M&T Bank (MTB) 10-K 21 Feb 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Feb. 14, 2014	Jun. 30, 2013
Document And Entity Information [Abstract]	'	'	'
Document Type	'10-K	'	'
Amendment Flag	'false	'	'
Document Period End Date	31-Dec-13	'	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Trading Symbol	'MTB	'	'
Entity Registrant Name	'M&T BANK CORP	'	'
Entity Central Index Key	'0000036270	'	'
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	'	131,031,744	'
Entity Public Float	'	'	$12,619,414,344

Consolidated_Balance_Sheet

Consolidated Balance Sheet (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Assets	'	'
Cash and due from banks	$1,573,361	$1,983,615
Interest-bearing deposits at banks	1,651,138	129,945
Federal funds sold	99,573	3,000
Trading account	376,131	488,966
Investment securities (includes pledged securities that can be sold or repledged of $1,696,438 at December 31, 2013; $1,801,842 at December 31, 2012)	'	'
Available for sale (cost: $4,444,365 at December 31, 2013; $4,643,070 at December 31, 2012)	4,531,786	4,739,437
Held to maturity (fair value: $3,860,127 at December 31, 2013; $976,883 at December 31, 2012)	3,966,130	1,032,276
Other (fair value: $298,581 at December 31, 2013; $302,648 at December 31, 2012)	298,581	302,648
Total investment securities	8,796,497	6,074,361
Loans and leases	64,325,783	66,790,186
Unearned discount	-252,624	-219,229
Loans and leases, net of unearned discount	64,073,159	66,570,957
Allowance for credit losses	-916,676	-925,860
Loans and leases, net	63,156,483	65,645,097
Premises and equipment	633,520	594,652
Goodwill	3,524,625	3,524,625
Core deposit and other intangible assets	68,851	115,763
Accrued interest and other assets	5,282,212	4,448,779
Total assets	85,162,391	83,008,803
Liabilities	'	'
Noninterest-bearing deposits	24,661,007	24,240,802
NOW accounts	1,989,441	1,979,619
Savings deposits	36,621,580	33,783,947
Time deposits	3,523,838	4,562,366
Deposits at Cayman Islands office	322,746	1,044,519
Total deposits	67,118,612	65,611,253
Federal funds purchased and agreements to repurchase securities	260,455	1,074,482
Accrued interest and other liabilities	1,368,922	1,512,717
Long-term borrowings	5,108,870	4,607,758
Total liabilities	73,856,859	72,806,210
Shareholders' equity	'	'
Preferred stock, $1.00 par, 1,000,000 shares authorized; Issued and outstanding: Liquidation preference of $1,000 per share: 381,500 shares at December 31, 2013 and December 31, 2012; Liquidation preference of $10,000 per share: 50,000 shares at December 31, 2013 and December 31, 2012	881,500	872,500
Common stock, $.50 par, 250,000,000 shares authorized, 130,516,364 shares issued at December 31, 2013; 128,176,912 shares issued at December 31, 2012	65,258	64,088
Common stock issuable, 47,231 shares at December 31, 2013; 57,409 shares at December 31, 2012	2,915	3,473
Additional paid-in capital	3,232,014	3,025,520
Retained earnings	7,188,004	6,477,276
Accumulated other comprehensive income (loss), net	-64,159	-240,264
Total shareholders' equity	11,305,532	10,202,593
Total liabilities and shareholders' equity	$85,162,391	$83,008,803

Consolidated_Balance_Sheet_Par

Consolidated Balance Sheet (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Pledged securities that can be sold or repledged	$1,696,438	$1,801,842
Investment securities, available for sale, amortized cost	4,444,365	4,643,070
Investment securities, held to maturity, fair value	3,860,127	976,883
Other, fair value	$298,581	$302,648
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	130,516,364	128,176,912
Common stock issuable, shares	47,231	57,409
Series A And Series C [Member]	'	'
Preferred stock, shares issued and outstanding	381,500	381,500
Preferred stock, liquidation preference per share	$1,000	$1,000
Series D Preferred Stock [Member]	'	'
Preferred stock, shares issued and outstanding	50,000	50,000
Preferred stock, liquidation preference per share	$10,000	$10,000

Consolidated_Statement_of_Inco

Consolidated Statement of Income (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Interest income	'	'	'
Loans and leases, including fees	$2,734,708	$2,704,156	$2,522,567
Deposits at banks	5,201	1,221	2,934
Federal funds sold	104	21	57
Agreements to resell securities	10	'	132
Trading account	1,265	1,126	1,198
Investment securities	'	'	'
Fully taxable	209,244	227,116	256,057
Exempt from federal taxes	6,802	8,045	9,142
Total interest income	2,957,334	2,941,685	2,792,087
Interest expense	'	'	'
NOW accounts	1,287	1,343	1,145
Savings deposits	54,948	68,011	84,314
Time deposits	26,439	46,102	71,014
Deposits at Cayman Islands office	1,018	1,130	962
Short-term borrowings	430	1,286	1,030
Long-term borrowings	199,983	225,297	243,866
Total interest expense	284,105	343,169	402,331
Net interest income	2,673,229	2,598,516	2,389,756
Provision for credit losses	185,000	204,000	270,000
Net interest income after provision for credit losses	2,488,229	2,394,516	2,119,756
Other income	'	'	'
Mortgage banking revenues	331,265	349,064	166,021
Service charges on deposit accounts	446,941	446,698	455,095
Trust income	496,008	471,852	332,385
Brokerage services income	65,647	59,059	56,470
Trading account and foreign exchange gains	40,828	35,634	27,224
Gain on bank investment securities	56,457	9	150,187
Total other-than-temporary impairment ("OTTI") losses	-1,884	-32,067	-72,915
Portion of OTTI losses recognized in other comprehensive income (before taxes)	-7,916	-15,755	-4,120
Net OTTI losses recognized in earnings	-9,800	-47,822	-77,035
Equity in earnings of Bayview Lending Group LLC	-16,126	-21,511	-24,231
Other revenues from operations	453,985	374,287	496,796
Total other income	1,865,205	1,667,270	1,582,912
Other expense	'	'	'
Salaries and employee benefits	1,355,178	1,314,540	1,203,993
Equipment and net occupancy	264,327	257,551	249,514
Printing, postage and supplies	39,557	41,929	40,917
Amortization of core deposit and other intangible assets	46,912	60,631	61,617
FDIC assessments	69,584	101,110	100,230
Other costs of operations	860,327	733,499	821,797
Total other expense	2,635,885	2,509,260	2,478,068
Income (loss) before taxes	1,717,549	1,552,526	1,224,600
Income taxes	579,069	523,028	365,121
Net income	1,138,480	1,029,498	859,479
Net income available to common shareholders	'	'	'
Basic	1,062,429	953,390	781,743
Diluted	$1,062,496	$953,429	$781,765
Net income per common share	'	'	'
Basic	$8.26	$7.57	$6.37
Diluted	$8.20	$7.54	$6.35

Consolidated_Statement_of_Comp

Consolidated Statement of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement Of Partners Capital [Abstract]	'	'	'
Net income	$1,138,480	$1,029,498	$859,479
Other comprehensive income, net of tax and reclassification adjustments:	'	'	'
Net unrealized gains (losses) on investment securities	-2,865	114,825	6,687
Reclassification to income for amortization of gains on terminated cash flow hedges	'	-112	-281
Foreign currency translation adjustment	381	519	-803
Defined benefit plans liability adjustment	178,589	945	-156,824
Total gain (loss) during the period	176,105	116,177	-151,221
Total comprehensive income	$1,314,585	$1,145,675	$708,258

Consolidated_Statement_of_Cash

Consolidated Statement of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities	'	'	'
Net income	$1,138,480	$1,029,498	$859,479
Adjustments to reconcile net income to net cash provided by operating activities	'	'	'
Provision for credit losses	185,000	204,000	270,000
Depreciation and amortization of premises and equipment	91,469	84,375	80,304
Amortization of capitalized servicing rights	65,354	59,555	55,859
Amortization of core deposit and other intangible assets	46,912	60,631	61,617
Provision for deferred income taxes	139,785	131,858	33,924
Asset write-downs	17,918	63,790	170,632
Net gain on sales of assets	-127,890	-6,868	-187,120
Net change in accrued interest receivable, payable	-10,523	-13,898	-27,508
Net change in other accrued income and expense	71,523	-200,704	147,465
Net change in loans originated for sale	-674,062	-924,839	238,156
Net change in trading account assets and liabilities	-11,642	12,583	69,438
Net cash provided by operating activities	932,324	499,981	1,772,246
Cash flows from investing activities	'	'	'
Proceeds from sales of investment securities Available for sale	1,081,802	49,528	1,909,829
Proceeds from sales of investment securities Other	13,172	78,071	116,410
Proceeds from maturities of investment securities Available for sale	1,034,564	1,585,260	1,307,567
Proceeds from maturities of investment securities Held to maturity	287,837	329,279	272,841
Purchases of investment securities Available for sale	-197,931	-28,161	-3,491,759
Purchases of investment securities Held to maturity	-1,977,064	-285,125	-28,454
Purchases of investment securities Other	-9,105	-13,833	-30,727
Net decrease in agreements to resell securities	'	'	15,000
Net (increase) decrease in loans and leases	123,120	-5,672,747	-2,233,600
Net (increase) decrease in interest-bearing deposits at banks	-1,521,193	25,015	2,552,527
Capital expenditures, net	-129,563	-91,519	-70,008
Acquisitions, net of cash acquired Banks and bank holding companies	'	'	178,940
Purchase of Wilmington Trust Corporation preferred stock	'	'	-330,000
Net (increase) decrease in loan servicing advances	-1,004,923	-69,084	55,698
Other, net	95,706	32,458	144,668
Net cash provided (used) by investing activities	-2,203,578	-4,060,858	368,932
Cash flows from financing activities	'	'	'
Net increase in deposits	1,513,884	6,230,391	742,653
Net increase (decrease) in short-term borrowings	-814,027	292,422	-313,050
Proceeds from long-term borrowings	799,760	'	'
Payments on long-term borrowings	-261,212	-2,080,167	-1,809,984
Dividends paid - common	-365,349	-357,717	-350,129
Dividends paid - preferred	-53,450	-53,450	-48,203
Proceeds from issuance of preferred stock	'	'	495,000
Redemption of preferred stock	'	'	-370,000
Other, net	137,967	63,616	31,177
Net cash provided (used) by financing activities	957,573	4,095,095	-1,622,536
Net increase (decrease) in cash and cash equivalents	-313,681	534,218	518,642
Cash and cash equivalents at beginning of year	1,986,615	1,452,397	933,755
Cash and cash equivalents at end of year	1,672,934	1,986,615	1,452,397
Supplemental disclosure of cash flow information	'	'	'
Interest received during the year	2,894,699	2,931,409	2,807,071
Interest paid during the year	301,734	371,887	440,810
Income taxes paid during the year	389,008	405,598	251,810
Supplemental schedule of noncash investing and financing activities	'	'	'
Available-for-sale investment securities	1,690,490	'	'
Held-to-maturity investment securities	1,245,444	'	'
Capitalized servicing rights	30,879	'	'
Real estate acquired in settlement of loans	44,804	48,932	81,588
Acquisitions Fair value of	'	'	'
Assets acquired (noncash)	'	'	10,666,102
Liabilities assumed	'	'	10,044,555
Common stock issued	'	'	$405,557

Consolidated_Statement_of_Chan

Consolidated Statement of Changes In Shareholders' Equity (USD $)

Total

Series C stock warrants [Member]

Series A stock warrants [Member]

Preferred stock [Member]

Preferred stock [Member]

Preferred stock [Member]

Common stock [Member]

Common stock [Member]

Common stock [Member]

Common stock issuable [Member]

Common stock issuable [Member]

Common stock issuable [Member]

Additional paid-in capital [Member]

Additional paid-in capital [Member]

Additional paid-in capital [Member]

Retained earnings [Member]

Retained earnings [Member]

Retained earnings [Member]

Accumulated other comprehensive income (loss), net [Member]

Accumulated other comprehensive income (loss), net [Member]

Accumulated other comprehensive income (loss), net [Member]

Treasury Stock [Member]

Treasury Stock [Member]

Treasury Stock [Member]

In Thousands, unless otherwise specified

Series C stock warrants [Member]

Series A stock warrants [Member]

Series C stock warrants [Member]

Series A stock warrants [Member]

Series C stock warrants [Member]

Series A stock warrants [Member]

Series C stock warrants [Member]

Series A stock warrants [Member]

Series C stock warrants [Member]

Series A stock warrants [Member]

Series C stock warrants [Member]

Series A stock warrants [Member]

Series C stock warrants [Member]

Series A stock warrants [Member]

Beginning Balance at Dec. 31, 2010

$8,357,695

'

'

$740,657

'

'

$60,198

'

'

$4,189

'

'

$2,398,615

'

'

$5,426,701

'

'

($205,220)

'

'

($67,445)

'

'

Total comprehensive income

708,258

'

'

'

'

'

'

'

'

'

'

'

'

'

'

859,479

'

'

-151,221

'

'

'

'

'

Acquisition of Wilmington Trust Corporation - common stock issued

405,557

'

'

'

'

'

2,348

'

'

'

'

'

403,209

'

'

'

'

'

'

'

'

'

'

'

Partial redemption of Series A preferred stock

-370,000

'

'

-370,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Conversion of Series B preferred stock into 433,144 shares of common stock

'

'

'

-26,500

'

'

192

'

'

'

'

'

21,754

'

'

'

'

'

'

'

'

4,554

'

'

Issuance of Series D preferred stock

495,000

'

'

500,000

'

'

'

'

'

'

'

'

-5,000

'

'

'

'

'

'

'

'

'

'

'

Preferred stock cash dividends

-48,203

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-48,203

'

'

'

'

'

'

'

'

Amortization of preferred stock discount

'

'

'

20,428

'

'

'

'

'

'

'

'

'

'

'

-20,428

'

'

'

'

'

'

'

'

Stock-based compensation plans:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Compensation expense, net

43,912

'

'

'

'

'

50

'

'

'

'

'

12,196

'

'

'

'

'

'

'

'

31,666

'

'

Exercises of stock options, net

25,854

'

'

'

'

'

48

'

'

'

'

'

-4,300

'

'

'

'

'

'

'

'

30,106

'

'

Directors' stock plan

1,431

'

'

'

'

'

6

'

'

'

'

'

813

'

'

'

'

'

'

'

'

612

'

'

Deferred compensation plans, net, including dividend equivalents

38

'

'

'

'

'

'

'

'

-117

'

'

-164

'

'

-188

'

'

'

'

'

507

'

'

Other

1,863

'

'

'

'

'

'

'

'

'

'

'

1,863

'

'

'

'

'

'

'

'

'

'

'

Common stock cash dividends - $2.80 per share

-350,196

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-350,196

'

'

'

'

'

'

'

'

Ending balance at Dec. 31, 2011

9,271,209

'

'

864,585

'

'

62,842

'

'

4,072

'

'

2,828,986

'

'

5,867,165

'

'

-356,441

'

'

'

'

'

Total comprehensive income

1,145,675

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,029,498

'

'

116,177

'

'

'

'

'

Preferred stock cash dividends

-53,450

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-53,450

'

'

'

'

'

'

'

'

Amortization of preferred stock discount

'

'

'

7,915

'

'

'

'

'

'

'

'

'

'

'

-7,915

'

'

'

'

'

'

'

'

Stock-based compensation plans:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Compensation expense, net

48,166

'

'

'

'

'

229

'

'

'

'

'

47,937

'

'

'

'

'

'

'

'

'

'

'

Exercises of stock options, net

135,945

'

'

'

'

'

928

'

'

'

'

'

135,017

'

'

'

'

'

'

'

'

'

'

'

Stock purchase plan

10,117

'

'

'

'

'

75

'

'

'

'

'

10,042

'

'

'

'

'

'

'

'

'

'

'

Directors' stock plan

1,480

'

'

'

'

'

9

'

'

'

'

'

1,471

'

'

'

'

'

'

'

'

'

'

'

Deferred compensation plans, net, including dividend equivalents

-161

'

'

'

'

'

5

'

'

-599

'

'

593

'

'

-160

'

'

'

'

'

'

'

'

Other

1,474

'

'

'

'

'

'

'

'

'

'

'

1,474

'

'

'

'

'

'

'

'

'

'

'

Common stock cash dividends - $2.80 per share

-357,862

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-357,862

'

'

'

'

'

'

'

'

Ending balance at Dec. 31, 2012

10,202,593

'

'

872,500

'

'

64,088

'

'

3,473

'

'

3,025,520

'

'

6,477,276

'

'

-240,264

'

'

'

'

'

Total comprehensive income

1,314,585

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,138,480

'

'

176,105

'

'

'

'

'

Preferred stock cash dividends

-53,450

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-53,450

'

'

'

'

'

'

'

'

Amortization of preferred stock discount

'

'

'

9,000

'

'

'

'

'

'

'

'

'

'

'

-9,000

'

'

'

'

'

'

'

'

Stock-based compensation plans:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Exercise of stock warrants into common stock

'

'

'

'

'

'

'

93

13

'

'

'

'

-93

-13

'

'

'

'

'

'

'

'

'

Compensation expense, net

38,027

'

'

'

'

'

137

'

'

'

'

'

37,890

'

'

'

'

'

'

'

'

'

'

'

Exercises of stock options, net

164,805

'

'

'

'

'

914

'

'

'

'

'

163,891

'

'

'

'

'

'

'

'

'

'

'

Directors' stock plan

1,644

'

'

'

'

'

8

'

'

'

'

'

1,636

'

'

'

'

'

'

'

'

'

'

'

Deferred compensation plans, net, including dividend equivalents

-109

'

'

'

'

'

5

'

'

-558

'

'

575

'

'

-131

'

'

'

'

'

'

'

'

Other

2,608

'

'

'

'

'

'

'

'

'

'

'

2,608

'

'

'

'

'

'

'

'

'

'

'

Common stock cash dividends - $2.80 per share

-365,171

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-365,171

'

'

'

'

'

'

'

'

Ending balance at Dec. 31, 2013

$11,305,532

'

'

$881,500

'

'

$65,258

'

'

$2,915

'

'

$3,232,014

'

'

$7,188,004

'

'

($64,159)

'

'

'

'

'

Consolidated_Statement_of_Chan1

Consolidated Statement of Changes In Shareholders' Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Common stock [Member]	'	'	'
Shares of common stock issued upon conversion of Series B preferred stock	'	'	433,144
Retained earnings [Member]	'	'	'
Common stock per share dividend amount	$2.80	$2.80	$2.80
Series C stock warrants [Member] | Common stock [Member]	'	'	'
Number of warrants exercised into shares	407,542	'	'
Number of shares converted from warrants	186,589	'	'
Series A stock warrants [Member] | Common stock [Member]	'	'	'
Number of warrants exercised into shares	69,127	'	'
Number of shares converted from warrants	25,427	'	'

Significant_accounting_policie

Significant accounting policies	12 Months Ended
	Dec. 31, 2013
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, Pennsylvania, Maryland, Delaware, Virginia and the District of Columbia and on small and medium-size businesses based in those areas. Banking services are also provided in West Virginia and New Jersey, while certain subsidiaries also conduct activities in other areas.
	The accounting and reporting policies of M&T and subsidiaries (“the Company”) conform to generally accepted accounting principles (“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 more 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.
	The cost basis of individual securities is written down through a charge to earnings when declines in value below amortized cost 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. The cost basis of individual equity securities is written down to estimated fair value through a charge to earnings when declines in value below cost are considered to be other than temporary. 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 recorded at fair value with no carry-over of an acquired entity’s previously established allowance for credit losses. 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.
	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.
	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 acquired loans 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. 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 market 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 that is expected to vest, 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.
	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.
	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.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2013
Business Combinations [Abstract]	'
Acquisitions	'
	2.    Acquisitions
	On August 27, 2012, M&T announced that it had entered into a definitive agreement with Hudson City Bancorp, Inc. (“Hudson City”), headquartered in Paramus, New Jersey, under which Hudson City will be acquired by M&T. Pursuant to the terms of the agreement, Hudson City shareholders will receive consideration for each common share of Hudson City in an amount valued at .08403 of an M&T share in the form of either M&T common stock or cash, based on the election of each Hudson City shareholder, subject to proration as specified in the merger agreement (which provides for an aggregate split of total consideration of 60% common stock of M&T and 40% cash). As of December 31, 2013 total consideration to be paid was valued at approximately $5.0 billion.
	At December 31, 2013, Hudson City had $38.6 billion of assets, including $24.2 billion of loans and $9.3 billion of investment securities, and $33.9 billion of liabilities, including $21.5 billion of deposits. The merger has received the approval of the common shareholders of M&T and Hudson City. However, the merger is subject to a number of other conditions, including regulatory approvals.
	On June 17, 2013, M&T and Manufacturers and Traders Trust Company (“M&T Bank”), M&T’s principal banking subsidiary, entered into a written agreement with the Federal Reserve Bank of New York (“Federal Reserve Bank”). Under the terms of the agreement, M&T and M&T Bank are required to submit to the Federal Reserve Bank a revised compliance risk management program designed to ensure compliance with the Bank Secrecy Act and anti-money-laundering laws and regulations and to take certain other steps to enhance their compliance practices. The Company has commenced a major initiative, including the hiring of outside consulting firms, intended to fully address the Federal Reserve Bank’s concerns. In view of the timeframe required to implement this initiative, demonstrate its efficacy to the satisfaction of the Federal Reserve Bank and otherwise meet any other regulatory requirements that may be imposed in connection with these matters, M&T and Hudson City extended the date after which either party may elect to terminate the merger agreement if the merger has not yet been completed to December 31, 2014. Nevertheless, there can be no assurances that the merger will be completed by that date.
	On May 16, 2011, M&T acquired all of the outstanding common stock of Wilmington Trust Corporation (“Wilmington Trust”), headquartered in Wilmington, Delaware, in a stock-for-stock transaction. Wilmington Trust operated 55 banking offices in Delaware and Pennsylvania at the date of acquisition. The results of operations acquired in the Wilmington Trust transaction have been included in the Company’s financial results since May 16, 2011. Wilmington Trust shareholders received .051372 shares of M&T common stock in exchange for each share of Wilmington Trust common stock, resulting in M&T issuing a total of 4,694,486 common shares with an acquisition date fair value of $406 million.
	The Wilmington Trust transaction has been 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 $10.8 billion, including $6.4 billion of loans and leases (including approximately $3.2 billion of commercial real estate loans, $1.4 billion of commercial loans and leases, $1.1 billion of consumer loans and $680 million of residential real estate loans). Liabilities assumed aggregated $10.0 billion, including $8.9 billion of deposits. The common stock issued in the transaction added $406 million to M&T’s common shareholders’ equity. Immediately prior to the closing of the Wilmington Trust transaction, M&T redeemed the $330 million of preferred stock issued by Wilmington Trust as part of the Troubled Asset Relief Program — Capital Purchase Program (“TARP”) of the U.S. Department of Treasury (“U.S. Treasury”). In connection with the acquisition, the Company recorded $112 million of core deposit and other intangible assets. The core deposit and other intangible assets are generally being amortized over periods of 5 to 7 years using accelerated methods. There was no goodwill recorded as a result of the transaction, however, a non-taxable gain of $65 million was realized, which represented the excess of the fair value of assets acquired less liabilities assumed over consideration exchanged. The acquisition of Wilmington Trust added to M&T’s market-leading position in the Mid-Atlantic region by giving M&T the leading deposit market share in Delaware.
	The following table discloses the impact of Wilmington Trust (excluding the impact of the merger-related gain and expenses) since the acquisition on May 16, 2011 through the end of 2011. The table also presents certain pro forma information as if Wilmington Trust had been included in the Company’s consolidated financial results for all of 2011. These results combine the historical results of Wilmington Trust 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 indicative of what would have occurred had the acquisition taken place earlier than indicated. In particular, no adjustments have been made to eliminate the amount of Wilmington Trust’s provision for credit losses of $42 million in 2011 or the impact of other-than-temporary impairment losses recognized by Wilmington Trust of $5 million in 2011 that may not have been necessary had the acquired loans and investment securities been recorded at fair value as of the beginning of 2011. Expenses related to systems conversions and other costs of integration of $84 million and the $65 million gain recorded in connection with the acquisition are included in the 2011 pro forma results. Additionally, the Company has achieved further operating cost savings and other business synergies as a result of the acquisition which are not reflected in the pro forma amounts that follow.
			Actual Since		Pro Forma
			Acquisition		Year Ended
			Through		December 31, 2011
			December 31, 2011
			(In thousands)
	Total revenues(a)		$	380,945	$	4,202,109
	Net income			18,586		808,696
	(a)	Represents net interest income plus other income.
	The Company incurred merger-related expenses in 2013 associated with the pending Hudson City acquisition and in 2012 and 2011 predominantly associated with the Wilmington Trust acquisition related to actual or planned 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 the actual or planned conversion of systems and/or integration of operations; costs related to branch and office consolidations; 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 employees of acquired entities) and incentive compensation costs; travel costs; and printing, postage, supplies and other costs of planning for or completing the transactions and commencing operations in new markets and offices.
	A summary of merger-related expenses included in the consolidated statement of income for the years ended December 31, 2013, 2012 and 2011 follows:
			2013		2012		2011
			(In thousands)
	Salaries and employee benefits		$	836	$	4,997	$	16,131
	Equipment and net occupancy			690		15		412
	Printing, postage and supplies			1,825		—		2,663
	Other costs of operations			9,013		4,867		64,481
			$	12,364	$	9,879	$	83,687

Investment_securities

Investment securities	12 Months Ended
	Dec. 31, 2013
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			Gross			Gross			Estimated
		Cost			Unrealized			Unrealized			Fair Value
					Gains			Losses
		(In thousands)
	December 31, 2013
	Investment securities available for sale:
	U.S. Treasury and federal agencies	$	37,396		$	382		$	2		$	37,776
	Obligations of states and political subdivisions		10,484			333			6			10,811
	Mortgage-backed securities:
	Government issued or guaranteed		4,123,435			61,001			19,350			4,165,086
	Privately issued		1,468			387			5			1,850
	Collateralized debt obligations		42,274			21,666			857			63,083
	Other debt securities		137,828			1,722			19,465			120,085
	Equity securities		91,480			41,842			227			133,095
			4,444,365			127,333			39,912			4,531,786
	Investment securities held to maturity:
	Obligations of states and political subdivisions		169,684			3,744			135			173,293
	Mortgage-backed securities:
	Government issued or guaranteed		3,567,905			16,160			65,149			3,518,916
	Privately issued		219,628			—			60,623			159,005
	Other debt securities		8,913			—			—			8,913
			3,966,130			19,904			125,907			3,860,127
	Other securities		298,581			—			—			298,581
	Total	$	8,709,076		$	147,237		$	165,819		$	8,690,494
	December 31, 2012
	Investment securities available for sale:
	U.S. Treasury and federal agencies	$	38,422		$	922		$	—		$	39,344
	Obligations of states and political subdivisions		20,375			534			8			20,901
	Mortgage-backed securities:
	Government issued or guaranteed		3,163,210			208,060			229			3,371,041
	Privately issued		1,142,287			7,272			125,673			1,023,886
	Collateralized debt obligations		43,228			19,663			1,022			61,869
	Other debt securities		136,603			2,247			26,900			111,950
	Equity securities		98,945			14,921			3,420			110,446
			4,643,070			253,619			157,252			4,739,437
	Investment securities held to maturity:
	Obligations of states and political subdivisions		182,103			7,647			27			189,723
	Mortgage-backed securities:
	Government issued or guaranteed		597,340			31,727			—			629,067
	Privately issued		242,378			160			94,900			147,638
	Other debt securities		10,455			—			—			10,455
			1,032,276			39,534			94,927			976,883
	Other securities		302,648			—			—			302,648
	Total	$	5,977,994		$	293,153		$	252,179		$	6,018,968
	No investment in securities of a single non-U.S. Government or government agency issuer exceeded ten percent of shareholders’ equity at December 31, 2013.
	As of December 31, 2013, the latest available investment ratings of all obligations of states and political subdivisions, privately issued mortgage-backed securities, collateralized debt obligations and other debt securities were:
		Amortized			Estimated			Average Credit Rating of Fair Value Amount
		Cost			Fair Value			A or Better			BBB			BB		B or Less		Not Rated
		(In thousands)
	Obligations of states and political subdivisions	$	180,168		$	184,104		$	152,704		$	6,359		$	200	$	—	$	24,841
	Privately issued mortgage-backed     securities		221,096			160,855			56,731			—			—		104,000		124
	Collateralized debt obligations		42,274			63,083			11,005			3,684			8,904		39,490		—
	Other debt securities		146,741			128,998			12,073			56,481			28,966		21,300		10,178
	Total	$	590,279		$	537,040		$	232,513		$	66,524		$	38,070	$	164,790	$	35,143
	The amortized cost and estimated fair value of collateralized mortgage obligations included in mortgage-backed securities were as follows:
		December 31
		2013			2012
		(In thousands)
	Collateralized mortgage obligations:
	Amortized cost	$	231,040		$	1,414,691
	Estimated fair value		171,100			1,202,243
Gross realized gains from sales of investment securities were $116,490,000 in 2013. During 2013, the Company sold its holdings of Visa Class B shares for a gain of $89,545,000 and its holdings of MasterCard Class B shares for a gain of $13,208,000. Gross realized losses on investment securities were $60,033,000 in 2013. The Company sold substantially all of its privately issued mortgage-backed securities held in the available-for-sale investment securities portfolio during 2013. In total, $1.0 billion of such securities were sold for a net loss of approximately $46,302,000. In 2011, gross realized gains from sales of investment securities were $150,223,000 and gross realized losses were $36,000. During 2011, the Company sold residential mortgage-backed securities guaranteed by the Federal National Mortgage Association (“Fannie Mae”) and the Federal Home Loan Mortgage Corporation (“Freddie Mac”) having an aggregate amortized cost of approximately $1.5 billion which resulted in a gain of $104 million. The Company also sold trust preferred securities and collateralized debt securities during 2011 having an aggregate amortized cost of $136 million and $100 million, respectively, which resulted in gains of $25 million and $20 million, respectively. Gross realized gains and losses from sales of investment securities were not significant in 2012.
The Company recognized $10 million, $48 million and $77 million of pre-tax other-than-temporary impairment losses related to privately issued mortgage-backed securities in 2013, 2012 and 2011, respectively. The impairment charges were recognized in light of deterioration of real estate values and a rise in delinquencies and charge-offs of underlying mortgage loans collateralizing those securities. The other-than-temporary impairment losses represented management’s estimate of credit losses inherent in the debt securities considering projected cash flows using assumptions of delinquency rates, loss severities, and other estimates of future collateral performance.
Changes in credit losses during 2013, 2012 and 2011 associated with debt securities for which other-than-temporary impairment losses have been recognized in earnings follows:
	Year Ended December 31
	2013			2012			2011
	(In thousands)
Estimated credit losses — beginning balance	$	197,809		$	285,399		$	327,912
Additions for credit losses not previously recognized		9,800			47,822			77,035
Reductions for increases in cash flows		—			—			(5,111	)
Reductions for realized losses		(207,441	)		(135,412	)		(114,437	)
Estimated credit losses — ending balance	$	168		$	197,809		$	285,399
At December 31, 2013, the amortized cost and estimated fair value of debt securities by contractual maturity were as follows:
	Amortized			Estimated
	Cost			Fair Value
	(In thousands)
Debt securities available for sale:
Due in one year or less	$	29,839		$	30,036
Due after one year through five years		16,005			16,617
Due after five years through ten years		7,718			8,015
Due after ten years		174,420			177,087
		227,982			231,755
Mortgage-backed securities available for sale		4,124,903			4,166,936
	$	4,352,885		$	4,398,691
Debt securities held to maturity:
Due in one year or less	$	19,485		$	19,606
Due after one year through five years		68,713			70,618
Due after five years through ten years		81,486			83,069
Due after ten years		8,913			8,913
		178,597			182,206
Mortgage-backed securities held to maturity		3,787,533			3,677,921
	$	3,966,130		$	3,860,127
A summary of investment securities that as of December 31, 2013 and 2012 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			Fair Value			Unrealized
				Losses						Losses
	(In thousands)
December 31, 2013
Investment securities available for sale:
U.S. Treasury and federal agencies	$	745		$	(2	)	$	—		$	—
Obligations of states and political subdivisions		—			—			558			(6	)
Mortgage-backed securities:
Government issued or guaranteed		1,697,094			(19,225	)		5,815			(125	)
Privately issued		—			—			98			(5	)
Collateralized debt obligations		—			—			6,257			(857	)
Other debt securities		1,428			(4	)		103,602			(19,461	)
Equity securities		159			(227	)		—			—
		1,699,426			(19,458	)		116,330			(20,454	)
Investment securities held to maturity:
Obligations of states and political subdivisions		13,517			(120	)		1,558			(15	)
Mortgage-backed securities:
Government issued or guaranteed		2,629,950			(65,149	)		—			—
Privately issued		—			—			159,005			(60,623	)
		2,643,467			(65,269	)		160,563			(60,638	)
Total	$	4,342,893		$	(84,727	)	$	276,893		$	(81,092	)
December 31, 2012
Investment securities available for sale:
Obligations of states and political subdivisions	$	166		$	(1	)	$	683		$	(7	)
Mortgage-backed securities:
Government issued or guaranteed		12,107			(65	)		8,804			(164	)
Privately issued		121,487			(692	)		774,328			(124,981	)
Collateralized debt obligations		—			—			6,043			(1,022	)
Other debt securities		—			—			95,685			(26,900	)
Equity securities		5,535			(1,295	)		2,956			(2,125	)
		139,295			(2,053	)		888,499			(155,199	)
Investment securities held to maturity:
Obligations of states and political subdivisions		1,026			(5	)		3,558			(22	)
Privately issued mortgage-backed securities		—			—			147,273			(94,900	)
		1,026			(5	)		150,831			(94,922	)
Total	$	140,321		$	(2,058	)	$	1,039,330		$	(250,121	)
The Company owned 468 individual investment securities with aggregate gross unrealized losses of $166 million at December 31, 2013. Approximately $61 million of the unrealized losses pertain to privately issued mortgage-backed securities with a cost basis of $220 million. The Company also had $19 million of unrealized losses on available-for-sale trust preferred securities issued by financial institutions having a cost basis of $123 million. Based on a review of each of the securities in the investment securities portfolio at December 31, 2013, the Company concluded that it expected to recover the amortized cost basis of its investment. As of December 31, 2013, 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, 2013, the Company has not identified events or changes in circumstances which may have a significant adverse effect on the fair value of the $299 million of cost method investment securities.
At December 31, 2013, investment securities with a carrying value of $3,902,317,000, including $2,459,296,000 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 $1,696,438,000 at December 31, 2013. 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
	Dec. 31, 2013
Receivables [Abstract]	'
Loans and leases	'
	4.    Loans and leases
	Total loans and leases outstanding were comprised of the following:
			December 31
			2013			2012
			(In thousands)
	Loans
	Commercial, financial, etc.		$	17,477,238		$	16,500,202
	Real estate:
	Residential			8,911,554			11,161,323
	Commercial			21,799,886			22,333,036
	Construction			4,457,650			3,772,413
	Consumer			10,280,527			11,550,274
	Total loans			62,926,855			65,317,248
	Leases
	Commercial			1,398,928			1,472,938
	Total loans and leases			64,325,783			66,790,186
	Less: unearned discount			(252,624	)		(219,229	)
	Total loans and leases, net of unearned discount		$	64,073,159		$	66,570,957
	One-to-four family residential mortgage loans held for sale were $401 million at December 31, 2013 and $1.2 billion at December 31, 2012. Commercial real estate loans held for sale were $68 million at December 31, 2013 and $200 million at December 31, 2012.
	During the second and third quarters of 2013, the Company securitized approximately $1.3 billion of one-to-four family residential real estate loans previously held in the Company’s loan portfolio into guaranteed mortgage-backed securities with the Government National Mortgage Association (“Ginnie Mae”) and recognized gains of $42,382,000. In addition, the Company securitized and sold in September 2013 approximately $1.4 billion of automobile loans held in its loan portfolio, resulting in a gain of $20,683,000.
	As of December 31, 2013, approximately $2.3 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, 2013, 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 $17 million, $28 million and $23 million in 2013, 2012 and 2011, respectively.
	The outstanding principal balance and the carrying amount of acquired loans that were recorded at fair value at the acquisition date that is included in the consolidated balance sheet were as follows:
			December 31
			2013			2012
			(In thousands)
	Outstanding principal balance		$	4,656,811		$	6,705,120
	Carrying amount:
	Commercial, financial, leasing, etc.			580,685			928,107
	Commercial real estate			1,541,368			2,567,050
	Residential real estate			576,473			707,309
	Consumer			1,308,926			1,637,887
			$	4,007,452		$	5,840,353
	Purchased impaired loans included in the table above totaled $331 million at December 31, 2013 and $447 million at December 31, 2012, representing less than 1% of the Company’s assets as of each date. A summary of changes in the accretable yield for acquired loans for the years ended December 31, 2013, 2012 and 2011 follows:
	For Year Ended December 31,		2013						2012						2011
			Purchased			Other			Purchased			Other			Purchased			Other
			Impaired			Acquired			Impaired			Acquired			Impaired			Acquired
			(In thousands)
	Balance at beginning of period		$	42,252		$	638,272		$	30,805		$	807,960		$	9,245		$	447,505
	Additions			—			—			—			—			39,358			648,631
	Interest income			(36,727	)		(247,295	)		(40,551	)		(295,654	)		(26,221	)		(268,315	)
	Reclassifications from nonaccretable balance, net			31,705			149,595			51,998			148,490			8,629			1,800
	Other(a)			—			(1,939	)		—			(22,524	)		(206	)		(21,661	)
	Balance at end of period		$	37,230		$	538,633		$	42,252		$	638,272		$	30,805		$	807,960
	(a)	Other changes in expected cash flows including changes in interest rates and prepayment assumptions.
	A summary of current, past due and nonaccrual loans as of December 31, 2013 and 2012 follows:
									90 Days or More Past
									Due and Accruing
			Current			30-89 Days			Non-			Acquired(a)			Purchased			Nonaccrual			Total
						Past Due			acquired						Impaired(b)
			(In thousands)
	December 31, 2013
	Commercial, financial, leasing, etc.		$	18,489,474		$	77,538		$	4,981		$	6,778		$	15,706		$	110,739		$	18,705,216
	Real estate:
	Commercial			21,236,071			145,749			63,353			35,603			88,034			173,048			21,741,858
	Residential builder and developer			1,025,984			8,486			141			7,930			137,544			96,427			1,276,512
	Other commercial construction			2,986,598			42,234			—			8,031			57,707			35,268			3,129,838
	Residential			7,630,368			295,131			294,649			43,700			29,184			252,805			8,545,837
	Residential Alt-A			283,253			18,009			—			—			—			81,122			382,384
	Consumer:
	Home equity lines and loans			5,972,365			40,537			—			27,754			2,617			78,516			6,121,789
	Automobile			1,314,246			29,144			—			366			—			21,144			1,364,900
	Other			2,726,522			47,830			5,386			—			—			25,087			2,804,825
Total		$	61,664,881		$	704,658		$	368,510		$	130,162		$	330,792		$	874,156		$	64,073,159
December 31, 2012
Commercial, financial, leasing, etc.		$	17,511,052		$	62,479		$	23,490		$	10,587		$	17,437		$	151,908		$	17,776,953
Real estate:
Commercial			21,759,997			118,249			13,111			54,995			132,962			193,859			22,273,173
Residential builder and developer			757,311			35,419			3,258			23,909			187,764			181,865			1,189,526
Other commercial construction			2,379,953			35,274			509			9,572			68,971			36,812			2,531,091
Residential			9,811,956			337,969			313,184			45,124			36,769			249,314			10,794,316
Residential Alt-A			331,021			19,692			—			—			—			95,808			446,521
Consumer:
Home equity lines and loans			6,199,591			40,759			—			20,318			3,211			58,071			6,321,950
Automobile			2,442,502			40,461			—			251			—			25,107			2,508,321
Other			2,661,432			40,599			4,845			1,798			—			20,432			2,729,106
Total		$	63,854,815		$	730,901		$	358,397		$	166,554		$	447,114		$	1,013,176		$	66,570,957
(a)	Acquired loans that were recorded at fair value at acquisition date. This category does not include purchased impaired loans that are presented separately.
(b)	Accruing loans that were impaired at acquisition date and were 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 $62,010,000 in 2013, $69,054,000 in 2012 and $80,278,000 in 2011. The actual amounts included in interest income during 2013, 2012 and 2011 on such loans were $31,987,000, $30,484,000 and $31,301,000, respectively.
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 table below summarizes the Company’s loan modification activities that were considered troubled debt restructurings for the year ended December 31, 2013:
					Recorded Investment						Financial Effects of
											Modification
		Number			Pre-			Post-			Recorded			Interest
					modifica-			modifica-			Investment			(b)
					tion			tion			(a)
		(Dollars in thousands)
Commercial, financial, leasing, etc.
Principal deferral			79		$	16,389		$	16,002		$	(387	)	$	—
Interest rate reduction			1			104			335			231			(54	)
Other			4			50,433			50,924			491			—
Combination of concession types			11			6,229			5,578			(651	)		(458	)
Real estate:
Commercial
Principal deferral			27			40,639			40,464			(175	)		—
Other			2			449			475			26			—
Combination of concession types			9			2,649			3,040			391			(250	)
Residential builder and developer
Principal deferral			18			21,423			20,577			(846	)		—
Other			1			4,039			3,888			(151	)		—
Combination of concession types			3			15,580			15,514			(66	)		(535	)
Other commercial construction
Principal deferral			3			590			521			(69	)		—
Residential
Principal deferral			32			3,556			3,821			265			—
Other			1			195			195			—			—
Combination of concession types			61			73,940			70,854			(3,086	)		(924	)
Residential Alt-A
Principal deferral			10			1,900			1,880			(20	)		—
Combination of concession types			19			2,826			3,148			322			(790	)
Consumer:
Home equity lines and loans
Principal deferral			10			859			861			2			—
Interest rate reduction			1			99			99			—			(8	)
Other			1			106			106			—			—
Combination of concession types			28			2,190			2,190			—			(270	)
Automobile
Principal deferral			460			6,148			6,148			—			—
Interest rate reduction			15			235			235			—			(22	)
Other			78			339			339			—			—
Combination of concession types			225			2,552			2,552			—			(191	)
Other
Principal deferral			36			332			332			—			—
Interest rate reduction			1			12			12			—			(2	)
Other			2			14			14			—			—
Combination of concession types			120			4,248			4,248			—			(1,187	)
Total			1,258		$	258,075		$	254,352		$	(3,723	)	$	(4,691	)
(a)	Financial effects impacting the recorded investment included principal payments or advances, charge-offs and capitalized escrow arrearages.
(b)	Represents the present value of interest rate concessions discounted at the effective rate of the original loan.
The table below summarizes the Company’s loan modification activities that were considered troubled debt restructurings for the year ended December 31, 2012:
					Recorded Investment						Financial Effects of
											Modification
		Number			Pre-			Post-			Recorded			Interest
					modifica-			modifica-			Investment			(b)
					tion			tion			(a)
		(Dollars in thousands)
Commercial, financial, leasing, etc.
Principal deferral			61		$	23,888		$	22,456		$	(1,432	)	$	—
Other			3			2,967			3,052			85			—
Combination of concession types			5			628			740			112			(102	)
Real estate:
Commercial
Principal deferral			24			22,855			23,059			204			—
Interest rate reduction			2			665			708			43			(129	)
Combination of concession types			7			1,637			1,656			19			(351	)
Residential builder and developer
Principal deferral			23			36,868			34,740			(2,128	)		—
Combination of concession types			7			37,602			36,148			(1,454	)		—
Other commercial construction
Principal deferral			6			81,062			79,312			(1,750	)		—
Residential
Principal deferral			36			4,643			4,808			165			—
Interest rate reduction			1			109			109			—			(20	)
Combination of concession types			62			12,886			13,146			260			(657	)
Residential Alt-A
Principal deferral			7			968			989			21			—
Combination of concession types			38			8,525			8,717			192			(159	)
Consumer:
Home equity lines and loans
Principal deferral			15			1,285			1,285			—			—
Interest rate reduction			1			144			144			—			(6	)
Combination of concession types			29			2,332			2,332			—			(368	)
Automobile
Principal deferral			618			8,347			8,347			—			—
Interest rate reduction			22			328			328			—			(24	)
Other			67			300			300			—			—
Combination of concession types			375			5,857			5,857			—			(684	)
Other
Principal deferral			80			1,201			1,201			—			—
Interest rate reduction			22			515			515			—			(85	)
Other			13			54			54			—			—
Combination of concession types			84			1,015			1,015			—			(268	)
Total			1,608		$	256,681		$	251,018		$	(5,663	)	$	(2,853	)
(a)	Financial effects impacting the recorded investment included principal payments or advances, charge-offs and capitalized escrow arrearages.
(b)	Represents the present value of interest rate concessions discounted at the effective rate of the original loan.
The table below summarizes the Company’s loan modification activities that were considered troubled debt restructurings for the year ended December 31, 2011:
					Recorded Investment						Financial Effects of
											Modification
		Number			Pre-			Post-			Recorded			Interest
					modifica-			modifica-			Investment			(b)
					tion			tion			(a)
		(Dollars in thousands)
Commercial, financial, leasing, etc.
Principal deferral			53		$	10,703		$	10,778		$	75		$	—
Combination of concession types			3			2,049			2,046			(3	)		(654	)
Real estate:
Commercial
Principal deferral			29			16,804			16,704			(100	)		—
Combination of concession types			3			15,778			15,777			(1	)		(1,463	)
Residential builder and developer
Principal deferral			9			33,208			26,811			(6,397	)		—
Other			6			118,114			110,156			(7,958	)		—
Combination of concession types			5			2,540			2,561			21			—
Other commercial construction
Principal deferral			3			8,436			8,553			117			—
Combination of concession types			3			65,813			60,973			(4,840	)		—
Residential
Principal deferral			37			8,175			8,235			60			—
Interest rate reduction			14			1,926			1,991			65			(318	)
Combination of concession types			111			19,508			19,934			426			(1,559	)
Residential Alt-A
Principal deferral			3			800			835			35			—
Combination of concession types			34			6,813			6,978			165			(889	)
Consumer:
Home equity lines and loans
Principal deferral			3			259			259			—			—
Other			3			86			86			—			—
Combination of concession types			26			2,156			2,158			2			(444	)
Automobile
Principal deferral			746			10,053			10,053			—			—
Interest rate reduction			17			183			183			—			(13	)
Other			111			739			739			—			—
Combination of concession types			431			6,703			6,703			—			(808	)
Other
Principal deferral			23			400			400			—			—
Interest rate reduction			1			8			8			—			(1	)
Other			4			103			103			—			—
Combination of concession types			102			803			803			—			(189	)
Total			1,780		$	332,160		$	313,827		$	(18,333	)	$	(6,338	)
(a)	Financial effects impacting the recorded investment included principal payments or advances, charge-offs and capitalized escrow arrearages.
(b)	Represents the present value of interest rate concessions discounted at the effective rate of the original loan.
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, 2013, 2012 and 2011 and for which there was a subsequent payment default during the respective period 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 $120,000, amounted to $135,512,000 and $99,532,000 at December 31, 2013 and 2012, respectively. During 2013, new borrowings by such persons amounted to $44,799,000 (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 retirements) were $8,819,000.
At December 31, 2013, approximately $8.9 billion of commercial loans and leases, $9.6 billion of commercial real estate loans, $5.3 billion of one-to-four family residential real estate loans, $4.1 billion of home equity loans and lines of credit and $2.1 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
		2013			2012
		(In thousands)
Commercial leases:
Direct financings:
Lease payments receivable		$	1,052,214		$	1,106,434
Estimated residual value of leased assets			85,595			96,468
Unearned income			(114,101	)		(134,428	)
Investment in direct financings			1,023,708			1,068,474
Leveraged leases:
Lease payments receivable			127,821			132,466
Estimated residual value of leased assets			133,298			137,570
Unearned income			(47,188	)		(50,378	)
Investment in leveraged leases			213,931			219,658
Total investment in leases.		$	1,237,639		$	1,288,132
Deferred taxes payable arising from leveraged leases		$	172,296		$	172,026
Included within the estimated residual value of leased assets at December 31, 2013 and 2012 were $54 million and $61 million, respectively, in residual value associated with direct financing leases that are guaranteed by the lessees or others.
At December 31, 2013, the minimum future lease payments to be received from lease financings were as follows:
		(In thousands)
Year ending December 31:
2014		$	268,434
2015			247,620
2016			193,920
2017			122,781
2018			85,341
Later years			261,939
		$	1,180,035

