M&T Bank (MTB) 10-Q 12 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 31, 2013
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
Entity Registrant Name	'M&T BANK CORP	'
Entity Central Index Key	'0000036270	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	130,229,189

Consolidated_Balance_Sheet

Consolidated Balance Sheet (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Assets	'	'
Cash and due from banks	$1,941,944	$1,983,615
Interest-bearing deposits at banks	1,925,811	129,945
Federal funds sold	117,809	3,000
Trading account	371,370	488,966
Investment securities (includes pledged securities that can be sold or repledged of $1,707,437 at September 30, 2013; $1,801,842 at December 31, 2012)	'	'
Available for sale (cost: $4,555,109 at September 30, 2013; $4,643,070 at December 31, 2012)	4,692,180	4,739,437
Held to maturity (fair value: $3,277,386 at September 30, 2013; $976,883 at December 31, 2012)	3,319,114	1,032,276
Other (fair value: $298,479 at September 30, 2013; $302,648 at December 31, 2012)	298,479	302,648
Total investment securities	8,309,773	6,074,361
Loans and leases	63,914,772	66,790,186
Unearned discount	-255,730	-219,229
Loans and leases, net of unearned discount	63,659,042	66,570,957
Allowance for credit losses	-916,370	-925,860
Loans and leases, net	62,742,672	65,645,097
Premises and equipment	614,795	594,652
Goodwill	3,524,625	3,524,625
Core deposit and other intangible assets	79,290	115,763
Accrued interest and other assets	4,799,396	4,448,779
Total assets	84,427,485	83,008,803
Liabilities	'	'
Noninterest-bearing deposits	24,150,771	24,240,802
NOW accounts	1,716,511	1,979,619
Savings deposits	36,536,906	33,783,947
Time deposits	3,831,443	4,562,366
Deposits at Cayman Islands office	316,510	1,044,519
Total deposits	66,552,141	65,611,253
Federal funds purchased and agreements to repurchase securities	246,019	1,074,482
Accrued interest and other liabilities	1,491,797	1,512,717
Long-term borrowings	5,121,326	4,607,758
Total liabilities	73,411,283	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 September 30, 2013 and December 31, 2012; Liquidation preference of $10,000 per share: 50,000 shares at September 30, 2013 and December 31, 2012	879,010	872,500
Common stock, $.50 par, 250,000,000 shares authorized, 130,194,232 shares issued at September 30, 2013; 128,176,912 shares issued at December 31, 2012	65,097	64,088
Common stock issuable, 47,048 shares at September 30, 2013; 57,409 shares at December 31, 2012	2,889	3,473
Additional paid-in capital	3,192,981	3,025,520
Retained earnings	7,074,287	6,477,276
Accumulated other comprehensive income (loss), net	-198,062	-240,264
Total shareholders' equity	11,016,202	10,202,593
Total liabilities and shareholders' equity	$84,427,485	$83,008,803

Consolidated_Balance_Sheet_Par

Consolidated Balance Sheet (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Pledged securities that can be sold or repledged	$1,707,437	$1,801,842
Investment securities, available for sale, amortized cost	4,555,109	4,643,070
Investment securities, held to maturity, fair value	3,277,386	976,883
Other, fair value	$298,479	$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	130,194,232	128,176,912
Common stock issuable, shares	47,048	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 $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Interest income	'	'	'	'
Loans and leases, including fees	$683,482	$687,466	$2,071,332	$2,010,529
Deposits at banks	1,650	139	3,372	1,119
Federal funds sold	22	6	84	17
Agreements to resell securities	'	'	10	'
Trading account	169	214	1,048	849
Investment securities	'	'	'	'
Fully taxable	55,746	54,959	141,799	177,647
Exempt from federal taxes	1,617	2,067	5,223	6,171
Total interest income	742,686	744,851	2,222,868	2,196,332
Interest expense	'	'	'	'
NOW accounts	333	327	976	1,034
Savings deposits	13,733	16,510	41,560	51,633
Time deposits	6,129	10,843	21,809	36,706
Deposits at Cayman Islands office	213	336	801	781
Short-term borrowings	58	365	385	1,016
Long-term borrowings	49,112	53,748	150,592	174,068
Total interest expense	69,578	82,129	216,123	265,238
Net interest income	673,108	662,722	2,006,745	1,931,094
Provision for credit losses	48,000	46,000	143,000	155,000
Net interest income after provision for credit losses	625,108	616,722	1,863,745	1,776,094
Other income	'	'	'	'
Mortgage banking revenues	64,731	106,812	249,096	232,518
Service charges on deposit accounts	113,839	114,463	336,505	334,334
Trust income	123,801	115,709	370,132	354,937
Brokerage services income	16,871	14,114	49,840	44,187
Trading account and foreign exchange gains	8,987	8,469	27,138	25,278
Gain on bank investment securities	'	372	56,457	9
Total other-than-temporary impairment ("OTTI") losses	'	-2,134	-1,884	-26,246
Portion of OTTI losses recognized in other comprehensive income (before taxes)	'	-3,538	-7,916	-7,085
Net OTTI losses recognized in earnings	'	-5,672	-9,800	-33,331
Equity in earnings of Bayview Lending Group LLC	-3,881	-5,183	-9,990	-16,570
Other revenues from operations	153,040	96,649	349,581	272,744
Total other income	477,388	445,733	1,418,959	1,214,106
Other expense	'	'	'	'
Salaries and employee benefits	339,332	321,746	1,019,019	991,530
Equipment and net occupancy	66,220	64,248	195,657	194,667
Printing, postage and supplies	9,752	8,272	30,749	31,512
Amortization of core deposit and other intangible assets	10,628	14,085	36,473	46,766
FDIC assessments	14,877	23,801	52,010	77,712
Other costs of operations	217,817	183,875	558,905	540,927
Total other expense	658,626	616,027	1,892,813	1,883,114
Income before taxes	443,870	446,428	1,389,891	1,107,086
Income taxes	149,391	152,966	472,833	373,781
Net income	294,479	293,462	917,058	733,305
Net income available to common shareholders	'	'	'	'
Basic	275,336	273,885	858,944	676,821
Diluted	$275,356	$273,896	$859,000	$676,842
Net income per common share	'	'	'	'
Basic	$2.13	$2.18	$6.69	$5.39
Diluted	$2.11	$2.17	$6.64	$5.37
Cash dividends per common share	$0.70	$0.70	$2.10	$2.10
Average common shares outstanding	'	'	'	'
Basic	129,171	125,818	128,369	125,510
Diluted	130,265	126,292	129,312	125,936

Consolidated_Statement_of_Comp

Consolidated Statement of Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement Of Partners Capital [Abstract]	'	'	'	'
Net income	$294,479	$293,462	$917,058	$733,305
Other comprehensive income, net of tax and reclassification adjustments:	'	'	'	'
Net unrealized gains on investment securities	23,367	42,560	26,724	111,931
Reclassification to income for amortization of gains on terminated cash flow hedges	'	'	'	-112
Foreign currency translation adjustment	1,251	482	205	351
Defined benefit plans liability adjustment	5,091	4,732	15,273	14,196
Total other comprehensive income	29,709	47,774	42,202	126,366
Total comprehensive income	$324,188	$341,236	$959,260	$859,671

Consolidated_Statement_of_Cash

Consolidated Statement of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities	'	'
Net income	$917,058	$733,305
Adjustments to reconcile net income to net cash provided by operating activities	'	'
Provision for credit losses	143,000	155,000
Depreciation and amortization of premises and equipment	66,547	63,344
Amortization of capitalized servicing rights	46,966	44,678
Amortization of core deposit and other intangible assets	36,473	46,766
Provision for deferred income taxes	93,229	108,699
Asset write-downs	16,204	46,505
Net gain on sales of assets	-124,375	-5,070
Net change in accrued interest receivable, payable	-2,819	-10,712
Net change in other accrued income and expense	115,400	-204,876
Net change in loans originated for sale	-808,778	-528,606
Net change in trading account assets and liabilities	4,772	24,743
Net cash provided by operating activities	503,677	473,776
Cash flows from investing activities	'	'
Proceeds from sales of investment securities Available for sale	1,081,747	49,430
Proceeds from sales of investment securities Other	12,994	61,648
Proceeds from maturities of investment securities Available for sale	887,092	1,155,603
Proceeds from maturities of investment securities Held to maturity	216,627	237,933
Purchases of investment securities Available for sale	-41,358	-26,115
Purchases of investment securities Held to maturity	-1,586,425	-282,704
Purchases of investment securities Other	-8,825	-13,563
Net (increase) decrease in loans and leases	905,491	-3,572,339
Net increase in interest-bearing deposits at banks	-1,795,866	-257,034
Other investments, net	-16,947	-7,447
Capital expenditures, net	-85,964	-65,947
Proceeds from sales of real estate acquired in settlement of loans	48,929	80,762
Other, net	-179,629	-86,649
Net cash used by investing activities	-562,134	-2,726,422
Cash flows from financing activities	'	'
Net increase in deposits	604,311	4,624,134
Net decrease in short-term borrowings	-828,463	-189,906
Proceeds from long-term borrowings	799,760	'
Payments on long-term borrowings	-258,937	-1,727,313
Dividends paid - common	-273,518	-267,481
Dividends paid - preferred	-31,494	-31,494
Other, net	119,936	15,237
Net cash provided by financing activities	131,595	2,423,177
Net increase in cash and cash equivalents	73,138	170,531
Cash and cash equivalents at beginning of period	1,986,615	1,452,397
Cash and cash equivalents at end of period	2,059,753	1,622,928
Supplemental disclosure of cash flow information	'	'
Interest received during the period	2,184,128	2,187,027
Interest paid during the period	226,335	280,983
Income taxes paid during the period	331,117	272,502
Supplemental schedule of noncash investing and financing activities	'	'
Available for sale investment securities	1,807,180	'
Securitization of residential mortgage loans allocated to Held to maturity investment securities	917,045	'
Capitalized servicing rights	29,264	'
Real estate acquired in settlement of loans	$35,865	$36,881

