate loans held for sale. The carrying value of hedged real estate loans held for sale recorded in the consolidated balance sheet includes changes in estimated fair market value during the hedge period, typically from the date of close through the sale date. Valuation adjustments made on these loans and commitments are included in “mortgage banking revenues.” Except for consumer and residential mortgage loans that are considered smaller balance homogenous loans and are evaluated collectively, the Company considers a loan to be impaired for purposes of applying GAAP when, based on current information and events, it is probable that the Company will be unable to collect all amounts according to the contractual terms of the loan agreement or the loan is delinquent 90 days. Regardless of loan type, the Company considers a loan to be impaired if it qualifies as a troubled debt restructuring. Impaired loans are classified as either nonaccrual or as loans renegotiated at below market rates which continue to accrue interest, provided that a credit assessment of the borrower’s financial condition results in an expectation of full repayment under the modified contractual terms. Certain loans greater than 90 days delinquent are not considered impaired if they are well-secured and in the process of collection. Loans less than 90 days delinquent are deemed to have an insignificant delay in payment and are generally not considered impaired. Impairment of a loan is measured based on the present value of expected future cash flows discounted at the loan’s effective interest rate, the loan’s observable market price, or the fair value of collateral if the loan is collateral-dependent. Interest received on impaired loans placed on nonaccrual status is generally applied to reduce the carrying value of the loan or, if principal is considered fully collectible, recognized as interest income. Residual value estimates for commercial leases are generally determined through internal or external reviews of the leased property. The Company reviews commercial lease residual values at least annually and recognizes residual value impairments deemed to be other than temporary. Loans and leases acquired in a business combination Loans acquired in a business combination subsequent to December 31, 2008 are initially recorded at fair value with no carry-over of an acquired entity’s previously established allowance for credit losses. Purchased impaired loans represent specifically identified loans with evidence of credit deterioration for which it was probable at acquisition that the Company would be unable to collect all contractual principal and interest payments. For purchased impaired loans and other loans acquired at a discount that was, in part, attributable to credit quality, the excess of cash flows expected at acquisition over the estimated fair value of acquired loans is recognized as interest income over the remaining lives of the loans. Subsequent decreases in the expected principal cash flows require the Company to evaluate the need for additions to the Company’s allowance for credit losses. Subsequent improvements in expected cash flows result first in the recovery of any related allowance for credit losses and then in recognition of additional interest income over the then-remaining lives of the loans. For all other acquired loans, the difference between the fair value and outstanding principal balance of the loans is recognized as an adjustment to interest income over the lives of those loans. Those loans are then accounted for in a manner that is similar to originated loans.
Allowance for credit losses	Allowance for credit losses The allowance for credit losses represents, in management’s judgment, the amount of losses inherent in the loan and lease portfolio as of the balance sheet date. The allowance is determined by management’s evaluation of the loan and lease portfolio based on such factors as the differing economic risks associated with each loan category, the current financial condition of specific borrowers, the economic environment in which borrowers operate, the level of delinquent loans, the value of any collateral and, where applicable, the existence of any guarantees or indemnifications. The effects of probable decreases in expected principal cash flows on loans acquired at a discount are also considered in the establishment of the allowance for credit losses.
Assets taken in foreclosure of defaulted loans	Assets taken in foreclosure of defaulted loans Assets taken in foreclosure of defaulted loans are primarily comprised of commercial and residential real property and are included in “other assets” in the consolidated balance sheet. An in-substance repossession or foreclosure occurs and a creditor is considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan upon either (1) the creditor obtaining legal title to the residential real estate property upon completion of a foreclosure or (2) the borrower conveying all interest in the residential real estate property to the creditor to satisfy that loan through completion of a deed in lieu of foreclosure or through a similar legal agreement. Upon acquisition of assets taken in satisfaction of a defaulted loan, the excess of the remaining loan balance over the asset’s estimated fair value less costs to sell is charged-off against the allowance for credit losses. Subsequent declines in value of the assets are recognized as “other costs of operations” in the consolidated statement of income.
Premises and equipment	Premises and equipment Premises and equipment are stated at cost less accumulated depreciation. Depreciation expense is computed principally using the straight-line method over the estimated useful lives of the assets.
Capitalized servicing rights	Capitalized servicing rights Capitalized servicing assets are included in “other assets” in the consolidated balance sheet. Separately recognized servicing assets are initially measured at fair value. The Company uses the amortization method to subsequently measure servicing assets. Under that method, capitalized servicing assets are charged to expense in proportion to and over the period of estimated net servicing income. To estimate the fair value of servicing rights, the Company considers market prices for similar assets and the present value of expected future cash flows associated with the servicing rights calculated using assumptions that market participants would use in estimating future servicing income and expense. Such assumptions include estimates of the cost of servicing loans, loan default rates, an appropriate discount rate, and prepayment speeds. For purposes of evaluating and measuring impairment of capitalized servicing rights, the Company stratifies such assets based on the predominant risk characteristics of the underlying financial instruments that are expected to have the most impact on projected prepayments, cost of servicing and other factors affecting future cash flows associated with the servicing rights. Such factors may include financial asset or loan type, note rate and term. The amount of impairment recognized is the amount by which the carrying value of the capitalized servicing rights for a stratum exceeds estimated fair value. Impairment is recognized through a valuation allowance.
Sales and securitizations of financial assets	Sales and securitizations of financial assets Transfers of financial assets for which the Company has surrendered control of the financial assets are accounted for as sales. Interests in a sale of financial assets that continue to be held by the Company, including servicing rights, are measured at fair value. The fair values of retained debt securities are generally determined through reference to independent pricing information. The fair values of retained servicing rights and any other retained interests are determined based on the present value of expected future cash flows associated with those interests and by reference to market prices for similar assets. Securitization structures typically require the use of special-purpose trusts that are considered variable interest entities. A variable interest entity is included in the consolidated financial statements if the Company has the power to direct the activities that most significantly impact the variable interest entity’s economic performance and has the obligation to absorb losses or the right to receive benefits of the variable interest entity that could potentially be significant to that entity.
Goodwill and core deposit and other intangible assets	Goodwill and core deposit and other intangible assets Goodwill represents the excess of the cost of an acquired entity over the fair value of the identifiable net assets acquired. Goodwill is not amortized, but rather is tested for impairment at least annually at the reporting unit level, which is either at the same level or one level below an operating segment. Other acquired intangible assets with finite lives, such as core deposit intangibles, are initially recorded at estimated fair value and are amortized over their estimated lives. Core deposit and other intangible assets are generally amortized using accelerated methods over estimated useful lives of five to ten years. The Company periodically assesses whether events or changes in circumstances indicate that the carrying amounts of core deposit and other intangible assets may be impaired.
Derivative financial instruments	Derivative financial instruments The Company accounts for derivative financial instruments at fair value. If certain conditions are met, a derivative may be specifically designated as (a) a hedge of the exposure to changes in the fair value of a recognized asset or liability or an unrecognized firm commitment, (b) a hedge of the exposure to variable cash flows of a forecasted transaction or (c) a hedge of the foreign currency exposure of a net investment in a foreign operation, an unrecognized firm commitment, an available-for-sale security, or a foreign currency denominated forecasted transaction. The Company utilizes interest rate swap agreements as part of the management of interest rate risk to modify the repricing characteristics of certain portions of its portfolios of earning assets and interest-bearing liabilities. For such agreements, amounts receivable or payable are recognized as accrued under the terms of the agreement and the net differential is recorded as an adjustment to interest income or expense of the related asset or liability. Interest rate swap agreements may be designated as either fair value hedges or cash flow hedges. In a fair value hedge, the fair values of the interest rate swap agreements and changes in the fair values of the hedged items are recorded in the Company’s consolidated balance sheet with the corresponding gain or loss recognized in current earnings. The difference between changes in the fair values of interest rate swap agreements and the hedged items represents hedge ineffectiveness and is recorded in “other revenues from operations” in the consolidated statement of income. In a cash flow hedge, the effective portion of the derivative’s unrealized gain or loss is initially recorded as a component of other comprehensive income and subsequently reclassified into earnings when the forecasted transaction affects earnings. The ineffective portion of the unrealized gain or loss is reported in “other revenues from operations” immediately. The Company utilizes commitments to sell real estate loans to hedge the exposure to changes in the fair value of real estate loans held for sale. Commitments to originate real estate loans to be held for sale and commitments to sell real estate loans are generally recorded in the consolidated balance sheet at estimated fair value. Derivative instruments not related to mortgage banking activities, including financial futures commitments and interest rate swap agreements, that do not satisfy the hedge accounting requirements are recorded at fair value and are generally classified as trading account assets or liabilities with resultant changes in fair value being recognized in “trading account and foreign exchange gains” in the consolidated statement of income.
Stock-based compensation	Stock-based compensation Stock-based compensation expense is recognized over the vesting period of the stock-based grant based on the estimated grant date value of the stock-based compensation, except that the recognition of compensation costs is accelerated for stock-based awards granted to retirement-eligible employees and employees who will become retirement-eligible prior to full vesting of the award because the Company’s incentive compensation plan allows for vesting at the time an employee retires. As discussed in note 26 herein, effective January 2017 the Company adopted amended accounting guidance which requires excess tax benefits or deficiencies associated with stock-based compensation be recognized in income tax expense. Previously, tax effects resulting from changes in M&T’s share price were recorded through shareholders’ equity.
Income taxes	Income taxes Deferred tax assets and liabilities are recognized for the future tax effects attributable to differences between the financial statement value of existing assets and liabilities and their respective tax bases and carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates and laws. The Company evaluates uncertain tax positions using the two-step process required by GAAP. The first step requires a determination of whether it is more likely than not that a tax position will be sustained upon examination, including resolution of any related appeals or litigation processes, based on the technical merits of the position. Under the second step, a tax position that meets the more-likely-than-not recognition threshold is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. The Company accounts for its investments in qualified affordable housing projects using the proportional amortization method. Under that method, the Company amortizes the initial cost of the investment in proportion to the tax credits and other tax benefits received and recognizes the net investment performance in the income statement as a component of income tax expense.
Earnings per common share	Earnings per common share Basic earnings per common share exclude dilution and are computed by dividing income available to common shareholders by the weighted-average number of common shares outstanding (exclusive of shares represented by the unvested portion of restricted stock and restricted stock unit grants) and common shares issuable under deferred compensation arrangements during the period. Diluted earnings per common share reflect shares represented by the unvested portion of restricted stock and restricted stock unit grants and the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock or resulted in the issuance of common stock that then shared in earnings. Proceeds assumed to have been received on such exercise or conversion are assumed to be used to purchase shares of M&T common stock at the average market price during the period, as required by the “treasury stock method” of accounting. GAAP requires that unvested share-based payment awards that contain nonforfeitable rights to dividends or dividend equivalents (whether paid or unpaid) shall be considered participating securities and shall be included in the computation of earnings per common share pursuant to the two-class method. The Company has issued stock-based compensation awards in the form of restricted stock and restricted stock units that contain such rights and, accordingly, the Company’s earnings per common share are calculated using the two-class method.
Treasury stock	Treasury stock Repurchases of shares of M&T common stock are recorded at cost as a reduction of shareholders’ equity. Reissuances of shares of treasury stock are recorded at average cost.

Acquisition and divestiture (Ta

Acquisition and divestiture (Tables)	12 Months Ended
Acquisition and divestiture (Tables)	Dec. 31, 2017
Business Combinations [Abstract]
Pro Forma Information	Actual Since Acquisition Pro Forma Through Year Ended December 31, 2015 December 31, 2015 (In thousands) Total revenues(a) $ 111,168 $ 5,132,662 Net income (loss) (21,175 ) 1,011,463 (a) Represents net interest income plus other income.
Summary of Merger-Related Expenses	A summary of merger-related expenses included in the consolidated statement of income for the years ended December 31, 2016 and 2015 follows: 2016 2015 (In thousands) Salaries and employee benefits $ 5,334 $ 51,287 Equipment and net occupancy 1,278 3 Outside data processing and software 1,067 785 Advertising and marketing 10,522 79 Printing, postage and supplies 1,482 504 Other costs of operations 16,072 23,318 Other expense 35,755 75,976 Provision for credit losses — 21,000 Total $ 35,755 $ 96,976

Investment securities (Tables)

Investment securities (Tables)	12 Months Ended
Investment securities (Tables)	Dec. 31, 2017
Investments Debt And Equity Securities [Abstract]
Amortized Cost and Estimated Fair Value of Investment Securities	The amortized cost and estimated fair value of investment securities were as follows: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value (In thousands) December 31, 2017 Investment securities available for sale: U.S. Treasury and federal agencies $ 1,965,665 $ — $ 18,178 $ 1,947,487 Obligations of states and political subdivisions 2,555 36 2 2,589 Mortgage-backed securities: Government issued or guaranteed 8,755,482 59,497 98,587 8,716,392 Privately issued 28 — — 28 Other debt securities 136,905 2,402 10,475 128,832 Equity securities 78,161 23,219 424 100,956 10,938,796 85,154 127,666 10,896,284 Investment securities held to maturity: Obligations of states and political subdivisions 24,562 109 49 24,622 Mortgage-backed securities: Government issued or guaranteed 3,187,953 27,236 13,746 3,201,443 Privately issued 135,688 2,574 27,575 110,687 Other debt securities 5,010 — — 5,010 3,353,213 29,919 41,370 3,341,762 Other securities 415,028 — — 415,028 Total $ 14,707,037 $ 115,073 $ 169,036 $ 14,653,074 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value (In thousands) December 31, 2016 Investment securities available for sale: U.S. Treasury and federal agencies $ 1,912,110 $ 386 $ 9,952 $ 1,902,544 Obligations of states and political subdivisions 3,570 77 6 3,641 Mortgage-backed securities: Government issued or guaranteed 10,980,507 88,343 113,989 10,954,861 Privately issued 45 — 1 44 Other debt securities 134,105 1,407 16,996 118,516 Equity securities 307,964 45,073 571 352,466 13,338,301 135,286 141,515 13,332,072 Investment securities held to maturity: Obligations of states and political subdivisions 60,858 267 224 60,901 Mortgage-backed securities: Government issued or guaranteed 2,233,173 37,498 7,374 2,263,297 Privately issued 157,704 897 37,120 121,481 Other debt securities 5,543 — — 5,543 2,457,278 38,662 44,718 2,451,222 Other securities 461,118 — — 461,118 Total $ 16,256,697 $ 173,948 $ 186,233 $ 16,244,412
Investment Ratings of All Privately Issued Mortgage-Backed Securities and Other Debt Securities	As of December 31, 2017, the latest available investment ratings of all obligations of states and political subdivisions, privately issued mortgage-backed securities and other debt securities were: Average Credit Rating of Fair Value Amount Amortized Cost Estimated Fair Value A or Better BBB BB B or Less Not Rated (In thousands) Obligations of states and political subdivisions $ 27,117 $ 27,211 $ 15,874 $ — $ — $ — $ 11,337 Privately issued mortgage-backed securities 135,716 110,715 23,459 16 — 87,233 7 Other debt securities 141,915 133,842 6,980 61,054 32,684 — 33,124 Total $ 304,748 $ 271,768 $ 46,313 $ 61,070 $ 32,684 $ 87,233 $ 44,468
Amortized Cost and Estimated Fair Value of Collateralized Mortgage Obligations	The amortized cost and estimated fair value of collateralized mortgage obligations included in mortgage-backed securities were as follows: December 31 2017 2016 (In thousands) Collateralized mortgage obligations: Amortized cost $ 138,527 $ 162,027 Estimated fair value 113,516 125,848
Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity	At December 31, 2017, the amortized cost and estimated fair value of debt securities by contractual maturity were as follows: Amortized Cost Estimated Fair Value (In thousands) Debt securities available for sale: Due in one year or less $ 616,908 613,866 Due after one year through five years 1,356,410 1,341,344 Due after five years through ten years 72,642 72,580 Due after ten years 59,165 51,118 2,105,125 2,078,908 Mortgage-backed securities available for sale 8,755,510 8,716,420 $ 10,860,635 10,795,328 Debt securities held to maturity: Due in one year or less $ 14,622 14,656 Due after one year through five years 9,844 9,865 Due after five years through ten years 96 101 Due after ten years 5,010 5,010 29,572 29,632 Mortgage-backed securities held to maturity 3,323,641 3,312,130 $ 3,353,213 3,341,762
Investment Securities in Continuous Unrealized Loss Position	A summary of investment securities that as of December 31, 2017 and 2016 had been in a continuous unrealized loss position for less than twelve months and those that had been in a continuous unrealized loss position for twelve months or longer follows: Less Than 12 Months 12 Months or More Fair Value Unrealized Losses Fair Value Unrealized Losses (In thousands) December 31, 2017 Investment securities available for sale: U.S. Treasury and federal agencies $ 278,132 (1,761 ) 1,669,355 (16,417 ) Obligations of states and political subdivisions — — 474 (2 ) Mortgage-backed securities: Government issued or guaranteed 2,106,142 (13,695 ) 3,138,841 (84,892 ) Other debt securities 3,067 (26 ) 61,159 (10,449 ) Equity securities — — 18,162 (424 ) 2,387,341 (15,482 ) 4,887,991 (112,184 ) Investment securities held to maturity: Obligations of states and political subdivisions 2,954 (4 ) 6,110 (45 ) Mortgage-backed securities: Government issued or guaranteed 1,331,759 (7,036 ) 265,695 (6,710 ) Privately issued 5,061 (1,216 ) 55,255 (26,359 ) 1,339,774 (8,256 ) 327,060 (33,114 ) Total $ 3,727,115 (23,738 ) 5,215,051 (145,298 ) December 31, 2016 Investment securities available for sale: U.S. Treasury and federal agencies $ 1,710,241 (9,950 ) 2,295 (2 ) Obligations of states and political subdivisions — — 593 (6 ) Mortgage-backed securities: Government issued or guaranteed 6,730,829 (113,374 ) 81,003 (615 ) Privately issued — — 27 (1 ) Other debt securities 100 (1 ) 85,400 (16,995 ) Equity securities 17,776 (422 ) 151 (149 ) 8,458,946 (123,747 ) 169,469 (17,768 ) Investment securities held to maturity: Obligations of states and political subdivisions 17,988 (126 ) 11,891 (98 ) Mortgage-backed securities: Government issued or guaranteed 618,832 (6,842 ) 17,481 (532 ) Privately issued 17,911 (1,222 ) 57,016 (35,898 ) 654,731 (8,190 ) 86,388 (36,528 ) Total $ 9,113,677 (131,937 ) 255,857 (54,296 )

Loans and leases (Tables)

Loans and leases (Tables)	12 Months Ended
Loans and leases (Tables)	Dec. 31, 2017
Receivables [Abstract]
Total Loans and Leases Outstanding	Total loans and leases outstanding were comprised of the following: December 31 2017 2016 (In thousands) Loans Commercial, financial, etc. $ 20,474,696 $ 21,351,119 Real estate: Residential 19,619,259 22,584,141 Commercial 25,345,779 25,550,057 Construction 8,125,925 8,066,756 Consumer 13,251,665 12,130,094 Total loans 86,817,324 89,682,167 Leases Commercial 1,425,562 1,419,510 Total loans and leases 88,242,886 91,101,677 Less: unearned discount (253,903 ) (248,261 ) Total loans and leases, net of unearned discount $ 87,988,983 $ 90,853,416
Summary of Current, Past Due and Nonaccrual Loans	A summary of current, past due and nonaccrual loans as of December 31, 2017 and 2016 follows: Current 30-89 Days Past Due Accruing Loans Past Due 90 Days or More (a) Accruing Loans Acquired at a Discount Past Due 90 days or More (b) Purchased Impaired (c) Nonaccrual Total (In thousands) December 31, 2017 Commercial, financial, leasing, etc. $ 21,332,234 167,756 1,322 327 21 240,991 $ 21,742,651 Real estate: Commercial 24,910,381 166,305 4,444 6,016 16,815 184,982 25,288,943 Residential builder and developer 1,618,973 5,159 — — 1,135 6,451 1,631,718 Other commercial construction 6,407,451 23,467 — — 4,706 10,088 6,445,712 Residential 15,376,759 474,372 233,437 7,582 282,102 235,834 16,610,086 Residential — limited documentation 2,718,019 83,898 — — 105,236 96,105 3,003,258 Consumer: Home equity lines and loans 5,171,345 38,546 — 9,391 — 74,500 5,293,782 Automobile 3,441,371 78,511 — — — 23,781 3,543,663 Other 4,349,071 40,929 5,202 24,102 — 9,866 4,429,170 Total $ 85,325,604 1,078,943 244,405 47,418 410,015 882,598 $ 87,988,983 December 31, 2016 Commercial, financial, leasing, etc. $ 22,287,857 53,503 6,195 417 641 261,434 $ 22,610,047 Real estate: Commercial 25,076,684 183,531 7,054 12,870 31,404 176,201 25,487,744 Residential builder and developer 1,884,989 4,667 5 1,952 14,006 16,707 1,922,326 Other commercial construction 5,985,118 77,701 922 198 14,274 18,111 6,096,324 Residential 17,631,377 485,468 281,298 11,537 378,549 229,242 19,017,471 Residential — limited documentation 3,239,344 88,366 — — 139,158 106,573 3,573,441 Consumer: Home equity lines and loans 5,502,091 44,565 — 12,678 — 81,815 5,641,149 Automobile 2,869,232 56,158 — 1 — 18,674 2,944,065 Other 3,491,629 31,286 5,185 21,491 — 11,258 3,560,849 Total $ 87,968,321 1,025,245 300,659 61,144 578,032 920,015 $ 90,853,416 (a) Excludes loans acquired at a discount. (b) Loans acquired at a discount that were recorded at fair value at acquisition date. This category does not include purchased impaired loans that are presented separately. (c) Accruing loans acquired at a discount that were impaired at acquisition date and recorded at fair value.
Outstanding Principal Balance and Carrying Amount of Loans and Included in Consolidated Balance Sheet	The outstanding principal balance and the carrying amount of loans acquired at a discount that were recorded at fair value at the acquisition date and included in the consolidated balance sheet were as follows: December 31 2017 2016 (In thousands) Outstanding principal balance $ 1,394,188 $ 2,311,699 Carrying amount: Commercial, financial, leasing, etc. 31,105 59,928 Commercial real estate 228,054 456,820 Residential real estate 620,827 799,802 Consumer 123,413 487,721 $ 1,003,399 $ 1,804,271
Summary of Changes in Accretable Yield for Acquired Loans	A summary of changes in the accretable yield for loans acquired at a discount for the years ended December 31, 2017, 2016 and 2015 follows: For the Year Ended December 31, 2017 2016 2015 Purchased Other Purchased Other Purchased Other Impaired Acquired Impaired Acquired Impaired Acquired (In thousands) Balance at beginning of period $ 154,233 $ 201,153 $ 184,618 $ 296,434 $ 76,518 $ 397,379 Additions — — — — 117,251 — Interest income (47,452 ) (82,605 ) (52,769 ) (123,044 ) (28,551 ) (158,260 ) Reclassifications from nonaccretable balance 51,137 16,437 22,384 22,677 19,400 49,930 Other(a) — (1,823 ) — 5,086 — 7,385 Balance at end of period $ 157,918 $ 133,162 $ 154,233 $ 201,153 $ 184,618 $ 296,434 (a) Other changes in expected cash flows including changes in interest rates and prepayment assumptions.
Loan Modification Activities that were Considered Troubled Debt Restructurings	The tables that follow summarize the Company’s loan modification activities that were considered troubled debt restructurings for the years ended December 31, 2017, 2016 and 2015: Post-modification (a) Number Pre- modification recorded investment Principal Deferral Other Combination of Concession Types Total Year Ended December 31, 2017 (Dollars in thousands) Commercial, financial, leasing, etc. 217 $ 111,036 $ 25,051 $ 6,459 $ 57,153 $ 88,663 Real estate: Commercial 83 44,924 17,039 868 22,975 40,882 Residential builder and developer 3 12,291 — — 10,879 10,879 Other commercial construction 2 168 168 — — 168 Residential 141 31,827 16,633 — 17,974 34,607 Residential — limited documentation 20 4,230 911 — 3,661 4,572 Consumer: Home equity lines and loans 110 10,049 1,137 491 8,585 10,213 Automobile 69 1,378 1,203 — 175 1,378 Other 9 160 160 — — 160 Total 654 $ 216,063 $ 62,302 $ 7,818 $ 121,402 $ 191,522 Year Ended December 31, 2016 Commercial, financial, leasing, etc. 164 $ 154,093 $ 102,446 $ — $ 41,673 $ 144,119 Real estate: Commercial 81 44,870 23,558 4,576 15,603 43,737 Residential builder and developer 6 39,660 22,958 — 15,123 38,081 Other commercial construction 3 3,113 250 — 2,782 3,032 Residential 119 20,057 11,771 — 9,367 21,138 Residential — limited documentation 21 3,560 1,047 — 2,917 3,964 Consumer: Home equity lines and loans 103 11,870 761 — 11,110 11,871 Automobile 163 1,264 1,124 55 85 1,264 Other 79 1,209 968 45 196 1,209 Total 739 $ 279,696 $ 164,883 $ 4,676 $ 98,856 $ 268,415 Post-modification (a) Number Pre- modification recorded investment Principal Deferral Other Combination of Concession Types Total Year Ended December 31, 2015 (Dollars in thousands) Commercial, financial, leasing, etc. 127 $ 101,129 $ 50,807 $ 12,926 $ 31,439 $ 95,172 Real estate: Commercial 58 56,893 48,388 4,087 3,242 55,717 Residential builder and developer 2 10,650 10,598 — — 10,598 Other commercial construction 6 10,743 460 — 10,375 10,835 Residential 85 10,485 6,528 267 4,277 11,072 Residential — limited documentation 11 1,962 437 — 1,635 2,072 Consumer: Home equity lines and loans 71 7,378 2,175 — 5,204 7,379 Automobile 302 3,053 1,818 287 948 3,053 Other 155 2,507 1,995 116 396 2,507 Total 817 $ 204,800 $ 123,206 $ 17,683 $ 57,516 $ 198,405 (a) Financial effects impacting the recorded investment included principal payments or advances, charge-offs and capitalized escrow arrearages. The present value of interest rate concessions, discounted at the effective rate of the original loan, was not material.
Summary of Lease Financing Receivables	A summary of lease financing receivables follows: December 31 2017 2016 (In thousands) Commercial leases: Direct financings: Lease payments receivable $ 1,159,584 $ 1,136,815 Estimated residual value of leased assets 89,666 79,449 Unearned income (110,261 ) (107,535 ) Investment in direct financings 1,138,989 1,108,729 Leveraged leases: Lease payments receivable 87,821 92,918 Estimated residual value of leased assets 88,491 110,328 Unearned income (35,792 ) (38,760 ) Investment in leveraged leases 140,520 164,486 Total investment in leases $ 1,279,509 $ 1,273,215 Deferred taxes payable arising from leveraged leases $ 81,359 $ 139,067
Minimum Future Lease Payments to be Received from Lease Financings	At December 31, 2017, the minimum future lease payments to be received from lease financings were as follows: (In thousands) Year ending December 31: 2018 $ 310,207 2019 297,599 2020 208,613 2021 150,553 2022 96,871 Later years 183,562 $ 1,247,405