Allowance_for_credit_losses

Allowance for credit losses	12 Months Ended
	Dec. 31, 2013
Receivables [Abstract]	'
Allowance for credit losses	'
	5.    Allowance for credit losses
	Changes in the allowance for credit losses for the years ended December 31, 2013, 2012 and 2011 were as follows:
		Commercial,			Real Estate
		Financial,
	2013	Leasing, etc.			Commercial			Residential			Consumer			Unallocated		Total
		(In thousands)
	Beginning balance	$	246,759		$	337,101		$	88,807		$	179,418		$	73,775	$	925,860
	Provision for credit losses		124,180			275			3,149			56,156			1,240		185,000
	Allowance related to loans sold or securitized		—			—			—			(11,000	)		—		(11,000	)
	Net charge-offs
	Charge-offs		(109,329	)		(34,595	)		(23,621	)		(85,965	)		—		(253,510	)
	Recoveries		11,773			22,197			10,321			26,035			—		70,326
	Net charge-offs		(97,556	)		(12,398	)		(13,300	)		(59,930	)		—		(183,184	)
	Ending balance	$	273,383		$	324,978		$	78,656		$	164,644		$	75,015	$	916,676
	2012
	Beginning balance	$	234,022		$	367,637		$	91,915		$	143,121		$	71,595	$	908,290
	Provision for credit losses		42,510			5,211			34,864			119,235			2,180		204,000
	Net charge-offs
	Charge-offs		(41,148	)		(41,945	)		(44,314	)		(103,348	)		—		(230,755	)
	Recoveries		11,375			6,198			6,342			20,410			—		44,325
	Net charge-offs		(29,773	)		(35,747	)		(37,972	)		(82,938	)		—		(186,430	)
	Ending balance	$	246,759		$	337,101		$	88,807		$	179,418		$	73,775	$	925,860
	2011
	Beginning balance	$	212,579		$	400,562		$	86,351		$	133,067		$	70,382	$	902,941
	Provision for credit losses		66,240			44,404			57,081			101,062			1,213		270,000
	Net charge-offs
	Charge-offs		(55,021	)		(86,869	)		(58,351	)		(109,246	)		—		(309,487	)
	Recoveries		10,224			9,540			6,834			18,238			—		44,836
	Net charge-offs		(44,797	)		(77,329	)		(51,517	)		(91,008	)		—		(264,651	)
	Ending balance	$	234,022		$	367,637		$	91,915		$	143,121		$	71,595	$	908,290
	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 detailed or intensified 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 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 officers are responsible for continually assigning grades to these loans based on standards outlined in the Company’s Credit Policy. Internal loan grades are also monitored by the Company’s loan review department to ensure consistency and strict adherence to the prescribed standards. 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. As updated appraisals are obtained on individual loans or other events in the market place indicate that collateral values have significantly changed, individual loan grades are adjusted as appropriate. Changes in other factors cited may also lead to loan grade changes at any time. Except for consumer and residential real estate loans that are considered smaller balance homogenous loans and acquired loans that are evaluated on an aggregated basis, 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. Modified loans, including smaller balance homogenous loans, that are considered to be troubled debt restructurings 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.
	The following tables provide information with respect to loans and leases that were considered impaired as of December 31, 2013 and 2012 and for the years ended December 31, 2013, 2012 and 2011.
		December 31, 2013									December 31, 2012
		Recorded			Unpaid			Related			Recorded			Unpaid		Related
		Investment			Principal			Allowance			Investment			Principal		Allowance
					Balance									Balance
		(In thousands)
	With an allowance recorded:
	Commercial, financial, leasing, etc.	$	90,293		$	112,092		$	24,614		$	127,282		$	149,534	$	33,829
	Real estate:
	Commercial		113,570			132,325			19,520			121,542			143,846		23,641
	Residential builder and developer		33,311			55,122			4,379			115,306			216,218		25,661
	Other commercial construction		86,260			90,515			4,022			73,544			76,869		6,836
	Residential		96,508			114,521			7,146			103,451			121,819		3,521
	Residential Alt-A		111,911			124,528			14,000			128,891			141,940		17,000
	Consumer:
	Home equity lines and loans		13,672			14,796			3,312			12,360			13,567		2,254
	Automobile		40,441			40,441			11,074			49,210			49,210		14,273
	Other		17,660			17,660			4,541			14,408			14,408		5,667
			603,626			702,000			92,608			745,994			927,411		132,682
	With no related allowance recorded:
	Commercial, financial, leasing, etc.		28,093			33,095			—			32,631			42,199		—
	Real estate:
	Commercial		65,271			84,333			—			78,380			100,337		—
	Residential builder and developer		72,366			104,768			—			74,307			105,438		—
	Other commercial construction		7,369			11,493			—			23,018			23,532		—
	Residential		84,144			95,358			—			86,342			96,448		—
	Residential Alt-A		28,357			52,211			—			31,354			58,768		—
			285,600			381,258			—			326,032			426,722		—
	Total:
	Commercial, financial, leasing, etc.		118,386			145,187			24,614			159,913			191,733		33,829
	Real estate:
Commercial		178,841			216,658			19,520			199,922			244,183		23,641
Residential builder and developer		105,677			159,890			4,379			189,613			321,656		25,661
Other commercial construction		93,629			102,008			4,022			96,562			100,401		6,836
Residential		180,652			209,879			7,146			189,793			218,267		3,521
Residential Alt-A		140,268			176,739			14,000			160,245			200,708		17,000
Consumer:
Home equity lines and loans		13,672			14,796			3,312			12,360			13,567		2,254
Automobile		40,441			40,441			11,074			49,210			49,210		14,273
Other		17,660			17,660			4,541			14,408			14,408		5,667
Total	$	889,226		$	1,083,258		$	92,608		$	1,072,026		$	1,354,133	$	132,682
	Year Ended									Year Ended
	December 31, 2013									December 31, 2012
	Average			Interest Income						Average			Interest Income
	Recorded			Recognized						Recorded			Recognized
	Investment			Total			Cash			Investment			Total		Cash
							Basis								Basis
	(In thousands)
Commercial, financial, leasing, etc.	$	155,188		$	7,197		$	7,197		$	151,314		$	2,938	$	2,938
Real estate:
Commercial		197,533			4,852			4,852			185,171			2,834		2,834
Residential builder and developer		147,288			1,043			796			249,191			1,563		1,102
Other commercial construction		96,475			5,248			5,248			99,672			5,020		5,020
Residential		183,059			6,203			4,111			132,888			5,284		3,300
Residential Alt-A		149,461			6,784			2,341			171,546			7,175		2,226
Consumer:
Home equity lines and loans		12,811			683			183			11,322			663		179
Automobile		44,116			2,916			515			51,650			3,470		724
Other		15,710			634			208			11,028			472		197
Total	$	1,001,641		$	35,560		$	25,451		$	1,063,782		$	29,419	$	18,520
	Year Ended
	December 31, 2011
				Interest Income
				Recognized
	Average			Total			Cash
	Recorded						Basis
	Investment
	(In thousands)
Commercial, financial, leasing, etc.	$	163,485		$	3,306		$	3,278
Real estate:
Commercial		189,837			2,060			1,985
Residential builder and developer		317,296			1,948			860
Other commercial construction		105,947			926			684
Residential		99,107			4,271			2,286
Residential Alt-A		196,161			7,713			1,965
Consumer:
Home equity lines and loans		11,428			681			106
Automobile		56,862			3,850			1,060
Other		5,006			273			89
Total	$	1,145,129		$	25,028		$	12,313
In accordance with the previously described policies, the Company utilizes a loan grading system that is applied to all commercial loans and commercial real estate loans. Loan grades are utilized to differentiate risk within the portfolio and consider the expectations of default for each loan. 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. All larger balance criticized commercial loans and commercial real estate loans are individually reviewed by centralized loan review personnel each quarter to determine the appropriateness of the assigned loan grade, including whether the loan should be reported as accruing or nonaccruing. Smaller balance criticized loans are analyzed by business line risk management areas to ensure proper loan grade classification. 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,			Commercial			Residential			Other
	Financial,						Builder and			Commercial
	Leasing, etc						Developer			Construction
	(In thousands)
December 31, 2013
Pass	$	17,894,592		$	20,972,257		$	1,107,144		$	3,040,106
Criticized accrual		699,885			596,553			72,941			54,464
Criticized nonaccrual		110,739			173,048			96,427			35,268
Total	$	18,705,216		$	21,741,858		$	1,276,512		$	3,129,838
December 31, 2012
Pass	$	16,889,753		$	21,275,182		$	922,141		$	2,307,436
Criticized accrual		735,292			804,132			85,520			186,843
Criticized nonaccrual		151,908			193,859			181,865			36,812
Total	$	17,776,953		$	22,273,173		$	1,189,526		$	2,531,091
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 the original balance 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 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. The determination of the allocated portion of the allowance for credit losses is very subjective. Given that 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,			Real Estate
	Financial,
	Leasing, etc.			Commercial			Residential			Consumer			Total
	(In thousands)
December 31, 2013
Individually evaluated for impairment	$	24,614		$	27,563		$	21,127		$	18,927		$	92,231
Collectively evaluated for impairment		246,096			296,781			55,864			144,210			742,951
Purchased impaired		2,673			634			1,665			1,507			6,479
Allocated	$	273,383		$	324,978		$	78,656		$	164,644			841,661
Unallocated														75,015
Total													$	916,676
December 31, 2012
Individually evaluated for impairment	$	33,669		$	55,291		$	20,502		$	22,194		$	131,656
Collectively evaluated for impairment		212,930			280,789			66,684			156,661			717,064
Purchased impaired		160			1,021			1,621			563			3,365
Allocated	$	246,759		$	337,101		$	88,807		$	179,418			852,085
Unallocated														73,775
Total													$	925,860
The recorded investment in loans and leases summarized on the basis of the Company’s impairment methodology was as follows:
	Commercial,			Real Estate
	Financial,
	Leasing, etc.			Commercial			Residential			Consumer			Total
	(In thousands)
December 31, 2013
Individually evaluated for impairment	$	118,386		$	376,339		$	320,360		$	71,773		$	886,858
Collectively evaluated for impairment		18,571,124			25,488,584			8,578,677			10,217,124			62,855,509
Purchased impaired		15,706			283,285			29,184			2,617			330,792
Total	$	18,705,216		$	26,148,208		$	8,928,221		$	10,291,514		$	64,073,159
December 31, 2012
Individually evaluated for impairment	$	159,761		$	480,335		$	349,477		$	75,978		$	1,065,551
Collectively evaluated for impairment		17,599,755			25,123,758			10,854,591			11,480,188			65,058,292
Purchased impaired		17,437			389,697			36,769			3,211			447,114
Total	$	17,776,953		$	25,993,790		$	11,240,837		$	11,559,377		$	66,570,957

Premises_and_equipment

Premises and equipment	12 Months Ended
	Dec. 31, 2013
Property Plant And Equipment [Abstract]	'
Premises and equipment	'
	6.    Premises and equipment
	The detail of premises and equipment was as follows:
		December 31
		2013		2012
		(In thousands)
	Land	$	84,220	$	84,545
	Buildings — owned		402,065		393,527
	Buildings — capital leases		1,131		1,131
	Leasehold improvements		208,947		198,498
	Furniture and equipment — owned		547,824		465,113
	Furniture and equipment — capital leases		17,703		17,915
			1,261,890		1,160,729
	Less: accumulated depreciation and amortization
	Owned assets		617,228		559,948
	Capital leases		11,142		6,129
			628,370		566,077
	Premises and equipment, net	$	633,520	$	594,652
	Net lease expense for all operating leases totaled $103,297,000 in 2013, $102,924,000 in 2012 and $97,098,000 in 2011. 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
	Dec. 31, 2013
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 Year Ended December 31,	2013			2012			2011			2013			2012			2011
		(In thousands)
	Beginning balance	$	104,855		$	131,264		$	92,066		$	59,978		$	51,250		$	42,613
	Originations		52,375			14,577			13,920			26,754			19,653			17,613
	Purchases		272			109			61,642			—			—			—
	Recognized in loan securitization transactions		13,696			—			—			—			—			—
	Amortization		(44,821	)		(41,095	)		(36,364	)		(14,233	)		(10,925	)		(8,976	)
			126,377			104,855			131,264			72,499			59,978			51,250
	Valuation allowance		(300	)		(4,500	)		(1,800	)		—			—			—
	Ending balance, net	$	126,077		$	100,355		$	129,464		$	72,499		$	59,978		$	51,250
		Other									Total
	For Year Ended December 31,	2013			2012			2011			2013			2012			2011
		(In thousands)
	Beginning balance	$	8,143		$	15,678		$	26,197		$	172,976		$	198,192		$	160,876
	Originations		—			—			—			79,129			34,230			31,533
	Purchases		—			—			—			272			109			61,642
	Recognized in loan securitization transactions		9,382			—			—			23,078			—			—
	Amortization		(6,300	)		(7,535	)		(10,519	)		(65,354	)		(59,555	)		(55,859	)
			11,225			8,143			15,678			210,101			172,976			198,192
	Valuation allowance		—			—			—			(300	)		(4,500	)		(1,800	)
	Ending balance, net	$	11,225		$	8,143		$	15,678		$	209,801		$	168,476		$	196,392
	Residential mortgage loans serviced for others were $69.1 billion at December 31, 2013, $32.1 billion at December 31, 2012 and $36.3 billion at December 31, 2011. Reflected in residential mortgage loans serviced for others were loans sub-serviced for others of $46.6 billion, $12.5 billion and $14.3 billion at December 31, 2013, 2012, and 2011, respectively. Commercial mortgage loans serviced for others were $11.4 billion, $10.6 billion and $9.0 billion at December 31, 2013, 2012 and 2011, respectively. Other loans serviced for others include small balance commercial mortgage loans and automobile loans totaling $4.4 billion, $3.8 billion and $4.4 billion at December 31, 2013, 2012 and 2011, respectively.
	Changes in the valuation allowance for capitalized residential mortgage servicing assets were not significant in 2013, 2012 or 2011. The estimated fair value of capitalized residential mortgage loan servicing assets was approximately $266 million at December 31, 2013 and $138 million at December 31, 2012. The fair value of capitalized residential mortgage loan servicing assets was estimated using weighted-average discount rates of 9.3% and 10.6% at December 31, 2013 and 2012, respectively, and contemporaneous prepayment assumptions that vary by loan type. At December 31, 2013 and 2012, the discount rate represented a weighted-average option-adjusted spread (“OAS”) of 770 basis points (hundredths of one percent) and 929 basis points, respectively, over market implied forward London Interbank Offered Rates. 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 $85 million and $71 million at December 31, 2013 and 2012, respectively. An 18% discount rate was used to estimate the fair value of capitalized commercial mortgage loan servicing rights at December 31, 2013 and 2012 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, 2013 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		11.39	%
	Impact on fair value of 10% adverse change	$	(11,283,000	)
	Impact on fair value of 20% adverse change		(21,664,000	)
	Weighted-average OAS		7.7	%
	Impact on fair value of 10% adverse change	$	(5,714,000	)
	Impact on fair value of 20% adverse change		(11,155,000	)
	Weighted-average discount rate					18	%
	Impact on fair value of 10% adverse change				$	(3,677,000	)
	Impact on fair value of 20% adverse change					(7,096,000	)
	As described in note 19, during 2013 the Company securitized approximately $1.3 billion of one-to-four family residential mortgage loans formerly held in the Company’s loan portfolio in guaranteed mortgage securitizations with Ginnie Mae and securitized and sold approximately $1.4 billion of automobile loans. In conjunction with these transactions, the Company retained the servicing rights to the loans.

Goodwill_and_other_intangible_

Goodwill and other intangible assets	12 Months Ended
	Dec. 31, 2013
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		Accumulated		Net Carrying
		Amount		Amortization		Amount
		(In thousands)
	December 31, 2013
	Core deposit	$	755,794	$	705,518	$	50,276
	Other		177,268		158,693		18,575
	Total	$	933,062	$	864,211	$	68,851
	December 31, 2012
	Core deposit	$	755,794	$	670,940	$	84,854
	Other		177,268		146,359		30,909
	Total	$	933,062	$	817,299	$	115,763
	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. The remaining weighted-average amortization period as of December 31, 2013 was approximately three years. Amortization expense for core deposit and other intangible assets was $46,912,000, $60,631,000 and $61,617,000 for the years ended December 31, 2013, 2012 and 2011, respectively. Estimated amortization expense in future years for such intangible assets is as follows:
		(In thousands)
	Year ending December 31:
	2014	$	33,825
	2015		20,938
	2016		10,052
	2017		3,303
	2018		733
		$	68,851
	In accordance with GAAP, the Company completed annual goodwill impairment tests as of October 1, 2013, 2012 and 2011. 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, 2013 and 2012 for purposes of testing for impairment is as follows.
		(In thousands)
	Business Banking	$	748,907
	Commercial Banking		907,524
	Commercial Real Estate		349,197
	Discretionary Portfolio		—
	Residential Mortgage Banking		—
	Retail Banking		1,144,404
	All Other		374,593
	Total	$	3,524,625

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2013
Debt Disclosure [Abstract]	'
Borrowings	'
	9.    Borrowings
	The amounts and interest rates of short-term borrowings were as follows:
		Federal Funds			Other			Total
		Purchased			Short-term
		and			Borrowings
		Repurchase
		Agreements
		(Dollars in thousands)
	At December 31, 2013
	Amount outstanding	$	260,455		$	—		$	260,455
	Weighted-average interest rate		0.04	%		—			0.04	%
	For the year ended December 31, 2013
	Highest amount at a month-end	$	563,879		$	—
	Daily-average amount outstanding		390,034			—		$	390,034
	Weighted-average interest rate		0.11	%		—			0.11	%
	At December 31, 2012
	Amount outstanding	$	1,074,482		$	—		$	1,074,482
	Weighted-average interest rate		0.11	%		—			0.11	%
	For the year ended December 31, 2012
	Highest amount at a month-end	$	1,224,194		$	50,016
	Daily-average amount outstanding		822,859			16,043		$	838,902
	Weighted-average interest rate		0.15	%		0.57	%		0.15	%
	At December 31, 2011
	Amount outstanding	$	732,059		$	50,023		$	782,082
	Weighted-average interest rate		0.04	%		0.7	%		0.09	%
	For the year ended December 31, 2011
	Highest amount at a month-end	$	1,389,237		$	142,927
	Daily-average amount outstanding		706,749			120,059		$	826,808
	Weighted-average interest rate		0.11	%		0.18	%		0.12	%
	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, 2013 matured on the next business day following year-end. Other short-term borrowings at December 31, 2011 included $50 million of borrowings from FHLBs. There were no similar borrowings at December 31, 2013 or December 31, 2012.
	At December 31, 2013, the Company had lines of credit under formal agreements as follows:
		M&T			M&T Bank			Wilmington
								Trust, N.A.
		(In thousands)
	Outstanding borrowings	$	—		$	28,868		$	—
	Unused		30,000			19,838,117			300,710
	M&T has a revolving credit agreement with an unaffiliated commercial bank whereby M&T may borrow up to $30 million at its discretion through November 21, 2014. At December 31, 2013, M&T Bank had borrowing facilities available with the FHLBs whereby M&T Bank could borrow up to approximately $8.3 billion. Additionally, M&T Bank and Wilmington Trust, National Association (“Wilmington Trust, N.A.”), a wholly owned subsidiary of M&T, had available lines of credit with the Federal Reserve Bank of New York totaling approximately $11.8 billion at December 31, 2013. M&T Bank and Wilmington Trust, N.A. are required to pledge loans and investment securities as collateral for these borrowing facilities.
	Long-term borrowings were as follows:
		December 31,
		2013			2012
		(In thousands)
	Senior notes of M&T Bank:
	Variable rate due 2016	$	300,000		$	—
	1.45% due 2018		502,479			—
	Advances from FHLB:
	Fixed rates		29,079			30,066
	Agreements to repurchase securities		1,400,000			1,400,000
	Subordinated notes of Wilmington Trust Corporation
	(a wholly owned subsidiary of M&T):
	4.875% due 2013		—			251,298
	8.50% due 2018		224,067			230,255
	Subordinated notes of M&T Bank:
	6.625% due 2017		437,582			455,439
	9.50% due 2018		50,000			50,000
	5.585% due 2020, variable rate commencing 2015		392,964			385,669
	5.629% due 2021, variable rate commencing 2016		559,378			583,097
	Junior subordinated debentures of M&T associated with preferred capital securities:
	Fixed rates:
	M&T Capital Trust I — 8.234%, due 2027		154,640			154,640
	M&T Capital Trust II — 8.277%, due 2027		103,093			103,093
	M&T Capital Trust III — 9.25%, due 2027		66,109			66,434
	BSB Capital Trust I — 8.125%, due 2028		15,589			15,566
	Provident Trust I — 8.29%, due 2028		25,051			24,746
Southern Financial Statutory Trust I — 10.60%, due 2030		6,521			6,496
M&T Capital Trust IV — 8.50%, due 2068		350,010			350,010
Variable rates:
First Maryland Capital I — due 2027		144,641			144,102
First Maryland Capital II — due 2027		145,964			145,301
Allfirst Asset Trust — due 2029		96,059			95,913
BSB Capital Trust III — due 2033		15,464			15,464
Provident Trust III — due 2033		52,176			51,694
Southern Financial Capital Trust III — due 2033		7,747			7,683
Other		30,257			40,792
	$	5,108,870		$	4,607,758
During the first quarter of 2013, M&T Bank instituted a Bank Note Program whereby M&T Bank may offer up to $5 billion in unsecured senior and subordinated notes. During March 2013, three-year floating rate senior notes due March 2016 were issued for $300 million and five-year 1.45% fixed rate senior notes due March 2018 were issued for $500 million. The floating rate notes pay interest quarterly at rates that are indexed to the three-month LIBOR. The rate at December 31, 2013 was .54%.
Long-term fixed rate advances from the FHLB had contractual interest rates ranging from 3.48% to 7.32% at December 31, 2013 and 2012. The weighted-average contractual interest rates payable were 4.60% at December 31, 2013 and 4.64% at December 31, 2012. 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 3.61% to 4.30% at each of December 31, 2013 and 2012. The weighted-average contractual interest rates were 3.90% at each of those dates. The agreements outstanding at December 31, 2013 reflect various repurchase dates through 2017, 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 of $1.6 billion at each of December 31, 2013 and 2012.
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 fixed and floating 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 current risk-based capital guidelines, the Capital Securities are includable in M&T’s Tier 1 capital. However, in July 2013, the Federal Reserve Board, the Office of the Comptroller of the Currency and the Federal Deposit Insurance Corporation issued a final rule to comprehensively revise the capital framework for the U.S. banking sector. Under that rule, trust preferred capital securities will be phased out from inclusion in Tier 1 capital such that in 2015 only 25% of then-outstanding securities will be included in Tier 1 capital and beginning in 2016 none of the securities will be included in Tier 1 capital. The variable rate Junior Subordinated Debentures pay interest quarterly at rates that are indexed to the three-month LIBOR. Those rates ranged from 1.09% to 3.59% at December 31, 2013 and from 1.16% to 3.69% at December 31, 2012. The weighted-average variable rates payable on those Junior Subordinated Debentures were 1.67% at December 31, 2013 and 1.75% at December 31, 2012.
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 the event of an extended interest period exceeding twenty quarterly periods for $350 million of Junior Subordinated Debentures due January 31, 2068, M&T must fund the payment of accrued and unpaid interest through an alternative payment mechanism, which requires M&T to issue common stock, non-cumulative perpetual preferred stock or warrants to purchase common stock until M&T has raised an amount of eligible proceeds at least equal to the aggregate amount of accrued and unpaid deferred interest on the Junior Subordinated Debentures due January 31, 2068. 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 2068) 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. In January 2014, M&T announced that it will redeem all of the issued and outstanding 8.5% $350 million trust preferred securities issued by M&T Capital Trust IV and the related junior subordinated debentures held by M&T Capital Trust IV on February 27, 2014.
Long-term borrowings at December 31, 2013 mature as follows:
	(In thousands)
Year ending December 31:
2014	$	22,021
2015		5,756
2016		1,105,075
2017		1,041,871
2018		777,991
Later years		2,156,156
	$	5,108,870

Shareholders_equity

Shareholders' equity	12 Months Ended
	Dec. 31, 2013
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 is presented below:
			December 31, 2013				December 31, 2012
			Shares		Carrying		Shares		Carrying
			Issued and		Value		Issued and		Value
			Outstanding				Outstanding
			(Dollars in thousands)
	Series A(a)
	Fixed Rate Cumulative Perpetual Preferred Stock, Series A, $1,000 liquidation preference per share			230,000	$	230,000		230,000	$	226,965
	Series C(a)
	Fixed Rate Cumulative Perpetual Preferred Stock, Series C, $1,000 liquidation preference per share			151,500		151,500		151,500		145,535
	Series D(b)
	Fixed Rate Non-cumulative Perpetual Preferred Stock, Series D, $10,000 liquidation preference per share			50,000		500,000		50,000		500,000
	(a)	Shares were originally issued as part of the TARP of the U.S Treasury. Cash proceeds were allocated between the preferred stock and a ten-year warrant to purchase M&T common stock (Series A — 1,218,522 common shares at $73.86 per share, Series C — 407,542 common shares at $55.76 per share). The U.S. Treasury sold all of the shares of M&T preferred stock that it held in August 2012. In connection with that sale, the terms of the preferred stock were modified such that dividends, if declared, were paid quarterly at a rate of 5% per year through November 14, 2013 and at 6.375% thereafter, and M&T agreed to not redeem the preferred shares until on or after November 15, 2018. In December 2012, the U.S. Treasury sold to other investors the Series A warrants for $26.50 per warrant. In March 2013, the U.S. Treasury exercised the Series C warrants in a “cashless” exercise, resulting in the issuance of 186,589 common shares. During 2013, 69,127 of the Series A warrants were exercised in “cashless” exercises, resulting in the issuance of 25,427 common shares. Remaining outstanding Series A warrants were 1,149,395 at December 31, 2013.
	(b)	Dividends, if declared, will be paid semi-annually at a rate of 6.875% per year. The shares are redeemable in whole or in part on or after June 15, 2016. 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 and Series C warrants mentioned in (a) above, a ten-year warrant to purchase 95,383 shares of M&T common stock at $518.96 per share was outstanding at each of December 31, 2013 and 2012. That warrant was issued by Wilmington Trust in December 2008 as part of the TARP of the U.S. Treasury.

Stockbased_compensation_plans

Stock-based compensation plans	12 Months Ended
	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock-based compensation plans	'
	11.    Stock-based compensation plans
	Stock-based compensation expense was $55 million in 2013, $57 million in 2012 and $56 million in 2011. The Company recognized income tax benefits related to stock-based compensation of $29 million in 2013, $30 million in 2012 and $22 million in 2011.
	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. Through December 31, 2013, only stock-based compensation awards, including stock options, restricted stock and restricted stock units, that vest with the passage of time as service is provided have been issued. At December 31, 2013 and 2012, respectively, there were 4,874,542 and 5,307,228 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 generally vest over four years. Unrecognized compensation expense associated with restricted stock was $27 million as of December 31, 2013 and is expected to be recognized over a weighted-average period of 1.5 years. The Company generally will issue restricted shares from treasury stock to the extent available, but may also issue new shares. During 2013, 2012 and 2011, the number of restricted shares issued was 269,755, 453,908 and 451,248, respectively, with a weighted-average grant date fair value of $27,716,000, $36,969,000 and $38,369,000, respectively. Unrecognized compensation expense associated with restricted stock units was $9 million as of December 31, 2013 and is expected to be recognized over a weighted-average period of 1.4 years. During 2013, 2012 and 2011 the number of restricted stock units issued was 315,316, 278,505 and 242,282, respectively, with a weighted-average grant date fair value of $32,380,000, $22,139,000 and $20,921,000, respectively.
	A summary of restricted stock and restricted stock unit activity follows:
		Restricted			Weighted-		Restricted			Weighted-
		Stock Units			Average		Stock			Average
		Outstanding			Grant Price		Outstanding			Grant Price
	Unvested at January 1, 2013		799,495		$	70.28		1,095,631		$	71.01
	Granted		315,316			102.69		269,755			102.75
	Vested		(341,348	)		56.43		(446,882	)		56.74
	Cancelled		(2,633	)		96.9		(55,809	)		87.05
	Unvested at December 31, 2013		770,830		$	89.58		862,695		$	87.29
	Stock option awards
	Stock options issued generally vest 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 2013, 2012 and 2011 were not significant.
	A summary of stock option activity follows:
		Stock			Weighted-Average					Aggregate
		Options								Intrinsic Value
		Outstanding			Exercise		Life			(In thousands)
					Price		(In Years)
	Outstanding at January 1, 2013		7,033,359		$	103.3
	Granted		100			102.69
	Exercised		(1,998,841	)		95.27
	Expired		(153,857	)		138.46
	Outstanding at December 31, 2013		4,880,761		$	105.48		2.8		$	66,464
	Exercisable at December 31, 2013		4,879,148		$	105.49		2.8		$	66,400
	For 2013, 2012 and 2011, M&T received $172 million, $153 million and $28 million, respectively, in cash and realized tax benefits from the exercise of stock options of $12 million, $8 million and $3 million, respectively. The intrinsic value of stock options exercised during those periods was $34 million, $21 million and $7 million, respectively. As of December 31, 2013, 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 2013 was not significant, and for 2012 and 2011 was $17 million and $29 million, respectively. Upon the exercise of stock options, the Company generally issues shares from treasury stock to the extent available, but may also 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, of which no shares have been issued. There were no shares issued in 2013, 151,014 shares issued in 2012 under a previous plan and no shares issued in 2011. For 2012 M&T received $10,117,000 in cash for shares purchased through the employee stock purchase plan. Compensation expense recognized for the stock purchase plan was not significant in 2013, 2012 or 2011.
	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 33,046 and 38,593 at December 31, 2013 and 2012, respectively. The obligation to issue shares is included in “common stock issuable” in the consolidated balance sheet. Through December 31, 2013, 139,429 shares have been issued in connection with the deferred bonus plan.
	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, 2013, 197,905 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 14,185 and 18,816 at December 31, 2013 and 2012, respectively. The obligation to issue shares is included in “common stock issuable” in the consolidated balance sheet.

Pension_plans_and_other_postre

Pension plans and other postretirement benefits	12 Months Ended
	Dec. 31, 2013
Compensation And Retirement Disclosure [Abstract]	'
Pension plans and other postretirement benefits	'
	12.    Pension plans and other postretirement benefits
	The Company provides pension (defined benefit and defined contribution plans) and other postretirement benefits (including defined benefit health care and life insurance plans) 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
			2013			2012			2011
			(In thousands)
	Service cost		$	24,360		$	29,549		$	28,828
	Interest cost on benefit obligation			60,130			62,037			58,545
	Expected return on plan assets			(87,353	)		(70,511	)		(60,700	)
	Amortization of prior service credit			(6,556	)		(6,559	)		(6,559	)
	Recognized net actuarial loss			41,076			37,386			20,530
	Net periodic pension expense		$	31,657		$	51,902		$	40,644
	Net other postretirement benefits expense for defined benefit plans consisted of the following:
			Year Ended December 31
			2013			2012			2011
			(In thousands)
	Service cost		$	742		$	668		$	535
	Interest cost on benefit obligation			2,691			3,737			3,761
	Amortization of prior service cost (credit)			(1,359	)		21			107
	Recognized net actuarial loss			360			530			36
	Net other postretirement benefits expense		$	2,434		$	4,956		$	4,439
	Data relating to the funding position of the defined benefit plans were as follows:
			Pension Benefits						Other
									Postretirement Benefits
			2013			2012			2013			2012
			(In thousands)
	Change in benefit obligation:
	Benefit obligation at beginning of year		$	1,644,567		$	1,496,490		$	74,966		$	90,104
	Service cost			24,360			29,549			742			668
	Interest cost			60,130			62,037			2,691			3,737
	Plan participants’ contributions			—			—			3,069			3,765
	Amendments			—			—			—			(13,313	)
	Actuarial (gain) loss			(184,181	)		116,237			(12,830	)		(182	)
	Settlements/curtailments			—			(320	)		—			—
	Medicare Part D reimbursement			—			—			509			918
	Benefits paid			(60,683	)		(59,426	)		(8,555	)		(10,731	)
	Benefit obligation at end of year			1,484,193			1,644,567			60,592			74,966
	Change in plan assets:
	Fair value of plan assets at beginning of year			1,408,771			1,117,972			—			—
	Actual return on plan assets			150,795			143,430			—			—
	Employer contributions			7,801			207,115			4,977			6,048
	Plan participants’ contributions			—			—			3,069			3,765
	Medicare Part D reimbursement			—			—			509			918
	Settlements			—			(320	)		—			—
	Benefits and other payments			(60,683	)		(59,426	)		(8,555	)		(10,731	)
	Fair value of plan assets at end of year			1,506,684			1,408,771			—			—
	Funded status		$	22,491		$	(235,796	)	$	(60,592	)	$	(74,966	)
	Assets and liabilities recognized in the consolidated balance sheet were:
	Net prepaid asset		$	139,576		$	—		$	—		$	—
	Accrued liabilities			(117,085	)		(235,796	)		(60,592	)		(74,966	)
	Amounts recognized in accumulated other comprehensive income (“AOCI”) were:
	Net loss (gain)		$	191,386		$	480,084		$	(1,056	)	$	12,134
	Net prior service cost			(16,899	)		(23,455	)		(11,814	)		(13,173	)
	Pre-tax adjustment to AOCI			174,487			456,629			(12,870	)		(1,039	)
	Taxes.			(68,486	)		(179,227	)		5,051			408
	Net adjustment to AOCI.		$	106,001		$	277,402		$	(7,819	)	$	(631	)
	The Company has an unfunded supplemental pension plan for certain key executives. The projected benefit obligation and accumulated benefit obligation included in the preceding data related to such plan were $117,085,000 as of December 31, 2013 and $130,745,000 as of December 31, 2012.
	The accumulated benefit obligation for all defined benefit pension plans was $1,460,498,000 and $1,618,119,000 at December 31, 2013 and 2012, 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. As indicated in the preceding table, as of December 31, 2013 the Company recorded a minimum liability adjustment of $161,617,000 ($174,487,000 related to pension plans and $(12,870,000) related to other postretirement benefits) with a corresponding reduction of shareholders’ equity, net of applicable deferred taxes, of $98,182,000. In aggregate, the benefit plans realized a net gain during 2013 that resulted from actual experience differing from the plan assumptions utilized and from changes in actuarial assumptions. The main factors contributing to that gain were actual investment returns from assets in the qualified defined benefit pension plan that exceeded expected returns and from an increase in the discount rate used in the measurement of the benefit obligations to 4.75% at December 31, 2013 from 3.75% at December 31, 2012. As a result, the Company decreased its minimum liability adjustment from that which was recorded at December 31, 2012 by $293,973,000 with a corresponding increase to shareholders’ equity that, net of applicable deferred taxes, was $178,589,000. 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			Total
						Postretirement
						Benefit Plans
			(In thousands)
2013
Net gain		$	(247,622	)	$	(12,830	)	$	(260,452	)
Amortization of prior service credit			6,556			1,359			7,915
Amortization of loss			(41,076	)		(360	)		(41,436	)
Total recognized in other comprehensive income, pre-tax		$	(282,142	)	$	(11,831	)	$	(293,973	)
2012
Net loss (gain)		$	43,318		$	(182	)	$	43,136
Prior service credit			—			(13,313	)		(13,313	)
Amortization of prior service (cost) credit			6,559			(21	)		6,538
Amortization of loss			(37,386	)		(530	)		(37,916	)
Total recognized in other comprehensive income, pre-tax		$	12,491		$	(14,046	)	$	(1,555	)
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 2014:
		Pension Plans			Other
					Postretirement
					Benefit Plans
		(In thousands)
Amortization of net prior service credit		$	(6,552	)	$	(1,359	)
Amortization of net loss			13,460			—
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 2013, 2012 and 2011 associated with the defined contribution pension plan was approximately $21 million, $17 million and $13 million, respectively.
Assumptions
The assumed weighted-average rates used to determine benefit obligations at December 31 were:
		Pension						Other
		Benefits						Postretirement
								Benefits
		2013			2012			2013			2012
Discount rate			4.75	%		3.75	%		4.75	%		3.75	%
Rate of increase in future compensation levels			4.42	%		4.5	%		—			—
The assumed weighted-average rates used to determine net benefit expense for the years ended December 31 were:
		Pension Benefits									Other
											Postretirement Benefits
		2013			2012			2011			2013			2012			2011
Discount rate			3.75	%		4.25	%		5.25	%		3.75	%		4.25	%		5.25	%
Long-term rate of return on plan assets			6.5	%		6.5	%		6.5	%		—			—			—
Rate of increase in future compensation levels			4.5	%		4.5	%		4.5	%		—			—			—
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.
For measurement of other postretirement benefits, a 7.50% annual rate of increase in the per capita cost of covered health care benefits was assumed for 2014. The rate was assumed to decrease to 5.0% over 30 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		$	100		$	(91	)
Accumulated postretirement benefit obligation			2,147			(1,947	)
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 a strong 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 45 to 80 percent equity securities, 5 to 40 percent debt securities, and 3 to 30 percent money-market funds/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. Equity securities include investments in large-cap and mid-cap companies located in the United States and equity mutual funds with domestic and international investments, and, to a lesser extent, direct investments in foreign-based companies. Debt securities include corporate bonds of companies from diversified industries, mortgage-backed securities guaranteed by government agencies, U.S. Treasury securities, and mutual funds that invest in debt securities. Additionally, the Company’s defined benefit pension plan held $168,040,000 (11.2% of total assets) of real estate, private equity and other investments at December 31, 2013. 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, 2013, by asset category, were as follows:
		Fair Value Measurement of Plan Assets At December 31, 2013
		Total			Quoted Prices			Significant			Significant
					in Active			Observable			Unobservable
					Markets			Inputs			Inputs
					for Identical Assets			(Level 2)			(Level 3)
					(Level 1)
		(In thousands)
Asset category:
Money-market funds		$	37,952		$	37,952		$	—		$	—
Equity securities:
M&T			142,955			142,955			—			—
Domestic(a)			271,203			271,203			—			—
International			24,053			24,053			—			—
Mutual funds:
Domestic			194,099			194,099			—			—
International			413,685			413,685			—			—
			1,045,995			1,045,995			—			—
Debt securities:
Corporate(b)			63,196			—			63,196			—
Government			75,043			—			75,043			—
International			2,443			—			2,443			—
Mutual funds:
Domestic(c)			68,280			68,280			—			—
International			43,742			43,742			—			—
			252,704			112,022			140,682			—
Other:
Diversified mutual fund			93,055			93,055			—			—
Private real estate			3,123			—			—			3,123
Private equity			6,199			—			—			6,199
Hedge funds			65,663			41,489			—			24,174
			168,040			134,544			—			33,496
Total(d)		$	1,504,691		$	1,330,513		$	140,682		$	33,496
The fair values of the Company’s pension plan assets at December 31, 2012, by asset category, were as follows:
		Fair Value Measurement of Plan Assets At December 31, 2012
		Total			Quoted Prices			Significant			Significant
					in Active			Observable			Unobservable
					Markets			Inputs			Inputs
					for Identical Assets			(Level 2)			(Level 3)
					(Level 1)
		(In thousands)
Asset category:
Money-market funds		$	46,657		$	46,657		$	—		$	—
Equity securities:
M&T			120,914			120,914			—			—
Domestic(a)			147,382			147,382			—			—
International			8,561			8,561			—			—
Mutual funds:
Domestic			188,950			188,950			—			—
International			208,696			208,696			—			—
			674,503			674,503			—			—
Debt securities:
Corporate(b)			307,712			—			307,712			—
Government			141,224			—			141,224			—
International			10,230			—			10,230			—
Mutual funds:
Domestic(c)			107,576			107,576			—			—
International			54,362			54,362			—			—
			621,104			161,938			459,166			—
Other:
Diversified mutual fund			10,415			10,415			—			—
Private real estate			4,603			—			—			4,603
Private equity			5,347			—			—			5,347
Hedge funds			41,509			10,000			—			31,509
			61,874			20,415			—			41,459
Total(d)		$	1,404,138		$	903,513		$	459,166		$	41,459
(a)	This category is comprised of equities of companies primarily within the mid-cap and large-cap sector of the U.S. economy and range across diverse industries.
(b)	This category represents investment grade bonds of U.S. issuers from diverse industries.
(c)	Approximately 35% of the mutual funds were invested in investment grade bonds of U.S. issuers and 65% in high-yielding bonds at December 31, 2013. Approximately 40% of the mutual funds were invested in investment grade bonds of U.S. issuers and 60% in high-yielding bonds at December 31, 2012. The holdings within the funds are spread across diverse industries.
(d)	Excludes dividends and interest receivable totaling $1,993,000 and $4,633,000 at December 31, 2013 and 2012, respectively.
Pension plan assets included common stock of M&T with a fair value of $142,955,000 (9.5% of total plan assets) at December 31, 2013 and $120,914,000 (8.6% of total plan assets) at December 31, 2012. No investment in securities of a non-U.S. Government or government agency issuer exceeded ten percent of plan assets at December 31, 2013. Assets subject to Level 3 valuations did not constitute a significant portion of plan assets at December 31, 2013 or December 31, 2012.
The changes in Level 3 pension plan assets measured at estimated fair value on a recurring basis during the year ended December 31, 2013 were as follows:
		Balance –			Sales/			Total			Balance –
		January 1,			Purchases			Realized/			December 31,
		2013						Unrealized			2013
								Gains (Losses)
		(In thousands)
Other
Private real estate		$	4,603		$	(308	)	$	(1,172	)	$	3,123
Private equity			5,347			165			687			6,199
Hedge funds			31,509			(9,873	)		2,538			24,174
Total		$	41,459		$	(10,016	)	$	2,053		$	33,496
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. Subject to the impact of actual events and circumstances that may occur in 2014, the Company may make contributions to the qualified defined benefit pension plan in 2014, but the amount of any such contribution has not yet been determined. The Company made cash contributions of $200 million and $70 million to the qualified defined benefit pension plan in 2012 and 2011, respectively. The Company did not make any contributions to the plan in 2013. The Company regularly funds the payment of benefit obligations for the supplemental defined benefit pension and postretirement benefit plans because such plans do not hold assets for investment. Payments made by the Company for supplemental pension benefits were $7,801,000 and $7,115,000 in 2013 and 2012, respectively. Payments made by the Company for postretirement benefits were $4,977,000 and $6,048,000 in 2013 and 2012, respectively. Payments for supplemental pension and other postretirement benefits for 2014 are not expected to differ from those made in 2013 by an amount that will be material to the Company’s consolidated financial position.
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			Other
		Benefits			Postretirement
					Benefits
		(In thousands)
Year ending December 31:
2014		$	65,970		$	6,780
2015			67,993			6,503
2016			73,628			6,283
2017			77,180			5,995
2018			80,380			5,741
2019 through 2023			461,397			25,172
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 $31,797,000, $31,305,000 and $27,738,000 in 2013, 2012 and 2011, respectively.

Income_taxes

Income taxes	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Income taxes	'
	13.    Income taxes
	The components of income tax expense (benefit) were as follows:
		Year Ended December 31
		2013			2012			2011
		(In thousands)
	Current
	Federal	$	371,249		$	309,156		$	277,631
	State and city		68,035			82,014			53,566
	Total current		439,284			391,170			331,197
	Deferred
	Federal		106,537			117,229			34,325
	State and city		33,248			14,629			(401	)
	Total deferred		139,785			131,858			33,924
	Total income taxes applicable to pre-tax income	$	579,069		$	523,028		$	365,121
	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, 2013, M&T Bank’s tax bad debt reserve for which no federal income taxes have been provided was $79,121,000. 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 expenses of $18,313,000 in 2013 and $28,712,000 in 2011 and a benefit of $18,766,000 in 2012. No alternative minimum tax expense was recognized in 2013, 2012 or 2011.
	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
		2013			2012			2011
		(In thousands)
	Income taxes at statutory federal income tax rate	$	601,142		$	543,384		$	428,610
	Increase (decrease) in taxes:
	Tax-exempt income		(34,747	)		(33,890	)		(33,799	)
	State and city income taxes, net of federal income tax effect		65,834			62,818			34,557
	Low income housing and other credits		(49,206	)		(42,074	)		(40,763	)
	Non-taxable gain on acquisition		—			—			(22,725	)
	Other		(3,954	)		(7,210	)		(759	)
		$	579,069		$	523,028		$	365,121
	Deferred tax assets (liabilities) were comprised of the following at December 31:
		2013			2012			2011
		(In thousands)
	Losses on loans and other assets	$	645,713		$	809,033		$	896,219
	Postretirement and other employee benefits		30,023			34,517			39,992
	Incentive compensation plans		37,772			50,067			49,183
	Interest on loans		100,725			72,278			46,965
	Retirement benefits		—			91,980			147,997
	Stock-based compensation		63,101			69,874			78,014
	Unrealized investment losses		—			—			50,528
	Depreciation and amortization		1,404			12,130			9,563
	Other		121,561			103,027			99,012
	Gross deferred tax assets		1,000,299			1,242,906			1,417,473
	Leasing transactions		(284,370	)		(291,524	)		(294,150	)
	Unrealized investment gains		(21,779	)		(23,574	)		—
	Capitalized servicing rights		(46,041	)		(20,348	)		(17,603	)
	Interest on subordinated note exchange		(6,075	)		(8,794	)		(11,275	)
	Retirement benefits		(9,397	)		—			—
	Other		(49,450	)		(61,410	)		(48,803	)
	Gross deferred tax liabilities		(417,112	)		(405,650	)		(371,831	)
	Net deferred tax asset	$	583,187		$	837,256		$	1,045,642
	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,			Accrued			Unrecognized
		State and			Interest			Income Tax
		Local Tax						Benefits
		(In thousands)
	Gross unrecognized tax benefits at January 1, 2011	$	24,853		$	20,696		$	45,549
	Increases in unrecognized tax benefits as a result of tax positions taken during 2011		4,659			—			4,659
	Decreases in unrecognized tax benefits as a result of settlements with taxing authorities		(9,742	)		(5,497	)		(15,239	)
	Decreases in unrecognized tax benefits as a result of tax positions taken in prior years		—			(1,645	)		(1,645	)
	Decreases in unrecognized tax benefits because applicable returns are no longer subject to examination		(8,471	)		(8,201	)		(16,672	)
	Unrecognized tax benefits acquired in a business combination		7,034			3,924			10,958
	Gross unrecognized tax benefits at December 31, 2011		18,333			9,277			27,610
Increases in unrecognized tax benefits as a result of tax positions taken during 2012		860			—			860
Increases in unrecognized tax benefits as a result of tax positions taken in prior years		—			4,514			4,514
Decreases in unrecognized tax benefits as a result of settlements with taxing authorities		(1,002	)		—			(1,002	)
Decreases in unrecognized tax benefits because applicable returns are no longer subject to examination		(1,643	)		(1,412	)		(3,055	)
Gross unrecognized tax benefits at December 31, 2012		16,548			12,379			28,927
Increases in unrecognized tax benefits as a result of tax positions taken during 2013		2,267			—			2,267
Increases in unrecognized tax benefits as a result of tax positions taken in prior years		—			4,429			4,429
Decreases in unrecognized tax benefits as a result of settlements with taxing authorities		(1,854	)		(487	)		(2,341	)
Decreases in unrecognized tax benefits because applicable returns are no longer subject to examination		(2,350	)		(1,625	)		(3,975	)
Gross unrecognized tax benefits at December 31, 2013	$	14,611		$	14,696			29,307
Less: Federal, state and local income tax benefits								(9,611	)
Net unrecognized tax benefits at December 31, 2013 that, if recognized, would impact the effective income tax rate							$	19,696
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, 2013 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. Under statute, the Company’s federal income tax returns for the years 2010, 2011 and 2012 could be adjusted by the Internal Revenue Service, although examinations for those tax years have been concluded. 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 2010. 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
	Dec. 31, 2013
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
			2013			2012			2011
			(In thousands, except per share)
	Income available to common shareholders:
	Net income		$	1,138,480		$	1,029,498		$	859,479
	Less: Preferred stock dividends(a)			(54,120	)		(53,450	)		(45,839	)
	Amortization of preferred stock discount(a)			(7,942	)		(8,026	)		(20,018	)
	Net income available to common equity			1,076,418			968,022			793,622
	Less: Income attributable to unvested stock-based compensation awards			(13,989	)		(14,632	)		(11,879	)
	Net income available to common shareholders		$	1,062,429		$	953,390		$	781,743
	Weighted-average shares outstanding:
	Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards			130,354			127,793			124,524
	Less: Unvested stock-based compensation awards			(1,700	)		(1,929	)		(1,861	)
	Weighted-average shares outstanding			128,654			125,864			122,663
	Basic earnings per common share		$	8.26		$	7.57		$	6.37
	(a)	Including impact of not as yet declared cumulative dividends.
	The computations of diluted earnings per common share follow:
			Year Ended December 31
			2013			2012			2011
			(In thousands, except per share)
	Net income available to common equity		$	1,076,418		$	968,022		$	793,622
	Less: Income attributable to unvested stock-based compensation awards			(13,922	)		(14,593	)		(11,857	)
	Net income available to common shareholders		$	1,062,496		$	953,429		$	781,765
	Adjusted weighted-average shares outstanding:
	Common and unvested stock-based compensation awards			130,354			127,793			124,524
	Less: Unvested stock-based compensation awards			(1,700	)		(1,929	)		(1,861	)
	Plus: Incremental shares from assumed conversion of stock-based compensation awards			949			541			416
	Adjusted weighted-average shares outstanding			129,603			126,405			123,079
	Diluted earnings per common share		$	8.2		$	7.54		$	6.35
	GAAP defines unvested share-based awards that contain nonforfeitable rights to dividends or dividend equivalents (whether paid or unpaid) as participating securities that 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, which, in accordance with GAAP, are considered participating securities.
	Stock-based compensation awards and warrants to purchase common stock of M&T representing approximately 3,847,000, 8,905,000 and 11,268,000 common shares during 2013, 2012 and 2011, respectively, were not included in the computations of diluted earnings per common share because the effect on those years would have been antidilutive.