Consolidated_Statement_of_Chan

Consolidated Statement of Changes In Shareholders' Equity (USD $)	Total	Preferred stock [Member]	Common stock [Member]	Common stock [Member]	Common stock [Member]	Common stock issuable [Member]	Additional paid-in capital [Member]	Additional paid-in capital [Member]	Additional paid-in capital [Member]	Retained earnings [Member]	Accumulated other comprehensive income (loss), net [Member]
In Thousands, unless otherwise specified				Exercise of Series C stock warrants [Member]	Exercise of Series A stock warrants [Member]			Exercise of Series C stock warrants [Member]	Exercise of Series A stock warrants [Member]
Beginning 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	859,671	'	'	'	'	'	'	'	'	733,305	126,366
Preferred stock cash dividends	-40,088	'	'	'	'	'	'	'	'	-40,088	'
Amortization of preferred stock discount	'	5,831	'	'	'	'	'	'	'	-5,831	'
Stock-based compensation plans:	'	'	'	'	'	'	'	'	'	'	'
Compensation expense, net	37,883	'	228	'	'	'	37,655	'	'	'	'
Exercises of stock options, net	72,484	'	545	'	'	'	71,939	'	'	'	'
Stock purchase plan	10,101	'	75	'	'	'	10,026	'	'	'	'
Directors' stock plan	1,121	'	7	'	'	'	1,114	'	'	'	'
Deferred compensation plans, net, including dividend equivalents	-160	'	5	'	'	-621	576	'	'	-120	'
Other	952	'	'	'	'	'	952	'	'	'	'
Common stock cash dividends - $2.10 per share	-267,646	'	'	'	'	'	'	'	'	-267,646	'
Ending Balance at Sep. 30, 2012	9,945,527	870,416	63,702	'	'	3,451	2,951,248	'	'	6,286,785	-230,075
Beginning 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	959,260	'	'	'	'	'	'	'	'	917,058	42,202
Preferred stock cash dividends	-40,088	'	'	'	'	'	'	'	'	-40,088	'
Amortization of preferred stock discount	'	6,510	'	'	'	'	'	'	'	-6,510	'
Exercise of stock warrants into common stock	'	'	'	93	11	'	'	-93	-11	'	'
Stock-based compensation plans:	'	'	'	'	'	'	'	'	'	'	'
Compensation expense, net	29,973	'	147	'	'	'	29,826	'	'	'	'
Exercises of stock options, net	134,728	'	747	'	'	'	133,981	'	'	'	'
Directors' stock plan	1,229	'	6	'	'	'	1,223	'	'	'	'
Deferred compensation plans, net, including dividend equivalents	-109	'	5	'	'	-584	568	'	'	-98	'
Other	1,967	'	'	'	'	'	1,967	'	'	'	'
Common stock cash dividends - $2.10 per share	-273,351	'	'	'	'	'	'	'	'	-273,351	'
Ending Balance at Sep. 30, 2013	$11,016,202	$879,010	$65,097	'	'	$2,889	$3,192,981	'	'	$7,074,287	($198,062)

Consolidated_Statement_of_Chan1

Consolidated Statement of Changes In Shareholders' Equity (Parenthetical) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Retained earnings [Member]	'	'
Common stock per share dividend amount	$2.10	$2.10
Exercise of Series C stock warrants [Member] | Common stock [Member]	'	'
Number of warrants exercised into shares	407,542	'
Number of shares converted from warrants	186,589	'
Exercise of Series A stock warrants [Member] | Common stock [Member]	'	'
Number of warrants exercised into shares	57,327	'
Number of shares converted from warrants	21,130	'

Significant_Accounting_Policie

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Significant Accounting Policies	'
	1	Significant accounting policies
	The consolidated financial statements of M&T Bank Corporation (“M&T”) and subsidiaries (“the Company”) were compiled in accordance with generally accepted accounting principles (“GAAP”) using the accounting policies set forth in note 1 of Notes to Financial Statements included in the 2012 Annual Report. In the opinion of management, all adjustments necessary for a fair presentation have been made and were all of a normal recurring nature.

Acquisitions

Acquisitions	9 Months Ended
	Sep. 30, 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 would 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 September 30, 2013, total consideration to be paid was valued at approximately $4.8 billion. At September 30, 2013, Hudson City had $39.2 billion of assets, including $24.7 billion of loans and $10.0 billion of investment securities, and $34.5 billion of liabilities, including $22.1 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 April 12, 2013, M&T announced that additional time would be required to obtain a regulatory determination on the applications for the proposed merger with Hudson City. M&T learned that the Federal Reserve Bank of New York (“Federal Reserve Bank”) identified certain concerns with the Company’s procedures, systems and processes related to the Company’s Bank Secrecy Act and anti-money-laundering compliance program. 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. 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 anti-money-laundering laws and regulations and to take certain other steps to enhance their compliance practices. M&T 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 potential 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 from August 27, 2013 to January 31, 2014. There can be no assurances that the merger will be completed by that date.
	In connection with the pending acquisition, the Company incurred merger-related expenses related to preparing for 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 planning for the conversion of systems and/or integration of operations; initial marketing and promotion expenses designed to introduce M&T Bank to its new customers; travel costs; and printing, postage, supplies and other costs of planning for the transaction and commencing operations in new markets and offices.
	A summary of merger-related expenses in 2013 associated with the pending Hudson City acquisition and in 2012 associated with the May 16, 2011 acquisition of Wilmington Trust Corporation (“Wilmington Trust”) included in the consolidated statement of income is presented below. There were no merger-related expenses during the three-month periods ended September 30, 2013 or 2012.
			Nine months ended
			September 30,		September 30,
			2013		2012
			(in thousands)
	Salaries and employee benefits		$	836		4,997
	Equipment and net occupancy			690		15
	Printing, postage and supplies			1,825		—
	Other costs of operations			9,013		4,867
			$	12,364		9,879

Investment_Securities

Investment Securities	9 Months Ended
	Sep. 30, 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)
	September 30, 2013
	Investment securities available for sale:
	U.S. Treasury and federal agencies		$	37,432			480			25	$	37,887
	Obligations of states and political subdivisions			17,614			355			6		17,963
	Mortgage-backed securities:
	Government issued or guaranteed			4,214,895			116,758			1,254		4,330,399
	Privately issued			2,789			1,032			5		3,816
	Collateralized debt obligations			42,686			17,724			1,107		59,303
	Other debt securities			137,661			1,758			20,015		119,404
	Equity securities			102,032			22,221			845		123,408
				4,555,109			160,328			23,257		4,692,180
	Investment securities held to maturity:
	Obligations of states and political subdivisions			170,370			4,279			88		174,561
	Mortgage-backed securities:
	Government issued or guaranteed			2,914,687			39,987			29,015		2,925,659
	Privately issued			224,767			—			56,891		167,876
	Other debt securities			9,290			—			—		9,290
				3,319,114			44,266			85,994		3,277,386
	Other securities			298,479			—			—		298,479
	Total		$	8,172,702			204,594			109,251	$	8,268,045
	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
	Gross realized gains on investment securities were $116 million for the nine-month period ended September 30, 2013. During the second quarter of 2013, the Company sold its holdings of Visa Class B shares for a gain of approximately $90 million and its holdings of MasterCard Class B shares for a gain of $13 million. Gross realized losses on investment securities were $60 million for the nine-month period ended September 30, 2013. During the second quarter of 2013, the Company sold substantially all of its privately issued mortgage-backed securities held in the available-for-sale investment securities portfolio. In total, $1.0 billion of such securities were sold for a net loss of approximately $46 million. Gross realized gains and losses from sales of investment securities were not significant for the three-month period ended September 30, 2013 and for the three-month and nine-month periods ended September 30, 2012.
	The Company recognized $10 million of pre-tax other-than-temporary impairment (“OTTI”) losses during the nine months ended September 30, 2013 and $6 million and $33 million during the three months and nine months ended September 30, 2012, respectively, related to privately issued mortgage-backed securities. There were no other-than-temporary impairment losses during the third quarter of 2013. 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 OTTI losses represented management’s estimate of credit losses inherent in the debt securities considering projected cash flows using assumptions for delinquency rates, loss severities, and other estimates for future collateral performance.
	Changes in credit losses associated with debt securities for which OTTI losses have been recognized in earnings for the three months and nine months ended September 30, 2013 and 2012 follows:
			Three months ended
			September 30
			2013			2012
			(in thousands)
	Beginning balance		$	794			264,197
	Additions for credit losses not previously recognized			—			5,672
	Reductions for realized losses			(626	)		(67,926	)
	Ending balance		$	168			201,943
			Nine months ended
			30-Sep
			2013			2012
			(in thousands)
	Beginning balance		$	197,809			285,399
	Additions for credit losses not previously recognized			9,800			33,331
Reductions for realized losses			(207,441	)		(116,787	)
Ending balance		$	168			201,943
At September 30, 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		$	24,886			24,971
Due after one year through five years			21,212			22,016
Due after five years through ten years			8,282			8,553
Due after ten years			181,013			179,017
			235,393			234,557
Mortgage-backed securities available for sale			4,217,684			4,334,215
		$	4,453,077			4,568,772
Debt securities held to maturity:
Due in one year or less		$	18,617			18,751
Due after one year through five years			65,392			67,400
Due after five years through ten years			86,361			88,410
Due after ten years			9,290			9,290
			179,660			183,851
Mortgage-backed securities held to maturity			3,139,454			3,093,535
		$	3,319,114			3,277,386
A summary of investment securities that as of September 30, 2013 and December 31, 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)
September 30, 2013
Investment securities available for sale:
U.S. Treasury and federal agencies		$	6,346			(25	)		—		—
Obligations of states and political subdivisions			577			(2	)		559		(4	)
Mortgage-backed securities:
Government issued or guaranteed			174,503			(1,126	)		5,731		(128	)
Privately issued			—			—			107		(5	)
Collateralized debt obligations			—			—			5,995		(1,107	)
Other debt securities			1,576			(7	)		102,898		(20,008	)
Equity securities			2,777			(845	)		—		—
			185,779			(2,005	)		115,290		(21,252	)
Investment securities held to maturity:
Obligations of states and political subdivisions			14,751			(70	)		1,558		(18	)
Mortgage-backed securities:
Government issued or guaranteed			1,259,353			(29,015	)		—		—
Privately issued			—			—			167,876		(56,891	)
			1,274,104			(29,085	)		169,434		(56,909	)
Total		$	1,459,883			(31,090	)		284,724		(78,161	)
		Less than 12 months						12 months or more
		Fair value			Unrealized			Fair value		Unrealized
					losses					losses
		(in thousands)
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 299 individual investment securities with aggregate gross unrealized losses of $109 million at September 30, 2013. Approximately $57 million of the unrealized losses pertained to privately issued mortgage-backed securities with a cost basis of $225 million. The Company also had $21 million of unrealized losses on trust preferred securities issued by financial institutions and securities backed by trust preferred securities having a cost basis of $132 million. Based on a review of each of the remaining securities in the investment securities portfolio at September 30, 2013, the Company concluded that it expected to recover the amortized cost basis of its investment. As of September 30, 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 September 30, 2013, the Company has not identified events or changes in circumstances which may have a significant adverse effect on the fair value of the $298 million of cost method investment securities.