Allowance for credit losses (Ta

Allowance for credit losses (Tables)	12 Months Ended
Allowance for credit losses (Tables)	Dec. 31, 2017
Receivables [Abstract]
Changes in Allowance for Credit Losses	Changes in the allowance for credit losses for the years ended December 31, 2017, 2016 and 2015 were as follows: Commercial, Financial, Real Estate Leasing, etc. Commercial Residential Consumer Unallocated Total (In thousands) 2017 Beginning balance $ 330,833 362,719 61,127 156,288 78,030 $ 988,997 Provision for credit losses 41,511 6,715 16,094 103,410 270 168,000 Net charge-offs Charge-offs (64,941 ) (7,931 ) (20,799 ) (130,927 ) — (224,598 ) Recoveries 21,196 12,582 8,983 42,038 — 84,799 Net (charge-offs) recoveries (43,745 ) 4,651 (11,816 ) (88,889 ) — (139,799 ) Ending balance $ 328,599 374,085 65,405 170,809 78,300 $ 1,017,198 2016 Beginning balance $ 300,404 326,831 72,238 178,320 78,199 $ 955,992 Provision for credit losses 59,506 33,627 6,902 90,134 (169 ) 190,000 Net charge-offs Charge-offs (59,244 ) (4,805 ) (26,133 ) (141,073 ) — (231,255 ) Recoveries 30,167 7,066 8,120 28,907 — 74,260 Net (charge-offs) recoveries (29,077 ) 2,261 (18,013 ) (112,166 ) — (156,995 ) Ending balance $ 330,833 362,719 61,127 156,288 78,030 $ 988,997 2015 Beginning balance $ 288,038 307,927 61,910 186,033 75,654 $ 919,562 Provision for credit losses 43,065 25,768 19,133 79,489 2,545 170,000 Net charge-offs Charge-offs (60,983 ) (16,487 ) (13,116 ) (107,787 ) — (198,373 ) Recoveries 30,284 9,623 4,311 20,585 — 64,803 Net charge-offs (30,699 ) (6,864 ) (8,805 ) (87,202 ) — (133,570 ) Ending balance $ 300,404 326,831 72,238 178,320 78,199 $ 955,992
Impaired Loans and Leases	The following tables provide information with respect to loans and leases that were considered impaired as of December 31, 2017 and 2016 and for the years ended December 31, 2017, 2016 and 2015. December 31, 2017 December 31, 2016 Recorded Investment Unpaid Principal Balance Related Allowance Recorded Investment Unpaid Principal Balance Related Allowance (In thousands) With an allowance recorded: Commercial, financial, leasing, etc. $ 177,250 194,257 45,488 168,072 184,432 48,480 Real estate: Commercial 67,199 75,084 9,140 71,862 86,666 11,620 Residential builder and developer 5,320 5,641 308 7,396 8,361 506 Other commercial construction 4,817 20,357 647 2,475 2,731 448 Residential 101,724 122,602 4,000 86,680 105,944 3,457 Residential — limited documentation 77,277 92,439 3,900 82,547 97,718 6,000 Consumer: Home equity lines and loans 48,847 53,914 8,812 44,693 48,965 8,027 Automobile 13,498 15,737 2,811 16,982 18,272 3,740 Other 3,220 5,872 656 3,791 5,296 776 499,152 585,903 75,762 484,498 558,385 83,054 With no related allowance recorded: Commercial, financial, leasing, etc. 89,126 115,327 — 100,805 124,786 — Real estate: Commercial 138,356 149,716 — 113,276 121,846 — Residential builder and developer 5,057 5,296 — 14,368 21,124 — Other commercial construction 5,456 9,130 — 15,933 35,281 — Residential 13,574 18,980 — 16,823 24,161 — Residential — limited documentation 9,588 16,138 — 15,429 24,590 — 261,157 314,587 — 276,634 351,788 — Total: Commercial, financial, leasing, etc. 266,376 309,584 45,488 268,877 309,218 48,480 Real estate: Commercial 205,555 224,800 9,140 185,138 208,512 11,620 Residential builder and developer 10,377 10,937 308 21,764 29,485 506 Other commercial construction 10,273 29,487 647 18,408 38,012 448 Residential 115,298 141,582 4,000 103,503 130,105 3,457 Residential — limited documentation 86,865 108,577 3,900 97,976 122,308 6,000 Consumer: Home equity lines and loans 48,847 53,914 8,812 44,693 48,965 8,027 Automobile 13,498 15,737 2,811 16,982 18,272 3,740 Other 3,220 5,872 656 3,791 5,296 776 Total $ 760,309 900,490 75,762 761,132 910,173 83,054
Interest Income Recognized on Impaired Loans	Year Ended December 31, 2017 Year Ended December 31, 2016 Interest Income Recognized Interest Income Recognized Average Recorded Investment Total Cash Basis Average Recorded Investment Total Cash Basis (In thousands) Commercial, financial, leasing, etc. $ 240,157 3,894 3,894 277,647 8,342 8,342 Real estate: Commercial 207,616 4,497 4,497 175,877 4,878 4,878 Residential builder and developer 16,209 6,419 6,419 29,237 2,300 2,300 Other commercial construction 15,142 1,001 1,001 19,697 644 644 Residential 110,646 7,177 3,406 98,394 6,227 3,154 Residential — limited documentation 93,097 5,981 1,607 103,060 5,999 1,975 Consumer: Home equity lines and loans 47,323 1,681 400 36,493 1,325 410 Automobile 15,045 1,025 81 19,636 1,242 99 Other 3,363 308 11 9,218 440 83 Total $ 748,598 31,983 21,316 769,259 31,397 21,885 Year Ended December 31, 2015 Interest Income Recognized Average Recorded Investment Total Cash Basis (In thousands) Commercial, financial, leasing, etc. $ 236,201 2,933 2,933 Real estate: Commercial 166,628 6,243 6,243 Residential builder and developer 59,457 335 335 Other commercial construction 20,276 2,311 2,311 Residential 101,483 6,188 4,037 Residential — 118,449 6,380 2,638 Consumer: Home equity lines and loans 21,523 905 261 Automobile 25,675 1,619 175 Other 18,809 729 113 Total $ 768,501 27,643 19,046
Summary of Loan Grades	The following table summarizes the loan grades applied to the various classes of the Company’s commercial loans and commercial real estate loans. Real Estate Commercial, Residential Other Financial, Builder and Commercial Leasing, etc. Commercial Developer Construction (In thousands) December 31, 2017 Pass $ 20,490,486 24,380,184 1,485,148 6,270,812 Criticized accrual 1,011,174 723,777 140,119 164,812 Criticized nonaccrual 240,991 184,982 6,451 10,088 Total $ 21,742,651 25,288,943 1,631,718 6,445,712 December 31, 2016 Pass $ 21,398,581 24,570,269 1,789,071 5,912,351 Criticized accrual 950,032 741,274 116,548 165,862 Criticized nonaccrual 261,434 176,201 16,707 18,111 Total $ 22,610,047 25,487,744 1,922,326 6,096,324
Allocation of Allowance for Credit Losses on Basis of Company's Impairment Methodology	The allocation of the allowance for credit losses summarized on the basis of the Company’s impairment methodology was as follows: Commercial, Financial, Real Estate Leasing, etc. Commercial Residential Consumer Total (In thousands) December 31, 2017 Individually evaluated for impairment $ 45,488 10,095 7,900 12,279 $ 75,762 Collectively evaluated for impairment 283,111 363,990 47,645 158,530 853,276 Purchased impaired — — 9,860 — 9,860 Allocated $ 328,599 374,085 65,405 170,809 938,898 Unallocated 78,300 Total $ 1,017,198 December 31, 2016 Individually evaluated for impairment $ 48,480 12,500 9,457 12,543 $ 82,980 Collectively evaluated for impairment 282,353 348,301 47,993 143,745 822,392 Purchased impaired — 1,918 3,677 — 5,595 Allocated $ 330,833 362,719 61,127 156,288 910,967 Unallocated 78,030 Total $ 988,997
Recorded Investment in Loans and Leases on Basis of Company's Impairment Methodology	The recorded investment in loans and leases summarized on the basis of the Company’s impairment methodology was as follows: Commercial, Financial, Real Estate Leasing, etc. Commercial Residential Consumer Total (In thousands) December 31, 2017 Individually evaluated for impairment $ 266,376 226,205 202,163 65,565 $ 760,309 Collectively evaluated for impairment 21,476,254 33,117,512 19,023,843 13,201,050 86,818,659 Purchased impaired 21 22,656 387,338 — 410,015 Total $ 21,742,651 33,366,373 19,613,344 13,266,615 $ 87,988,983 December 31, 2016 Individually evaluated for impairment $ 268,877 224,630 201,479 65,466 $ 760,452 Collectively evaluated for impairment 22,340,529 33,222,080 21,871,726 12,080,597 89,514,932 Purchased impaired 641 59,684 517,707 — 578,032 Total $ 22,610,047 33,506,394 22,590,912 12,146,063 $ 90,853,416

Premises and equipment (Tables)

Premises and equipment (Tables)	12 Months Ended
Premises and equipment (Tables)	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Summary of Premises and Equipment	The detail of premises and equipment was as follows: December 31 2017 2016 (In thousands) Land $ 98,077 $ 104,671 Buildings 454,610 448,442 Leasehold improvements 239,956 232,936 Furniture and equipment — owned 676,665 636,219 Furniture and equipment — capital leases 18,039 14,849 1,487,347 1,437,117 Less: accumulated depreciation and amortization Owned assets 830,832 756,245 Capital leases 10,064 5,609 840,896 761,854 Premises and equipment, net $ 646,451 $ 675,263

Capitalized servicing assets (T

Capitalized servicing assets (Tables)	12 Months Ended
Capitalized servicing assets (Tables)	Dec. 31, 2017
Transfers And Servicing [Abstract]
Servicing Asset at Amortized Cost	Changes in capitalized servicing assets were as follows: Residential Mortgage Loans Commercial Mortgage Loans For the Year Ended December 31, 2017 2016 2015 2017 2016 2015 (In thousands) Beginning balance $ 117,351 $ 118,303 $ 109,871 $ 103,764 $ 83,692 $ 72,939 Originations 28,792 28,618 35,556 34,620 40,117 29,914 Purchases 699 638 243 — — — Amortization (31,864 ) (30,208 ) (27,367 ) (24,308 ) (20,045 ) (19,161 ) 114,978 117,351 118,303 114,076 103,764 83,692 Valuation allowance — — — — — — Ending balance, net $ 114,978 $ 117,351 $ 118,303 $ 114,076 $ 103,764 $ 83,692 Other Total For the Year Ended December 31, 2017 2016 2015 2017 2016 2015 (In thousands) Beginning balance $ — $ 729 $ 4,107 $ 221,115 $ 202,724 $ 186,917 Originations — — — 63,412 68,735 65,470 Purchases — — — 699 638 243 Amortization — (729 ) (3,378 ) (56,172 ) (50,982 ) (49,906 ) — — 729 229,054 221,115 202,724 Valuation allowance — — — — — — Ending balance, net $ — $ — $ 729 $ 229,054 $ 221,115 $ 202,724
Economic Assumptions Used to Determine Fair Value of Capitalized Servicing Rights and Sensitivity of Value to Changes in Assumptions	Residential Commercial Weighted-average prepayment speeds 12.16 % Impact on fair value of 10% adverse change $ (8,935,000 ) Impact on fair value of 20% adverse change (17,159,000 ) Weighted-average OAS 10.67 % Impact on fair value of 10% adverse change $ (6,838,000 ) Impact on fair value of 20% adverse change (13,267,000 ) Weighted-average discount rate 18.00 % Impact on fair value of 10% adverse change $ (5,885,000 ) Impact on fair value of 20% adverse change (11,342,000 )

Goodwill and other intangible42

Goodwill and other intangible assets (Tables)	12 Months Ended
Goodwill and other intangible assets (Tables)	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets	Total amortizing intangible assets were comprised of the following: Gross Carrying Amount Accumulated Amortization Net Carrying Amount (In thousands) December 31, 2017 Core deposit $ 887,459 $ 820,110 $ 67,349 Other 182,568 178,328 4,240 Total $ 1,070,027 $ 998,438 $ 71,589 December 31, 2016 Core deposit $ 887,459 $ 789,988 $ 97,471 Other 177,268 177,084 184 Total $ 1,064,727 $ 967,072 $ 97,655
Estimated Amortization Expense in Future Years	Estimated amortization expense in future years for such intangible assets is as follows: (In thousands) Year ending December 31: 2018 $ 24,522 2019 19,086 2020 14,383 2021 9,681 2022 3,917 $ 71,589
Summary of Goodwill Assigned to Reportable Segments for Purposes of Testing for Impairment	A summary of goodwill assigned to each of the Company’s reportable segments as of December 31, 2017 and 2016 for purposes of testing for impairment is as follows: (In thousands) Business Banking $ 864,366 Commercial Banking 1,401,873 Commercial Real Estate 654,389 Discretionary Portfolio — Residential Mortgage Banking — Retail Banking 1,309,191 All Other 363,293 Total $ 4,593,112

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
Borrowings (Tables)	Dec. 31, 2017
Debt Disclosure [Abstract]
Amounts and Interest Rates of Short-term Borrowings	The amounts and interest rates of short-term borrowings were as follows: Federal Funds Purchased and Repurchase Agreements Other Short-term Borrowings Total (Dollars in thousands) At December 31, 2017 Amount outstanding $ 175,099 $ — $ 175,099 Weighted-average interest rate 0.92 % — 0.92 % For the year ended December 31, 2017 Highest amount at a month-end $ 204,977 $ 1,500,000 Daily-average amount outstanding 188,459 16,164 $ 204,623 Weighted-average interest rate 0.69 % 1.27 % 0.74 % At December 31, 2016 Amount outstanding $ 163,442 $ — $ 163,442 Weighted-average interest rate 0.32 % — 0.32 % For the year ended December 31, 2016 Highest amount at a month-end $ 225,940 $ 1,974,013 Daily-average amount outstanding 203,853 689,969 $ 893,822 Weighted-average interest rate 0.28 % 0.44 % 0.41 % At December 31, 2015 Amount outstanding $ 150,546 $ 1,981,636 $ 2,132,182 Weighted-average interest rate 0.06 % 0.43 % 0.40 % For the year ended December 31, 2015 Highest amount at a month-end $ 202,951 $ 1,989,257 Daily-average amount outstanding 187,167 360,838 $ 548,005 Weighted-average interest rate 0.08 % 0.43 % 0.31 %
Lines of Credit Under Formal Agreements	At December 31, 2017, M&T Bank had lines of credit under formal agreements as follows: (In thousands) Outstanding borrowings $ 576,954 Unused 31,624,206
Long-term Borrowings	Long-term borrowings were as follows: December 31, 2017 2016 (In thousands) Senior notes of M&T Bank: Variable rate due 2017 $ — $ 550,000 Variable rate due 2022 249,558 — 1.25% due 2017 — 499,999 1.40% due 2017 — 749,946 1.45% due 2018 499,907 501,829 2.25% due 2019 644,977 649,012 2.30% due 2019 746,919 749,473 2.10% due 2020 743,788 749,735 2.05% due 2020 739,961 — 2.50% due 2022 638,872 — 2.90% due 2025 749,404 749,320 Advances from FHLB: Fixed rates 576,876 1,154,737 Agreements to repurchase securities 421,771 1,084,694 Subordinated notes of Wilmington Trust Corporation (a wholly owned subsidiary of M&T): 8.50% due 2018 200,000 207,651 Subordinated notes of M&T Bank: 6.625% due 2017 — 409,526 5.585% due 2020, variable rate commenced 2015 409,361 409,361 5.629% due 2021, variable rate commenced 2016 500,000 500,000 3.40% due 2027 491,176 — Junior subordinated debentures of M&T associated with preferred capital securities: Fixed rates: BSB Capital Trust I — 8.125%, due 2028 15,682 15,659 Provident Trust I — 8.29%, due 2028 26,847 26,293 Southern Financial Statutory Trust I — 10.60%, due 2030 6,664 6,620 Variable rates: First Maryland Capital I — due 2027 146,794 146,256 First Maryland Capital II — due 2027 148,617 147,954 Allfirst Asset Trust — due 2029 96,640 96,494 BSB Capital Trust III — due 2033 15,464 15,464 Provident Statutory Trust III — due 2033 54,466 53,834 Southern Financial Capital Trust III — due 2033 8,051 7,968 Other 9,635 12,010 $ 8,141,430 $ 9,493,835
Maturity of Long-term Borrowings	Long-term borrowings at December 31, 2017 mature as follows: (In thousands) Year ending December 31: 2018 $ 701,256 2019 2,282,016 2020 2,005,383 2021 502,487 2022 888,430 Later years 1,761,858 $ 8,141,430

Shareholders' equity (Tables)

Shareholders' equity (Tables)	12 Months Ended
Shareholders' equity (Tables)	Dec. 31, 2017
Equity [Abstract]
Issued and Outstanding Preferred Stock	Issued and outstanding preferred stock of M&T as of December 31, 2017 and 2016 is presented below: Shares Issued and Outstanding Carrying Value (Dollars in thousands) Series A (a) Fixed Rate Cumulative Perpetual Preferred Stock, $1,000 liquidation preference per share 230,000 $ 230,000 Series C (a) Fixed Rate Cumulative Perpetual Preferred Stock, $1,000 liquidation preference per share 151,500 $ 151,500 Series E (b) Fixed-to-Floating Rate Non-cumulative Perpetual Preferred Stock, $1,000 liquidation preference per share 350,000 $ 350,000 Series F (c) Fixed-to-Floating Rate Non-cumulative Perpetual Preferred Stock, $10,000 liquidation preference per share 50,000 $ 500,000 (a) Dividends, if declared, are paid at 6.375%. Warrants to purchase M&T common stock at $73.77 per share issued in connection with the Series A preferred stock expire December 23, 2018 and totaled 257,008 at December 31, 2017. (b) Dividends, if declared, are paid semi-annually at a rate of 6.45% through February 14, 2024 and thereafter will be paid quarterly at a rate of the three-month LIBOR plus 361 basis points. The shares are redeemable in whole or in part on or after February 15, 2024. Notwithstanding M&T’s option to redeem the shares, if an event occurs such that the shares no longer qualify as Tier 1 capital, M&T may redeem all of the shares within 90 days following that occurrence. (c) Dividends, if declared, are paid semi-annually at a rate of 5.125% through October 31, 2026 and thereafter will be paid quarterly at a rate of the three-month LIBOR plus 352 basis points. The shares are redeemable in whole or in part on or after November 1, 2026. Notwithstanding M&T’s option to redeem the shares, if an event occurs such that the shares no longer qualify as Tier 1 capital, M&T may redeem all of the shares within 90 days following that occurrence.

Stock-based compensation plans

Stock-based compensation plans (Tables)	12 Months Ended
Stock-based compensation plans (Tables)	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Restricted Stock and Restricted Stock Unit Activity	A summary of restricted stock and restricted stock unit activity follows: Restricted Stock Units Outstanding Weighted- Average Grant Price Restricted Stock Outstanding Weighted- Average Grant Price Unvested at January 1, 2017 739,350 $ 111.21 499,324 $ 109.92 Granted 235,983 162.57 181,939 162.46 Vested (481,002 ) 114.06 (290,935 ) 108.97 Cancelled (11,774 ) 129.15 (16,584 ) 128.64 Unvested at December 31, 2017 482,557 $ 133.05 373,744 $ 135.41
Summary of Stock Option Activity	A summary of stock option activity follows: Weighted-Average Stock Options Outstanding Exercise Price Life (In Years) Aggregate Intrinsic Value (In thousands) Outstanding at January 1, 2017 1,594,591 $ 139.60 Granted 200 162.57 Exercised (658,400 ) 116.20 Expired (270,979 ) 165.46 Outstanding at December 31, 2017 665,412 $ 152.23 0.8 $ 18,086 Exercisable at December 31, 2017 665,010 $ 152.23 0.8 $ 18,072

Pension plans and other postr46

Pension plans and other postretirement benefits (Tables)	12 Months Ended
Pension plans and other postretirement benefits (Tables)	Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
Net Periodic Pension Expense for Defined Benefit Plans	Net periodic pension expense for defined benefit plans consisted of the following: Year Ended December 31 2017 2016 2015 (In thousands) Service cost $ 20,193 $ 25,037 $ 24,372 Interest cost on benefit obligation 79,270 83,410 72,731 Expected return on plan assets (108,524 ) (108,473 ) (96,155 ) Amortization of prior service cost (credit) 557 (3,228 ) (6,005 ) Recognized net actuarial loss 29,263 30,145 44,825 Net periodic pension expense $ 20,759 $ 26,891 $ 39,768 Net other postretirement benefits expense for defined benefit plans consisted of the following: Year Ended December 31 2017 2016 2015 (In thousands) Service cost $ 1,172 $ 1,595 $ 914 Interest cost on benefit obligation 3,716 4,971 2,995 Amortization of prior service credit (1,359 ) (1,359 ) (1,359 ) Recognized net actuarial (gain) loss (988 ) 60 106 Net other postretirement benefits expense $ 2,541 $ 5,267 $ 2,656
Data Relating to Funding Position of Defined Benefit Plans	Data relating to the funding position of the defined benefit plans were as follows: Pension Benefits Other Postretirement Benefits 2017 2016 2017 2016 (In thousands) Change in benefit obligation: Benefit obligation at beginning of year $ 2,007,158 $ 2,004,531 $ 109,922 $ 121,497 Service cost 20,193 25,037 1,172 1,595 Interest cost 79,270 83,410 3,716 4,971 Plan participants’ contributions — — 2,929 3,085 Amendments and curtailments — (28,308 ) (30,088 ) — Actuarial (gain) loss 172,180 4,827 (8,511 ) (10,553 ) Medicare Part D reimbursement — — 630 592 Benefits paid (90,065 ) (82,339 ) (11,133 ) (11,265 ) Benefit obligation at end of year 2,188,736 2,007,158 68,637 109,922 Change in plan assets: Fair value of plan assets at beginning of year 1,642,131 1,625,134 — — Actual return on plan assets 251,381 88,564 — — Employer contributions 211,444 10,772 7,574 7,588 Plan participants’ contributions — — 2,929 3,085 Medicare Part D reimbursement — — 630 592 Benefits paid (90,065 ) (82,339 ) (11,133 ) (11,265 ) Fair value of plan assets at end of year 2,014,891 1,642,131 — — Funded status $ (173,845 ) $ (365,027 ) $ (68,637 ) $ (109,922 ) Accrued liabilities recognized in the consolidated balance sheet $ (173,845 ) $ (365,027 ) $ (68,637 ) $ (109,922 ) Amounts recognized in accumulated other comprehensive income (“AOCI”) were: Net loss (gain) $ 460,622 $ 460,562 $ (13,936 ) $ (6,413 ) Net prior service cost (credit) 2,948 3,505 (36,466 ) (7,737 ) Pre-tax adjustment to AOCI 463,570 464,067 (50,402 ) (14,150 ) Taxes (121,873 ) (182,611 ) 13,251 5,568 Net adjustment to AOCI $ 341,697 $ 281,456 $ (37,151 ) $ (8,582 )
Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income	The table below reflects the changes in plan assets and benefit obligations recognized in other comprehensive income related to the Company’s postretirement benefit plans. Pension Plans Other Postretirement Benefit Plans Total (In thousands) 2017 Net loss (gain) $ 29,323 $ (8,511 ) $ 20,812 Amendments and curtailments — (30,088 ) (30,088 ) Amortization of prior service (cost) credit (557 ) 1,359 802 Amortization of actuarial (loss) gain (29,263 ) 988 (28,275 ) Total recognized in other comprehensive income, pre-tax $ (497 ) $ (36,252 ) $ (36,749 ) 2016 Net loss (gain) $ 24,736 $ (10,553 ) $ 14,183 Amendments and curtailments (28,308 ) — (28,308 ) Amortization of prior service credit 3,228 1,359 4,587 Amortization of actuarial loss (30,145 ) (60 ) (30,205 ) Total recognized in other comprehensive income, pre-tax $ (30,489 ) $ (9,254 ) $ (39,743 )
Amortization of Amounts in Accumulated Other Comprehensive Income Expected to be Recognized as Components of Net Periodic Benefit Expense	The following table reflects the amortization of amounts in accumulated other comprehensive income expected to be recognized as components of net periodic benefit expense during 2018: Pension Plans Other Postretirement Benefit Plans (In thousands) Amortization of net prior service cost (credit) $ 557 $ (4,729 ) Amortization of net loss (gain) 44,416 (830 )
Assumed Weighted-Average Rates Used to Determine Benefit Obligations	The assumed weighted-average rates used to determine benefit obligations at December 31 were: Pension Benefits Other Postretirement Benefits 2017 2016 2017 2016 Discount rate 3.50 % 4.00 % 3.50 % 4.00 % Rate of increase in future compensation levels 4.33 % 4.39 % — —
Assumed Weighted-Average Rates Used to Determine Net Benefit Expense	The assumed weighted-average rates used to determine net benefit expense for the years ended December 31 were: Pension Benefits Other Postretirement Benefits 2017 2016 2015 2017 2016 2015 Discount rate 4.00 % 4.25 % 4.00 % 4.00 % 4.25 % 4.00 % Long-term rate of return on plan assets 6.50 % 6.50 % 6.50 % — — — Rate of increase in future compensation levels 4.39 % 4.37 % 4.39 % — — —
Effects on One-Percentage Point Change in Assumed Health Care Cost Trend Rates	A one-percentage point change in assumed health care cost trend rates would have had the following effects: +1% -1% (In thousands) Increase (decrease) in: Service and interest cost $ 63 $ (57 ) Accumulated postretirement benefit obligation 1,454 (1,316 )
Fair Values of Company's Pension Plan Assets by Asset Category	The fair values of the Company’s pension plan assets at December 31, 2017 and 2016, by asset category, were as follows: Fair Value Measurement of Plan Assets At December 31, 2017 Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Asset category: Money-market investments $ 117,648 $ 62,706 $ 54,942 $ — Equity securities: M&T 154,818 154,818 — — Domestic(a) 240,763 240,763 — — International(b) 13,349 13,349 — — Mutual funds: Domestic(a) 205,509 205,509 — — International(b) 405,200 405,200 — — 1,019,639 1,019,639 — — Debt securities: Corporate(c) 89,751 — 89,751 — Government 235,984 — 235,984 — International 2,176 — 2,176 — Mutual funds: Domestic(d) 243,456 243,456 — — 571,367 243,456 327,911 — Other: Diversified mutual fund 80,227 80,227 — — Real estate partnerships 3,747 842 — 2,905 Private equity 31,484 — — 31,484 Hedge funds 178,080 125,966 — 52,114 Guaranteed deposit fund 10,925 — — 10,925 304,463 207,035 — 97,428 Total(e) $ 2,013,117 $ 1,532,836 $ 382,853 $ 97,428 Fair Value Measurement of Plan Assets At December 31, 2016 Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (In thousands) Asset category: Money-market investments $ 39,556 $ 35,562 $ 3,994 $ — Equity securities: M&T 164,474 164,474 — — Domestic(a) 200,595 200,595 — — International(b) 14,364 14,364 — — Mutual funds: Domestic(a) 250,472 250,472 — — International(b) 290,172 290,172 — — 920,077 920,077 — — Debt securities: Corporate(c) 104,909 — 104,909 — Government 121,869 — 121,869 — International 13,073 — 13,073 — Mutual funds: Domestic(d) 205,847 205,847 — — 445,698 205,847 239,851 — Other: Diversified mutual fund 92,691 92,691 — — Real estate partnerships 3,112 768 — 2,344 Private equity 21,924 — — 21,924 Hedge funds 106,250 85,270 — 20,980 Guaranteed deposit fund 10,992 — — 10,992 234,969 178,729 — 56,240 Total(e) $ 1,640,300 $ 1,340,215 $ 243,845 $ 56,240 (a) This category is mainly comprised of equities of companies primarily within the mid-cap and large-cap sectors of the U.S. economy and range across diverse industries. (b) This category is comprised of equities in companies primarily within the mid-cap and large-cap sectors of international markets mainly in developed markets in Europe and the Pacific Rim. (c) This category represents investment grade bonds of U.S. issuers from diverse industries. (d) Approximately 77% of the mutual funds were invested in investment grade bonds and 23% in high-yielding bonds at December 31, 2017. Approximately 75% of the mutual funds were invested in investment grade bonds and 25% in high-yielding bonds at December 31, 2016. The holdings within the funds were spread across diverse industries. (e) Excludes dividends and interest receivable totaling $1,774,000 and $1,831,000 at December 31, 2017 and 2016, respectively.
Changes in Level 3 Pension Plan Assets Measured at Fair Value on Recurring Basis	The changes in Level 3 pension plan assets measured at estimated fair value on a recurring basis during the year ended December 31, 2017 were as follows: Balance – January 1, 2017 Purchases (Sales) Total Realized/ Unrealized Gains (Losses) Balance – December 31, 2017 (In thousands) Other Real estate partnerships $ 2,344 $ 365 $ 196 $ 2,905 Private equity 21,924 6,821 2,739 31,484 Hedge funds 20,980 29,839 1,295 52,114 Guaranteed deposit fund 10,992 — (67 ) 10,925 Total $ 56,240 $ 37,025 $ 4,163 $ 97,428
Defined Benefit Plan Estimated Future Benefit Payments	Estimated benefits expected to be paid in future years related to the Company’s defined benefit pension and other postretirement benefits plans are as follows: Pension Benefits Other Postretirement Benefits (In thousands) Year ending December 31: 2018 $ 88,407 $ 7,318 2019 94,317 7,207 2020 98,753 7,055 2021 103,968 4,402 2022 107,298 4,302 2023 through 2027 594,900 19,830

Income taxes (Tables)

Income taxes (Tables)	12 Months Ended
Income taxes (Tables)	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Components of Income Tax Expense	The components of income tax expense were as follows: Year Ended December 31 2017 2016 2015 (In thousands) Current Federal $ 363,043 $ 428,750 $ 130,349 State and local 94,714 95,426 21,549 Total current 457,757 524,176 151,898 Deferred Federal 367,308 147,662 324,317 State and local 33,482 26,351 72,279 Total deferred 400,790 174,013 396,596 Amortization of investments in qualified affordable housing projects 57,009 45,095 46,531 Total income taxes applicable to pre-tax income $ 915,556 $ 743,284 $ 595,025
Schedule of Income Tax Expense Benefit Reconciliation	Total income taxes differed from the amount computed by applying the statutory federal income tax rate to pre-tax income as follows: Year Ended December 31 2017 2016 2015 (In thousands) Income taxes at statutory federal income tax rate $ 813,352 $ 720,439 $ 586,142 Increase (decrease) in taxes: Tax-exempt income (40,778 ) (35,364 ) (33,102 ) State and local income taxes, net of federal income tax effect 83,327 79,155 60,988 Qualified affordable housing project federal tax credits, net (16,015 ) (15,091 ) (15,297 ) Initial impact of enactment of Tax Act 85,431 — — Other (9,761 ) (5,855 ) (3,706 ) $ 915,556 $ 743,284 $ 595,025
Deferred Tax Assets (Liabilities)	Deferred tax assets (liabilities) were comprised of the following at December 31: 2017 2016 2015 (In thousands) Losses on loans and other assets $ 345,609 $ 590,288 $ 637,955 Retirement benefits 45,322 143,067 148,722 Postretirement and other employee benefits 26,009 52,512 55,962 Incentive and other compensation plans 25,050 36,616 60,337 Interest on loans 37,900 61,266 57,640 Stock-based compensation 26,676 52,181 72,090 Unrealized losses — 10,741 — Other 66,247 106,876 162,086 Gross deferred tax assets 572,813 1,053,547 1,194,792 Leasing transactions (181,159 ) (266,268 ) (285,074 ) Unrealized gains (94,285 ) — (31,121 ) Capitalized servicing rights (51,781 ) (71,108 ) (59,171 ) Depreciation and amortization (52,733 ) (63,959 ) (56,731 ) Other (21,599 ) (87,200 ) (55,611 ) Gross deferred tax liabilities (401,557 ) (488,535 ) (487,708 ) Net deferred tax asset $ 171,256 $ 565,012 $ 707,084
Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits follows: Federal, State and Local Tax Accrued Interest Unrecognized Income Tax Benefits (In thousands) Gross unrecognized tax benefits at January 1, 2015 $ 10,712 $ 3,869 $ 14,581 Increases as a result of tax positions taken during 2015 8,108 — 8,108 Increases as a result of tax positions taken in prior years — 807 807 Decreases as a result of settlements with taxing authorities (1,515 ) (274 ) (1,789 ) Unrealized tax benefits acquired in a business combination 7,232 3,567 10,799 Gross unrecognized tax benefits at December 31, 2015 24,537 7,969 32,506 Increases as a result of tax positions taken during 2016 12,237 — 12,237 Increases as a result of tax positions taken in prior years — 656 656 Decreases as a result of tax positions in prior years (885 ) (710 ) (1,595 ) Gross unrecognized tax benefits at December 31, 2016 35,889 7,915 43,804 Increases as a result of tax positions taken during 2017 13,019 — 13,019 Increases as a result of tax positions taken in prior years — 1,379 1,379 Decreases as a result of settlements with taxing authorities (332 ) (168 ) (500 ) Decreases as a result of tax positions taken in prior years (3,144 ) (3,475 ) (6,619 ) Gross unrecognized tax benefits at December 31, 2017 $ 45,432 $ 5,651 51,083 Less: Federal, state and local income tax benefits (10,727 ) Net unrecognized tax benefits at December 31, 2017 that, if recognized, would impact the effective income tax rate $ 40,356