Comprehensive_income

Comprehensive income	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
Comprehensive income	'
	15.    Comprehensive income
	The following tables display the components of other comprehensive income (loss) and amounts reclassified from accumulated other comprehensive income (loss) to net income.
			Investment Securities						Defined			Other			Total			Income			Net
									Benefit						Amount			Tax
			With			All			Plans						Before Tax
			OTTI			Other
			(in thousands)
	Balance — January 1, 2013		$	(91,835	)		152,199			(455,590	)		(431	)	$	(395,657	)		155,393		$	(240,264	)
	Other comprehensive income before reclassifications:
	Unrealized holding gains (losses), net			77,794			(129,628	)		—			—			(51,834	)		20,311			(31,523	)
	Foreign currency translation adjustment			—			—			—			546			546			(165	)		381
	Current year pension gains (losses)			—			—			260,452			—			260,452			(102,227	)		158,225
	Total other comprehensive income before reclassifications			77,794			(129,628	)		260,452			546			209,164			(82,081	)		127,083
	Amounts reclassified from accumulated other
	comprehensive income that
	(increase) decrease net income:
	Accretion of unrealized holding losses on held-to-maturity (“HTM”) securities			279			4,008			—			—			4,287	(a)		(1,683	)		2,604
	OTTI charges recognized in net income			9,800			—			—			—			9,800	(b)		(3,847	)		5,953
	Losses (gains) realized in net income			41,217			(8,129	)		—			—			33,088	(c)		(12,987	)		20,101
	Amortization of prior service credit			—			—			(7,915	)		—			(7,915	)(e)		3,107			(4,808	)
	Amortization of actuarial losses			—			—			41,436			—			41,436	(e)		(16,264	)		25,172
	Total reclassifications			51,296			(4,121	)		33,521			—			80,696			(31,674	)		49,022
	Total gain (loss) during the			129,090			(133,749	)		293,973			546			289,860			(113,755	)		176,105
	period
	Balance — December 31, 2013		$	37,255			18,450			(161,617	)		115		$	(105,797	)		41,638		$	(64,159	)
			Investment Securities						Defined			Other			Total			Income			Net
									Benefit						Amount			Tax
			With			All			Plans						Before Tax
			OTTI			Other
			(in thousands)
	Balance — January 1, 2012		$	(138,319	)		9,757			(457,145	)		(1,062	)	$	(586,769	)		230,328		$	(356,441	)
	Other comprehensive income before reclassifications:
	Unrealized holding gains (losses), net			(2,998	)		137,921			—			—			134,923			(52,905	)		82,018
	Foreign currency translation adjustment			—			—			—			809			809			(290	)		519
	Current year pension			—			—			(29,823	)		—			(29,823	)		11,705			(18,118	)
	gains (losses)
	Total other comprehensive income before reclassifications			(2,998	)		137,921			(29,823	)		809			105,909			(41,490	)		64,419
	Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income:
	Accretion of unrealized holding losses on HTM securities			1,660			4,530			—			—			6,190	(a)		(2,430	)		3,760
	OTTI charges recognized in net income			47,822			—			—			—			47,822	(b)		(18,770	)		29,052
	Losses (gains) realized in net income			—			(9	)		—			—			(9	)(c)		4			(5	)
	Amortization of gains on terminated cash flow hedges			—			—			—			(178	)		(178	)		66			(112	)
	Amortization of prior service credit			—			—			(6,538	)		—			(6,538	)(e)		2,566			(3,972	)
	Amortization of actuarial losses			—			—			37,916			—			37,916	(e)		(14,881	)		23,035
	Total reclassifications			49,482			4,521			31,378			(178	)		85,203			(33,445	)		51,758
	Total gain (loss) during the period			46,484			142,442			1,555			631			191,112			(74,935	)		116,177
	Balance — December 31, 2012		$	(91,835	)		152,199			(455,590	)		(431	)	$	(395,657	)		155,393		$	(240,264	)
			Investment Securities						Defined			Other			Total			Income			Net
									Benefit						Amount			Tax
			With			All			Plans						Before Tax
			OTTI			Other
			(in thousands)
	Balance — January 1, 2011		$	(143,139	)		3,860			(198,999	)		626		$	(337,652	)		132,432		$	(205,220	)
	Other comprehensive income before reclassifications:
	Unrealized holding gains (losses), net			(68,946	)		145,522			—			—			76,576			(29,786	)		46,790
	Foreign currency translation adjustment			—			—			—			(1,240	)		(1,240	)		437			(803	)
	Current year pension			—			—			(272,260	)		—			(272,260	)		106,862			(165,398	)
	gains (losses)
	Total other comprehensive income before reclassifications			(68,946	)		145,522			(272,260	)		(1,240	)		(196,924	)		77,513			(119,411	)
	Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income:
	Accretion of unrealized holding losses on HTM securities			545			6,490			—			—			7,035	(a)		(2,762	)		4,273
	OTTI charges recognized in net income			77,035			—			—			—			77,035	(b)		(30,235	)		46,800
	Losses (gains) realized in net income			(3,814	)		(146,115	)		—			—			(149,929	)(c)		58,753			(91,176	)
Amortization of gains on terminated cash flow hedges			—			—			—			(448	)		(448	)(d)		167			(281	)
Amortization of prior service credit			—			—			(6,452	)		—			(6,452	)(e)		2,532			(3,920	)
Amortization of actuarial losses			—			—			20,566			—			20,566	(e)		(8,072	)		12,494
Total reclassifications			73,766			(139,625	)		14,114			(448	)		(52,193	)		20,383			(31,810	)
Total gain (loss) during the period			4,820			5,897			(258,146	)		(1,688	)		(249,117	)		97,896			(151,221	)
Balance — December 31, 2011		$	(138,319	)		9,757			(457,145	)		(1,062	)	$	(586,769	)		230,328		$	(356,441	)
(a)	Included in interest income.
(b)	Included in OTTI losses recognized in earnings.
(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 unrealized gains (losses) as follows:
								Cash			Foreign			Defined			Total
								Flow			Currency			Benefit
		Investment Securities						Hedges			Translation			Plans
		With OTTI			All Other						Adjustment
		(In thousands)
Balance at January 1, 2011		$	(87,053	)	$	2,332		$	393		$	—		$	(120,892	)	$	(205,220	)
Net gain (loss) during 2011			3,024			3,663			(281	)		(803	)		(156,824	)		(151,221	)
Balance at December 31, 2011			(84,029	)		5,995			112			(803	)		(277,716	)		(356,441	)
Net gain (loss) during 2012			28,239			86,586			(112	)		519			945			116,177
Balance at December 31, 2012			(55,790	)		92,581			—			(284	)		(276,771	)		(240,264	)
Net gain (loss) during 2013			78,422			(81,287	)		—			381			178,589			176,105
Balance at December 31, 2013		$	22,632		$	11,294		$	—		$	97		$	(98,182	)	$	(64,159	)

Other_income_and_other_expense

Other income and other expense	12 Months Ended
	Dec. 31, 2013
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
		2013		2012		2011
		(In thousands)
	Other income:
	Bank owned life insurance	$	56,120	$	51,199	$	50,776
	Credit-related fee income		72,271		68,596		73,886
	Letter of credit fees		59,889		58,496		56,247
	Non-taxable gain from business combination						64,930
	Gains from loan securitization transactions		63,066
	Other expense:
	Professional services		335,794		248,544		222,122
	Amortization of capitalized servicing rights		65,354		59,555		55,859
	Advertising and promotion		56,597		52,388		58,312
	Write-down of investment in Bayview Lending Group LLC (“BLG”)						79,012

International_activities

International activities	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
International activities	'
	17.    International activities
	The Company engages in certain international activities consisting largely of collecting Eurodollar deposits, engaging in foreign currency trading on behalf of customers, providing credit to support the international activities of domestic companies and holding certain loans to foreign borrowers. As a result of the Wilmington Trust acquisition, the Company offers certain trust-related services in Europe and the Cayman Islands. Revenues from providing such trust-related services were approximately $26 million in 2013, $24 million in 2012 and $15 million in 2011. Net assets identified with international activities amounted to $226 million and $179 million at December 31, 2013 and 2012, respectively. Such assets included $192 million and $149 million, respectively, of loans to foreign borrowers. Deposits at M&T Bank’s Cayman Islands office were $323 million and $1.0 billion at December 31, 2013 and 2012, 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.

Derivative_financial_instrumen

Derivative financial instruments	12 Months Ended
	Dec. 31, 2013
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 and collateral provisions protecting the at-risk party. Based on adherence to the Company’s credit standards and the presence of the netting and collateral provisions, the Company believes that the credit risk inherent in these contracts was not significant as of December 31, 2013.
	The net effect of interest rate swap agreements was to increase net interest income by $41 million in 2013, $36 million in 2012 and $38 million in 2011. The average notional amounts of interest rate swap agreements impacting net interest income that were entered into for interest rate risk management purposes were $1.2 billion in 2013 and $900 million in each of 2012 and 2011.
	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:
			Notional			Average		Weighted-Average						Estimated Fair
			Amount			Maturity		Rate						Value Gain
								Fixed			Variable
			(In thousands)			(In years)								(In thousands)
	December 31, 2013
	Fair value hedges:
	Fixed rate long-term borrowings(a)		$	1,400,000			3.7		4.42	%		1.2	%	$	102,875
	December 31, 2012
	Fair value hedges:
	Fixed rate long-term borrowings(a)		$	900,000			4.4		6.07	%		1.85	%	$	143,179
	(a)	Under the terms of these agreements, the Company receives settlement amounts at a fixed rate and pays at a variable rate.
	The notional amount of interest rate swap agreements entered into for risk management purposes that were outstanding at December 31, 2013 mature as follows:
			(In thousands)
	Year ending December 31:
	2016		$	500,000
	2017			400,000
	2018			500,000
			$	1,400,000
	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 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 purposes had notional values of $17.4 billion and $15.5 billion at December 31, 2013 and 2012, respectively. The notional amounts of foreign currency and other option and futures contracts entered into for trading purposes aggregated $1.4 billion and $869 million at December 31, 2013 and 2012, 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
			2013			2012		2013			2012
			(In thousands)
	Derivatives designated and qualifying as hedging instruments
	Fair value hedges:
	Interest rate swap agreements(a)		$	102,875		$	143,179	$	—		$	—
	Commitments to sell real estate loans(a)			6,957			1,114		487			3,825
				109,832			144,293		487			3,825
	Derivatives not designated and qualifying as hedging instruments
	Mortgage-related commitments to originate real estate loans for sale(a)			7,616			48,056		3,675			197
	Commitments to sell real estate loans(a)			6,120			1,982		230			6,570
	Trading:
	Interest rate contracts(b)			274,864			399,963		234,455			365,616
	Foreign exchange and other option and futures contracts(b)			15,831			8,725		15,342			8,658
				304,431			458,726		253,702			381,041
	Total derivatives		$	414,263		$	603,019	$	254,189		$	384,866
	(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.
			Amount of Unrealized Gain (Loss) Recognized
			Year Ended					Year Ended						Year Ended
			December 31, 2013					December 31, 2012						December 31, 2011
			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)		$	(40,304	)	$	38,986	$	(4,123	)	$	3,724		$	50,665		$	(47,916	)
	Derivatives not designated as hedging instruments
	Trading:
	Interest rate contracts(b)		$	9,824				$	8,004					$	6,130
	Foreign exchange and other option and futures contracts(b)			(3,369	)				(3,970	)					(2,649	)
	Total		$	6,455				$	4,034					$	3,481
	(a)	Reported as other revenues from operations.
	(b)	Reported as trading account and foreign exchange gains.
	In addition, 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 $23 million and $89 million at December 31, 2013 and 2012, 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 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 $194 million and $374 million at December 31, 2013 and 2012, respectively. After consideration of such netting arrangements, the net liability positions with counterparties aggregated $107 million and $281 million at December 31, 2013 and 2012, respectively. The Company was required to post collateral relating to those positions of $95 million and $266 million at December 31, 2013 and 2012, 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 rating were to fall below specified ratings, the counterparties to 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, 2013 was $34 million, for which the Company had posted collateral of $23 million in the normal course of business. If the credit risk-related contingent features had been triggered on December 31, 2013, the maximum amount of additional collateral the Company would have been required to post with counterparties was $11 million.
The aggregate fair value of derivative financial instruments in an asset position, which are subject to enforceable master netting arrangements, was $183 million and $164 million at December 31, 2013 and 2012, respectively. After consideration of such netting arrangements, the net asset positions with counterparties aggregated $95 million and $71 million at December 31, 2013 and 2012, respectively. Counterparties posted collateral relating to those positions of $93 million and $69 million at December 31, 2013 and 2012, 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.

Variable_interest_entities_and

Variable interest entities and asset securitizations	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
Variable interest entities and asset securitizations	'
	19.    Variable interest entities and asset securitizations
	During 2013, the Company securitized approximately $3.0 billion of one-to-four family residential mortgage loans in guaranteed mortgage securitizations with Ginnie Mae. Approximately $1.3 billion of such loans were formerly held in the Company’s loan portfolio, whereas the remaining loans were newly originated. The Company recognized pre-tax gains of $42 million related to loans previously held in portfolio, which have been recorded in “other revenues from operations,” and pre-tax gains of $28 million on newly originated loans, which have been reflected in “mortgage banking revenues.” As a result of the securitization structure, the Company does not have effective control over the underlying loans and expects no material credit-related losses on the retained securities as a result of the guarantees by Ginnie Mae. Additionally, in 2013 the Company securitized and sold approximately $1.4 billion of automobile loans that had been held in its loan portfolio. The Company recognized a gain of $21 million related to the sale, which has been recorded in “other revenues from operations.” The Company continues to service the automobile loans, but has no other financial interest in the securitization trust that the loans were sold into. The Company securitized loans to improve its regulatory capital ratios and strengthen its liquidity and risk profile as a result of changing regulatory requirements.
	In accordance with GAAP, the Company determined that it was the primary beneficiary of a residential mortgage loan securitization trust considering its role as servicer and its retained subordinated interests in the trust. As a result, the Company has included the one-to-four family residential mortgage loans that were included in the trust in its consolidated financial statements. At December 31, 2013 and 2012, the carrying values of the loans in the securitization trust were $121 million and $151 million, respectively. The outstanding principal amount of mortgage-backed securities issued by the qualified special purpose trust that was held by parties unrelated to M&T at December 31, 2013 and 2012 was $18 million and $23 million, respectively. Because the transaction was non-recourse, the Company’s maximum exposure to loss as a result of its association with the trust at December 31, 2013 is limited to realizing the carrying value of the loans less the amount of the mortgage-backed securities held by third parties.
	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, 2013 and 2012, the Company included the Junior Subordinated Debentures as “long-term borrowings” in its consolidated balance sheet. The Company has recognized $34 million 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 $1.3 billion at December 31, 2013 and $1.5 billion at December 31, 2012. 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 $236 million, including $45 million of unfunded commitments, at December 31, 2013 and $270 million, including $71 million of unfunded commitments, at December 31, 2012. 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.

Fair_value_measurements

Fair value measurements	12 Months Ended
	Dec. 31, 2013
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, 2013.
	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 consist primarily of interest rate swap agreements 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 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.
	As discussed in note 3, the Company sold substantially all of its privately issued mortgage-backed securities classified as available for sale during the second quarter of 2013. In prior periods, the Company generally used model-based techniques to value such securities because the Company was significantly restricted in the level of market observable assumptions that could be relied upon. Specifically, market assumptions regarding credit adjusted cash flows and liquidity influences on discount rates were difficult to observe at the individual bond level. Because of the inactivity in the markets and the lack of observable valuation inputs, the Company classified the valuation of privately issued mortgage-backed securities as Level 3.
	The Company supplemented its determination of fair value for many of its privately issued mortgage-backed securities by obtaining pricing indications from two independent sources at December 31, 2012. However, the Company could not readily ascertain that the basis of such valuations could be ascribed to orderly and observable trades in the market for privately issued mortgage-backed securities. As a result, the Company also performed internal modeling to estimate the cash flows and fair value of privately issued mortgage-backed securities with an amortized cost basis of $1.1 billion at December 31, 2012. The Company’s internal modeling techniques included discounting estimated bond-specific cash flows using assumptions about cash flows associated with loans underlying each of the bonds, including estimates about the timing and amount of credit losses and prepayments. In estimating those cash flows, the Company used assumptions as to future delinquency, defaults, home price appreciation or depreciation and loss rates. To determine the point within the range of potential values that was most representative of fair value under current market conditions for each of the bonds, the Company averaged the internal model valuations and the indications obtained from the two independent pricing sources, such that the weighted-average reliance on internal model pricing for the bonds modeled was 33% with a 67% average weighting placed on the values provided by the independent sources. Significant unobservable inputs used in the Company’s modeling of fair value for mortgage-backed securities are included in the accompanying table of significant unobservable inputs to Level 3 measurements.
	Included in collateralized debt obligations are securities backed by trust preferred securities issued by financial institutions and other entities. The Company could not obtain pricing indications for many of these securities from its two primary independent pricing sources. The Company, therefore, performed internal modeling to estimate the cash flows and fair value of its portfolio of securities backed by trust preferred securities at December 31, 2013 and 2012. The modeling techniques included estimating cash flows using bond-specific assumptions about future collateral defaults and related loss severities. The resulting cash flows were then discounted by reference to market yields observed in the single-name trust preferred securities market. In determining a market yield applicable to the estimated cash flows, a margin over LIBOR, ranging from 5% to 11% with a weighted-average of 8% was used. Significant unobservable inputs used in the determination of estimated fair value of collateralized debt obligations are included in the accompanying table of significant unobservable inputs to Level 3 measurements. At December 31, 2013, the total amortized cost and fair value of securities backed by trust preferred securities issued by financial institutions and other entities were $42 million and $63 million, respectively, and at December 31, 2012 were $43 million and $62 million, respectively. Privately issued mortgage-backed securities and securities backed by trust preferred securities issued by financial institutions and other entities constituted all of the available-for-sale investment securities classified as Level 3 valuations.
	The Company ensures an appropriate control framework is in place over the valuation processes and techniques used for Level 3 fair value measurements. Internal pricing models used for significant valuation measurements have generally been subjected to validation procedures including testing of mathematical constructs, review of valuation methodology and significant assumptions used.
	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 are 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 assets and has considered its own credit risk in the valuation of its interest rate swap liabilities.
	The following tables present assets and liabilities at December 31, 2013 and 2012 measured at estimated fair value on a recurring basis:
			Fair Value			Level 1(a)			Level 2(a)			Level 3
			Measurements at
			December 31,
			2013
			(In thousands)
	Trading account assets		$	376,131			51,386			324,745			—
	Investment securities available for sale:
	U.S. Treasury and federal agencies			37,776			—			37,776			—
	Obligations of states and political subdivisions			10,811			—			10,811			—
	Mortgage-backed securities:
	Government issued or guaranteed			4,165,086			—			4,165,086			—
	Privately issued			1,850			—			—			1,850
	Collateralized debt obligations			63,083			—			—			63,083
	Other debt securities			120,085			—			120,085			—
	Equity securities			133,095			82,450			50,645			—
				4,531,786			82,450			4,384,403			64,933
	Real estate loans held for sale			468,650			—			468,650			—
	Other assets(b)			123,568			—			115,952			7,616
	Total assets		$	5,500,135			133,836			5,293,750			72,549
	Trading account liabilities		$	249,797			—			249,797			—
	Other liabilities(b)			4,392			—			717			3,675
	Total liabilities		$	254,189			—			250,514			3,675
			Fair Value			Level 1(a)			Level 2(a)			Level 3
			Measurements at
			December 31,
			2012
			(In thousands)
	Trading account assets		$	488,966			56,106			432,860			—
	Investment securities available for sale:
	U.S. Treasury and federal agencies			39,344			—			39,344			—
	Obligations of states and political subdivisions			20,901			—			20,901			—
	Mortgage-backed securities:
	Government issued or guaranteed			3,371,041			—			3,371,041			—
	Privately issued			1,023,886			—			—			1,023,886
	Collateralized debt obligations			61,869			—			—			61,869
	Other debt securities			111,950			—			111,950			—
	Equity securities			110,446			98,364			12,082			—
				4,739,437			98,364			3,555,318			1,085,755
	Real estate loans held for sale			1,387,491			—			1,387,491			—
	Other assets(b)			194,331			—			146,275			48,056
	Total assets		$	6,810,225			154,470			5,521,944			1,133,811
Trading account liabilities		$	374,274			—			374,274			—
Other liabilities(b)			10,592			—			10,395			197
Total liabilities		$	384,866			—			384,669			197
(a)	There were no significant transfers between Level 1 and Level 2 of the fair value hierarchy during the years ended December 31, 2013 and 2012.
(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 year ended December 31, 2013 were as follows:
		Investment Securities Available for Sale
		Privately Issued			Collateralized			Other
		Mortgage-			Debt			Assets  and
		backed			Obligations			Other
		Securities						Liabilities
		(In thousands)
Balance — January 1, 2013		$	1,023,886		$	61,869		$	47,859
Total gains (losses) realized/unrealized:
Included in earnings			(56,102	)(a)		—			97,845	(b)
Included in other comprehensive income			116,359	(e)		4,508	(e)		—
Sales			(978,608	)		—			—
Settlements			(103,685	)		(3,294	)		—
Transfers in and/or out of Level 3(c)			—			—			(141,763	)(d)
Balance — December 31, 2013		$	1,850		$	63,083		$	3,941
Changes in unrealized gains included in earnings related to assets still held at December 31, 2013		$	—		$	—		$	3,431	(b)
The changes in Level 3 assets and liabilities measured at estimated fair value on a recurring basis during the year ended December 31, 2012 were as follows:
		Investment Securities Available for Sale
		Privately			Collateralized			Other Assets
		Issued			Debt			and Other
		Mortgage-			Obligations			Liabilities
		backed
		Securities
		(In thousands)
Balance — January 1, 2012		$	1,151,285		$	52,500		$	6,923
Total gains (losses) realized/unrealized:
Included in earnings			(42,467	)(a)		—			212,281	(b)
Included in other comprehensive income			114,592	(e)		12,214	(e)		—
Settlements			(199,524	)		(2,845	)		—
Transfers in and/or out of Level 3(c)			—			—			(171,345	)(d)
Balance — December 31, 2012		$	1,023,886		$	61,869		$	47,859
Changes in unrealized gains (losses) included in earnings related to assets still held at December 31, 2012		$	(42,467	)(a)	$	—		$	47,859	(b)
The changes in Level 3 assets and liabilities measured at estimated fair value on a recurring basis during the year ended December 31, 2011 were as follows:
		Investment Securities Available for Sale
		Privately			Collateralized			Other
		Issued			Debt			Assets and
		Mortgage-			Obligations			Other
		backed						Liabilities
		Securities
		(In thousands)
Balance — January 1, 2011		$	1,457,968		$	110,756		$	2,244
Total gains (losses) realized/unrealized:
Included in earnings			(64,919	)(a)		19,231	(a)		67,163	(b)
Included in other comprehensive income			6,816	(e)		(272	)(e)		—
Purchases			—			50,790			—
Sales			—			(124,874	)		—
Settlements			(248,580	)		(3,131	)		—
Transfers in and/or out of Level 3(c)			—			—			(62,484	)(d)
Balance — December 31, 2011		$	1,151,285		$	52,500		$	6,923
Changes in unrealized gains (losses) included in earnings related to assets still held at December 31, 2011		$	(64,919	)(a)	$	—		$	6,902	(b)
(a)	Reported as an other-than-temporary impairment loss or as gain (loss) on bank investment securities in the consolidated statement of income.
(b)	Reported as mortgage banking revenues in the consolidated statement of income and includes the fair value of commitment issuances and expirations.
(c)	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.
(d)	Transfers out of Level 3 consist of interest rate locks transferred to closed loans.
(e)	Reported as net unrealized gains on investment securities in the consolidated statement of comprehensive income.
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.
Investment securities held to maturity
During 2012 and 2011, other-than-temporary losses of $5 million and $12 million, respectively, were recorded related to certain mortgage-backed securities. In accordance with GAAP, the carrying value of such securities was reduced to fair value, with estimated credit losses recognized in earnings and any remaining unrealized loss recognized in accumulated other comprehensive income. The determination of fair value included use of external and internal valuation sources that, as in the case of privately issued mortgage-backed securities, were weighted and averaged when estimating fair value. Due to the presence of significant unobservable inputs those valuations are classified as Level 3. The amortized cost, fair value and impact on the Company’s financial statements of the modeling described herein were not material. No such other-than-temporary losses were recorded in 2013.
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 20% to 90% at December 31, 2013. As these discounts are not readily observable and are considered significant, the valuations have been classified as Level 3. Loans subject to nonrecurring fair value measurement were $222 million at December 31, 2013, ($173 million and $49 million of which were classified as Level 2 and Level 3, respectively), $335 million at December 31, 2012 ($207 million and $128 million of which were classified as Level 2 and Level 3, respectively), and $419 million at December 31, 2011 ($262 million and $157 million of which were classified as Level 2 and Level 3, respectively). Changes in fair value recognized for partial charge-offs of loans and loan impairment reserves on loans held by the Company at the end of each of those years during each of the years ended December 31, 2013, 2012 and 2011 were decreases of $58 million, $67 million and $158 million, respectively.
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 $29 million and $34 million at December 31, 2013 and December 31, 2012, respectively. Changes in fair value recognized for foreclosed assets held by the Company at December 31, 2013, 2012 and 2011 were not material during each of 2013, 2012 and 2011.
Investment in Bayview Lending Group LLC
In 2011, the Company recognized a $79 million other-than-temporary impairment charge related to M&T’s 20% investment in BLG and charged it down to its estimated fair value at that time of $115 million. That impairment charge is included in “other costs of operations.” In determining the fair value of M&T’s investment in BLG at December 31, 2011, the Company projected no further commercial mortgage origination and securitization activities by BLG. BLG, however, is entitled to receive, if and when made, cash distributions from affiliates, a portion of which is contractually required to be distributed to M&T. Specifically, cash flows related to mortgage assets held by BLG and its affiliates were estimated using various assumptions on future default and loss severities to arrive at the expected amount of cash flow that could be available for distribution. As of December 31, 2011 the weighted-average assumptions of projected default percentage on the underlying mortgage loan collateral supporting those mortgage assets was 31% and the weighted-average loss severity assumption was 75%. With respect to projected value expected to be generated by the asset management and servicing operations of BLG’s affiliates, M&T developed estimates from company-provided forecasts of financial results and through discussions with their senior management pertaining to longer-term projections of growth in assets under management and asset servicing portfolios. M&T considered different scenarios of projected cash flows that could be generated by the asset management and servicing operations of BLG’s affiliates. M&T then discounted the various projections using discount rates that ranged from 8.0% to 12.5% that were determined by reference to returns required by investors in similar businesses. The determination of fair value of M&T’s 20% investment in BLG is considered a Level 3 valuation due to the unobservable nature of key assumptions. There was no other-than-temporary impairment charge recognized in 2013 or 2012 related to M&T’s investment in BLG.
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, 2013 and 2012:
		Fair Value at			Valuation		Unobservable	Range
		December 31,			Technique		Input/Assumptions	(Weighted-
		2013						Average)
		(In thousands)
Recurring fair value measurements
Privately issued mortgage–backed securities		$	1,850		Two independent pricing quotes		—	—
Collateralized debt obligations			63,083		Discounted cash flow		Probability of default	17%-55% (39%)
							Loss severity	100%
Net other assets (liabilities)(a)			3,941		Discounted cash flow		Commitment expirations	0%-90% (20%)
(a)	Other Level 3 assets (liabilities) consist of commitments to originate real estate loans.
		Fair Value at			Valuation		Unobservable	Range
		December 31,			Technique		Input/Assumptions	(Weighted-
		2012						Average)
		(In thousands)
Recurring fair value measurements
Privately issued mortgage–backed securities		$	1,023,886		Discounted cash flow		Probability of default	1%-40% (19%)
							Loss severity	32%-82% (51%)
Collateralized debt obligations			61,869		Discounted cash flow		Probability of default	22%-69% (47%)
							Loss severity	100%
Net other assets (liabilities)(a)			47,859		Discounted cash flow		Commitment expirations	0%-69% (20%)
(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 probability of default and loss severity for mortgage-backed securities and collateralized debt obligations backed by trust preferred securities would generally result in a lower (higher) fair value measurement.
An increase (decrease) in the estimate of expirations for commitments to originate residential mortgage 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
With the exception of marketable securities, certain off-balance sheet financial instruments and one-to-four family residential 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. Additional information about the assumptions and calculations utilized follows.
The carrying amounts and estimated fair value for financial instrument assets (liabilities) are presented in the following table:
		December 31, 2013
		Carrying			Estimated			Level 1			Level 2			Level 3
		Amount			Fair Value
		(In thousands)
Financial assets:
Cash and cash equivalents		$	1,672,934		$	1,672,934		$	1,596,877		$	76,057		$	—
Interest-bearing deposits at banks			1,651,138			1,651,138			—			1,651,138			—
Trading account assets			376,131			376,131			51,386			324,745			—
Investment securities			8,796,497			8,690,494			82,450			8,384,106			223,938
Loans and leases:
Commercial loans and leases			18,705,216			18,457,288			—			—			18,457,288
Commercial real estate loans			26,148,208			26,018,195			—			67,505			25,950,690
Residential real estate loans			8,928,221			8,867,872			—			5,432,207			3,435,665
Consumer loans			10,291,514			10,201,087			—			—			10,201,087
Allowance for credit losses			(916,676	)		—			—			—			—
Loans and leases, net			63,156,483			63,544,442			—			5,499,712			58,044,730
Accrued interest receivable			222,558			222,558			—			222,558			—
Financial liabilities:
Noninterest-bearing deposits		$	(24,661,007	)	$	(24,661,007	)		—		$	(24,661,007	)		—
Savings deposits and NOW accounts			(38,611,021	)		(38,611,021	)		—			(38,611,021	)		—
Time deposits			(3,523,838	)		(3,542,789	)		—			(3,542,789	)		—
Deposits at Cayman Islands office			(322,746	)		(322,746	)		—			(322,746	)		—
Short-term borrowings			(260,455	)		(260,455	)		—			(260,455	)		—
Long-term borrowings			(5,108,870	)		(5,244,902	)		—			(5,244,902	)		—
Accrued interest payable			(43,419	)		(43,419	)		—			(43,419	)		—
Trading account liabilities			(249,797	)		(249,797	)		—			(249,797	)		—
Other financial instruments:
Commitments to originate real estate loans for sale		$	3,941		$	3,941			—		$	—		$	3,941
Commitments to sell real estate loans			12,360			12,360			—			12,360			—
Other credit-related commitments			(118,886	)		(118,886	)		—			—			(118,886	)
Interest rate swap agreements used for interest rate risk management			102,875			102,875			—			102,875			—
		December 31, 2012
		Carrying			Estimated			Level 1			Level 2			Level 3
		Amount			Fair Value
		(In thousands)
Financial assets:
Cash and cash equivalents		$	1,986,615		$	1,986,615		$	1,895,423		$	91,192		$	—
Interest-bearing deposits at banks			129,945			129,945			—			129,945			—
Trading account assets			488,966			488,966			56,106			432,860			—
Investment securities			6,074,361			6,018,968			98,364			4,687,211			1,233,393
Loans and leases:
Commercial loans and leases			17,776,953			17,554,562			—			—			17,554,562
Commercial real estate loans			25,993,790			25,858,482			—			199,997			25,658,485
Residential real estate loans			11,240,837			11,381,319			—			8,100,915			3,280,404
Consumer loans			11,559,377			11,504,799			—			—			11,504,799
Allowance for credit losses			(925,860	)		—			—			—			—
Loans and leases, net			65,645,097			66,299,162			—			8,300,912			57,998,250
Accrued interest receivable			222,897			222,897			—			222,897			—
Financial liabilities:
Noninterest-bearing deposits		$	(24,240,802	)	$	(24,240,802	)		—		$	(24,240,802	)		—
Savings deposits and NOW accounts			(35,763,566	)		(35,763,566	)		—			(35,763,566	)		—
Time deposits			(4,562,366	)		(4,584,384	)		—			(4,584,384	)		—
Deposits at Cayman Islands office			(1,044,519	)		(1,044,519	)		—			(1,044,519	)		—
Short-term borrowings			(1,074,482	)		(1,074,482	)		—			(1,074,482	)		—
Long-term borrowings			(4,607,758	)		(4,768,408	)		—			(4,768,408	)		—
Accrued interest payable			(54,281	)		(54,281	)		—			(54,281	)		—
Trading account liabilities			(374,274	)		(374,274	)		—			(374,274	)		—
Other financial instruments:
Commitments to originate real estate loans for sale		$	47,859		$	47,859			—		$	—		$	47,859
Commitments to sell real estate loans			(7,299	)		(7,299	)		—			(7,299	)		—
Other credit-related commitments			(119,464	)		(119,464	)		—			—			(119,464	)
Interest rate swap agreements used for interest rate risk management			143,179			143,179			—			143,179			—
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 NOW accounts 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
	Dec. 31, 2013
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
		2013		2012
		(In thousands)
	Commitments to extend credit
	Home equity lines of credit	$	6,218,823	$	6,282,615
	Commercial real estate loans to be sold		62,386		139,929
	Other commercial real estate and construction		3,919,545		3,819,342
	Residential real estate loans to be sold		469,869		1,550,441
	Other residential real estate		384,617		445,268
	Commercial and other		10,419,545		10,070,711
	Standby letters of credit		3,600,528		4,025,329
	Commercial letters of credit		53,284		53,201
	Financial guarantees and indemnification contracts		2,457,633		2,120,361
	Commitments to sell real estate loans		854,656		2,625,408
	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 $2.3 billion and $2.0 billion at December 31, 2013 and 2012, 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 noncancellable operating lease agreements expiring at various dates over the next 25 years. Minimum lease payments under noncancellable operating leases are summarized in the following table:
		(In thousands)
	Year ending December 31:
	2014	$	85,923
	2015		80,237
	2016		66,265
	2017		52,793
	2018		43,593
	Later years		135,156
		$	463,967
	The Company has an agreement with the Baltimore Ravens of the National Football League whereby the Company obtained the naming rights to a football stadium in Baltimore, Maryland. Under the agreement, the Company is obligated to pay $6 million per year from 2014 through 2017.
	The Company reinsures credit life and accident and health insurance purchased by consumer loan customers. The Company also enters into reinsurance contracts with third party insurance companies who insure against the risk of a mortgage borrower’s payment default in connection with certain mortgage loans originated by the Company. When providing reinsurance coverage, the Company receives a premium in exchange for accepting a portion of the insurer’s risk of loss. The outstanding loan principal balances reinsured by the Company were approximately $19 million at December 31, 2013. Assets of subsidiaries providing reinsurance that are available to satisfy claims totaled approximately $36 million at December 31, 2013. The amounts noted above are not necessarily indicative of losses which may ultimately be incurred. Such losses are expected to be substantially less because most loans are repaid by borrowers in accordance with the original loan terms. Management believes that any reinsurance losses that may be payable by the Company will not be material to the Company’s consolidated financial position.
	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, 2013, management believes that any further liability arising out of the Company’s obligation to loan purchasers is not material to the Company’s consolidated financial position.
	M&T and its subsidiaries are subject in the normal course of business to various pending and threatened legal proceedings 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 legal 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
	Dec. 31, 2013
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 has been 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. The net effect of this allocation is recorded in the “All Other” category. 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. 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. 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, 2013, 2012 and 2011
			Business Banking									Commercial Banking						Commercial Real Estate									Discretionary Portfolio
			2013			2012			2011			2013		2012		2011		2013			2012			2011			2013			2012			2011
	Net interest income(a)		$	325,521		$	347,067		$	334,811		$	758,231	$	753,678	$	655,407	$	570,786		$	531,398		$	467,683		$	66,157		$	66,303		$	63,030
	Noninterest income			102,945			103,283			95,429			263,766		253,808		249,150		130,895			133,120			99,409			(2,126	)		(76,113	)		98,770
				428,466			450,350			430,240			1,021,997		1,007,486		904,557		701,681			664,518			567,092			64,031			(9,810	)		161,800
	Provision for credit losses			26,450			22,245			45,689			76,818		15,781		29,823		7,365			4,238			58,474			16,670			44,305			59,309
	Amortization of core deposit and other intangible assets			—			—			—			—		—		—		—			—			—			—			—			—
	Depreciation and other amortization			198			122			140			564		567		553		14,296			11,004			9,054			1,330			2,065			2,859
	Other noninterest expense			214,043			179,428			177,172			288,842		262,820		248,428		214,246			190,879			154,042			30,431			31,006			32,262
	Income (loss) before taxes			187,775			248,555			207,239			655,773		728,318		625,753		465,774			458,397			345,522			15,600			(87,186	)		67,370
	Income tax expense (benefit)			76,735			101,484			84,532			264,433		296,894		256,311		143,981			149,321			105,709			(14,368	)		(54,071	)		7,975
	Net income (loss)		$	111,040		$	147,071		$	122,707		$	391,340	$	431,424	$	369,442	$	321,793		$	309,076		$	239,813		$	29,968		$	(33,115	)	$	59,395
	Average total assets (in millions)		$	5,080		$	4,909		$	5,192		$	21,655	$	19,946	$	17,650	$	17,150		$	16,437		$	15,025		$	16,480		$	16,583		$	14,170
	Capital expenditures (in millions)		$	1		$	—		$	—		$	—	$	—	$	—	$	—		$	—		$	—		$	—		$	—		$	—
												For the Years Ended December 31, 2013, 2012 and 2011
			Residential Mortgage									Retail Banking						All Other									Total
			Banking
			2013			2012			2011			2013		2012		2011		2013			2012			2011			2013			2012			2011
	Net interest income(a)		$	98,496		$	78,058		$	63,951		$	810,134	$	902,906	$	851,332	$	43,904		$	(80,894	)	$	(46,458	)	$	2,673,229		$	2,598,516		$	2,389,756
	Noninterest income			325,474			402,211			184,249			373,362		349,571		366,042		670,889			501,390			489,863			1,865,205			1,667,270			1,582,912
				423,970			480,269			248,200			1,183,496		1,252,477		1,217,374		714,793			420,496			443,405			4,538,434			4,265,786			3,972,668
	Provision for credit losses			(11,711	)		17,169			36,375			72,502		95,345		101,679		(3,094	)		4,917			(61,349	)		185,000			204,000			270,000
	Amortization of core deposit and other intangible assets			—			—			—			—		—		—		46,912			60,631			61,617			46,912			60,631			61,617
	Depreciation and other amortization			48,716			46,902			44,349			34,599		32,734		33,713		57,120			50,536			45,495			156,823			143,930			136,163
	Other noninterest expense			225,794			195,604			151,945			768,644		751,916		744,905		690,150			693,046			771,534			2,432,150			2,304,699			2,280,288
	Income (loss) before taxes			161,171			220,594			15,531			307,751		372,482		337,077		(76,295	)		(388,634	)		(373,892	)		1,717,549			1,552,526			1,224,600
	Income tax expense (benefit)			61,779			85,671			2,403			125,350		151,616		137,161		(78,841	)		(207,887	)		(228,970	)		579,069			523,028			365,121
	Net income (loss)		$	99,392		$	134,923		$	13,128		$	182,401	$	220,866	$	199,916	$	2,546		$	(180,747	)	$	(144,922	)	$	1,138,480		$	1,029,498		$	859,479
	Average total assets (in millions)		$	2,858		$	2,451		$	1,958		$	10,997	$	11,705	$	11,940	$	9,442		$	7,952		$	8,042		$	83,662		$	79,983		$	73,977
	Capital expenditures (in millions)		$	—		$	1		$	—		$	40	$	15	$	25	$	89		$	76		$	45		$	130		$	92		$	70
	(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 $24,971,000 in 2013, $26,391,000 in 2012 and $25,876,000 in 2011 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. The Discretionary Portfolio segment includes securities, residential mortgage loans and other assets; short-term and long-term borrowed funds; brokered certificates of deposit and interest rate swap agreements related thereto; and Cayman Islands branch deposits. This segment also provides foreign exchange services to customers. The Residential Mortgage Banking segment originates and services residential mortgage loans for consumers and sells substantially all of those 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 mortgage 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, telephone banking and Internet banking. 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
			2013			2012			2011
			(In thousands)
	Revenues		$	(50,128	)	$	(71,452	)	$	(64,239	)
	Expenses			(16,235	)		(17,313	)		(14,146	)
	Income taxes (benefit)			(13,791	)		(22,029	)		(20,383	)
	Net income (loss)			(20,102	)		(32,110	)		(29,710	)
	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
	Dec. 31, 2013
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, 2013, approximately $1.11 billion was available for payment of dividends to M&T from banking subsidiaries. Additionally, the Federal Reserve Board requires bank holding companies with $50 billion or more of total consolidated assets to submit annual capital plans. Such bank holding companies may pay dividends and repurchase stock only in accordance with a capital plan which the Federal Reserve Board has not objected to.
	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 noninterest-earning reserves against certain deposit liabilities. During the maintenance periods that included December 31, 2013 and 2012, cash and due from banks included a daily average of $595,593,000 and $604,789,000, respectively, for such purpose.
	Federal regulators have adopted capital adequacy guidelines for bank holding companies and banks. 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. Under the capital adequacy guidelines, the so-called “Tier 1 capital” and “Total capital” as a percentage of risk-weighted assets and certain off-balance sheet financial instruments must be at least 4% and 8%, respectively. In addition to these risk-based measures, regulators also require banking institutions that meet certain qualitative criteria to maintain a minimum “leverage” ratio of “Tier 1 capital” to average total assets, adjusted for goodwill and certain other items, of at least 3% to be considered adequately capitalized. As of December 31, 2013, M&T and each of its banking subsidiaries exceeded all applicable capital adequacy requirements. To be considered “well capitalized,” under the regulatory framework for prompt corrective action, a banking institution must maintain Tier 1 risk-based capital, total risk-based capital and leverage ratios of at least 6%, 10% and 5%, respectively.
	The capital ratios and amounts of the Company and its banking subsidiaries as of December 31, 2013 and 2012 are presented below:
			M&T			M&T Bank			Wilmington
			(Consolidated)						Trust, N.A.
			(Dollars in thousands)
	December 31, 2013:
	Tier 1 capital
	Amount		$	8,792,035		$	7,341,506		$	420,330
	Ratio(a)			12	%		10.08	%		73.79	%
	Minimum required amount(b)			2,930,925			2,914,246			22,786
	Total capital
	Amount			11,045,589			9,445,770			424,975
	Ratio(a)			15.07	%		12.96	%		74.6	%
	Minimum required amount(b)			5,861,849			5,828,491			45,573
	Leverage
	Amount			8,792,035			7,341,506			420,330
	Ratio(c)			10.78	%		9.09	%		19.8	%
	Minimum required amount(b)			2,446,476			2,422,096			63,678
	December 31, 2012:
	Tier 1 capital
	Amount		$	7,810,196		$	6,767,774		$	405,469
	Ratio(a)			10.22	%		8.92	%		61.02	%
	Minimum required amount(b)			3,057,093			3,034,184			26,580
	Total capital
	Amount			10,230,302			8,981,931			410,873
	Ratio(a)			13.39	%		11.84	%		61.83	%
	Minimum required amount(b)			6,114,186			6,068,367			53,160
	Leverage
	Amount			7,810,196			6,767,774			405,469
	Ratio(c)			10.07	%		8.84	%		21.62	%
	Minimum required amount(b)			2,327,122			2,297,902			56,275
	(a)	The ratio of capital to risk-weighted assets, as defined by regulation.
	(b)	Minimum amount of capital to be considered adequately capitalized, as defined by regulation.
	(c)	The ratio of capital to average assets, as defined by regulation.

Relationship_with_Bayview_Lend

Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P.	12 Months Ended
	Dec. 31, 2013
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% interest in BLG, a privately-held commercial mortgage company. The carrying value of that investment was $74 million at December 31, 2013. M&T recognizes income or loss from BLG using the equity method of accounting. In 2011, the Company recognized a $79 million other-than-temporary impairment charge related to its investment in BLG that is included in “other costs of operations.” Further information concerning the other-than-temporary impairment charge is provided in note 20.
	Bayview Financial Holdings, L.P. (together with its affiliates, “Bayview Financial”), a privately-held specialty mortgage finance 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 $5.5 billion and $6.5 billion at December 31, 2013 and 2012, respectively. Revenues from those servicing rights were $31 million, $35 million and $41 million during 2013, 2012 and 2011, respectively. The Company sub-services residential mortgage loans for Bayview Financial having outstanding principal balances totaling $45.6 billion and $11.4 billion at December 31, 2013 and 2012, respectively. Revenues earned for sub-servicing loans for Bayview Financial were $33 million in 2013, $10 million in 2012 and $477 thousand in 2011. In addition, the Company held $2 million and $11 million at December 31, 2013 and 2012, respectively, of mortgage-backed securities in its available-for-sale investment securities portfolio that were securitized by Bayview Financial. Finally, the Company held $220 million and $242 million of similar investment securities in its held-to-maturity portfolio at December 31, 2013 and 2012, respectively.

Parent_company_financial_state

Parent company financial statements	12 Months Ended
	Dec. 31, 2013
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]	'
Parent company financial statements	'
	25.    Parent company financial statements
	Condensed Balance Sheet
			December 31
			2013			2012
			(In thousands)
	Assets
	Cash in subsidiary bank		$	10,729		$	4,774
	Due from consolidated bank subsidiaries
	Money-market savings			968,274			714,677
	Current income tax receivable			1,914			1,835
	Other			1,894			—
	Total due from consolidated bank subsidiaries			972,082			716,512
	Investments in consolidated subsidiaries
	Banks and bank holding company			11,364,657			10,495,557
	Other			16,212			16,344
	Investments in unconsolidated subsidiaries (note 19)			33,751			33,916
	Investment in Bayview Lending Group LLC			73,883			93,489
	Other assets			80,098			83,975
	Total assets		$	12,551,412		$	11,444,567
	Liabilities
	Due to consolidated bank subsidiaries		$	—		$	213
	Accrued expenses and other liabilities			62,817			60,619
	Long-term borrowings			1,183,063			1,181,142
	Total liabilities			1,245,880			1,241,974
	Shareholders’ equity			11,305,532			10,202,593
	Total liabilities and shareholders’ equity		$	12,551,412		$	11,444,567
	Condensed Statement of Income
			Year Ended December 31
			2013			2012			2011
			(In thousands, except per share)
	Income
	Dividends from consolidated bank subsidiaries		$	700,000		$	700,000		$	715,000
	Equity in earnings of Bayview Lending Group LLC			(16,126	)		(21,511	)		(24,231	)
	Other income			9,992			8,755			67,829
	Total income			693,866			687,244			758,598
	Expense
	Interest on long-term borrowings			73,115			82,286			90,959
	Other expense (a)			15,994			19,226			87,368
	Total expense			89,109			101,512			178,327
	Income before income taxes and equity in undistributed income of subsidiaries			604,757			585,732			580,271
	Income tax credits			35,986			43,149			50,460
	Income before equity in undistributed income of subsidiaries			640,743			628,881			630,731
	Equity in undistributed income of subsidiaries
	Net income of subsidiaries			1,197,737			1,100,617			943,748
	Less: dividends received			(700,000	)		(700,000	)		(715,000	)
	Equity in undistributed income of subsidiaries			497,737			400,617			228,748
	Net income		$	1,138,480		$	1,029,498		$	859,479
	Net income per common share
	Basic		$	8.26		$	7.57		$	6.37
	Diluted			8.2			7.54			6.35
	(a)	In 2011 includes $79 million write-down of Investment in Bayview Lending Group LLC.
	Condensed Statement of Cash Flows
			Year Ended December 31
			2013			2012			2011
			(In thousands)
	Cash flows from operating activities
	Net income		$	1,138,480		$	1,029,498		$	859,479
	Adjustments to reconcile net income to net cash provided by operating activities
	Equity in undistributed income of subsidiaries			(497,737	)		(400,617	)		(228,748	)
	Provision for deferred income taxes			1,535			1,724			(10,349	)
	Asset write-downs			—			—			79,012
	Net change in accrued income and expense			31,979			6,798			44,336
	Net cash provided by operating activities			674,257			637,403			743,730
Cash flows from investing activities
Proceeds from sales of investment securities			—			411			1,987
Proceeds from maturities of investment securities			—			—			4,400
Investment in subsidiary			(140,000	)		—			—
Purchase of Wilmington Trust Corporation preferred stock			—			—			(330,000	)
Other, net			3,295			324			2,833
Net cash provided (used) by investing activities			(136,705	)		735			(320,780	)
Cash flows from financing activities
Payments on long-term borrowings			—			(300,000	)		—
Dividends paid — common			(365,349	)		(357,717	)		(350,129	)
Dividends paid — preferred			(53,450	)		(53,450	)		(48,203	)
Proceeds from issuance of preferred stock			—			—			495,000
Redemption of preferred stock			—			—			(370,000	)
Other, net			140,799			143,352			16,386
Net cash used by financing activities			(278,000	)		(567,815	)		(256,946	)
Net increase in cash and cash equivalents			259,552			70,323			166,004
Cash and cash equivalents at beginning of year			719,451			649,128			483,124
Cash and cash equivalents at end of year		$	979,003		$	719,451		$	649,128
Supplemental disclosure of cash flow information
Interest received during the year		$	2,224		$	1,970		$	2,082
Interest paid during the year			71,090			80,090			87,184
Income taxes received during the year			45,237			21,878			57,964

Significant_accounting_policie1

Significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2013
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.
	The cost basis of individual securities is written down through a charge to earnings when declines in value below amortized cost 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. The cost basis of individual equity securities is written down to estimated fair value through a charge to earnings when declines in value below cost are considered to be other than temporary. 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 recorded at fair value with no carry-over of an acquired entity’s previously established allowance for credit losses. 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.
	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.
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 acquired loans 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. 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 market 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 that is expected to vest, 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.
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.
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.