Loans_and_Leases_and_the_Allow

Loans and Leases and the Allowance for Credit Losses	9 Months Ended
	Sep. 30, 2013
Receivables [Abstract]	'
Loans and Leases and the Allowance for Credit Losses	'
	4	Loans and leases and the allowance for credit losses
	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 is as follows:
			September 30,			December 31,
			2013			2012
			(in thousands)
	Outstanding principal balance		$	5,274,466			6,705,120
	Carrying amount:
	Commercial, financial, leasing, etc.			730,743			928,107
	Commercial real estate			1,875,842			2,567,050
	Residential real estate			598,820			707,309
	Consumer			1,357,847			1,637,887
			$	4,563,252			5,840,353
	Purchased impaired loans included in the table above totaled $357 million at September 30, 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 three months and nine months ended September 30, 2013 and 2012 follows:
			Three months ended September 30
			2013						2012
			Purchased			Other			Purchased			Other
			impaired			acquired			impaired			acquired
			(in thousands)
	Balance at beginning of period		$	55,149			622,093		$	55,599			733,161
	Interest income			(10,428	)		(60,786	)		(12,436	)		(74,936	)
	Reclassifications from nonaccretable balance, net			172			—			542			—
	Other (a)			—			6,254			—			1,382
	Balance at end of period		$	44,893			567,561		$	43,705			659,607
			Nine months ended September 30
			2013						2012
			Purchased			Other			Purchased			Other
			impaired			acquired			impaired			acquired
			(in thousands)
	Balance at beginning of period		$	42,252			638,272		$	30,805			807,960
	Interest income			(28,879	)		(190,072	)		(29,721	)		(228,908	)
	Reclassifications from nonaccretable balance, net			31,520			122,519			42,621			98,165
	Other (a)			—			(3,158	)		—			(17,610	)
	Balance at end of period		$	44,893			567,561		$	43,705			659,607
	(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 September 30, 2013 and December 31, 2012 were as follows:
									90 Days or
									more past
									due and accruing
			Current			30-89			Non-			Acquired			Purchased			Nonaccrual			Total
						Days			acquired			(a)			impaired
						past due									(b)
									(in thousands)
	September 30, 2013
	Commercial, financial, leasing, etc.		$	17,678,290			91,757			2,582			11,147			16,257			111,116			17,911,149
	Real estate:
	Commercial			21,447,385			179,972			12,859			50,853			101,049			198,397			21,990,515
	Residential builder and developer			921,728			10,622			52			12,353			138,651			113,096			1,196,502
	Other commercial construction			3,029,504			16,903			1,888			5,090			68,539			36,326			3,158,250
	Residential			7,884,094			301,564			317,660			44,489			30,201			252,987			8,830,995
	Residential Alt-A			297,840			18,263			—			—			—			80,905			397,008
	Consumer:
	Home equity lines and loans			6,027,315			32,428			—			29,472			2,640			77,537			6,169,392
	Automobile			1,144,216			39,221			—			181			—			22,087			1,205,705
	Other			2,736,469			34,886			4,751			—			—			23,420			2,799,526
	Total		$	61,166,841			725,616			339,792			153,585			357,337			915,871			63,659,042
									90 Days or
									more past
									due and accruing
			Current			30-89			Non-			Acquired			Purchased			Nonaccrual			Total
						Days			acquired			(a)			impaired
						past due									(b)
			(in thousands)
	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.
One-to-four family residential mortgage loans held for sale were $667 million and $1.2 billion at September 30, 2013 and December 31, 2012, respectively. Commercial mortgage loans held for sale were $152 million at September 30, 2013 and $200 million at December 31, 2012.
Changes in the allowance for credit losses for the three months ended September 30, 2013 were as follows:
		Commercial,			Real Estate
		Financial,
		Leasing, etc.			Commercial			Residential			Consumer			Unallocated			Total
		(in thousands)
Beginning balance		$	268,867			324,264			85,311			174,291			74,332		$	927,065
Provision for credit losses			20,209			12,139			315			14,935			402			48,000
Allowance related to loans securitized and sold			—			—			—			(11,000	)		—			(11,000	)
Net charge-offs
Charge-offs			(30,931	)		(7,701	)		(5,320	)		(20,242	)		—			(64,194	)
Recoveries			5,150			4,751			2,399			4,199			—			16,499
Net charge-offs			(25,781	)		(2,950	)		(2,921	)		(16,043	)		—			(47,695	)
Ending balance		$	263,295			333,453			82,705			162,183			74,734		$	916,370
Changes in the allowance for credit losses for the three months ended September 30, 2012 were as follows:
		Commercial,			Real Estate
		Financial,
		Leasing, etc.			Commercial			Residential			Consumer			Unallocated			Total
		(in thousands)
Beginning balance		$	244,728			341,521			93,269			164,352			73,158		$	917,028
Provision for credit losses			439			9,891			8,247			26,962			461			46,000
Net charge-offs
Charge-offs			(8,874	)		(7,982	)		(8,687	)		(24,553	)		—			(50,096	)
Recoveries			1,174			1,421			1,139			4,557			—			8,291
Net charge-offs			(7,700	)		(6,561	)		(7,548	)		(19,996	)		—			(41,805	)
Ending balance		$	237,467			344,851			93,968			171,318			73,619		$	921,223
Changes in the allowance for credit losses for the nine months ended September 30, 2013 were as follows:
		Commercial,			Real Estate
		Financial,
		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			93,736			914			3,913			43,478			959			143,000
Allowance related to loans securitized and sold			—			—			—			(11,000	)		—			(11,000	)
Net charge-offs
Charge-offs			(86,787	)		(21,493	)		(18,583	)		(62,905	)		—			(189,768	)
Recoveries			9,587			16,931			8,568			13,192			—			48,278
Net charge-offs			(77,200	)		(4,562	)		(10,015	)		(49,713	)		—			(141,490	)
Ending balance		$	263,295			333,453			82,705			162,183			74,734		$	916,370
Changes in the allowance for credit losses for the nine months ended September 30, 2012 were as follows:
		Commercial,			Real Estate
		Financial,
		Leasing, etc.			Commercial			Residential			Consumer			Unallocated			Total
		(in thousands)
Beginning balance		$	234,022			367,637			91,915			143,121			71,595		$	908,290
Provision for credit losses			29,663			4,322			30,064			88,927			2,024			155,000
Net charge-offs
Charge-offs			(32,989	)		(31,578	)		(32,812	)		(77,155	)		—			(174,534	)
Recoveries			6,771			4,470			4,801			16,425			—			32,467
Net charge-offs			(26,218	)		(27,108	)		(28,011	)		(60,730	)		—			(142,067	)
Ending balance		$	237,467			344,851			93,968			171,318			73,619		$	921,223
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 anytime. Except for consumer and residential mortgage 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 or more. 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 September 30, 2013 and December 31, 2012 and for the three months and nine months ended September 30, 2013 and September 30, 2012.
		September 30, 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.		$	93,568			114,572			25,530			127,282			149,534			33,829
Real estate:
Commercial			127,921			152,885			24,104			121,542			143,846			23,641
Residential builder and developer			61,947			102,395			7,374			115,306			216,218			25,661
Other commercial construction			74,116			77,180			3,104			73,544			76,869			6,836
Residential			100,287			118,572			6,537			103,451			121,819			3,521
Residential Alt-A			115,695			128,446			15,000			128,891			141,940			17,000
Consumer:
Home equity lines and loans			13,258			14,372			3,408			12,360			13,567			2,254
Automobile			42,106			42,106			12,060			49,210			49,210			14,273
Other			16,057			16,057			4,169			14,408			14,408			5,667
			644,955			766,585			101,286			745,994			927,411			132,682
With no related allowance recorded:
Commercial, financial, leasing, etc.			24,945			30,551			—			32,631			42,199			—
Real estate:
Commercial			77,284			99,461			—			78,380			100,337			—
Residential builder and developer			56,015			84,852			—			74,307			105,438			—
Other commercial construction			19,960			24,051			—			23,018			23,532			—
Residential			83,041			93,898			—			86,342			96,448			—
Residential Alt-A			28,397			52,565			—			31,354			58,768			—
			289,642			385,378			—			326,032			426,722			—
Total:
Commercial, financial, leasing, etc.			118,513			145,123			25,530			159,913			191,733			33,829
Real estate:
Commercial			205,205			252,346			24,104			199,922			244,183			23,641
Residential builder and developer			117,962			187,247			7,374			189,613			321,656			25,661
Other commercial construction			94,076			101,231			3,104			96,562			100,401			6,836
Residential			183,328			212,470			6,537			189,793			218,267			3,521
Residential Alt-A			144,092			181,011			15,000			160,245			200,708			17,000
Consumer:
Home equity lines and loans			13,258			14,372			3,408			12,360			13,567			2,254
Automobile			42,106			42,106			12,060			49,210			49,210			14,273
Other			16,057			16,057			4,169			14,408			14,408			5,667
Total		$	934,597			1,151,963			101,286			1,072,026			1,354,133			132,682
		Three months ended									Three months ended
		September 30, 2013									September 30, 2012
					Interest income									Interest income
					recognized									recognized
		Average			Total			Cash			Average			Total			Cash
		recorded						basis			recorded						basis
		investment									investment
		(in thousands)
Commercial, financial, leasing, etc.		$	149,357			516			516			141,166			1,507			1,507
Real estate:
Commercial			205,971			716			716			180,009			531			531
Residential builder and developer			130,855			213			188			237,847			476			370
Other commercial construction			95,486			208			208			84,604			9			9
Residential			180,995			1,391			865			131,114			1,269			765
Residential Alt-A			147,056			1,763			692			167,780			1,836			593
Consumer:
Home equity lines and loans			12,810			167			49			11,949			172			48
Automobile			42,957			710			127			51,138			863			185
Other			15,791			161			50			11,996			121			52
Total		$	981,278			5,845			3,411			1,017,603			6,784			4,060
		Nine months ended									Nine months ended
		September 30, 2013									September 30, 2012
					Interest income									Interest income
					recognized									recognized
		Average			Total			Cash			Average			Total			Cash
		recorded						basis			recorded						basis
		investment									investment
		(in thousands)
Commercial, financial, leasing, etc.		$	164,877			6,358			6,358			155,627			2,659			2,659
Real estate:
Commercial			200,354			1,428			1,428			179,524			2,087			2,087
Residential builder and developer			159,308			871			637			260,858			1,202			801
Other commercial construction			97,268			3,322			3,322			100,242			5,019			5,019
Residential			184,719			4,795			3,188			128,646			3,926			2,453
Residential Alt-A			151,992			5,173			1,799			174,390			5,432			1,666
Consumer:
Home equity lines and loans			12,633			499			127			11,024			502			136
Automobile			45,075			2,226			404			52,249			2,632			553
Other			15,438			468			153			10,097			320			138
Total		$	1,031,664			25,140			17,416			1,072,657			23,779			15,512
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 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 and commercial real estate loans.
					Real Estate
		Commercial,			Commercial			Residential			Other
		Financial,						Builder and			Commercial
		Leasing, etc.						Developer			Construction
		(in thousands)
September 30, 2013
Pass		$	17,022,772			20,978,696			1,005,932			3,066,941
Criticized accrual			777,261			813,422			77,474			54,983
Criticized nonaccrual			111,116			198,397			113,096			36,326
Total		$	17,911,149			21,990,515			1,196,502			3,158,250
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 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)
September 30, 2013
Individually evaluated for impairment		$	25,530			34,139			21,517			19,637		$	100,823
Collectively evaluated for impairment			234,912			298,579			59,645			141,202			734,338
Purchased impaired			2,853			735			1,543			1,344			6,475
Allocated		$	263,295			333,453			82,705			162,183			841,636
Unallocated															74,734
Total														$	916,370
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)
September 30, 2013
Individually evaluated for impairment		$	118,513			413,443			326,860			71,421		$	930,237
Collectively evaluated for impairment			17,776,379			25,623,585			8,870,942			10,100,562			62,371,468
Purchased impaired			16,257			308,239			30,201			2,640			357,337
Total		$	17,911,149			26,345,267			9,228,003			10,174,623		$	63,659,042
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
During the normal course of business, the Company modifies loans to maximize recovery efforts. If the borrower is experiencing financial difficulty and a concession is granted, the Company considers such modifications as troubled debt restructurings and classifies those loans as either nonaccrual loans or renegotiated loans. The types of concessions that the Company grants typically include principal deferrals and interest rate concessions, but may also include other types of concessions.
The tables below summarize the Company’s loan modification activities that were considered troubled debt restructurings for the three months ended September 30, 2013 and 2012:
					Recorded investment						Financial effects of
											modification
Three months ended September 30, 2013		Number			Pre-			Post-			Recorded			Interest
					modification			modification			investment			(b)
											(a)
		(dollars in thousands)
Commercial, financial, leasing, etc.
Principal deferral			14		$	2,407		$	2,266		$	(141	)	$	—
Other			2			1,773			2,067			294			—
Combination of concession types			3			374			374			—			(25	)
Real estate:
Commercial
Principal deferral			10			4,160			4,134			(26	)		—
Other			2			449			475			26			—
Combination of concession types			6			1,868			2,264			396			(156	)
Residential builder and developer
Principal deferral			1			249			241			(8	)		—
Other commercial construction
Principal deferral			1			226			158			(68	)		—
Residential
Principal deferral			6			860			912			52			—
Combination of concession types			14			1,258			1,308			50			(197	)
Residential Alt-A
Principal deferral			5			764			773			9			—
Combination of concession types			4			332			496			164			(252	)
Consumer:
Home equity lines and loans
Principal deferral			2			179			179			—			—
Combination of concession types			9			682			682			—			(79	)
Automobile
Principal deferral			121			1,718			1,718			—			—
Interest rate reduction			2			19			19			—			(2	)
Other			20			42			42			—			—
Combination of concession types			61			551			551			—			(33	)
Other
Principal deferral			9			60			60			—			—
Combination of concession types			18			470			470			—			(86	)
Total			310		$	18,441		$	19,189		$	748		$	(830	)
(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.
					Recorded investment						Financial effects of
											modification
Three months ended September 30, 2012		Number			Pre-			Post-			Recorded			Interest
					modification			modification			investment			(b)
											(a)
		(dollars in thousands)
Commercial, financial, leasing, etc.
Principal deferral			21		$	7,823		$	7,653		$	(170	)	$	—
Combination of concession types			2			327			322			(5	)		(39	)
Real estate:
Commercial
Principal deferral			8			5,951			6,238			287			—
Combination of concession types			1			214			214			—			(49	)
Residential builder and developer
Principal deferral			11			17,383			16,275			(1,108	)		—
Combination of concession types			1			2,486			2,486			—			—
Other commercial construction
Principal deferral			2			5,429			4,702			(727	)		—
Residential
Principal deferral			5			738			772			34			—
Combination of concession types			18			5,490			5,553			63			(150	)
Residential Alt-A
Principal deferral			1			218			220			2			—
Combination of concession types			13			2,771			2,795			24			—
Consumer:
Home equity lines and loans
Principal deferral			5			434			434			—			—
Combination of concession types			11			976			976			—			(125	)
Automobile
Principal deferral			135			1,721			1,721			—			—
Interest rate reduction			9			157			157			—			(11	)
Other			20			68			68			—			—
Combination of concession types			109			2,329			2,329			—			(319	)
Other
Principal deferral			14			336			336			—			—
Other			1			1			1			—			—
Combination of concession types			22			339			339			—			(97	)
Total			409		$	55,191		$	53,591		$	(1,600	)	$	(790	)
(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 tables below summarize the Company’s loan modification activities that were considered troubled debt restructurings for the nine months ended September 30, 2013 and 2012:
					Recorded investment						Financial effects of
											modification
Nine months ended September 30, 2013		Number			Pre-			Post-			Recorded			Interest
					modification			modification			investment			(b)
											(a)
		(dollars in thousands)
Commercial, financial, leasing, etc.
Principal deferral			53		$	9,283		$	9,070		$	(213	)	$	—
Other			4			50,433			50,924			491			—
Combination of concession types			6			2,206			1,696			(510	)		(25	)
Real estate:
Commercial
Principal deferral			23			38,187			38,027			(160	)		—
Other			2			449			475			26			—
Combination of concession types			8			2,450			2,845			395			(212	)
Residential builder and developer
Principal deferral			16			19,102			18,303			(799	)		—
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			21			2,642			2,877			235			—
Other			1			195			195			—			—
Combination of concession types			52			72,917			69,734			(3,183	)		(754	)
Residential Alt-A
Principal deferral			6			863			875			12			—
Combination of concession types			17			2,426			2,715			289			(640	)
Consumer:
Home equity lines and loans
Principal deferral			6			359			361			2			—
Interest rate reduction			1			99			99			—			(8	)
Other			1			106			106			—			—
Combination of concession types			19			1,299			1,299			—			(176	)
Automobile
Principal deferral			359			4,933			4,933			—			—
Interest rate reduction			11			159			159			—			(17	)
Other			65			274			274			—			—
Combination of concession types			184			2,148			2,148			—			(162	)
Other
Principal deferral			29			290			290			—			—
Interest rate reduction			1			12			12			—			(2	)
Other			1			12			12			—			—
Combination of concession types			90			2,394			2,394			—			(587	)
Total			983		$	233,447		$	229,746		$	(3,701	)	$	(3,118	)
(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.
					Recorded investment						Financial effects of
											modification
Nine months ended September 30, 2012		Number			Pre-			Post-			Recorded			Interest
					modification			modification			investment			(b)
											(a)
		(dollars in thousands)
Commercial, financial, leasing, etc.
Principal deferral			39		$	21,027		$	19,668		$	(1,359	)	$	—
Other			3			2,967			3,052			85			—
Combination of concession types			3			372			366			(6	)		(72	)
Real estate:
Commercial
Principal deferral			11			10,387			10,642			255			—
Interest rate reduction			1			383			430			47			(89	)
Combination of concession types			5			1,424			1,445			21			(305	)
Residential builder and developer
Principal deferral			19			26,708			24,812			(1,896	)		—
Combination of concession types			3			4,836			5,212			376			—
Other commercial construction
Principal deferral			5			66,317			65,600			(717	)		—
Residential
Principal deferral			27			3,302			3,447			145			—
Combination of concession types			47			10,475			10,658			183			(415	)
Residential Alt-A
Principal deferral			5			768			785			17			—
Combination of concession types			28			5,640			5,732			92			(49	)
Consumer:
Home equity lines and loans
Principal deferral			15			1,285			1,285			—			—
Interest rate reduction			1			144			144			—			(6	)
Combination of concession types			17			1,691			1,691			—			(272	)
Automobile
Principal deferral			484			6,306			6,306			—			—
Interest rate reduction			16			234			234			—			(16	)
Other			51			239			239			—			—
Combination of concession types			298			5,108			5,108			—			(601	)
Other
Principal deferral			73			1,117			1,117			—			—
Interest rate reduction			3			23			23			—			(3	)
Other			10			50			50			—			—
Combination of concession types			74			700			700			—			(155	)
Total			1,238		$	171,503		$	168,746		$	(2,757	)	$	(1,983	)
(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 September 30, 2013 and 2012 for which there was a subsequent payment default during the nine-month periods ended September 30, 2013 and 2012, were $20 million (largely commercial real estate loans) and $13 million (largely residential builder and developer loans), respectively.