Earnings per common share (Tabl

Earnings per common share (Tables)	12 Months Ended
Earnings per common share (Tables)	Dec. 31, 2017
Earnings Per Share [Abstract]
Computations of Basic Earnings Per Common Share	The computations of basic earnings per common share follow: Year Ended December 31 2017 2016 2015 (In thousands, except per share) Income available to common shareholders: Net income $ 1,408,306 $ 1,315,114 $ 1,079,667 Less: Preferred stock dividends(a) (72,734 ) (81,270 ) (81,270 ) Net income available to common equity 1,335,572 1,233,844 998,397 Less: Income attributable to unvested stock-based compensation awards (8,069 ) (10,385 ) (10,708 ) Net income available to common shareholders $ 1,327,503 $ 1,223,459 $ 987,689 Weighted-average shares outstanding: Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards 153,092 158,121 138,285 Less: Unvested stock-based compensation awards (933 ) (1,341 ) (1,482 ) Weighted-average shares outstanding 152,159 156,780 136,803 Basic earnings per common share $ 8.72 $ 7.80 $ 7.22 (a) Including impact of not as yet declared cumulative dividends.
Computations of Diluted Earnings Per Common Share	The computations of diluted earnings per common share follow: Year Ended December 31 2017 2016 2015 (In thousands, except per share) Net income available to common equity $ 1,335,572 $ 1,233,844 $ 998,397 Less: Income attributable to unvested stock-based compensation awards (8,055 ) (10,363 ) (10,673 ) Net income available to common shareholders $ 1,327,517 $ 1,223,481 $ 987,724 Adjusted weighted-average shares outstanding: Common and unvested stock-based compensation awards 153,092 158,121 138,285 Less: Unvested stock-based compensation awards (933 ) (1,341 ) (1,482 ) Plus: Incremental shares from assumed conversion of stock-based compensation awards and warrants to purchase common stock 392 524 730 Adjusted weighted-average shares outstanding 152,551 157,304 137,533 Diluted earnings per common share $ 8.70 $ 7.78 $ 7.18

Comprehensive income (Tables)

Comprehensive income (Tables)	12 Months Ended
Comprehensive income (Tables)	Dec. 31, 2017
Equity [Abstract]
Impact of Reclassification from AOCI to Retained Earnings	The impact of that reclassification was an increase in retained earnings as of December 31, 2017 resulting from items remaining in AOCI as of that date as follows: (In thousands) Net unrealized losses on investment securities $ 8,065 Defined benefit plans liability adjustments 53,960 Cash flow hedges and other 2,004 Increase to retained earnings $ 64,029
Components of Other Comprehensive Income (Loss) and Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) to Net Income	The following tables display the components of other comprehensive income (loss) and amounts reclassified from accumulated other Total Defined Amount Investment Securities Benefit Before Income With OTTI (a) All Other Plans Other Tax Tax Net (In thousands) Balance — January 1, 2017 $ 46,725 (73,785 ) (449,917 ) (8,268 ) $ (485,245 ) 190,609 $ (294,636 ) Other comprehensive income before reclassifications: Unrealized holding gains (losses), net (8,746 ) (6,259 ) — — (15,005 ) 7,269 (7,736 ) Foreign currency translation adjustment — — — 4,447 4,447 (2,206 ) 2,241 Unrealized losses on cash flow hedges — — — (12,291 ) (12,291 ) 4,837 (7,454 ) Current year benefit plans gains — — 9,276 — 9,276 (3,650 ) 5,626 Total other comprehensive income (loss) before reclassifications (8,746 ) (6,259 ) 9,276 (7,844 ) (13,573 ) 6,250 (7,323 ) Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income: Amortization of unrealized holding losses on held-to-maturity (“HTM”) securities — 3,387 — — 3,387 (b) (1,333 ) 2,054 Gains realized in net income (18,351 ) (2,928 ) — — (21,279 ) (c) 7,195 (14,084 ) Accretion of net gain on terminated cash flow hedges — — — (137 ) (137 ) (d) 54 (83 ) Net yield adjustment from cash flow hedges currently in effect — — — (3,916 ) (3,916 ) (b) 1,541 (2,375 ) Amortization of prior service credit — — (802 ) — (802 ) (e) 315 (487 ) Amortization of actuarial losses — — 28,275 — 28,275 (e) (11,126 ) 17,149 Total (27,097 ) (5,800 ) 36,749 (11,897 ) (8,045 ) 2,896 (5,149 ) Reclassification of income tax effects to retained earnings — — — — — (64,029 ) (64,029 ) Balance — December 31, 2017 $ 19,628 (79,585 ) (413,168 ) (20,165 ) $ (493,290 ) 129,476 $ (363,814 ) Total Defined Amount Investment Securities Benefit Before Income With OTTI (a) All Other Plans Other Tax Tax Net (In thousands) Balance — January 1, 2016 $ 16,359 62,849 (489,660 ) (4,093 ) $ (414,545 ) 162,918 $ (251,627 ) Other comprehensive income before reclassifications: Unrealized holding gains (losses), net 30,366 (110,316 ) — — (79,950 ) 31,509 (48,441 ) Foreign currency translation adjustment — — — (4,020 ) (4,020 ) 1,406 (2,614 ) Current year benefit plans gains — — 14,125 — 14,125 (5,557 ) 8,568 Total other comprehensive income (loss) before reclassifications 30,366 (110,316 ) 14,125 (4,020 ) (69,845 ) 27,358 (42,487 ) Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income: Amortization of unrealized holding losses on HTM securities — 3,996 — — 3,996 (b) (1,572 ) 2,424 Gains realized in net income — (30,314 ) — — (30,314 ) (c) 11,925 (18,389 ) Accretion of net gain on terminated cash flow hedges — — — (155 ) (155 ) (d) 61 (94 ) Amortization of prior service credit — — (4,587 ) — (4,587 ) (e) 1,805 (2,782 ) Amortization of actuarial losses — — 30,205 — 30,205 (e) (11,886 ) 18,319 Total reclassifications — (26,318 ) 25,618 (155 ) (855 ) 333 (522 ) Total gain (loss) during the period 30,366 (136,634 ) 39,743 (4,175 ) (70,700 ) 27,691 (43,009 ) Balance — December 31, 2016 $ 46,725 (73,785 ) (449,917 ) (8,268 ) $ (485,245 ) 190,609 $ (294,636 ) Balance — January 1, 2015 $ 7,438 201,828 (503,027 ) (4,082 ) $ (297,843 ) 116,849 $ (180,994 ) Other comprehensive income before reclassifications: Unrealized holding gains (losses), net 8,921 (142,623 ) — — (133,702 ) 52,376 (81,326 ) Foreign currency translation adjustment — — — (1,323 ) (1,323 ) 398 (925 ) Gains on cash flow hedges — — — 1,453 1,453 (572 ) 881 Current year benefit plans losses — — (24,200 ) — (24,200 ) 8,612 (15,588 ) Total other comprehensive income (loss) before reclassifications 8,921 (142,623 ) (24,200 ) 130 (157,772 ) 60,814 (96,958 ) Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income: Amortization of unrealized holding losses on HTM securities — 3,514 — — 3,514 (b) (1,383 ) 2,131 Losses realized in net income — 130 — — 130 (c) (49 ) 81 Accretion of net gain on terminated cash flow hedges — — — (141 ) (141 ) (d) 56 (85 ) Amortization of prior service credit — — (7,364 ) — (7,364 ) (e) 2,620 (4,744 ) Amortization of actuarial losses — — 44,931 — 44,931 (e) (15,989 ) 28,942 Total reclassifications — 3,644 37,567 (141 ) 41,070 (14,745 ) 26,325 Total gain (loss) during the period 8,921 (138,979 ) 13,367 (11 ) (116,702 ) 46,069 (70,633 ) Balance — December 31, 2015 $ 16,359 62,849 (489,660 ) (4,093 ) $ (414,545 ) 162,918 $ (251,627 ) (a) Other-than-temporary impairment. (b) Included in interest income. (c) Included in gain (loss) on bank investment securities. (d) Included in interest expense. (e) Included in salaries and employee benefits expense.
Accumulated Other Comprehensive Income (Loss), Net	Accumulated other comprehensive income (loss), net consisted of the following: Investment Securities Defined With OTTI All Other Benefit Plans Other Total (In thousands) Balance at January 1, 2015 $ 4,518 $ 122,683 $ (305,589 ) $ (2,606 ) $ (180,994 ) Net gain (loss) during 2015 5,403 (84,517 ) 8,610 (129 ) (70,633 ) Balance at December 31, 2015 9,921 38,166 (296,979 ) (2,735 ) (251,627 ) Net gain (loss) during 2016 18,417 (82,823 ) 24,105 (2,708 ) (43,009 ) Balance at December 31, 2016 28,338 (44,657 ) (272,874 ) (5,443 ) (294,636 ) Net gain (loss) during 2017 (10,755 ) (9,011 ) 22,288 (7,671 ) (5,149 ) Reclassification of income tax effects to retained earnings (3,115 ) (4,950 ) (53,960 ) (2,004 ) (64,029 ) Balance at December 31, 2017 $ 14,468 $ (58,618 ) $ (304,546 ) $ (15,118 ) $ (363,814 )

Other income and other expense

Other income and other expense (Tables)	12 Months Ended
Other income and other expense (Tables)	Dec. 31, 2017
Other Income And Expenses [Abstract]
Other Income and Other Expense	The following items, which exceeded 1% of total interest income and other income in the respective period, were included in either “other revenues from operations” or “other costs of operations” in the consolidated statement of income: Year Ended December 31 2017 2016 2015 (In thousands) Other income: Credit-related fee income $ 77,580 $ 70,424 $ 81,558 Letter of credit fees 52,724 Bank owned life insurance 52,984 Other expense: Professional services 289,862 268,060 267,540 Amortization of capitalized servicing rights 49,906

Derivative financial instrume51

Derivative financial instruments (Tables)	12 Months Ended
Derivative financial instruments (Tables)	Dec. 31, 2017
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Information about Interest Rate Swap Agreements	Information about interest rate swap agreements entered into for interest rate risk management purposes summarized by type of financial instrument the swap agreements were intended to hedge follows: Weighted- Average Rate Notional Amount Average Maturity Fixed Variable Estimated Fair Value Gain (a) (In (In (In December 31, 2017 Fair value hedges: Fixed rate long-term borrowings(b) $ 4,550,000 2.9 2.27 % 2.09 % $ 573 Cash flow hedges: Variable rate commercial real estate loans(b)( c) 4,850,000 2.0 1.52 % 1.36 % 66 Total $ 9,400,000 2.5 $ 639 December 31, 2016 Fair value hedges: Fixed rate long-term borrowings(b) $ 900,000 1.1 3.75 % 2.08 % $ 11,892 (a) Effective January 2017 certain clearinghouse exchanges revised their rules such that certain required payments by counterparties for variation margin on derivative instruments that had been treated as collateral are now treated as settlements of those positions. The impact of such rule changes at December 31, 2017 was a reduction of the estimated fair value losses on interest rate swap agreements designated as fair value hedges of $41.1 million and on interest rate swap agreements designated as cash flow hedges of $16.3 million. (b) Under the terms of these agreements, the Company receives settlement amounts at a fixed rate and pays at a variable rate. (c) Includes notional amount and terms of $2.0 billion of forward-starting interest rate swap agreements that will become effective upon maturity in 2019 of $2.0 billion of agreements currently in effect.
Notional Amount of Interest Rate Swap Agreements Outstanding Maturity	The notional amount of interest rate swap agreements entered into for risk management purposes that were outstanding at December 31, 2017 mature as follows: (In thousands) Year ending December 31: 2018 $ 500,000 2019 4,250,000 2020 3,500,000 2021 — 2022 650,000 2023 through 2027 500,000 $ 9,400,000
Information about Fair Values of Derivative Instruments in Consolidated Balance Sheet	Information about the fair values of derivative instruments in the Company’s consolidated balance sheet and consolidated statement of income follows: Asset Derivatives Liability Derivatives Fair Value Fair Value December 31 December 31 2017 2016 2017 2016 (In thousands) Derivatives designated and qualifying as hedging instruments Interest rate swap agreements (a) $ 639 $ 11,892 $ — $ — Commitments to sell real estate loans (a) 734 33,189 283 1,347 1,373 45,081 283 1,347 Derivatives not designated and qualifying as hedging instruments Mortgage-related commitments to originate real estate loans for sale (a) 8,797 8,060 494 735 Commitments to sell real estate loans (a) 2,526 5,210 1,019 399 Trading: Interest rate contracts (b) 74,164 228,810 132,104 167,737 Foreign exchange and other option and futures contracts (b) 5,657 7,908 5,286 6,639 91,144 249,988 138,903 175,510 Total derivatives $ 92,517 $ 295,069 $ 139,186 $ 176,857 (a) Asset derivatives are reported in other assets and liability derivatives are reported in other liabilities. (b) Asset derivatives are reported in trading account assets and liability derivatives are reported in other liabilities. The impact of the variation margin rule change at December 31, 2017 was a reduction of the estimated fair value of interest rate contracts in the trading account in an asset position of $136.2 million and in a liability position of $12.2 million.
Information about Fair Values of Derivative Instruments in Consolidated Statement of Income	Amount of Gain (Loss) Recognized Year Ended December 31, 2017 Year Ended December 31, 2016 Year Ended December 31, 2015 Derivative Hedged Item Derivative Hedged Item Derivative Hedged Item (In thousands) Derivatives in fair value hedging relationships Interest rate swap agreements: Fixed rate long-term borrowings (a) $ (52,392 ) 51,628 $ (32,000 ) 30,906 $ (29,359 ) 28,719 Derivatives not designated as hedging Trading: Interest rate contracts (b) $ 5,398 $ 14,042 $ 10,755 Foreign exchange and other option and futures contracts (b) 6,821 7,665 9,337 Total $ 12,219 $ 21,707 $ 20,092 (a) Reported as other revenues from operations. (b) Reported as trading account and foreign exchange gains.

Fair value measurements (Tables

Fair value measurements (Tables)	12 Months Ended
Fair value measurements (Tables)	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Estimated Fair Value on Recurring Basis	The following tables present assets and liabilities at December 31, 2017 and 2016 measured at estimated fair value on a recurring basis: Fair Value Measurements Level 1 (a) Level 2 (a) Level 3 (In thousands) December 31, 2017 Trading account assets $ 132,909 $ 47,873 $ 85,036 $ — Investment securities available for sale: U.S. Treasury and federal agencies 1,947,487 — 1,947,487 — Obligations of states and political subdivisions 2,589 — 2,589 — Mortgage-backed securities: Government issued or guaranteed 8,716,392 — 8,716,392 — Privately issued 28 — — 28 Other debt securities 128,832 — 128,832 — Equity securities 100,956 73,232 27,724 — 10,896,284 73,232 10,823,024 28 Real estate loans held for sale 378,047 — 378,047 — Other assets (b) 12,696 — 3,899 8,797 Total assets $ 11,419,936 $ 121,105 $ 11,290,006 $ 8,825 Trading account liabilities $ 137,390 $ — $ 137,390 $ — Other liabilities (b) 1,796 — 1,302 494 Total liabilities $ 139,186 $ — $ 138,692 $ 494 December 31, 2016 Trading account assets $ 323,867 $ 46,135 $ 277,732 $ — Investment securities available for sale: U.S. Treasury and federal agencies 1,902,544 — 1,902,544 — Obligations of states and political subdivisions 3,641 — 3,641 — Mortgage-backed securities: Government issued or guaranteed 10,954,861 — 10,954,861 — Privately issued 44 — — 44 Other debt securities 118,516 — 118,516 — Equity securities 352,466 301,711 50,755 — 13,332,072 301,711 13,030,317 44 Real estate loans held for sale 1,056,180 — 1,056,180 — Other assets (b) 58,351 — 50,291 8,060 Total assets $ 14,770,470 $ 347,846 $ 14,414,520 $ 8,104 Trading account liabilities $ 174,376 $ — $ 174,376 $ — Other liabilities (b) 2,481 — 1,746 735 Total liabilities $ 176,857 $ — $ 176,122 $ 735 (a) There were no significant transfers between Level 1 and Level 2 of the fair value hierarchy during the years ended December 31, 2017 and 2016. (b) Comprised predominantly of interest rate swap agreements used for interest rate risk management (Level 2), commitments to sell real estate loans (Level 2) and commitments to originate real estate loans to be held for sale (Level 3).
Changes in Level 3 Assets and Liabilities Measured at Estimated Fair Value on Recurring Basis	The changes in Level 3 assets and liabilities measured at estimated fair value on a recurring basis during the years ended December 31, 2017, 2016 and 2015 were as follows: Investment Securities Available for Sale Privately Issued Mortgage-Backed Other Assets (In thousands) 2017 Balance — January 1, 2017 $ 44 $ 7,325 Total gains (losses) realized/unrealized: Included in earnings — 77,832 (b) Sales — — Settlements (16 ) — Transfers out of Level 3 (a) — (76,854 ) (e) Balance — December 31, 2017 $ 28 8,303 Changes in unrealized gains included in earnings related to assets still held at December 31, 2017 $ — 7,978 (b) Investment Securities Available for Sale Privately Issued Mortgage-Backed Collateralized Other Assets (In thousands) 2016 Balance — January 1, 2016 $ 74 47,393 9,879 Total gains (losses) realized/unrealized: Included in earnings — 30,041 (c) 110,937 (b) Included in other comprehensive income — (18,268 ) (d) — Sales — (58,296 ) — Settlements (30 ) (870 ) — Transfers out of Level 3 (a) — — (113,491 ) (e) Balance — December 31, 2016 $ 44 — 7,325 Changes in unrealized gains included in earnings related to assets still held at December 31, 2016 $ — — 7,256 (b) 2015 Balance — January 1, 2015 $ 103 50,316 17,347 Total gains realized/unrealized: Included in earnings — — 87,061 (b) Included in other comprehensive income — 3,254 (d) — Settlements (29 ) (6,177 ) — Transfers out of Level 3 (a) — — (94,529 ) (e) Balance — December 31, 2015 $ 74 47,393 9,879 Changes in unrealized gains included in earnings related to assets still held at December 31, 2015 $ — — 8,850 (b) (a) The Company’s policy for transfers between fair value levels is to recognize the transfer as of the actual date of the event or change in circumstances that caused the transfer. (b) Reported as mortgage banking revenues in the consolidated statement of income and includes the fair value of commitment issuances and expirations. (c) Reported as gain on bank investment securities in the consolidated statement of income. (d) Reported as net unrealized gains (losses) on investment securities in the consolidated statement of comprehensive income. (e) Transfers out of Level 3 consist of interest rate locks transferred to closed loans.
Quantitative Information Related to Significant Unobservable Inputs	The following tables present quantitative information about significant unobservable inputs used in the fair value measurements for Level 3 assets and liabilities at December 31, 2017 and 2016: Fair Value Valuation Technique Unobservable Inputs/Assumptions Range (Weighted- Average) (In December 31, 2017 Recurring fair value measurements Privately issued mortgage-backed securities $ 28 Two independent pricing quotes — — Net other assets (liabilities) (a) 8,303 Discounted Commitment expirations 0%-78% (22%) December 31, 2016 Recurring fair value measurements Privately issued mortgage-backed securities $ 44 Two independent pricing quotes — — Net other assets (liabilities) (a) 7,325 Discounted Commitment expirations 0%-77% (30%) (a) Other Level 3 assets (liabilities) consist of commitments to originate real estate loans.
Carrying Amounts and Estimated Fair Value for Financial Instrument Assets (Liabilities)	The carrying amounts and estimated fair value for financial instrument assets (liabilities) are presented in the following table: December 31, 2017 Carrying Amount Estimated Fair Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Cash and cash equivalents $ 1,420,888 1,420,888 1,352,035 68,853 — Interest-bearing deposits at banks 5,078,903 5,078,903 — 5,078,903 — Trading account assets 132,909 132,909 47,873 85,036 — Investment securities 14,664,525 14,653,074 73,232 14,469,127 110,715 Loans and leases: Commercial loans and leases 21,742,651 21,321,282 — — 21,321,282 Commercial real estate loans 33,366,373 32,950,724 — 22,130 32,928,594 Residential real estate loans 19,613,344 19,596,826 — 4,440,645 15,156,181 Consumer loans 13,266,615 13,161,517 — — 13,161,517 Allowance for credit losses (1,017,198 ) — — — — Loans and leases, net 86,971,785 87,030,349 — 4,462,775 82,567,574 Accrued interest receivable 327,170 327,170 — 327,170 — Financial liabilities: Noninterest-bearing deposits $ (33,975,180 ) (33,975,180 ) — (33,975,180 ) — Savings and interest-checking deposits (51,698,008 ) (51,698,008 ) — (51,698,008 ) — Time deposits (6,580,962 ) (6,635,048 ) — (6,635,048 ) — Deposits at Cayman Islands office (177,996 ) (177,996 ) — (177,996 ) — Short-term borrowings (175,099 ) (175,099 ) — (175,099 ) — Long-term borrowings (8,141,430 ) (8,193,783 ) — (8,193,783 ) — Accrued interest payable (75,641 ) (75,641 ) — (75,641 ) — Trading account liabilities (137,390 ) (137,390 ) — (137,390 ) — Other financial instruments: Commitments to originate real estate loans for sale $ 8,303 8,303 — — 8,303 Commitments to sell real estate loans 1,958 1,958 — 1,958 — Other credit-related commitments (125,281 ) (125,281 ) — — (125,281 ) Interest rate swap agreements used for interest rate risk management 639 639 — 639 — December 31, 2016 Carrying Amount Estimated Fair Value Level 1 Level 2 Level 3 (In thousands) Financial assets: Cash and cash equivalents $ 1,320,549 1,320,549 1,249,654 70,895 — Interest-bearing deposits at banks 5,000,638 5,000,638 — 5,000,638 — Trading account assets 323,867 323,867 46,135 277,732 — Investment securities 16,250,468 16,244,412 301,711 15,821,176 121,525 Loans and leases: Commercial loans and leases 22,610,047 22,239,428 — — 22,239,428 Commercial real estate loans 33,506,394 33,129,428 — 642,590 32,486,838 Residential real estate loans 22,590,912 22,638,167 — 4,912,488 17,725,679 Consumer loans 12,146,063 12,061,590 — — 12,061,590 Allowance for credit losses (988,997 ) — — — — Loans and leases, net 89,864,419 90,068,613 — 5,555,078 84,513,535 Accrued interest receivable 308,805 308,805 — 308,805 — Financial liabilities: Noninterest-bearing deposits $ (32,813,896 ) (32,813,896 ) — (32,813,896 ) — Savings and interest-checking deposits (52,346,207 ) (52,346,207 ) — (52,346,207 ) — Time deposits (10,131,846 ) (10,222,585 ) — (10,222,585 ) — Deposits at Cayman Islands office (201,927 ) (201,927 ) — (201,927 ) — Short-term borrowings (163,442 ) (163,442 ) — (163,442 ) — Long-term borrowings (9,493,835 ) (9,473,844 ) — (9,473,844 ) — Accrued interest payable (75,172 ) (75,172 ) — (75,172 ) — Trading account liabilities (174,376 ) (174,376 ) — (174,376 ) — Other financial instruments: Commitments to originate real estate loans for sale $ 7,325 7,325 — — 7,325 Commitments to sell real estate loans 36,653 36,653 — 36,653 — Other credit-related commitments (136,295 ) (136,295 ) — — (136,295 ) Interest rate swap agreements used for interest rate risk management 11,892 11,892 — 11,892 —

Commitments and contingencies (

Commitments and contingencies (Tables)	12 Months Ended
Commitments and contingencies (Tables)	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Company's Significant Commitments	The following table presents the Company’s significant commitments. Certain of these commitments are not included in the Company’s consolidated balance sheet. December 31 2017 2016 (In thousands) Commitments to extend credit Home equity lines of credit $ 5,482,622 5,499,609 Commercial real estate loans to be sold 194,763 70,100 Other commercial real estate 6,050,569 6,451,709 Residential real estate loans to be sold 347,113 478,950 Other residential real estate 201,426 232,721 Commercial and other 12,733,815 12,298,473 Standby letters of credit 2,497,844 2,987,091 Commercial letters of credit 46,739 44,723 Financial guarantees and indemnification contracts 3,434,381 3,043,580 Commitments to sell real estate loans 812,217 1,489,237
Minimum Lease Payments Under Noncancelable Operating Leases	Minimum lease payments under noncancelable operating leases are summarized in the following table: (In thousands) Year ending December 31: 2018 $ 92,824 2019 87,298 2020 70,490 2021 54,685 2022 41,953 Later years 82,195 $ 429,445

Segment information (Tables)