Acquisitions_Tables

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2013
Business Combinations [Abstract]	'
Pro Forma Information	'
	Additionally, the Company has achieved further operating cost savings and other business synergies as a result of the acquisition which are not reflected in the pro forma amounts that follow.
			Actual Since		Pro Forma
			Acquisition		Year Ended
			Through		December 31, 2011
			December 31, 2011
			(In thousands)
	Total revenues(a)		$	380,945	$	4,202,109
	Net income			18,586		808,696
	(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, 2013, 2012 and 2011 follows:
			2013		2012		2011
			(In thousands)
	Salaries and employee benefits		$	836	$	4,997	$	16,131
	Equipment and net occupancy			690		15		412
	Printing, postage and supplies			1,825		—		2,663
	Other costs of operations			9,013		4,867		64,481
			$	12,364	$	9,879	$	83,687

Investment_securities_Tables

Investment securities (Tables)	12 Months Ended
	Dec. 31, 2013
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			Gross			Gross			Estimated
		Cost			Unrealized			Unrealized			Fair Value
					Gains			Losses
		(In thousands)
	December 31, 2013
	Investment securities available for sale:
	U.S. Treasury and federal agencies	$	37,396		$	382		$	2		$	37,776
	Obligations of states and political subdivisions		10,484			333			6			10,811
	Mortgage-backed securities:
	Government issued or guaranteed		4,123,435			61,001			19,350			4,165,086
	Privately issued		1,468			387			5			1,850
	Collateralized debt obligations		42,274			21,666			857			63,083
	Other debt securities		137,828			1,722			19,465			120,085
	Equity securities		91,480			41,842			227			133,095
			4,444,365			127,333			39,912			4,531,786
	Investment securities held to maturity:
	Obligations of states and political subdivisions		169,684			3,744			135			173,293
	Mortgage-backed securities:
	Government issued or guaranteed		3,567,905			16,160			65,149			3,518,916
	Privately issued		219,628			—			60,623			159,005
	Other debt securities		8,913			—			—			8,913
			3,966,130			19,904			125,907			3,860,127
	Other securities		298,581			—			—			298,581
	Total	$	8,709,076		$	147,237		$	165,819		$	8,690,494
	December 31, 2012
	Investment securities available for sale:
	U.S. Treasury and federal agencies	$	38,422		$	922		$	—		$	39,344
	Obligations of states and political subdivisions		20,375			534			8			20,901
	Mortgage-backed securities:
	Government issued or guaranteed		3,163,210			208,060			229			3,371,041
	Privately issued		1,142,287			7,272			125,673			1,023,886
	Collateralized debt obligations		43,228			19,663			1,022			61,869
	Other debt securities		136,603			2,247			26,900			111,950
	Equity securities		98,945			14,921			3,420			110,446
			4,643,070			253,619			157,252			4,739,437
	Investment securities held to maturity:
	Obligations of states and political subdivisions		182,103			7,647			27			189,723
	Mortgage-backed securities:
	Government issued or guaranteed		597,340			31,727			—			629,067
	Privately issued		242,378			160			94,900			147,638
	Other debt securities		10,455			—			—			10,455
			1,032,276			39,534			94,927			976,883
	Other securities		302,648			—			—			302,648
	Total	$	5,977,994		$	293,153		$	252,179		$	6,018,968
Investment Ratings of All Privately Issued Mortgage-Backed Securities, Collateralized Debt Obligations and Other Debt Securities	'
	As of December 31, 2013, the latest available investment ratings of all obligations of states and political subdivisions, privately issued mortgage-backed securities, collateralized debt obligations and other debt securities were:
		Amortized			Estimated			Average Credit Rating of Fair Value Amount
		Cost			Fair Value			A or Better			BBB			BB		B or Less		Not Rated
		(In thousands)
	Obligations of states and political subdivisions	$	180,168		$	184,104		$	152,704		$	6,359		$	200	$	—	$	24,841
	Privately issued mortgage-backed     securities		221,096			160,855			56,731			—			—		104,000		124
	Collateralized debt obligations		42,274			63,083			11,005			3,684			8,904		39,490		—
	Other debt securities		146,741			128,998			12,073			56,481			28,966		21,300		10,178
	Total	$	590,279		$	537,040		$	232,513		$	66,524		$	38,070	$	164,790	$	35,143
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
		2013			2012
		(In thousands)
	Collateralized mortgage obligations:
	Amortized cost	$	231,040		$	1,414,691
	Estimated fair value		171,100			1,202,243
Changes in Credit Losses Associated with Debt Securities for Which Other-Than-Temporary Impairment Losses	'
	Changes in credit losses during 2013, 2012 and 2011 associated with debt securities for which other-than-temporary impairment losses have been recognized in earnings follows:
		Year Ended December 31
		2013			2012			2011
		(In thousands)
	Estimated credit losses — beginning balance	$	197,809		$	285,399		$	327,912
	Additions for credit losses not previously recognized		9,800			47,822			77,035
	Reductions for increases in cash flows		—			—			(5,111	)
	Reductions for realized losses		(207,441	)		(135,412	)		(114,437	)
	Estimated credit losses — ending balance	$	168		$	197,809		$	285,399
Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity	'
	At December 31, 2013, the amortized cost and estimated fair value of debt securities by contractual maturity were as follows:
		Amortized			Estimated
		Cost			Fair Value
		(In thousands)
	Debt securities available for sale:
	Due in one year or less	$	29,839		$	30,036
	Due after one year through five years		16,005			16,617
	Due after five years through ten years		7,718			8,015
	Due after ten years		174,420			177,087
			227,982			231,755
	Mortgage-backed securities available for sale		4,124,903			4,166,936
		$	4,352,885		$	4,398,691
	Debt securities held to maturity:
	Due in one year or less	$	19,485		$	19,606
	Due after one year through five years		68,713			70,618
	Due after five years through ten years		81,486			83,069
	Due after ten years		8,913			8,913
			178,597			182,206
	Mortgage-backed securities held to maturity		3,787,533			3,677,921
		$	3,966,130		$	3,860,127
Investment Securities in Continuous Unrealized Loss Position	'
	A summary of investment securities that as of December 31, 2013 and 2012 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			Fair Value			Unrealized
					Losses						Losses
		(In thousands)
	December 31, 2013
	Investment securities available for sale:
	U.S. Treasury and federal agencies	$	745		$	(2	)	$	—		$	—
	Obligations of states and political subdivisions		—			—			558			(6	)
	Mortgage-backed securities:
	Government issued or guaranteed		1,697,094			(19,225	)		5,815			(125	)
	Privately issued		—			—			98			(5	)
	Collateralized debt obligations		—			—			6,257			(857	)
	Other debt securities		1,428			(4	)		103,602			(19,461	)
	Equity securities		159			(227	)		—			—
			1,699,426			(19,458	)		116,330			(20,454	)
	Investment securities held to maturity:
	Obligations of states and political subdivisions		13,517			(120	)		1,558			(15	)
	Mortgage-backed securities:
	Government issued or guaranteed		2,629,950			(65,149	)		—			—
	Privately issued		—			—			159,005			(60,623	)
			2,643,467			(65,269	)		160,563			(60,638	)
	Total	$	4,342,893		$	(84,727	)	$	276,893		$	(81,092	)
	December 31, 2012
	Investment securities available for sale:
	Obligations of states and political subdivisions	$	166		$	(1	)	$	683		$	(7	)
	Mortgage-backed securities:
	Government issued or guaranteed		12,107			(65	)		8,804			(164	)
	Privately issued		121,487			(692	)		774,328			(124,981	)
	Collateralized debt obligations		—			—			6,043			(1,022	)
	Other debt securities		—			—			95,685			(26,900	)
	Equity securities		5,535			(1,295	)		2,956			(2,125	)
			139,295			(2,053	)		888,499			(155,199	)
	Investment securities held to maturity:
	Obligations of states and political subdivisions		1,026			(5	)		3,558			(22	)
	Privately issued mortgage-backed securities		—			—			147,273			(94,900	)
			1,026			(5	)		150,831			(94,922	)
	Total	$	140,321		$	(2,058	)	$	1,039,330		$	(250,121	)

Loans_and_leases_Tables

Loans and leases (Tables)	12 Months Ended
	Dec. 31, 2013
Receivables [Abstract]	'
Total Loans and Leases Outstanding	'
	Total loans and leases outstanding were comprised of the following:
			December 31
			2013			2012
			(In thousands)
	Loans
	Commercial, financial, etc.		$	17,477,238		$	16,500,202
	Real estate:
	Residential			8,911,554			11,161,323
	Commercial			21,799,886			22,333,036
	Construction			4,457,650			3,772,413
	Consumer			10,280,527			11,550,274
	Total loans			62,926,855			65,317,248
	Leases
	Commercial			1,398,928			1,472,938
	Total loans and leases			64,325,783			66,790,186
	Less: unearned discount			(252,624	)		(219,229	)
	Total loans and leases, net of unearned discount		$	64,073,159		$	66,570,957
Outstanding Principal Balance and Carrying Amount of Loans that is Included in Consolidated Balance Sheet	'
	The outstanding principal balance and the carrying amount of acquired loans that were recorded at fair value at the acquisition date that is included in the consolidated balance sheet were as follows:
			December 31
			2013			2012
			(In thousands)
	Outstanding principal balance		$	4,656,811		$	6,705,120
	Carrying amount:
	Commercial, financial, leasing, etc.			580,685			928,107
	Commercial real estate			1,541,368			2,567,050
	Residential real estate			576,473			707,309
	Consumer			1,308,926			1,637,887
			$	4,007,452		$	5,840,353
Summary of Changes in Accretable Yield for Acquired Loans	'
	A summary of changes in the accretable yield for acquired loans for the years ended December 31, 2013, 2012 and 2011 follows:
	For Year Ended December 31,		2013						2012						2011
			Purchased			Other			Purchased			Other			Purchased			Other
			Impaired			Acquired			Impaired			Acquired			Impaired			Acquired
			(In thousands)
	Balance at beginning of period		$	42,252		$	638,272		$	30,805		$	807,960		$	9,245		$	447,505
	Additions			—			—			—			—			39,358			648,631
	Interest income			(36,727	)		(247,295	)		(40,551	)		(295,654	)		(26,221	)		(268,315	)
	Reclassifications from nonaccretable balance, net			31,705			149,595			51,998			148,490			8,629			1,800
	Other(a)			—			(1,939	)		—			(22,524	)		(206	)		(21,661	)
	Balance at end of period		$	37,230		$	538,633		$	42,252		$	638,272		$	30,805		$	807,960
	(a)	Other changes in expected cash flows including changes in interest rates and prepayment assumptions.
Summary of Current, Past Due and Nonaccrual Loans	'
	A summary of current, past due and nonaccrual loans as of December 31, 2013 and 2012 follows:
									90 Days or More Past
									Due and Accruing
			Current			30-89 Days			Non-			Acquired(a)			Purchased			Nonaccrual			Total
						Past Due			acquired						Impaired(b)
			(In thousands)
	December 31, 2013
	Commercial, financial, leasing, etc.		$	18,489,474		$	77,538		$	4,981		$	6,778		$	15,706		$	110,739		$	18,705,216
	Real estate:
	Commercial			21,236,071			145,749			63,353			35,603			88,034			173,048			21,741,858
	Residential builder and developer			1,025,984			8,486			141			7,930			137,544			96,427			1,276,512
	Other commercial construction			2,986,598			42,234			—			8,031			57,707			35,268			3,129,838
	Residential			7,630,368			295,131			294,649			43,700			29,184			252,805			8,545,837
	Residential Alt-A			283,253			18,009			—			—			—			81,122			382,384
	Consumer:
	Home equity lines and loans			5,972,365			40,537			—			27,754			2,617			78,516			6,121,789
	Automobile			1,314,246			29,144			—			366			—			21,144			1,364,900
	Other			2,726,522			47,830			5,386			—			—			25,087			2,804,825
	Total		$	61,664,881		$	704,658		$	368,510		$	130,162		$	330,792		$	874,156		$	64,073,159
	December 31, 2012
	Commercial, financial, leasing, etc.		$	17,511,052		$	62,479		$	23,490		$	10,587		$	17,437		$	151,908		$	17,776,953
	Real estate:
	Commercial			21,759,997			118,249			13,111			54,995			132,962			193,859			22,273,173
	Residential builder and developer			757,311			35,419			3,258			23,909			187,764			181,865			1,189,526
	Other commercial construction			2,379,953			35,274			509			9,572			68,971			36,812			2,531,091
	Residential			9,811,956			337,969			313,184			45,124			36,769			249,314			10,794,316
	Residential Alt-A			331,021			19,692			—			—			—			95,808			446,521
	Consumer:
	Home equity lines and loans			6,199,591			40,759			—			20,318			3,211			58,071			6,321,950
	Automobile			2,442,502			40,461			—			251			—			25,107			2,508,321
	Other			2,661,432			40,599			4,845			1,798			—			20,432			2,729,106
	Total		$	63,854,815		$	730,901		$	358,397		$	166,554		$	447,114		$	1,013,176		$	66,570,957
	(a)	Acquired loans that were recorded at fair value at acquisition date. This category does not include purchased impaired loans that are presented separately.
	(b)	Accruing loans that were impaired at acquisition date and were recorded at fair value.
Loan Modification Activities that were Considered Troubled Debt Restructurings	'
	The table below summarizes the Company’s loan modification activities that were considered troubled debt restructurings for the year ended December 31, 2013:
						Recorded Investment						Financial Effects of
												Modification
			Number			Pre-			Post-			Recorded			Interest
						modifica-			modifica-			Investment			(b)
						tion			tion			(a)
			(Dollars in thousands)
	Commercial, financial, leasing, etc.
	Principal deferral			79		$	16,389		$	16,002		$	(387	)	$	—
	Interest rate reduction			1			104			335			231			(54	)
	Other			4			50,433			50,924			491			—
	Combination of concession types			11			6,229			5,578			(651	)		(458	)
	Real estate:
	Commercial
	Principal deferral			27			40,639			40,464			(175	)		—
	Other			2			449			475			26			—
	Combination of concession types			9			2,649			3,040			391			(250	)
	Residential builder and developer
	Principal deferral			18			21,423			20,577			(846	)		—
	Other			1			4,039			3,888			(151	)		—
	Combination of concession types			3			15,580			15,514			(66	)		(535	)
	Other commercial construction
	Principal deferral			3			590			521			(69	)		—
	Residential
	Principal deferral			32			3,556			3,821			265			—
	Other			1			195			195			—			—
	Combination of concession types			61			73,940			70,854			(3,086	)		(924	)
	Residential Alt-A
	Principal deferral			10			1,900			1,880			(20	)		—
	Combination of concession types			19			2,826			3,148			322			(790	)
	Consumer:
	Home equity lines and loans
	Principal deferral			10			859			861			2			—
	Interest rate reduction			1			99			99			—			(8	)
	Other			1			106			106			—			—
	Combination of concession types			28			2,190			2,190			—			(270	)
	Automobile
	Principal deferral			460			6,148			6,148			—			—
	Interest rate reduction			15			235			235			—			(22	)
	Other			78			339			339			—			—
	Combination of concession types			225			2,552			2,552			—			(191	)
	Other
	Principal deferral			36			332			332			—			—
	Interest rate reduction			1			12			12			—			(2	)
	Other			2			14			14			—			—
	Combination of concession types			120			4,248			4,248			—			(1,187	)
	Total			1,258		$	258,075		$	254,352		$	(3,723	)	$	(4,691	)
	(a)	Financial effects impacting the recorded investment included principal payments or advances, charge-offs and capitalized escrow arrearages.
	(b)	Represents the present value of interest rate concessions discounted at the effective rate of the original loan.
	The table below summarizes the Company’s loan modification activities that were considered troubled debt restructurings for the year ended December 31, 2012:
						Recorded Investment						Financial Effects of
												Modification
			Number			Pre-			Post-			Recorded			Interest
						modifica-			modifica-			Investment			(b)
						tion			tion			(a)
			(Dollars in thousands)
	Commercial, financial, leasing, etc.
	Principal deferral			61		$	23,888		$	22,456		$	(1,432	)	$	—
	Other			3			2,967			3,052			85			—
	Combination of concession types			5			628			740			112			(102	)
	Real estate:
	Commercial
	Principal deferral			24			22,855			23,059			204			—
Interest rate reduction			2			665			708			43			(129	)
Combination of concession types			7			1,637			1,656			19			(351	)
Residential builder and developer
Principal deferral			23			36,868			34,740			(2,128	)		—
Combination of concession types			7			37,602			36,148			(1,454	)		—
Other commercial construction
Principal deferral			6			81,062			79,312			(1,750	)		—
Residential
Principal deferral			36			4,643			4,808			165			—
Interest rate reduction			1			109			109			—			(20	)
Combination of concession types			62			12,886			13,146			260			(657	)
Residential Alt-A
Principal deferral			7			968			989			21			—
Combination of concession types			38			8,525			8,717			192			(159	)
Consumer:
Home equity lines and loans
Principal deferral			15			1,285			1,285			—			—
Interest rate reduction			1			144			144			—			(6	)
Combination of concession types			29			2,332			2,332			—			(368	)
Automobile
Principal deferral			618			8,347			8,347			—			—
Interest rate reduction			22			328			328			—			(24	)
Other			67			300			300			—			—
Combination of concession types			375			5,857			5,857			—			(684	)
Other
Principal deferral			80			1,201			1,201			—			—
Interest rate reduction			22			515			515			—			(85	)
Other			13			54			54			—			—
Combination of concession types			84			1,015			1,015			—			(268	)
Total			1,608		$	256,681		$	251,018		$	(5,663	)	$	(2,853	)
(a)	Financial effects impacting the recorded investment included principal payments or advances, charge-offs and capitalized escrow arrearages.
(b)	Represents the present value of interest rate concessions discounted at the effective rate of the original loan.
The table below summarizes the Company’s loan modification activities that were considered troubled debt restructurings for the year ended December 31, 2011:
					Recorded Investment						Financial Effects of
											Modification
		Number			Pre-			Post-			Recorded			Interest
					modifica-			modifica-			Investment			(b)
					tion			tion			(a)
		(Dollars in thousands)
Commercial, financial, leasing, etc.
Principal deferral			53		$	10,703		$	10,778		$	75		$	—
Combination of concession types			3			2,049			2,046			(3	)		(654	)
Real estate:
Commercial
Principal deferral			29			16,804			16,704			(100	)		—
Combination of concession types			3			15,778			15,777			(1	)		(1,463	)
Residential builder and developer
Principal deferral			9			33,208			26,811			(6,397	)		—
Other			6			118,114			110,156			(7,958	)		—
Combination of concession types			5			2,540			2,561			21			—
Other commercial construction
Principal deferral			3			8,436			8,553			117			—
Combination of concession types			3			65,813			60,973			(4,840	)		—
Residential
Principal deferral			37			8,175			8,235			60			—
Interest rate reduction			14			1,926			1,991			65			(318	)
Combination of concession types			111			19,508			19,934			426			(1,559	)
Residential Alt-A
Principal deferral			3			800			835			35			—
Combination of concession types			34			6,813			6,978			165			(889	)
Consumer:
Home equity lines and loans
Principal deferral			3			259			259			—			—
Other			3			86			86			—			—
Combination of concession types			26			2,156			2,158			2			(444	)
Automobile
Principal deferral			746			10,053			10,053			—			—
Interest rate reduction			17			183			183			—			(13	)
Other			111			739			739			—			—
Combination of concession types			431			6,703			6,703			—			(808	)
Other
Principal deferral			23			400			400			—			—
Interest rate reduction			1			8			8			—			(1	)
Other			4			103			103			—			—
Combination of concession types			102			803			803			—			(189	)
Total			1,780		$	332,160		$	313,827		$	(18,333	)	$	(6,338	)
(a)	Financial effects impacting the recorded investment included principal payments or advances, charge-offs and capitalized escrow arrearages.
(b)	Represents the present value of interest rate concessions discounted at the effective rate of the original loan.
Summary of Lease Financing Receivables	'
	A summary of lease financing receivables follows:
			December 31
			2013			2012
			(In thousands)
	Commercial leases:
	Direct financings:
	Lease payments receivable		$	1,052,214		$	1,106,434
	Estimated residual value of leased assets			85,595			96,468
	Unearned income			(114,101	)		(134,428	)
	Investment in direct financings			1,023,708			1,068,474
	Leveraged leases:
	Lease payments receivable			127,821			132,466
	Estimated residual value of leased assets			133,298			137,570
	Unearned income			(47,188	)		(50,378	)
	Investment in leveraged leases			213,931			219,658
	Total investment in leases.		$	1,237,639		$	1,288,132
	Deferred taxes payable arising from leveraged leases		$	172,296		$	172,026
Minimum Future Lease Payments to be Received from Lease Financings	'
	At December 31, 2013, the minimum future lease payments to be received from lease financings were as follows:
			(In thousands)
	Year ending December 31:
	2014		$	268,434
	2015			247,620
	2016			193,920
	2017			122,781
	2018			85,341
	Later years			261,939
			$	1,180,035

Allowance_for_credit_losses_Ta

Allowance for credit losses (Tables)	12 Months Ended
	Dec. 31, 2013
Receivables [Abstract]	'
Changes in Allowance for Credit Losses	'
	Changes in the allowance for credit losses for the years ended December 31, 2013, 2012 and 2011 were as follows:
		Commercial,			Real Estate
		Financial,
	2013	Leasing, etc.			Commercial			Residential			Consumer			Unallocated		Total
		(In thousands)
	Beginning balance	$	246,759		$	337,101		$	88,807		$	179,418		$	73,775	$	925,860
	Provision for credit losses		124,180			275			3,149			56,156			1,240		185,000
	Allowance related to loans sold or securitized		—			—			—			(11,000	)		—		(11,000	)
	Net charge-offs
	Charge-offs		(109,329	)		(34,595	)		(23,621	)		(85,965	)		—		(253,510	)
	Recoveries		11,773			22,197			10,321			26,035			—		70,326
	Net charge-offs		(97,556	)		(12,398	)		(13,300	)		(59,930	)		—		(183,184	)
	Ending balance	$	273,383		$	324,978		$	78,656		$	164,644		$	75,015	$	916,676
	2012
	Beginning balance	$	234,022		$	367,637		$	91,915		$	143,121		$	71,595	$	908,290
	Provision for credit losses		42,510			5,211			34,864			119,235			2,180		204,000
	Net charge-offs
	Charge-offs		(41,148	)		(41,945	)		(44,314	)		(103,348	)		—		(230,755	)
	Recoveries		11,375			6,198			6,342			20,410			—		44,325
	Net charge-offs		(29,773	)		(35,747	)		(37,972	)		(82,938	)		—		(186,430	)
	Ending balance	$	246,759		$	337,101		$	88,807		$	179,418		$	73,775	$	925,860
	2011
	Beginning balance	$	212,579		$	400,562		$	86,351		$	133,067		$	70,382	$	902,941
	Provision for credit losses		66,240			44,404			57,081			101,062			1,213		270,000
	Net charge-offs
	Charge-offs		(55,021	)		(86,869	)		(58,351	)		(109,246	)		—		(309,487	)
	Recoveries		10,224			9,540			6,834			18,238			—		44,836
	Net charge-offs		(44,797	)		(77,329	)		(51,517	)		(91,008	)		—		(264,651	)
	Ending balance	$	234,022		$	367,637		$	91,915		$	143,121		$	71,595	$	908,290
Impaired Loans and Leases	'
	The following tables provide information with respect to loans and leases that were considered impaired as of December 31, 2013 and 2012 and for the years ended December 31, 2013, 2012 and 2011.
		December 31, 2013									December 31, 2012
		Recorded			Unpaid			Related			Recorded			Unpaid		Related
		Investment			Principal			Allowance			Investment			Principal		Allowance
					Balance									Balance
		(In thousands)
	With an allowance recorded:
	Commercial, financial, leasing, etc.	$	90,293		$	112,092		$	24,614		$	127,282		$	149,534	$	33,829
	Real estate:
	Commercial		113,570			132,325			19,520			121,542			143,846		23,641
	Residential builder and developer		33,311			55,122			4,379			115,306			216,218		25,661
	Other commercial construction		86,260			90,515			4,022			73,544			76,869		6,836
	Residential		96,508			114,521			7,146			103,451			121,819		3,521
	Residential Alt-A		111,911			124,528			14,000			128,891			141,940		17,000
	Consumer:
	Home equity lines and loans		13,672			14,796			3,312			12,360			13,567		2,254
	Automobile		40,441			40,441			11,074			49,210			49,210		14,273
	Other		17,660			17,660			4,541			14,408			14,408		5,667
			603,626			702,000			92,608			745,994			927,411		132,682
	With no related allowance recorded:
	Commercial, financial, leasing, etc.		28,093			33,095			—			32,631			42,199		—
	Real estate:
	Commercial		65,271			84,333			—			78,380			100,337		—
	Residential builder and developer		72,366			104,768			—			74,307			105,438		—
	Other commercial construction		7,369			11,493			—			23,018			23,532		—
	Residential		84,144			95,358			—			86,342			96,448		—
	Residential Alt-A		28,357			52,211			—			31,354			58,768		—
			285,600			381,258			—			326,032			426,722		—
	Total:
	Commercial, financial, leasing, etc.		118,386			145,187			24,614			159,913			191,733		33,829
	Real estate:
	Commercial		178,841			216,658			19,520			199,922			244,183		23,641
	Residential builder and developer		105,677			159,890			4,379			189,613			321,656		25,661
	Other commercial construction		93,629			102,008			4,022			96,562			100,401		6,836
	Residential		180,652			209,879			7,146			189,793			218,267		3,521
	Residential Alt-A		140,268			176,739			14,000			160,245			200,708		17,000
	Consumer:
	Home equity lines and loans		13,672			14,796			3,312			12,360			13,567		2,254
	Automobile		40,441			40,441			11,074			49,210			49,210		14,273
	Other		17,660			17,660			4,541			14,408			14,408		5,667
	Total	$	889,226		$	1,083,258		$	92,608		$	1,072,026		$	1,354,133	$	132,682
Interest Income Recognized on Loans	'
		Year Ended									Year Ended
		December 31, 2013									December 31, 2012
		Average			Interest Income						Average			Interest Income
		Recorded			Recognized						Recorded			Recognized
		Investment			Total			Cash			Investment			Total		Cash
								Basis								Basis
		(In thousands)
	Commercial, financial, leasing, etc.	$	155,188		$	7,197		$	7,197		$	151,314		$	2,938	$	2,938
	Real estate:
	Commercial		197,533			4,852			4,852			185,171			2,834		2,834
	Residential builder and developer		147,288			1,043			796			249,191			1,563		1,102
	Other commercial construction		96,475			5,248			5,248			99,672			5,020		5,020
	Residential		183,059			6,203			4,111			132,888			5,284		3,300
	Residential Alt-A		149,461			6,784			2,341			171,546			7,175		2,226
	Consumer:
	Home equity lines and loans		12,811			683			183			11,322			663		179
	Automobile		44,116			2,916			515			51,650			3,470		724
	Other		15,710			634			208			11,028			472		197
	Total	$	1,001,641		$	35,560		$	25,451		$	1,063,782		$	29,419	$	18,520
		Year Ended
		December 31, 2011
					Interest Income
					Recognized
		Average			Total			Cash
		Recorded						Basis
		Investment
		(In thousands)
	Commercial, financial, leasing, etc.	$	163,485		$	3,306		$	3,278
	Real estate:
	Commercial		189,837			2,060			1,985
	Residential builder and developer		317,296			1,948			860
	Other commercial construction		105,947			926			684
	Residential		99,107			4,271			2,286
	Residential Alt-A		196,161			7,713			1,965
	Consumer:
	Home equity lines and loans		11,428			681			106
	Automobile		56,862			3,850			1,060
	Other		5,006			273			89
	Total	$	1,145,129		$	25,028		$	12,313
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,			Commercial			Residential			Other
		Financial,						Builder and			Commercial
		Leasing, etc						Developer			Construction
		(In thousands)
	December 31, 2013
	Pass	$	17,894,592		$	20,972,257		$	1,107,144		$	3,040,106
	Criticized accrual		699,885			596,553			72,941			54,464
	Criticized nonaccrual		110,739			173,048			96,427			35,268
	Total	$	18,705,216		$	21,741,858		$	1,276,512		$	3,129,838
	December 31, 2012
	Pass	$	16,889,753		$	21,275,182		$	922,141		$	2,307,436
	Criticized accrual		735,292			804,132			85,520			186,843
	Criticized nonaccrual		151,908			193,859			181,865			36,812
	Total	$	17,776,953		$	22,273,173		$	1,189,526		$	2,531,091
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,			Real Estate
		Financial,
		Leasing, etc.			Commercial			Residential			Consumer			Total
		(In thousands)
	December 31, 2013
	Individually evaluated for impairment	$	24,614		$	27,563		$	21,127		$	18,927		$	92,231
	Collectively evaluated for impairment		246,096			296,781			55,864			144,210			742,951
	Purchased impaired		2,673			634			1,665			1,507			6,479
	Allocated	$	273,383		$	324,978		$	78,656		$	164,644			841,661
	Unallocated														75,015
	Total													$	916,676
	December 31, 2012
	Individually evaluated for impairment	$	33,669		$	55,291		$	20,502		$	22,194		$	131,656
	Collectively evaluated for impairment		212,930			280,789			66,684			156,661			717,064
	Purchased impaired		160			1,021			1,621			563			3,365
	Allocated	$	246,759		$	337,101		$	88,807		$	179,418			852,085
	Unallocated														73,775
	Total													$	925,860
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,			Real Estate
		Financial,
		Leasing, etc.			Commercial			Residential			Consumer			Total
		(In thousands)
	December 31, 2013
	Individually evaluated for impairment	$	118,386		$	376,339		$	320,360		$	71,773		$	886,858
	Collectively evaluated for impairment		18,571,124			25,488,584			8,578,677			10,217,124			62,855,509
	Purchased impaired		15,706			283,285			29,184			2,617			330,792
	Total	$	18,705,216		$	26,148,208		$	8,928,221		$	10,291,514		$	64,073,159
	December 31, 2012
	Individually evaluated for impairment	$	159,761		$	480,335		$	349,477		$	75,978		$	1,065,551
	Collectively evaluated for impairment		17,599,755			25,123,758			10,854,591			11,480,188			65,058,292
	Purchased impaired		17,437			389,697			36,769			3,211			447,114
	Total	$	17,776,953		$	25,993,790		$	11,240,837		$	11,559,377		$	66,570,957

Premises_and_equipment_Tables

Premises and equipment (Tables)	12 Months Ended
	Dec. 31, 2013
Property Plant And Equipment [Abstract]	'
Summary of Premises and Equipment	'
	The detail of premises and equipment was as follows:
		December 31
		2013		2012
		(In thousands)
	Land	$	84,220	$	84,545
	Buildings — owned		402,065		393,527
	Buildings — capital leases		1,131		1,131
	Leasehold improvements		208,947		198,498
	Furniture and equipment — owned		547,824		465,113
	Furniture and equipment — capital leases		17,703		17,915
			1,261,890		1,160,729
	Less: accumulated depreciation and amortization
	Owned assets		617,228		559,948
	Capital leases		11,142		6,129
			628,370		566,077
	Premises and equipment, net	$	633,520	$	594,652

Capitalized_servicing_assets_T

Capitalized servicing assets (Tables)	12 Months Ended
	Dec. 31, 2013
Transfers And Servicing [Abstract]	'
Servicing Asset at Amortized Cost	'
	Changes in capitalized servicing assets were as follows:
		Residential Mortgage Loans									Commercial Mortgage Loans
	For Year Ended December 31,	2013			2012			2011			2013			2012			2011
		(In thousands)
	Beginning balance	$	104,855		$	131,264		$	92,066		$	59,978		$	51,250		$	42,613
	Originations		52,375			14,577			13,920			26,754			19,653			17,613
	Purchases		272			109			61,642			—			—			—
	Recognized in loan securitization transactions		13,696			—			—			—			—			—
	Amortization		(44,821	)		(41,095	)		(36,364	)		(14,233	)		(10,925	)		(8,976	)
			126,377			104,855			131,264			72,499			59,978			51,250
	Valuation allowance		(300	)		(4,500	)		(1,800	)		—			—			—
	Ending balance, net	$	126,077		$	100,355		$	129,464		$	72,499		$	59,978		$	51,250
		Other									Total
	For Year Ended December 31,	2013			2012			2011			2013			2012			2011
		(In thousands)
	Beginning balance	$	8,143		$	15,678		$	26,197		$	172,976		$	198,192		$	160,876
	Originations		—			—			—			79,129			34,230			31,533
	Purchases		—			—			—			272			109			61,642
	Recognized in loan securitization transactions		9,382			—			—			23,078			—			—
	Amortization		(6,300	)		(7,535	)		(10,519	)		(65,354	)		(59,555	)		(55,859	)
			11,225			8,143			15,678			210,101			172,976			198,192
	Valuation allowance		—			—			—			(300	)		(4,500	)		(1,800	)
	Ending balance, net	$	11,225		$	8,143		$	15,678		$	209,801		$	168,476		$	196,392
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		11.39	%
	Impact on fair value of 10% adverse change	$	(11,283,000	)
	Impact on fair value of 20% adverse change		(21,664,000	)
	Weighted-average OAS		7.7	%
	Impact on fair value of 10% adverse change	$	(5,714,000	)
	Impact on fair value of 20% adverse change		(11,155,000	)
	Weighted-average discount rate					18	%
	Impact on fair value of 10% adverse change				$	(3,677,000	)
	Impact on fair value of 20% adverse change					(7,096,000	)

Goodwill_and_other_intangible_1

Goodwill and other intangible assets (Tables)	12 Months Ended
	Dec. 31, 2013
Goodwill And Intangible Assets Disclosure [Abstract]	'
Schedule of Finite-Lived Intangible Assets	'
	Total amortizing intangible assets were comprised of the following:
		Gross Carrying		Accumulated		Net Carrying
		Amount		Amortization		Amount
		(In thousands)
	December 31, 2013
	Core deposit	$	755,794	$	705,518	$	50,276
	Other		177,268		158,693		18,575
	Total	$	933,062	$	864,211	$	68,851
	December 31, 2012
	Core deposit	$	755,794	$	670,940	$	84,854
	Other		177,268		146,359		30,909
	Total	$	933,062	$	817,299	$	115,763
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:
	2014	$	33,825
	2015		20,938
	2016		10,052
	2017		3,303
	2018		733
		$	68,851
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, 2013 and 2012 for purposes of testing for impairment is as follows.
		(In thousands)
	Business Banking	$	748,907
	Commercial Banking		907,524
	Commercial Real Estate		349,197
	Discretionary Portfolio		—
	Residential Mortgage Banking		—
	Retail Banking		1,144,404
	All Other		374,593
	Total	$	3,524,625

Borrowings_Tables

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2013
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			Other			Total
		Purchased			Short-term
		and			Borrowings
		Repurchase
		Agreements
		(Dollars in thousands)
	At December 31, 2013
	Amount outstanding	$	260,455		$	—		$	260,455
	Weighted-average interest rate		0.04	%		—			0.04	%
	For the year ended December 31, 2013
	Highest amount at a month-end	$	563,879		$	—
	Daily-average amount outstanding		390,034			—		$	390,034
	Weighted-average interest rate		0.11	%		—			0.11	%
	At December 31, 2012
	Amount outstanding	$	1,074,482		$	—		$	1,074,482
	Weighted-average interest rate		0.11	%		—			0.11	%
	For the year ended December 31, 2012
	Highest amount at a month-end	$	1,224,194		$	50,016
	Daily-average amount outstanding		822,859			16,043		$	838,902
	Weighted-average interest rate		0.15	%		0.57	%		0.15	%
	At December 31, 2011
	Amount outstanding	$	732,059		$	50,023		$	782,082
	Weighted-average interest rate		0.04	%		0.7	%		0.09	%
	For the year ended December 31, 2011
	Highest amount at a month-end	$	1,389,237		$	142,927
	Daily-average amount outstanding		706,749			120,059		$	826,808
	Weighted-average interest rate		0.11	%		0.18	%		0.12	%
Lines of Credit Under Formal Agreements	'
	At December 31, 2013, the Company had lines of credit under formal agreements as follows:
		M&T			M&T Bank			Wilmington
								Trust, N.A.
		(In thousands)
	Outstanding borrowings	$	—		$	28,868		$	—
	Unused		30,000			19,838,117			300,710
Long-term Borrowings	'
	Long-term borrowings were as follows:
		December 31,
		2013			2012
		(In thousands)
	Senior notes of M&T Bank:
	Variable rate due 2016	$	300,000		$	—
	1.45% due 2018		502,479			—
	Advances from FHLB:
	Fixed rates		29,079			30,066
	Agreements to repurchase securities		1,400,000			1,400,000
	Subordinated notes of Wilmington Trust Corporation
	(a wholly owned subsidiary of M&T):
	4.875% due 2013		—			251,298
	8.50% due 2018		224,067			230,255
	Subordinated notes of M&T Bank:
	6.625% due 2017		437,582			455,439
	9.50% due 2018		50,000			50,000
	5.585% due 2020, variable rate commencing 2015		392,964			385,669
	5.629% due 2021, variable rate commencing 2016		559,378			583,097
	Junior subordinated debentures of M&T associated with preferred capital securities:
	Fixed rates:
	M&T Capital Trust I — 8.234%, due 2027		154,640			154,640
	M&T Capital Trust II — 8.277%, due 2027		103,093			103,093
	M&T Capital Trust III — 9.25%, due 2027		66,109			66,434
	BSB Capital Trust I — 8.125%, due 2028		15,589			15,566
	Provident Trust I — 8.29%, due 2028		25,051			24,746
	Southern Financial Statutory Trust I — 10.60%, due 2030		6,521			6,496
	M&T Capital Trust IV — 8.50%, due 2068		350,010			350,010
	Variable rates:
	First Maryland Capital I — due 2027		144,641			144,102
	First Maryland Capital II — due 2027		145,964			145,301
	Allfirst Asset Trust — due 2029		96,059			95,913
	BSB Capital Trust III — due 2033		15,464			15,464
	Provident Trust III — due 2033		52,176			51,694
	Southern Financial Capital Trust III — due 2033		7,747			7,683
	Other		30,257			40,792
		$	5,108,870		$	4,607,758
Maturity of Long-term Borrowings	'
	Long-term borrowings at December 31, 2013 mature as follows:
		(In thousands)
	Year ending December 31:
	2014	$	22,021
	2015		5,756
	2016		1,105,075
	2017		1,041,871
	2018		777,991
	Later years		2,156,156
		$	5,108,870

Shareholders_equity_Tables

Shareholders' equity (Tables)	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
Issued and Outstanding Preferred Stock	'
	Issued and outstanding preferred stock of M&T is presented below:
			December 31, 2013				December 31, 2012
			Shares		Carrying		Shares		Carrying
			Issued and		Value		Issued and		Value
			Outstanding				Outstanding
			(Dollars in thousands)
	Series A(a)
	Fixed Rate Cumulative Perpetual Preferred Stock, Series A, $1,000 liquidation preference per share			230,000	$	230,000		230,000	$	226,965
	Series C(a)
	Fixed Rate Cumulative Perpetual Preferred Stock, Series C, $1,000 liquidation preference per share			151,500		151,500		151,500		145,535
	Series D(b)
	Fixed Rate Non-cumulative Perpetual Preferred Stock, Series D, $10,000 liquidation preference per share			50,000		500,000		50,000		500,000
	(a)	Shares were originally issued as part of the TARP of the U.S Treasury. Cash proceeds were allocated between the preferred stock and a ten-year warrant to purchase M&T common stock (Series A — 1,218,522 common shares at $73.86 per share, Series C — 407,542 common shares at $55.76 per share). The U.S. Treasury sold all of the shares of M&T preferred stock that it held in August 2012. In connection with that sale, the terms of the preferred stock were modified such that dividends, if declared, were paid quarterly at a rate of 5% per year through November 14, 2013 and at 6.375% thereafter, and M&T agreed to not redeem the preferred shares until on or after November 15, 2018. In December 2012, the U.S. Treasury sold to other investors the Series A warrants for $26.50 per warrant. In March 2013, the U.S. Treasury exercised the Series C warrants in a “cashless” exercise, resulting in the issuance of 186,589 common shares. During 2013, 69,127 of the Series A warrants were exercised in “cashless” exercises, resulting in the issuance of 25,427 common shares. Remaining outstanding Series A warrants were 1,149,395 at December 31, 2013.
	(b)	Dividends, if declared, will be paid semi-annually at a rate of 6.875% per year. The shares are redeemable in whole or in part on or after June 15, 2016. 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.