Borrowings

Borrowings	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]	'
Borrowings	'
	5	Borrowings
	M&T had $1.2 billion of fixed and floating rate junior subordinated deferrable interest debentures (“Junior Subordinated Debentures”) outstanding at September 30, 2013 which are held by various trusts that 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.
	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.
	During the first quarter of 2013, M&T Bank instituted a Bank Note Program whereby M&T Bank may offer up to $5 billion of 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.
	Also included in long-term borrowings are agreements to repurchase securities of $1.4 billion at each of September 30, 2013 and December 31, 2012. 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 September 30, 2013 and December 31, 2012.

Shareholders_Equity

Shareholders' Equity	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]	'
Shareholders' Equity	'
	6	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:
			Shares		Carrying		Carrying
			issued and		value		value
			outstanding		September 30, 2013		December 31, 2012
					(dollars in thousands)
	Series A (a)
	Fixed Rate Cumulative Perpetual Preferred Stock, Series A, $1,000 liquidation preference per share			230,000	$	229,236	$	226,965
	Series C (a) (b)
	Fixed Rate Cumulative Perpetual Preferred Stock, Series C, $1,000 liquidation preference per share			151,500		149,774		145,535
	Series D (c)
	Fixed Rate Non-Cumulative Perpetual Preferred Stock, Series D, $10,000 liquidation preference per share			50,000		500,000		500,000
	(a)	Shares were originally issued as part of the Troubled Asset Relief Program – Capital Purchase Program (“TARP”) of the U.S. Department of Treasury (“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, will accrue and be paid quarterly at a rate of 5% per year through November 14, 2013 and at 6.375% thereafter, and that M&T will 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 the third quarter of 2013, 57,327 of the Series A warrants were exercised in a “cashless” exercise, resulting in the issuance of 21,130 common shares. Remaining outstanding Series A warrants were 1,161,195 at September 30, 2013.
	(b)	Shares were assumed in an acquisition and a new Series C Preferred Stock was designated.
	(c)	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.
	A warrant expiring on May 16, 2021 providing for the purchase of 95,383 shares of M&T common stock at $518.96 per share was outstanding at September 30, 2013 and December 31, 2012. The obligation under that warrant was assumed by M&T in an acquisition.

Pension_Plans_and_Other_Postre

Pension Plans and Other Postretirement Benefits	9 Months Ended
	Sep. 30, 2013
Compensation And Retirement Disclosure [Abstract]	'
Pension Plans and Other Postretirement Benefits	'
	7	Pension plans and other postretirement benefits
	The Company provides defined benefit pension and other postretirement benefits (including health care and life insurance benefits) to qualified retired employees. Net periodic defined benefit cost for defined benefit plans consisted of the following:
			Pension						Other
			benefits						postretirement
									benefits
			Three months ended September 30
			2013			2012			2013			2012
			(in thousands)
	Service cost		$	6,090			7,387			186			167
	Interest cost on projected benefit obligation			15,032			15,509			673			934
	Expected return on plan assets			(21,838	)		(17,627	)		—			—
	Amortization of prior service cost			(1,639	)		(1,640	)		(340	)		5
	Amortization of net actuarial loss			10,269			9,291			90			133
	Net periodic benefit cost		$	7,914			12,920			609			1,239
			Pension						Other
			benefits						postretirement
									benefits
			Nine months ended September 30
			2013			2012			2013			2012
			(in thousands)
	Service cost		$	18,270			22,162			557			501
	Interest cost on projected benefit obligation			45,097			46,527			2,018			2,803
	Expected return on plan assets			(65,515	)		(52,883	)		—			—
	Amortization of prior service cost			(4,917	)		(4,919	)		(1,019	)		15
	Amortization of net actuarial loss			30,807			27,874			270			398
	Net periodic benefit cost		$	23,742			38,761			1,826			3,717
	Expense incurred in connection with the Company’s defined contribution pension and retirement savings plans totaled $12,440,000 and $11,289,000 for the three months ended September 30, 2013 and 2012, respectively, and $40,757,000 and $37,304,000 for the nine months ended September 30, 2013 and 2012, respectively.

Earnings_Per_Common_Share

Earnings Per Common Share	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]	'
Earnings Per Common Share	'
	8	Earnings per common share
	The computations of basic earnings per common share follow:
			Three months ended						Nine months ended
			September 30						September 30
			2013			2012			2013			2012
			(in thousands, except per share)
	Income available to common shareholders:
	Net income		$	294,479			293,462		$	917,058			733,305
	Less: Preferred stock dividends (a)			(13,363	)		(13,363	)		(40,088	)		(40,088	)
	Amortization of preferred stock discount (a)			(2,235	)		(2,033	)		(6,575	)		(5,921	)
	Net income available to common equity			278,881			278,066			870,395			687,296
	Less: Income attributable to unvested stock-based compensation awards			(3,545	)		(4,181	)		(11,451	)		(10,475	)
	Net income available to common shareholders		$	275,336			273,885		$	858,944			676,821
	Weighted-average shares outstanding:
	Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards			130,836			127,741			130,088			127,449
	Less: Unvested stock-based compensation awards			(1,665	)		(1,923	)		(1,719	)		(1,939	)
	Weighted-average shares outstanding			129,171			125,818			128,369			125,510
	Basic earnings per common share		$	2.13			2.18		$	6.69			5.39
	(a)	Including impact of not as yet declared cumulative dividends.
	The computations of diluted earnings per common share follow:
			Three months ended						Nine months ended
			September 30						September 30
			2013			2012			2013			2012
			(in thousands, except per share)
	Net income available to common equity		$	278,881			278,066		$	870,395			687,296
	Less: Income attributable to unvested stock-based compensation awards			(3,525	)		(4,170	)		(11,395	)		(10,454	)
	Net income available to common shareholders		$	275,356			273,896		$	859,000			676,842
	Adjusted weighted-average shares outstanding:
	Common and unvested stock-based compensation awards			130,836			127,741			130,088			127,449
	Less: Unvested stock-based compensation awards			(1,665	)		(1,923	)		(1,719	)		(1,939	)
	Plus: Incremental shares from assumed conversion of stock-based compensation awards and warrants to purchase common stock			1,094			474			943			426
	Adjusted weighted-average shares outstanding			130,265			126,292			129,312			125,936
	Diluted earnings per common share		$	2.11			2.17		$	6.64			5.37
	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 3.1 million and 9.7 million common shares during the three-month periods ended September 30, 2013 and 2012, respectively, and 4.1 million and 9.9 million common shares during the nine-month periods ended September 30, 2013 and 2012, respectively, were not included in the computations of diluted earnings per common share because the effect on those periods would have been antidilutive.

Comprehensive_Income

Comprehensive Income	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]	'
Comprehensive Income	'
	9	Comprehensive income
	The following table displays the components of other comprehensive income (loss) and amounts reclassified from accumulated other comprehensive income (loss) to net income:
			Investment Securities
			With			All			Defined			Other			Total			Income			Net
			OTTI			other			benefit						amount			tax
									plans						before tax
			(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			59,523			(61,706	)		—			—			(2,183	)		814			(1,369	)
	Foreign currency translation adjustment			—			—			—			296			296			(91	)		205
	Total other comprehensive income before reclassifications			59,523			(61,706	)		—			296			(1,887	)		723			(1,164	)
	Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income:
	Accretion of unrealized holding losses on held-to-maturity (“HTM”) securities			230			3,127			—			—			3,357	(a)		(1,318	)		2,039
	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			—			—			(5,936	)		—			(5,936	) (e)		2,330			(3,606	)
	Amortization of actuarial losses			—			—			31,077			—			31,077	(e)		(12,198	)		18,879
	Total reclassifications			51,247			(5,002	)		25,141			—			71,386			(28,020	)		43,366
	Total gain (loss) during the period			110,770			(66,708	)		25,141			296			69,499			(27,297	)		42,202
	Balance – September 30, 2013		$	18,935			85,491			(430,449	)		(135	)	$	(326,158	)		128,096		$	(198,062	)
			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			(8,099	)		153,908			—			—			145,809			(57,183	)		88,626
	Foreign currency translation adjustment			—			—			—			552			552			(201	)		351
	Total other comprehensive income before reclassifications			(8,099	)		153,908			—			552			146,361			(57,384	)		88,977
	Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income:
	Accretion of unrealized holding losses on HTM securities			1,544			3,495			—			—			5,039	(a)		(1,978	)		3,061
	OTTI charges recognized in net income			33,331			—			—			—			33,331	(b)		(13,082	)		20,249
	Gains realized in net income			—			(9	)		—			—			(9	) (c)		4			(5	)
	Amortization of gains on terminated cash flow hedges			—			—			—			(178	)		(178	) (d)		66			(112	)
	Amortization of prior service credit			—			—			(4,904	)		—			(4,904	) (e)		1,925			(2,979	)
	Amortization of actuarial losses			—			—			28,272			—			28,272	(e)		(11,097	)		17,175
	Total reclassifications			34,875			3,486			23,368			(178	)		61,551			(24,162	)		37,389
	Total gain (loss) during the period			26,776			157,394			23,368			374			207,912			(81,546	)		126,366
	Balance – September 30,2012		$	(111,543	)		167,151			(433,777	)		(688	)	$	(378,857	)		148,782		$	(230,075	)
	(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 the following:
			Investment securities						Defined			Other			Total
									benefit
			With			All			plans
			OTTI			other
	Balance – December 31, 2012		$	(55,790	)		92,581			(276,771	)		(284	)	$	(240,264	)
	Net gain (loss) during period			67,293			(40,569	)		15,273			205			42,202
	Balance – September 30, 2013		$	11,503			52,012			(261,498	)		(79	)	$	(198,062	)