Segment information (Tables)	12 Months Ended
Segment information (Tables)	Dec. 31, 2017
Segment Reporting [Abstract]
Summary of Reclassified Segment Information on Comparable Basis	The financial information of the Company’s segments was compiled utilizing the accounting policies described in note 1 with certain exceptions. The more significant of these exceptions are described herein. The Company allocates interest income or interest expense using a methodology that charges users of funds (assets) interest expense and credits providers of funds (liabilities) with income based on the maturity, prepayment and/or repricing characteristics of the assets and liabilities. A provision for credit losses is allocated to segments in an amount based largely on actual net charge-offs incurred by the segment during the period plus or minus an amount necessary to adjust the segment’s allowance for credit losses due to changes in loan balances. In contrast, the level of the consolidated provision for credit losses is determined using the methodologies described in notes 1 and 5. The net effects of these allocations are recorded in the “All Other” category. Indirect fixed and variable expenses incurred by certain centralized support areas are allocated to segments based on actual usage (for example, volume measurements) and other criteria. Certain types of administrative expenses and bankwide expense accruals (including amortization of core deposit and other intangible assets associated with acquisitions of financial institutions) are generally not allocated to segments. Income taxes are allocated to segments based on the Company’s marginal statutory tax rate adjusted for any tax-exempt income or non-deductible expenses. Equity is allocated to the segments based on regulatory capital requirements and in proportion to an assessment of the inherent risks associated with the business of the segment (including interest, credit and operating risk). The management accounting policies and processes utilized in compiling segment financial information are highly subjective and, unlike financial accounting, are not based on authoritative guidance similar to GAAP. As a result, reported segment results are not necessarily comparable with similar information reported by other financial institutions. Furthermore, changes in management structure or allocation methodologies and procedures may result in changes in reported segment financial data. During 2017, the Company revised its funds transfer pricing allocation related to certain deposit categories. Accordingly, financial information presented herein for 2016 and 2015 has been reclassified to provide segment information on a comparable basis, as noted in the following tables. For the Year Ended December 31, 2016 Net Interest Income as Previously Reported Impact of Changes Net Interest Income as Reclassified Net Income (Loss) as Previously Reported Impact of Changes Net Income (Loss) as Reclassified (In thousands) Business Banking $ 354,333 17,556 371,889 $ 93,346 10,412 103,758 Commercial Banking 785,874 (535 ) 785,339 411,696 (317 ) 411,379 Commercial Real Estate 608,385 — 608,385 350,358 — 350,358 Discretionary Portfolio 345,926 — 345,926 163,538 — 163,538 Residential Mortgage Banking 70,655 (40,846 ) 29,809 79,678 (24,225 ) 55,453 Retail Banking 1,074,125 33,263 1,107,388 274,646 19,727 294,373 All Other 230,589 (9,438 ) 221,151 (58,148 ) (5,597 ) (63,745 ) Total $ 3,469,887 — 3,469,887 $ 1,315,114 — 1,315,114 For the Year Ended December 31, 2015 Net Interest Income as Previously Reported Impact of Changes Net Interest Income as Reclassified Net Income (Loss) as Previously Reported Impact of Changes Net Income (Loss) as Reclassified (In thousands) Business Banking $ 338,855 18,523 357,378 $ 98,758 10,986 109,744 Commercial Banking 753,604 (242 ) 753,362 431,030 (144 ) 430,886 Commercial Real Estate 577,922 — 577,922 340,641 — 340,641 Discretionary Portfolio 97,626 — 97,626 59,272 — 59,272 Residential Mortgage Banking 63,939 (23,970 ) 39,969 88,578 (14,216 ) 74,362 Retail Banking 917,041 34,699 951,740 267,518 20,579 288,097 All Other 93,600 (29,010 ) 64,590 (206,130 ) (17,205 ) (223,335 ) Total $ 2,842,587 — 2,842,587 $ 1,079,667 — 1,079,667
Information about Company's Segments	Information about the Company’s segments is presented in the accompanying table. Income statement amounts are in thousands of dollars. Balance sheet amounts are in millions of dollars. For the Years Ended December 31, 2017, 2016 and 2015 Business Banking Commercial Banking Commercial Real Estate Discretionary Portfolio 2017 2016 2015 2017 2016 2015 2017 2016 2015 2017 2016 2015 Net interest income(a) $ 393,948 $ 371,889 $ 357,378 $ 809,301 $ 785,339 $ 753,362 $ 649,378 $ 608,385 $ 577,922 $ 277,095 $ 345,926 $ 97,626 Noninterest income 112,512 108,783 108,195 283,447 274,923 290,142 169,966 179,706 142,948 23,851 26,075 28,114 506,460 480,672 465,573 1,092,748 1,060,262 1,043,504 819,344 788,091 720,870 300,946 372,001 125,740 Provision for credit losses 15,598 12,709 15,513 11,876 34,903 25,089 (7,524 ) (3,447 ) (8,003 ) 31,119 32,925 7,599 Amortization of core deposit and other intangible assets — — — — — — 1,060 — — — — — Depreciation and other amortization 393 404 407 509 520 566 24,410 20,120 19,247 279 472 679 Other noninterest expense 294,493 292,124 264,163 339,936 327,616 288,303 207,493 204,965 169,688 76,021 95,300 49,839 Income (loss) before taxes 195,976 175,435 185,490 740,427 697,223 729,546 593,905 566,453 539,938 193,527 243,304 67,623 Income tax expense (benefit) 80,043 71,677 75,746 303,556 285,844 298,660 229,770 216,095 199,297 58,559 79,766 8,351 Net income (loss) $ 115,933 $ 103,758 $ 109,744 $ 436,871 $ 411,379 $ 430,886 $ 364,135 $ 350,358 $ 340,641 $ 134,968 $ 163,538 $ 59,272 Average total assets (in millions) $ 5,602 $ 5,456 $ 5,339 $ 26,573 $ 25,592 $ 24,143 $ 22,741 $ 21,131 $ 18,827 $ 37,203 $ 40,867 $ 26,648 Capital expenditures (in millions) $ — $ — $ — $ — $ — $ — $ 1 $ — $ — $ — $ — $ — For the Years Ended December 31, 2017, 2016 and 2015 Residential Mortgage Banking Retail Banking All Other Total 2017 2016 2015 2017 2016 2015 2017 2016 2015 2017 2016 2015 Net interest income(a) $ 30,328 $ 29,809 $ 39,969 $ 1,210,066 $ 1,107,388 $ 951,740 $ 410,928 $ 221,151 $ 64,590 $ 3,781,044 $ 3,469,887 $ 2,842,587 Noninterest income 321,589 342,858 336,099 329,833 323,176 324,953 609,945 570,475 594,586 1,851,143 1,825,996 1,825,037 351,917 372,667 376,068 1,539,899 1,430,564 1,276,693 1,020,873 791,626 659,176 5,632,187 5,295,883 4,667,624 Provision for credit losses 1,254 (3,617 ) (5,225 ) 107,412 120,437 72,953 8,265 (3,910 ) 62,074 168,000 190,000 170,000 Amortization of core deposit and other intangible assets — — — — — — 30,306 42,613 26,424 31,366 42,613 26,424 Depreciation and other amortization 32,011 30,264 27,883 38,234 37,657 35,291 69,923 68,541 64,852 165,759 157,978 148,925 Other noninterest expense 247,639 258,141 233,651 758,153 776,123 682,594 1,019,465 892,625 959,345 2,943,200 2,846,894 2,647,583 Income (loss) before taxes 71,013 87,879 119,759 636,100 496,347 485,855 (107,086 ) (208,243 ) (453,519 ) 2,323,862 2,058,398 1,674,692 Income tax expense (benefit) 25,446 32,426 45,397 258,934 201,974 197,758 (40,752 ) (144,498 ) (230,184 ) 915,556 743,284 595,025 Net income (loss) $ 45,567 $ 55,453 $ 74,362 $ 377,166 $ 294,373 $ 288,097 $ (66,334 ) $ (63,745 ) $ (223,335 ) $ 1,408,306 $ 1,315,114 $ 1,079,667 Average total assets (in millions) $ 2,355 $ 2,569 $ 2,918 $ 12,702 $ 11,840 $ 11,035 $ 13,684 $ 16,885 $ 12,870 $ 120,860 $ 124,340 $ 101,780 Capital expenditures (in millions) $ — $ — $ — $ 34 $ 46 $ 14 $ 44 $ 62 $ 68 $ 79 $ 108 $ 82 (a) Net interest income is the difference between actual taxable-equivalent interest earned on assets and interest paid on liabilities by a segment and a funding charge (credit) based on the Company’s internal funds transfer pricing methodology. Segments are charged a cost to fund any assets (e.g. loans) and are paid a funding credit for any funds provided (e.g. deposits). The taxable-equivalent adjustment aggregated $34,570,000 in 2017, $26,962,000 in 2016 and $24,463,000 in 2015 and is eliminated in “All Other” net interest income and income tax expense (benefit).
Intersegment Activity Eliminated in Arriving at Consolidated Totals was Included in "All Other" Category	The amount of intersegment activity eliminated in arriving at consolidated totals was included in the “All Other” category as follows: Year Ended December 31 2017 2016 2015 (In thousands) Revenues $ (43,941 ) $ (48,625 ) $ (48,972 ) Expenses (32,623 ) (40,422 ) (13,332 ) Income taxes (benefit) (4,606 ) (3,338 ) (14,503 ) Net income (loss) (6,712 ) (4,865 ) (21,137 )

Regulatory matters (Tables)

Regulatory matters (Tables)	12 Months Ended
Regulatory matters (Tables)	Dec. 31, 2017
Banking And Thrift [Abstract]
Summary of Required Minimum and Well Capitalized Capital Ratios	Pursuant to the rules in effect as of December 31, 2017, the required minimum and well capitalized capital ratios are as follows: Well Minimum Capitalized ● Common equity Tier 1 ("CET1") to risk-weighted assets 4.5 % 6.5 % ● Tier 1 capital to risk-weighted assets 6.0 % 8.0 % ● Total capital to risk-weighted assets 8.0 % 10.0 % ● Leverage — Tier 1 capital to average total assets, as defined 4.0 % 5.0 %
Capital Ratios and Amounts of Company and its Banking Subsidiaries	The capital ratios and amounts of the Company and its banking subsidiaries as of December 31, 2017 and 2016 are presented below: M&T (Consolidated) M&T Bank Wilmington Trust, N.A. (Dollars in thousands) December 31, 2017: Common equity Tier 1 capital Amount $ 10,675,735 $ 9,978,163 $ 529,988 Ratio(a) 10.99 % 10.30 % 48.16 % Tier 1 capital Amount 11,908,166 9,978,163 529,988 Ratio(a) 12.26 % 10.30 % 48.16 % Total capital Amount 14,328,467 12,012,171 534,235 Ratio(a) 14.75 % 12.40 % 48.54 % Leverage Amount 11,908,166 9,978,163 529,988 Ratio(b) 10.31 % 8.68 % 13.03 % December 31, 2016: Common equity Tier 1 capital Amount $ 10,849,642 $ 10,115,688 $ 496,801 Ratio(a) 10.70 % 10.02 % 57.08 % Tier 1 capital Amount 12,083,948 10,115,688 496,801 Ratio(a) 11.92 % 10.02 % 57.08 % Total capital Amount 14,282,492 11,812,114 501,111 Ratio(a) 14.09 % 11.70 % 57.57 % Leverage Amount 12,083,948 10,115,688 496,801 Ratio(b) 9.99 % 8.41 % 15.31 % (a) The ratio of capital to risk-weighted assets, as defined by regulation. (b) The ratio of capital to average assets, as defined by regulation.

Parent company financial stat56

Parent company financial statements (Tables)	12 Months Ended
Parent company financial statements (Tables)	Dec. 31, 2017
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
Condensed Balance Sheet	Condensed Balance Sheet December 31 2017 2016 (In thousands) Assets Cash in subsidiary bank $ 13,379 $ 15,003 Due from consolidated bank subsidiaries Money-market savings 1,616,147 1,767,184 Current income tax receivable 4,437 3,061 Total due from consolidated bank subsidiaries 1,620,584 1,770,245 Investments in consolidated subsidiaries Banks 14,841,794 15,003,964 Other 253,904 161,201 Investments in unconsolidated subsidiaries (note 19) 23,453 23,643 Investment in Bayview Lending Group LLC — 11,908 Other assets 66,023 71,687 Total assets $ 16,819,137 $ 17,057,651 Liabilities Accrued expenses and other liabilities $ 49,093 $ 54,487 Long-term borrowings 519,225 516,542 Total liabilities 568,318 571,029 Shareholders’ equity 16,250,819 16,486,622 Total liabilities and shareholders’ equity $ 16,819,137 $ 17,057,651
Condensed Statement of Income	Condensed Statement of Income Year Ended December 31 2017 2016 2015 (In thousands, except per share) Income Dividends from consolidated bank subsidiaries $ 1,540,000 $ 1,930,000 $ 480,000 Equity in earnings of Bayview Lending Group LLC 352 (10,752 ) (14,267 ) Other income 9,493 5,530 2,364 Total income 1,549,845 1,924,778 468,097 Expense Interest on long-term borrowings 21,591 18,963 24,453 Other expense 19,636 21,361 16,793 Total expense 41,227 40,324 41,246 Income before income taxes and equity in undistributed income of subsidiaries 1,508,618 1,884,454 426,851 Income tax credits 26,453 17,247 19,965 Income before equity in undistributed income of subsidiaries 1,535,071 1,901,701 446,816 Equity in undistributed income of subsidiaries Net income of subsidiaries 1,413,235 1,343,413 1,112,851 Less: dividends received (1,540,000 ) (1,930,000 ) (480,000 ) Equity in undistributed income of subsidiaries (126,765 ) (586,587 ) 632,851 Net income $ 1,408,306 $ 1,315,114 $ 1,079,667 Net income per common share Basic $ 8.72 $ 7.80 $ 7.22 Diluted 8.70 7.78 7.18
Condensed Statement of Cash Flow	Condensed Statement of Cash Flows Year Ended December 31 2017 2016 2015 (In thousands) Cash flows from operating activities Net income $ 1,408,306 $ 1,315,114 $ 1,079,667 Adjustments to reconcile net income to net cash provided by operating activities Equity in undistributed income of subsidiaries 126,765 586,587 (632,851 ) Benefit (provision) for deferred income taxes 4,543 (3,157 ) (3,655 ) Net change in accrued income and expense (170 ) 12,898 21,780 Loss (gain) on sale of assets (2,995 ) (2,342 ) 119 Net cash provided by operating activities 1,536,449 1,909,100 465,060 Cash flows from investing activities Proceeds from sales or maturities of investment securities — 51 755 Other, net 12,407 13,619 14,038 Net cash provided by investing activities 12,407 13,670 14,793 Cash flows from financing activities Payments on long-term borrowings — — (322,621 ) Purchases of treasury stock (1,205,905 ) (641,334 ) — Dividends paid — common (457,402 ) (441,891 ) (375,017 ) Dividends paid — preferred (72,734 ) (81,270 ) (81,270 ) Redemption of Series D preferred stock — (500,000 ) — Proceeds from issuance of Series F preferred stock — 495,000 — Other, net 34,524 143,764 76,364 Net cash used by financing activities (1,701,517 ) (1,025,731 ) (702,544 ) Net increase (decrease) in cash and cash equivalents (152,661 ) 897,039 (222,691 ) Cash and cash equivalents at beginning of year 1,782,187 885,148 1,107,839 Cash and cash equivalents at end of year $ 1,629,526 $ 1,782,187 $ 885,148 Supplemental disclosure of cash flow information Interest received during the year $ 2,313 $ 1,931 $ 1,905 Interest paid during the year 18,498 15,918 30,420 Income taxes received during the year 21,740 8,877 16,696

Significant Accounting Polici57

Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017
Significant Accounting Policies [Line Items]
Delinquent period of loans resulting in accrued interest being charged against income	90 days
Delinquent period of loans secured by real estate resulting in charge off	150 days
Maximum [Member]
Significant Accounting Policies [Line Items]
Loans secured by real estate delinquent period threshold for return to accrual status	90 days
Consumer loan delinquent period threshold for consideration for charge off	180 days
Estimated useful lives	10 years
Minimum [Member]
Significant Accounting Policies [Line Items]
Consumer loan delinquent period threshold for consideration for charge off	91 days
Estimated useful lives	5 years
Income tax benefit recognition criteria percentage threshold	50.00%

Acquisition and Divestiture - A

Acquisition and Divestiture - Additional Information (Detail) $ in Thousands	Nov. 01, 2015USD ($)Officeshares	Apr. 30, 2015USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Proceeds from sales of investment securities Available for sale			$ 534,160	$ 63,513	$ 5,654,850
Goodwill			4,593,112	4,593,112
Provision for credit losses			168,000	190,000	170,000
Gain on sale of business net of tax		$ 23,000
Gain on sale of business before tax		45,000
Goodwill recorded		$ 11,000
Revenue on sale of business					9,000
Hudson City [Member]
Business Acquisition [Line Items]
Number of banking offices acquired in New Jersey, Connecticut and New York \| Office	135
Gross amount of cash paid in the acquisition	$ 2,100,000
Business acquisition, purchase price	5,200,000
Assets acquired	36,700,000
Residential real estate loans	19,000,000
Investment securities	7,900,000
Liabilities assumed	31,500,000
Deposits	17,900,000
Borrowings	13,200,000
Proceeds from sales of investment securities Available for sale	5,800,000
Repayments of borrowings	10,600,000
Goodwill	1,100,000
Core deposit intangible asset	$ 132,000
Estimated useful lives	7 years
Merger-related expenses			$ 0	35,755	96,976
Provision for credit losses					$ 21,000
Estimated fair value of purchased impaired loans				$ 18,300,000
Hudson City [Member] \| Common Stock [Member]
Business Acquisition [Line Items]
Shares issued upon acquisition \| shares	25,953,950

Acquisition and Divestiture - P

Acquisition and Divestiture - Pro Forma Information (Detail) - USD ($) $ in Thousands	2 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015
Business Acquisition Pro Forma Information [Abstract]
Total revenues actual since acquisition through	$ 111,168
Net income (loss) actual since acquisition through	$ (21,175)
Total revenues		$ 5,132,662
Net income (loss)		$ 1,011,463

Acquisition and Divestiture - S

Acquisition and Divestiture - Summary of Merger-Related Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of merger-related expenses
Salaries and employee benefits	$ 1,650,729	$ 1,623,600	$ 1,549,530
Equipment and net occupancy	295,084	295,141	272,539
Outside data processing and software	184,670	172,389	164,133
Advertising and marketing	69,203	87,137	59,227
Printing, postage and supplies	35,960	39,546	38,491
Other costs of operations	771,442	682,014	660,475
Total other expense	3,140,325	3,047,485	2,822,932
Provision for credit losses	168,000	190,000	170,000
Hudson City [Member]
Summary of merger-related expenses
Salaries and employee benefits		5,334	51,287
Equipment and net occupancy		1,278	3
Outside data processing and software		1,067	785
Advertising and marketing		10,522	79
Printing, postage and supplies		1,482	504
Other costs of operations		16,072	23,318
Total other expense		35,755	75,976
Provision for credit losses			21,000
Total	$ 0	$ 35,755	$ 96,976

Investment Securities - Amortiz

Investment Securities - Amortized Cost and Estimated Fair Value of Investment Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Investment securities available for sale, amortized cost	$ 10,938,796	$ 13,338,301
Investment securities available for sale, gross unrealized gains	85,154	135,286
Investment securities available for sale, gross unrealized losses	127,666	141,515
Investment securities available for sale, estimated fair value	10,896,284	13,332,072
Amortized cost for held to maturity	3,353,213	2,457,278
Gross unrealized gains for held to maturity	29,919	38,662
Gross unrealized losses for held to maturity	41,370	44,718
Estimated fair value for held to maturity	3,341,762	2,451,222
Other securities, Amortized cost	415,028	461,118
Other securities, Estimated fair value	415,028	461,118
Total Amortized cost	14,707,037	16,256,697
Total for Gross unrealized gains	115,073	173,948
Total for Gross unrealized losses	169,036	186,233
Total for Estimated fair value	14,653,074	16,244,412
U.S. Treasury and Federal Agencies [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Investment securities available for sale, amortized cost	1,965,665	1,912,110
Investment securities available for sale, gross unrealized gains		386
Investment securities available for sale, gross unrealized losses	18,178	9,952
Investment securities available for sale, estimated fair value	1,947,487	1,902,544
Obligations of States and Political Subdivisions [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Investment securities available for sale, amortized cost	2,555	3,570
Investment securities available for sale, gross unrealized gains	36	77
Investment securities available for sale, gross unrealized losses	2	6
Investment securities available for sale, estimated fair value	2,589	3,641
Amortized cost for held to maturity	24,562	60,858
Gross unrealized gains for held to maturity	109	267
Gross unrealized losses for held to maturity	49	224
Estimated fair value for held to maturity	24,622	60,901
Government Issued or Guaranteed [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Investment securities available for sale, amortized cost	8,755,482	10,980,507
Investment securities available for sale, gross unrealized gains	59,497	88,343
Investment securities available for sale, gross unrealized losses	98,587	113,989
Investment securities available for sale, estimated fair value	8,716,392	10,954,861
Amortized cost for held to maturity	3,187,953	2,233,173
Gross unrealized gains for held to maturity	27,236	37,498
Gross unrealized losses for held to maturity	13,746	7,374
Estimated fair value for held to maturity	3,201,443	2,263,297
Privately Issued [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Investment securities available for sale, amortized cost	28	45
Investment securities available for sale, gross unrealized losses		1
Investment securities available for sale, estimated fair value	28	44
Amortized cost for held to maturity	135,688	157,704
Gross unrealized gains for held to maturity	2,574	897
Gross unrealized losses for held to maturity	27,575	37,120
Estimated fair value for held to maturity	110,687	121,481
Other Debt Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Investment securities available for sale, amortized cost	136,905	134,105
Investment securities available for sale, gross unrealized gains	2,402	1,407
Investment securities available for sale, gross unrealized losses	10,475	16,996
Investment securities available for sale, estimated fair value	128,832	118,516
Amortized cost for held to maturity	5,010	5,543
Estimated fair value for held to maturity	5,010	5,543
Equity Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Investment securities available for sale, amortized cost	78,161	307,964
Investment securities available for sale, gross unrealized gains	23,219	45,073
Investment securities available for sale, gross unrealized losses	424	571
Investment securities available for sale, estimated fair value	$ 100,956	$ 352,466

Investment Securities - Additio

Investment Securities - Additional Information (Detail)	12 Months Ended
Investment Securities - Additional Information (Detail)	Dec. 31, 2017USD ($)Investment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Investment Holdings [Line Items]
Gross realized gains on investment securities	$ 23,251,000	$ 30,545,000
Gross realized gains(loss) on sale of investment securities	$ 0	0	$ 0
Number of investment securities with aggregate gross unrealized losses \| Investment	1,163
Unrealized losses on individual investment securities	$ 169,036,000	186,233,000
Cost method investment securities	415,000,000
Investment securities pledged to secure debt carrying value	2,401,871,000
Pledged securities that can be sold or repledged	487,151,000	1,203,473,000
Available-for-Sale Securities [Member]
Investment Holdings [Line Items]
Investment securities pledged to secure debt carrying value	1,942,287,000
Collateralized Debt Obligations [Member]
Investment Holdings [Line Items]
Net gain on securities sold		$ 30,000,000
Collateralized Debt Obligations [Member] \| Fannie Mae And Freddie Mac Preferred Stock [Member]
Investment Holdings [Line Items]
Net gain on securities sold	$ 18,000,000
Government Agency [Member]
Investment Holdings [Line Items]
Number of investment securities that exceeded ten percent of shareholders' equity \| Investment	0
Non-U.S. Government [Member]
Investment Holdings [Line Items]
Number of investment securities that exceeded ten percent of shareholders' equity \| Investment	0
Government Issued or Guaranteed [Member]
Investment Holdings [Line Items]
Number of investment securities that exceeded ten percent of shareholders' equity \| Investment	0

Investment Securities - Investm

Investment Securities - Investment Ratings of All Privately Issued Mortgage-Backed Securities and Other Debt Securities (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Amortized Cost	$ 304,748
Total securities with disclosed rating, Estimated Fair Value	271,768
A or Better [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	46,313
BBB [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	61,070
BB [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	32,684
B or Less [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	87,233
Not Rated [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	44,468
Obligations of States and Political Subdivisions [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Amortized Cost	27,117
Total securities with disclosed rating, Estimated Fair Value	27,211
Obligations of States and Political Subdivisions [Member] \| A or Better [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	15,874
Obligations of States and Political Subdivisions [Member] \| Not Rated [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	11,337
Privately Issued [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Amortized Cost	135,716
Total securities with disclosed rating, Estimated Fair Value	110,715
Privately Issued [Member] \| A or Better [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	23,459
Privately Issued [Member] \| BBB [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	16
Privately Issued [Member] \| B or Less [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	87,233
Privately Issued [Member] \| Not Rated [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	7
Other Debt Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Amortized Cost	141,915
Total securities with disclosed rating, Estimated Fair Value	133,842
Other Debt Securities [Member] \| A or Better [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	6,980
Other Debt Securities [Member] \| BBB [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	61,054
Other Debt Securities [Member] \| BB [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	32,684
Other Debt Securities [Member] \| Not Rated [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Total securities with disclosed rating, Estimated Fair Value	$ 33,124

Investment Securities - Amort64

Investment Securities - Amortized Cost and Estimated Fair Value of Collateralized Mortgage Obligations (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Amortized Cost And Fair Value Debt Securities [Abstract]
Collateralized mortgage obligations, Amortized cost	$ 138,527	$ 162,027
Collateralized mortgage obligations, Estimated fair value	$ 113,516	$ 125,848

Investment Securities - Amort65

Investment Securities - Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt securities available for sale:
Due in one year or less	$ 616,908
Due after one year through five years	1,356,410
Due after five years through ten years	72,642
Due after ten years	59,165
Total available for sale (amortized cost)	2,105,125
Mortgage-backed securities available for sale	8,755,510
Total	10,860,635
Debt securities held to maturity:
Due in one year or less	14,622
Due after one year through five years	9,844
Due after five years through ten years	96
Due after ten years	5,010
Total available for held to maturity (amortized cost)	29,572
Mortgage-backed securities held to maturity	3,323,641
Amortized cost for held to maturity	3,353,213	$ 2,457,278
Debt securities available for sale:
Due in one year or less	613,866
Due after one year through five years	1,341,344
Due after five years through ten years	72,580
Due after ten years	51,118
Total available for sale (fair value)	2,078,908
Mortgage-backed securities available for sale	8,716,420
Total	10,795,328
Debt securities held to maturity:
Due in one year or less	14,656
Due after one year through five years	9,865
Due after five years through ten years	101
Due after ten years	5,010
Total available for held to maturity (fair value)	29,632
Mortgage-backed securities held to maturity	3,312,130
Total	$ 3,341,762	$ 2,451,222

Investment Securities - Inves66

Investment Securities - Investment Securities in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Estimated fair value, Less than 12 months	$ 2,387,341	$ 8,458,946
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	(15,482)	(123,747)
Estimated fair value, 12 months or more	4,887,991	169,469
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	(112,184)	(17,768)
Held to maturity, Estimated fair value, Less than 12 months	1,339,774	654,731
Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses	(8,256)	(8,190)
Held to maturity, Estimated fair value, 12 months or more	327,060	86,388
Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Aggregate Losses	(33,114)	(36,528)
Total investment securities, fair value less than 12 months	3,727,115	9,113,677
Investment Securities Continuous Unrealized Loss Position Less Than Twelve Months Aggregate Losses	(23,738)	(131,937)
Total of investment securities, fair value, 12 Months or More	5,215,051	255,857
Investment Securities Continuous Unrealized Loss Position Twelve Months or Longer Aggregate Losses	(145,298)	(54,296)
U.S. Treasury and Federal Agencies [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Estimated fair value, Less than 12 months	278,132	1,710,241
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	(1,761)	(9,950)
Estimated fair value, 12 months or more	1,669,355	2,295
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	(16,417)	(2)
Obligations of States and Political Subdivisions [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Estimated fair value, 12 months or more	474	593
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	(2)	(6)
Held to maturity, Estimated fair value, Less than 12 months	2,954	17,988
Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses	(4)	(126)
Held to maturity, Estimated fair value, 12 months or more	6,110	11,891
Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Aggregate Losses	(45)	(98)
Government Issued or Guaranteed [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Estimated fair value, Less than 12 months	2,106,142	6,730,829
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	(13,695)	(113,374)
Estimated fair value, 12 months or more	3,138,841	81,003
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	(84,892)	(615)
Held to maturity, Estimated fair value, Less than 12 months	1,331,759	618,832
Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses	(7,036)	(6,842)
Held to maturity, Estimated fair value, 12 months or more	265,695	17,481
Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Aggregate Losses	(6,710)	(532)
Privately Issued Mortgage-Backed Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Estimated fair value, 12 months or more		27
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses		(1)
Other Debt Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Estimated fair value, Less than 12 months	3,067	100
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	(26)	(1)
Estimated fair value, 12 months or more	61,159	85,400
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	(10,449)	(16,995)
Equity Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Estimated fair value, Less than 12 months		17,776
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses		(422)
Estimated fair value, 12 months or more	18,162	151
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	(424)	(149)
Privately Issued [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Held to maturity, Estimated fair value, Less than 12 months	5,061	17,911
Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses	(1,216)	(1,222)
Held to maturity, Estimated fair value, 12 months or more	55,255	57,016
Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Aggregate Losses	$ (26,359)	$ (35,898)

Loans and Leases - Total Loans

Loans and Leases - Total Loans and Leases Outstanding (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Loans
Commercial, financial, etc.	$ 20,474,696	$ 21,351,119
Real estate:
Residential	19,619,259	22,584,141
Commercial	25,345,779	25,550,057
Construction	8,125,925	8,066,756
Consumer	13,251,665	12,130,094
Total loans	86,817,324	89,682,167
Leases
Commercial	1,425,562	1,419,510
Total loans and leases	88,242,886	91,101,677
Unearned discount	(253,903)	(248,261)
Loans and leases, net of unearned discount	$ 87,988,983	$ 90,853,416

Loans and Leases - Additional I

Loans and Leases - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loans And Leases Receivable [Line Items]
Commercial real estate loans held for sale	$ 22,000,000	$ 643,000,000
Charges incurred for reimbursement of loan	0	0	$ 0
Interest income that would have been recognized on nonaccrual and renegotiated loans if those loans were accruing interest at their originally contracted terms	63,872,000	68,371,000	56,784,000
Interest on nonaccrual and renegotiated loans included in interest income	31,425,000	33,941,000	$ 30,735,000
Contractual principal and interest payments	410,000,000	578,000,000
Guaranteed amount included in the estimated residual value of leased assets associated with direct financing leases	37,000,000	47,000,000
Amount of foreclosed residential real estate property held	108,000,000	129,000,000
Loans secured by residential real estate that were in the process of foreclosure	$ 497,000,000	506,000,000
Percentage loans in the process of foreclosure, serviced by other entities, classified as purchased impaired	45.00%
Percentage loans in the process of foreclosure, serviced by other entities, classified as government guaranteed	19.00%
Director and Certain Officers [Member]
Loans And Leases Receivable [Line Items]
Exclusion limit of loans from related party disclosure	Less than $60,000
Borrowing by directors and certain officers of M&T and its banking subsidiaries and their associates	$ 93,103,000	$ 63,543,000
New borrowings by directors, certain officers and their associates	88,077,000
Repayments and other reductions of borrowings by directors, certain officers and their associates	$ 58,517,000
Maximum [Member]
Loans And Leases Receivable [Line Items]
Purchased impaired loans as a percentage of total assets	1.00%	1.00%
Commercial Real Estate [Member]
Loans And Leases Receivable [Line Items]
Loans serviced for others sold with credit recourse	$ 3,300,000,000
Loans pledged to secure outstanding borrowings from the FHLB of New York	12,700,000,000
Residential Mortgage Loans [Member]
Loans And Leases Receivable [Line Items]
Mortgage loans held for sale	356,000,000	$ 414,000,000
Loans pledged to secure outstanding borrowings from the FHLB of New York	15,300,000,000
Commercial Loans and Leases [Member]
Loans And Leases Receivable [Line Items]
Loans pledged to secure outstanding borrowings from the FHLB of New York	11,900,000,000
Home Equity Loans and Lines of Credit [Member]
Loans And Leases Receivable [Line Items]
Loans pledged to secure outstanding borrowings from the FHLB of New York	2,300,000,000
Other Consumer Loans [Member]
Loans And Leases Receivable [Line Items]
Loans pledged to secure outstanding borrowings from the FHLB of New York	$ 5,200,000,000