Stockbased_compensation_plans_

Stock-based compensation plans (Tables)	12 Months Ended
	Dec. 31, 2013
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			Weighted-		Restricted			Weighted-
		Stock Units			Average		Stock			Average
		Outstanding			Grant Price		Outstanding			Grant Price
	Unvested at January 1, 2013		799,495		$	70.28		1,095,631		$	71.01
	Granted		315,316			102.69		269,755			102.75
	Vested		(341,348	)		56.43		(446,882	)		56.74
	Cancelled		(2,633	)		96.9		(55,809	)		87.05
	Unvested at December 31, 2013		770,830		$	89.58		862,695		$	87.29
Summary of Stock Option Activity	'
	A summary of stock option activity follows:
		Stock			Weighted-Average					Aggregate
		Options								Intrinsic Value
		Outstanding			Exercise		Life			(In thousands)
					Price		(In Years)
	Outstanding at January 1, 2013		7,033,359		$	103.3
	Granted		100			102.69
	Exercised		(1,998,841	)		95.27
	Expired		(153,857	)		138.46
	Outstanding at December 31, 2013		4,880,761		$	105.48		2.8		$	66,464
	Exercisable at December 31, 2013		4,879,148		$	105.49		2.8		$	66,400

Pension_plans_and_other_postre1

Pension plans and other postretirement benefits (Tables)	12 Months Ended
	Dec. 31, 2013
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
			2013			2012			2011
			(In thousands)
	Service cost		$	24,360		$	29,549		$	28,828
	Interest cost on benefit obligation			60,130			62,037			58,545
	Expected return on plan assets			(87,353	)		(70,511	)		(60,700	)
	Amortization of prior service credit			(6,556	)		(6,559	)		(6,559	)
	Recognized net actuarial loss			41,076			37,386			20,530
	Net periodic pension expense		$	31,657		$	51,902		$	40,644
	Net other postretirement benefits expense for defined benefit plans consisted of the following:
			Year Ended December 31
			2013			2012			2011
			(In thousands)
	Service cost		$	742		$	668		$	535
	Interest cost on benefit obligation			2,691			3,737			3,761
	Amortization of prior service cost (credit)			(1,359	)		21			107
	Recognized net actuarial loss			360			530			36
	Net other postretirement benefits expense		$	2,434		$	4,956		$	4,439
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
			2013			2012			2013			2012
			(In thousands)
	Change in benefit obligation:
	Benefit obligation at beginning of year		$	1,644,567		$	1,496,490		$	74,966		$	90,104
	Service cost			24,360			29,549			742			668
	Interest cost			60,130			62,037			2,691			3,737
	Plan participants’ contributions			—			—			3,069			3,765
	Amendments			—			—			—			(13,313	)
	Actuarial (gain) loss			(184,181	)		116,237			(12,830	)		(182	)
	Settlements/curtailments			—			(320	)		—			—
	Medicare Part D reimbursement			—			—			509			918
	Benefits paid			(60,683	)		(59,426	)		(8,555	)		(10,731	)
	Benefit obligation at end of year			1,484,193			1,644,567			60,592			74,966
	Change in plan assets:
	Fair value of plan assets at beginning of year			1,408,771			1,117,972			—			—
	Actual return on plan assets			150,795			143,430			—			—
	Employer contributions			7,801			207,115			4,977			6,048
	Plan participants’ contributions			—			—			3,069			3,765
	Medicare Part D reimbursement			—			—			509			918
	Settlements			—			(320	)		—			—
	Benefits and other payments			(60,683	)		(59,426	)		(8,555	)		(10,731	)
	Fair value of plan assets at end of year			1,506,684			1,408,771			—			—
	Funded status		$	22,491		$	(235,796	)	$	(60,592	)	$	(74,966	)
	Assets and liabilities recognized in the consolidated balance sheet were:
	Net prepaid asset		$	139,576		$	—		$	—		$	—
	Accrued liabilities			(117,085	)		(235,796	)		(60,592	)		(74,966	)
	Amounts recognized in accumulated other comprehensive income (“AOCI”) were:
	Net loss (gain)		$	191,386		$	480,084		$	(1,056	)	$	12,134
	Net prior service cost			(16,899	)		(23,455	)		(11,814	)		(13,173	)
	Pre-tax adjustment to AOCI			174,487			456,629			(12,870	)		(1,039	)
	Taxes.			(68,486	)		(179,227	)		5,051			408
	Net adjustment to AOCI.		$	106,001		$	277,402		$	(7,819	)	$	(631	)
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			Total
						Postretirement
						Benefit Plans
			(In thousands)
	2013
	Net gain		$	(247,622	)	$	(12,830	)	$	(260,452	)
	Amortization of prior service credit			6,556			1,359			7,915
	Amortization of loss			(41,076	)		(360	)		(41,436	)
	Total recognized in other comprehensive income, pre-tax		$	(282,142	)	$	(11,831	)	$	(293,973	)
	2012
	Net loss (gain)		$	43,318		$	(182	)	$	43,136
	Prior service credit			—			(13,313	)		(13,313	)
	Amortization of prior service (cost) credit			6,559			(21	)		6,538
	Amortization of loss			(37,386	)		(530	)		(37,916	)
	Total recognized in other comprehensive income, pre-tax		$	12,491		$	(14,046	)	$	(1,555	)
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 2014:
			Pension Plans			Other
						Postretirement
						Benefit Plans
			(In thousands)
	Amortization of net prior service credit		$	(6,552	)	$	(1,359	)
	Amortization of net loss			13,460			—
Assumed Weighted-Average Rates Used to Determine Benefit Obligations	'
	The assumed weighted-average rates used to determine benefit obligations at December 31 were:
			Pension						Other
			Benefits						Postretirement
									Benefits
			2013			2012			2013			2012
	Discount rate			4.75	%		3.75	%		4.75	%		3.75	%
	Rate of increase in future compensation levels			4.42	%		4.5	%		—			—
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
			2013			2012			2011			2013			2012			2011
	Discount rate			3.75	%		4.25	%		5.25	%		3.75	%		4.25	%		5.25	%
	Long-term rate of return on plan assets			6.5	%		6.5	%		6.5	%		—			—			—
	Rate of increase in future compensation levels			4.5	%		4.5	%		4.5	%		—			—			—
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		$	100		$	(91	)
	Accumulated postretirement benefit obligation			2,147			(1,947	)
Fair Values of Company's Pension Plan Assets by Asset Category	'
	The fair values of the Company’s pension plan assets at December 31, 2013, by asset category, were as follows:
			Fair Value Measurement of Plan Assets At December 31, 2013
			Total			Quoted Prices			Significant			Significant
						in Active			Observable			Unobservable
						Markets			Inputs			Inputs
						for Identical Assets			(Level 2)			(Level 3)
						(Level 1)
			(In thousands)
	Asset category:
	Money-market funds		$	37,952		$	37,952		$	—		$	—
	Equity securities:
	M&T			142,955			142,955			—			—
	Domestic(a)			271,203			271,203			—			—
	International			24,053			24,053			—			—
	Mutual funds:
	Domestic			194,099			194,099			—			—
	International			413,685			413,685			—			—
				1,045,995			1,045,995			—			—
	Debt securities:
	Corporate(b)			63,196			—			63,196			—
	Government			75,043			—			75,043			—
	International			2,443			—			2,443			—
	Mutual funds:
	Domestic(c)			68,280			68,280			—			—
	International			43,742			43,742			—			—
				252,704			112,022			140,682			—
	Other:
	Diversified mutual fund			93,055			93,055			—			—
	Private real estate			3,123			—			—			3,123
	Private equity			6,199			—			—			6,199
	Hedge funds			65,663			41,489			—			24,174
				168,040			134,544			—			33,496
	Total(d)		$	1,504,691		$	1,330,513		$	140,682		$	33,496
	The fair values of the Company’s pension plan assets at December 31, 2012, by asset category, were as follows:
			Fair Value Measurement of Plan Assets At December 31, 2012
			Total			Quoted Prices			Significant			Significant
						in Active			Observable			Unobservable
						Markets			Inputs			Inputs
						for Identical Assets			(Level 2)			(Level 3)
						(Level 1)
			(In thousands)
	Asset category:
	Money-market funds		$	46,657		$	46,657		$	—		$	—
	Equity securities:
	M&T			120,914			120,914			—			—
	Domestic(a)			147,382			147,382			—			—
	International			8,561			8,561			—			—
	Mutual funds:
	Domestic			188,950			188,950			—			—
	International			208,696			208,696			—			—
				674,503			674,503			—			—
	Debt securities:
	Corporate(b)			307,712			—			307,712			—
	Government			141,224			—			141,224			—
	International			10,230			—			10,230			—
	Mutual funds:
	Domestic(c)			107,576			107,576			—			—
	International			54,362			54,362			—			—
				621,104			161,938			459,166			—
	Other:
	Diversified mutual fund			10,415			10,415			—			—
	Private real estate			4,603			—			—			4,603
	Private equity			5,347			—			—			5,347
Hedge funds			41,509			10,000			—			31,509
			61,874			20,415			—			41,459
Total(d)		$	1,404,138		$	903,513		$	459,166		$	41,459
(a)	This category is comprised of equities of companies primarily within the mid-cap and large-cap sector of the U.S. economy and range across diverse industries.
(b)	This category represents investment grade bonds of U.S. issuers from diverse industries.
(c)	Approximately 35% of the mutual funds were invested in investment grade bonds of U.S. issuers and 65% in high-yielding bonds at December 31, 2013. Approximately 40% of the mutual funds were invested in investment grade bonds of U.S. issuers and 60% in high-yielding bonds at December 31, 2012. The holdings within the funds are spread across diverse industries.
(d)	Excludes dividends and interest receivable totaling $1,993,000 and $4,633,000 at December 31, 2013 and 2012, 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, 2013 were as follows:
			Balance –			Sales/			Total			Balance –
			January 1,			Purchases			Realized/			December 31,
			2013						Unrealized			2013
									Gains (Losses)
			(In thousands)
	Other
	Private real estate		$	4,603		$	(308	)	$	(1,172	)	$	3,123
	Private equity			5,347			165			687			6,199
	Hedge funds			31,509			(9,873	)		2,538			24,174
	Total		$	41,459		$	(10,016	)	$	2,053		$	33,496
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			Other
			Benefits			Postretirement
						Benefits
			(In thousands)
	Year ending December 31:
	2014		$	65,970		$	6,780
	2015			67,993			6,503
	2016			73,628			6,283
	2017			77,180			5,995
	2018			80,380			5,741
	2019 through 2023			461,397			25,172

Income_taxes_Tables

Income taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Components of Income Tax Expense (Benefit)	'
	The components of income tax expense (benefit) were as follows:
		Year Ended December 31
		2013			2012			2011
		(In thousands)
	Current
	Federal	$	371,249		$	309,156		$	277,631
	State and city		68,035			82,014			53,566
	Total current		439,284			391,170			331,197
	Deferred
	Federal		106,537			117,229			34,325
	State and city		33,248			14,629			(401	)
	Total deferred		139,785			131,858			33,924
	Total income taxes applicable to pre-tax income	$	579,069		$	523,028		$	365,121
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
		2013			2012			2011
		(In thousands)
	Income taxes at statutory federal income tax rate	$	601,142		$	543,384		$	428,610
	Increase (decrease) in taxes:
	Tax-exempt income		(34,747	)		(33,890	)		(33,799	)
	State and city income taxes, net of federal income tax effect		65,834			62,818			34,557
	Low income housing and other credits		(49,206	)		(42,074	)		(40,763	)
	Non-taxable gain on acquisition		—			—			(22,725	)
	Other		(3,954	)		(7,210	)		(759	)
		$	579,069		$	523,028		$	365,121
Deferred Tax Assets (Liabilities)	'
	Deferred tax assets (liabilities) were comprised of the following at December 31:
		2013			2012			2011
		(In thousands)
	Losses on loans and other assets	$	645,713		$	809,033		$	896,219
	Postretirement and other employee benefits		30,023			34,517			39,992
	Incentive compensation plans		37,772			50,067			49,183
	Interest on loans		100,725			72,278			46,965
	Retirement benefits		—			91,980			147,997
	Stock-based compensation		63,101			69,874			78,014
	Unrealized investment losses		—			—			50,528
	Depreciation and amortization		1,404			12,130			9,563
	Other		121,561			103,027			99,012
	Gross deferred tax assets		1,000,299			1,242,906			1,417,473
	Leasing transactions		(284,370	)		(291,524	)		(294,150	)
	Unrealized investment gains		(21,779	)		(23,574	)		—
	Capitalized servicing rights		(46,041	)		(20,348	)		(17,603	)
	Interest on subordinated note exchange		(6,075	)		(8,794	)		(11,275	)
	Retirement benefits		(9,397	)		—			—
	Other		(49,450	)		(61,410	)		(48,803	)
	Gross deferred tax liabilities		(417,112	)		(405,650	)		(371,831	)
	Net deferred tax asset	$	583,187		$	837,256		$	1,045,642
Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits	'
	A reconciliation of the beginning and ending amount of unrecognized tax benefits follows:
		Federal,			Accrued			Unrecognized
		State and			Interest			Income Tax
		Local Tax						Benefits
		(In thousands)
	Gross unrecognized tax benefits at January 1, 2011	$	24,853		$	20,696		$	45,549
	Increases in unrecognized tax benefits as a result of tax positions taken during 2011		4,659			—			4,659
	Decreases in unrecognized tax benefits as a result of settlements with taxing authorities		(9,742	)		(5,497	)		(15,239	)
	Decreases in unrecognized tax benefits as a result of tax positions taken in prior years		—			(1,645	)		(1,645	)
	Decreases in unrecognized tax benefits because applicable returns are no longer subject to examination		(8,471	)		(8,201	)		(16,672	)
	Unrecognized tax benefits acquired in a business combination		7,034			3,924			10,958
	Gross unrecognized tax benefits at December 31, 2011		18,333			9,277			27,610
	Increases in unrecognized tax benefits as a result of tax positions taken during 2012		860			—			860
	Increases in unrecognized tax benefits as a result of tax positions taken in prior years		—			4,514			4,514
	Decreases in unrecognized tax benefits as a result of settlements with taxing authorities		(1,002	)		—			(1,002	)
	Decreases in unrecognized tax benefits because applicable returns are no longer subject to examination		(1,643	)		(1,412	)		(3,055	)
	Gross unrecognized tax benefits at December 31, 2012		16,548			12,379			28,927
	Increases in unrecognized tax benefits as a result of tax positions taken during 2013		2,267			—			2,267
	Increases in unrecognized tax benefits as a result of tax positions taken in prior years		—			4,429			4,429
	Decreases in unrecognized tax benefits as a result of settlements with taxing authorities		(1,854	)		(487	)		(2,341	)
	Decreases in unrecognized tax benefits because applicable returns are no longer subject to examination		(2,350	)		(1,625	)		(3,975	)
	Gross unrecognized tax benefits at December 31, 2013	$	14,611		$	14,696			29,307
	Less: Federal, state and local income tax benefits								(9,611	)
	Net unrecognized tax benefits at December 31, 2013 that, if recognized, would impact the effective income tax rate							$	19,696

Earnings_per_common_share_Tabl

Earnings per common share (Tables)	12 Months Ended
	Dec. 31, 2013
Earnings Per Share [Abstract]	'
Computations of Basic Earnings Per Common Share	'
	The computations of basic earnings per common share follow:
			Year Ended December 31
			2013			2012			2011
			(In thousands, except per share)
	Income available to common shareholders:
	Net income		$	1,138,480		$	1,029,498		$	859,479
	Less: Preferred stock dividends(a)			(54,120	)		(53,450	)		(45,839	)
	Amortization of preferred stock discount(a)			(7,942	)		(8,026	)		(20,018	)
	Net income available to common equity			1,076,418			968,022			793,622
	Less: Income attributable to unvested stock-based compensation awards			(13,989	)		(14,632	)		(11,879	)
	Net income available to common shareholders		$	1,062,429		$	953,390		$	781,743
	Weighted-average shares outstanding:
	Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards			130,354			127,793			124,524
	Less: Unvested stock-based compensation awards			(1,700	)		(1,929	)		(1,861	)
	Weighted-average shares outstanding			128,654			125,864			122,663
	Basic earnings per common share		$	8.26		$	7.57		$	6.37
	(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
			2013			2012			2011
			(In thousands, except per share)
	Net income available to common equity		$	1,076,418		$	968,022		$	793,622
	Less: Income attributable to unvested stock-based compensation awards			(13,922	)		(14,593	)		(11,857	)
	Net income available to common shareholders		$	1,062,496		$	953,429		$	781,765
	Adjusted weighted-average shares outstanding:
	Common and unvested stock-based compensation awards			130,354			127,793			124,524
	Less: Unvested stock-based compensation awards			(1,700	)		(1,929	)		(1,861	)
	Plus: Incremental shares from assumed conversion of stock-based compensation awards			949			541			416
	Adjusted weighted-average shares outstanding			129,603			126,405			123,079
	Diluted earnings per common share		$	8.2		$	7.54		$	6.35

Comprehensive_income_Tables

Comprehensive income (Tables)	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
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 comprehensive income (loss) to net income.
			Investment Securities						Defined			Other			Total			Income			Net
									Benefit						Amount			Tax
			With			All			Plans						Before Tax
			OTTI			Other
			(in thousands)
	Balance — January 1, 2013		$	(91,835	)		152,199			(455,590	)		(431	)	$	(395,657	)		155,393		$	(240,264	)
	Other comprehensive income before reclassifications:
	Unrealized holding gains (losses), net			77,794			(129,628	)		—			—			(51,834	)		20,311			(31,523	)
	Foreign currency translation adjustment			—			—			—			546			546			(165	)		381
	Current year pension gains (losses)			—			—			260,452			—			260,452			(102,227	)		158,225
	Total other comprehensive income before reclassifications			77,794			(129,628	)		260,452			546			209,164			(82,081	)		127,083
	Amounts reclassified from accumulated other
	comprehensive income that
	(increase) decrease net income:
	Accretion of unrealized holding losses on held-to-maturity (“HTM”) securities			279			4,008			—			—			4,287	(a)		(1,683	)		2,604
	OTTI charges recognized in net income			9,800			—			—			—			9,800	(b)		(3,847	)		5,953
	Losses (gains) realized in net income			41,217			(8,129	)		—			—			33,088	(c)		(12,987	)		20,101
	Amortization of prior service credit			—			—			(7,915	)		—			(7,915	)(e)		3,107			(4,808	)
	Amortization of actuarial losses			—			—			41,436			—			41,436	(e)		(16,264	)		25,172
	Total reclassifications			51,296			(4,121	)		33,521			—			80,696			(31,674	)		49,022
	Total gain (loss) during the			129,090			(133,749	)		293,973			546			289,860			(113,755	)		176,105
	period
	Balance — December 31, 2013		$	37,255			18,450			(161,617	)		115		$	(105,797	)		41,638		$	(64,159	)
			Investment Securities						Defined			Other			Total			Income			Net
									Benefit						Amount			Tax
			With			All			Plans						Before Tax
			OTTI			Other
			(in thousands)
	Balance — January 1, 2012		$	(138,319	)		9,757			(457,145	)		(1,062	)	$	(586,769	)		230,328		$	(356,441	)
	Other comprehensive income before reclassifications:
	Unrealized holding gains (losses), net			(2,998	)		137,921			—			—			134,923			(52,905	)		82,018
	Foreign currency translation adjustment			—			—			—			809			809			(290	)		519
	Current year pension			—			—			(29,823	)		—			(29,823	)		11,705			(18,118	)
	gains (losses)
	Total other comprehensive income before reclassifications			(2,998	)		137,921			(29,823	)		809			105,909			(41,490	)		64,419
	Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income:
	Accretion of unrealized holding losses on HTM securities			1,660			4,530			—			—			6,190	(a)		(2,430	)		3,760
	OTTI charges recognized in net income			47,822			—			—			—			47,822	(b)		(18,770	)		29,052
	Losses (gains) realized in net income			—			(9	)		—			—			(9	)(c)		4			(5	)
	Amortization of gains on terminated cash flow hedges			—			—			—			(178	)		(178	)		66			(112	)
	Amortization of prior service credit			—			—			(6,538	)		—			(6,538	)(e)		2,566			(3,972	)
	Amortization of actuarial losses			—			—			37,916			—			37,916	(e)		(14,881	)		23,035
	Total reclassifications			49,482			4,521			31,378			(178	)		85,203			(33,445	)		51,758
	Total gain (loss) during the period			46,484			142,442			1,555			631			191,112			(74,935	)		116,177
	Balance — December 31, 2012		$	(91,835	)		152,199			(455,590	)		(431	)	$	(395,657	)		155,393		$	(240,264	)
			Investment Securities						Defined			Other			Total			Income			Net
									Benefit						Amount			Tax
			With			All			Plans						Before Tax
			OTTI			Other
			(in thousands)
	Balance — January 1, 2011		$	(143,139	)		3,860			(198,999	)		626		$	(337,652	)		132,432		$	(205,220	)
	Other comprehensive income before reclassifications:
	Unrealized holding gains (losses), net			(68,946	)		145,522			—			—			76,576			(29,786	)		46,790
	Foreign currency translation adjustment			—			—			—			(1,240	)		(1,240	)		437			(803	)
	Current year pension			—			—			(272,260	)		—			(272,260	)		106,862			(165,398	)
	gains (losses)
	Total other comprehensive income before reclassifications			(68,946	)		145,522			(272,260	)		(1,240	)		(196,924	)		77,513			(119,411	)
	Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income:
	Accretion of unrealized holding losses on HTM securities			545			6,490			—			—			7,035	(a)		(2,762	)		4,273
	OTTI charges recognized in net income			77,035			—			—			—			77,035	(b)		(30,235	)		46,800
	Losses (gains) realized in net income			(3,814	)		(146,115	)		—			—			(149,929	)(c)		58,753			(91,176	)
	Amortization of gains on terminated cash flow hedges			—			—			—			(448	)		(448	)(d)		167			(281	)
Amortization of prior service credit			—			—			(6,452	)		—			(6,452	)(e)		2,532			(3,920	)
Amortization of actuarial losses			—			—			20,566			—			20,566	(e)		(8,072	)		12,494
Total reclassifications			73,766			(139,625	)		14,114			(448	)		(52,193	)		20,383			(31,810	)
Total gain (loss) during the period			4,820			5,897			(258,146	)		(1,688	)		(249,117	)		97,896			(151,221	)
Balance — December 31, 2011		$	(138,319	)		9,757			(457,145	)		(1,062	)	$	(586,769	)		230,328		$	(356,441	)
(a)	Included in interest income.
(b)	Included in OTTI losses recognized in earnings.
(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 unrealized gains (losses) as follows:
									Cash			Foreign			Defined			Total
									Flow			Currency			Benefit
			Investment Securities						Hedges			Translation			Plans
			With OTTI			All Other						Adjustment
			(In thousands)
	Balance at January 1, 2011		$	(87,053	)	$	2,332		$	393		$	—		$	(120,892	)	$	(205,220	)
	Net gain (loss) during 2011			3,024			3,663			(281	)		(803	)		(156,824	)		(151,221	)
	Balance at December 31, 2011			(84,029	)		5,995			112			(803	)		(277,716	)		(356,441	)
	Net gain (loss) during 2012			28,239			86,586			(112	)		519			945			116,177
	Balance at December 31, 2012			(55,790	)		92,581			—			(284	)		(276,771	)		(240,264	)
	Net gain (loss) during 2013			78,422			(81,287	)		—			381			178,589			176,105
	Balance at December 31, 2013		$	22,632		$	11,294		$	—		$	97		$	(98,182	)	$	(64,159	)

Other_income_and_other_expense1

Other income and other expense (Tables)	12 Months Ended
	Dec. 31, 2013
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
		2013		2012		2011
		(In thousands)
	Other income:
	Bank owned life insurance	$	56,120	$	51,199	$	50,776
	Credit-related fee income		72,271		68,596		73,886
	Letter of credit fees		59,889		58,496		56,247
	Non-taxable gain from business combination						64,930
	Gains from loan securitization transactions		63,066
	Other expense:
	Professional services		335,794		248,544		222,122
	Amortization of capitalized servicing rights		65,354		59,555		55,859
	Advertising and promotion		56,597		52,388		58,312
	Write-down of investment in Bayview Lending Group LLC (“BLG”)						79,012

Derivative_financial_instrumen1

Derivative financial instruments (Tables)	12 Months Ended
	Dec. 31, 2013
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:
			Notional			Average		Weighted-Average						Estimated Fair
			Amount			Maturity		Rate						Value Gain
								Fixed			Variable
			(In thousands)			(In years)								(In thousands)
	December 31, 2013
	Fair value hedges:
	Fixed rate long-term borrowings(a)		$	1,400,000			3.7		4.42	%		1.2	%	$	102,875
	December 31, 2012
	Fair value hedges:
	Fixed rate long-term borrowings(a)		$	900,000			4.4		6.07	%		1.85	%	$	143,179
	(a)	Under the terms of these agreements, the Company receives settlement amounts at a fixed rate and pays at a variable rate.
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, 2013 mature as follows:
			(In thousands)
	Year ending December 31:
	2016		$	500,000
	2017			400,000
	2018			500,000
			$	1,400,000
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
			2013			2012		2013			2012
			(In thousands)
	Derivatives designated and qualifying as hedging instruments
	Fair value hedges:
	Interest rate swap agreements(a)		$	102,875		$	143,179	$	—		$	—
	Commitments to sell real estate loans(a)			6,957			1,114		487			3,825
				109,832			144,293		487			3,825
	Derivatives not designated and qualifying as hedging instruments
	Mortgage-related commitments to originate real estate loans for sale(a)			7,616			48,056		3,675			197
	Commitments to sell real estate loans(a)			6,120			1,982		230			6,570
	Trading:
	Interest rate contracts(b)			274,864			399,963		234,455			365,616
	Foreign exchange and other option and futures contracts(b)			15,831			8,725		15,342			8,658
				304,431			458,726		253,702			381,041
	Total derivatives		$	414,263		$	603,019	$	254,189		$	384,866
	(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.
Information About Fair Values of Derivative Instruments in Consolidated Statement of Income	'
			Amount of Unrealized Gain (Loss) Recognized
			Year Ended					Year Ended						Year Ended
			December 31, 2013					December 31, 2012						December 31, 2011
			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)		$	(40,304	)	$	38,986	$	(4,123	)	$	3,724		$	50,665		$	(47,916	)
	Derivatives not designated as hedging instruments
	Trading:
	Interest rate contracts(b)		$	9,824				$	8,004					$	6,130
	Foreign exchange and other option and futures contracts(b)			(3,369	)				(3,970	)					(2,649	)
	Total		$	6,455				$	4,034					$	3,481
	(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
	Dec. 31, 2013
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, 2013 and 2012 measured at estimated fair value on a recurring basis:
			Fair Value			Level 1(a)			Level 2(a)			Level 3
			Measurements at
			December 31,
			2013
			(In thousands)
	Trading account assets		$	376,131			51,386			324,745			—
	Investment securities available for sale:
	U.S. Treasury and federal agencies			37,776			—			37,776			—
	Obligations of states and political subdivisions			10,811			—			10,811			—
	Mortgage-backed securities:
	Government issued or guaranteed			4,165,086			—			4,165,086			—
	Privately issued			1,850			—			—			1,850
	Collateralized debt obligations			63,083			—			—			63,083
	Other debt securities			120,085			—			120,085			—
	Equity securities			133,095			82,450			50,645			—
				4,531,786			82,450			4,384,403			64,933
	Real estate loans held for sale			468,650			—			468,650			—
	Other assets(b)			123,568			—			115,952			7,616
	Total assets		$	5,500,135			133,836			5,293,750			72,549
	Trading account liabilities		$	249,797			—			249,797			—
	Other liabilities(b)			4,392			—			717			3,675
	Total liabilities		$	254,189			—			250,514			3,675
			Fair Value			Level 1(a)			Level 2(a)			Level 3
			Measurements at
			December 31,
			2012
			(In thousands)
	Trading account assets		$	488,966			56,106			432,860			—
	Investment securities available for sale:
	U.S. Treasury and federal agencies			39,344			—			39,344			—
	Obligations of states and political subdivisions			20,901			—			20,901			—
	Mortgage-backed securities:
	Government issued or guaranteed			3,371,041			—			3,371,041			—
	Privately issued			1,023,886			—			—			1,023,886
	Collateralized debt obligations			61,869			—			—			61,869
	Other debt securities			111,950			—			111,950			—
	Equity securities			110,446			98,364			12,082			—
				4,739,437			98,364			3,555,318			1,085,755
	Real estate loans held for sale			1,387,491			—			1,387,491			—
	Other assets(b)			194,331			—			146,275			48,056
	Total assets		$	6,810,225			154,470			5,521,944			1,133,811
	Trading account liabilities		$	374,274			—			374,274			—
	Other liabilities(b)			10,592			—			10,395			197
	Total liabilities		$	384,866			—			384,669			197
	(a)	There were no significant transfers between Level 1 and Level 2 of the fair value hierarchy during the years ended December 31, 2013 and 2012.
	(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 year ended December 31, 2013 were as follows:
			Investment Securities Available for Sale
			Privately Issued			Collateralized			Other
			Mortgage-			Debt			Assets  and
			backed			Obligations			Other
			Securities						Liabilities
			(In thousands)
	Balance — January 1, 2013		$	1,023,886		$	61,869		$	47,859
	Total gains (losses) realized/unrealized:
	Included in earnings			(56,102	)(a)		—			97,845	(b)
	Included in other comprehensive income			116,359	(e)		4,508	(e)		—
	Sales			(978,608	)		—			—
	Settlements			(103,685	)		(3,294	)		—
	Transfers in and/or out of Level 3(c)			—			—			(141,763	)(d)
	Balance — December 31, 2013		$	1,850		$	63,083		$	3,941
	Changes in unrealized gains included in earnings related to assets still held at December 31, 2013		$	—		$	—		$	3,431	(b)
	The changes in Level 3 assets and liabilities measured at estimated fair value on a recurring basis during the year ended December 31, 2012 were as follows:
			Investment Securities Available for Sale
			Privately			Collateralized			Other Assets
			Issued			Debt			and Other
			Mortgage-			Obligations			Liabilities
			backed
			Securities
			(In thousands)
	Balance — January 1, 2012		$	1,151,285		$	52,500		$	6,923
	Total gains (losses) realized/unrealized:
	Included in earnings			(42,467	)(a)		—			212,281	(b)
	Included in other comprehensive income			114,592	(e)		12,214	(e)		—
	Settlements			(199,524	)		(2,845	)		—
	Transfers in and/or out of Level 3(c)			—			—			(171,345	)(d)
	Balance — December 31, 2012		$	1,023,886		$	61,869		$	47,859
	Changes in unrealized gains (losses) included in earnings related to assets still held at December 31, 2012		$	(42,467	)(a)	$	—		$	47,859	(b)
	The changes in Level 3 assets and liabilities measured at estimated fair value on a recurring basis during the year ended December 31, 2011 were as follows:
			Investment Securities Available for Sale
			Privately			Collateralized			Other
			Issued			Debt			Assets and
			Mortgage-			Obligations			Other
			backed						Liabilities
			Securities
			(In thousands)
	Balance — January 1, 2011		$	1,457,968		$	110,756		$	2,244
	Total gains (losses) realized/unrealized:
	Included in earnings			(64,919	)(a)		19,231	(a)		67,163	(b)
	Included in other comprehensive income			6,816	(e)		(272	)(e)		—
	Purchases			—			50,790			—
	Sales			—			(124,874	)		—
	Settlements			(248,580	)		(3,131	)		—
	Transfers in and/or out of Level 3(c)			—			—			(62,484	)(d)
	Balance — December 31, 2011		$	1,151,285		$	52,500		$	6,923
	Changes in unrealized gains (losses) included in earnings related to assets still held at December 31, 2011		$	(64,919	)(a)	$	—		$	6,902	(b)
	(a)	Reported as an other-than-temporary impairment loss or as gain (loss) on bank investment securities in the consolidated statement of income.
	(b)	Reported as mortgage banking revenues in the consolidated statement of income and includes the fair value of commitment issuances and expirations.
	(c)	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.
	(d)	Transfers out of Level 3 consist of interest rate locks transferred to closed loans.
	(e)	Reported as net unrealized gains on investment securities in the consolidated statement of comprehensive income
Quantitative Information Related to Significant Unobservable Inputs	'
	The following table present quantitative information about significant unobservable inputs used in the fair value measurements for Level 3 assets and liabilities at December 31, 2013 and 2012:
			Fair Value at			Valuation		Unobservable	Range
			December 31,			Technique		Input/Assumptions	(Weighted-
			2013						Average)
			(In thousands)
	Recurring fair value measurements
	Privately issued mortgage–backed securities		$	1,850		Two independent pricing quotes		—	—
	Collateralized debt obligations			63,083		Discounted cash flow		Probability of default	17%-55% (39%)
								Loss severity	100%
	Net other assets (liabilities)(a)			3,941		Discounted cash flow		Commitment expirations	0%-90% (20%)
	(a)	Other Level 3 assets (liabilities) consist of commitments to originate real estate loans.
			Fair Value at			Valuation		Unobservable	Range
			December 31,			Technique		Input/Assumptions	(Weighted-
			2012						Average)
			(In thousands)
	Recurring fair value measurements
	Privately issued mortgage–backed securities		$	1,023,886		Discounted cash flow		Probability of default	1%-40% (19%)
								Loss severity	32%-82% (51%)
	Collateralized debt obligations			61,869		Discounted cash flow		Probability of default	22%-69% (47%)
								Loss severity	100%
	Net other assets (liabilities)(a)			47,859		Discounted cash flow		Commitment expirations	0%-69% (20%)
	(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, 2013
			Carrying			Estimated			Level 1			Level 2			Level 3
			Amount			Fair Value
			(In thousands)
	Financial assets:
	Cash and cash equivalents		$	1,672,934		$	1,672,934		$	1,596,877		$	76,057		$	—
	Interest-bearing deposits at banks			1,651,138			1,651,138			—			1,651,138			—
	Trading account assets			376,131			376,131			51,386			324,745			—
	Investment securities			8,796,497			8,690,494			82,450			8,384,106			223,938
	Loans and leases:
	Commercial loans and leases			18,705,216			18,457,288			—			—			18,457,288
	Commercial real estate loans			26,148,208			26,018,195			—			67,505			25,950,690
	Residential real estate loans			8,928,221			8,867,872			—			5,432,207			3,435,665
	Consumer loans			10,291,514			10,201,087			—			—			10,201,087
	Allowance for credit losses			(916,676	)		—			—			—			—
	Loans and leases, net			63,156,483			63,544,442			—			5,499,712			58,044,730
	Accrued interest receivable			222,558			222,558			—			222,558			—
	Financial liabilities:
	Noninterest-bearing deposits		$	(24,661,007	)	$	(24,661,007	)		—		$	(24,661,007	)		—
	Savings deposits and NOW accounts			(38,611,021	)		(38,611,021	)		—			(38,611,021	)		—
	Time deposits			(3,523,838	)		(3,542,789	)		—			(3,542,789	)		—
	Deposits at Cayman Islands office			(322,746	)		(322,746	)		—			(322,746	)		—
	Short-term borrowings			(260,455	)		(260,455	)		—			(260,455	)		—
	Long-term borrowings			(5,108,870	)		(5,244,902	)		—			(5,244,902	)		—
	Accrued interest payable			(43,419	)		(43,419	)		—			(43,419	)		—
	Trading account liabilities			(249,797	)		(249,797	)		—			(249,797	)		—
	Other financial instruments:
	Commitments to originate real estate loans for sale		$	3,941		$	3,941			—		$	—		$	3,941
	Commitments to sell real estate loans			12,360			12,360			—			12,360			—
	Other credit-related commitments			(118,886	)		(118,886	)		—			—			(118,886	)
	Interest rate swap agreements used for interest rate risk management			102,875			102,875			—			102,875			—
			December 31, 2012
			Carrying			Estimated			Level 1			Level 2			Level 3
			Amount			Fair Value
			(In thousands)
	Financial assets:
	Cash and cash equivalents		$	1,986,615		$	1,986,615		$	1,895,423		$	91,192		$	—
	Interest-bearing deposits at banks			129,945			129,945			—			129,945			—
	Trading account assets			488,966			488,966			56,106			432,860			—
	Investment securities			6,074,361			6,018,968			98,364			4,687,211			1,233,393
	Loans and leases:
	Commercial loans and leases			17,776,953			17,554,562			—			—			17,554,562
	Commercial real estate loans			25,993,790			25,858,482			—			199,997			25,658,485
	Residential real estate loans			11,240,837			11,381,319			—			8,100,915			3,280,404
	Consumer loans			11,559,377			11,504,799			—			—			11,504,799
	Allowance for credit losses			(925,860	)		—			—			—			—
	Loans and leases, net			65,645,097			66,299,162			—			8,300,912			57,998,250
	Accrued interest receivable			222,897			222,897			—			222,897			—
	Financial liabilities:
	Noninterest-bearing deposits		$	(24,240,802	)	$	(24,240,802	)		—		$	(24,240,802	)		—
	Savings deposits and NOW accounts			(35,763,566	)		(35,763,566	)		—			(35,763,566	)		—
	Time deposits			(4,562,366	)		(4,584,384	)		—			(4,584,384	)		—
	Deposits at Cayman Islands office			(1,044,519	)		(1,044,519	)		—			(1,044,519	)		—
	Short-term borrowings			(1,074,482	)		(1,074,482	)		—			(1,074,482	)		—
	Long-term borrowings			(4,607,758	)		(4,768,408	)		—			(4,768,408	)		—
	Accrued interest payable			(54,281	)		(54,281	)		—			(54,281	)		—
	Trading account liabilities			(374,274	)		(374,274	)		—			(374,274	)		—
	Other financial instruments:
	Commitments to originate real estate loans for sale		$	47,859		$	47,859			—		$	—		$	47,859
	Commitments to sell real estate loans			(7,299	)		(7,299	)		—			(7,299	)		—
	Other credit-related commitments			(119,464	)		(119,464	)		—			—			(119,464	)
	Interest rate swap agreements used for interest rate risk management			143,179			143,179			—			143,179			—

Commitments_and_contingencies_

Commitments and contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
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
		2013		2012
		(In thousands)
	Commitments to extend credit
	Home equity lines of credit	$	6,218,823	$	6,282,615
	Commercial real estate loans to be sold		62,386		139,929
	Other commercial real estate and construction		3,919,545		3,819,342
	Residential real estate loans to be sold		469,869		1,550,441
	Other residential real estate		384,617		445,268
	Commercial and other		10,419,545		10,070,711
	Standby letters of credit		3,600,528		4,025,329
	Commercial letters of credit		53,284		53,201
	Financial guarantees and indemnification contracts		2,457,633		2,120,361
	Commitments to sell real estate loans		854,656		2,625,408
Minimum Lease Payments Under Noncancellable Operating Leases	'
	Minimum lease payments under noncancellable operating leases are summarized in the following table:
		(In thousands)
	Year ending December 31:
	2014	$	85,923
	2015		80,237
	2016		66,265
	2017		52,793
	2018		43,593
	Later years		135,156
		$	463,967

Segment_information_Tables

Segment information (Tables)	12 Months Ended
	Dec. 31, 2013
Segment Reporting [Abstract]	'
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, 2013, 2012 and 2011
			Business Banking									Commercial Banking						Commercial Real Estate									Discretionary Portfolio
			2013			2012			2011			2013		2012		2011		2013			2012			2011			2013			2012			2011
	Net interest income(a)		$	325,521		$	347,067		$	334,811		$	758,231	$	753,678	$	655,407	$	570,786		$	531,398		$	467,683		$	66,157		$	66,303		$	63,030
	Noninterest income			102,945			103,283			95,429			263,766		253,808		249,150		130,895			133,120			99,409			(2,126	)		(76,113	)		98,770
				428,466			450,350			430,240			1,021,997		1,007,486		904,557		701,681			664,518			567,092			64,031			(9,810	)		161,800
	Provision for credit losses			26,450			22,245			45,689			76,818		15,781		29,823		7,365			4,238			58,474			16,670			44,305			59,309
	Amortization of core deposit and other intangible assets			—			—			—			—		—		—		—			—			—			—			—			—
	Depreciation and other amortization			198			122			140			564		567		553		14,296			11,004			9,054			1,330			2,065			2,859
	Other noninterest expense			214,043			179,428			177,172			288,842		262,820		248,428		214,246			190,879			154,042			30,431			31,006			32,262
	Income (loss) before taxes			187,775			248,555			207,239			655,773		728,318		625,753		465,774			458,397			345,522			15,600			(87,186	)		67,370
	Income tax expense (benefit)			76,735			101,484			84,532			264,433		296,894		256,311		143,981			149,321			105,709			(14,368	)		(54,071	)		7,975
	Net income (loss)		$	111,040		$	147,071		$	122,707		$	391,340	$	431,424	$	369,442	$	321,793		$	309,076		$	239,813		$	29,968		$	(33,115	)	$	59,395
	Average total assets (in millions)		$	5,080		$	4,909		$	5,192		$	21,655	$	19,946	$	17,650	$	17,150		$	16,437		$	15,025		$	16,480		$	16,583		$	14,170
	Capital expenditures (in millions)		$	1		$	—		$	—		$	—	$	—	$	—	$	—		$	—		$	—		$	—		$	—		$	—
												For the Years Ended December 31, 2013, 2012 and 2011
			Residential Mortgage									Retail Banking						All Other									Total
			Banking
			2013			2012			2011			2013		2012		2011		2013			2012			2011			2013			2012			2011
	Net interest income(a)		$	98,496		$	78,058		$	63,951		$	810,134	$	902,906	$	851,332	$	43,904		$	(80,894	)	$	(46,458	)	$	2,673,229		$	2,598,516		$	2,389,756
	Noninterest income			325,474			402,211			184,249			373,362		349,571		366,042		670,889			501,390			489,863			1,865,205			1,667,270			1,582,912
				423,970			480,269			248,200			1,183,496		1,252,477		1,217,374		714,793			420,496			443,405			4,538,434			4,265,786			3,972,668
	Provision for credit losses			(11,711	)		17,169			36,375			72,502		95,345		101,679		(3,094	)		4,917			(61,349	)		185,000			204,000			270,000
	Amortization of core deposit and other intangible assets			—			—			—			—		—		—		46,912			60,631			61,617			46,912			60,631			61,617
	Depreciation and other amortization			48,716			46,902			44,349			34,599		32,734		33,713		57,120			50,536			45,495			156,823			143,930			136,163
	Other noninterest expense			225,794			195,604			151,945			768,644		751,916		744,905		690,150			693,046			771,534			2,432,150			2,304,699			2,280,288
	Income (loss) before taxes			161,171			220,594			15,531			307,751		372,482		337,077		(76,295	)		(388,634	)		(373,892	)		1,717,549			1,552,526			1,224,600
	Income tax expense (benefit)			61,779			85,671			2,403			125,350		151,616		137,161		(78,841	)		(207,887	)		(228,970	)		579,069			523,028			365,121
	Net income (loss)		$	99,392		$	134,923		$	13,128		$	182,401	$	220,866	$	199,916	$	2,546		$	(180,747	)	$	(144,922	)	$	1,138,480		$	1,029,498		$	859,479
	Average total assets (in millions)		$	2,858		$	2,451		$	1,958		$	10,997	$	11,705	$	11,940	$	9,442		$	7,952		$	8,042		$	83,662		$	79,983		$	73,977
	Capital expenditures (in millions)		$	—		$	1		$	—		$	40	$	15	$	25	$	89		$	76		$	45		$	130		$	92		$	70
	(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 $24,971,000 in 2013, $26,391,000 in 2012 and $25,876,000 in 2011 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
			2013			2012			2011
			(In thousands)
	Revenues		$	(50,128	)	$	(71,452	)	$	(64,239	)
	Expenses			(16,235	)		(17,313	)		(14,146	)
	Income taxes (benefit)			(13,791	)		(22,029	)		(20,383	)
	Net income (loss)			(20,102	)		(32,110	)		(29,710	)

Regulatory_matters_Tables

Regulatory matters (Tables)	12 Months Ended
	Dec. 31, 2013
Banking And Thrift [Abstract]	'
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, 2013 and 2012 are presented below:
			M&T			M&T Bank			Wilmington
			(Consolidated)						Trust, N.A.
			(Dollars in thousands)
	December 31, 2013:
	Tier 1 capital
	Amount		$	8,792,035		$	7,341,506		$	420,330
	Ratio(a)			12	%		10.08	%		73.79	%
	Minimum required amount(b)			2,930,925			2,914,246			22,786
	Total capital
	Amount			11,045,589			9,445,770			424,975
	Ratio(a)			15.07	%		12.96	%		74.6	%
	Minimum required amount(b)			5,861,849			5,828,491			45,573
	Leverage
	Amount			8,792,035			7,341,506			420,330
	Ratio(c)			10.78	%		9.09	%		19.8	%
	Minimum required amount(b)			2,446,476			2,422,096			63,678
	December 31, 2012:
	Tier 1 capital
	Amount		$	7,810,196		$	6,767,774		$	405,469
	Ratio(a)			10.22	%		8.92	%		61.02	%
	Minimum required amount(b)			3,057,093			3,034,184			26,580
	Total capital
	Amount			10,230,302			8,981,931			410,873
	Ratio(a)			13.39	%		11.84	%		61.83	%
	Minimum required amount(b)			6,114,186			6,068,367			53,160
	Leverage
	Amount			7,810,196			6,767,774			405,469
	Ratio(c)			10.07	%		8.84	%		21.62	%
	Minimum required amount(b)			2,327,122			2,297,902			56,275
	(a)	The ratio of capital to risk-weighted assets, as defined by regulation.
	(b)	Minimum amount of capital to be considered adequately capitalized, as defined by regulation.
	(c)	The ratio of capital to average assets, as defined by regulation.

Parent_company_financial_state1

Parent company financial statements (Tables)	12 Months Ended
	Dec. 31, 2013
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]	'
Condensed Balance Sheet	'
	Condensed Balance Sheet
			December 31
			2013			2012
			(In thousands)
	Assets
	Cash in subsidiary bank		$	10,729		$	4,774
	Due from consolidated bank subsidiaries
	Money-market savings			968,274			714,677
	Current income tax receivable			1,914			1,835
	Other			1,894			—
	Total due from consolidated bank subsidiaries			972,082			716,512
	Investments in consolidated subsidiaries
	Banks and bank holding company			11,364,657			10,495,557
	Other			16,212			16,344
	Investments in unconsolidated subsidiaries (note 19)			33,751			33,916
	Investment in Bayview Lending Group LLC			73,883			93,489
	Other assets			80,098			83,975
	Total assets		$	12,551,412		$	11,444,567
	Liabilities
	Due to consolidated bank subsidiaries		$	—		$	213
	Accrued expenses and other liabilities			62,817			60,619
	Long-term borrowings			1,183,063			1,181,142
	Total liabilities			1,245,880			1,241,974
	Shareholders’ equity			11,305,532			10,202,593
	Total liabilities and shareholders’ equity		$	12,551,412		$	11,444,567
Condensed Statement of Income	'
	Condensed Statement of Income
			Year Ended December 31
			2013			2012			2011
			(In thousands, except per share)
	Income
	Dividends from consolidated bank subsidiaries		$	700,000		$	700,000		$	715,000
	Equity in earnings of Bayview Lending Group LLC			(16,126	)		(21,511	)		(24,231	)
	Other income			9,992			8,755			67,829
	Total income			693,866			687,244			758,598
	Expense
	Interest on long-term borrowings			73,115			82,286			90,959
	Other expense (a)			15,994			19,226			87,368
	Total expense			89,109			101,512			178,327
	Income before income taxes and equity in undistributed income of subsidiaries			604,757			585,732			580,271
	Income tax credits			35,986			43,149			50,460
	Income before equity in undistributed income of subsidiaries			640,743			628,881			630,731
	Equity in undistributed income of subsidiaries
	Net income of subsidiaries			1,197,737			1,100,617			943,748
	Less: dividends received			(700,000	)		(700,000	)		(715,000	)
	Equity in undistributed income of subsidiaries			497,737			400,617			228,748
	Net income		$	1,138,480		$	1,029,498		$	859,479
	Net income per common share
	Basic		$	8.26		$	7.57		$	6.37
	Diluted			8.2			7.54			6.35
	(a)	In 2011 includes $79 million write-down of Investment in Bayview Lending Group LLC.
Condensed Statement of Cash Flow	'
	Condensed Statement of Cash Flows
			Year Ended December 31
			2013			2012			2011
			(In thousands)
	Cash flows from operating activities
	Net income		$	1,138,480		$	1,029,498		$	859,479
	Adjustments to reconcile net income to net cash provided by operating activities
	Equity in undistributed income of subsidiaries			(497,737	)		(400,617	)		(228,748	)
	Provision for deferred income taxes			1,535			1,724			(10,349	)
	Asset write-downs			—			—			79,012
	Net change in accrued income and expense			31,979			6,798			44,336
	Net cash provided by operating activities			674,257			637,403			743,730
	Cash flows from investing activities
	Proceeds from sales of investment securities			—			411			1,987
	Proceeds from maturities of investment securities			—			—			4,400
	Investment in subsidiary			(140,000	)		—			—
	Purchase of Wilmington Trust Corporation preferred stock			—			—			(330,000	)
	Other, net			3,295			324			2,833
	Net cash provided (used) by investing activities			(136,705	)		735			(320,780	)
	Cash flows from financing activities
	Payments on long-term borrowings			—			(300,000	)		—
	Dividends paid — common			(365,349	)		(357,717	)		(350,129	)
	Dividends paid — preferred			(53,450	)		(53,450	)		(48,203	)
	Proceeds from issuance of preferred stock			—			—			495,000
	Redemption of preferred stock			—			—			(370,000	)
	Other, net			140,799			143,352			16,386
	Net cash used by financing activities			(278,000	)		(567,815	)		(256,946	)
	Net increase in cash and cash equivalents			259,552			70,323			166,004
	Cash and cash equivalents at beginning of year			719,451			649,128			483,124
	Cash and cash equivalents at end of year		$	979,003		$	719,451		$	649,128
	Supplemental disclosure of cash flow information
	Interest received during the year		$	2,224		$	1,970		$	2,082
	Interest paid during the year			71,090			80,090			87,184
	Income taxes received during the year			45,237			21,878			57,964

Recovered_Sheet1

Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2013
Significant Accounting Policies [Line Items]	'
Delinquent period in which principal or interest is charged against income (in days)	'90 days
Delinquent period in which the net realizable value of the property collateralizing loan is charged-off	'150 days
Estimated useful lives of core deposit and other intangible assets	'8 years
Maximum [Member]	'
Significant Accounting Policies [Line Items]	'
Consumer loans delay in payments	'90 days
Consumer loans due in days	'180 days
Estimated useful lives of core deposit and other intangible assets	'10 years
Minimum [Member]	'
Significant Accounting Policies [Line Items]	'
Consumer loans due in days	'91 days
Estimated useful lives of core deposit and other intangible assets	'5 years
Income tax benefit recognition criteria percentage threshold	50.00%

Acquisitions_Additional_Inform

Acquisitions - Additional Information (Detail) (USD $)

12 Months Ended

1 Months Ended

1 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Aug. 27, 2012

31-May-11

Aug. 27, 2012

31-May-11

31-May-11

Aug. 27, 2012

16-May-13

31-May-11

Dec. 31, 2011

16-May-11

Dec. 31, 2013

Common stock [Member]

Minimum [Member]

Maximum [Member]

Cash [Member]

Wilmington Trust Corporation Acquisition [Member]

Wilmington Trust Corporation Acquisition [Member]

Wilmington Trust Corporation Acquisition [Member]

Wilmington Trust Corporation Acquisition [Member]

Hudson City [Member]

Office

Business Acquisition [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Purchase consideration per common share

'

'

'

0.08403

'

'

'

'

'

'

'

'

'

'

Percentage of total consideration

'

'

'

'

'

60.00%

'

'

40.00%

'

'

'

'

'

Total consideration to be paid

$5,000,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Assets

85,162,391,000

83,008,803,000

'

'

'

'

'

'

'

'

'

'

'

38,600,000,000

Loans

'

'

'

'

'

'

'

'

'

'

'

'

'

24,200,000,000

Investment securities

8,796,497,000

6,074,361,000

'

'

'

'

'

'

'

'

'

'

'

9,300,000,000

Liabilities

73,856,859,000

72,806,210,000

'

'

'

'

'

'

'

'

'

'

'

33,900,000,000

Deposits

67,118,612,000

65,611,253,000

'

'

'

'

'

'

'

'

'

'

'

21,500,000,000

Number of banking offices operated

'

'

'

'

'

'

'

'

'

'

'

'

55

'

Shares of M&T common stock exchanged for each share of Wilmington Trust common stock

'

'

'

'

'

'

'

'

'

'

'

'

0.051372

'

Common stock issued for acquisition

'

'

'

'

'

'

'

'

'

4,694,486

'

'

'

'

Common shares issued for acquisition fair value

'

'

'

'

'

'

'

'

'

'

'

'

405,557,000

'

Assets acquired total

'

'

'

'

'

'

'

'

'

10,800,000,000

'

'

'

'

Loans and leases

'

'

'

'

'

'

'

'

'

6,400,000,000

'

'

'

'

Commercial real estate loans

'

'

'

'

'

'

'

'

'

3,200,000,000

'

'

'

'

Commercial loans and leases

'

'

'

'

'

'

'

'

'

1,400,000,000

'

'

'

'

Consumer loans

'

'

'

'

'

'

'

'

'

1,100,000,000

'

'

'

'

Residential real estate loans

'

'

'

'

'

'

'

'

'

680,000,000

'

'

'

'

Liabilities

'

'

'

'

'

'

'

'

'

10,000,000,000

'

'

'

'

Deposits

'

'

'

'

'

'

'

'

'

8,900,000,000

'

'

'

'

Value added in shareholders equity due to acquisition

'

'

'

'

'

'

'

'

'

406,000,000

'

'

'

'

Preferred stock redeemed

'

'

'

'

'

'

'

'

'

330,000,000

'

'

'

'

Core deposit and other intangibles

'

'

'

'

'

'

'

'

'

112,000,000

'

'

'

'

Intangible Assets Amortization

'

'

'

'

'

'

'5 years

'7 years

'

'

'

'

'

'

Goodwill

3,524,625,000

3,524,625,000

'

'

0

'

'

'

'

'

'

'

'

'

Realized non-taxable gain

'

'

'

'

'

'

'

'

'

'

65,000,000

'

'

'

Provision for credit losses

185,000,000

204,000,000

270,000,000

'

'

'

'

'

'

'

'

42,000,000

'

'

Other- than-temporary impairment

'

'

'

'

'

'

'

'

'

'

'

5,000,000

'

'

Merger related expenses associated with acquisition of Wilmington Trust

'

'

$84,000,000

'

'

'

'

'

'

'

'

'

'

'

Acquisitions_Pro_Forma_Informa

Acquisitions - Pro Forma Information (Detail) (USD $)	7 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2011
Business Combinations [Abstract]	'	'
Total revenues actual since acquisition	$380,945	'
Total revenues pro forma	'	4,202,109
Net income actual since acquisition	18,586	'
Net income pro forma	'	$808,696

Acquisitions_Summary_of_Merger

Acquisitions - Summary of Merger-Related Expenses (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary of merger-related expenses	'	'	'
Salaries and employee benefits	$1,355,178	$1,314,540	$1,203,993
Equipment and net occupancy	264,327	257,551	249,514
Printing, postage and supplies	39,557	41,929	40,917
Other costs of operations	860,327	733,499	821,797
Total merger-related expenses	'	'	84,000
Bank Acquisition [Member]	'	'	'
Summary of merger-related expenses	'	'	'
Salaries and employee benefits	836	4,997	16,131
Equipment and net occupancy	690	15	412
Printing, postage and supplies	1,825	'	2,663
Other costs of operations	9,013	4,867	64,481
Total merger-related expenses	$12,364	$9,879	$83,687