Derivative_Financial_Instrumen

Derivative Financial Instruments	9 Months Ended
	Sep. 30, 2013
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'
Derivative Financial Instruments	'
	10	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 is not significant as of September 30, 2013.
	The net effect of interest rate swap agreements was to increase net interest income by $11 million and $9 million for the three-month periods ended September 30, 2013 and 2012, respectively, and $30 million and $27 million for the nine months ended September 30, 2013 and 2012, respectively.
	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-
			amount			maturity			average rate
									Fixed			Variable
			(in thousands)			(in years)
	September 30, 2013
	Fair value hedges:
	Fixed rate long-term borrowings (a)		$	1,400,000			3.9			4.42	%		1.22	%
	December 31, 2012
	Fair value hedges:
	Fixed rate long-term borrowings (a)		$	900,000			4.4			6.07	%		1.85	%
	(a)	Under the terms of these agreements, the Company receives settlement amounts at a fixed rate and pays at a variable rate.
	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 $15.9 billion and $15.5 billion at September 30, 2013 and December 31, 2012, respectively. The notional amounts of foreign currency and other option and futures contracts entered into for trading purposes aggregated $904 million and $869 million at September 30, 2013 and December 31, 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
			September 30,			December 31,			September 30,			December 31,
			2013			2012			2013			2012
			(in thousands)
	Derivatives designated and qualifying as hedging instruments
	Fair value hedges:
	Interest rate swap agreements (a)		$	114,083			143,179		$	—			—
	Commitments to sell real estate loans (a)			2,477			1,114			11,665			3,825
				116,560			144,293			11,665			3,825
	Derivatives not designated and qualifying as hedging instruments
	Mortgage-related commitments to originate real estate loans for sale (a)			18,186			48,056			5,111			197
	Commitments to sell real estate loans (a)			6,879			1,982			7,434			6,570
	Trading:
	Interest rate contracts (b)			285,442			399,963			248,311			365,616
	Foreign exchange and other option and futures contracts (b)			13,451			8,725			13,138			8,658
				323,958			458,726			273,994			381,041
	Total derivatives		$	440,518			603,019		$	285,659			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
			Three months ended						Three months ended
			September 30, 2013						September 30, 2012
			Derivative			Hedged item			Derivative			Hedged item
			(in thousands)
	Derivatives in fair value hedging relationships
	Interest rate swap agreements:
	Fixed rate long-term borrowings (a)		$	(86	)		(20	)	$	3,273			(3,252	)
	Derivatives not designated as hedging instruments
	Trading:
	Interest rate contracts (b)		$	2,778					$	777
	Foreign exchange and other option and futures contracts (b)			(862	)					74
	Total		$	1,916					$	851
			Amount of unrealized gain (loss) recognized
			Nine months ended						Nine months ended
			September 30, 2013						30-Sep-12
			Derivative			Hedged item			Derivative			Hedged item
			(in thousands)
	Derivatives in fair value hedging relationships
	Interest rate swap agreements:
	Fixed rate long-term borrowings (a)		$	(29,097	)		27,733		$	5,918			(5,876	)
	Derivatives not designated as hedging instruments
	Trading:
	Interest rate contracts (b)		$	5,974					$	3,996
	Foreign exchange and other option and futures contracts (b)			(2,469	)					(3,071	)
Total		$	3,505					$	925
(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 $27 million and $89 million at September 30, 2013 and December 31, 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 $229 million and $374 million at September 30, 2013 and December 31, 2012, respectively. After consideration of such netting arrangements, the net liability positions with counterparties aggregated $132 million and $281 million at September 30, 2013 and December 31, 2012, respectively. The Company was required to post collateral relating to those positions of $118 million and $266 million at September 30, 2013 and December 31, 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 of the derivative financial instruments could demand immediate incremental collateralization on those instruments in a net liability position. The aggregate fair value of all derivative financial instruments with such credit-risk-related contingent features in a net liability position on September 30, 2013 was $42 million, for which the Company had posted collateral of $29 million in the normal course of business. If the credit-risk-related contingent features had been triggered on September 30, 2013, the maximum amount of additional collateral the Company would have been required to post to counterparties was $13 million.
The aggregate fair value of derivative financial instruments in an asset position, which are subject to enforceable master netting arrangements, was $187 million and $164 million at September 30, 2013 and December 31, 2012, respectively. After consideration of such netting arrangements, the net asset positions with counterparties aggregated $98 million and $71 million at September 30, 2013 and December 31, 2012, respectively. Counterparties posted collateral relating to those positions of $96 million and $69 million at September 30, 2013 and December 31, 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	9 Months Ended
	Sep. 30, 2013
Text Block [Abstract]	'
Variable Interest Entities and Asset Securitizations	'
	11	Variable interest entities and asset securitizations
	In the third quarter of 2013, the Company securitized approximately $1.8 billion of one-to-four family residential mortgage loans in guaranteed mortgage securitizations with the Government National Mortgage Association (“Ginnie Mae”). Approximately $1.0 billion of such loans were formerly held in the Company’s loan portfolio, whereas the remaining $811 million of the loans were newly originated. The Company recognized gains of $35 million related to loans previously held for investment, which has been recorded in “other revenues from operations,” and gains of $15 million on newly originated loans, which has been reflected in “mortgage banking revenues.” In total, the Company securitized approximately $2.8 billion of one-to-four family residential mortgage loans in guaranteed mortgage securitizations with Ginnie Mae during the nine months ended September 30, 2013. Approximately $1.4 billion of such loans were formerly held in the Company’s loan portfolio, whereas the remaining $1.4 billion were newly originated. For the nine months ended September 30, 2013, the Company recognized pre-tax gains of $42 million related to loans previously held for investment, which have been recorded in “other revenues from operations,” and pre-tax gains of $25 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. In the third quarter of 2013, the Company securitized and sold approximately $1.4 billion of automobile loans held in its loan portfolio. The Company recognized gains of $21 million related to the sale, which has been recorded in “other revenues from operations.” The Company has securitized loans to improve its regulatory capital ratios and strengthen its liquidity and risk profile as a result of changing regulatory liquidity and capital 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 September 30, 2013 and December 31, 2012, the carrying values of the loans in the securitization trust were $126 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 September 30, 2013 and December 31, 2012 was $19 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 September 30, 2013 is limited to realizing the carrying value of the loans less the amount of the mortgage-backed securities held by the third parties.
	As described in note 5, 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 September 30, 2013 and December 31, 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 5.
	The Company has invested as a limited partner in various partnerships that collectively had total assets of approximately $1.4 billion and $1.5 billion at September 30, 2013 and December 31, 2012, respectively. 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 $250 million, including $57 million of unfunded commitments, at September 30, 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	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	12	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 September 30, 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.
	At December 31, 2012, 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. 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 depreciation or appreciation 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 September 30, 2013 and December 31, 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. The total amortized cost and fair value of securities backed by trust preferred securities issued by financial institutions and other entities were $43 million and $59 million, respectively, at September 30, 2013 and $43 million and $62 million, respectively, at December 31, 2012. 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 significant 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 originated 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 agreement assets and has considered its own credit risk in the valuation of its interest rate swap agreement liabilities.
	The following tables present assets and liabilities at September 30, 2013 and December 31, 2012 measured at estimated fair value on a recurring basis:
			Fair value			Level 1 (a)			Level 2 (a)			Level 3
			measurements at
			September 30,
			2013
			(in thousands)
	Trading account assets		$	371,370			48,344			323,026			—
	Investment securities available for sale:
	U.S. Treasury and federal agencies			37,887			—			37,887			—
	Obligations of states and political subdivisions			17,963			—			17,963			—
	Mortgage-backed securities:
	Government issued or guaranteed			4,330,399			—			4,330,399			—
	Privately issued			3,816			—			—			3,816
	Collateralized debt obligations			59,303			—			—			59,303
	Other debt securities			119,404			—			119,404			—
	Equity securities			123,408			91,075			32,333			—
				4,692,180			91,075			4,537,986			63,119
	Real estate loans held for sale			819,029			—			819,029			—
	Other assets (b)			141,625			—			123,440			18,185
	Total assets		$	6,024,204			139,419			5,803,481			81,304
	Trading account liabilities		$	261,449			—			261,449			—
	Other liabilities (b)			24,210			—			19,100			5,110
	Total liabilities		$	285,659			—			280,549			5,110
			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 three months and nine months ended September 30, 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 three months ended September 30, 2013 were as follows:
		Investment securities available for sale
		Privately issued			Collateralized			Other assets
		mortgage-backed			debt			and other
		securities			obligations			liabilities
		(in thousands)
Balance – June 30, 2013		$	5,272		$	59,916		$	7,408
Total gains (losses) realized/unrealized:
Included in earnings			—			—			24,440	(b)
Included in other comprehensive income			400	(e)		213	(e)		—
Settlements			(1,856	)		(826	)		—
Transfers in and/or out of Level 3 (c)			—			—			(18,773	)(d)
Balance – September 30, 2013		$	3,816		$	59,303		$	13,075
Changes in unrealized gains (losses) included in earnings related to assets still held at September 30, 2013		$	—		$	—		$	(1,727	)(b)
The changes in Level 3 assets and liabilities measured at estimated fair value on a recurring basis during the three months ended September 30, 2012 were as follows:
		Investment securities available for sale
		Privately issued			Collateralized			Other assets
		mortgage-backed			debt			and other
		securities			obligations			liabilities
		(in thousands)
Balance – June 30, 2012		$	1,080,519		$	55,098		$	34,051
Total gains (losses) realized/unrealized:
Included in earnings			(5,672	)(a)		—			84,864	(b)
Included in other comprehensive income			40,603	(e)		3,297	(e)		—
Settlements			(49,814	)		(1,194	)		—
Transfers in and/or out of Level 3 (c)			—			—			(48,570	)(d)
Balance – September 30, 2012		$	1,065,636		$	57,201		$	70,345
Changes in unrealized gains (losses) included in earnings related to assets still held at September 30, 2012		$	(5,672	)(a)	$	—		$	63,357	(b)
The changes in Level 3 assets and liabilities measured at estimated fair value on a recurring basis during the nine months ended September 30, 2013 were as follows:
		Investment securities available for sale
		Privately issued			Collateralized			Other assets
		mortgage-backed			debt			and other
		securities			obligations			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)		—			83,252	(b)
Included in other comprehensive income			116,984	(e)		(324	)(e)		—
Sales			(978,608	)		—			—
Settlements			(102,344	)		(2,242	)		—
Transfers in and/or out of Level 3 (c)			—			—			(118,036	)(d)
Balance – September 30, 2013		$	3,816		$	59,303		$	13,075
Changes in unrealized gains included in earnings related to assets still held at September 30, 2013		$	—		$	—		$	925	(b)
The changes in Level 3 assets and liabilities measured at estimated fair value on a recurring basis during the nine months ended September 30, 2012 were as follows:
		Investment securities available for sale
		Privately issued			Collateralized			Other assets
		mortgage-backed			debt			and other
		securities			obligations			liabilities
		(in thousands)
Balance – January 1, 2012		$	1,151,285		$	52,500		$	6,923
Total gains (losses) realized/unrealized:
Included in earnings			(27,976	)(a)		—			157,381	(b)
Included in other comprehensive income			89,397	(e)		7,008	(e)		—
Settlements			(147,070	)		(2,307	)		—
Transfers in and/or out of Level 3 (c)			—			—			(93,959	)(d)
Balance – September 30, 2012		$	1,065,636		$	57,201		$	70,345
Changes in unrealized gains (losses) included in earnings related to assets still held at September 30, 2012		$	(27,976	)(a)	$	—		$	70,187	(b)
(a)	Reported as an OTTI 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 the nine-month period ended September 30, 2012, the Company recognized OTTI losses related to certain mortgage-backed securities of $5 million. 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 available-for-sale privately issued mortgage-backed securities, were weighted and averaged when estimating fair value. Due to the presence of significant unobservable inputs that valuation was 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.
Loans
Loans are generally not recorded at fair value on a recurring basis. Periodically, the Company records nonrecurring adjustments to the carrying value of loans based on fair value measurements for partial charge-offs of the uncollectible portions of those loans. Nonrecurring adjustments also include certain impairment amounts for collateral-dependent loans when establishing the allowance for credit losses. Such amounts are generally based on the fair value of the underlying collateral supporting the loan and, as a result, the carrying value of the loan less the calculated valuation amount does not necessarily represent the fair value of the loan. Real estate collateral is typically valued using appraisals or other indications of value based on recent comparable sales of similar properties or assumptions generally observable in the marketplace and the related nonrecurring fair value measurement adjustments have generally been classified as Level 2, unless significant adjustments have been made to the valuation that are not readily observable by market participants. Non-real estate collateral supporting commercial loans generally consists of business assets such as receivables, inventory and equipment. Fair value estimations are typically determined by discounting recorded values of those assets to reflect estimated net realizable value considering specific borrower facts and circumstances and the experience of credit personnel in their dealings with similar borrower collateral liquidations. Such discounts were generally in the range of 10% to 80% at September 30, 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 $247 million at September 30, 2013, ($163 million and $84 million of which were classified as Level 2 and Level 3, respectively) and $320 million at September 30, 2012 ($221 million and $99 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 on September 30, 2013 were decreases of $33 million and $82 million for the three months and nine months ended September 30, 2013, respectively. Changes in fair value recognized for partial charge-offs of loans and loan impairment reserves on loans held by the Company on September 30, 2012 were decreases of $17 million and $47 million for the three- and nine-month periods ended September 30, 2012, 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 $20 million and $51 million at September 30, 2013 and September 30, 2012, respectively. Changes in fair value recognized for those foreclosed assets held by the Company were not material during the three- and nine-month periods ended September 30, 2013 and 2012.
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 September 30, 2013 and December 31, 2012.
		Fair value at			Valuation		Unobservable	Range
		September 30, 2013						(weighted-
					technique		input/assumptions	average)
		(in thousands)
Recurring fair value measurements
Privately issued mortgage–backed securities		$	3,816		Two independent price quotes		—	—
Collateralized debt obligations			59,303		Discounted cash flow		Probability of default	13%-55% (39%)
							Loss severity	100%
Net other assets (liabilities)(a)			13,075		Discounted cash flow		Commitment expirations	0%-91% (21%)
		Fair value at			Valuation		Unobservable	Range
		December 31, 2012						(weighted-
					technique		input/assumptions	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 collateralized debt securities 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:
		September 30, 2013
		Carrying			Estimated			Level 1			Level 2			Level 3
		amount			fair value
		(in thousands)
Financial assets:
Cash and cash equivalents		$	2,059,753		$	2,059,753		$	1,992,949		$	66,804		$	—
Interest-bearing deposits at banks			1,925,811			1,925,811			—			1,925,811			—
Trading account assets			371,370			371,370			48,344			323,026			—
Investment securities			8,309,773			8,268,045			91,075			7,945,975			230,995
Loans and leases:
Commercial loans and leases			17,911,149			17,685,646			—			—			17,685,646
Commercial real estate loans			26,345,267			26,256,932			—			151,690			26,105,242
Residential real estate loans			9,228,003			9,198,681			—			5,757,491			3,441,190
Consumer loans			10,174,623			10,151,004			—			—			10,151,004
Allowance for credit losses			(916,370	)		—			—			—			—
Loans and leases, net			62,742,672			63,292,263			—			5,909,181			57,383,082
Accrued interest receivable			234,208			234,208			—			234,208			—
Financial liabilities:
Noninterest-bearing deposits		$	(24,150,771	)	$	(24,150,771	)	$	—		$	(24,150,771	)	$	—
Savings deposits and NOW accounts			(38,253,417	)		(38,253,417	)		—			(38,253,417	)		—
Time deposits			(3,831,443	)		(3,853,552	)		—			(3,853,552	)		—
Deposits at Cayman Islands office			(316,510	)		(316,510	)		—			(316,510	)		—
Short-term borrowings			(246,019	)		(246,019	)		—			(246,019	)		—
Long-term borrowings			(5,121,326	)		(5,257,947	)		—			(5,257,947	)		—
Accrued interest payable			(62,773	)		(62,773	)		—			(62,773	)		—
Trading account liabilities			(261,449	)		(261,449	)		—			(261,449	)		—
Other financial instruments:
Commitments to originate real estate loans for sale		$	13,075		$	13,075		$	—		$	—		$	13,075
Commitments to sell real estate loans			(9,743	)		(9,743	)		—			(9,743	)		—
Other credit-related commitments			(114,048	)		(114,048	)		—			—			(114,048	)
Interest rate swap agreements used for interest rate risk management			114,083			114,083			—			114,083			—
		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 13, 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	9 Months Ended
	Sep. 30, 2013
Commitments And Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	13	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.
			September 30,		December 31,
			2013		2012
			(in thousands)
	Commitments to extend credit
	Home equity lines of credit		$	6,239,383		6,282,615
	Commercial real estate loans to be sold			60,479		139,929
	Other commercial real estate and construction			3,877,466		3,819,342
	Residential real estate loans to be sold			647,523		1,550,441
	Other residential real estate			410,647		445,268
	Commercial and other			10,629,010		10,070,711
	Standby letters of credit			3,684,608		4,025,329
	Commercial letters of credit			49,757		53,201
	Financial guarantees, indemnification contracts and other			2,394,180		2,120,361
	Commitments to sell real estate loans			1,294,488		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 Delegated Underwriting and Servicing program. The Company’s maximum credit risk for recourse associated with loans sold under this program totaled approximately $2.2 billion at September 30, 2013 and $2.0 billion at December 31, 2012.
	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 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 $5 million in 2013 and $6 million per year from 2014 through 2017.
	The Company also has commitments under long-term operating leases.
	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 $46 million at September 30, 2013. Assets of subsidiaries providing reinsurance that are available to satisfy claims totaled approximately $37 million at September 30, 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 September 30, 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. Management, after consultation with legal counsel, does not anticipate that the aggregate ultimate liability arising out of litigation pending or threatened against M&T or its subsidiaries will be material to the Company’s consolidated financial position. On an on-going basis the Company assesses its 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 $70 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	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]	'
Segment Information	'
	14	Segment information
	Reportable segments have been determined based upon the Company’s internal profitability reporting system, which is organized by strategic business unit. Certain strategic business units have been combined for segment information reporting purposes where the nature of the products and services, the type of customer and the distribution of those products and services are similar. The reportable segments are Business Banking, Commercial Banking, Commercial Real Estate, Discretionary Portfolio, Residential Mortgage Banking and Retail Banking.
	The financial information of the Company’s segments was compiled utilizing the accounting policies described in note 22 to the Company’s consolidated financial statements as of and for the year ended December 31, 2012. 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, the financial information of the reported segments is not necessarily comparable with similar information reported by other financial institutions. As also described in note 22 to the Company’s 2012 consolidated financial statements, neither goodwill nor core deposit and other intangible assets (and the amortization charges associated with such assets) resulting from acquisitions of financial institutions have been allocated to the Company’s reportable segments, but are included in the “All Other” category. The Company does, however, assign such intangible assets to business units for purposes of testing for impairment.
	Information about the Company’s segments is presented in the following table:
			Three months ended September 30
			2013								2012
			Total		Inter-			Net			Total			Inter-			Net
			revenues(a)		segment			income			revenues(a)			segment			income
					revenues			(loss)						revenues			(loss)
			(in thousands)
	Business Banking		$	107,887		1,237			26,552			114,181			1,011			38,411
	Commercial Banking			257,317		1,383			97,221			255,498			1,561			112,654
	Commercial Real Estate			171,094		399			79,450			169,806			5,031			75,896
	Discretionary Portfolio			44,040		(19,584	)		25,182			1,805			(25,593	)		(5,039	)
	Residential Mortgage Banking			92,505		15,241			12,731			138,662			28,454			44,727
	Retail Banking			314,273		3,351			53,965			318,567			2,841			58,441
	All Other			163,380		(2,027	)		(622	)		109,936			(13,305	)		(31,628	)
	Total		$	1,150,496		—			294,479			1,108,455			—			293,462
			Nine months ended September 30
			2013								2012
			Total		Inter-			Net			Total			Inter-			Net
			revenues(a)		segment			income			revenues(a)			segment			income
					revenues			(loss)						revenues			(loss)
			(in thousands)
	Business Banking		$	319,791		3,750			89,675			335,475			3,202			110,829
	Commercial Banking			760,074		4,048			291,828			741,714			4,832			315,373
	Commercial Real Estate			524,160		2,505			245,826			491,433			5,860			225,025
	Discretionary Portfolio			41,972		(38,200	)		18,992			(11,162	)		(60,990	)		(28,037	)
	Residential Mortgage Banking			324,168		55,528			81,235			341,699			100,350			94,238
	Retail Banking			898,295		10,206			157,815			939,409			8,931			165,289
	All Other			557,244		(37,837	)		31,687			306,632			(62,185	)		(149,412	)
	Total		$	3,425,704		—			917,058			3,145,200			—			733,305
			Average total assets
			Nine months ended					Year ended
			September 30
								December 31
			2013		2012			2012
			(in millions)
	Business Banking		$	5,041		4,918			4,909
	Commercial Banking			21,554		19,691			19,946
	Commercial Real Estate			17,112		16,364			16,437
	Discretionary Portfolio			16,224		16,428			16,583
	Residential Mortgage Banking			2,783		2,316			2,451
	Retail Banking			11,304		11,746			11,705
	All Other			9,082		8,055			7,952
	Total		$	83,100		79,518			79,983
	(a)	Total revenues are comprised of net interest income and other income. Net interest income is the difference between 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 allocation 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 $6,105,000 and $6,534,000 for the three-month periods ended September 30, 2013 and 2012, respectively, and $18,772,000 and $19,884,000 for the nine-month periods ended September 30, 2013 and 2012, respectively, and is eliminated in “All Other” total revenues. Intersegment revenues are included in total revenues of the reportable segments. The elimination of intersegment revenues is included in the determination of “All Other” total revenues.