Loans and Leases - Summary of C

Loans and Leases - Summary of Current, Past Due and Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	$ 85,325,604	$ 87,968,321
30-89 Days Past Due	1,078,943	1,025,245
Accruing Loans Past Due 90 Days or More	244,405	300,659
Purchased Impaired	410,015	578,032
Nonaccrual	882,598	920,015
Loans and leases, net of unearned discount	87,988,983	90,853,416
Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	47,418	61,144
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	21,332,234	22,287,857
30-89 Days Past Due	167,756	53,503
Accruing Loans Past Due 90 Days or More	1,322	6,195
Purchased Impaired	21	641
Nonaccrual	240,991	261,434
Loans and leases, net of unearned discount	21,742,651	22,610,047
Commercial, Financial, Leasing, etc. [Member] \| Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	327	417
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	24,910,381	25,076,684
30-89 Days Past Due	166,305	183,531
Accruing Loans Past Due 90 Days or More	4,444	7,054
Purchased Impaired	16,815	31,404
Nonaccrual	184,982	176,201
Loans and leases, net of unearned discount	25,288,943	25,487,744
Commercial [Member] \| Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	6,016	12,870
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	1,618,973	1,884,989
30-89 Days Past Due	5,159	4,667
Accruing Loans Past Due 90 Days or More		5
Purchased Impaired	1,135	14,006
Nonaccrual	6,451	16,707
Loans and leases, net of unearned discount	1,631,718	1,922,326
Residential Builder and Developer [Member] \| Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More		1,952
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	6,407,451	5,985,118
30-89 Days Past Due	23,467	77,701
Accruing Loans Past Due 90 Days or More		922
Purchased Impaired	4,706	14,274
Nonaccrual	10,088	18,111
Loans and leases, net of unearned discount	6,445,712	6,096,324
Other Commercial Construction [Member] \| Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More		198
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	15,376,759	17,631,377
30-89 Days Past Due	474,372	485,468
Accruing Loans Past Due 90 Days or More	233,437	281,298
Purchased Impaired	282,102	378,549
Nonaccrual	235,834	229,242
Loans and leases, net of unearned discount	16,610,086	19,017,471
Residential [Member] \| Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	7,582	11,537
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	2,718,019	3,239,344
30-89 Days Past Due	83,898	88,366
Purchased Impaired	105,236	139,158
Nonaccrual	96,105	106,573
Loans and leases, net of unearned discount	3,003,258	3,573,441
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	5,171,345	5,502,091
30-89 Days Past Due	38,546	44,565
Nonaccrual	74,500	81,815
Loans and leases, net of unearned discount	5,293,782	5,641,149
Home Equity Lines and Loans [Member] \| Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	9,391	12,678
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	3,441,371	2,869,232
30-89 Days Past Due	78,511	56,158
Nonaccrual	23,781	18,674
Loans and leases, net of unearned discount	3,543,663	2,944,065
Automobile [Member] \| Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More		1
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	4,349,071	3,491,629
30-89 Days Past Due	40,929	31,286
Accruing Loans Past Due 90 Days or More	5,202	5,185
Nonaccrual	9,866	11,258
Loans and leases, net of unearned discount	4,429,170	3,560,849
Other [Member] \| Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	$ 24,102	$ 21,491

Loans and Leases - Outstanding

Loans and Leases - Outstanding Principal Balance and Carrying Amount of Loans and Included in Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Outstanding principal and carrying value of acquired loans recorded at fair value
Outstanding principal balance	$ 1,394,188	$ 2,311,699
Carrying amount	1,003,399	1,804,271
Commercial, Financial, Leasing, etc. [Member]
Outstanding principal and carrying value of acquired loans recorded at fair value
Carrying amount	31,105	59,928
Commercial Real Estate [Member]
Outstanding principal and carrying value of acquired loans recorded at fair value
Carrying amount	228,054	456,820
Residential Real Estate [Member]
Outstanding principal and carrying value of acquired loans recorded at fair value
Carrying amount	620,827	799,802
Consumer [Member]
Outstanding principal and carrying value of acquired loans recorded at fair value
Carrying amount	$ 123,413	$ 487,721

Loans and Leases - Summary of71

Loans and Leases - Summary of Changes in Accretable Yield for Acquired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Purchased Impaired [Member]
Summary of changes in Accretable Yield for loans acquired at a discount
Balance at beginning of period	$ 154,233	$ 184,618	$ 76,518
Additions			117,251
Interest income	(47,452)	(52,769)	(28,551)
Reclassifications from nonaccretable balance	51,137	22,384	19,400
Balance at end of period	157,918	154,233	184,618
Other Acquired [Member]
Summary of changes in Accretable Yield for loans acquired at a discount
Balance at beginning of period	201,153	296,434	397,379
Interest income	(82,605)	(123,044)	(158,260)
Reclassifications from nonaccretable balance	16,437	22,677	49,930
Other	(1,823)	5,086	7,385
Balance at end of period	$ 133,162	$ 201,153	$ 296,434

Loans and Leases and the Allowa

Loans and Leases and the Allowance for Credit Losses - Loan Modification Activities that were Considered Troubled Debt Restructurings (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)Modification	Dec. 31, 2016USD ($)Modification	Dec. 31, 2015USD ($)Modification
Financing Receivable Modifications [Line Items]
Number of modifications \| Modification	654	739	817
Pre- modification recorded investment	$ 216,063	$ 279,696	$ 204,800
Post- modification	$ 191,522	$ 268,415	$ 198,405
Commercial Real Estate [Member]
Financing Receivable Modifications [Line Items]
Number of modifications \| Modification	83	81	58
Pre- modification recorded investment	$ 44,924	$ 44,870	$ 56,893
Post- modification	40,882	43,737	55,717
Principal Deferral [Member]
Financing Receivable Modifications [Line Items]
Post- modification	62,302	164,883	123,206
Principal Deferral [Member] \| Commercial Real Estate [Member]
Financing Receivable Modifications [Line Items]
Post- modification	17,039	23,558	48,388
Other [Member]
Financing Receivable Modifications [Line Items]
Post- modification	7,818	4,676	17,683
Other [Member] \| Commercial Real Estate [Member]
Financing Receivable Modifications [Line Items]
Post- modification	868	4,576	4,087
Combination of Concession Types [Member]
Financing Receivable Modifications [Line Items]
Post- modification	121,402	98,856	57,516
Combination of Concession Types [Member] \| Commercial Real Estate [Member]
Financing Receivable Modifications [Line Items]
Post- modification	$ 22,975	$ 15,603	$ 3,242
Residential [Member]
Financing Receivable Modifications [Line Items]
Number of modifications \| Modification	141	119	85
Pre- modification recorded investment	$ 31,827	$ 20,057	$ 10,485
Post- modification	34,607	21,138	11,072
Residential [Member] \| Principal Deferral [Member]
Financing Receivable Modifications [Line Items]
Post- modification	16,633	11,771	6,528
Residential [Member] \| Other [Member]
Financing Receivable Modifications [Line Items]
Post- modification			267
Residential [Member] \| Combination of Concession Types [Member]
Financing Receivable Modifications [Line Items]
Post- modification	$ 17,974	$ 9,367	$ 4,277
Residential Limited Documentation [Member]
Financing Receivable Modifications [Line Items]
Number of modifications \| Modification	20	21	11
Pre- modification recorded investment	$ 4,230	$ 3,560	$ 1,962
Post- modification	4,572	3,964	2,072
Residential Limited Documentation [Member] \| Principal Deferral [Member]
Financing Receivable Modifications [Line Items]
Post- modification	911	1,047	437
Residential Limited Documentation [Member] \| Combination of Concession Types [Member]
Financing Receivable Modifications [Line Items]
Post- modification	$ 3,661	$ 2,917	$ 1,635
Home Equity Lines and Loans [Member]
Financing Receivable Modifications [Line Items]
Number of modifications \| Modification	110	103	71
Pre- modification recorded investment	$ 10,049	$ 11,870	$ 7,378
Post- modification	10,213	11,871	7,379
Home Equity Lines and Loans [Member] \| Principal Deferral [Member]
Financing Receivable Modifications [Line Items]
Post- modification	1,137	761	2,175
Home Equity Lines and Loans [Member] \| Other [Member]
Financing Receivable Modifications [Line Items]
Post- modification	491
Home Equity Lines and Loans [Member] \| Combination of Concession Types [Member]
Financing Receivable Modifications [Line Items]
Post- modification	$ 8,585	$ 11,110	$ 5,204
Automobile [Member]
Financing Receivable Modifications [Line Items]
Number of modifications \| Modification	69	163	302
Pre- modification recorded investment	$ 1,378	$ 1,264	$ 3,053
Post- modification	1,378	1,264	3,053
Automobile [Member] \| Principal Deferral [Member]
Financing Receivable Modifications [Line Items]
Post- modification	1,203	1,124	1,818
Automobile [Member] \| Other [Member]
Financing Receivable Modifications [Line Items]
Post- modification		55	287
Automobile [Member] \| Combination of Concession Types [Member]
Financing Receivable Modifications [Line Items]
Post- modification	$ 175	$ 85	$ 948
Other [Member]
Financing Receivable Modifications [Line Items]
Number of modifications \| Modification	9	79	155
Pre- modification recorded investment	$ 160	$ 1,209	$ 2,507
Post- modification	160	1,209	2,507
Other [Member] \| Principal Deferral [Member]
Financing Receivable Modifications [Line Items]
Post- modification	$ 160	968	1,995
Other [Member] \| Other [Member]
Financing Receivable Modifications [Line Items]
Post- modification		45	116
Other [Member] \| Combination of Concession Types [Member]
Financing Receivable Modifications [Line Items]
Post- modification		$ 196	$ 396
Residential Builder and Developer [Member]
Financing Receivable Modifications [Line Items]
Number of modifications \| Modification	3	6	2
Pre- modification recorded investment	$ 12,291	$ 39,660	$ 10,650
Post- modification	10,879	38,081	10,598
Residential Builder and Developer [Member] \| Principal Deferral [Member]
Financing Receivable Modifications [Line Items]
Post- modification		22,958	$ 10,598
Residential Builder and Developer [Member] \| Combination of Concession Types [Member]
Financing Receivable Modifications [Line Items]
Post- modification	$ 10,879	$ 15,123
Other Commercial Construction [Member]
Financing Receivable Modifications [Line Items]
Number of modifications \| Modification	2	3	6
Pre- modification recorded investment	$ 168	$ 3,113	$ 10,743
Post- modification	168	3,032	10,835
Other Commercial Construction [Member] \| Principal Deferral [Member]
Financing Receivable Modifications [Line Items]
Post- modification	$ 168	250	460
Other Commercial Construction [Member] \| Combination of Concession Types [Member]
Financing Receivable Modifications [Line Items]
Post- modification		$ 2,782	$ 10,375
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable Modifications [Line Items]
Number of modifications \| Modification	217	164	127
Pre- modification recorded investment	$ 111,036	$ 154,093	$ 101,129
Post- modification	88,663	144,119	95,172
Commercial, Financial, Leasing, etc. [Member] \| Principal Deferral [Member]
Financing Receivable Modifications [Line Items]
Post- modification	25,051	102,446	50,807
Commercial, Financial, Leasing, etc. [Member] \| Other [Member]
Financing Receivable Modifications [Line Items]
Post- modification	6,459		12,926
Commercial, Financial, Leasing, etc. [Member] \| Combination of Concession Types [Member]
Financing Receivable Modifications [Line Items]
Post- modification	$ 57,153	$ 41,673	$ 31,439

Loans and Leases - Summary of L

Loans and Leases - Summary of Lease Financing Receivables (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Direct financings:
Lease payments receivable	$ 1,159,584	$ 1,136,815
Estimated residual value of leased assets	89,666	79,449
Unearned income	(110,261)	(107,535)
Investment in direct financings	1,138,989	1,108,729
Leveraged leases:
Lease payments receivable	87,821	92,918
Estimated residual value of leased assets	88,491	110,328
Unearned income	(35,792)	(38,760)
Investment in leveraged leases	140,520	164,486
Total investment in leases	1,279,509	1,273,215
Deferred taxes payable arising from leveraged leases	$ 81,359	$ 139,067

Loans and Leases - Minimum Futu

Loans and Leases - Minimum Future Lease Payments to be Received from Lease Financings (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Receivables [Abstract]
2,018	$ 310,207
2,019	297,599
2,020	208,613
2,021	150,553
2,022	96,871
Later years	183,562
Total	$ 1,247,405

Allowance for Credit Losses - C

Allowance for Credit Losses - Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 988,997	$ 955,992	$ 919,562
Provision for credit losses	168,000	190,000	170,000
Net charge-offs
Charge-offs	(224,598)	(231,255)	(198,373)
Recoveries	84,799	74,260	64,803
Net (charge-offs) recoveries	(139,799)	(156,995)	(133,570)
Ending balance	1,017,198	988,997	955,992
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	330,833	300,404	288,038
Provision for credit losses	41,511	59,506	43,065
Net charge-offs
Charge-offs	(64,941)	(59,244)	(60,983)
Recoveries	21,196	30,167	30,284
Net (charge-offs) recoveries	(43,745)	(29,077)	(30,699)
Ending balance	328,599	330,833	300,404
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	362,719	326,831	307,927
Provision for credit losses	6,715	33,627	25,768
Net charge-offs
Charge-offs	(7,931)	(4,805)	(16,487)
Recoveries	12,582	7,066	9,623
Net (charge-offs) recoveries	4,651	2,261	(6,864)
Ending balance	374,085	362,719	326,831
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	61,127	72,238	61,910
Provision for credit losses	16,094	6,902	19,133
Net charge-offs
Charge-offs	(20,799)	(26,133)	(13,116)
Recoveries	8,983	8,120	4,311
Net (charge-offs) recoveries	(11,816)	(18,013)	(8,805)
Ending balance	65,405	61,127	72,238
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	156,288	178,320	186,033
Provision for credit losses	103,410	90,134	79,489
Net charge-offs
Charge-offs	(130,927)	(141,073)	(107,787)
Recoveries	42,038	28,907	20,585
Net (charge-offs) recoveries	(88,889)	(112,166)	(87,202)
Ending balance	170,809	156,288	178,320
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	78,030	78,199	75,654
Provision for credit losses	270	(169)	2,545
Net charge-offs
Ending balance	$ 78,300	$ 78,030	$ 78,199

Allowance for Credit Losses - I

Allowance for Credit Losses - Impaired Loans and Leases (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Recorded investment with related allowance	$ 499,152	$ 484,498
Unpaid principal balance with related allowance	585,903	558,385
Related allowance	75,762	83,054
Recorded investment with no related allowance	261,157	276,634
Unpaid principal balance with no related allowance	314,587	351,788
Recorded investment	760,309	761,132
Unpaid principal balance	900,490	910,173
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment with related allowance	67,199	71,862
Unpaid principal balance with related allowance	75,084	86,666
Related allowance	9,140	11,620
Recorded investment with no related allowance	138,356	113,276
Unpaid principal balance with no related allowance	149,716	121,846
Recorded investment	205,555	185,138
Unpaid principal balance	224,800	208,512
Automobile [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment with related allowance	13,498	16,982
Unpaid principal balance with related allowance	15,737	18,272
Related allowance	2,811	3,740
Recorded investment	13,498	16,982
Unpaid principal balance	15,737	18,272
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment with related allowance	177,250	168,072
Unpaid principal balance with related allowance	194,257	184,432
Related allowance	45,488	48,480
Recorded investment with no related allowance	89,126	100,805
Unpaid principal balance with no related allowance	115,327	124,786
Recorded investment	266,376	268,877
Unpaid principal balance	309,584	309,218
Residential Builder and Developer [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment with related allowance	5,320	7,396
Unpaid principal balance with related allowance	5,641	8,361
Related allowance	308	506
Recorded investment with no related allowance	5,057	14,368
Unpaid principal balance with no related allowance	5,296	21,124
Recorded investment	10,377	21,764
Unpaid principal balance	10,937	29,485
Other Commercial Construction [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment with related allowance	4,817	2,475
Unpaid principal balance with related allowance	20,357	2,731
Related allowance	647	448
Recorded investment with no related allowance	5,456	15,933
Unpaid principal balance with no related allowance	9,130	35,281
Recorded investment	10,273	18,408
Unpaid principal balance	29,487	38,012
Residential [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment with related allowance	101,724	86,680
Unpaid principal balance with related allowance	122,602	105,944
Related allowance	4,000	3,457
Recorded investment with no related allowance	13,574	16,823
Unpaid principal balance with no related allowance	18,980	24,161
Recorded investment	115,298	103,503
Unpaid principal balance	141,582	130,105
Residential Limited Documentation [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment with related allowance	77,277	82,547
Unpaid principal balance with related allowance	92,439	97,718
Related allowance	3,900	6,000
Recorded investment with no related allowance	9,588	15,429
Unpaid principal balance with no related allowance	16,138	24,590
Recorded investment	86,865	97,976
Unpaid principal balance	108,577	122,308
Home Equity Lines and Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment with related allowance	48,847	44,693
Unpaid principal balance with related allowance	53,914	48,965
Related allowance	8,812	8,027
Recorded investment	48,847	44,693
Unpaid principal balance	53,914	48,965
Other [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment with related allowance	3,220	3,791
Unpaid principal balance with related allowance	5,872	5,296
Related allowance	656	776
Recorded investment	3,220	3,791
Unpaid principal balance	$ 5,872	$ 5,296

Allowance for Credit Losses -77

Allowance for Credit Losses - Interest Income Recognized on Impaired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	$ 748,598	$ 769,259	$ 768,501
Interest Income Recognized, Total	31,983	31,397	27,643
Interest Income Recognized, Cash Basis	21,316	21,885	19,046
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	207,616	175,877	166,628
Interest Income Recognized, Total	4,497	4,878	6,243
Interest Income Recognized, Cash Basis	4,497	4,878	6,243
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	240,157	277,647	236,201
Interest Income Recognized, Total	3,894	8,342	2,933
Interest Income Recognized, Cash Basis	3,894	8,342	2,933
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	16,209	29,237	59,457
Interest Income Recognized, Total	6,419	2,300	335
Interest Income Recognized, Cash Basis	6,419	2,300	335
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	15,142	19,697	20,276
Interest Income Recognized, Total	1,001	644	2,311
Interest Income Recognized, Cash Basis	1,001	644	2,311
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	110,646	98,394	101,483
Interest Income Recognized, Total	7,177	6,227	6,188
Interest Income Recognized, Cash Basis	3,406	3,154	4,037
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	93,097	103,060	118,449
Interest Income Recognized, Total	5,981	5,999	6,380
Interest Income Recognized, Cash Basis	1,607	1,975	2,638
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	47,323	36,493	21,523
Interest Income Recognized, Total	1,681	1,325	905
Interest Income Recognized, Cash Basis	400	410	261
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	15,045	19,636	25,675
Interest Income Recognized, Total	1,025	1,242	1,619
Interest Income Recognized, Cash Basis	81	99	175
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	3,363	9,218	18,809
Interest Income Recognized, Total	308	440	729
Interest Income Recognized, Cash Basis	$ 11	$ 83	$ 113

Allowance for Credit Losses - S

Allowance for Credit Losses - Summary of Loan Grades (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	$ 87,988,983	$ 90,853,416
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	21,742,651	22,610,047
Commercial, Financial, Leasing, etc. [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	20,490,486	21,398,581
Commercial, Financial, Leasing, etc. [Member] \| Criticized Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,011,174	950,032
Commercial, Financial, Leasing, etc. [Member] \| Criticized Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	240,991	261,434
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	25,288,943	25,487,744
Commercial [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	24,380,184	24,570,269
Commercial [Member] \| Criticized Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	723,777	741,274
Commercial [Member] \| Criticized Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	184,982	176,201
Residential Builder and Developer [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,631,718	1,922,326
Residential Builder and Developer [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,485,148	1,789,071
Residential Builder and Developer [Member] \| Criticized Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	140,119	116,548
Residential Builder and Developer [Member] \| Criticized Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	6,451	16,707
Other Commercial Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	6,445,712	6,096,324
Other Commercial Construction [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	6,270,812	5,912,351
Other Commercial Construction [Member] \| Criticized Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	164,812	165,862
Other Commercial Construction [Member] \| Criticized Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	$ 10,088	$ 18,111

Allowance for Credit Losses - A

Allowance for Credit Losses - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Minimum delinquency period for loan level collectability analysis consumer mortgage	150 days
Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of loans for which partial charge-off has been recognized	$ 34	$ 44
Mortgage loans on real real estate not requiring charge off due to collateral carrying amount	20	16
Home Equity Loans and Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of loans for which partial charge-off has been recognized	25	32
Mortgage loans on real real estate not requiring charge off due to collateral carrying amount	$ 32	$ 39

Allowance for Credit Losses -80

Allowance for Credit Losses - Allocation of Allowance for Credit Losses on Basis of Company's Impairment Methodology (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	$ 75,762	$ 82,980
Allowance for credit losses	853,276	822,392
Allowance for credit losses	1,017,198	988,997	$ 955,992	$ 919,562
Purchased Impaired [Member] \| Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	9,860	5,595
Allocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	938,898	910,967
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	78,300	78,030	$ 78,199	$ 75,654
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	45,488	48,480
Allowance for credit losses	283,111	282,353
Commercial, Financial, Leasing, etc. [Member] \| Allocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	328,599	330,833
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	10,095	12,500
Allowance for credit losses	363,990	348,301
Commercial Real Estate [Member] \| Purchased Impaired [Member] \| Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses		1,918
Commercial Real Estate [Member] \| Allocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	374,085	362,719
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	7,900	9,457
Allowance for credit losses	47,645	47,993
Residential Real Estate [Member] \| Purchased Impaired [Member] \| Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	9,860	3,677
Residential Real Estate [Member] \| Allocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	65,405	61,127
Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	12,279	12,543
Allowance for credit losses	158,530	143,745
Consumer Loans [Member] \| Allocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	$ 170,809	$ 156,288

Allowance for Credit Losses - R

Allowance for Credit Losses - Recorded Investment in Loans and Leases on Basis of Company's Impairment Methodology (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in loans and leases, individually evaluated for impairment	$ 760,309	$ 760,452
Recorded investment in loans and leases, collectively evaluated for impairment	86,818,659	89,514,932
Recorded investment in loans and leases, purchased impaired	410,015	578,032
Loans and leases, net of unearned discount	87,988,983	90,853,416
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in loans and leases, individually evaluated for impairment	266,376	268,877
Recorded investment in loans and leases, collectively evaluated for impairment	21,476,254	22,340,529
Recorded investment in loans and leases, purchased impaired	21	641
Loans and leases, net of unearned discount	21,742,651	22,610,047
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in loans and leases, individually evaluated for impairment	226,205	224,630
Recorded investment in loans and leases, collectively evaluated for impairment	33,117,512	33,222,080
Recorded investment in loans and leases, purchased impaired	22,656	59,684
Loans and leases, net of unearned discount	33,366,373	33,506,394
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in loans and leases, individually evaluated for impairment	202,163	201,479
Recorded investment in loans and leases, collectively evaluated for impairment	19,023,843	21,871,726
Recorded investment in loans and leases, purchased impaired	387,338	517,707
Loans and leases, net of unearned discount	19,613,344	22,590,912
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded investment in loans and leases, individually evaluated for impairment	65,565	65,466
Recorded investment in loans and leases, collectively evaluated for impairment	13,201,050	12,080,597
Loans and leases, net of unearned discount	$ 13,266,615	$ 12,146,063

Premises and Equipment - Summar

Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Land	$ 98,077	$ 104,671
Buildings	454,610	448,442
Leasehold improvements	239,956	232,936
Premises and equipment, gross	1,487,347	1,437,117
Less: accumulated depreciation and amortization	840,896	761,854
Premises and equipment, net	646,451	675,263
Owned Assets [Member]
Property, Plant and Equipment [Line Items]
Furniture and equipment	676,665	636,219
Less: accumulated depreciation and amortization	830,832	756,245
Capital Leases [Member]
Property, Plant and Equipment [Line Items]
Furniture and equipment	18,039	14,849
Less: accumulated depreciation and amortization	$ 10,064	$ 5,609

Premises and Equipment - Additi

Premises and Equipment - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment Capitalized Interest Costs [Abstract]
Net lease expense for all operating leases	$ 114,362,000	$ 113,663,000	$ 102,356,000

Capitalized Servicing Assets -

Capitalized Servicing Assets - Changes in Capitalized Servicing Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Servicing Asset at Amortized Cost [Line Items]
Amortized value, Beginning balance	$ 221,115	$ 202,724	$ 186,917
Originations	63,412	68,735	65,470
Purchases	699	638	243
Amortization	(56,172)	(50,982)	(49,906)
Amortized value, ending balance	229,054	221,115	202,724
Ending balance, net	229,054	221,115	202,724
Residential Mortgage Loans [Member]
Servicing Asset at Amortized Cost [Line Items]
Amortized value, Beginning balance	117,351	118,303	109,871
Originations	28,792	28,618	35,556
Purchases	699	638	243
Amortization	(31,864)	(30,208)	(27,367)
Amortized value, ending balance	114,978	117,351	118,303
Ending balance, net	114,978	117,351	118,303
Commercial Mortgage Loans [Member]
Servicing Asset at Amortized Cost [Line Items]
Amortized value, Beginning balance	103,764	83,692	72,939
Originations	34,620	40,117	29,914
Amortization	(24,308)	(20,045)	(19,161)
Amortized value, ending balance	114,076	103,764	83,692
Ending balance, net	$ 114,076	103,764	83,692
Other [Member]
Servicing Asset at Amortized Cost [Line Items]
Amortized value, Beginning balance		729	4,107
Amortization		$ (729)	(3,378)
Amortized value, ending balance			729
Ending balance, net			$ 729

Capitalized Servicing Assets 85

Capitalized Servicing Assets - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Residential Mortgage Loans [Member]
Servicing Assets at Fair Value [Line Items]
Mortgage loans serviced for others	$ 22,600	$ 22,800	$ 22,600	$ 22,800	$ 23,900
Estimated fair value of capitalized mortgage loan servicing assets	$ 234	$ 235	$ 234	$ 235
Weighted average discount rates used to estimate fair value of capitalized mortgaged loan servicing assets	12.20%	12.20%
Residential Mortgage Loans [Member] \| LIBOR [Member]
Servicing Assets at Fair Value [Line Items]
Discounted rate represented weighted-average option-adjusted basis spread point percentage			10.67%	10.95%
Residential Mortgage Sub Servicing Loan [Member]
Servicing Assets at Fair Value [Line Items]
Mortgage loans serviced for others	$ 56,600	$ 30,400	$ 56,600	$ 30,400	37,800
Commercial Mortgage Loans [Member]
Servicing Assets at Fair Value [Line Items]
Mortgage loans serviced for others	13,600	11,800	13,600	11,800	$ 11,000
Estimated fair value of capitalized mortgage loan servicing assets	$ 132	$ 119	$ 132	$ 119
Weighted average discount rates used to estimate fair value of capitalized mortgaged loan servicing assets	18.00%	18.00%	18.00%
Commercial Mortgage Sub Servicing Loan [Member]
Servicing Assets at Fair Value [Line Items]
Mortgage loans serviced for others	$ 2,600		$ 2,600

Capitalized Servicing Assets 86

Capitalized Servicing Assets - Economic Assumptions Used to Determine Fair Value of Capitalized Servicing Rights and Sensitivity of Value to Changes in Assumptions (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017
Residential Mortgage Loans [Member]
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Weighted-average prepayment speeds			12.16%
Impact on fair value of 10% adverse change	$ (8,935,000)		$ (8,935,000)
Impact on fair value of 20% adverse change	$ (17,159,000)		$ (17,159,000)
Weighted-average OAS	10.67%		10.67%
Impact on fair value of 10% adverse change	$ (6,838,000)		$ (6,838,000)
Impact on fair value of 20% adverse change	$ (13,267,000)		$ (13,267,000)
Weighted-average discount rate	12.20%	12.20%
Commercial Mortgage Loans [Member]
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Weighted-average discount rate	18.00%	18.00%	18.00%
Impact on fair value of 10% adverse change	$ (5,885,000)		$ (5,885,000)
Impact on fair value of 20% adverse change	$ (11,342,000)		$ (11,342,000)

Goodwill and Other Intangible87

Goodwill and Other Intangible Assets - Total Amortizing Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,070,027	$ 1,064,727
Accumulated Amortization	998,438	967,072
Net Carrying Amount	71,589	97,655
Core Deposit [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	887,459	887,459
Accumulated Amortization	820,110	789,988
Net Carrying Amount	67,349	97,471
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	182,568	177,268
Accumulated Amortization	178,328	177,084
Net Carrying Amount	$ 4,240	$ 184

Goodwill and Other Intangible88

Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill And Other Intangible Assets [Line Items]
Amortization of core deposit and other intangible assets	$ 31,366,000	$ 42,613,000	$ 26,424,000
Minimum [Member]
Goodwill And Other Intangible Assets [Line Items]
Estimated useful lives	5 years
Maximum [Member]
Goodwill And Other Intangible Assets [Line Items]
Estimated useful lives	10 years
Core Deposit and Other Intangible Assets [Member]
Goodwill And Other Intangible Assets [Line Items]
Estimated useful lives	8 years
Amortization of core deposit and other intangible assets	$ 31,366,000	$ 42,613,000	$ 26,424,000
Core Deposit and Other Intangible Assets [Member] \| Minimum [Member]
Goodwill And Other Intangible Assets [Line Items]
Estimated useful lives	5 years
Core Deposit and Other Intangible Assets [Member] \| Maximum [Member]
Goodwill And Other Intangible Assets [Line Items]
Estimated useful lives	10 years

Goodwill and Other Intangible89

Goodwill and Other Intangible Assets - Estimated Amortization Expense in Future Years (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
2,018	$ 24,522
2,019	19,086
2,020	14,383
2,021	9,681
2,022	3,917
Net Carrying Amount	$ 71,589	$ 97,655