Investment_Securities_Amortize

Investment Securities - Amortized Cost and Estimated Fair Value of Investment Securities (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Other securities, Amortized cost	$298,581	$302,648
Other securities, Gross unrealized gains	'	'
Other securities, Gross unrealized losses	'	'
Other securities, Estimated fair value	298,581	302,648
Investment securities, available for sale, amortized cost	4,444,365	4,643,070
Gross unrealized gains	127,333	253,619
Gross unrealized losses	39,912	157,252
Estimated fair value	4,531,786	4,739,437
Amortized cost for held to maturity	3,966,130	1,032,276
Gross unrealized gains for held to maturity	19,904	39,534
Gross unrealized losses for held to maturity	125,907	94,927
Estimated fair value for held to maturity	3,860,127	976,883
Total Amortized cost	8,709,076	5,977,994
Total for Gross unrealized gains	147,237	293,153
Total for Gross unrealized losses	165,819	252,179
Total for Estimated fair value	8,690,494	6,018,968
Government Issued or Guaranteed [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Investment securities, available for sale, amortized cost	4,123,435	3,163,210
Gross unrealized gains	61,001	208,060
Gross unrealized losses	19,350	229
Estimated fair value	4,165,086	3,371,041
Amortized cost for held to maturity	3,567,905	597,340
Gross unrealized gains for held to maturity	16,160	31,727
Gross unrealized losses for held to maturity	65,149	'
Estimated fair value for held to maturity	3,518,916	629,067
Privately issued [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Investment securities, available for sale, amortized cost	1,468	1,142,287
Gross unrealized gains	387	7,272
Gross unrealized losses	5	125,673
Estimated fair value	1,850	1,023,886
Amortized cost for held to maturity	219,628	242,378
Gross unrealized gains for held to maturity	'	160
Gross unrealized losses for held to maturity	60,623	94,900
Estimated fair value for held to maturity	159,005	147,638
Collateralized Debt Obligations [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Investment securities, available for sale, amortized cost	42,274	43,228
Gross unrealized gains	21,666	19,663
Gross unrealized losses	857	1,022
Estimated fair value	63,083	61,869
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	10,484	20,375
Gross unrealized gains	333	534
Gross unrealized losses	6	8
Estimated fair value	10,811	20,901
Amortized cost for held to maturity	169,684	182,103
Gross unrealized gains for held to maturity	3,744	7,647
Gross unrealized losses for held to maturity	135	27
Estimated fair value for held to maturity	173,293	189,723
Other Debt Securities [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Investment securities, available for sale, amortized cost	137,828	136,603
Gross unrealized gains	1,722	2,247
Gross unrealized losses	19,465	26,900
Estimated fair value	120,085	111,950
Amortized cost for held to maturity	8,913	10,455
Gross unrealized gains for held to maturity	'	'
Gross unrealized losses for held to maturity	'	'
Estimated fair value for held to maturity	8,913	10,455
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	37,396	38,422
Gross unrealized gains	382	922
Gross unrealized losses	2	'
Estimated fair value	37,776	39,344
Equity Securities [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Investment securities, available for sale, amortized cost	91,480	98,945
Gross unrealized gains	41,842	14,921
Gross unrealized losses	227	3,420
Estimated fair value	$133,095	$110,446

Investment_Securities_Addition

Investment Securities - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investment Holdings [Line Items]	'	'	'
Percentage of share holders equity that is not exceeded by investment in security of single non-us government or government agency	10.00%	'	'
Gross realized gains on investment securities	$116,490,000	'	$150,223,000
Gross realized losses on investment securities	60,033,000	'	36,000
Number of investment securities with aggregate gross unrealized losses	468	'	'
Unrealized losses on individual investment securities	-165,819,000	-252,179,000	'
Unrealized losses on privately issued residential mortgage-backed securities	61,000,000	'	'
Unrealized losses on trust preferred securities issued by financial institutions and securities backed by trust preferred securities	19,000,000	'	'
Cost method investment securities	299,000,000	'	'
Investment securities pledged to secure debt carrying value	3,902,317,000	'	'
Pledged securities that can be sold or repledged	1,696,438,000	1,801,842,000	'
Privately Issued Mortgage-Backed Securities [Member]	'	'	'
Investment Holdings [Line Items]	'	'	'
Privately issued mortgage backed securities sold	1,000,000,000	'	'
Net loss on securities sold	46,302,000	'	'
Aggregate amortized cost on mortgage-backed securities	220,000,000	'	'
Pre-tax other-than-temporary impairment losses	10,000,000	48,000,000	77,000,000
Securities Backed by Trust Preferred Securities [Member]	'	'	'
Investment Holdings [Line Items]	'	'	'
Aggregate amortized cost on mortgage-backed securities	123,000,000	'	'
Available-for-sale securities [Member]	'	'	'
Investment Holdings [Line Items]	'	'	'
Investment securities pledged to secure debt carrying value	2,459,296,000	'	'
Trust preferred securities [Member]	'	'	'
Investment Holdings [Line Items]	'	'	'
Aggregate amortized cost on mortgage-backed securities	'	'	136,000,000
Pre-tax gain on sale of mortgage-backed securities	'	'	25,000,000
Collateralized Debt Obligations [Member]	'	'	'
Investment Holdings [Line Items]	'	'	'
Aggregate amortized cost on mortgage-backed securities	'	'	100,000,000
Pre-tax gain on sale of mortgage-backed securities	'	'	20,000,000
Government Issued or Guaranteed [Member]	'	'	'
Investment Holdings [Line Items]	'	'	'
Aggregate amortized cost on mortgage-backed securities	'	'	1,500,000,000
Pre-tax gain on sale of mortgage-backed securities	'	'	104,000,000
Visa Class B [Member]	'	'	'
Investment Holdings [Line Items]	'	'	'
Gain on sale of holdings	89,545,000	'	'
MasterCard Class B [Member]	'	'	'
Investment Holdings [Line Items]	'	'	'
Gain on sale of holdings	$13,208,000	'	'

Investment_Securities_Investme

Investment Securities - Investment Ratings of All Privately Issued Mortgage-Backed Securities, Collateralized Debt Obligations and Other Debt Securities (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Amortized Cost	$590,279
Total securities with disclosed rating, Estimated Fair Value	537,040
Obligations of States and Political Subdivisions [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Amortized Cost	180,168
Total securities with disclosed rating, Estimated Fair Value	184,104
Mortgage-backed Securities, Privately issued [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Amortized Cost	221,096
Total securities with disclosed rating, Estimated Fair Value	160,855
Collateralized Debt Obligations [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Amortized Cost	42,274
Total securities with disclosed rating, Estimated Fair Value	63,083
Other Debt Securities [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Amortized Cost	146,741
Total securities with disclosed rating, Estimated Fair Value	128,998
A or Better [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	232,513
A or Better [Member] | Obligations of States and Political Subdivisions [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	152,704
A or Better [Member] | Mortgage-backed Securities, Privately issued [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	56,731
A or Better [Member] | Collateralized Debt Obligations [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	11,005
A or Better [Member] | Other Debt Securities [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	12,073
BBB [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	66,524
BBB [Member] | Obligations of States and Political Subdivisions [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	6,359
BBB [Member] | Mortgage-backed Securities, Privately issued [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	'
BBB [Member] | Collateralized Debt Obligations [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	3,684
BBB [Member] | Other Debt Securities [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	56,481
BB [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	38,070
BB [Member] | Obligations of States and Political Subdivisions [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	200
BB [Member] | Mortgage-backed Securities, Privately issued [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	'
BB [Member] | Collateralized Debt Obligations [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	8,904
BB [Member] | Other Debt Securities [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	28,966
B or Less [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	164,790
B or Less [Member] | Obligations of States and Political Subdivisions [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	'
B or Less [Member] | Mortgage-backed Securities, Privately issued [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	104,000
B or Less [Member] | Collateralized Debt Obligations [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	39,490
B or Less [Member] | Other Debt Securities [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	21,300
Not Rated [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	35,143
Not Rated [Member] | Obligations of States and Political Subdivisions [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	24,841
Not Rated [Member] | Mortgage-backed Securities, Privately issued [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	124
Not Rated [Member] | Collateralized Debt Obligations [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	'
Not Rated [Member] | Other Debt Securities [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total securities with disclosed rating, Estimated Fair Value	$10,178

Investment_Securities_Amortize1

Investment Securities - Amortized Cost and Estimated Fair Value of Collateralized Mortgage Obligations (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Amortized Cost And Fair Value Debt Securities [Abstract]	'	'
Collateralized mortgage obligations, Amortized cost	$231,040	$1,414,691
Estimated fair value	$171,100	$1,202,243

Investment_Securities_Changes_

Investment Securities - Changes in Credit Losses Associated with Debt Securities for Which OTTI Losses (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investments Debt And Equity Securities [Abstract]	'	'	'
Estimated credit losses - beginning balance	$197,809	$285,399	$327,912
Additions for credit losses not previously recognized	9,800	47,822	77,035
Reductions for increases in cash flows	'	'	-5,111
Reductions for realized losses	-207,441	-135,412	-114,437
Estimated credit losses - ending balance	$168	$197,809	$285,399

Investment_Securities_Amortize2

Investment Securities - Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Debt securities available for sale:	'	'
Due in one year or less	$29,839	'
Due after one year through five years	16,005	'
Due after five years through ten years	7,718	'
Due after ten years	174,420	'
Total available for sale (amortized cost)	227,982	'
Mortgage-backed securities available for sale	4,124,903	'
Total	4,352,885	'
Debt securities held to maturity:	'	'
Due in one year or less	19,485	'
Due after one year through five years	68,713	'
Due after five years through ten years	81,486	'
Due after ten years	8,913	'
Total available for held to maturity (amortized cost)	178,597	'
Mortgage-backed securities held to maturity	3,787,533	'
Total	3,966,130	1,032,276
Debt securities available for sale:	'	'
Due in one year or less	30,036	'
Due after one year through five years	16,617	'
Due after five years through ten years	8,015	'
Due after ten years	177,087	'
Total available for available for sale (fair value)	231,755	'
Mortgage-backed securities available for sale	4,166,936	'
Total	4,398,691	'
Debt securities held to maturity:	'	'
Due in one year or less	19,606	'
Due after one year through five years	70,618	'
Due after five years through ten years	83,069	'
Due after ten years	8,913	'
Total available for held to maturity (fair value)	182,206	'
Mortgage-backed securities held to maturity	3,677,921	'
Estimated fair value for held to maturity	$3,860,127	$976,883

Investment_Securities_Investme1

Investment Securities - Investment Securities in Continuous Unrealized Loss Position (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Estimated fair value, Less than 12 months	$1,699,426	$139,295
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	-19,458	-2,053
Estimated fair value, 12 months or more	116,330	888,499
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	-20,454	-155,199
Held to maturity, Estimated fair value, Less than 12 months	2,643,467	1,026
Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses	-65,269	-5
Held to maturity, Estimated fair value, 12 months or more	160,563	150,831
Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Aggregate Losses	-60,638	-94,922
Total investment securities, fair value less than 12 months	4,342,893	140,321
Investment Securities Continuous Unrealized Loss Position Less Than Twelve Months Aggregate Losses	-84,727	-2,058
Total of investment securities, fair value, 12 Months or More	276,893	1,039,330
Investment Securities Continuous Unrealized Loss Position Twelve Months or Longer Aggregate Losses	-81,092	-250,121
Government Issued or Guaranteed [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Estimated fair value, Less than 12 months	1,697,094	12,107
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	-19,225	-65
Estimated fair value, 12 months or more	5,815	8,804
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	-125	-164
Held to maturity, Estimated fair value, Less than 12 months	2,629,950	'
Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses	-65,149	'
Held to maturity, Estimated fair value, 12 months or more	'	'
Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Aggregate Losses	'	'
Privately Issued Mortgage-Backed Securities [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Held to maturity, Estimated fair value, Less than 12 months	'	'
Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses	'	'
Held to maturity, Estimated fair value, 12 months or more	159,005	147,273
Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Aggregate Losses	-60,623	-94,900
Privately Issued Mortgage-Backed Securities [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Estimated fair value, Less than 12 months	'	121,487
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	'	-692
Estimated fair value, 12 months or more	98	774,328
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	-5	-124,981
Obligations of States and Political Subdivisions [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Estimated fair value, Less than 12 months	'	166
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	'	-1
Estimated fair value, 12 months or more	558	683
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	-6	-7
Held to maturity, Estimated fair value, Less than 12 months	13,517	1,026
Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses	-120	-5
Held to maturity, Estimated fair value, 12 months or more	1,558	3,558
Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Aggregate Losses	-15	-22
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	745	'
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	-2	'
Estimated fair value, 12 months or more	'	'
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	'	'
Collateralized Debt Obligations [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Estimated fair value, Less than 12 months	'	'
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	'	'
Estimated fair value, 12 months or more	6,257	6,043
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	-857	-1,022
Other Debt Securities [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Estimated fair value, Less than 12 months	1,428	'
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	-4	'
Estimated fair value, 12 months or more	103,602	95,685
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	-19,461	-26,900
Equity Securities [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]	'	'
Estimated fair value, Less than 12 months	159	5,535
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	-227	-1,295
Estimated fair value, 12 months or more	'	2,956
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	'	($2,125)

Loans_and_Leases_Total_Gross_L

Loans and Leases - Total Gross Loans and Leases Outstanding (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Loans	'	'
Commercial, financial, etc.	$17,477,238	$16,500,202
Real estate:	'	'
Residential	8,911,554	11,161,323
Commercial	21,799,886	22,333,036
Construction	4,457,650	3,772,413
Consumer	10,280,527	11,550,274
Total loans	62,926,855	65,317,248
Leases	'	'
Commercial	1,398,928	1,472,938
Total loans and leases	64,325,783	66,790,186
Less: unearned discount	-252,624	-219,229
Total loans and leases, net of unearned discount	$64,073,159	$66,570,957

Loans_and_Leases_Additional_In

Loans and Leases - Additional Information (Detail) (USD $)	1 Months Ended	6 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Loans And Leases Receivable [Line Items]	'	'	'	'	'
Residential mortgage loans securitized with Ginnie Mae	'	$1,300,000,000	$3,000,000,000	'	'
Automobile loans securitized and sold	1,400,000,000	'	1,400,000,000	'	'
Recognized gain	'	42,382,000	42,382,000	'	'
Recognized gains sale of securities	20,683,000	'	20,683,000	'	'
Charges incurred for reimbursement of loan	'	'	17,000,000	28,000,000	23,000,000
Contractual principal and interest payments	'	'	331,000,000	447,000,000	'
Purchased impaired loans as a percentage of total assets	'	'	'Less than 1% of the Company's assets	'Less than 1% of the Company's assets	'
Interest income that would have been recognized on nonaccrual and renegotiated loans if those loans were accruing interest at their originally contracted terms	'	'	62,010,000	69,054,000	80,278,000
Interest on nonaccrual and renegotiated loans included in interest income	'	'	31,987,000	30,484,000	31,301,000
Exclusion limit of loans from related party disclosure	'	'	'Less than $120,000	'	'
Borrowing by directors and certain officers of M&T and its banking subsidiaries and their associates	'	'	135,512,000	99,532,000	'
New borrowings by directors, certain officers and their associates	'	'	44,799,000	'	'
Repayments and other reductions of borrowings by directors, certain officers and their associates	'	'	8,819,000	'	'
Guaranteed amount included in the estimated residual value of leased assets associated with direct financing leases	'	'	54,000,000	61,000,000	'
Residential mortgage loans [Member]	'	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'	'
Mortgage loans held for sale	'	'	401,000,000	1,200,000,000	'
Loans pledged to secure outstanding borrowings from the FHLB of New York	'	'	5,300,000,000	'	'
Commercial Real Estate [Member]	'	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'	'
Commercial real estate loans held for sale	'	'	68,000,000	200,000,000	'
Loans serviced for others sold with credit recourse	'	'	2,300,000,000	'	'
Loans pledged to secure outstanding borrowings from the FHLB of New York	'	'	9,600,000,000	'	'
Commercial loans and leases [Member]	'	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'	'
Loans pledged to secure outstanding borrowings from the FHLB of New York	'	'	8,900,000,000	'	'
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	'	'	4,100,000,000	'	'
Other consumer loans [Member]	'	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'	'
Loans pledged to secure outstanding borrowings from the FHLB of New York	'	'	$2,100,000,000	'	'

Loans_and_Leases_Outstanding_P

Loans and Leases - Outstanding Principal Balance and Carrying Amount of Loans that is Included in Consolidated Balance Sheet (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Outstanding principal and carrying value of acquired loans recorded at fair value	'	'
Outstanding principal balance	$4,656,811	$6,705,120
Carrying amount	4,007,452	5,840,353
Commercial, Financial, Leasing, etc. [Member]	'	'
Outstanding principal and carrying value of acquired loans recorded at fair value	'	'
Carrying amount	580,685	928,107
Real Estate Commercial [Member]	'	'
Outstanding principal and carrying value of acquired loans recorded at fair value	'	'
Carrying amount	1,541,368	2,567,050
Residential Real Estate [Member]	'	'
Outstanding principal and carrying value of acquired loans recorded at fair value	'	'
Carrying amount	576,473	707,309
Consumer [Member]	'	'
Outstanding principal and carrying value of acquired loans recorded at fair value	'	'
Carrying amount	$1,308,926	$1,637,887

Loans_and_Leases_Summary_of_Ch

Loans and Leases - Summary of Changes in Accretable Yield for Acquired Loans (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Purchased impaired [Member]	'	'	'
Summary of changes in Accretable Yield for acquired loans	'	'	'
Balance at beginning of period	$42,252	$30,805	$9,245
Additions	'	'	39,358
Interest income	-36,727	-40,551	-26,221
Reclassifications from nonaccretable balance, net	31,705	51,998	8,629
Other (a)	'	'	-206
Balance at end of period	37,230	42,252	30,805
Other [Member]	'	'	'
Summary of changes in Accretable Yield for acquired loans	'	'	'
Balance at beginning of period	638,272	807,960	447,505
Additions	'	'	648,631
Interest income	-247,295	-295,654	-268,315
Reclassifications from nonaccretable balance, net	149,595	148,490	1,800
Other (a)	-1,939	-22,524	-21,661
Balance at end of period	$538,633	$638,272	$807,960

Loans_and_Leases_Summary_of_Cu

Loans and Leases - Summary of Current, Past Due and Nonaccrual Loans (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Loans And Leases Receivable [Line Items]	'	'
Current	$61,664,881	$63,854,815
30-89 Days Past Due	704,658	730,901
Purchased Impaired (b)	330,792	447,114
Nonaccrual	874,156	1,013,176
Total	64,073,159	66,570,957
Commercial, Financial, Leasing, etc. [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	18,489,474	17,511,052
30-89 Days Past Due	77,538	62,479
Purchased Impaired (b)	15,706	17,437
Nonaccrual	110,739	151,908
Total	18,705,216	17,776,953
Commercial [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	21,236,071	21,759,997
30-89 Days Past Due	145,749	118,249
Purchased Impaired (b)	88,034	132,962
Nonaccrual	173,048	193,859
Total	21,741,858	22,273,173
Residential Builder and Developer [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	1,025,984	757,311
30-89 Days Past Due	8,486	35,419
Purchased Impaired (b)	137,544	187,764
Nonaccrual	96,427	181,865
Total	1,276,512	1,189,526
Other Commercial Construction [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	2,986,598	2,379,953
30-89 Days Past Due	42,234	35,274
Purchased Impaired (b)	57,707	68,971
Nonaccrual	35,268	36,812
Total	3,129,838	2,531,091
Residential [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	7,630,368	9,811,956
30-89 Days Past Due	295,131	337,969
Purchased Impaired (b)	29,184	36,769
Nonaccrual	252,805	249,314
Total	8,545,837	10,794,316
Residential Alt-A [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	283,253	331,021
30-89 Days Past Due	18,009	19,692
Purchased Impaired (b)	'	'
Nonaccrual	81,122	95,808
Total	382,384	446,521
Home equity lines and loans [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	5,972,365	6,199,591
30-89 Days Past Due	40,537	40,759
Purchased Impaired (b)	2,617	3,211
Nonaccrual	78,516	58,071
Total	6,121,789	6,321,950
Automobile [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	1,314,246	2,442,502
30-89 Days Past Due	29,144	40,461
Purchased Impaired (b)	'	'
Nonaccrual	21,144	25,107
Total	1,364,900	2,508,321
Other [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	2,726,522	2,661,432
30-89 Days Past Due	47,830	40,599
Purchased Impaired (b)	'	'
Nonaccrual	25,087	20,432
Total	2,804,825	2,729,106
Non-Acquired [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	368,510	358,397
Non-Acquired [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	4,981	23,490
Non-Acquired [Member] | Commercial [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	63,353	13,111
Non-Acquired [Member] | Residential Builder and Developer [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	141	3,258
Non-Acquired [Member] | Other Commercial Construction [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	'	509
Non-Acquired [Member] | Residential [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	294,649	313,184
Non-Acquired [Member] | Residential Alt-A [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	'	'
Non-Acquired [Member] | Home equity lines and loans [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	'	'
Non-Acquired [Member] | Automobile [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	'	'
Non-Acquired [Member] | Other [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	5,386	4,845
Acquired [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	130,162	166,554
Acquired [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	6,778	10,587
Acquired [Member] | Commercial [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	35,603	54,995
Acquired [Member] | Residential Builder and Developer [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	7,930	23,909
Acquired [Member] | Other Commercial Construction [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	8,031	9,572
Acquired [Member] | Residential [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	43,700	45,124
Acquired [Member] | Residential Alt-A [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	'	'
Acquired [Member] | Home equity lines and loans [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	27,754	20,318
Acquired [Member] | Automobile [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	366	251
Acquired [Member] | Other [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days Or More Past Due And Accruing - Non-Acquired	'	$1,798

Loans_and_Leases_Loan_Modifica

Loans and Leases - Loan Modification Activities that were Considered Troubled Debt Restructurings (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	Modification	Modification	Modification
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	1,258	1,608	1,780
Pre-modification Recorded Investment	$258,075	$256,681	$332,160
Post-modification, Recorded Investment	254,352	251,018	313,827
Financial Effects of Modification, Recorded Investment	-3,723	-5,663	-18,333
Financial Effects of Modification, Interest	-4,691	-2,853	-6,338
Principal deferral [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	79	61	53
Pre-modification Recorded Investment	16,389	23,888	10,703
Post-modification, Recorded Investment	16,002	22,456	10,778
Financial Effects of Modification, Recorded Investment	-387	-1,432	75
Financial Effects of Modification, Interest	'	'	'
Principal deferral [Member] | Commercial Real Estate [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	27	24	29
Pre-modification Recorded Investment	40,639	22,855	16,804
Post-modification, Recorded Investment	40,464	23,059	16,704
Financial Effects of Modification, Recorded Investment	-175	204	-100
Financial Effects of Modification, Interest	'	'	'
Principal deferral [Member] | Residential Builder and Developer [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	18	23	9
Pre-modification Recorded Investment	21,423	36,868	33,208
Post-modification, Recorded Investment	20,577	34,740	26,811
Financial Effects of Modification, Recorded Investment	-846	-2,128	-6,397
Financial Effects of Modification, Interest	'	'	'
Principal deferral [Member] | Other Commercial Construction [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	3	6	3
Pre-modification Recorded Investment	590	81,062	8,436
Post-modification, Recorded Investment	521	79,312	8,553
Financial Effects of Modification, Recorded Investment	-69	-1,750	117
Financial Effects of Modification, Interest	'	'	'
Principal deferral [Member] | Residential [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	32	36	37
Pre-modification Recorded Investment	3,556	4,643	8,175
Post-modification, Recorded Investment	3,821	4,808	8,235
Financial Effects of Modification, Recorded Investment	265	165	60
Financial Effects of Modification, Interest	'	'	'
Principal deferral [Member] | Residential Alt-A [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	10	7	3
Pre-modification Recorded Investment	1,900	968	800
Post-modification, Recorded Investment	1,880	989	835
Financial Effects of Modification, Recorded Investment	-20	21	35
Financial Effects of Modification, Interest	'	'	'
Principal deferral [Member] | Home equity lines and loans [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	10	15	3
Pre-modification Recorded Investment	859	1,285	259
Post-modification, Recorded Investment	861	1,285	259
Financial Effects of Modification, Recorded Investment	2	'	'
Financial Effects of Modification, Interest	'	'	'
Principal deferral [Member] | Automobile [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	460	618	746
Pre-modification Recorded Investment	6,148	8,347	10,053
Post-modification, Recorded Investment	6,148	8,347	10,053
Financial Effects of Modification, Recorded Investment	'	'	'
Financial Effects of Modification, Interest	'	'	'
Principal deferral [Member] | Other [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	36	80	23
Pre-modification Recorded Investment	332	1,201	400
Post-modification, Recorded Investment	332	1,201	400
Financial Effects of Modification, Recorded Investment	'	'	'
Financial Effects of Modification, Interest	'	'	'
Other [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	4	3	'
Pre-modification Recorded Investment	50,433	2,967	'
Post-modification, Recorded Investment	50,924	3,052	'
Financial Effects of Modification, Recorded Investment	491	85	'
Financial Effects of Modification, Interest	'	'	'
Other [Member] | Commercial Real Estate [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	2	'	'
Pre-modification Recorded Investment	449	'	'
Post-modification, Recorded Investment	475	'	'
Financial Effects of Modification, Recorded Investment	26	'	'
Financial Effects of Modification, Interest	'	'	'
Other [Member] | Residential Builder and Developer [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	1	'	6
Pre-modification Recorded Investment	4,039	'	118,114
Post-modification, Recorded Investment	3,888	'	110,156
Financial Effects of Modification, Recorded Investment	-151	'	-7,958
Financial Effects of Modification, Interest	'	'	'
Other [Member] | Residential [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	1	'	'
Pre-modification Recorded Investment	195	'	'
Post-modification, Recorded Investment	195	'	'
Financial Effects of Modification, Recorded Investment	'	'	'
Financial Effects of Modification, Interest	'	'	'
Other [Member] | Home equity lines and loans [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	1	'	3
Pre-modification Recorded Investment	106	'	86
Post-modification, Recorded Investment	106	'	86
Financial Effects of Modification, Recorded Investment	'	'	'
Financial Effects of Modification, Interest	'	'	'
Other [Member] | Automobile [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	78	67	111
Pre-modification Recorded Investment	339	300	739
Post-modification, Recorded Investment	339	300	739
Financial Effects of Modification, Recorded Investment	'	'	'
Financial Effects of Modification, Interest	'	'	'
Other [Member] | Other [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	2	13	4
Pre-modification Recorded Investment	14	54	103
Post-modification, Recorded Investment	14	54	103
Financial Effects of Modification, Recorded Investment	'	'	'
Financial Effects of Modification, Interest	'	'	'
Combination of concession types [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	11	5	3
Pre-modification Recorded Investment	6,229	628	2,049
Post-modification, Recorded Investment	5,578	740	2,046
Financial Effects of Modification, Recorded Investment	-651	112	-3
Financial Effects of Modification, Interest	-458	-102	-654
Combination of concession types [Member] | Commercial Real Estate [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	9	7	3
Pre-modification Recorded Investment	2,649	1,637	15,778
Post-modification, Recorded Investment	3,040	1,656	15,777
Financial Effects of Modification, Recorded Investment	391	19	-1
Financial Effects of Modification, Interest	-250	-351	-1,463
Combination of concession types [Member] | Residential Builder and Developer [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	3	7	5
Pre-modification Recorded Investment	15,580	37,602	2,540
Post-modification, Recorded Investment	15,514	36,148	2,561
Financial Effects of Modification, Recorded Investment	-66	-1,454	21
Financial Effects of Modification, Interest	-535	'	'
Combination of concession types [Member] | Other Commercial Construction [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	'	'	3
Pre-modification Recorded Investment	'	'	65,813
Post-modification, Recorded Investment	'	'	60,973
Financial Effects of Modification, Recorded Investment	'	'	-4,840
Combination of concession types [Member] | Residential [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	61	62	111
Pre-modification Recorded Investment	73,940	12,886	19,508
Post-modification, Recorded Investment	70,854	13,146	19,934
Financial Effects of Modification, Recorded Investment	-3,086	260	426
Financial Effects of Modification, Interest	-924	-657	-1,559
Combination of concession types [Member] | Residential Alt-A [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	19	38	34
Pre-modification Recorded Investment	2,826	8,525	6,813
Post-modification, Recorded Investment	3,148	8,717	6,978
Financial Effects of Modification, Recorded Investment	322	192	165
Financial Effects of Modification, Interest	-790	-159	-889
Combination of concession types [Member] | Home equity lines and loans [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	28	29	26
Pre-modification Recorded Investment	2,190	2,332	2,156
Post-modification, Recorded Investment	2,190	2,332	2,158
Financial Effects of Modification, Recorded Investment	'	'	2
Financial Effects of Modification, Interest	-270	-368	-444
Combination of concession types [Member] | Automobile [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	225	375	431
Pre-modification Recorded Investment	2,552	5,857	6,703
Post-modification, Recorded Investment	2,552	5,857	6,703
Financial Effects of Modification, Recorded Investment	'	'	'
Financial Effects of Modification, Interest	-191	-684	-808
Combination of concession types [Member] | Other [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	120	84	102
Pre-modification Recorded Investment	4,248	1,015	803
Post-modification, Recorded Investment	4,248	1,015	803
Financial Effects of Modification, Recorded Investment	'	'	'
Financial Effects of Modification, Interest	-1,187	-268	-189
Interest rate reduction [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	1	'	'
Pre-modification Recorded Investment	104	'	'
Post-modification, Recorded Investment	335	'	'
Financial Effects of Modification, Recorded Investment	231	'	'
Financial Effects of Modification, Interest	-54	'	'
Interest rate reduction [Member] | Commercial Real Estate [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	'	2	'
Pre-modification Recorded Investment	'	665	'
Post-modification, Recorded Investment	'	708	'
Financial Effects of Modification, Recorded Investment	'	43	'
Financial Effects of Modification, Interest	'	-129	'
Interest rate reduction [Member] | Residential [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	'	1	14
Pre-modification Recorded Investment	'	109	1,926
Post-modification, Recorded Investment	'	109	1,991
Financial Effects of Modification, Recorded Investment	'	'	65
Financial Effects of Modification, Interest	'	-20	-318
Interest rate reduction [Member] | Home equity lines and loans [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	1	1	'
Pre-modification Recorded Investment	99	144	'
Post-modification, Recorded Investment	99	144	'
Financial Effects of Modification, Recorded Investment	'	'	'
Financial Effects of Modification, Interest	-8	-6	'
Interest rate reduction [Member] | Automobile [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	15	22	17
Pre-modification Recorded Investment	235	328	183
Post-modification, Recorded Investment	235	328	183
Financial Effects of Modification, Recorded Investment	'	'	'
Financial Effects of Modification, Interest	-22	-24	-13
Interest rate reduction [Member] | Other [Member]	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'
Number of modifications	1	22	1
Pre-modification Recorded Investment	12	515	8
Post-modification, Recorded Investment	12	515	8
Financial Effects of Modification, Recorded Investment	'	'	'
Financial Effects of Modification, Interest	($2)	($85)	($1)

Loans_and_Leases_Summary_of_Le

Loans and Leases - Summary of Lease Financing Receivables (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Direct financings:	'	'
Lease payments receivable	$1,052,214	$1,106,434
Estimated residual value of leased assets	85,595	96,468
Unearned income	-114,101	-134,428
Investment in direct financings	1,023,708	1,068,474
Leveraged leases:	'	'
Lease payments receivable	127,821	132,466
Estimated residual value of leased assets	133,298	137,570
Unearned income	-47,188	-50,378
Investment in leveraged leases	213,931	219,658
Total investment in leases.	1,237,639	1,288,132
Deferred taxes payable arising from leveraged leases	$172,296	$172,026

Loans_and_Leases_Minimum_Futur

Loans and Leases - Minimum Future Lease Payments to be Received from Lease Financings (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Receivables [Abstract]	'
2014	$268,434
2015	247,620
2016	193,920
2017	122,781
2018	85,341
Later years	261,939
Total	$1,180,035

Allowance_for_Credit_Losses_Ch

Allowance for Credit Losses - Changes in Allowance for Credit Losses (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Beginning balance	$925,860	$908,290	$902,941
Provision for credit losses	185,000	204,000	270,000
Allowance related to loans sold or securitized	-11,000	'	'
Net charge-offs	'	'	'
Charge-offs	-253,510	-230,755	-309,487
Recoveries	70,326	44,325	44,836
Net charge-offs	-183,184	-186,430	-264,651
Ending balance	916,676	925,860	908,290
Commercial, Financial, Leasing, etc. [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Beginning balance	246,759	234,022	212,579
Provision for credit losses	124,180	42,510	66,240
Net charge-offs	'	'	'
Charge-offs	-109,329	-41,148	-55,021
Recoveries	11,773	11,375	10,224
Net charge-offs	-97,556	-29,773	-44,797
Ending balance	273,383	246,759	234,022
Real Estate Commercial [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Beginning balance	337,101	367,637	400,562
Provision for credit losses	275	5,211	44,404
Net charge-offs	'	'	'
Charge-offs	-34,595	-41,945	-86,869
Recoveries	22,197	6,198	9,540
Net charge-offs	-12,398	-35,747	-77,329
Ending balance	324,978	337,101	367,637
Residential Real Estate [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Beginning balance	88,807	91,915	86,351
Provision for credit losses	3,149	34,864	57,081
Net charge-offs	'	'	'
Charge-offs	-23,621	-44,314	-58,351
Recoveries	10,321	6,342	6,834
Net charge-offs	-13,300	-37,972	-51,517
Ending balance	78,656	88,807	91,915
Consumer [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Beginning balance	179,418	143,121	133,067
Provision for credit losses	56,156	119,235	101,062
Allowance related to loans sold or securitized	-11,000	'	'
Net charge-offs	'	'	'
Charge-offs	-85,965	-103,348	-109,246
Recoveries	26,035	20,410	18,238
Net charge-offs	-59,930	-82,938	-91,008
Ending balance	164,644	179,418	143,121
Unallocated [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'
Beginning balance	73,775	71,595	70,382
Provision for credit losses	1,240	2,180	1,213
Net charge-offs	'	'	'
Ending balance	$75,015	$73,775	$71,595

Allowance_for_Credit_Losses_Ad

Allowance for Credit Losses - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2013
Financing Receivable Allowance For Credit Loss Additional Information [Abstract]	'
Loan delinquent period	'90 days
Delinquency period for loan level collectability analysis consumer mortgage	'More than 150 days

Allowance_for_Credit_Losses_Im

Allowance for Credit Losses - Impaired Loans and Leases (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	$889,226	$1,072,026
Unpaid Principal Balance	1,083,258	1,354,133
Related Allowance	92,608	132,682
Commercial, Financial, Leasing, etc. [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	118,386	159,913
Unpaid Principal Balance	145,187	191,733
Related Allowance	24,614	33,829
Commercial Real Estate [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	178,841	199,922
Unpaid Principal Balance	216,658	244,183
Related Allowance	19,520	23,641
Residential Builder and Developer [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	105,677	189,613
Unpaid Principal Balance	159,890	321,656
Related Allowance	4,379	25,661
Other Commercial Construction [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	93,629	96,562
Unpaid Principal Balance	102,008	100,401
Related Allowance	4,022	6,836
Residential [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	180,652	189,793
Unpaid Principal Balance	209,879	218,267
Related Allowance	7,146	3,521
Residential Alt-A [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	140,268	160,245
Unpaid Principal Balance	176,739	200,708
Related Allowance	14,000	17,000
Home equity lines and loans [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	13,672	12,360
Unpaid Principal Balance	14,796	13,567
Related Allowance	3,312	2,254
Automobile [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	40,441	49,210
Unpaid Principal Balance	40,441	49,210
Related Allowance	11,074	14,273
Other [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	17,660	14,408
Unpaid Principal Balance	17,660	14,408
Related Allowance	4,541	5,667
Impaired Financing Receivable With Related Allowance [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	603,626	745,994
Unpaid Principal Balance	702,000	927,411
Related Allowance	92,608	132,682
Impaired Financing Receivable With Related Allowance [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	90,293	127,282
Unpaid Principal Balance	112,092	149,534
Related Allowance	24,614	33,829
Impaired Financing Receivable With Related Allowance [Member] | Commercial Real Estate [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	113,570	121,542
Unpaid Principal Balance	132,325	143,846
Related Allowance	19,520	23,641
Impaired Financing Receivable With Related Allowance [Member] | Residential Builder and Developer [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	33,311	115,306
Unpaid Principal Balance	55,122	216,218
Related Allowance	4,379	25,661
Impaired Financing Receivable With Related Allowance [Member] | Other Commercial Construction [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	86,260	73,544
Unpaid Principal Balance	90,515	76,869
Related Allowance	4,022	6,836
Impaired Financing Receivable With Related Allowance [Member] | Residential [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	96,508	103,451
Unpaid Principal Balance	114,521	121,819
Related Allowance	7,146	3,521
Impaired Financing Receivable With Related Allowance [Member] | Residential Alt-A [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	111,911	128,891
Unpaid Principal Balance	124,528	141,940
Related Allowance	14,000	17,000
Impaired Financing Receivable With Related Allowance [Member] | Home equity lines and loans [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	13,672	12,360
Unpaid Principal Balance	14,796	13,567
Related Allowance	3,312	2,254
Impaired Financing Receivable With Related Allowance [Member] | Automobile [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	40,441	49,210
Unpaid Principal Balance	40,441	49,210
Related Allowance	11,074	14,273
Impaired Financing Receivable With Related Allowance [Member] | Other [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	17,660	14,408
Unpaid Principal Balance	17,660	14,408
Related Allowance	4,541	5,667
Impaired Financing Receivable with No Related Allowance [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	285,600	326,032
Unpaid Principal Balance	381,258	426,722
Related Allowance	'	'
Impaired Financing Receivable with No Related Allowance [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	28,093	32,631
Unpaid Principal Balance	33,095	42,199
Related Allowance	'	'
Impaired Financing Receivable with No Related Allowance [Member] | Commercial Real Estate [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	65,271	78,380
Unpaid Principal Balance	84,333	100,337
Related Allowance	'	'
Impaired Financing Receivable with No Related Allowance [Member] | Residential Builder and Developer [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	72,366	74,307
Unpaid Principal Balance	104,768	105,438
Related Allowance	'	'
Impaired Financing Receivable with No Related Allowance [Member] | Other Commercial Construction [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	7,369	23,018
Unpaid Principal Balance	11,493	23,532
Related Allowance	'	'
Impaired Financing Receivable with No Related Allowance [Member] | Residential [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	84,144	86,342
Unpaid Principal Balance	95,358	96,448
Related Allowance	'	'
Impaired Financing Receivable with No Related Allowance [Member] | Residential Alt-A [Member]	'	'
Schedule Of Financial Receivables [Line Items]	'	'
Recorded Investment	28,357	31,354
Unpaid Principal Balance	52,211	58,768
Related Allowance	'	'

Allowance_for_Credit_Losses_In

Allowance for Credit Losses - Interest Income Recognized on Loans (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Loans And Leases Receivable [Line Items]	'	'	'
Average Recorded Investment	$1,001,641	$1,063,782	$1,145,129
Interest Income Recognized, Total	35,560	29,419	25,028
Interest Income Recognized, Cash Basis	25,451	18,520	12,313
Commercial, Financial, Leasing, etc. [Member]	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'
Average Recorded Investment	155,188	151,314	163,485
Interest Income Recognized, Total	7,197	2,938	3,306
Interest Income Recognized, Cash Basis	7,197	2,938	3,278
Commercial Real Estate [Member]	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'
Average Recorded Investment	197,533	185,171	189,837
Interest Income Recognized, Total	4,852	2,834	2,060
Interest Income Recognized, Cash Basis	4,852	2,834	1,985
Residential Builder and Developer [Member]	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'
Average Recorded Investment	147,288	249,191	317,296
Interest Income Recognized, Total	1,043	1,563	1,948
Interest Income Recognized, Cash Basis	796	1,102	860
Other Commercial Construction [Member]	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'
Average Recorded Investment	96,475	99,672	105,947
Interest Income Recognized, Total	5,248	5,020	926
Interest Income Recognized, Cash Basis	5,248	5,020	684
Residential [Member]	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'
Average Recorded Investment	183,059	132,888	99,107
Interest Income Recognized, Total	6,203	5,284	4,271
Interest Income Recognized, Cash Basis	4,111	3,300	2,286
Residential Alt-A [Member]	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'
Average Recorded Investment	149,461	171,546	196,161
Interest Income Recognized, Total	6,784	7,175	7,713
Interest Income Recognized, Cash Basis	2,341	2,226	1,965
Home equity lines and loans [Member]	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'
Average Recorded Investment	12,811	11,322	11,428
Interest Income Recognized, Total	683	663	681
Interest Income Recognized, Cash Basis	183	179	106
Automobile [Member]	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'
Average Recorded Investment	44,116	51,650	56,862
Interest Income Recognized, Total	2,916	3,470	3,850
Interest Income Recognized, Cash Basis	515	724	1,060
Other [Member]	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'
Average Recorded Investment	15,710	11,028	5,006
Interest Income Recognized, Total	634	472	273
Interest Income Recognized, Cash Basis	$208	$197	$89

Allowance_for_Credit_Losses_Su

Allowance for Credit Losses - Summary of Loan Grades (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	$64,073,159	$66,570,957
Commercial, Financial, Leasing, etc. [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	18,705,216	17,776,953
Commercial, Financial, Leasing, etc. [Member] | Pass [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	17,894,592	16,889,753
Commercial, Financial, Leasing, etc. [Member] | Criticized Accrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	699,885	735,292
Commercial, Financial, Leasing, etc. [Member] | Criticized Nonaccrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	110,739	151,908
Commercial [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	21,741,858	22,273,173
Commercial [Member] | Pass [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	20,972,257	21,275,182
Commercial [Member] | Criticized Accrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	596,553	804,132
Commercial [Member] | Criticized Nonaccrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	173,048	193,859
Residential Builder and Developer [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	1,276,512	1,189,526
Residential Builder and Developer [Member] | Pass [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	1,107,144	922,141
Residential Builder and Developer [Member] | Criticized Accrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	72,941	85,520
Residential Builder and Developer [Member] | Criticized Nonaccrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	96,427	181,865
Other Commercial Construction [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	3,129,838	2,531,091
Other Commercial Construction [Member] | Pass [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	3,040,106	2,307,436
Other Commercial Construction [Member] | Criticized Accrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	54,464	186,843
Other Commercial Construction [Member] | Criticized Nonaccrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	$35,268	$36,812

Allowance_for_Credit_Losses_Al

Allowance for Credit Losses - Allocation of Allowance for Credit Losses on Basis of Company's Impairment Methodology (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
In Thousands, unless otherwise specified
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	$916,676	$925,860	$908,290	$902,941
Allocated [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	841,661	852,085	'	'
Unallocated [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	75,015	73,775	'	'
Individually Evaluated for Impairment [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	92,231	131,656	'	'
Collectively Evaluated for Impairment [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	742,951	717,064	'	'
Purchased Impaired [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	6,479	3,365	'	'
Commercial, Financial, Leasing, etc. [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	273,383	246,759	234,022	212,579
Commercial, Financial, Leasing, etc. [Member] | Allocated [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	273,383	246,759	'	'
Commercial, Financial, Leasing, etc. [Member] | Individually Evaluated for Impairment [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	24,614	33,669	'	'
Commercial, Financial, Leasing, etc. [Member] | Collectively Evaluated for Impairment [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	246,096	212,930	'	'
Commercial, Financial, Leasing, etc. [Member] | Purchased Impaired [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	2,673	160	'	'
Commercial Real Estate [Member] | Allocated [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	324,978	337,101	'	'
Commercial Real Estate [Member] | Individually Evaluated for Impairment [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	27,563	55,291	'	'
Commercial Real Estate [Member] | Collectively Evaluated for Impairment [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	296,781	280,789	'	'
Commercial Real Estate [Member] | Purchased Impaired [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	634	1,021	'	'
Residential Real Estate [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	78,656	88,807	91,915	86,351
Residential Real Estate [Member] | Allocated [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	78,656	88,807	'	'
Residential Real Estate [Member] | Individually Evaluated for Impairment [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	21,127	20,502	'	'
Residential Real Estate [Member] | Collectively Evaluated for Impairment [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	55,864	66,684	'	'
Residential Real Estate [Member] | Purchased Impaired [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	1,665	1,621	'	'
Consumer loans [Member] | Allocated [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	164,644	179,418	'	'
Consumer loans [Member] | Individually Evaluated for Impairment [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	18,927	22,194	'	'
Consumer loans [Member] | Collectively Evaluated for Impairment [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	144,210	156,661	'	'
Consumer loans [Member] | Purchased Impaired [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Allowance for credit losses	$1,507	$563	'	'

Allowance_for_Credit_Losses_Re

Allowance for Credit Losses - Recorded Investment in Loans and Leases on Basis of Company's Impairment Methodology (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	$64,073,159	$66,570,957
Individually Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	886,858	1,065,551
Collectively Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	62,855,509	65,058,292
Purchased Impaired [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	330,792	447,114
Commercial, Financial, Leasing, etc. [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	18,705,216	17,776,953
Commercial, Financial, Leasing, etc. [Member] | Individually Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	118,386	159,761
Commercial, Financial, Leasing, etc. [Member] | Collectively Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	18,571,124	17,599,755
Commercial, Financial, Leasing, etc. [Member] | Purchased Impaired [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	15,706	17,437
Commercial Real Estate [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	26,148,208	25,993,790
Commercial Real Estate [Member] | Individually Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	376,339	480,335
Commercial Real Estate [Member] | Collectively Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	25,488,584	25,123,758
Commercial Real Estate [Member] | Purchased Impaired [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	283,285	389,697
Residential Real Estate [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	8,928,221	11,240,837
Residential Real Estate [Member] | Individually Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	320,360	349,477
Residential Real Estate [Member] | Collectively Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	8,578,677	10,854,591
Residential Real Estate [Member] | Purchased Impaired [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	29,184	36,769
Consumer loans [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	10,291,514	11,559,377
Consumer loans [Member] | Individually Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	71,773	75,978
Consumer loans [Member] | Collectively Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	10,217,124	11,480,188
Consumer loans [Member] | Purchased Impaired [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	$2,617	$3,211

Premises_and_equipment_Summary

Premises and equipment - Summary of Premises and Equipment (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Land	$84,220	$84,545
Leasehold improvements	208,947	198,498
Premises and equipment, Gross	1,261,890	1,160,729
Less: accumulated depreciation and amortization	628,370	566,077
Premises and equipment, net	633,520	594,652
Owned assets [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Buildings	402,065	393,527
Furniture and equipment	547,824	465,113
Less: accumulated depreciation and amortization	617,228	559,948
Capital leases [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Buildings	1,131	1,131
Furniture and equipment	17,703	17,915
Less: accumulated depreciation and amortization	$11,142	$6,129

Premises_and_equipment_Additio

Premises and equipment - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property Plant And Equipment [Abstract]	'	'	'
Net lease expense for all operating leases	$103,297,000	$102,924,000	$97,098,000

Capitalized_servicing_assets_C

Capitalized servicing assets - Changes in Capitalized Servicing Assets (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Servicing Asset at Amortized Cost [Line Items]	'	'	'
Amortized value, Beginning balance	$172,976	$198,192	$160,876
Originations	79,129	34,230	31,533
Purchases	272	109	61,642
Recognized in loan securitization transactions	23,078	'	'
Amortization	-65,354	-59,555	-55,859
Amortized value, ending balance	210,101	172,976	198,192
Valuation allowance	-300	-4,500	-1,800
Ending balance, net	209,801	168,476	196,392
Other [Member]	'	'	'
Servicing Asset at Amortized Cost [Line Items]	'	'	'
Amortized value, Beginning balance	8,143	15,678	26,197
Recognized in loan securitization transactions	9,382	'	'
Amortization	-6,300	-7,535	-10,519
Amortized value, ending balance	11,225	8,143	15,678
Ending balance, net	11,225	8,143	15,678
Residential Mortgage Loans [Member]	'	'	'
Servicing Asset at Amortized Cost [Line Items]	'	'	'
Amortized value, Beginning balance	104,855	131,264	92,066
Originations	52,375	14,577	13,920
Purchases	272	109	61,642
Recognized in loan securitization transactions	13,696	'	'
Amortization	-44,821	-41,095	-36,364
Amortized value, ending balance	126,377	104,855	131,264
Valuation allowance	-300	-4,500	-1,800
Ending balance, net	126,077	100,355	129,464
Commercial Mortgage Loans [Member]	'	'	'
Servicing Asset at Amortized Cost [Line Items]	'	'	'
Amortized value, Beginning balance	59,978	51,250	42,613
Originations	26,754	19,653	17,613
Amortization	-14,233	-10,925	-8,976
Amortized value, ending balance	72,499	59,978	51,250
Ending balance, net	$72,499	$59,978	$51,250