Relationship_with_Bayview_Lend

Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P.	9 Months Ended
	Sep. 30, 2013
Text Block [Abstract]	'
Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P.	'
	15	Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P.
	M&T holds a 20% interest in Bayview Lending Group LLC (“BLG”), a privately-held commercial mortgage company. M&T recognizes income or loss from BLG using the equity method of accounting. The carrying value of that investment was $80 million at September 30, 2013.
	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 small-balance commercial mortgage loans from BLG and Bayview Financial having outstanding principal balances of $3.4 billion and $3.8 billion at September 30, 2013 and December 31, 2012, respectively. In addition, the Company has servicing rights that were obtained from Bayview Financial related to residential mortgage loans with outstanding principal balances of $2.4 billion at September 30, 2013 and $2.7 billion at December 31, 2012. Revenues from servicing residential and small-balance commercial mortgage loans obtained from BLG and Bayview Financial were $7 million and $9 million during the three months ended September 30, 2013 and 2012, respectively, and $23 million and $27 million for the nine months ended September 30, 2013 and 2012, respectively. The Company sub-services residential mortgage loans for Bayview Financial and affiliates having outstanding principal balances totaling $45.5 billion and $11.4 billion at September 30, 2013 and December 31, 2012, respectively. During the third quarter of 2013, the Company added approximately $35 billion of residential real estate loans to the loans sub-serviced for Bayview Financial and affiliates. Revenues earned for sub-servicing loans for Bayview Financial and affiliates were $8 million and $2 million for the three-month periods ended September 30, 2013 and 2012, respectively, and $12 million and $7 million for the nine-month periods ended September 30, 2013 and 2012, respectively. In addition, at September 30, 2013 and December 31, 2012, the Company held $4 million and $11 million, respectively, of mortgage-backed securities in its available-for-sale investment securities portfolio that were securitized by Bayview Financial. Finally, the Company held $225 million and $242 million of similar investment securities in its held-to-maturity portfolio at September 30, 2013 and December 31, 2012, respectively.