Goodwill and Other Intangible90

Goodwill and Other Intangible Assets - Summary of Goodwill Assigned to Reportable Segments for Purposes of Testing for Impairment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill	$ 4,593,112	$ 4,593,112
Business Banking [Member]
Goodwill [Line Items]
Goodwill	864,366
Commercial Banking [Member]
Goodwill [Line Items]
Goodwill	1,401,873
Commercial Real Estate [Member]
Goodwill [Line Items]
Goodwill	654,389
Retail Banking [Member]
Goodwill [Line Items]
Goodwill	1,309,191
All Other [Member]
Goodwill [Line Items]
Goodwill	$ 363,293

Borrowings - Amounts and Intere

Borrowings - Amounts and Interest Rates of Short-term Borrowings (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Borrowings [Line Items]
Weighted-average interest rate	0.92%	0.32%	0.40%
Daily-average amount outstanding	$ 204,623,000	$ 893,822,000	$ 548,005,000
Weighted-average interest rate	0.74%	0.41%	0.31%
Federal funds purchased and short term borrowings	$ 175,099,000	$ 163,442,000	$ 2,132,182,000
Federal Funds Purchased and Repurchase Agreements [Member]
Schedule Of Borrowings [Line Items]
Weighted-average interest rate	0.92%	0.32%	0.06%
Highest amount at a month-end	$ 204,977,000	$ 225,940,000	$ 202,951,000
Daily-average amount outstanding	$ 188,459,000	$ 203,853,000	$ 187,167,000
Weighted-average interest rate	0.69%	0.28%	0.08%
Federal Funds Purchased and Repurchase Agreements	$ 175,099,000	$ 163,442,000	$ 150,546,000
Other Short-term Borrowings [Member]
Schedule Of Borrowings [Line Items]
Weighted-average interest rate			0.43%
Highest amount at a month-end	1,500,000,000	1,974,013,000	$ 1,989,257,000
Daily-average amount outstanding	$ 16,164,000	$ 689,969,000	$ 360,838,000
Weighted-average interest rate	1.27%	0.44%	0.43%
Other Short-term Borrowings			$ 1,981,636,000

Borrowings - Lines of Credit Un

Borrowings - Lines of Credit Under Formal Agreements (Detail) - M&T Bank [Member] $ in Thousands	Dec. 31, 2017USD ($)
Schedule Of Borrowings [Line Items]
Outstanding borrowings	$ 576,954
Unused	$ 31,624,206

Borrowings - Additional Informa

Borrowings - Additional Information (Detail) - USD ($)	12 Months Ended
Borrowings - Additional Information (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Minimum contractual interest rates of long-term agreements to repurchase securities	4.09%	3.65%
Maximum contractual interest rates of long-term agreements to repurchase securities	4.58%	4.58%
Weighted-average contractual interest rates of long term agreements to repurchase securities	4.31%	4.05%
Repurchase dates of the long-term agreements outstanding	2,020
Collateral posted	$ 442,000,000,000	$ 1,100,000,000
Debt Maturity, Start Year	Jan. 1, 2027
Debt Maturity, End Year	Dec. 31, 2033
Minimum [Member]
Debt Instrument [Line Items]
Variable interest rate of Senior Notes /Junior Subordinated Debentures	2.23%	1.74%
Maximum [Member]
Debt Instrument [Line Items]
Variable interest rate of Senior Notes /Junior Subordinated Debentures	4.71%	4.23%
FHLBs Facility [Member]
Debt Instrument [Line Items]
Borrowing facilities available with FHLB's amount	$ 20,200,000,000
Federal Reserve Bank of New York [Member]
Debt Instrument [Line Items]
Line of credit facility	$ 12,000,000,000
Variable Rate Senior Notes [Member]
Debt Instrument [Line Items]
Weighted-average variable rates payable		1.22%
Variable Rate Senior Notes [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Variable interest rate of Senior Notes /Junior Subordinated Debentures	2.05%	1.18%
Variable Rate Senior Notes [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Variable interest rate of Senior Notes /Junior Subordinated Debentures	2.05%	1.26%
Long-term Fixed Rate Advances From FHLB [Member]
Debt Instrument [Line Items]
Advances from the FHLB maturity date	2,035
Long-term Fixed Rate Advances From FHLB [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Variable contractual interest rate of long-term debt	1.97%	1.17%
Long-term Fixed Rate Advances From FHLB [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Variable contractual interest rate of long-term debt	5.98%	7.32%
Long-term Fixed Rate Advances From FHLB [Member] \| Weighted Average [Member]
Debt Instrument [Line Items]
Variable contractual interest rate of long-term debt	2.06%	1.65%
Subordinated Capital Notes [Member]
Debt Instrument [Line Items]
Interest rate of debt instrument	2.78%	1.97%
Subordinated Variable Rate Notes Due 2021 [Member]
Debt Instrument [Line Items]
Interest rate of debt instrument	2.12%	1.57%
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Weighted-average variable rates payable	2.83%	2.33%

Borrowings - Long-term Borrowin

Borrowings - Long-term Borrowings (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Borrowings [Line Items]
Fixed rates advances from FHLB	$ 576,876	$ 1,154,737
Agreements to repurchase securities	421,771	1,084,694
Other	9,635	12,010
Long-term borrowings	8,141,430	9,493,835
Variable Rate Term Loans Due 2017 [Member]
Schedule Of Borrowings [Line Items]
Variable\fixed rates term loan amount		550,000
Variable Rate Term Loans Due 2022 [Member]
Schedule Of Borrowings [Line Items]
Variable\fixed rates term loan amount	249,558
Fixed Rate Term Loans 1.25% Due 2017 [Member]
Schedule Of Borrowings [Line Items]
Variable\fixed rates term loan amount		499,999
Fixed Rate Term Loans 1.40% Due 2017 [Member]
Schedule Of Borrowings [Line Items]
Variable\fixed rates term loan amount		749,946
Fixed Rate Term Loans 1.45% Due 2018 [Member]
Schedule Of Borrowings [Line Items]
Variable\fixed rates term loan amount	499,907	501,829
Fixed Rate Term Loans 2.25% Due 2019 [Member]
Schedule Of Borrowings [Line Items]
Variable\fixed rates term loan amount	644,977	649,012
Fixed Rate Term Loans 2.30% Due 2019 [Member]
Schedule Of Borrowings [Line Items]
Variable\fixed rates term loan amount	746,919	749,473
Fixed Rate Term Loans 2.10% Due 2020 [Member]
Schedule Of Borrowings [Line Items]
Variable\fixed rates term loan amount	743,788	749,735
Fixed Rate Term Loans 2.05% Due 2020 [Member]
Schedule Of Borrowings [Line Items]
Variable\fixed rates term loan amount	739,961
Fixed Rate Term Loans 2.50% Due 2022 [Member]
Schedule Of Borrowings [Line Items]
Variable\fixed rates term loan amount	638,872
Fixed Rate Term Loans 2.90% Due 2025 [Member]
Schedule Of Borrowings [Line Items]
Variable\fixed rates term loan amount	749,404	749,320
8.5% due 2018 [Member]
Schedule Of Borrowings [Line Items]
Subordinated notes	200,000	207,651
6.625% due 2017 [Member]
Schedule Of Borrowings [Line Items]
Subordinated notes		409,526
5.585% due 2020, Variable Rate Commenced 2015 [Member]
Schedule Of Borrowings [Line Items]
Subordinated notes	409,361	409,361
5.629% due 2021, Variable Rate Commenced 2016 [Member]
Schedule Of Borrowings [Line Items]
Subordinated notes	500,000	500,000
3.40% due 2027 [Member]
Schedule Of Borrowings [Line Items]
Subordinated notes	491,176
BSB Capital Trust I - 8.125%, due 2028 [Member]
Schedule Of Borrowings [Line Items]
Junior subordinated debentures associated with preferred capital securities	15,682	15,659
Provident Trust I - 8.29%, due 2028 [Member]
Schedule Of Borrowings [Line Items]
Junior subordinated debentures associated with preferred capital securities	26,847	26,293
Southern Financial Statutory Trust I - 10.60%, due 2030 [Member]
Schedule Of Borrowings [Line Items]
Junior subordinated debentures associated with preferred capital securities	6,664	6,620
First Maryland Capital I - due 2027 [Member]
Schedule Of Borrowings [Line Items]
Junior subordinated debentures associated with preferred capital securities	146,794	146,256
First Maryland Capital II - due 2027 [Member]
Schedule Of Borrowings [Line Items]
Junior subordinated debentures associated with preferred capital securities	148,617	147,954
Allfirst Asset Trust - due 2029 [Member]
Schedule Of Borrowings [Line Items]
Junior subordinated debentures associated with preferred capital securities	96,640	96,494
BSB Capital Trust III - due 2033 [Member]
Schedule Of Borrowings [Line Items]
Junior subordinated debentures associated with preferred capital securities	15,464	15,464
Provident Statutory Trust III - Due 2033 [Member]
Schedule Of Borrowings [Line Items]
Junior subordinated debentures associated with preferred capital securities	54,466	53,834
Southern Financial Capital Trust III - due 2033 [Member]
Schedule Of Borrowings [Line Items]
Junior subordinated debentures associated with preferred capital securities	$ 8,051	$ 7,968

Borrowings - Long-term Borrow95

Borrowings - Long-term Borrowings (Parenthetical) (Detail)	12 Months Ended
Borrowings - Long-term Borrowings (Parenthetical) (Detail)	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Borrowings [Line Items]
Debt Maturity, Start Date	Jan. 1, 2027
Debt Maturity, End Date	Dec. 31, 2033
Variable Rate Due 2016 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,017	2,017
Senior Notes Due 2017 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,022	2,022
Fixed Rate Term Loans 1.25% Due 2017 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,017	2,017
Interest rate of debt instrument	1.25%	1.25%
Fixed Rate Term Loans 1.40% Due 2017 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,017	2,017
Interest rate of debt instrument	1.40%	1.40%
Fixed Rate Term Loans 1.45% Due 2018 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,018	2,018
Interest rate of debt instrument	1.45%	1.45%
Fixed Rate Term Loans 2.25% Due 2019 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,019	2,019
Interest rate of debt instrument	2.25%	2.25%
Fixed Rate Term Loans 2.30% Due 2019 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,019	2,019
Interest rate of debt instrument	2.30%	2.30%
Fixed Rate Term Loans 2.10% Due 2020 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,020	2,020
Interest rate of debt instrument	2.10%	2.10%
Fixed Rate Term Loans 2.05% Due 2020 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,020	2,020
Interest rate of debt instrument	2.05%	2.05%
Fixed Rate Term Loans 2.90% Due 2025 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,025	2,025
Interest rate of debt instrument	2.90%	2.90%
Fixed Rate Term Loans 2.50% Due 2022 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,022	2,022
Interest rate of debt instrument	2.50%	2.50%
8.5% due 2018 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,018	2,018
Interest rate of debt instrument	8.50%	8.50%
6.625% due 2017 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,017	2,017
Interest rate of debt instrument	6.625%	6.625%
5.585% due 2020, Variable Rate Commenced 2015 [Member]
Schedule Of Borrowings [Line Items]
Interest rate of debt instrument	5.585%	5.585%
Debt Maturity, Start Date	Jan. 1, 2015	Jan. 1, 2015
Debt Maturity, End Date	Dec. 31, 2020	Dec. 31, 2020
5.629% due 2021, Variable Rate Commenced 2016 [Member]
Schedule Of Borrowings [Line Items]
Interest rate of debt instrument	5.629%	5.629%
Debt Maturity, Start Date	Jan. 1, 2016	Jan. 1, 2016
Debt Maturity, End Date	Dec. 31, 2021	Dec. 31, 2021
3.40% due 2027 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,027	2,027
Interest rate of debt instrument	3.40%	3.40%
BSB Capital Trust I - 8.125%, due 2028 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,028	2,028
Interest rate of debt instrument	8.125%	8.125%
Provident Trust I - 8.29%, due 2028 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,028	2,028
Interest rate of debt instrument	8.29%	8.29%
Southern Financial Statutory Trust I - 10.60%, due 2030 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,030	2,030
Interest rate of debt instrument	10.60%	10.60%
First Maryland Capital I - due 2027 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,027	2,027
First Maryland Capital II - due 2027 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,027	2,027
Allfirst Asset Trust - due 2029 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,029	2,029
BSB Capital Trust III - due 2033 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,033	2,033
Provident Statutory Trust III - Due 2033 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,033	2,033
Southern Financial Capital Trust III - due 2033 [Member]
Schedule Of Borrowings [Line Items]
Debt maturity date	2,033	2,033

Borrowings - Maturity of Long-t

Borrowings - Maturity of Long-term Borrowings (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
2,018	$ 701,256
2,019	2,282,016
2,020	2,005,383
2,021	502,487
2,022	888,430
Later years	1,761,858
Long-term borrowings	$ 8,141,430	$ 9,493,835

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, par value	$ 1	$ 1
Warrant [Member] \| Assumed In Acquisition [Member]
Class of Stock [Line Items]
Exercise price of each class of warrants or rights outstanding	$ 518.32
Warrant to purchase common stock	95,500
Warrants, date of expiration	Dec. 12, 2018

Shareholders' Equity - Issued a

Shareholders' Equity - Issued and Outstanding Preferred Stock (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Carrying Value	$ 1,231,500	$ 1,231,500
Series A Fixed Rate Cumulative Perpetual Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, Shares Issued	230,000	230,000
Preferred stock, Shares Outstanding	230,000	230,000
Carrying Value	$ 230,000	$ 230,000
Series C Fixed Rate Cumulative Perpetual Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, Shares Issued	151,500	151,500
Preferred stock, Shares Outstanding	151,500	151,500
Carrying Value	$ 151,500	$ 151,500
Series E Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, Shares Issued	350,000	350,000
Preferred stock, Shares Outstanding	350,000	350,000
Carrying Value	$ 350,000	$ 350,000
Series F Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, Shares Issued	50,000	500,000
Preferred stock, Shares Outstanding	50,000	500,000
Carrying Value	$ 500,000	$ 500,000

Shareholders' Equity - Issued99

Shareholders' Equity - Issued and Outstanding Preferred Stock (Parenthetical) (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Series A Fixed Rate Cumulative Perpetual Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, liquidation preference per share	$ 1,000	$ 1,000
Preferred stock dividend rate	6.375%
Exercise price of each class of warrants or rights outstanding	$ 73.77
Warrants and rights outstanding	257,008
Warrants, date of expiration	Dec. 23, 2018
Series C Fixed Rate Cumulative Perpetual Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, liquidation preference per share	$ 1,000	1,000
Preferred stock dividend rate	6.375%
Series E Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, liquidation preference per share	$ 1,000	$ 1,000
Preferred stock dividend rate	6.45%	6.45%
Date of change in the dividend rate	Feb. 14, 2024	Feb. 14, 2024
London Interbank offered rate plus basis points	3.61%	3.61%
Preferred shares redemption date	Feb. 15, 2024	Feb. 15, 2024
Preferred Stock, Redemption Feature, Redemption Term	90 days	90 days
Series F Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, liquidation preference per share	$ 10,000	$ 10,000
Preferred stock dividend rate	5.125%	5.125%
Date of change in the dividend rate	Oct. 31, 2026	Oct. 31, 2026
London Interbank offered rate plus basis points	3.52%	3.52%
Preferred shares redemption date	Nov. 1, 2026	Nov. 1, 2026
Preferred Stock, Redemption Feature, Redemption Term	90 days	90 days

Stock-Based Compensation Pla100

Stock-Based Compensation Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 61,000,000	$ 65,000,000	$ 67,000,000
Recognized income tax benefits related to stock-based compensation	$ 35,000,000	$ 31,000,000	$ 29,000,000
Shares under equity incentive compensation plan for future grant	3,278,036	3,667,800
Directors Stock Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issuable under deferred compensation plans	7,505	9,215
Shares issued in connection with deferred compensation plans	255,816
Deferred Bonus Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issuable under deferred compensation plans	19,633	23,188
Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued	66,504	97,880	89,384
Common stock authorized for issuance	2,500,000
Cash received from exercise of stock options	$ 9,730,000	$ 9,528,000	$ 9,296,000
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years	3 years	3 years	4 years
Unrecognized compensation cost expected to be recognized over a weighted-average period (in years)	1 year	1 year
Unrecognized compensation cost related to non-vested awards	$ 15,000,000
Shares issued	181,939	218,341	218,183
Restricted Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value	$ 29,557,000	$ 24,085,000	$ 24,726,000
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost related to non-vested awards	$ 6,000,000
Shares issued	235,983	348,297	324,772
Weighted-average grant date fair value	$ 38,364,000	$ 38,795,000	$ 37,070,000
Stock Option Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	4 years
Stock options exercisable period, maximum	10 years 1 day
Cash realized from exercise of stock options	$ 72,000,000	172,000,000	93,000,000
Tax benefits realized from exercise of stock options	10,000,000	15,000,000	6,000,000
Intrinsic value of stock options exercised	$ 31,000,000	$ 42,000,000	$ 17,000,000

Stock-Based Compensation Pla101

Stock-Based Compensation Plans - Summary of Restricted Stock and Restricted Stock Unit Activity (Detail)	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted Stock Outstanding, Unvested, Beginning balance \| shares	739,350
Restricted Stock Outstanding, Granted \| shares	235,983
Restricted Stock Outstanding, Vested \| shares	(481,002)
Restricted Stock Outstanding, Cancelled \| shares	(11,774)
Restricted Stock Outstanding, Unvested, Ending balance \| shares	482,557
Weighted-Average Grant Price, Unvested, Beginning balance \| $ / shares	$ 111.21
Weighted-Average Grant Price, Granted \| $ / shares	162.57
Weighted-Average Grant Price, Vested \| $ / shares	114.06
Weighted-Average Grant Price, Cancelled \| $ / shares	129.15
Weighted-Average Grant Price, Unvested, Ending balance \| $ / shares	$ 133.05
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted Stock Outstanding, Unvested, Beginning balance \| shares	499,324
Restricted Stock Outstanding, Granted \| shares	181,939
Restricted Stock Outstanding, Vested \| shares	(290,935)
Restricted Stock Outstanding, Cancelled \| shares	(16,584)
Restricted Stock Outstanding, Unvested, Ending balance \| shares	373,744
Weighted-Average Grant Price, Unvested, Beginning balance \| $ / shares	$ 109.92
Weighted-Average Grant Price, Granted \| $ / shares	162.46
Weighted-Average Grant Price, Vested \| $ / shares	108.97
Weighted-Average Grant Price, Cancelled \| $ / shares	128.64
Weighted-Average Grant Price, Unvested, Ending balance \| $ / shares	$ 135.41

Stock-Based Compensation Pla102

Stock-Based Compensation Plans - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Options Outstanding, Beginning balance \| shares	1,594,591
Stock Options Outstanding, Granted \| shares	200
Stock Options Outstanding, Exercised \| shares	(658,400)
Stock Options Outstanding, Expired \| shares	(270,979)
Stock Options Outstanding, Ending balance \| shares	665,412
Stock Options Outstanding, Exercisable \| shares	665,010
Weighted-Average Exercise Price, Outstanding, Beginning balance \| $ / shares	$ 139.60
Weighted-Average Exercise Price, Granted \| $ / shares	162.57
Weighted-Average Exercise Price, Exercised \| $ / shares	116.20
Weighted-Average Exercise Price, Expired \| $ / shares	165.46
Weighted-Average Exercise Price, Outstanding, Ending balance \| $ / shares	152.23
Weighted-Average Exercise Price, Exercisable \| $ / shares	$ 152.23
Weighted-Average Life (In Years), Outstanding, Ending balance	9 months 18 days
Weighted-Average Life (In Years), Exercisable	9 months 18 days
Aggregate Intrinsic Value, Outstanding, Ending balance \| $	$ 18,086
Aggregate Intrinsic Value, Exercisable \| $	$ 18,072

Pension Plans and Other Post103

Pension Plans and Other Postretirement Benefits - Net Periodic Benefit Cost for Defined Benefit Plans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 20,193	$ 25,037	$ 24,372
Interest cost on benefit obligation	79,270	83,410	72,731
Expected return on plan assets	(108,524)	(108,473)	(96,155)
Amortization of prior service cost (credit)	557	(3,228)	(6,005)
Recognized net actuarial loss	29,263	30,145	44,825
Net periodic benefit costs	20,759	26,891	39,768
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,172	1,595	914
Interest cost on benefit obligation	3,716	4,971	2,995
Amortization of prior service cost (credit)	(1,359)	(1,359)	(1,359)
Recognized net actuarial loss	(988)	60	106
Net periodic benefit costs	$ 2,541	$ 5,267	$ 2,656

Pension Plans and Other Post104

Pension Plans and Other Postretirement Benefits - Data Relating to Funding Position of Defined Benefit Plans (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in plan assets:
Fair value of plan assets at beginning of year	$ 1,640,300,000
Fair value of plan assets at end of year	2,013,117,000	$ 1,640,300,000
Pension Benefits [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	2,007,158,000	2,004,531,000
Service cost	20,193,000	25,037,000	$ 24,372,000
Interest cost	79,270,000	83,410,000	72,731,000
Amendments and curtailments		(28,308,000)
Actuarial (gain) loss	172,180,000	4,827,000
Benefits paid	(90,065,000)	(82,339,000)
Benefit obligation at end of year	2,188,736,000	2,007,158,000	2,004,531,000
Change in plan assets:
Fair value of plan assets at beginning of year	1,642,131,000	1,625,134,000
Actual return on plan assets	251,381,000	88,564,000
Employer contributions	211,444,000	10,772,000
Benefits paid	(90,065,000)	(82,339,000)
Fair value of plan assets at end of year	2,014,891,000	1,642,131,000	1,625,134,000
Funded status	(173,845,000)	(365,027,000)
Accrued liabilities recognized in the consolidated balance sheet	(173,845,000)	(365,027,000)
Net loss (gain)	460,622,000	460,562,000
Net prior service cost (credit)	2,948,000	3,505,000
Pre-tax adjustment to AOCI	463,570,000	464,067,000
Taxes	(121,873,000)	(182,611,000)
Net adjustment to AOCI	341,697,000	281,456,000
Other Postretirement Benefits [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	109,922,000	121,497,000
Service cost	1,172,000	1,595,000	914,000
Interest cost	3,716,000	4,971,000	2,995,000
Plan participants’ contributions	2,929,000	3,085,000
Amendments and curtailments	(30,088,000)
Actuarial (gain) loss	(8,511,000)	(10,553,000)
Medicare Part D reimbursement	630,000	592,000
Benefits paid	(11,133,000)	(11,265,000)
Benefit obligation at end of year	68,637,000	109,922,000	$ 121,497,000
Change in plan assets:
Employer contributions	7,574,000	7,588,000
Plan participants’ contributions	2,929,000	3,085,000
Medicare Part D reimbursement	630,000	592,000
Benefits paid	(11,133,000)	(11,265,000)
Funded status	(68,637,000)	(109,922,000)
Accrued liabilities recognized in the consolidated balance sheet	(68,637,000)	(109,922,000)
Net loss (gain)	(13,936,000)	(6,413,000)
Net prior service cost (credit)	(36,466,000)	(7,737,000)
Pre-tax adjustment to AOCI	(50,402,000)	(14,150,000)
Taxes	13,251,000	5,568,000
Net adjustment to AOCI	$ (37,151,000)	$ (8,582,000)

Pension Plans and Other Post105

Pension Plans and Other Postretirement Benefits - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Minimum pension liability	$ 413,168,000
Minimum pension liability adjustment net of tax		$ 304,546,000
Decrease in minimum liability adjustment		36,749,000
Defined contribution pension and retirement savings plans total expense	$ 30,000,000	25,000,000	$ 23,000,000
Assumptions used calculating net periodic benefit sensitivity rate increase decrease discount rate	0.25%
Effect of 25 basis point increase in rate of return on pension expense	$ 4,000,000
Effect of 25 basis point decrease in rate of return on pension expense	7,000,000
Effect of 25 basis point decrease in discount rate on benefit obligation	76,000,000
Effect of 25 basis point increase in discount rate on benefit obligation	$ 80,000,000
Annual rate of increase in health care cost assumed for next fiscal year	6.50%
Defined Benefit Plan, ultimate health care cost trend rate	5.00%
Period for decreasing the annual rate	over 11 years
Defined benefit pension plans	$ 304,463,000
Percentage of total assets	15.00%
Defined benefit plan fair value of plan assets	$ 2,013,117,000	1,640,300,000
Qualified benefit pension plans		0	0
Percentage of pension plan assets that is not exceeded by investment in security of single Non-US Government of Government agency	10.00%
Percentage of eligible employees contribution for Retirement Savings Plan	50.00%
Percentage of employer matching contribution to employee's contribution	75.00%
Maximum employer contribution on Employee's qualified contribution	4.50%
Qualified defined contribution plans expense during the period	$ 38,229,000	36,766,000	34,145,000
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	$ 1,019,639,000	920,077,000
Equity Securities [Member] \| Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for plan assets	25.00%
Equity Securities [Member] \| Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for plan assets	60.00%
Total Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	$ 571,367,000	445,698,000
Total Debt Securities [Member] \| Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for plan assets	10.00%
Total Debt Securities [Member] \| Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for plan assets	65.00%
Other Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	$ 304,463,000	234,969,000
Other Securities [Member] \| Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for plan assets	10.00%
Other Securities [Member] \| Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocations for plan assets	85.00%
M&T Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	$ 154,818,000	$ 164,474,000
Percentage of common stock in total plan assets	7.70%	10.00%
Supplemental Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 165,210,000	$ 160,433,000
Accumulated benefit obligation	165,210,000	160,433,000
Employer contributions	11,444,000	10,772,000
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	2,188,736,000	2,007,158,000	2,004,531,000
Accumulated benefit obligation	2,158,601,000	1,979,225,000
Minimum pension liability	463,570,000
Defined benefit plan fair value of plan assets	2,014,891,000	1,642,131,000	1,625,134,000
Employer contributions	211,444,000	10,772,000
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	68,637,000	109,922,000	$ 121,497,000
Minimum pension liability	50,402,000
Employer contributions	$ 7,574,000	$ 7,588,000

Pension Plans and Other Post106

Pension Plans and Other Postretirement Benefits - Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net loss (gain)	$ 20,812	$ 14,183
Amendments and curtailments	(30,088)	(28,308)
Amortization of prior service (cost) credit	802	4,587	$ 7,364
Amortization of actuarial (loss) gain	(28,275)	(30,205)	$ (44,931)
Total recognized in other comprehensive income, pre-tax	(36,749)	(39,743)
Pension Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net loss (gain)	29,323	24,736
Amendments and curtailments		(28,308)
Amortization of prior service (cost) credit	(557)	3,228
Amortization of actuarial (loss) gain	(29,263)	(30,145)
Total recognized in other comprehensive income, pre-tax	(497)	(30,489)
Other Postretirement Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net loss (gain)	(8,511)	(10,553)
Amendments and curtailments	(30,088)
Amortization of prior service (cost) credit	1,359	1,359
Amortization of actuarial (loss) gain	988	(60)
Total recognized in other comprehensive income, pre-tax	$ (36,252)	$ (9,254)

Pension Plans and other Post107

Pension Plans and other Postretirement Benefits - Amortization of Amounts in Accumulated Other Comprehensive Income Expected to be Recognized as Components of Net Periodic Benefit Expense (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Pension Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Amortization of net prior service cost (credit)	$ 557
Amortization of net loss (gain)	44,416
Other Postretirement Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Amortization of net prior service cost (credit)	(4,729)
Amortization of net loss (gain)	$ (830)

Pension Plans and Other Post108

Pension Plans and Other Postretirement Benefits - Assumed Weighted-Average Rates Used to Determine Benefit Obligations (Detail)	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Discount rate	3.50%	4.00%
Rate of increase in future compensation levels	4.33%	4.39%
Other Postretirement Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Discount rate	3.50%	4.00%

Pension Plans and Other Post109

Pension Plans and Other Postretirement Benefits - Assumed Weighted-Average Rates Used to Determine Net Benefit Expense (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Discount rate	4.00%	4.25%	4.00%
Long-term rate of return on plan assets	6.50%	6.50%	6.50%
Rate of increase in future compensation levels	4.39%	4.37%	4.39%
Other Postretirement Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Discount rate	4.00%	4.25%	4.00%

Pension Plans and Other Post110

Pension Plans and Other Postretirement Benefits - Effects on One-Percentage Point Change in Assumed Health Care Cost Trend Rates (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Compensation And Retirement Disclosure [Abstract]
Service and interest cost	$ 63
Accumulated postretirement benefit obligation	1,454
Service and interest cost	(57)
Accumulated postretirement benefit obligation	$ (1,316)