Capitalized_servicing_assets_A

Capitalized servicing assets - Additional Information (Detail) (USD $)

1 Months Ended

12 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Residential Mortgage Loans [Member]

Residential Mortgage Loans [Member]

Residential Mortgage Loans [Member]

Residential Mortgage Sub Servicing Loan [Member]

Residential Mortgage Sub Servicing Loan [Member]

Residential Mortgage Sub Servicing Loan [Member]

Commercial Mortgage Loans [Member]

Commercial Mortgage Loans [Member]

Commercial Mortgage Loans [Member]

Commercial Mortgage Loans [Member]

Commercial Mortgage Loans [Member]

Commercial Mortgage Loans [Member]

Servicing Assets at Fair Value [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Mortgage loans serviced for others

'

'

$69,100,000,000

$32,100,000,000

$36,300,000,000

$46,600,000,000

$12,500,000,000

$14,300,000,000

$4,400,000,000

$3,800,000,000

$4,400,000,000

$11,400,000,000

$10,600,000,000

$9,000,000,000

Estimated fair value of capitalized mortgage loan servicing assets

'

'

266,000,000

138,000,000

'

'

'

'

'

'

'

85,000,000

71,000,000

'

Weighted average discount rates used to estimate fair value of capitalized mortgaged loan servicing assets

'

'

9.30%

10.60%

'

'

'

'

'

'

'

18.00%

18.00%

'

Weighted-average option-adjusted spread in the discount rate

'

'

'770 basis points

'929 basis points

'

'

'

'

'

'

'

'

'

'

Residential mortgage loans securitized formerly held in Company's portfolio

'

1,300,000,000

'

'

'

'

'

'

'

'

'

'

'

'

Automobile loans securitized and sold

$1,400,000,000

$1,400,000,000

'

'

'

'

'

'

'

'

'

'

'

'

Capitalized_servicing_assets_E

Capitalized servicing assets - Economic Assumptions Used to Determine Fair Value of Capitalized Servicing Rights and Sensitivity of Value to Changes in Assumptions (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013
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	11.39%
Impact on fair value of 10% adverse change	($11,283,000)
Impact on fair value of 20% adverse change	-21,664,000
Weighted-average OAS	7.70%
Impact on fair value of 10% adverse change	-5,714,000
Impact on fair value of 20% adverse change	-11,155,000
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%
Impact on fair value of 10% adverse change	-3,677,000
Impact on fair value of 20% adverse change	($7,096,000)

Goodwill_and_other_intangible_2

Goodwill and other intangible assets - Total Amortizing Intangible Assets (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	$933,062	$933,062
Accumulated Amortization	864,211	817,299
Net Carrying Amount	68,851	115,763
Core deposit [Member]	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	755,794	755,794
Accumulated Amortization	705,518	670,940
Net Carrying Amount	50,276	84,854
Other [Member]	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Gross Carrying Amount	177,268	177,268
Accumulated Amortization	158,693	146,359
Net Carrying Amount	$18,575	$30,909

Goodwill_and_other_intangible_3

Goodwill and other intangible assets - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Goodwill And Other Intangible Assets [Line Items]	'	'	'
Useful lives of core deposit and other intangible assets	'8 years	'	'
Remaining weighted-average amortization period	'3 years	'	'
Amortization of core deposit and other intangible assets	$46,912,000	$60,631,000	$61,617,000
Core deposit and other intangible assets [Member]	'	'	'
Goodwill And Other Intangible Assets [Line Items]	'	'	'
Amortization of core deposit and other intangible assets	$46,912,000	$60,631,000	$61,617,000
Minimum [Member]	'	'	'
Goodwill And Other Intangible Assets [Line Items]	'	'	'
Useful lives of core deposit and other intangible assets	'5 years	'	'
Maximum [Member]	'	'	'
Goodwill And Other Intangible Assets [Line Items]	'	'	'
Useful lives of core deposit and other intangible assets	'10 years	'	'

Recovered_Sheet2

Goodwill and Other Intangible Assets - Estimated Amortization Expense in Future Years (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Goodwill And Intangible Assets Disclosure [Abstract]	'	'
2014	$33,825	'
2015	20,938	'
2016	10,052	'
2017	3,303	'
2018	733	'
Future Amortization Expense, Total	$68,851	$115,763

Goodwill_and_other_intangible_4

Goodwill and other intangible assets - Summary of Goodwill Assigned to Reportable Segments for Purposes of Testing for Impairment (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012	31-May-11
In Thousands, unless otherwise specified
Goodwill [Line Items]	'	'	'
Goodwill	$3,524,625	$3,524,625	$0
Business Banking [Member]	'	'	'
Goodwill [Line Items]	'	'	'
Goodwill	748,907	748,907	'
Commercial Banking [Member]	'	'	'
Goodwill [Line Items]	'	'	'
Goodwill	907,524	907,524	'
Commercial Real Estate [Member]	'	'	'
Goodwill [Line Items]	'	'	'
Goodwill	349,197	349,197	'
Discretionary Portfolio [Member]	'	'	'
Goodwill [Line Items]	'	'	'
Goodwill	'	'	'
Residential Mortgage Banking [Member]	'	'	'
Goodwill [Line Items]	'	'	'
Goodwill	'	'	'
Retail Banking [Member]	'	'	'
Goodwill [Line Items]	'	'	'
Goodwill	1,144,404	1,144,404	'
All Other [Member]	'	'	'
Goodwill [Line Items]	'	'	'
Goodwill	$374,593	$374,593	'

Borrowings_Amounts_and_Interes

Borrowings - Amounts and Interest Rates of Short-term Borrowings (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule Of Borrowings [Line Items]	'	'	'
Federal funds purchased and short term borrowings	$260,455	$1,074,482	$782,082
Weighted-average interest rate	0.04%	0.11%	0.09%
Daily-average amount outstanding	390,034	838,902	826,808
Weighted-average interest rate	0.11%	0.15%	0.12%
Federal Funds Purchased and Repurchase Agreements [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Federal Funds Purchased and Repurchase Agreements	260,455	1,074,482	732,059
Weighted-average interest rate	0.04%	0.11%	0.04%
Highest amount at a month-end	563,879	1,224,194	1,389,237
Daily-average amount outstanding	390,034	822,859	706,749
Weighted-average interest rate	0.11%	0.15%	0.11%
Other Short-term Borrowings [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Other Short-term borrowings	'	'	50,023
Weighted-average interest rate	'	'	0.70%
Highest amount at a month-end	'	50,016	142,927
Daily-average amount outstanding	'	$16,043	$120,059
Weighted-average interest rate	'	0.57%	0.18%

Borrowings_Additional_Informat

Borrowings - Additional Information (Detail) (USD $)

12 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Jan. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 31, 2013

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Minimum [Member]

Maximum [Member]

Subsequent Event [Member]

Libor Rate [Member]

FHLB Atlanta [Member]

FHLB Atlanta [Member]

FHLB Atlanta [Member]

M&T (Consolidated) [Member]

M&T Bank [Member]

Federal Reserve Bank of New York [Member]

Variable Rate Notes Due 2016 [Member]

1.45% due 2018 [Member]

1.45% due 2018 [Member]

1.45% due 2018 [Member]

Long-term Variable Rate Advances From FHLB [Member]

Long-term Fixed Rate Advances From FHLB [Member]

Long-term Fixed Rate Advances From FHLB [Member]

Junior Subordinated Debenture Due January 31, 2068 [Member]

Schedule Of Borrowings [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Federal funds purchased and short-term repurchase agreements outstanding

'

'

'

'

'

'

'

$0

$0

$50,000,000

'

'

'

'

'

'

'

'

'

'

'

Maximum amount of borrower using revolving credit agreement

'

'

'

'

'

'

'

'

'

'

30,000,000

'

'

'

'

'

'

'

'

'

'

Borrowing facilities available with FHLB's amount

'

'

'

'

'

'

'

'

'

'

'

8,300,000,000

'

'

'

'

'

'

'

'

'

Line of credit facility

'

'

'

'

'

'

'

'

'

'

'

'

11,800,000,000

'

'

'

'

'

'

'

'

Revolving credit maturity date

'

'

'

'

'

'

'

'

'

'

21-Nov-14

'

'

'

'

'

'

'

'

'

'

Unsecured senior and subordinated notes that may be issued under Bank Note Program

'

'

5,000,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt maturity date

'

'

'

'

'

'

'

'

'

'

'

'

'

'2016

'2018

'2018

'2018

'

'

'

'

Variable rates

'

'

'

'

'

'

'

'

'

'

'

'

'

300,000,000

500,000,000

502,479,000

'

'

'

'

'

Interest rate of debt instrument

'

'

'

'

'

8.50%

0.54%

'

'

'

'

'

'

'

1.45%

1.45%

1.45%

'

'

'

'

Variable contractual interest rate of long-term debt lower limit

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.00%

3.48%

3.48%

'

Variable contractual interest rate of long-term debt upper limit

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.00%

7.32%

7.32%

'

Weighted-average contractual variable interest rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.00%

4.60%

4.64%

'

Advances from the FHLB maturity date

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'2035

'

'

'

Minimum contractual interest rates of long-term agreements to repurchase securities

3.61%

3.61%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum contractual interest rates of long-term agreements to repurchase securities

4.30%

4.30%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted-average contractual interest rates of long term agreements to repurchase securities

3.90%

3.90%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Repurchase dates of the long-term agreements outstanding

'2017

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Collateralized Financings

1,600,000,000

1,600,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Trust preferred capital securities

25.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Minimum variable interest rate of Junior Subordinated Debentures

1.09%

1.16%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum variable interest rate of Junior Subordinated Debentures

3.59%

3.69%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted-average variable rates payable on Junior Subordinated Debentures

'

'

'

1.67%

1.75%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Junior subordinated debentures

'

'

'

'

'

$350,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$350,000,000

Junior Subordinated Debentures Maturity Date

31-Jan-68

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Maturity, Start Year

1-Jan-27

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Maturity, End Year

31-Dec-68

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Borrowings_Lines_of_Credit_Und

Borrowings - Lines of Credit Under Formal Agreements (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
M&T (Consolidated) [Member]	'
Schedule Of Borrowings [Line Items]	'
Outstanding borrowings	'
Unused	30,000
M&T Bank [Member]	'
Schedule Of Borrowings [Line Items]	'
Outstanding borrowings	28,868
Unused	19,838,117
Wilmington Trust, N.A. [Member]	'
Schedule Of Borrowings [Line Items]	'
Outstanding borrowings	'
Unused	$300,710

Borrowings_Longterm_Borrowings

Borrowings - Long-term Borrowings (Detail) (USD $)	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule Of Borrowings [Line Items]	'	'	'
Fixed rates	$29,079	'	$30,066
Agreements to repurchase securities	1,400,000	'	1,400,000
Other	30,257	'	40,792
Long-term borrowings	5,108,870	'	4,607,758
Variable Rate Notes Due 2016 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Variable rates	300,000	'	'
1.45% due 2018 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Variable rates	502,479	500,000	'
4.875% due 2013 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Subordinated notes	0	'	251,298
8.5% due 2018 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Subordinated notes	224,067	'	230,255
6.625% due 2017 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Subordinated notes	437,582	'	455,439
9.5% due 2018 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Subordinated notes	50,000	'	50,000
5.585% due 2020, variable rate commencing 2015 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Subordinated notes	392,964	'	385,669
5.629% due 2021, variable rate commencing 2016 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Subordinated notes	559,378	'	583,097
M&T Capital Trust I - 8.234%, due 2027 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Junior subordinated debentures associated with preferred capital securities	154,640	'	154,640
M&T Capital Trust II - 8.277%, due 2027 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Junior subordinated debentures associated with preferred capital securities	103,093	'	103,093
M&T Capital Trust III - 9.25%, due 2027 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Junior subordinated debentures associated with preferred capital securities	66,109	'	66,434
BSB Capital Trust I - 8.125%, due 2028 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Junior subordinated debentures associated with preferred capital securities	15,589	'	15,566
Provident Trust I - 8.29%, due 2028 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Junior subordinated debentures associated with preferred capital securities	25,051	'	24,746
Southern Financial Statutory Trust I - 10.60%, due 2030 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Junior subordinated debentures associated with preferred capital securities	6,521	'	6,496
M&T Capital Trust IV - 8.50%, due 2068 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Junior subordinated debentures associated with preferred capital securities	350,010	'	350,010
First Maryland Capital I - due 2027 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Junior subordinated debentures associated with preferred capital securities	144,641	'	144,102
First Maryland Capital II - due 2027 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Junior subordinated debentures associated with preferred capital securities	145,964	'	145,301
Allfirst Asset Trust - due 2029 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Junior subordinated debentures associated with preferred capital securities	96,059	'	95,913
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 Trust III - due 2033 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Junior subordinated debentures associated with preferred capital securities	52,176	'	51,694
Southern Financial Capital Trust III - due 2033 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Junior subordinated debentures associated with preferred capital securities	$7,747	'	$7,683

Borrowings_Longterm_Borrowings1

Borrowings - Long-term Borrowings (Parenthetical) (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Borrowings [Line Items]	'	'	'
Debt Maturity, Start Date	'	1-Jan-27	'
Debt Maturity, End Date	'	31-Dec-68	'
Variable rate due 2016 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Debt maturity date	'	'2016	'2016
1.45% due 2018 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	1.45%	1.45%	1.45%
Debt maturity date	'2018	'2018	'2018
4.875% due 2013 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	'	4.88%	4.88%
Debt maturity date	'	'2013	'2013
8.5% due 2018 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	'	8.50%	8.50%
Debt maturity date	'	'2018	'2018
6.625% due 2017 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	'	6.63%	6.63%
Debt maturity date	'	'2017	'2017
9.5% due 2018 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	'	9.50%	9.50%
Debt maturity date	'	'2018	'2018
5.585% due 2020, variable rate commencing 2015 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	'	5.59%	5.59%
Debt Maturity, Start Date	'	1-Jan-15	1-Jan-15
Debt Maturity, End Date	'	31-Dec-20	31-Dec-20
5.629% due 2021, variable rate commencing 2016 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	'	5.63%	5.63%
Debt Maturity, Start Date	'	1-Jan-16	1-Jan-16
Debt Maturity, End Date	'	31-Dec-21	31-Dec-21
M&T Capital Trust I - 8.234%, due 2027 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	'	8.23%	8.23%
Debt maturity date	'	'2027	'2027
M&T Capital Trust II - 8.277%, due 2027 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	'	8.28%	8.28%
Debt maturity date	'	'2027	'2027
M&T Capital Trust III - 9.25%, due 2027 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	'	9.25%	9.25%
Debt maturity date	'	'2027	'2027
BSB Capital Trust I - 8.125%, due 2028 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	'	8.13%	8.13%
Debt maturity date	'	'2028	'2028
Provident Trust I - 8.29%, due 2028 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	'	8.29%	8.29%
Debt maturity date	'	'2028	'2028
Southern Financial Statutory Trust I - 10.60%, due 2030 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	'	10.60%	10.60%
Debt maturity date	'	'2030	'2030
M&T Capital Trust IV - 8.50%, due 2068 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Interest rate of debt instrument	'	8.50%	8.50%
Debt maturity date	'	'2068	'2068
First Maryland Capital I - due 2027 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Debt maturity date	'	'2027	'2027
First Maryland Capital II - due 2027 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Debt maturity date	'	'2027	'2027
Allfirst Asset Trust - due 2029 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Debt maturity date	'	'2029	'2029
BSB Capital Trust III - due 2033 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Debt maturity date	'	'2033	'2033
Provident Trust III - due 2033 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Debt maturity date	'	'2033	'2033
Southern Financial Capital Trust III - due 2033 [Member]	'	'	'
Schedule Of Borrowings [Line Items]	'	'	'
Debt maturity date	'	'2033	'2033

Borrowings_Maturity_of_Longter

Borrowings - Maturity of Long-term Borrowings (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Debt Disclosure [Abstract]	'	'
2014	$22,021	'
2015	5,756	'
2016	1,105,075	'
2017	1,041,871	'
2018	777,991	'
Later years	2,156,156	'
Long-term borrowings	$5,108,870	$4,607,758

Shareholders_equity_Additional

Shareholders' equity - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Class of Stock [Line Items]	'	'
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, par value	$1	$1
Exercise price of each class of warrants or rights outstanding	'	26.5
Ten Year Warrant Series D Preferred [Member]	'	'
Class of Stock [Line Items]	'	'
Exercise price of each class of warrants or rights outstanding	518.96	518.96
Ten-year warrant to purchase common stock	95,383	95,383
Warrant issue date	'2008-12	'

Shareholders_equity_Issued_and

Shareholders' equity - Issued and Outstanding Preferred Stock (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Class of Stock [Line Items]	'	'
Carrying value	$881,500	$872,500
Series A Fixed Rate Cumulative Perpetual Preferred Stock [Member]	'	'
Class of Stock [Line Items]	'	'
Preferred stock, shares issued and outstanding	230,000	230,000
Carrying value	230,000	226,965
Series C Fixed Rate Cumulative Perpetual Preferred Stock [Member]	'	'
Class of Stock [Line Items]	'	'
Preferred stock, shares issued and outstanding	151,500	151,500
Carrying value	151,500	145,535
Series D Fixed Rate Non-Cumulative Perpetual Preferred Stock [Member]	'	'
Class of Stock [Line Items]	'	'
Preferred stock, shares issued and outstanding	50,000	50,000
Carrying value	$500,000	$500,000

Shareholders_equity_Issued_and1

Shareholders' equity - Issued and Outstanding Preferred Stock (Parenthetical) (Detail) (USD $)

1 Months Ended

12 Months Ended

1 Months Ended

1 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

Aug. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Aug. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Aug. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 31, 2013

Sep. 30, 2013

Dec. 31, 2013

Dec. 31, 2013

Series A Fixed Rate Cumulative Perpetual Preferred Stock [Member]

Series A Fixed Rate Cumulative Perpetual Preferred Stock [Member]

Series C Fixed Rate Cumulative Perpetual Preferred Stock [Member]

Series C Fixed Rate Cumulative Perpetual Preferred Stock [Member]

Series D Fixed Rate Non-Cumulative Perpetual Preferred Stock [Member]

Series D Fixed Rate Non-Cumulative Perpetual Preferred Stock [Member]

Ten Year Warrant Series A Preferred [Member]

Series A [Member]

Series A [Member]

Ten Year Warrant Series C Preferred [Member]

Series C [Member]

Series C [Member]

Preferred series A and C First Five Years [Member]

Preferred series A and C After Five Years [Member]

Series C warrants [Member]

Series A Warrants [Member]

Series A Warrants [Member]

Series D [Member]

Class of Stock [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Liquidation preference

'

'

'

$1,000

$1,000

$1,000

$1,000

$10,000

$10,000

'

'

'

'

'

'

'

'

'

'

'

'

Ten-year warrant to purchase common stock

'

'

'

'

'

'

'

'

'

1,218,522

'

'

407,542

'

'

'

'

'

'

'

'

Exercise price of each class of warrants or rights outstanding

'

'

26.5

'

'

'

'

'

'

'

'

73.86

'

'

55.76

'

'

'

'

'

'

Preferred stock dividend rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5.00%

6.38%

'

'

'

6.88%

Date of change in the dividend rate

14-Nov-13

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Preferred shares redemption date

'

'

'

'

'

'

'

'

'

'

15-Nov-18

'

'

15-Nov-18

'

'

'

'

'

'

15-Jun-16

Issuance of common shares

'

130,516,364

128,176,912

'

'

'

'

'

'

'

'

'

'

'

'

'

'

186,589

'

'

'

Cashless warrants exercised

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

69,127

'

'

Common stock shares, Issued as a result of warrants exercised

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25,427

'

'

Warrants and rights outstanding

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,149,395

'

Redemption days of shares by Company

'

'90 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stockbased_compensation_plans_1

Stock-based compensation plans - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock-based compensation expense	$55,000,000	$57,000,000	$56,000,000
Recognized income tax benefits related to stock-based compensation	29,000,000	30,000,000	22,000,000
Shares under equity incentive compensation plan for future grant	4,874,542	5,307,228	'
Directors stock plan [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Shares issuable under deferred compensation plans	14,185	18,816	'
Shares issued in connection with deferred compensation plans	197,905	'	'
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	172,000,000	153,000,000	28,000,000
Tax benefits realized from exercise of stock options	12,000,000	8,000,000	3,000,000
Intrinsic value of stock options exercised	34,000,000	21,000,000	7,000,000
Total grant date fair value of stock options vested	0	17,000,000	29,000,000
Restricted Stock Awards [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Vesting period	'4 years	'	'
Unrecognized compensation cost expected to be recognized over a weighted-average period (in years)	'1 year 6 months	'	'
Unrecognized compensation cost related to non-vested awards	27,000,000	'	'
Shares issued	269,755	453,908	451,248
Weighted-average grant date fair value	27,716,000	36,969,000	38,369,000
Restricted Stock Units [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Unrecognized compensation cost expected to be recognized over a weighted-average period (in years)	'1 year 4 months 24 days	'	'
Unrecognized compensation cost related to non-vested awards	9,000,000	'	'
Shares issued	315,316	278,505	242,282
Weighted-average grant date fair value	32,380,000	22,139,000	20,921,000
Stock Purchase Plan [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Shares issued	0	151,014	0
Common stock authorized for issuance	2,500,000	'	'
Common stock issued through employee stock purchase plan	0	'	'
Cash received from exercise of stock options	$0	$10,117,000	'
Deferred bonus plan [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Shares issuable under deferred compensation plans	33,046	38,593	'
Shares issued in connection with deferred compensation plans	139,429	'	'

Stockbased_compensation_plans_2

Stock-based compensation plans - Summary of Restricted Stock and Restricted Stock Unit Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013
Restricted Stock Units (RSUs) [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Restricted Stock Outstanding, Unvested, Beginning balance	799,495
Restricted Stock Outstanding, Granted	315,316
Restricted Stock Outstanding, Vested	-341,348
Restricted Stock Outstanding, Cancelled	-2,633
Restricted Stock Outstanding, Unvested, Ending balance	770,830
Weighted-Average Grant Price, Unvested, Beginning balance	$70.28
Weighted-Average Grant Price, Granted	$102.69
Weighted-Average Grant Price, Vested	$56.43
Weighted-Average Grant Price, Cancelled	$96.90
Weighted-Average Grant Price, Unvested, Ending balance	$89.58
Restricted Stock [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Restricted Stock Outstanding, Unvested, Beginning balance	1,095,631
Restricted Stock Outstanding, Granted	269,755
Restricted Stock Outstanding, Vested	-446,882
Restricted Stock Outstanding, Cancelled	-55,809
Restricted Stock Outstanding, Unvested, Ending balance	862,695
Weighted-Average Grant Price, Unvested, Beginning balance	$71.01
Weighted-Average Grant Price, Granted	$102.75
Weighted-Average Grant Price, Vested	$56.74
Weighted-Average Grant Price, Cancelled	$87.05
Weighted-Average Grant Price, Unvested, Ending balance	$87.29

Stockbased_compensation_plans_3

Stock-based compensation plans - Summary of Stock Option Activity (Detail) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock Options Outstanding, Beginning balance	7,033,359
Stock Options Outstanding, Granted	100
Stock Options Outstanding, Exercised	-1,998,841
Stock Options Outstanding, Expired	-153,857
Stock Options Outstanding, Ending balance	4,880,761
Stock Options Outstanding, Exercisable	4,879,148
Weighted-Average Exercise Price, Outstanding, Beginning balance	$103.30
Weighted-Average Exercise Price, Granted	$102.69
Weighted-Average Exercise Price, Exercised	$95.27
Weighted-Average Exercise Price, Expired	$138.46
Weighted-Average Exercise Price, Outstanding, Ending balance	$105.48
Weighted-Average Exercise Price, Exercisable	$105.49
Weighted-Average Life (In Years), Outstanding, Ending balance	'2 years 9 months 18 days
Weighted-Average Life (In Years), Exercisable	'2 years 9 months 18 days
Aggregate Intrinsic Value, Outstanding, Ending balance	$66,464
Aggregate Intrinsic Value, Exercisable	$66,400

Recovered_Sheet3

Pension Plans and Other Postretirement Benefits - Net Periodic Benefit Cost for Defined Benefit Plans (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Benefits [Member]	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Service cost	$24,360	$29,549	$28,828
Interest cost on benefit obligation	60,130	62,037	58,545
Expected return on plan assets	-87,353	-70,511	-60,700
Amortization of prior service cost (credit)	-6,556	-6,559	-6,559
Recognized net actuarial loss	41,076	37,386	20,530
Net periodic benefit costs	31,657	51,902	40,644
Other Postretirement Benefits [Member]	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Service cost	742	668	535
Interest cost on benefit obligation	2,691	3,737	3,761
Amortization of prior service cost (credit)	-1,359	21	107
Recognized net actuarial loss	360	530	36
Net periodic benefit costs	$2,434	$4,956	$4,439

Pension_plans_and_other_postre2

Pension plans and other postretirement benefits - Data Relating to Funding Position of Defined Benefit Plans (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Fair value of plan assets at end of year	$1,504,691,000	$1,404,138,000	'
Pension Benefits [Member]	'	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Benefit obligation at beginning of year	1,644,567,000	1,496,490,000	'
Service cost	24,360,000	29,549,000	28,828,000
Interest cost	60,130,000	62,037,000	58,545,000
Plan participants' contributions	'	'	'
Amendments	'	'	'
Actuarial (gain) loss	-184,181,000	116,237,000	'
Settlements/curtailments	'	-320,000	'
Medicare Part D reimbursement	'	'	'
Benefits paid	-60,683,000	-59,426,000	'
Benefit obligation at end of year	1,484,193,000	1,644,567,000	1,496,490,000
Fair value of plan assets at beginning of year	1,408,771,000	1,117,972,000	'
Actual return on plan assets	150,795,000	143,430,000	'
Employer contributions	7,801,000	207,115,000	'
Plan participants' contributions	'	'	'
Medicare Part D reimbursement	'	'	'
Settlements	'	-320,000	'
Benefits and other payments	-60,683,000	-59,426,000	'
Fair value of plan assets at end of year	1,506,684,000	1,408,771,000	1,117,972,000
Funded status	22,491,000	-235,796,000	'
Net prepaid asset	139,576,000	'	'
Accrued liabilities	-117,085,000	-235,796,000	'
Net loss (gain)	191,386,000	480,084,000	'
Net prior service cost	-16,899,000	-23,455,000	'
Pre-tax adjustment to AOCI	174,487,000	456,629,000	'
Taxes	-68,486,000	-179,227,000	'
Net adjustment to AOCI	106,001,000	277,402,000	'
Other Postretirement Benefits [Member]	'	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Benefit obligation at beginning of year	74,966,000	90,104,000	'
Service cost	742,000	668,000	535,000
Interest cost	2,691,000	3,737,000	3,761,000
Plan participants' contributions	3,069,000	3,765,000	'
Amendments	'	-13,313,000	'
Actuarial (gain) loss	-12,830,000	-182,000	'
Settlements/curtailments	'	'	'
Medicare Part D reimbursement	509,000	918,000	'
Benefits paid	-8,555,000	-10,731,000	'
Benefit obligation at end of year	60,592,000	74,966,000	90,104,000
Fair value of plan assets at beginning of year	'	'	'
Actual return on plan assets	'	'	'
Employer contributions	4,977,000	6,048,000	'
Plan participants' contributions	3,069,000	3,765,000	'
Medicare Part D reimbursement	509,000	918,000	'
Settlements	'	'	'
Benefits and other payments	-8,555,000	-10,731,000	'
Fair value of plan assets at end of year	'	'	'
Funded status	-60,592,000	-74,966,000	'
Net prepaid asset	'	'	'
Accrued liabilities	-60,592,000	-74,966,000	'
Net loss (gain)	-1,056,000	12,134,000	'
Net prior service cost	-11,814,000	-13,173,000	'
Pre-tax adjustment to AOCI	-12,870,000	-1,039,000	'
Taxes	5,051,000	408,000	'
Net adjustment to AOCI	($7,819,000)	($631,000)	'

Pension_plans_and_other_postre3

Pension plans and other postretirement benefits - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Minimum pension liability	$161,617,000	'	'
Minimum pension liability adjustment net of tax	98,182,000	'	'
Discount rate of benefit plan	4.75%	3.75%	'
Decrease in minimum liability adjustment	'	293,973,000	'
Increase in minimum pension liability adjustment net of tax	'	178,589,000	'
Defined contribution pension and retirement savings plans total expense	21,000,000	17,000,000	13,000,000
Annual rate of increase in health care cost assumed for next fiscal year	7.50%	'	'
Defined Benefit Plan, ultimate health care cost trend rate	5.00%	'	'
Period for decreasing the annual rate	'Over 30 years	'	'
Defined benefit pension plans	168,040,000	'	'
Percentage of total assets	11.20%	'	'
Defined benefit plan fair value of plan assets	1,504,691,000	1,404,138,000	'
Percentage of pension plan assets that is not exceeded by investment in security of single Non-US Government of Government agency	10.00%	'	'
Qualified benefit pension plans	0	200,000,000	70,000,000
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	31,797,000	31,305,000	27,738,000
Total Equity Securities [Member]	'	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Target allocations for plan assets, minimum range	45.00%	'	'
Target allocations for plan assets, maximum range	80.00%	'	'
Defined benefit plan fair value of plan assets	1,045,995,000	674,503,000	'
Total Debt securities [Member]	'	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Target allocations for plan assets, minimum range	5.00%	'	'
Target allocations for plan assets, maximum range	40.00%	'	'
Defined benefit plan fair value of plan assets	252,704,000	621,104,000	'
Other Securities [Member]	'	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Target allocations for plan assets, minimum range	3.00%	'	'
Target allocations for plan assets, maximum range	30.00%	'	'
Defined benefit plan fair value of plan assets	168,040,000	61,874,000	'
M&T Equity securities [Member]	'	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Defined benefit plan fair value of plan assets	142,955,000	120,914,000	'
Percentage of common stock in total plan assets	9.50%	8.60%	'
Supplemental pension plan [Member]	'	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Projected benefit obligation	117,085,000	'	'
Accumulated benefit obligation	'	130,745,000	'
Employer contributions	7,801,000	7,115,000	'
Pension Benefits [Member]	'	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Projected benefit obligation	1,484,193,000	1,644,567,000	1,496,490,000
Accumulated benefit obligation	1,460,498,000	1,618,119,000	'
Minimum pension liability	174,487,000	'	'
Discount rate of benefit plan	3.75%	4.25%	5.25%
Defined benefit plan fair value of plan assets	1,506,684,000	1,408,771,000	1,117,972,000
Employer contributions	7,801,000	207,115,000	'
Other Postretirement Benefits [Member]	'	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Projected benefit obligation	60,592,000	74,966,000	90,104,000
Minimum pension liability	-12,870,000	'	'
Discount rate of benefit plan	3.75%	4.25%	5.25%
Defined benefit plan fair value of plan assets	'	'	'
Employer contributions	$4,977,000	$6,048,000	'

Pension_plans_and_other_postre4

Pension plans and other postretirement benefits - Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Net loss (gain)	($260,452)	$43,136	'
Prior service credit	'	-13,313	'
Amortization of prior service (cost) credit	7,915	6,538	6,452
Amortization of loss	-41,436	-37,916	-20,566
Total recognized in other comprehensive income, pre-tax	-293,973	-1,555	'
Pension Benefits [Member]	'	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Net loss (gain)	-247,622	43,318	'
Amortization of prior service (cost) credit	6,556	6,559	'
Amortization of loss	-41,076	-37,386	'
Total recognized in other comprehensive income, pre-tax	-282,142	12,491	'
Other Postretirement Benefits [Member]	'	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Net loss (gain)	-12,830	-182	'
Prior service credit	'	-13,313	'
Amortization of prior service (cost) credit	1,359	-21	'
Amortization of loss	-360	-530	'
Total recognized in other comprehensive income, pre-tax	($11,831)	($14,046)	'

Pension_plans_and_other_postre5

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) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013
Pension Benefits [Member]	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'
Amortization of net prior service credit	($6,552)
Amortization of net loss	13,460
Other Postretirement Benefits [Member]	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'
Amortization of net prior service credit	($1,359)

Pension_plans_and_other_postre6

Pension plans and other postretirement benefits - Assumed Weighted-Average Rates Used to Determine Benefit Obligations (Detail)	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Discount rate	4.75%	3.75%
Rate of increase in future compensation levels	4.42%	4.50%
Other Postretirement Benefits [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Discount rate	4.75%	3.75%
Rate of increase in future compensation levels	'	'

Pension_plans_and_other_postre7

Pension plans and other postretirement benefits - Assumed Weighted-Average Rates Used to Determine Net Benefit Expense (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Discount rate	4.75%	3.75%	'
Pension Benefits [Member]	'	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Discount rate	3.75%	4.25%	5.25%
Long-term rate of return on plan assets	6.50%	6.50%	6.50%
Rate of increase in future compensation levels	4.50%	4.50%	4.50%
Other Postretirement Benefits [Member]	'	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'	'
Discount rate	3.75%	4.25%	5.25%

Pension_plans_and_other_postre8

Pension plans and other postretirement benefits - Effects on One-Percentage Point Change in Assumed Health Care Cost Trend Rates (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013
Compensation And Retirement Disclosure [Abstract]	'
Service and interest cost	$100
Accumulated postretirement benefit obligation	2,147
Service and interest cost	-91
Accumulated postretirement benefit obligation	($1,947)

Pension_plans_and_other_postre9

Pension plans and other postretirement benefits - Fair Values of Company's Pension Plan Assets by Asset Category (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	$1,504,691	$1,404,138
Money-market funds [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	37,952	46,657
M&T Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	142,955	120,914
Domestic Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	271,203	147,382
International Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	24,053	8,561
Domestic Mutual Fund Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	194,099	188,950
International Mutual Fund Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	413,685	208,696
Total Equity Securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	1,045,995	674,503
Corporate Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	63,196	307,712
Government Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	75,043	141,224
International Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	2,443	10,230
Domestic Mutual Fund Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	68,280	107,576
International Mutual Fund Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	43,742	54,362
Total Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	252,704	621,104
Other Diversified mutual fund [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	93,055	10,415
Other Private real estate [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	3,123	4,603
Other Private equity [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	6,199	5,347
Other Hedge funds [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	65,663	41,509
Other Securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	168,040	61,874
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	1,330,513	903,513
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money-market funds [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	37,952	46,657
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | M&T Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	142,955	120,914
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Domestic Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	271,203	147,382
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | International Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	24,053	8,561
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Domestic Mutual Fund Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	194,099	188,950
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | International Mutual Fund Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	413,685	208,696
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Total Equity Securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	1,045,995	674,503
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Government Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | International Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Domestic Mutual Fund Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	68,280	107,576
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | International Mutual Fund Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	43,742	54,362
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Total Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	112,022	161,938
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Diversified mutual fund [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	93,055	10,415
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Private real estate [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Private equity [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Hedge funds [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	41,489	10,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	134,544	20,415
Significant Observable Inputs (Level 2) [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	140,682	459,166
Significant Observable Inputs (Level 2) [Member] | Money-market funds [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Observable Inputs (Level 2) [Member] | M&T Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Observable Inputs (Level 2) [Member] | Domestic Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Observable Inputs (Level 2) [Member] | International Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Observable Inputs (Level 2) [Member] | Domestic Mutual Fund Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Observable Inputs (Level 2) [Member] | International Mutual Fund Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Observable Inputs (Level 2) [Member] | Total Equity Securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Observable Inputs (Level 2) [Member] | Corporate Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	63,196	307,712
Significant Observable Inputs (Level 2) [Member] | Government Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	75,043	141,224
Significant Observable Inputs (Level 2) [Member] | International Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	2,443	10,230
Significant Observable Inputs (Level 2) [Member] | Domestic Mutual Fund Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Observable Inputs (Level 2) [Member] | International Mutual Fund Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Observable Inputs (Level 2) [Member] | Total Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	140,682	459,166
Significant Observable Inputs (Level 2) [Member] | Other Diversified mutual fund [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Observable Inputs (Level 2) [Member] | Other Private real estate [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Observable Inputs (Level 2) [Member] | Other Private equity [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Observable Inputs (Level 2) [Member] | Other Hedge funds [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Observable Inputs (Level 2) [Member] | Other Securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	33,496	41,459
Significant Unobservable Inputs (Level 3) [Member] | Money-market funds [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | M&T Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | Domestic Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | International Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | Domestic Mutual Fund Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | International Mutual Fund Equity securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | Total Equity Securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | Corporate Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | Government Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | International Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | Domestic Mutual Fund Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | International Mutual Fund Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | Total Debt securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | Other Diversified mutual fund [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	'	'
Significant Unobservable Inputs (Level 3) [Member] | Other Private real estate [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	3,123	4,603
Significant Unobservable Inputs (Level 3) [Member] | Other Private equity [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	6,199	5,347
Significant Unobservable Inputs (Level 3) [Member] | Other Hedge funds [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	24,174	31,509
Significant Unobservable Inputs (Level 3) [Member] | Other Securities [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Defined benefit plan fair value of plan assets	$33,496	$41,459

Recovered_Sheet4

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, 2013	Dec. 31, 2012
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Interest and dividend receivable on plan assets	$1,993,000	$4,633,000
Investment grade bonds of U.S. issuers [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Investment in mutual funds	35.00%	40.00%
High-yielding bonds [Member]	'	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'	'
Investment in mutual funds	65.00%	60.00%

Recovered_Sheet5

Pension plans and other postretirement benefits - Changes in Level 3 Pension Plan Assets Measured at Fair Value on Recurring Basis (Detail) (USD $)

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

In Thousands, unless otherwise specified

Other Private real estate [Member]

Other Private real estate [Member]

Other Private equity [Member]

Other Private equity [Member]

Other Hedge funds [Member]

Other Hedge funds [Member]

Other Securities [Member]

Other Securities [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Significant Unobservable Inputs (Level 3) [Member]

Other Private real estate [Member]

Other Private equity [Member]

Other Hedge funds [Member]

Other Securities [Member]

Pension Plans, Postretirement and Other Employee Benefits [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair value of plan assets at beginning of year

$1,504,691

$1,404,138

$3,123

$4,603

$6,199

$5,347

$65,663

$41,509

$168,040

$61,874

$33,496

$41,459

$4,603

$5,347

$31,509

$41,459

Sales

'

'

'

'

'

'

'

'

'

'

'

'

-308

165

-9,873

-10,016

Total Realized/Unrealized Gains (Losses)

'

'

'

'

'

'

'

'

'

'

'

'

-1,172

687

2,538

2,053

Fair value of plan assets at end of year

$1,504,691

$1,404,138

$3,123

$4,603

$6,199

$5,347

$65,663

$41,509

$168,040

$61,874

$33,496

$41,459

$3,123

$6,199

$24,174

$33,496

Recovered_Sheet6

Pension plans and other postretirement benefits - Defined Benefit Plan Estimated Future Benefit Payments (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Pension Benefits [Member]	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'
2014	$65,970
2015	67,993
2016	73,628
2017	77,180
2018	80,380
2019 through 2023	461,397
Other Postretirement Benefits [Member]	'
Pension Plans, Postretirement and Other Employee Benefits [Line Items]	'
2014	6,780
2015	6,503
2016	6,283
2017	5,995
2018	5,741
2019 through 2023	$25,172

Income_taxes_Components_of_Inc

Income taxes - Components of Income Tax Expense (Benefit) (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current	'	'	'
Federal	$371,249	$309,156	$277,631
State and city	68,035	82,014	53,566
Total current	439,284	391,170	331,197
Deferred	'	'	'
Federal	106,537	117,229	34,325
State and city	33,248	14,629	-401
Total deferred	139,785	131,858	33,924
Income taxes	$579,069	$523,028	$365,121

Income_taxes_Additional_Inform

Income taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	State
Income Tax Disclosure [Abstract]	'	'	'
Tax bad debt reserve	$79,121,000	'	'
Income taxes attributable to gains or losses on bank investment securities	18,313,000	-18,766,000	28,712,000
Minimum alternative tax expense recognized for gains or losses on bank investment securities	$0	$0	$0
Number of state and local jurisdictions where company files income tax returns	40	'	'

Income_taxes_Schedule_of_Incom

Income taxes - Schedule of Income Taxes Expenses Benefit Reconciliation (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
Income taxes at statutory federal income tax rate	$601,142	$543,384	$428,610
Increase (decrease) in taxes:	'	'	'
Tax-exempt income	-34,747	-33,890	-33,799
State and city income taxes, net of federal income tax effect	65,834	62,818	34,557
Low income housing and other credits	-49,206	-42,074	-40,763
Non-taxable gain on acquisition	'	'	-22,725
Other	-3,954	-7,210	-759
Income taxes	$579,069	$523,028	$365,121

Income_taxes_Deferred_Tax_Asse

Income taxes - Deferred Tax Assets (Liabilities) (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Income Tax Disclosure [Abstract]	'	'	'
Losses on loans and other assets	$645,713	$809,033	$896,219
Postretirement and other employee benefits	30,023	34,517	39,992
Incentive compensation plans	37,772	50,067	49,183
Interest on loans	100,725	72,278	46,965
Retirement benefits	'	91,980	147,997
Stock-based compensation	63,101	69,874	78,014
Unrealized investment losses	'	'	50,528
Depreciation and amortization	1,404	12,130	9,563
Other	121,561	103,027	99,012
Gross deferred tax assets	1,000,299	1,242,906	1,417,473
Leasing transactions	-284,370	-291,524	-294,150
Unrealized investment gains	-21,779	-23,574	'
Capitalized servicing rights	-46,041	-20,348	-17,603
Interest on subordinated note exchange	-6,075	-8,794	-11,275
Retirement benefits	-9,397	'	'
Other	-49,450	-61,410	-48,803
Gross deferred tax liabilities	-417,112	-405,650	-371,831
Net deferred tax asset	$583,187	$837,256	$1,045,642

Income_taxes_Reconciliation_of

Income taxes - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Federal, State and Local Tax [Member]	'	'	'
Reconciliation Of Unrecognized Tax Benefits [Line Items]	'	'	'
Beginning Balance	$16,548	$18,333	$24,853
Increases in unrecognized tax benefits as a result of tax positions taken during the period	2,267	860	4,659
Increases in unrecognized tax benefits as a result of tax positions taken in prior years	'	'	'
Decreases in unrecognized tax benefits as a result of settlements with taxing authorities	-1,854	-1,002	-9,742
Decreases in unrecognized tax benefits as a result of tax positions taken in prior years	'	'	'
Decreases in unrecognized tax benefits because applicable returns are no longer subject to examination	-2,350	-1,643	-8,471
Unrecognized tax benefits acquired in a business combination	'	'	7,034
Ending Balance	14,611	16,548	18,333
Accrued Interest [Member]	'	'	'
Reconciliation Of Unrecognized Tax Benefits [Line Items]	'	'	'
Beginning Balance	12,379	9,277	20,696
Increases in unrecognized tax benefits as a result of tax positions taken during the period	'	'	'
Increases in unrecognized tax benefits as a result of tax positions taken in prior years	4,429	4,514	'
Decreases in unrecognized tax benefits as a result of settlements with taxing authorities	-487	'	-5,497
Decreases in unrecognized tax benefits as a result of tax positions taken in prior years	'	'	-1,645
Decreases in unrecognized tax benefits because applicable returns are no longer subject to examination	-1,625	-1,412	-8,201
Unrecognized tax benefits acquired in a business combination	'	'	3,924
Ending Balance	14,696	12,379	9,277
Unrecognized Income Tax Benefits [Member]	'	'	'
Reconciliation Of Unrecognized Tax Benefits [Line Items]	'	'	'
Beginning Balance	28,927	27,610	45,549
Increases in unrecognized tax benefits as a result of tax positions taken during the period	2,267	860	4,659
Increases in unrecognized tax benefits as a result of tax positions taken in prior years	4,429	4,514	'
Decreases in unrecognized tax benefits as a result of settlements with taxing authorities	-2,341	-1,002	-15,239
Decreases in unrecognized tax benefits as a result of tax positions taken in prior years	'	'	-1,645
Decreases in unrecognized tax benefits because applicable returns are no longer subject to examination	-3,975	-3,055	-16,672
Unrecognized tax benefits acquired in a business combination	'	'	10,958
Ending Balance	29,307	28,927	27,610
Less: Federal, state and local income tax benefits	-9,611	'	'
Net unrecognized tax benefits if recognized, would impact the effective income tax rate	$19,696	'	'

Earnings_Per_Common_Share_Comp

Earnings Per Common Share - Computations of Basic Earnings Per Common Share (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income available to common shareholders:	'	'	'
Net income	$1,138,480	$1,029,498	$859,479
Less: Preferred stock dividends	-54,120	-53,450	-45,839
Amortization of preferred stock discount	-7,942	-8,026	-20,018
Net income available to common equity	1,076,418	968,022	793,622
Less: Income attributable to unvested stock-based compensation awards	-13,989	-14,632	-11,879
Net income available to common shareholders	$1,062,429	$953,390	$781,743
Weighted-average shares outstanding:	'	'	'
Common and unvested stock-based compensation awards	130,354	127,793	124,524
Less: Unvested stock-based compensation awards	-1,700	-1,929	-1,861
Weighted-average shares outstanding	128,654	125,864	122,663
Basic earnings per common share	$8.26	$7.57	$6.37

Earnings_Per_Common_Share_Comp1

Earnings Per Common Share - Computations of Diluted Earnings Per Common Share (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]	'	'	'
Net income available to common equity	$1,076,418	$968,022	$793,622
Less: Income attributable to unvested stock-based compensation awards	-13,922	-14,593	-11,857
Net income available to common shareholders	$1,062,496	$953,429	$781,765
Adjusted weighted-average shares outstanding:	'	'	'
Common and unvested stock-based compensation awards	130,354	127,793	124,524
Less: Unvested stock-based compensation awards	-1,700	-1,929	-1,861
Plus: Incremental shares from assumed conversion of stock-based compensation awards	949	541	416
Adjusted weighted-average shares outstanding	129,603	126,405	123,079
Diluted earnings per common share	$8.20	$7.54	$6.35

Earnings_Per_Common_Share_Addi

Earnings Per Common Share - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]	'	'	'
Antidilutive securities excluded from computation of earnings per share	3,847,000	8,905,000	11,268,000

Comprehensive_Income_Component

Comprehensive Income - Components of Other Comprehensive Income (Loss) and Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) to Net Income (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Components Of Comprehensive Income [Line Items]	'	'	'
Beginning balance	($395,657)	($586,769)	($337,652)
Unrealized holding gains (losses), net	-51,834	134,923	76,576
Foreign currency translation adjustment	546	809	-1,240
Current year pension gains (losses)	260,452	-29,823	-272,260
Total other comprehensive income before reclassifications	209,164	105,909	-196,924
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	4,287	6,190	7,035
OTTI charges recognized in net income	9,800	47,822	77,035
Losses (gains) realized in net income	33,088	-9	-149,929
Amortization of gains on terminated cash flow hedges	'	-178	-448
Amortization of prior service credit	-7,915	-6,538	-6,452
Amortization of actuarial losses	41,436	37,916	20,566
Total reclassifications	80,696	85,203	-52,193
Total gain (loss) during the period	289,860	191,112	-249,117
Ending balance	-105,797	-395,657	-586,769
Beginning balance	155,393	230,328	132,432
Unrealized holding gains(losses), net	20,311	-52,905	-29,786
Foreign currency translation adjustment	-165	-290	437
Current year pension gains (losses)	-102,227	11,705	106,862
Total other comprehensive income before reclassifications	-82,081	-41,490	77,513
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	-1,683	-2,430	-2,762
OTTI charges recognized in net income	-3,847	-18,770	-30,235
Losses (gains) realized in net income	-12,987	4	58,753
Amortization of gains on terminated cash flow hedges	'	66	167
Amortization of prior service credit	3,107	2,566	2,532
Amortization of actuarial losses	-16,264	-14,881	-8,072
Total reclassifications	-31,674	-33,445	20,383
Total gain (loss) during the period	-113,755	-74,935	97,896
Ending balance	41,638	155,393	230,328
Beginning Balance	-240,264	-356,441	-205,220
Unrealized holding gains(losses), net	-31,523	82,018	46,790
Foreign currency translation adjustment	381	519	-803
Current year pension gains (losses)	158,225	-18,118	-165,398
Total other comprehensive income before reclassifications	127,083	64,419	-119,411
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	2,604	3,760	4,273
OTTI charges recognized in net income	5,953	29,052	46,800
Losses (gains) realized in net income	20,101	-5	-91,176
Amortization of gains on terminated cash flow hedges	'	-112	-281
Amortization of prior service credit	-4,808	-3,972	-3,920
Amortization of actuarial losses	25,172	23,035	12,494
Total reclassifications	49,022	51,758	-31,810
Total gain (loss) during the period	176,105	116,177	-151,221
Ending balance	-64,159	-240,264	-356,441
Investment Securities With OTTI [Member]	'	'	'
Components Of Comprehensive Income [Line Items]	'	'	'
Beginning balance	-91,835	-138,319	-143,139
Unrealized holding gains (losses), net	77,794	-2,998	-68,946
Foreign currency translation adjustment	'	'	'
Current year pension gains (losses)	'	'	'
Total other comprehensive income before reclassifications	77,794	-2,998	-68,946
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	279	1,660	545
OTTI charges recognized in net income	9,800	47,822	77,035
Losses (gains) realized in net income	41,217	'	-3,814
Amortization of gains on terminated cash flow hedges	'	'	'
Amortization of prior service credit	'	'	'
Amortization of actuarial losses	'	'	'
Total reclassifications	51,296	49,482	73,766
Total gain (loss) during the period	129,090	46,484	4,820
Ending balance	37,255	-91,835	-138,319
Investment Securities All Other [Member]	'	'	'
Components Of Comprehensive Income [Line Items]	'	'	'
Beginning balance	152,199	9,757	3,860
Unrealized holding gains (losses), net	-129,628	137,921	145,522
Foreign currency translation adjustment	'	'	'
Current year pension gains (losses)	'	'	'
Total other comprehensive income before reclassifications	-129,628	137,921	145,522
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	4,008	4,530	6,490
OTTI charges recognized in net income	'	'	'
Losses (gains) realized in net income	-8,129	-9	-146,115
Amortization of gains on terminated cash flow hedges	'	'	'
Amortization of prior service credit	'	'	'
Amortization of actuarial losses	'	'	'
Total reclassifications	-4,121	4,521	-139,625
Total gain (loss) during the period	-133,749	142,442	5,897
Ending balance	18,450	152,199	9,757
Defined Benefit Plans [Member]	'	'	'
Components Of Comprehensive Income [Line Items]	'	'	'
Beginning balance	-455,590	-457,145	-198,999
Unrealized holding gains (losses), net	'	'	'
Foreign currency translation adjustment	'	'	'
Current year pension gains (losses)	260,452	-29,823	-272,260
Total other comprehensive income before reclassifications	260,452	-29,823	-272,260
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	'	'	'
OTTI charges recognized in net income	'	'	'
Losses (gains) realized in net income	'	'	'
Amortization of gains on terminated cash flow hedges	'	'	'
Amortization of prior service credit	-7,915	-6,538	-6,452
Amortization of actuarial losses	41,436	37,916	20,566
Total reclassifications	33,521	31,378	14,114
Total gain (loss) during the period	293,973	1,555	-258,146
Ending balance	-161,617	-455,590	-457,145
Beginning Balance	-276,771	-277,716	-120,892
Total gain (loss) during the period	178,589	945	-156,824
Ending balance	-98,182	-276,771	-277,716
Other [Member]	'	'	'
Components Of Comprehensive Income [Line Items]	'	'	'
Beginning balance	-431	-1,062	626
Unrealized holding gains (losses), net	'	'	'
Foreign currency translation adjustment	546	809	-1,240
Current year pension gains (losses)	'	'	'
Total other comprehensive income before reclassifications	546	809	-1,240
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	'	'	'
OTTI charges recognized in net income	'	'	'
Losses (gains) realized in net income	'	'	'
Amortization of gains on terminated cash flow hedges	'	-178	-448
Amortization of prior service credit	'	'	'
Amortization of actuarial losses	'	'	'
Total reclassifications	'	-178	-448
Total gain (loss) during the period	546	631	-1,688
Ending balance	$115	($431)	($1,062)

Comprehensive_Income_Accumulat

Comprehensive Income - Accumulated Other Comprehensive Income (Loss), Net Consisted of Unrealized Gains (Losses) (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning Balance	($240,264)	($356,441)	($205,220)
Net gain (loss) during period	176,105	116,177	-151,221
Ending balance	-64,159	-240,264	-356,441
Cash Flow Hedges [Member]	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning Balance	'	112	393
Net gain (loss) during period	'	-112	-281
Ending balance	'	'	112
Foreign Currency Translation Adjustment [Member]	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning Balance	-284	-803	'
Net gain (loss) during period	381	519	-803
Ending balance	97	-284	-803
Defined Benefit Plans [Member]	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning Balance	-276,771	-277,716	-120,892
Net gain (loss) during period	178,589	945	-156,824
Ending balance	-98,182	-276,771	-277,716
Investment Securities [Member] | Investment Securities With OTTI [Member]	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning Balance	-55,790	-84,029	-87,053
Net gain (loss) during period	78,422	28,239	3,024
Ending balance	22,632	-55,790	-84,029
Investment Securities [Member] | Investment Securities All Other [Member]	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning Balance	92,581	5,995	2,332
Net gain (loss) during period	-81,287	86,586	3,663
Ending balance	$11,294	$92,581	$5,995

Other_income_and_other_expense2

Other income and other expense - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2013
Other Income And Expenses [Abstract]	'
Minimum percentage of interest income and other income for separate disclosure	1.00%

Other_income_and_other_expense3

Other income and other expense - Other Income and Other Expense (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other income:	'	'	'
Bank owned life insurance	$56,120	$51,199	$50,776
Credit-related fee income	72,271	68,596	73,886
Letter of credit fees	59,889	58,496	56,247
Non-taxable gain from business combination	'	'	64,930
Gains from loan securitization transactions	63,066	'	'
Other expense:	'	'	'
Professional services	335,794	248,544	222,122
Amortization of capitalized servicing rights	65,354	59,555	55,859
Advertising and promotion	56,597	52,388	58,312
Write-down of investment in Bayview Lending Group LLC ("BLG")	'	'	$79,012

International_activities_Addit

International activities - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
International Activities [Abstract]	'	'	'
Revenues from trust-related services	$26,000,000	$24,000,000	$15,000,000
Net assets identified with international activities	226,000,000	179,000,000	'
Loans to foreign borrowers	192,000,000	149,000,000	'
Deposits at Cayman Islands office	$322,746,000	$1,044,519,000	'

Recovered_Sheet7

Derivative Financial Instruments - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Derivative [Line Items]	'	'	'
Increase in net interest income due to interest rate swap agreements	$41,000,000	$36,000,000	$38,000,000
Notional value of interest rate swap agreement impacting net interest income, contract entered into for interest rate risk management purposes	1,200,000,000	900,000,000	900,000,000
Notional value of foreign currency and other option and futures contracts entered into for trading purposes	1,400,000,000	869,000,000	'
Net unrealized pre-tax gains related to hedged loans held for sale, commitments to originate loans for sale and commitments to sell loans	23,000,000	89,000,000	'
Aggregate fair value of derivative financial instruments in a liability position	194,000,000	374,000,000	'
Net liability positions with counterparties	107,000,000	281,000,000	'
Post collateral requirements relating to positions	95,000,000	266,000,000	'
Fair value of additional collateral to be posted for derivative financial instruments	11,000,000	'	'
Aggregate fair value of derivative financial instruments in asset position	183,000,000	164,000,000	'
Net asset positions with counterparties	95,000,000	71,000,000	'
Counterparties posted collateral relating to positions	93,000,000	69,000,000	'
Credit Risk Derivative [Member]	'	'	'
Derivative [Line Items]	'	'	'
Aggregate fair value of derivative financial instruments in a net liability position	34,000,000	'	'
Fair value of collateral already posted for derivative financial instruments	23,000,000	'	'
Interest rate contracts [Member]	'	'	'
Derivative [Line Items]	'	'	'
Notional value of interest rate contracts entered into trading purposes	$17,400,000,000	$15,500,000,000	'

Recovered_Sheet8

Derivative Financial Instruments - Information about Interest Rate Swap Agreements (Detail) (Fixed rate long-term borrowings [Member], Fair Value Hedges [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fixed rate long-term borrowings [Member] | Fair Value Hedges [Member]	'	'
Derivative [Line Items]	'	'
Notional Amount	$1,400,000	$900,000
Average Maturity (in years)	'3 years 8 months 12 days	'4 years 4 months 24 days
Weighted-Average Rate, Fixed	4.42%	6.07%
Weighted-Average Rate, Variable	1.20%	1.85%
Estimated Fair Value Gain	$102,875	$143,179

Derivative_Financial_Instrumen2

Derivative Financial Instruments - Notional Amount of Interest Rate Swap Agreements Outstanding Maturity (Detail) (Interest rate swap agreements [Member], USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Interest rate swap agreements [Member]	'
Derivative Instruments and Hedging Activities Disclosures [Line Items]	'
2016	$500,000
2017	400,000
2018	500,000
Total	$1,400,000

Derivative_Financial_Instrumen3

Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Balance Sheet (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Derivatives, Fair Value [Line Items]	'	'
Asset derivatives, Fair value	$414,263	$603,019
Liability derivatives, Fair value	254,189	384,866
Derivatives designated and qualifying as hedging instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Asset derivatives, Fair value	109,832	144,293
Liability derivatives, Fair value	487	3,825
Derivatives not designated and qualifying as hedging instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Asset derivatives, Fair value	304,431	458,726
Liability derivatives, Fair value	253,702	381,041
Interest rate swap agreements [Member] | Derivatives designated and qualifying as hedging instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Asset derivatives, Fair value	102,875	143,179
Liability derivatives, Fair value	'	'
Commitments to sell real estate loans [Member] | Derivatives designated and qualifying as hedging instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Asset derivatives, Fair value	6,957	1,114
Liability derivatives, Fair value	487	3,825
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	6,120	1,982
Liability derivatives, Fair value	230	6,570
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	7,616	48,056
Liability derivatives, Fair value	3,675	197
Interest rate contracts [Member] | Derivatives not designated and qualifying as hedging instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Asset derivatives, Fair value	274,864	399,963
Liability derivatives, Fair value	234,455	365,616
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	15,831	8,725
Liability derivatives, Fair value	$15,342	$8,658

Derivative_Financial_Instrumen4

Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Statement of Income (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'
Derivatives not designated as hedging instruments, Derivatives	$6,455	$4,034	$3,481
Interest rate contracts [Member]	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'
Derivatives not designated as hedging instruments, Derivatives	9,824	8,004	6,130
Foreign exchange and other option and futures contracts [Member]	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'
Derivatives not designated as hedging instruments, Derivatives	-3,369	-3,970	-2,649
Interest rate swap agreements [Member] | Fixed rate long-term borrowings [Member]	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'
Derivatives in fair value hedging relationships, Derivatives	-40,304	-4,123	50,665
Derivatives in fair value hedging relationships, Hedged item	$38,986	$3,724	($47,916)

Recovered_Sheet9

Variable Interest Entities and Asset Securitizations - Additional Information (Detail) (USD $)	1 Months Ended	6 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Variable Interest Entity Disclosure [Abstract]	'	'	'	'
Residential mortgage loans securitized with Ginnie Mae	'	$1,300,000,000	$3,000,000,000	'
Residential mortgage loans securitized formerly held in Company's portfolio	'	'	1,300,000,000	'
Recognized gain	'	42,382,000	42,382,000	'
Gains of newly originated loans	'	'	28,000,000	'
Automobile loans securitized and sold	1,400,000,000	'	1,400,000,000	'
Recognized gain sale of securities	20,683,000	'	20,683,000	'
Carrying value of loans in the Securitization trusts	'	'	121,000,000	151,000,000
Combined outstanding principal amount of mortgage-backed securities issued by qualified special purpose trust held by unrelated parties	'	'	18,000,000	23,000,000
Other assets for its "investment" in the common securities recognized by the company of various trusts	'	'	34,000,000	34,000,000
Total assets of real estate partnerships in which the company invested	'	'	1,300,000,000	1,500,000,000
Maximum exposure to loss of investments in real estate partnerships	'	'	236,000,000	270,000,000
Unfunded commitments included in company's maximum exposure to loss of investments in real estate partnerships	'	'	$45,000,000	$71,000,000

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'
Number of independent pricing sources used to value privately issued mortgage-backed securities valued with internal modeling	'	2	'
Privately issued mortgage-backed securities at cost	'	$1,100,000,000	'
Weighted-average reliance on internal model pricing, percentage	33.00%	'	'
Average weighting placed on the values provided by the independent sources, percentage	67.00%	'	'
Weighted average discount margin over LIBOR	8.00%	'	'
Securities issued by financial institutions and other entities backed by trust preferred securities at cost	42,000,000	43,000,000	'
Fair value of securities issued by financial institutions and other entities backed by trust preferred securities	63,000,000	62,000,000	'
Other-than-temporary losses	'	5,000,000	12,000,000
Loans measured at fair value on nonrecurring basis	222,000,000	335,000,000	419,000,000
Change in fair value of nonrecurring fair value measured loans for charge-offs and impairment reserves	58,000,000	67,000,000	158,000,000
Assets taken in foreclosure of defaulted loans measured at fair value on a nonrecurring basis	29,000,000	34,000,000	'
Other-than-temporary impairment charge related to investment in BLG	0	0	79,000,000
Investment in BLG	'	'	20.00%
Carrying value of minority interest investment in Bayview Lending Group LLC	74,000,000	'	115,000,000
Weighted average projected default percentage on Bayview Lending Group mortgage loan collateral	'	'	31.00%
Weighted average loss severity factor on Bayview Lending Group mortgage loan collateral	'	'	75.00%
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	173,000,000	207,000,000	262,000,000
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	$49,000,000	$128,000,000	$157,000,000
Investment fair value percent	'	'	20.00%
Minimum [Member]	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'
Discount margin over LIBOR	5.00%	'	'
Discount rates for fair value estimations	20.00%	'	'
Discount rates	8.00%	'	'
Maximum [Member]	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'
Discount margin over LIBOR	11.00%	'	'
Discount rates for fair value estimations	90.00%	'	'
Discount rates	12.50%	'	'

Fair_Value_Measurements_Assets

Fair Value Measurements - Assets and Liabilities Measured at Estimated Fair Value on Recurring Basis (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading account assets	$376,131	$488,966
Investment securities	4,531,786	4,739,437
Real estate loans held for sale	468,650	1,387,491
Other assets	123,568	194,331
Total assets	5,500,135	6,810,225
Trading account liabilities	249,797	374,274
Other liabilities	4,392	10,592
Total liabilities	254,189	384,866
U.S. Treasury and Federal Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	37,776	39,344
Obligations of States and Political Subdivisions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	10,811	20,901
Government Issued or Guaranteed [Member] | Mortgage-backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	4,165,086	3,371,041
Privately Issued Mortgage-Backed Securities [Member] | Mortgage-backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	1,850	1,023,886
Collateralized Debt Obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	63,083	61,869
Other Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	120,085	111,950
Equity Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	133,095	110,446
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	51,386	56,106
Investment securities	82,450	98,364
Real estate loans held for sale	'	'
Other assets	'	'
Total assets	133,836	154,470
Trading account liabilities	'	'
Other liabilities	'	'
Total liabilities	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury and Federal Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Obligations of States and Political Subdivisions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Government Issued or Guaranteed [Member] | Mortgage-backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Privately Issued Mortgage-Backed Securities [Member] | Mortgage-backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Collateralized Debt Obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	82,450	98,364
Significant Observable Inputs (Level 2) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading account assets	324,745	432,860
Investment securities	4,384,403	3,555,318
Real estate loans held for sale	468,650	1,387,491
Other assets	115,952	146,275
Total assets	5,293,750	5,521,944
Trading account liabilities	249,797	374,274
Other liabilities	717	10,395
Total liabilities	250,514	384,669
Significant Observable Inputs (Level 2) [Member] | U.S. Treasury and Federal Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	37,776	39,344
Significant Observable Inputs (Level 2) [Member] | Obligations of States and Political Subdivisions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	10,811	20,901
Significant Observable Inputs (Level 2) [Member] | Government Issued or Guaranteed [Member] | Mortgage-backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	4,165,086	3,371,041
Significant Observable Inputs (Level 2) [Member] | Privately Issued Mortgage-Backed Securities [Member] | Mortgage-backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	'	'
Significant Observable Inputs (Level 2) [Member] | Collateralized Debt Obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	'	'
Significant Observable Inputs (Level 2) [Member] | Other Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	120,085	111,950
Significant Observable Inputs (Level 2) [Member] | Equity Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	50,645	12,082
Significant Unobservable Inputs (Level 3) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading account assets	'	'
Investment securities	64,933	1,085,755
Real estate loans held for sale	'	'
Other assets	7,616	48,056
Total assets	72,549	1,133,811
Trading account liabilities	'	'
Other liabilities	3,675	197
Total liabilities	3,675	197
Significant Unobservable Inputs (Level 3) [Member] | U.S. Treasury and Federal Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	'	'
Significant Unobservable Inputs (Level 3) [Member] | Obligations of States and Political Subdivisions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	'	'
Significant Unobservable Inputs (Level 3) [Member] | Government Issued or Guaranteed [Member] | Mortgage-backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	'	'
Significant Unobservable Inputs (Level 3) [Member] | Privately Issued Mortgage-Backed Securities [Member] | Mortgage-backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	1,850	1,023,886
Significant Unobservable Inputs (Level 3) [Member] | Collateralized Debt Obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	63,083	61,869
Significant Unobservable Inputs (Level 3) [Member] | Other Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	'	'
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	'	'

Fair_Value_Measurements_Change

Fair Value Measurements - Changes in Level 3 Assets and Liabilities Measured at Estimated Fair Value on Recurring Basis (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other Assets and Other Liabilities [Member]	'	'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'	'
Beginning Balance	$47,859	$6,923	$2,244
Total gains (losses) realized/unrealized:	'	'	'
Included in earnings	97,845	212,281	67,163
Included in other comprehensive income	'	'	'
Purchases	'	'	'
Sales	'	'	'
Settlements	'	'	'
Transfers in and/or out of Level 3	-141,763	-171,345	-62,484
Ending Balance	3,941	47,859	6,923
Changes in unrealized gains (losses) included in earnings related to assets still held at end of period	3,431	47,859	6,902
Mortgage-backed Securities, Privately issued [Member]	'	'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'	'
Beginning Balance	1,023,886	1,151,285	1,457,968
Total gains (losses) realized/unrealized:	'	'	'
Included in earnings	-56,102	-42,467	-64,919
Included in other comprehensive income	116,359	114,592	6,816
Purchases	'	'	'
Sales	-978,608	'	'
Settlements	-103,685	-199,524	-248,580
Transfers in and/or out of Level 3	'	'	'
Ending Balance	1,850	1,023,886	1,151,285
Changes in unrealized gains (losses) included in earnings related to assets still held at end of period	'	-42,467	-64,919
Collateralized Debt Obligations [Member]	'	'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'	'
Beginning Balance	61,869	52,500	110,756
Total gains (losses) realized/unrealized:	'	'	'
Included in earnings	'	'	19,231
Included in other comprehensive income	4,508	12,214	-272
Purchases	'	'	50,790
Sales	'	'	-124,874
Settlements	-3,294	-2,845	-3,131
Transfers in and/or out of Level 3	'	'	'
Ending Balance	63,083	61,869	52,500
Changes in unrealized gains (losses) included in earnings related to assets still held at end of period	'	'	'

Fair_Value_Measurements_Quanti

Fair Value Measurements - Quantitative Information Related to Significant Unobservable Inputs (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Mortgage-backed Securities, Privately issued [Member]	'	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'
Investments	$1,850	$1,023,886	$1,151,285	$1,457,968
Valuation technique	'Two independent pricing quotes	'Discounted cash flow	'	'
Unobservable inputs/ assumptions	'-	'Probability of default Loss severity	'	'
Mortgage-backed Securities, Privately issued [Member] | Weighted Average [Member]	'	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'
Probability of default	'	19.00%	'	'
Loss severity	'	51.00%	'	'
Mortgage-backed Securities, Privately issued [Member] | Minimum [Member]	'	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'
Probability of default	'	1.00%	'	'
Loss severity	'	32.00%	'	'
Mortgage-backed Securities, Privately issued [Member] | Maximum [Member]	'	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'
Probability of default	'	40.00%	'	'
Loss severity	'	82.00%	'	'
Collateralized Debt Obligations [Member]	'	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'
Investments	63,083	61,869	52,500	110,756
Valuation technique	'Discounted cash flow	'Discounted cash flow	'	'
Unobservable inputs/ assumptions	'Probability of default Loss severity	'Probability of default Loss severity	'	'
Collateralized Debt Obligations [Member] | Weighted Average [Member]	'	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'
Probability of default	39.00%	47.00%	'	'
Collateralized Debt Obligations [Member] | Minimum [Member]	'	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'
Probability of default	17.00%	22.00%	'	'
Collateralized Debt Obligations [Member] | Maximum [Member]	'	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'
Probability of default	55.00%	69.00%	'	'
Loss severity	100.00%	100.00%	'	'
Other Assets and Other Liabilities [Member]	'	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'
Investments	$3,941	$47,859	$6,923	$2,244
Valuation technique	'Discounted cash flow	'Discounted cash flow	'	'
Unobservable inputs/ assumptions	'Commitment expirations	'Commitment expirations	'	'
Other Assets and Other Liabilities [Member] | Weighted Average [Member]	'	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'
Commitment expirations weighted-average	20.00%	20.00%	'	'
Other Assets and Other Liabilities [Member] | Minimum [Member]	'	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'
Commitment expirations	0.00%	0.00%	'	'
Other Assets and Other Liabilities [Member] | Maximum [Member]	'	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'
Commitment expirations	90.00%	69.00%	'	'

Fair_Value_Measurements_Carryi

Fair Value Measurements - Carrying Amounts and Estimated Fair Value for Financial Instrument Assets (Liabilities) (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
In Thousands, unless otherwise specified
Financial assets:	'	'	'	'
Cash and cash equivalents	$1,672,934	$1,986,615	$1,452,397	$933,755
Interest-bearing deposits at banks	1,651,138	129,945	'	'
Trading account assets	376,131	488,966	'	'
Loans and leases:	'	'	'	'
Residential real estate loans	8,911,554	11,161,323	'	'
Consumer loans	10,280,527	11,550,274	'	'
Allowance for credit losses	-916,676	-925,860	-908,290	-902,941
Loans and leases, net	63,156,483	65,645,097	'	'
Financial liabilities:	'	'	'	'
Noninterest-bearing deposits	-24,661,007	-24,240,802	'	'
Time deposits	-3,523,838	-4,562,366	'	'
Deposits at Cayman Islands office	-322,746	-1,044,519	'	'
Long-term borrowings	-5,108,870	-4,607,758	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'	'	'
Financial assets:	'	'	'	'
Cash and cash equivalents	1,596,877	1,895,423	'	'
Interest-bearing deposits at banks	'	'	'	'
Trading account assets	51,386	56,106	'	'
Investment securities	82,450	98,364	'	'
Loans and leases:	'	'	'	'
Commercial loans and leases	'	'	'	'
Commercial real estate loans	'	'	'	'
Residential real estate loans	'	'	'	'
Consumer loans	'	'	'	'
Allowance for credit losses	'	'	'	'
Loans and leases, net	'	'	'	'
Accrued interest receivable	'	'	'	'
Financial liabilities:	'	'	'	'
Noninterest-bearing deposits	'	'	'	'
Savings deposits and NOW accounts	'	'	'	'
Time deposits	'	'	'	'
Deposits at Cayman Islands office	'	'	'	'
Short-term borrowings	'	'	'	'
Long-term borrowings	'	'	'	'
Accrued interest payable	'	'	'	'
Trading account liabilities	'	'	'	'
Other financial instruments:	'	'	'	'
Commitments to originate real estate loans for sale	'	'	'	'
Commitments to sell real estate loans	'	'	'	'
Other credit-related commitments	'	'	'	'
Interest rate swap agreements used for interest rate risk management	'	'	'	'
Significant Observable Inputs (Level 2) [Member]	'	'	'	'
Financial assets:	'	'	'	'
Cash and cash equivalents	76,057	91,192	'	'
Interest-bearing deposits at banks	1,651,138	129,945	'	'
Trading account assets	324,745	432,860	'	'
Investment securities	8,384,106	4,687,211	'	'
Loans and leases:	'	'	'	'
Commercial loans and leases	'	'	'	'
Commercial real estate loans	67,505	199,997	'	'
Residential real estate loans	5,432,207	8,100,915	'	'
Consumer loans	'	'	'	'
Allowance for credit losses	'	'	'	'
Loans and leases, net	5,499,712	8,300,912	'	'
Accrued interest receivable	222,558	222,897	'	'
Financial liabilities:	'	'	'	'
Noninterest-bearing deposits	-24,661,007	-24,240,802	'	'
Savings deposits and NOW accounts	-38,611,021	-35,763,566	'	'
Time deposits	-3,542,789	-4,584,384	'	'
Deposits at Cayman Islands office	-322,746	-1,044,519	'	'
Short-term borrowings	-260,455	-1,074,482	'	'
Long-term borrowings	-5,244,902	-4,768,408	'	'
Accrued interest payable	-43,419	-54,281	'	'
Trading account liabilities	-249,797	-374,274	'	'
Other financial instruments:	'	'	'	'
Commitments to originate real estate loans for sale	'	'	'	'
Commitments to sell real estate loans	12,360	-7,299	'	'
Other credit-related commitments	'	'	'	'
Interest rate swap agreements used for interest rate risk management	102,875	143,179	'	'
Significant Unobservable Inputs (Level 3) [Member]	'	'	'	'
Financial assets:	'	'	'	'
Cash and cash equivalents	'	'	'	'
Interest-bearing deposits at banks	'	'	'	'
Trading account assets	'	'	'	'
Investment securities	223,938	1,233,393	'	'
Loans and leases:	'	'	'	'
Commercial loans and leases	18,457,288	17,554,562	'	'
Commercial real estate loans	25,950,690	25,658,485	'	'
Residential real estate loans	3,435,665	3,280,404	'	'
Consumer loans	10,201,087	11,504,799	'	'
Allowance for credit losses	'	'	'	'
Loans and leases, net	58,044,730	57,998,250	'	'
Accrued interest receivable	'	'	'	'
Financial liabilities:	'	'	'	'
Noninterest-bearing deposits	'	'	'	'
Savings deposits and NOW accounts	'	'	'	'
Time deposits	'	'	'	'
Deposits at Cayman Islands office	'	'	'	'
Short-term borrowings	'	'	'	'
Long-term borrowings	'	'	'	'
Accrued interest payable	'	'	'	'
Trading account liabilities	'	'	'	'
Other financial instruments:	'	'	'	'
Commitments to originate real estate loans for sale	3,941	47,859	'	'
Commitments to sell real estate loans	'	'	'	'
Other credit-related commitments	-118,886	-119,464	'	'
Interest rate swap agreements used for interest rate risk management	'	'	'	'
Carrying Amount [Member]	'	'	'	'
Financial assets:	'	'	'	'
Cash and cash equivalents	1,672,934	1,986,615	'	'
Interest-bearing deposits at banks	1,651,138	129,945	'	'
Trading account assets	376,131	488,966	'	'
Investment securities	8,796,497	6,074,361	'	'
Loans and leases:	'	'	'	'
Commercial loans and leases	18,705,216	17,776,953	'	'
Commercial real estate loans	26,148,208	25,993,790	'	'
Residential real estate loans	8,928,221	11,240,837	'	'
Consumer loans	10,291,514	11,559,377	'	'
Allowance for credit losses	-916,676	-925,860	'	'
Loans and leases, net	63,156,483	65,645,097	'	'
Accrued interest receivable	222,558	222,897	'	'
Financial liabilities:	'	'	'	'
Noninterest-bearing deposits	-24,661,007	-24,240,802	'	'
Savings deposits and NOW accounts	-38,611,021	-35,763,566	'	'
Time deposits	-3,523,838	-4,562,366	'	'
Deposits at Cayman Islands office	-322,746	-1,044,519	'	'
Short-term borrowings	-260,455	-1,074,482	'	'
Long-term borrowings	-5,108,870	-4,607,758	'	'
Accrued interest payable	-43,419	-54,281	'	'
Trading account liabilities	-249,797	-374,274	'	'
Other financial instruments:	'	'	'	'
Commitments to originate real estate loans for sale	3,941	47,859	'	'
Commitments to sell real estate loans	12,360	-7,299	'	'
Other credit-related commitments	-118,886	-119,464	'	'
Interest rate swap agreements used for interest rate risk management	102,875	143,179	'	'
Estimate Fair Value [Member]	'	'	'	'
Financial assets:	'	'	'	'
Cash and cash equivalents	1,672,934	1,986,615	'	'
Interest-bearing deposits at banks	1,651,138	129,945	'	'
Trading account assets	376,131	488,966	'	'
Investment securities	8,690,494	6,018,968	'	'
Loans and leases:	'	'	'	'
Commercial loans and leases	18,457,288	17,554,562	'	'
Commercial real estate loans	26,018,195	25,858,482	'	'
Residential real estate loans	8,867,872	11,381,319	'	'
Consumer loans	10,201,087	11,504,799	'	'
Allowance for credit losses	'	'	'	'
Loans and leases, net	63,544,442	66,299,162	'	'
Accrued interest receivable	222,558	222,897	'	'
Financial liabilities:	'	'	'	'
Noninterest-bearing deposits	-24,661,007	-24,240,802	'	'
Savings deposits and NOW accounts	-38,611,021	-35,763,566	'	'
Time deposits	-3,542,789	-4,584,384	'	'
Deposits at Cayman Islands office	-322,746	-1,044,519	'	'
Short-term borrowings	-260,455	-1,074,482	'	'
Long-term borrowings	-5,244,902	-4,768,408	'	'
Accrued interest payable	-43,419	-54,281	'	'
Trading account liabilities	-249,797	-374,274	'	'
Other financial instruments:	'	'	'	'
Commitments to originate real estate loans for sale	3,941	47,859	'	'
Commitments to sell real estate loans	12,360	-7,299	'	'
Other credit-related commitments	-118,886	-119,464	'	'
Interest rate swap agreements used for interest rate risk management	$102,875	$143,179	'	'

Recovered_Sheet10

Commitments and Contingencies - Company's Significant Commitments (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Commitments to extend credit	'	'
Home equity lines of credit	$6,218,823	$6,282,615
Commercial real estate loans to be sold	62,386	139,929
Other commercial real estate and construction	3,919,545	3,819,342
Residential real estate loans to be sold	469,869	1,550,441
Other residential real estate	384,617	445,268
Commercial and other	10,419,545	10,070,711
Standby letters of credit	3,600,528	4,025,329
Commercial letters of credit	53,284	53,201
Financial guarantees and indemnification contracts	2,457,633	2,120,361
Commitments to sell real estate loans	$854,656	$2,625,408

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Significant Commitments [Line Items]	'	'
Maximum credit risk for recourse associated with loans sold under Federal National Mortgage Association Delegated Underwriting and Servicing program	$2,300,000,000	$2,000,000,000
Period of noncancelable operating lease in years	'25 years	'
Outstanding loan principal balances reinsured	19,000,000	'
Assets of subsidiaries providing reinsurance to satisfy claims	36,000,000	'
Range of reasonably possible losses, minimum	0	'
Range of reasonably possible losses, maximum	50,000,000	'
2014 - 2017 [Member]	'	'
Significant Commitments [Line Items]	'	'
Naming rights of football stadium per year	$6,000,000	'

Commitments_and_Contingencies_2

Commitments and Contingencies - Minimum Lease Payments Under Noncancellable Operating Leases (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Commitments And Contingencies Disclosure [Abstract]	'
2014	$85,923
2015	80,237
2016	66,265
2017	52,793
2018	43,593
Later years	135,156
Total	$463,967

Segment_Information_Informatio

Segment Information - Information about Company's Segments (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]	'	'	'
Net interest income	$2,673,229,000	$2,598,516,000	$2,389,756,000
Noninterest income	1,865,205,000	1,667,270,000	1,582,912,000
Total income	4,538,434,000	4,265,786,000	3,972,668,000
Provision for credit losses	185,000,000	204,000,000	270,000,000
Amortization of core deposit and other intangible assets	46,912,000	60,631,000	61,617,000
Depreciation and other amortization	156,823,000	143,930,000	136,163,000
Other noninterest expense	2,432,150,000	2,304,699,000	2,280,288,000
Income (loss) before taxes	1,717,549,000	1,552,526,000	1,224,600,000
Income tax expense (benefit)	579,069,000	523,028,000	365,121,000
Net income (loss)	1,138,480,000	1,029,498,000	859,479,000
Capital expenditures	130,000,000	92,000,000	70,000,000
Reporting Segment [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Average total assets	83,662,000,000	79,983,000,000	73,977,000,000
Residential Mortgage Banking [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Net interest income	98,496,000	78,058,000	63,951,000
Noninterest income	325,474,000	402,211,000	184,249,000
Total income	423,970,000	480,269,000	248,200,000
Provision for credit losses	-11,711,000	17,169,000	36,375,000
Amortization of core deposit and other intangible assets	'	'	'
Depreciation and other amortization	48,716,000	46,902,000	44,349,000
Other noninterest expense	225,794,000	195,604,000	151,945,000
Income (loss) before taxes	161,171,000	220,594,000	15,531,000
Income tax expense (benefit)	61,779,000	85,671,000	2,403,000
Net income (loss)	99,392,000	134,923,000	13,128,000
Capital expenditures	'	1,000,000	'
Residential Mortgage Banking [Member] | Reporting Segment [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Average total assets	2,858,000,000	2,451,000,000	1,958,000,000
Retail Banking [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Net interest income	810,134,000	902,906,000	851,332,000
Noninterest income	373,362,000	349,571,000	366,042,000
Total income	1,183,496,000	1,252,477,000	1,217,374,000
Provision for credit losses	72,502,000	95,345,000	101,679,000
Amortization of core deposit and other intangible assets	'	'	'
Depreciation and other amortization	34,599,000	32,734,000	33,713,000
Other noninterest expense	768,644,000	751,916,000	744,905,000
Income (loss) before taxes	307,751,000	372,482,000	337,077,000
Income tax expense (benefit)	125,350,000	151,616,000	137,161,000
Net income (loss)	182,401,000	220,866,000	199,916,000
Capital expenditures	40,000,000	15,000,000	25,000,000
Retail Banking [Member] | Reporting Segment [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Average total assets	10,997,000,000	11,705,000,000	11,940,000,000
All Other [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Net interest income	43,904,000	-80,894,000	-46,458,000
Noninterest income	670,889,000	501,390,000	489,863,000
Total income	714,793,000	420,496,000	443,405,000
Provision for credit losses	-3,094,000	4,917,000	-61,349,000
Amortization of core deposit and other intangible assets	46,912,000	60,631,000	61,617,000
Depreciation and other amortization	57,120,000	50,536,000	45,495,000
Other noninterest expense	690,150,000	693,046,000	771,534,000
Income (loss) before taxes	-76,295,000	-388,634,000	-373,892,000
Income tax expense (benefit)	-78,841,000	-207,887,000	-228,970,000
Net income (loss)	2,546,000	-180,747,000	-144,922,000
Capital expenditures	89,000,000	76,000,000	45,000,000
All Other [Member] | Reporting Segment [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Average total assets	9,442,000,000	7,952,000,000	8,042,000,000
Business Banking [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Net interest income	325,521,000	347,067,000	334,811,000
Noninterest income	102,945,000	103,283,000	95,429,000
Total income	428,466,000	450,350,000	430,240,000
Provision for credit losses	26,450,000	22,245,000	45,689,000
Amortization of core deposit and other intangible assets	'	'	'
Depreciation and other amortization	198,000	122,000	140,000
Other noninterest expense	214,043,000	179,428,000	177,172,000
Income (loss) before taxes	187,775,000	248,555,000	207,239,000
Income tax expense (benefit)	76,735,000	101,484,000	84,532,000
Net income (loss)	111,040,000	147,071,000	122,707,000
Average total assets	5,080,000,000	4,909,000,000	5,192,000,000
Capital expenditures	1,000,000	'	'
Commercial Banking [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Net interest income	758,231,000	753,678,000	655,407,000
Noninterest income	263,766,000	253,808,000	249,150,000
Total income	1,021,997,000	1,007,486,000	904,557,000
Provision for credit losses	76,818,000	15,781,000	29,823,000
Amortization of core deposit and other intangible assets	'	'	'
Depreciation and other amortization	564,000	567,000	553,000
Other noninterest expense	288,842,000	262,820,000	248,428,000
Income (loss) before taxes	655,773,000	728,318,000	625,753,000
Income tax expense (benefit)	264,433,000	296,894,000	256,311,000
Net income (loss)	391,340,000	431,424,000	369,442,000
Average total assets	21,655,000,000	19,946,000,000	17,650,000,000
Capital expenditures	'	'	'
Commercial Real Estate [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Net interest income	570,786,000	531,398,000	467,683,000
Noninterest income	130,895,000	133,120,000	99,409,000
Total income	701,681,000	664,518,000	567,092,000
Provision for credit losses	7,365,000	4,238,000	58,474,000
Amortization of core deposit and other intangible assets	'	'	'
Depreciation and other amortization	14,296,000	11,004,000	9,054,000
Other noninterest expense	214,246,000	190,879,000	154,042,000
Income (loss) before taxes	465,774,000	458,397,000	345,522,000
Income tax expense (benefit)	143,981,000	149,321,000	105,709,000
Net income (loss)	321,793,000	309,076,000	239,813,000
Average total assets	17,150,000,000	16,437,000,000	15,025,000,000
Capital expenditures	'	'	'
Discretionary Portfolio [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Net interest income	66,157,000	66,303,000	63,030,000
Noninterest income	-2,126,000	-76,113,000	98,770,000
Total income	64,031,000	-9,810,000	161,800,000
Provision for credit losses	16,670,000	44,305,000	59,309,000
Amortization of core deposit and other intangible assets	'	'	'
Depreciation and other amortization	1,330,000	2,065,000	2,859,000
Other noninterest expense	30,431,000	31,006,000	32,262,000
Income (loss) before taxes	15,600,000	-87,186,000	67,370,000
Income tax expense (benefit)	-14,368,000	-54,071,000	7,975,000
Net income (loss)	29,968,000	-33,115,000	59,395,000
Average total assets	16,480,000,000	16,583,000,000	14,170,000,000
Capital expenditures	'	'	'

Segment_Information_Informatio1

Segment Information - Information about Company's Segments (Parenthetical) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting [Abstract]	'	'	'
Taxable-equivalent adjustment	$24,971,000	$26,391,000	$25,876,000

Segment_Information_Intersegme

Segment Information - Intersegment Activity Eliminated in Arriving at Consolidated Totals was Included in "All Other" Category (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]	'	'	'
Revenues	($4,538,434)	($4,265,786)	($3,972,668)
Income taxes (benefit)	-579,069	-523,028	-365,121
Net income (loss)	-1,138,480	-1,029,498	-859,479
Intersegment activity eliminated in consolidated totals [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Revenues	-50,128	-71,452	-64,239
Expenses	-16,235	-17,313	-14,146
Income taxes (benefit)	-13,791	-22,029	-20,383
Net income (loss)	($20,102)	($32,110)	($29,710)

Segment_information_Additional

Segment information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2013
Segment Reporting [Abstract]	'
Percent of maximum revenue from single customer on total revenues	10.00%

Regulatory_Matters_Additional_

Regulatory Matters - Additional Information (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]	'	'
Funds available for payment of dividends to M&T from banking subsidiaries	$1,110,000,000	'
Required subsidiary noninterest-earning reserves against certain deposit liabilities	595,593,000	604,789,000
Minimum "Tier 1 capital" ratio required for capital adequacy	4.00%	'
Minimum "Total capital" ratio required for capital adequacy	8.00%	'
Minimum "Leverage" ratio required for capital adequacy	3.00%	'
Minimum "Tier 1" capital" ratio to be considered well capitalized	6.00%	'
Minimum "Total capital" ratio to be considered well capitalized	10.00%	'
Minimum "Leverage" ratio to be considered well capitalized	5.00%	'
Minimum [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_Capital_Rat

Regulatory Matters - Capital Ratios and Amounts of Company and its Banking Subsidiaries (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
M&T (Consolidated) [Member]	'	'
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]	'	'
Amount	$8,792,035	$7,810,196
Ratio	12.00%	10.22%
Minimum required amount	2,930,925	3,057,093
Amount	11,045,589	10,230,302
Ratio	15.07%	13.39%
Minimum required amount	5,861,849	6,114,186
Amount	8,792,035	7,810,196
Ratio	10.78%	10.07%
Minimum required amount	2,446,476	2,327,122
M&T Bank [Member]	'	'
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]	'	'
Amount	7,341,506	6,767,774
Ratio	10.08%	8.92%
Minimum required amount	2,914,246	3,034,184
Amount	9,445,770	8,981,931
Ratio	12.96%	11.84%
Minimum required amount	5,828,491	6,068,367
Amount	7,341,506	6,767,774
Ratio	9.09%	8.84%
Minimum required amount	2,422,096	2,297,902
Wilmington Trust, N.A. [Member]	'	'
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]	'	'
Amount	420,330	405,469
Ratio	73.79%	61.02%
Minimum required amount	22,786	26,580
Amount	424,975	410,873
Ratio	74.60%	61.83%
Minimum required amount	45,573	53,160
Amount	420,330	405,469
Ratio	19.80%	21.62%
Minimum required amount	$63,678	$56,275

Relationship_with_Bayview_Lend1

Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P. - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule Of Results Related To Equity Accounted Investees [Line Items]	'	'	'
Minority interest in Bayview Lending Group LLC	20.00%	'	'
Carrying value of minority interest investment in Bayview Lending Group LLC	$74,000,000	'	$115,000,000
Total other-than-temporary impairment ("OTTI") losses	0	0	79,000,000
Outstanding principal balances of mortgage servicing rights obtained from Bayview Financial	5,500,000,000	6,500,000,000	'
Revenues from servicing rights	31,000,000	35,000,000	41,000,000
Collateralized mortgage obligations in available-for-sale investment securities portfolio securitized by Bayview Financial	2,000,000	11,000,000	'
Investment securities in held-to-maturity portfolio securitized by Bayview Financial	220,000,000	242,000,000	'
Bayview Financial [Member]	'	'	'
Schedule Of Results Related To Equity Accounted Investees [Line Items]	'	'	'
Outstanding principal balances of residential mortgage loans from Bayview Financial	45,600,000,000	11,400,000,000	'
Revenues earned for sub-servicing loans	$33,000,000	$10,000,000	$477,000

Recovered_Sheet11

Parent Company Financial Statements - Condensed Balance Sheet (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
In Thousands, unless otherwise specified
Investments in consolidated subsidiaries	'	'	'	'
Investment in Bayview Lending Group LLC	$74,000	'	$115,000	'
Other assets	5,282,212	4,448,779	'	'
Total assets	85,162,391	83,008,803	'	'
Liabilities	'	'	'	'
Accrued expenses and other liabilities	1,368,922	1,512,717	'	'
Long-term borrowings	5,108,870	4,607,758	'	'
Total liabilities	73,856,859	72,806,210	'	'
Shareholders' equity	11,305,532	10,202,593	9,271,209	8,357,695
Total liabilities and shareholders' equity	85,162,391	83,008,803	'	'
Parent Company [Member]	'	'	'	'
Assets	'	'	'	'
Cash in subsidiary bank	10,729	4,774	'	'
Due from consolidated bank subsidiaries	'	'	'	'
Money-market savings	968,274	714,677	'	'
Current income tax receivable	1,914	1,835	'	'
Other	1,894	'	'	'
Total due from consolidated bank subsidiaries	972,082	716,512	'	'
Investments in consolidated subsidiaries	'	'	'	'
Banks and bank holding company	11,364,657	10,495,557	'	'
Other	16,212	16,344	'	'
Investments in unconsolidated subsidiaries (note 19)	33,751	33,916	'	'
Investment in Bayview Lending Group LLC	73,883	93,489	'	'
Other assets	80,098	83,975	'	'
Total assets	12,551,412	11,444,567	'	'
Liabilities	'	'	'	'
Due to consolidated bank subsidiaries	'	213	'	'
Accrued expenses and other liabilities	62,817	60,619	'	'
Long-term borrowings	1,183,063	1,181,142	'	'
Total liabilities	1,245,880	1,241,974	'	'
Shareholders' equity	11,305,532	10,202,593	'	'
Total liabilities and shareholders' equity	$12,551,412	$11,444,567	'	'

Recovered_Sheet12

Parent Company Financial Statements - Condensed Statement of Income (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income	'	'	'
Equity in earnings of Bayview Lending Group LLC	($16,126)	($21,511)	($24,231)
Expense	'	'	'
Interest on long-term borrowings	-199,983	-225,297	-243,866
Other expense (a)	-2,635,885	-2,509,260	-2,478,068
Income tax credits	-579,069	-523,028	-365,121
Equity in undistributed income of subsidiaries	'	'	'
Net income	1,138,480	1,029,498	859,479
Net income per common share	'	'	'
Basic	$8.26	$7.57	$6.37
Diluted	$8.20	$7.54	$6.35
Parent Company [Member]	'	'	'
Income	'	'	'
Dividends from consolidated bank subsidiaries	700,000	700,000	715,000
Equity in earnings of Bayview Lending Group LLC	-16,126	-21,511	-24,231
Other income	9,992	8,755	67,829
Total income	693,866	687,244	758,598
Expense	'	'	'
Interest on long-term borrowings	73,115	82,286	90,959
Other expense (a)	15,994	19,226	87,368
Total expense	89,109	101,512	178,327
Income before income taxes and equity in undistributed income of subsidiaries	604,757	585,732	580,271
Income tax credits	35,986	43,149	50,460
Income before equity in undistributed income of subsidiaries	640,743	628,881	630,731
Equity in undistributed income of subsidiaries	'	'	'
Net income of subsidiaries	1,197,737	1,100,617	943,748
Less: dividends received	-700,000	-700,000	-715,000
Equity in undistributed income of subsidiaries	497,737	400,617	228,748
Net income	$1,138,480	$1,029,498	$859,479
Net income per common share	'	'	'
Basic	$8.26	$7.57	$6.37
Diluted	$8.20	$7.54	$6.35

Parent_Company_Financial_State2

Parent Company Financial Statements - Condensed Statement of Income (Parenthetical) (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Parent Company Only Financial Information [Line Items]	'	'	'
Asset write-downs	$17,918	$63,790	$170,632
Parent Company [Member]	'	'	'
Parent Company Only Financial Information [Line Items]	'	'	'
Asset write-downs	'	'	$79,012

Parent_Company_Financial_State3

Parent Company Financial Statements - Condensed Statement of Cash Flows (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities	'	'	'
Net income	$1,138,480	$1,029,498	$859,479
Adjustments to reconcile net income to net cash provided by operating activities	'	'	'
Provision for deferred income taxes	139,785	131,858	33,924
Asset write-downs	17,918	63,790	170,632
Net cash provided by operating activities	932,324	499,981	1,772,246
Cash flows from investing activities	'	'	'
Other, net	95,706	32,458	144,668
Net cash provided (used) by investing activities	-2,203,578	-4,060,858	368,932
Cash flows from financing activities	'	'	'
Payments on long-term borrowings	-261,212	-2,080,167	-1,809,984
Dividends paid - common	-365,349	-357,717	-350,129
Dividends paid - preferred	-53,450	-53,450	-48,203
Proceeds from issuance of preferred stock	'	'	495,000
Redemption of preferred stock	'	'	-370,000
Other, net	137,967	63,616	31,177
Net cash provided (used) by financing activities	957,573	4,095,095	-1,622,536
Net increase in cash and cash equivalents	-313,681	534,218	518,642
Cash and cash equivalents at beginning of year	1,986,615	1,452,397	933,755
Cash and cash equivalents at end of year	1,672,934	1,986,615	1,452,397
Supplemental disclosure of cash flow information	'	'	'
Interest paid during the year	301,734	371,887	440,810
Income taxes received during the year	389,008	405,598	251,810
Parent Company [Member]	'	'	'
Cash flows from operating activities	'	'	'
Net income	1,138,480	1,029,498	859,479
Adjustments to reconcile net income to net cash provided by operating activities	'	'	'
Equity in undistributed income of subsidiaries	-497,737	-400,617	-228,748
Provision for deferred income taxes	1,535	1,724	-10,349
Asset write-downs	'	'	79,012
Net change in accrued income and expense	31,979	6,798	44,336
Net cash provided by operating activities	674,257	637,403	743,730
Cash flows from investing activities	'	'	'
Proceeds from sales of investment securities	'	411	1,987
Proceeds from maturities of investment securities	'	'	4,400
Investment in subsidiary	-140,000	'	'
Purchase of Wilmington Trust Corporation preferred stock	'	'	-330,000
Other, net	3,295	324	2,833
Net cash provided (used) by investing activities	-136,705	735	-320,780
Cash flows from financing activities	'	'	'
Payments on long-term borrowings	'	-300,000	'
Dividends paid - common	-365,349	-357,717	-350,129
Dividends paid - preferred	-53,450	-53,450	-48,203
Proceeds from issuance of preferred stock	'	'	495,000
Redemption of preferred stock	'	'	-370,000
Other, net	140,799	143,352	16,386
Net cash provided (used) by financing activities	-278,000	-567,815	-256,946
Net increase in cash and cash equivalents	259,552	70,323	166,004
Cash and cash equivalents at beginning of year	719,451	649,128	483,124
Cash and cash equivalents at end of year	979,003	719,451	649,128
Supplemental disclosure of cash flow information	'	'	'
Interest received during the year	2,224	1,970	2,082
Interest paid during the year	71,090	80,090	87,184
Income taxes received during the year	$45,237	$21,878	$57,964