Pension Plans and Other Post111

Pension Plans and Other Postretirement Benefits - Fair Values of Company's Pension Plan Assets by Asset Category (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	$ 2,013,117,000	$ 1,640,300,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	1,532,836,000	1,340,215,000
Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	382,853,000	243,845,000
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	97,428,000	56,240,000
Money-Market Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	117,648,000	39,556,000
Money-Market Investments [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	62,706,000	35,562,000
Money-Market Investments [Member] \| Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	54,942,000	3,994,000
M&T Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	154,818,000	164,474,000
M&T Equity Securities [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	154,818,000	164,474,000
Domestic Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	240,763,000	200,595,000
Domestic Equity Securities [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	240,763,000	200,595,000
International Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	13,349,000	14,364,000
International Equity Securities [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	13,349,000	14,364,000
Domestic Mutual Fund Equity securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	205,509,000	250,472,000
Domestic Mutual Fund Equity securities [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	205,509,000	250,472,000
International Mutual Fund Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	405,200,000	290,172,000
International Mutual Fund Equity Securities [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	405,200,000	290,172,000
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	1,019,639,000	920,077,000
Equity Securities [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	1,019,639,000	920,077,000
Corporate Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	89,751,000	104,909,000
Corporate Debt Securities [Member] \| Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	89,751,000	104,909,000
Government Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	235,984,000	121,869,000
Government Debt Securities [Member] \| Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	235,984,000	121,869,000
International Debt securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	2,176,000	13,073,000
International Debt securities [Member] \| Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	2,176,000	13,073,000
Domestic Mutual Fund Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	243,456,000	205,847,000
Domestic Mutual Fund Debt Securities [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	243,456,000	205,847,000
Total Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	571,367,000	445,698,000
Total Debt Securities [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	243,456,000	205,847,000
Total Debt Securities [Member] \| Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	327,911,000	239,851,000
Other Diversified Mutual Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	80,227,000	92,691,000
Other Diversified Mutual Fund [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	80,227,000	92,691,000
Other Real Estate Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	3,747,000	3,112,000
Other Real Estate Partnerships [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	842,000	768,000
Other Real Estate Partnerships [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	2,905,000	2,344,000
Other Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	31,484,000	21,924,000
Other Private Equity [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	31,484,000	21,924,000
Other Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	178,080,000	106,250,000
Other Hedge Funds [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	125,966,000	85,270,000
Other Hedge Funds [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	52,114,000	20,980,000
Guaranteed Deposit Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	10,925,000	10,992,000
Guaranteed Deposit Fund [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	10,925,000	10,992,000
Other Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	304,463,000	234,969,000
Other Securities [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	207,035,000	178,729,000
Other Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets	$ 97,428,000	$ 56,240,000

Pension Plans and Other Post112

Pension Plans and Other Postretirement Benefits - Fair Values of Company's Pension Plan Assets by Asset Category (Parenthetical) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Interest and dividend receivable on plan assets	$ 1,774,000	$ 1,831,000
Investment Grade Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Investment in mutual funds	77.00%	75.00%
High-Yielding Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Investment in mutual funds	23.00%	25.00%

Pension Plans and Other Post113

Pension Plans and Other Postretirement Benefits - Changes in Level 3 Pension Plan Assets Measured at Fair Value on Recurring Basis (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of plan assets at beginning of year	$ 1,640,300
Fair value of plan assets at end of year	2,013,117
Significant Unobservable Inputs (Level 3) [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of plan assets at beginning of year	56,240
Fair value of plan assets at end of year	97,428
Other Real Estate Partnerships [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of plan assets at beginning of year	3,112
Fair value of plan assets at end of year	3,747
Other Real Estate Partnerships [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of plan assets at beginning of year	2,344
Purchase(Sales)	365
Total Realized/Unrealized Gains (Losses)	196
Fair value of plan assets at end of year	2,905
Other Private Equity [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of plan assets at beginning of year	21,924
Fair value of plan assets at end of year	31,484
Other Private Equity [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of plan assets at beginning of year	21,924
Purchase(Sales)	6,821
Total Realized/Unrealized Gains (Losses)	2,739
Fair value of plan assets at end of year	31,484
Other Hedge Funds [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of plan assets at beginning of year	106,250
Fair value of plan assets at end of year	178,080
Other Hedge Funds [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of plan assets at beginning of year	20,980
Purchase(Sales)	29,839
Total Realized/Unrealized Gains (Losses)	1,295
Fair value of plan assets at end of year	52,114
Guaranteed Deposit Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of plan assets at beginning of year	10,992
Fair value of plan assets at end of year	10,925
Guaranteed Deposit Fund [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of plan assets at beginning of year	10,992
Total Realized/Unrealized Gains (Losses)	(67)
Fair value of plan assets at end of year	10,925
Other Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of plan assets at beginning of year	234,969
Fair value of plan assets at end of year	304,463
Other Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of plan assets at beginning of year	56,240
Purchase(Sales)	37,025
Total Realized/Unrealized Gains (Losses)	4,163
Fair value of plan assets at end of year	$ 97,428

Pension Plans and Other Post114

Pension Plans and Other Postretirement Benefits - Defined Benefit Plan Estimated Future Benefit Payments (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Pension Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
2,018	$ 88,407
2,019	94,317
2,020	98,753
2,021	103,968
2,022	107,298
2023 through 2027	594,900
Other Postretirement Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
2,018	7,318
2,019	7,207
2,020	7,055
2,021	4,402
2,022	4,302
2023 through 2027	$ 19,830

Income Taxes - Components of In

Income Taxes - Components of Income Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
Federal	$ 363,043	$ 428,750	$ 130,349
State and local	94,714	95,426	21,549
Total current	457,757	524,176	151,898
Deferred
Federal	367,308	147,662	324,317
State and local	33,482	26,351	72,279
Total deferred	400,790	174,013	396,596
Amortization of investments in qualified affordable housing projects	57,009	45,095	46,531
Income taxes	$ 915,556	$ 743,284	$ 595,025

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	3 Months Ended	12 Months Ended
Income Taxes - Additional Information (Detail)	Dec. 31, 2017USD ($)	Dec. 31, 2018	Dec. 31, 2017USD ($)State	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Income Tax Disclosure [Line Items]
Tax bad debt reserve	$ 137,121,000		$ 137,121,000
Income taxes attributable to gains or losses on bank investment securities			7,195,000	$ 11,925,000	$ 0
Alternative minimum tax expense recognized for gains or losses on bank investment securities			$ 0	$ 0	$ 0
Federal income tax rate			35.00%
Estimated incremental income tax expense related to Tax Act	$ 85,000,000
Number of state and local jurisdictions where company files income tax returns \| State			40
ASU 2016-09 [Member]
Income Tax Disclosure [Line Items]
New accounting pronouncement or change in accounting principle effect of adoption change in income tax expense (benefit)			$ (22,000,000)
Scenario Forecast [Member]
Income Tax Disclosure [Line Items]
Federal income tax rate		21.00%

Income Taxes - Schedule of Inco

Income Taxes - Schedule of Income Taxes Expenses Benefit Reconciliation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income taxes at statutory federal income tax rate	$ 813,352	$ 720,439	$ 586,142
Increase (decrease) in taxes:
Tax-exempt income	(40,778)	(35,364)	(33,102)
State and local income taxes, net of federal income tax effect	83,327	79,155	60,988
Qualified affordable housing project federal tax credits, net	(16,015)	(15,091)	(15,297)
Initial impact of enactment of Tax Act	85,431
Other	(9,761)	(5,855)	(3,706)
Income taxes	$ 915,556	$ 743,284	$ 595,025

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets (Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Losses on loans and other assets	$ 345,609	$ 590,288	$ 637,955
Retirement benefits	45,322	143,067	148,722
Postretirement and other employee benefits	26,009	52,512	55,962
Incentive and other compensation plans	25,050	36,616	60,337
Interest on loans	37,900	61,266	57,640
Stock-based compensation	26,676	52,181	72,090
Unrealized losses		10,741
Other	66,247	106,876	162,086
Gross deferred tax assets	572,813	1,053,547	1,194,792
Leasing transactions	(181,159)	(266,268)	(285,074)
Unrealized gains	(94,285)		(31,121)
Capitalized servicing rights	(51,781)	(71,108)	(59,171)
Depreciation and amortization	(52,733)	(63,959)	(56,731)
Other	(21,599)	(87,200)	(55,611)
Gross deferred tax liabilities	(401,557)	(488,535)	(487,708)
Net deferred tax asset	$ 171,256	$ 565,012	$ 707,084

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Federal, State and Local Tax [Member]
Reconciliation Of Unrecognized Tax Benefits [Line Items]
Beginning Balance	$ 35,889	$ 24,537	$ 10,712
Increases as a result of tax positions taken during the period	13,019	12,237	8,108
Decreases as a result of settlements with taxing authorities	(332)		(1,515)
Unrealized tax benefits acquired in a business combination			7,232
Decreases as a result of tax positions in prior years	(3,144)	(885)
Ending Balance	45,432	35,889	24,537
Accrued Interest [Member]
Reconciliation Of Unrecognized Tax Benefits [Line Items]
Beginning Balance	7,915	7,969	3,869
Increases as a result of tax positions taken in prior years	1,379	656	807
Decreases as a result of settlements with taxing authorities	(168)		(274)
Unrealized tax benefits acquired in a business combination			3,567
Decreases as a result of tax positions in prior years	(3,475)	(710)
Ending Balance	5,651	7,915	7,969
Unrecognized Income Tax Benefits [Member]
Reconciliation Of Unrecognized Tax Benefits [Line Items]
Beginning Balance	43,804	32,506	14,581
Increases as a result of tax positions taken during the period	13,019	12,237	8,108
Increases as a result of tax positions taken in prior years	1,379	656	807
Decreases as a result of settlements with taxing authorities	(500)		(1,789)
Unrealized tax benefits acquired in a business combination			10,799
Decreases as a result of tax positions in prior years	(6,619)	(1,595)
Ending Balance	51,083	$ 43,804	$ 32,506
Less: Federal, state and local income tax benefits	(10,727)
Net unrecognized tax benefits that, if recognized, would impact the effective income tax rate	$ 40,356

Earnings Per Common Share - Com

Earnings Per Common Share - Computations of Basic Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income available to common shareholders:
Net income	$ 1,408,306	$ 1,315,114	$ 1,079,667
Less: Preferred stock dividends	(72,734)	(81,270)	(81,270)
Net income available to common equity	1,335,572	1,233,844	998,397
Less: Income attributable to unvested stock-based compensation awards	(8,069)	(10,385)	(10,708)
Net income available to common shareholders	$ 1,327,503	$ 1,223,459	$ 987,689
Weighted-average shares outstanding:
Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards	153,092	158,121	138,285
Less: Unvested stock-based compensation awards	(933)	(1,341)	(1,482)
Weighted-average shares outstanding	152,159	156,780	136,803
Basic earnings per common share	$ 8.72	$ 7.80	$ 7.22

Earnings Per Common Share - 121

Earnings Per Common Share - Computations of Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income available to common equity	$ 1,335,572	$ 1,233,844	$ 998,397
Less: Income attributable to unvested stock-based compensation awards	(8,055)	(10,363)	(10,673)
Net income available to common shareholders	$ 1,327,517	$ 1,223,481	$ 987,724
Adjusted weighted-average shares outstanding:
Common and unvested stock-based compensation awards	153,092	158,121	138,285
Less: Unvested stock-based compensation awards	(933)	(1,341)	(1,482)
Plus: Incremental shares from assumed conversion of stock-based compensation awards and warrants to purchase common stock	392	524	730
Adjusted weighted-average shares outstanding	152,551	157,304	137,533
Diluted earnings per common share	$ 8.70	$ 7.78	$ 7.18

Earnings Per Common Share - Add

Earnings Per Common Share - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Antidilutive Securities excluded from computation of Earnings Per Share	401,000	2,171,000	2,268,000

Comprehensive Income -Additiona

Comprehensive Income -Additional Information (Detail)	12 Months Ended
Comprehensive Income -Additional Information (Detail)	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Federal income tax rate		35.00%
Scenario Forecast [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Federal income tax rate	21.00%

Comprehensive Income - Impact o

Comprehensive Income - Impact of Reclassification from AOCI to Retained Earnings (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Increase to retained earnings	$ 64,029
Net Unrealized Losses on Investment Securities [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Increase to retained earnings	8,065
Defined Benefit Plans Liability Adjustments [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Increase to retained earnings	53,960
Cash Flow Hedges and Other [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Increase to retained earnings	$ 2,004

Comprehensive Income - Componen

Comprehensive Income - Components of Other Comprehensive Income (Loss) and Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) to Net Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	$ (485,245)	$ (414,545)	$ (297,843)
Unrealized holding gains (losses), before tax	(15,005)	(79,950)	(133,702)
Foreign currency translation adjustment, before tax	4,447	(4,020)	(1,323)
Unrealized losses on cash flow hedges, before tax	(12,291)		1,453
Current year benefit plans gains (losses), before tax	9,276	14,125	(24,200)
Total other comprehensive income (loss) before reclassifications, before tax	(13,573)	(69,845)	(157,772)
Amortization of unrealized holding losses on held-to-maturity (“HTM”) securities, before tax	3,387	3,996	3,514
(Gains) losses realized in net income, before tax	(21,279)	(30,314)	130
Accretion of net gain (losses) on terminated cash flow hedges, before tax	(137)	(155)	(141)
Net yield adjustment from cash flow hedges currently in effect, before tax	(3,916)
Amortization of prior service credit, before tax	(802)	(4,587)	(7,364)
Amortization of actuarial losses, before tax	28,275	30,205	44,931
Total reclassifications, before tax	(8,045)	(855)	41,070
Total gain (loss) during the period, before tax		(70,700)	(116,702)
Ending balance, before tax	(493,290)	(485,245)	(414,545)
Beginning balance, tax	190,609	162,918	116,849
Unrealized holding gains (losses), tax	7,269	31,509	52,376
Foreign currency translation adjustment, tax	(2,206)	1,406	398
Unrealized losses on cash flow hedges, tax	4,837		(572)
Current year benefit plans gains (losses), tax	(3,650)	(5,557)	8,612
Total other comprehensive income (loss) before reclassifications, tax	6,250	27,358	60,814
Amortization of unrealized holding losses on held-to-maturity (“HTM”) securities, tax	(1,333)	(1,572)	(1,383)
Gains (losses) realized in net income, tax	7,195	11,925	(49)
Accretion of net gain (losses) on terminated cash flow hedges, tax	54	61	56
Net yield adjustment from cash flow hedges currently in effect, tax	1,541
Amortization of prior service credit, tax	315	1,805	2,620
Amortization of actuarial losses, tax	(11,126)	(11,886)	(15,989)
Total reclassifications, tax	2,896	333	(14,745)
Reclassification of income tax effects to retained earnings, tax	(64,029)
Total gain (loss) during the period, tax		27,691	46,069
Ending balance, tax	129,476	190,609	162,918
Beginning balance, net of tax	(294,636)	(251,627)	(180,994)
Unrealized holding gains (losses), net of tax	(7,736)	(48,441)	(81,326)
Foreign currency translation adjustment, net of tax	2,241	(2,614)	(925)
Unrealized losses on cash flow hedges, net of tax	(7,454)		881
Current year benefit plans gains (losses), net of tax	5,626	8,568	(15,588)
Total other comprehensive income (loss) before reclassifications, net of tax	(7,323)	(42,487)	(96,958)
Amortization of unrealized holding losses on held-to-maturity (“HTM”) securities, net of tax	2,054	2,424	2,131
(Gains) losses realized in net income, net of tax	(14,084)	(18,389)	81
Accretion of net gain on terminated cash flow hedges, net of tax	(83)	(94)	(85)
Net yield adjustment from cash flow hedges currently in effect, net of tax	(2,375)
Amortization of prior service credit, net of tax	(487)	(2,782)	(4,744)
Amortization of actuarial losses, net of tax	17,149	18,319	28,942
Total reclassifications, net of tax	(5,149)	(522)	26,325
Reclassification of income tax effects to retained earnings, net of tax	(64,029)
Total other comprehensive loss	(5,149)	(43,009)	(70,633)
Ending balance, net of tax	(363,814)	(294,636)	(251,627)
Investment Securities With OTTI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	46,725	16,359	7,438
Unrealized holding gains (losses), before tax	(8,746)	30,366	8,921
Total other comprehensive income (loss) before reclassifications, before tax	(8,746)	30,366	8,921
(Gains) losses realized in net income, before tax	(18,351)
Total reclassifications, before tax	(27,097)
Total gain (loss) during the period, before tax		30,366	8,921
Ending balance, before tax	19,628	46,725	16,359
Investment Securities All Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	(73,785)	62,849	201,828
Unrealized holding gains (losses), before tax	(6,259)	(110,316)	(142,623)
Total other comprehensive income (loss) before reclassifications, before tax	(6,259)	(110,316)	(142,623)
Amortization of unrealized holding losses on held-to-maturity (“HTM”) securities, before tax	3,387	3,996	3,514
(Gains) losses realized in net income, before tax	(2,928)	(30,314)	130
Total reclassifications, before tax	(5,800)	(26,318)	3,644
Total gain (loss) during the period, before tax		(136,634)	(138,979)
Ending balance, before tax	(79,585)	(73,785)	62,849
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	(449,917)	(489,660)	(503,027)
Current year benefit plans gains (losses), before tax	9,276	14,125	(24,200)
Total other comprehensive income (loss) before reclassifications, before tax	9,276	14,125	(24,200)
Amortization of prior service credit, before tax	(802)	(4,587)	(7,364)
Amortization of actuarial losses, before tax	28,275	30,205	44,931
Total reclassifications, before tax	36,749	25,618	37,567
Total gain (loss) during the period, before tax		39,743	13,367
Ending balance, before tax	(413,168)	(449,917)	(489,660)
Reclassification of income tax effects to retained earnings, net of tax	(53,960)
Total other comprehensive loss	22,288	24,105	8,610
Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, before tax	(8,268)	(4,093)	(4,082)
Foreign currency translation adjustment, before tax	4,447	(4,020)	(1,323)
Unrealized losses on cash flow hedges, before tax	(12,291)		1,453
Total other comprehensive income (loss) before reclassifications, before tax	(7,844)	(4,020)	130
Accretion of net gain (losses) on terminated cash flow hedges, before tax	(137)	(155)	(141)
Net yield adjustment from cash flow hedges currently in effect, before tax	(3,916)
Total reclassifications, before tax	(11,897)	(155)	(141)
Total gain (loss) during the period, before tax		(4,175)	(11)
Ending balance, before tax	$ (20,165)	$ (8,268)	$ (4,093)

Comprehensive Income - Accumula

Comprehensive Income - Accumulated Other Comprehensive Income (Loss), Net (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 16,486,622	$ 16,173,289	$ 12,335,896
Net gain (loss) during period	(5,149)	(43,009)	(70,633)
Reclassification of income tax effects to retained earnings	(64,029)
Ending balance	16,250,819	16,486,622	16,173,289
Investment Securities With OTTI [Member] \| Investment Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	28,338	9,921	4,518
Net gain (loss) during period	(10,755)	18,417	5,403
Reclassification of income tax effects to retained earnings	(3,115)
Ending balance	14,468	28,338	9,921
Investment Securities All Other [Member] \| Investment Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(44,657)	38,166	122,683
Net gain (loss) during period	(9,011)	(82,823)	(84,517)
Reclassification of income tax effects to retained earnings	(4,950)
Ending balance	(58,618)	(44,657)	38,166
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(272,874)	(296,979)	(305,589)
Net gain (loss) during period	22,288	24,105	8,610
Reclassification of income tax effects to retained earnings	(53,960)
Ending balance	(304,546)	(272,874)	(296,979)
Accumulated Other Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(5,443)	(2,735)	(2,606)
Net gain (loss) during period	(7,671)	(2,708)	(129)
Reclassification of income tax effects to retained earnings	(2,004)
Ending balance	(15,118)	(5,443)	(2,735)
Accumulated Other Comprehensive Income (Loss), Net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(294,636)	(251,627)	(180,994)
Net gain (loss) during period	(5,149)	(43,009)	(70,633)
Reclassification of income tax effects to retained earnings	(64,029)
Ending balance	$ (363,814)	$ (294,636)	$ (251,627)

Other Income and Other Expen127

Other Income and Other Expense - Other Income and Other Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other income:
Credit-related fee income	$ 77,580	$ 70,424	$ 81,558
Letter of credit fees			52,724
Bank owned life insurance			52,984
Other expense:
Professional services	289,862	268,060	267,540
Amortization of capitalized servicing rights	$ 56,172	$ 50,982	$ 49,906

International Activities - Addi

International Activities - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
International Activities [Line Items]
Revenues from international trust-related services	$ 24,000	$ 25,000	$ 26,000
Loans to foreign borrowers	86,971,785	89,864,419
Deposits at foreign office	177,996	201,927
Cayman Islands [Member]
International Activities [Line Items]
Deposits at foreign office	178	202
Canada [Member]
International Activities [Line Items]
Deposits at foreign office	45,000	50,000
Geographic Distribution, Foreign [Member]
International Activities [Line Items]
Loans to foreign borrowers	$ 159,000	$ 292,000
Geographic Concentration Risk [Member] \| Assets, Total [Member]
International Activities [Line Items]
Concentration risk percentage	1.00%
Geographic Concentration Risk [Member] \| Sales Revenue, Net [Member]
International Activities [Line Items]
Concentration risk percentage	1.00%

Derivative Financial Instrum129

Derivative Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Notional amounts of derivative contracts entered into for trading account purposes	$ 9,400,000,000
Net unrealized pre-tax gains related to hedged loans held for sale, commitments to originate loans for sale and commitments to sell loans	16,000,000	$ 28,000,000
Aggregate fair value of derivative financial instruments in a liability position	13,000,000	34,000,000
Net liability positions with counterparties	13,000,000	30,000,000
Aggregate fair value of derivative financial instruments in asset position	13,000,000	15,000,000
Net fair value of derivative financial instruments in a net asset position	13,000,000	11,000,000
Collateral relating to net asset positions	12,000,000	9,000,000
Counterparties [Member]
Derivative [Line Items]
Post collateral requirements relating to positions	12,000,000	27,000,000
Clearinghouse Credit Facilities [Member]
Derivative [Line Items]
Net fair value of derivative financial instruments in a net asset position	2,000,000	63,000,000
Collateral relating to net asset positions	2,000,000	81,000,000
Amount of initial margin posted	52,000,000	111,000,000
Reduction in the fair value of derivative asset due to contractual settlements	(136,000,000)
Reduction in the fair value of derivative liability due to contractual settlements	(70,000,000)
Interest Rate Swap Agreements [Member]
Derivative [Line Items]
Increase in net interest income due to interest rate swap agreements	25,000,000	37,000,000	$ 44,000,000
Notional amounts of derivative contracts entered into for trading account purposes	9,400,000,000
Interest Rate Contracts [Member]
Derivative [Line Items]
Notional amounts of derivative contracts entered into for trading account purposes	29,900,000,000	21,600,000,000
Foreign Currency and Other Option and Futures Contracts [Member]
Derivative [Line Items]
Notional amounts of derivative contracts entered into for trading account purposes	530,000,000,000	$ 471,000,000
Credit Risk Derivative [Member]
Derivative [Line Items]
Fair value of additional collateral to be posted for derivative financial instruments	0
Credit Risk Derivative [Member] \| Maximum [Member]
Derivative [Line Items]
Aggregate fair value of derivative financial instruments in a net liability position	$ 1,000,000

Derivative Financial Instrum130

Derivative Financial Instruments - Information about Interest Rate Swap Agreements (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Notional Amount	$ 9,400,000,000
Average Maturity (in years)	2 years 4 months 24 days
Estimated Fair Value Gain (Loss)	$ 639,000
Variable Rate Commercial Real Estate Loans [Member] \| Cash Flow Hedges [Member]
Derivative [Line Items]
Notional Amount	$ 4,850,000,000
Average Maturity (in years)	1 year 6 months
Weighted-Average Rate, Fixed	1.52%
Weighted-Average Rate, Variable	1.36%
Estimated Fair Value Gain (Loss)	$ 66,000
Fixed Rate Long-Term Borrowings [Member] \| Fair Value Hedges [Member]
Derivative [Line Items]
Notional Amount	$ 4,550,000,000	$ 900,000,000
Average Maturity (in years)	2 years 10 months 25 days	1 year 1 month 6 days
Weighted-Average Rate, Fixed	2.27%	3.75%
Weighted-Average Rate, Variable	2.09%	2.08%
Estimated Fair Value Gain (Loss)	$ 573,000	$ 11,892,000

Derivative Financial Instrum131

Derivative Financial Instruments - Information about Interest Rate Swap Agreements (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)
Derivative [Line Items]
Notional Amount	$ 9,400,000,000
Forward-Starting Interest Rate Swap Agreements [Member]
Derivative [Line Items]
Notional Amount	2,000,000
Fair Value Hedges [Member]
Derivative [Line Items]
Reduction of estimated fair value losses on hedging instruments	41,100,000
Cash Flow Hedges [Member]
Derivative [Line Items]
Reduction of estimated fair value losses on hedging instruments	$ 16,300,000

Derivative Financial Instrum132

Derivative Financial Instruments - Notional Amount of Interest Rate Swap Agreements Outstanding Maturity (Detail)	Dec. 31, 2017USD ($)
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Total	$ 9,400,000,000
Interest Rate Swap Agreements [Member]
Derivative Instruments And Hedging Activities Disclosures [Line Items]
2,018	500,000,000
2,019	4,250,000,000
2,020	3,500,000,000
2,022	650,000,000
2023 through 2027	500,000,000
Total	$ 9,400,000,000

Derivative Financial Instrum133

Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	$ 92,517	$ 295,069
Liability Derivatives, Fair Value	139,186	176,857
Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	91,144	249,988
Liability Derivatives, Fair Value	138,903	175,510
Fair Value Hedges [Member] \| Derivatives Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	1,373	45,081
Liability Derivatives, Fair Value	283	1,347
Interest Rate Swap Agreements [Member] \| Fair Value Hedges [Member] \| Derivatives Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	639	11,892
Commitments to Sell Real Estate Loans [Member] \| Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	2,526	5,210
Liability Derivatives, Fair Value	1,019	399
Commitments to Sell Real Estate Loans [Member] \| Fair Value Hedges [Member] \| Derivatives Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	734	33,189
Liability Derivatives, Fair Value	283	1,347
Mortgage-Related Commitments to Originate Real Estate Loans for Sale [Member] \| Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	8,797	8,060
Liability Derivatives, Fair Value	494	735
Interest Rate Contracts [Member] \| Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	74,164	228,810
Liability Derivatives, Fair Value	132,104	167,737
Foreign Exchange and Other Option and Futures Contracts [Member] \| Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	5,657	7,908
Liability Derivatives, Fair Value	$ 5,286	$ 6,639

Derivative Financial Instrum134

Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Balance Sheet (Parenthetical) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Offsetting [Abstract]
Reduction in estimated fair value of interest rate contracts in asset position	$ (136.2)
Reduction in estimated fair value of interest rate contracts in liability position	$ (12.2)

Derivative Financial Instrum135

Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Statement of Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, Derivatives	$ 12,219	$ 21,707	$ 20,092
Interest Rate Swap Agreements [Member] \| Fixed Rate Long-Term Borrowings [Member] \| Derivatives Designated and Qualifying as Hedging Instruments [Member] \| Fair Value Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives in fair value hedging relationships, Derivatives	(52,392)	(32,000)	(29,359)
Derivatives in fair value hedging relationships, Hedged item	51,628	30,906	28,719
Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, Derivatives	5,398	14,042	10,755
Foreign Exchange and Other Option and Futures Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, Derivatives	$ 6,821	$ 7,665	$ 9,337

Variable Interest Entities - Ad

Variable Interest Entities - Additional Information (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity Disclosure [Abstract]
Other assets for its "investment" in the common securities recognized by the company of various trusts	$ 23,000,000	$ 24,000,000
Total assets of partnerships in which the company invested	1,000,000,000	1,000,000,000
Maximum exposure to loss of investments in real estate partnerships	420,000,000	294,000,000
Unfunded commitments included in company's maximum exposure to loss of investments in real estate partnerships	$ 201,000,000	$ 102,000,000

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Estimated Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading account assets	$ 132,909	$ 323,867
Investment securities	10,896,284	13,332,072
U.S. Treasury and Federal Agencies [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	1,947,487	1,902,544
Obligations of States and Political Subdivisions [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	2,589	3,641
Government Issued or Guaranteed [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	8,716,392	10,954,861
Other Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	128,832	118,516
Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	100,956	352,466
Fair Value Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading account assets	132,909	323,867
Investment securities	10,896,284	13,332,072
Real estate loans held for sale	378,047	1,056,180
Other assets	12,696	58,351
Total assets	11,419,936	14,770,470
Trading account liabilities	137,390	174,376
Other liabilities	1,796	2,481
Total liabilities	139,186	176,857
Fair Value Measurements, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading account assets	47,873	46,135
Investment securities	73,232	301,711
Total assets	121,105	347,846
Fair Value Measurements, Recurring [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading account assets	85,036	277,732
Investment securities	10,823,024	13,030,317
Real estate loans held for sale	378,047	1,056,180
Other assets	3,899	50,291
Total assets	11,290,006	14,414,520
Trading account liabilities	137,390	174,376
Other liabilities	1,302	1,746
Total liabilities	138,692	176,122
Fair Value Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	28	44
Other assets	8,797	8,060
Total assets	8,825	8,104
Other liabilities	494	735
Total liabilities	494	735
Fair Value Measurements, Recurring [Member] \| U.S. Treasury and Federal Agencies [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	1,947,487	1,902,544
Fair Value Measurements, Recurring [Member] \| U.S. Treasury and Federal Agencies [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	1,947,487	1,902,544
Fair Value Measurements, Recurring [Member] \| Obligations of States and Political Subdivisions [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	2,589	3,641
Fair Value Measurements, Recurring [Member] \| Obligations of States and Political Subdivisions [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	2,589	3,641
Fair Value Measurements, Recurring [Member] \| Government Issued or Guaranteed [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	8,716,392	10,954,861
Fair Value Measurements, Recurring [Member] \| Government Issued or Guaranteed [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	8,716,392	10,954,861
Fair Value Measurements, Recurring [Member] \| Privately Issued Mortgage-Backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	28	44
Fair Value Measurements, Recurring [Member] \| Privately Issued Mortgage-Backed Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	28	44
Fair Value Measurements, Recurring [Member] \| Other Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	128,832	118,516
Fair Value Measurements, Recurring [Member] \| Other Debt Securities [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	128,832	118,516
Fair Value Measurements, Recurring [Member] \| Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	100,956	352,466
Fair Value Measurements, Recurring [Member] \| Equity Securities [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	73,232	301,711
Fair Value Measurements, Recurring [Member] \| Equity Securities [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities	$ 27,724	$ 50,755

Fair Value Measurements - Chang

Fair Value Measurements - Changes in Level 3 Assets and Liabilities Measured at Estimated Fair Value on Recurring Basis (Detail) - Fair Value Measurements, Recurring [Member] - Significant Unobservable Inputs (Level 3) [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Privately Issued [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 44	$ 74	$ 103
Total gains (losses) realized/unrealized:
Settlements	(16)	(30)	(29)
Ending Balance	28	44	74
Other Assets and Other Liabilities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	7,325	9,879	17,347
Total gains (losses) realized/unrealized:
Included in earnings	77,832	110,937	87,061
Transfers out of Level 3	(76,854)	(113,491)	(94,529)
Ending Balance	8,303	7,325	9,879
Changes in unrealized gains included in earnings related to assets still held at end of period	$ 7,978	7,256	8,850
Collateralized Debt Obligations [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance		47,393	50,316
Total gains (losses) realized/unrealized:
Included in earnings		30,041
Included in other comprehensive income		(18,268)	3,254
Sales		(58,296)
Settlements		$ (870)	(6,177)
Ending Balance			$ 47,393

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Discount rates for fair value estimations	10.00%
Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Discount rates for fair value estimations	85.00%
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Change in fair value of nonrecurring fair value measured loans for charge-offs and impairment reserves	$ 56	$ 71	$ 75
Fair Value, Measurements, Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loans measured at fair value on nonrecurring basis	210	293	210
Assets taken in foreclosure of defaulted loans measured at fair value on a nonrecurring basis	53	56
Fair Value, Measurements, Nonrecurring [Member] \| Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loans measured at fair value on nonrecurring basis	145	153	106
Fair Value, Measurements, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loans measured at fair value on nonrecurring basis	$ 65	$ 140	$ 104

Fair Value Measurements - Quant

Fair Value Measurements - Quantitative Information Related to Significant Unobservable Inputs (Detail) - Fair Value Measurements, Recurring [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Privately Issued [Member] \| Two Independent Pricing Quotes [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Recurring fair value measurements for certain Level 3 Assets and Liabilities	$ 28	$ 44
Other Assets and Other Liabilities [Member] \| Discounted Cash Flows [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Recurring fair value measurements for certain Level 3 Assets and Liabilities	$ 8,303	$ 7,325
Other Assets and Other Liabilities [Member] \| Discounted Cash Flows [Member] \| Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Commitment expirations	0.00%	0.00%
Other Assets and Other Liabilities [Member] \| Discounted Cash Flows [Member] \| Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Commitment expirations	78.00%	77.00%
Other Assets and Other Liabilities [Member] \| Discounted Cash Flows [Member] \| Weighted Average [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Commitment expirations	22.00%	30.00%

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Amounts and Estimated Fair Value for Financial Instrument Assets (Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financial assets:
Cash and cash equivalents	$ 1,420,888	$ 1,320,549	$ 1,368,040	$ 1,373,357
Interest-bearing deposits at banks	5,078,903	5,000,638
Trading account assets	132,909	323,867
Investment securities	14,664,525	16,250,468
Loans and leases:
Residential real estate loans	19,619,259	22,584,141
Consumer loans	13,251,665	12,130,094
Allowance for credit losses	(1,017,198)	(988,997)	$ (955,992)	$ (919,562)
Loans and leases, net	86,971,785	89,864,419
Financial liabilities:
Noninterest-bearing deposits	(33,975,180)	(32,813,896)
Savings and interest-checking deposits	(51,698,008)	(52,346,207)
Time deposits	(6,580,962)	(10,131,846)
Deposits at Cayman Islands office	(177,996)	(201,927)
Long-term borrowings	(8,141,430)	(9,493,835)
Carrying Amount [Member]
Financial assets:
Cash and cash equivalents	1,420,888	1,320,549
Interest-bearing deposits at banks	5,078,903	5,000,638
Trading account assets	132,909	323,867
Investment securities	14,664,525	16,250,468
Loans and leases:
Commercial loans and leases	21,742,651	22,610,047
Commercial real estate loans	33,366,373	33,506,394
Residential real estate loans	19,613,344	22,590,912
Consumer loans	13,266,615	12,146,063
Allowance for credit losses	(1,017,198)	(988,997)
Loans and leases, net	86,971,785	89,864,419
Accrued interest receivable	327,170	308,805
Financial liabilities:
Noninterest-bearing deposits	(33,975,180)	(32,813,896)
Savings and interest-checking deposits	(51,698,008)	(52,346,207)
Time deposits	(6,580,962)	(10,131,846)
Deposits at Cayman Islands office	(177,996)	(201,927)
Short-term borrowings	(175,099)	(163,442)
Long-term borrowings	(8,141,430)	(9,493,835)
Accrued interest payable	(75,641)	(75,172)
Trading account liabilities	(137,390)	(174,376)
Other financial instruments:
Commitments to originate real estate loans for sale	8,303	7,325
Commitments to sell real estate loans	1,958	36,653
Other credit-related commitments	(125,281)	(136,295)
Interest rate swap agreements used for interest rate risk management	639	11,892
Estimate Fair Value [Member]
Financial assets:
Cash and cash equivalents	1,420,888	1,320,549
Interest-bearing deposits at banks	5,078,903	5,000,638
Trading account assets	132,909	323,867
Investment securities	14,653,074	16,244,412
Loans and leases:
Commercial loans and leases	21,321,282	22,239,428
Commercial real estate loans	32,950,724	33,129,428
Residential real estate loans	19,596,826	22,638,167
Consumer loans	13,161,517	12,061,590
Loans and leases, net	87,030,349	90,068,613
Accrued interest receivable	327,170	308,805
Financial liabilities:
Noninterest-bearing deposits	(33,975,180)	(32,813,896)
Savings and interest-checking deposits	(51,698,008)	(52,346,207)
Time deposits	(6,635,048)	(10,222,585)
Deposits at Cayman Islands office	(177,996)	(201,927)
Short-term borrowings	(175,099)	(163,442)
Long-term borrowings	(8,193,783)	(9,473,844)
Accrued interest payable	(75,641)	(75,172)
Trading account liabilities	(137,390)	(174,376)
Other financial instruments:
Commitments to originate real estate loans for sale	8,303	7,325
Commitments to sell real estate loans	1,958	36,653
Other credit-related commitments	(125,281)	(136,295)
Interest rate swap agreements used for interest rate risk management	639	11,892
Estimate Fair Value [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets:
Cash and cash equivalents	1,352,035	1,249,654
Trading account assets	47,873	46,135
Investment securities	73,232	301,711
Estimate Fair Value [Member] \| Significant Observable Inputs (Level 2) [Member]
Financial assets:
Cash and cash equivalents	68,853	70,895
Interest-bearing deposits at banks	5,078,903	5,000,638
Trading account assets	85,036	277,732
Investment securities	14,469,127	15,821,176
Loans and leases:
Commercial real estate loans	22,130	642,590
Residential real estate loans	4,440,645	4,912,488
Loans and leases, net	4,462,775	5,555,078
Accrued interest receivable	327,170	308,805
Financial liabilities:
Noninterest-bearing deposits	(33,975,180)	(32,813,896)
Savings and interest-checking deposits	(51,698,008)	(52,346,207)
Time deposits	(6,635,048)	(10,222,585)
Deposits at Cayman Islands office	(177,996)	(201,927)
Short-term borrowings	(175,099)	(163,442)
Long-term borrowings	(8,193,783)	(9,473,844)
Accrued interest payable	(75,641)	(75,172)
Trading account liabilities	(137,390)	(174,376)
Other financial instruments:
Commitments to sell real estate loans	1,958	36,653
Interest rate swap agreements used for interest rate risk management	639	11,892
Estimate Fair Value [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Investment securities	110,715	121,525
Loans and leases:
Commercial loans and leases	21,321,282	22,239,428
Commercial real estate loans	32,928,594	32,486,838
Residential real estate loans	15,156,181	17,725,679
Consumer loans	13,161,517	12,061,590
Loans and leases, net	82,567,574	84,513,535
Other financial instruments:
Commitments to originate real estate loans for sale	8,303	7,325
Other credit-related commitments	$ (125,281)	$ (136,295)

Commitments and Contingencies -

Commitments and Contingencies - Company's Significant Commitments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Commitments to extend credit
Home equity lines of credit	$ 5,482,622	$ 5,499,609
Commercial real estate loans to be sold	194,763	70,100
Other commercial real estate	6,050,569	6,451,709
Residential real estate loans to be sold	347,113	478,950
Other residential real estate	201,426	232,721
Commercial and other	12,733,815	12,298,473
Standby letters of credit	2,497,844	2,987,091
Commercial letters of credit	46,739	44,723
Financial guarantees and indemnification contracts	3,434,381	3,043,580
Commitments to sell real estate loans	$ 812,217	$ 1,489,237

Commitments and Contingencie143

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Maximum credit risk for recourse associated with loans sold under Federal National Mortgage Association Delegated Underwriting and Servicing program	$ 3,300,000,000	$ 2,800,000,000
Period of noncancelable operating lease in years	21 years
Payments agreed to pay for legal settlements	$ 60,000,000
Payment of legal settlement expense	$ 16,000,000
Legal settlement, date of dismissal	Oct. 12, 2017
Minimum [Member]
Loss Contingencies [Line Items]
Range of reasonably possible losses	$ 0
Maximum [Member]
Loss Contingencies [Line Items]
Range of reasonably possible losses	$ 50,000,000

Commitments and Contingencie144

Commitments and Contingencies - Minimum Lease Payments Under Noncancellable Operating Leases (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,018	$ 92,824
2,019	87,298
2,020	70,490
2,021	54,685
2,022	41,953
Later years	82,195
Total	$ 429,445

Segment Information - Summary o

Segment Information - Summary of Reclassified Segment Information on Comparable Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net Interest Income	$ 3,781,044	$ 3,469,887	$ 2,842,587
Net income	1,408,306	1,315,114	1,079,667
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		3,469,887	2,842,587
Business Banking [Member]
Segment Reporting Information [Line Items]
Net income		103,758	109,744
Business Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income	393,948	371,889	357,378
Net income	115,933	103,758	109,744
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net income		411,379	430,886
Commercial Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income	809,301	785,339	753,362
Net income	436,871	411,379	430,886
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Net income		350,358	340,641
Commercial Real Estate [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income	649,378	608,385	577,922
Net income	364,135	350,358	340,641
Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Net income		163,538	59,272
Discretionary Portfolio [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income	277,095	345,926	97,626
Net income	134,968	163,538	59,272
Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net income		55,453	74,362
Residential Mortgage Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income	30,328	29,809	39,969
Net income	45,567	55,453	74,362
Retail Banking [Member]
Segment Reporting Information [Line Items]
Net income		294,373	288,097
Retail Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income	1,210,066	1,107,388	951,740
Net income	$ 377,166	294,373	288,097
All Other [Member]
Segment Reporting Information [Line Items]
Net income		(63,745)	(223,335)
All Other [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		221,151	64,590
As Previously Reported [Member]
Segment Reporting Information [Line Items]
Net income		1,315,114	1,079,667
As Previously Reported [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		3,469,887	2,842,587
As Previously Reported [Member] \| Business Banking [Member]
Segment Reporting Information [Line Items]
Net income		93,346	98,758
As Previously Reported [Member] \| Business Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		354,333	338,855
As Previously Reported [Member] \| Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net income		411,696	431,030
As Previously Reported [Member] \| Commercial Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		785,874	753,604
As Previously Reported [Member] \| Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Net income		350,358	340,641
As Previously Reported [Member] \| Commercial Real Estate [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		608,385	577,922
As Previously Reported [Member] \| Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Net income		163,538	59,272
As Previously Reported [Member] \| Discretionary Portfolio [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		345,926	97,626
As Previously Reported [Member] \| Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net income		79,678	88,578
As Previously Reported [Member] \| Residential Mortgage Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		70,655	63,939
As Previously Reported [Member] \| Retail Banking [Member]
Segment Reporting Information [Line Items]
Net income		274,646	267,518
As Previously Reported [Member] \| Retail Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		1,074,125	917,041
As Previously Reported [Member] \| All Other [Member]
Segment Reporting Information [Line Items]
Net income		(58,148)	(206,130)
As Previously Reported [Member] \| All Other [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		230,589	93,600
Impact of Changes [Member] \| Business Banking [Member]
Segment Reporting Information [Line Items]
Net income		10,412	10,986
Impact of Changes [Member] \| Business Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		17,556	18,523
Impact of Changes [Member] \| Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net income		(317)	(144)
Impact of Changes [Member] \| Commercial Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		(535)	(242)
Impact of Changes [Member] \| Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net income		(24,225)	(14,216)
Impact of Changes [Member] \| Residential Mortgage Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		(40,846)	(23,970)
Impact of Changes [Member] \| Retail Banking [Member]
Segment Reporting Information [Line Items]
Net income		19,727	20,579
Impact of Changes [Member] \| Retail Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		33,263	34,699
Impact of Changes [Member] \| All Other [Member]
Segment Reporting Information [Line Items]
Net income		(5,597)	(17,205)
Impact of Changes [Member] \| All Other [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Interest Income		$ (9,438)	$ (29,010)

Segment Information - Informati

Segment Information - Information about Company's Segments (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net interest income	$ 3,781,044	$ 3,469,887	$ 2,842,587
Noninterest income	1,851,143	1,825,996	1,825,037
Total income	5,632,187	5,295,883	4,667,624
Provision for credit losses	168,000	190,000	170,000
Amortization of core deposit and other intangible assets	31,366	42,613	26,424
Depreciation and other amortization	165,759	157,978	148,925
Other noninterest expense	2,943,200	2,846,894	2,647,583
Income before taxes	2,323,862	2,058,398	1,674,692
Income tax expense (benefit)	915,556	743,284	595,025
Net income	1,408,306	1,315,114	1,079,667
Average total assets	120,860,000	124,340,000	101,780,000
Capital expenditures	79,000	108,000	82,000
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income		3,469,887	2,842,587
All Other [Member]
Segment Reporting Information [Line Items]
Net interest income	410,928	221,151	64,590
Noninterest income	609,945	570,475	594,586
Total income	1,020,873	791,626	659,176
Provision for credit losses	8,265	(3,910)	62,074
Amortization of core deposit and other intangible assets	30,306	42,613	26,424
Depreciation and other amortization	69,923	68,541	64,852
Other noninterest expense	1,019,465	892,625	959,345
Income before taxes	(107,086)	(208,243)	(453,519)
Income tax expense (benefit)	(40,752)	(144,498)	(230,184)
Net income	(66,334)	(63,745)	(223,335)
Average total assets	13,684,000	16,885,000	12,870,000
Capital expenditures	44,000	62,000	68,000
Business Banking [Member]
Segment Reporting Information [Line Items]
Net income		103,758	109,744
Business Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	393,948	371,889	357,378
Noninterest income	112,512	108,783	108,195
Total income	506,460	480,672	465,573
Provision for credit losses	15,598	12,709	15,513
Depreciation and other amortization	393	404	407
Other noninterest expense	294,493	292,124	264,163
Income before taxes	195,976	175,435	185,490
Income tax expense (benefit)	80,043	71,677	75,746
Net income	115,933	103,758	109,744
Average total assets	5,602,000	5,456,000	5,339,000
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net income		411,379	430,886
Commercial Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	809,301	785,339	753,362
Noninterest income	283,447	274,923	290,142
Total income	1,092,748	1,060,262	1,043,504
Provision for credit losses	11,876	34,903	25,089
Depreciation and other amortization	509	520	566
Other noninterest expense	339,936	327,616	288,303
Income before taxes	740,427	697,223	729,546
Income tax expense (benefit)	303,556	285,844	298,660
Net income	436,871	411,379	430,886
Average total assets	26,573,000	25,592,000	24,143,000
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Net income		350,358	340,641
Commercial Real Estate [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	649,378	608,385	577,922
Noninterest income	169,966	179,706	142,948
Total income	819,344	788,091	720,870
Provision for credit losses	(7,524)	(3,447)	(8,003)
Amortization of core deposit and other intangible assets	1,060
Depreciation and other amortization	24,410	20,120	19,247
Other noninterest expense	207,493	204,965	169,688
Income before taxes	593,905	566,453	539,938
Income tax expense (benefit)	229,770	216,095	199,297
Net income	364,135	350,358	340,641
Average total assets	22,741,000	21,131,000	18,827,000
Capital expenditures	1,000
Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Net income		163,538	59,272
Discretionary Portfolio [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	277,095	345,926	97,626
Noninterest income	23,851	26,075	28,114
Total income	300,946	372,001	125,740
Provision for credit losses	31,119	32,925	7,599
Depreciation and other amortization	279	472	679
Other noninterest expense	76,021	95,300	49,839
Income before taxes	193,527	243,304	67,623
Income tax expense (benefit)	58,559	79,766	8,351
Net income	134,968	163,538	59,272
Average total assets	37,203,000	40,867,000	26,648,000
Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net income		55,453	74,362
Residential Mortgage Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	30,328	29,809	39,969
Noninterest income	321,589	342,858	336,099
Total income	351,917	372,667	376,068
Provision for credit losses	1,254	(3,617)	(5,225)
Depreciation and other amortization	32,011	30,264	27,883
Other noninterest expense	247,639	258,141	233,651
Income before taxes	71,013	87,879	119,759
Income tax expense (benefit)	25,446	32,426	45,397
Net income	45,567	55,453	74,362
Average total assets	2,355,000	2,569,000	2,918,000
Retail Banking [Member]
Segment Reporting Information [Line Items]
Net income		294,373	288,097
Retail Banking [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net interest income	1,210,066	1,107,388	951,740
Noninterest income	329,833	323,176	324,953
Total income	1,539,899	1,430,564	1,276,693
Provision for credit losses	107,412	120,437	72,953
Depreciation and other amortization	38,234	37,657	35,291
Other noninterest expense	758,153	776,123	682,594
Income before taxes	636,100	496,347	485,855
Income tax expense (benefit)	258,934	201,974	197,758
Net income	377,166	294,373	288,097
Average total assets	12,702,000	11,840,000	11,035,000
Capital expenditures	$ 34,000	$ 46,000	$ 14,000

Segment Information - Inform147

Segment Information - Information about Company's Segments (Parenthetical) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting [Abstract]
Taxable-equivalent adjustment	$ 34,570,000	$ 26,962,000	$ 24,463,000

Segment Information - Intersegm

Segment Information - Intersegment Activity Eliminated in Arriving at Consolidated Totals was Included in "All Other" Category (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 5,632,187	$ 5,295,883	$ 4,667,624
Income taxes (benefit)	915,556	743,284	595,025
Net income (loss)	1,408,306	1,315,114	1,079,667
Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Revenues	(43,941)	(48,625)	(48,972)
Expenses	(32,623)	(40,422)	(13,332)
Income taxes (benefit)	(4,606)	(3,338)	(14,503)
Net income (loss)	$ (6,712)	$ (4,865)	$ (21,137)

Segment Information - Additiona

Segment Information - Additional Information (Detail)	12 Months Ended
Segment Information - Additional Information (Detail)	Dec. 31, 2017
Segment Reporting [Abstract]
Percent of maximum revenue from single customer on total revenues	10.00%

Regulatory Matters - Additional

Regulatory Matters - Additional Information (Detail) - USD ($)	Jan. 01, 2019	Dec. 31, 2017	Dec. 31, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Funds available for payment of dividends to M&T from banking subsidiaries		$ 397,000,000
Required subsidiary noninterest-earning reserves against certain deposit liabilities		$ 679,401,000	$ 594,831,000
Capital conservation buffer		1.25%	0.625%
Scenario Forecast [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer	2.50%
Maximum [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Consolidated assets required per Federal Reserve Board to submit annual capital plans		$ 50,000,000,000

Regulatory Matters - Summary of

Regulatory Matters - Summary of Required Minimum and Well Capitalized Capital Ratios (Detail)	Dec. 31, 2017
Banking And Thrift [Abstract]
Common equity Tier 1 ("CET1") to risk-weighted assets, Minimum	4.50%
Tier 1 capital to risk-weighted assets, Minimum	6.00%
Total capital to risk-weighted assets, Minimum	8.00%
Leverage — Tier 1 capital to average total assets, as defined, Minimum	4.00%
Common equity Tier 1 ("CET1") to risk-weighted assets, Well Capitalized	6.50%
Tier 1 capital to risk-weighted assets, Well capitalized	8.00%
Total capital to risk-weighted assets, Well capitalized	10.00%
Leverage — Tier 1 capital to average total assets, as defined, Well capitalized	5.00%

Regulatory Matters - Capital Ra

Regulatory Matters - Capital Ratios and Amounts of Company and its Banking Subsidiaries (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Ratio	4.50%
Ratio	6.00%
Ratio	8.00%
M&T (Consolidated) [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Amount	$ 10,675,735	$ 10,849,642
Ratio	10.99%	10.70%
Amount	$ 11,908,166	$ 12,083,948
Ratio	12.26%	11.92%
Amount	$ 14,328,467	$ 14,282,492
Ratio	14.75%	14.09%
Amount	$ 11,908,166	$ 12,083,948
Ratio	10.31%	9.99%
M&T Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Amount	$ 9,978,163	$ 10,115,688
Ratio	10.30%	10.02%
Amount	$ 9,978,163	$ 10,115,688
Ratio	10.30%	10.02%
Amount	$ 12,012,171	$ 11,812,114
Ratio	12.40%	11.70%
Amount	$ 9,978,163	$ 10,115,688
Ratio	8.68%	8.41%
Wilmington Trust, N.A. [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Amount	$ 529,988	$ 496,801
Ratio	48.16%	57.08%
Amount	$ 529,988	$ 496,801
Ratio	48.16%	57.08%
Amount	$ 534,235	$ 501,111
Ratio	48.54%	57.57%
Amount	$ 529,988	$ 496,801
Ratio	13.03%	15.31%

Relationship with Bayview Le153

Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P. - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2017	Apr. 28, 2017
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	$ 8,141,430	$ 9,493,835
Bayview Lending Group [Member]
Schedule of Equity Method Investments [Line Items]
Minority interest in Bayview Lending Group LLC	20.00%
Carrying value of minority interest investment in Bayview Lending Group LLC	$ 0
Bayview Lending Group and Bayview Financial [Member]
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of mortgage servicing rights	3,000,000	3,500,000
Revenues from servicing	17,000	19,000	$ 23,000
Bayview Financial [Member]
Schedule of Equity Method Investments [Line Items]
Outstanding principal balances of residential mortgage loans from Bayview Financial	56,600,000	30,400,000
Revenues from sub-servicing	103,000	98,000	$ 115,000
Investment securities in held-to-maturity portfolio securitized by Bayview Financial	136,000	$ 158,000
Loan to Bayview Financial					$ 100,000
Bayview Financial [Member] \| Syndicated Loan Facility [Member]
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount				$ 750,000
Bayview Financial [Member] \| Syndicated Loan Facility [Member] \| M&T Bank [Member]
Schedule of Equity Method Investments [Line Items]
Loan facility carrying amount	$ 88,000

Parent Company Financial Sta154

Parent Company Financial Statements - Condensed Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments in consolidated subsidiaries
Total assets	$ 118,593,487	$ 123,449,206
Liabilities
Long-term borrowings	8,141,430	9,493,835
Total liabilities	102,342,668	106,962,584
Shareholders’ equity	16,250,819	16,486,622	$ 16,173,289	$ 12,335,896
Total liabilities and shareholders’ equity	118,593,487	123,449,206
Parent Company [Member]
Assets
Cash in subsidiary bank	13,379	15,003
Due from consolidated bank subsidiaries
Money-market savings	1,616,147	1,767,184
Current income tax receivable	4,437	3,061
Total due from consolidated bank subsidiaries	1,620,584	1,770,245
Investments in consolidated subsidiaries
Banks	14,841,794	15,003,964
Other	253,904	161,201
Investments in unconsolidated subsidiaries (note 19)	23,453	23,643
Investment in Bayview Lending Group LLC		11,908
Other assets	66,023	71,687
Total assets	16,819,137	17,057,651
Liabilities
Accrued expenses and other liabilities	49,093	54,487
Long-term borrowings	519,225	516,542
Total liabilities	568,318	571,029
Shareholders’ equity	16,250,819	16,486,622
Total liabilities and shareholders’ equity	$ 16,819,137	$ 17,057,651

Parent Company Financial Sta155

Parent Company Financial Statements - Condensed Statement of Income (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Expense
Interest on long-term borrowings	$ 189,372	$ 231,017	$ 252,766
Other expense	3,140,325	3,047,485	2,822,932
Income tax credits	(915,556)	(743,284)	(595,025)
Equity in undistributed income of subsidiaries
Net income	$ 1,408,306	$ 1,315,114	$ 1,079,667
Net income per common share
Basic	$ 8.72	$ 7.80	$ 7.22
Diluted	$ 8.70	$ 7.78	$ 7.18
Parent Company [Member]
Income
Dividends from consolidated bank subsidiaries	$ 1,540,000	$ 1,930,000	$ 480,000
Equity in earnings of Bayview Lending Group LLC	352	(10,752)	(14,267)
Other income	9,493	5,530	2,364
Total income	1,549,845	1,924,778	468,097
Expense
Interest on long-term borrowings	21,591	18,963	24,453
Other expense	19,636	21,361	16,793
Total expense	41,227	40,324	41,246
Income before income taxes and equity in undistributed income of subsidiaries	1,508,618	1,884,454	426,851
Income tax credits	26,453	17,247	19,965
Income before equity in undistributed income of subsidiaries	1,535,071	1,901,701	446,816
Equity in undistributed income of subsidiaries
Net income of subsidiaries	1,413,235	1,343,413	1,112,851
Less: dividends received	(1,540,000)	(1,930,000)	(480,000)
Equity in undistributed income of subsidiaries	(126,765)	(586,587)	632,851
Net income	$ 1,408,306	$ 1,315,114	$ 1,079,667
Net income per common share
Basic	$ 8.72	$ 7.80	$ 7.22
Diluted	$ 8.70	$ 7.78	$ 7.18

Parent Company Financial Sta156

Parent Company Financial Statements - Condensed Statement of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net income	$ 1,408,306	$ 1,315,114	$ 1,079,667
Adjustments to reconcile net income to net cash provided by operating activities
Benefit (provision) for deferred income taxes	400,790	174,013	396,596
Net gain on sales of assets	(53,467)	(63,222)	(67,759)
Net cash provided by operating activities	2,781,935	1,183,411	1,742,408
Cash flows from investing activities
Other, net	19,825	277,961	10,876
Net cash provided by investing activities	3,394,925	(720,768)	7,714,282
Cash flows from financing activities
Payments on long-term borrowings	(3,433,440)	(1,119,898)	(8,912,474)
Purchases of treasury stock	(1,205,905)	(641,334)
Dividends paid — common	(457,402)	(441,891)	(375,017)
Dividends paid — preferred	(72,734)	(81,270)	(81,270)
Redemption of Series D preferred stock		(500,000)
Other, net	10,675	161,691	69,766
Net cash used by financing activities	(6,076,521)	(510,134)	(9,462,007)
Net increase (decrease) in cash and cash equivalents	100,339	(47,491)	(5,317)
Cash and cash equivalents at beginning of year	1,320,549	1,368,040	1,373,357
Cash and cash equivalents at end of year	1,420,888	1,320,549	1,368,040
Supplemental disclosure of cash flow information
Interest received during the year	4,155,723	3,903,374	3,134,311
Interest paid during the year	405,290	498,951	400,329
Income taxes received during the year	494,205	276,866	378,660
Parent Company [Member]
Cash flows from operating activities
Net income	1,408,306	1,315,114	1,079,667
Adjustments to reconcile net income to net cash provided by operating activities
Equity in undistributed income of subsidiaries	126,765	586,587	(632,851)
Benefit (provision) for deferred income taxes	4,543	(3,157)	(3,655)
Net change in accrued income and expense	(170)	12,898	21,780
Net gain on sales of assets	(2,995)	(2,342)	119
Net cash provided by operating activities	1,536,449	1,909,100	465,060
Cash flows from investing activities
Proceeds from sales or maturities of investment securities		51	755
Other, net	12,407	13,619	14,038
Net cash provided by investing activities	12,407	13,670	14,793
Cash flows from financing activities
Payments on long-term borrowings			(322,621)
Purchases of treasury stock	(1,205,905)	(641,334)
Dividends paid — common	(457,402)	(441,891)	(375,017)
Dividends paid — preferred	(72,734)	(81,270)	(81,270)
Redemption of Series D preferred stock		(500,000)
Proceeds from issuance of Series F preferred stock		495,000
Other, net	34,524	143,764	76,364
Net cash used by financing activities	(1,701,517)	(1,025,731)	(702,544)
Net increase (decrease) in cash and cash equivalents	(152,661)	897,039	(222,691)
Cash and cash equivalents at beginning of year	1,782,187	885,148	1,107,839
Cash and cash equivalents at end of year	1,629,526	1,782,187	885,148
Supplemental disclosure of cash flow information
Interest received during the year	2,313	1,931	1,905
Interest paid during the year	18,498	15,918	30,420
Income taxes received during the year	$ 21,740	$ 8,877	$ 16,696

Recent Accounting Developments

Recent Accounting Developments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Reclassification from accumulated other comprehensive income to retained earnings		$ 64,029
Federal income tax rate		35.00%
Scenario Forecast [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Federal income tax rate	21.00%
ASU 2016-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
New accounting pronouncement or change in accounting principle effect of adoption change in income tax expense (benefit)		$ (22,000)
Tax Cut and Jobs Act [Member] \| Scenario Forecast [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Federal income tax rate	21.00%
ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Expense recognized on credit card rewards in other costs of operations		13,000	$ 6,000
ASU 2016-01 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Fair value on marketable equity securities		101,000
ASU 2016-02 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Minimum lease payments under noncancelable operating lease agreements		$ 429,000
Lessee, operating lease term		12 months