Significant_Accounting_Policie1

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Consolidation	'
	The consolidated financial statements of M&T Bank Corporation (“M&T”) and subsidiaries (“the Company”) were compiled in accordance with generally accepted accounting principles (“GAAP”) using the accounting policies set forth in note 1 of Notes to Financial Statements included in the 2012 Annual Report. In the opinion of management, all adjustments necessary for a fair presentation have been made and were all of a normal recurring nature.

Acquisitions_Tables

Acquisitions (Tables)	9 Months Ended
	Sep. 30, 2013
Business Combinations [Abstract]	'
Summary of Merger-Related Expenses	'
	A summary of merger-related expenses in 2013 associated with the pending Hudson City acquisition and in 2012 associated with the May 16, 2011 acquisition of Wilmington Trust Corporation (“Wilmington Trust”) included in the consolidated statement of income is presented below. There were no merger-related expenses during the three-month periods ended September 30, 2013 or 2012.
		Nine months ended
		September 30,		September 30,
		2013		2012
		(in thousands)
	Salaries and employee benefits	$	836		4,997
	Equipment and net occupancy		690		15
	Printing, postage and supplies		1,825		—
	Other costs of operations		9,013		4,867
		$	12,364		9,879

Investment_Securities_Tables

Investment Securities (Tables)	9 Months Ended
	Sep. 30, 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)
	September 30, 2013
	Investment securities available for sale:
	U.S. Treasury and federal agencies	$	37,432			480			25	$	37,887
	Obligations of states and political subdivisions		17,614			355			6		17,963
	Mortgage-backed securities:
	Government issued or guaranteed		4,214,895			116,758			1,254		4,330,399
	Privately issued		2,789			1,032			5		3,816
	Collateralized debt obligations		42,686			17,724			1,107		59,303
	Other debt securities		137,661			1,758			20,015		119,404
	Equity securities		102,032			22,221			845		123,408
			4,555,109			160,328			23,257		4,692,180
	Investment securities held to maturity:
	Obligations of states and political subdivisions		170,370			4,279			88		174,561
	Mortgage-backed securities:
	Government issued or guaranteed		2,914,687			39,987			29,015		2,925,659
	Privately issued		224,767			—			56,891		167,876
	Other debt securities		9,290			—			—		9,290
			3,319,114			44,266			85,994		3,277,386
	Other securities		298,479			—			—		298,479
	Total	$	8,172,702			204,594			109,251	$	8,268,045
	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
Changes in Credit Losses Associated with Debt Securities for Which OTTI Losses	'
	Changes in credit losses associated with debt securities for which OTTI losses have been recognized in earnings for the three months and nine months ended September 30, 2013 and 2012 follows:
		Three months ended
		September 30
		2013			2012
		(in thousands)
	Beginning balance	$	794			264,197
	Additions for credit losses not previously recognized		—			5,672
	Reductions for realized losses		(626	)		(67,926	)
	Ending balance	$	168			201,943
		Nine months ended
		30-Sep
		2013			2012
		(in thousands)
	Beginning balance	$	197,809			285,399
	Additions for credit losses not previously recognized		9,800			33,331
	Reductions for realized losses		(207,441	)		(116,787	)
	Ending balance	$	168			201,943
Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity	'
	At September 30, 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	$	24,886			24,971
	Due after one year through five years		21,212			22,016
	Due after five years through ten years		8,282			8,553
	Due after ten years		181,013			179,017
			235,393			234,557
	Mortgage-backed securities available for sale		4,217,684			4,334,215
		$	4,453,077			4,568,772
	Debt securities held to maturity:
	Due in one year or less	$	18,617			18,751
	Due after one year through five years		65,392			67,400
	Due after five years through ten years		86,361			88,410
	Due after ten years		9,290			9,290
			179,660			183,851
	Mortgage-backed securities held to maturity		3,139,454			3,093,535
		$	3,319,114			3,277,386
Investment Securities in Continuous Unrealized Loss Position	'
	A summary of investment securities that as of September 30, 2013 and December 31, 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)
	September 30, 2013
	Investment securities available for sale:
	U.S. Treasury and federal agencies	$	6,346			(25	)		—		—
	Obligations of states and political subdivisions		577			(2	)		559		(4	)
	Mortgage-backed securities:
	Government issued or guaranteed		174,503			(1,126	)		5,731		(128	)
	Privately issued		—			—			107		(5	)
	Collateralized debt obligations		—			—			5,995		(1,107	)
	Other debt securities		1,576			(7	)		102,898		(20,008	)
	Equity securities		2,777			(845	)		—		—
			185,779			(2,005	)		115,290		(21,252	)
	Investment securities held to maturity:
	Obligations of states and political subdivisions		14,751			(70	)		1,558		(18	)
	Mortgage-backed securities:
	Government issued or guaranteed		1,259,353			(29,015	)		—		—
	Privately issued		—			—			167,876		(56,891	)
			1,274,104			(29,085	)		169,434		(56,909	)
	Total	$	1,459,883			(31,090	)		284,724		(78,161	)
		Less than 12 months						12 months or more
		Fair value			Unrealized			Fair value		Unrealized
					losses					losses
		(in thousands)
	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_and_the_Allow1

Loans and Leases and the Allowance for Credit Losses (Tables)	9 Months Ended
	Sep. 30, 2013
Receivables [Abstract]	'
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 is as follows:
			September 30,			December 31,
			2013			2012
			(in thousands)
	Outstanding principal balance		$	5,274,466			6,705,120
	Carrying amount:
	Commercial, financial, leasing, etc.			730,743			928,107
	Commercial real estate			1,875,842			2,567,050
	Residential real estate			598,820			707,309
	Consumer			1,357,847			1,637,887
			$	4,563,252			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 three months and nine months ended September 30, 2013 and 2012 follows:
			Three months ended September 30
			2013						2012
			Purchased			Other			Purchased			Other
			impaired			acquired			impaired			acquired
			(in thousands)
	Balance at beginning of period		$	55,149			622,093		$	55,599			733,161
	Interest income			(10,428	)		(60,786	)		(12,436	)		(74,936	)
	Reclassifications from nonaccretable balance, net			172			—			542			—
	Other (a)			—			6,254			—			1,382
	Balance at end of period		$	44,893			567,561		$	43,705			659,607
			Nine months ended September 30
			2013						2012
			Purchased			Other			Purchased			Other
			impaired			acquired			impaired			acquired
			(in thousands)
	Balance at beginning of period		$	42,252			638,272		$	30,805			807,960
	Interest income			(28,879	)		(190,072	)		(29,721	)		(228,908	)
	Reclassifications from nonaccretable balance, net			31,520			122,519			42,621			98,165
	Other (a)			—			(3,158	)		—			(17,610	)
	Balance at end of period		$	44,893			567,561		$	43,705			659,607
	(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 September 30, 2013 and December 31, 2012 were as follows:
									90 Days or
									more past
									due and accruing
			Current			30-89			Non-			Acquired			Purchased			Nonaccrual			Total
						Days			acquired			(a)			impaired
						past due									(b)
									(in thousands)
	September 30, 2013
	Commercial, financial, leasing, etc.		$	17,678,290			91,757			2,582			11,147			16,257			111,116			17,911,149
	Real estate:
	Commercial			21,447,385			179,972			12,859			50,853			101,049			198,397			21,990,515
	Residential builder and developer			921,728			10,622			52			12,353			138,651			113,096			1,196,502
	Other commercial construction			3,029,504			16,903			1,888			5,090			68,539			36,326			3,158,250
	Residential			7,884,094			301,564			317,660			44,489			30,201			252,987			8,830,995
	Residential Alt-A			297,840			18,263			—			—			—			80,905			397,008
	Consumer:
	Home equity lines and loans			6,027,315			32,428			—			29,472			2,640			77,537			6,169,392
	Automobile			1,144,216			39,221			—			181			—			22,087			1,205,705
	Other			2,736,469			34,886			4,751			—			—			23,420			2,799,526
	Total		$	61,166,841			725,616			339,792			153,585			357,337			915,871			63,659,042
									90 Days or
									more past
									due and accruing
			Current			30-89			Non-			Acquired			Purchased			Nonaccrual			Total
						Days			acquired			(a)			impaired
						past due									(b)
			(in thousands)
	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.
Changes in Allowance for Credit Losses	'
	Changes in the allowance for credit losses for the three months ended September 30, 2013 were as follows:
			Commercial,			Real Estate
			Financial,
			Leasing, etc.			Commercial			Residential			Consumer			Unallocated			Total
			(in thousands)
	Beginning balance		$	268,867			324,264			85,311			174,291			74,332		$	927,065
	Provision for credit losses			20,209			12,139			315			14,935			402			48,000
	Allowance related to loans securitized and sold			—			—			—			(11,000	)		—			(11,000	)
	Net charge-offs
	Charge-offs			(30,931	)		(7,701	)		(5,320	)		(20,242	)		—			(64,194	)
	Recoveries			5,150			4,751			2,399			4,199			—			16,499
	Net charge-offs			(25,781	)		(2,950	)		(2,921	)		(16,043	)		—			(47,695	)
	Ending balance		$	263,295			333,453			82,705			162,183			74,734		$	916,370
	Changes in the allowance for credit losses for the three months ended September 30, 2012 were as follows:
			Commercial,			Real Estate
			Financial,
			Leasing, etc.			Commercial			Residential			Consumer			Unallocated			Total
			(in thousands)
	Beginning balance		$	244,728			341,521			93,269			164,352			73,158		$	917,028
	Provision for credit losses			439			9,891			8,247			26,962			461			46,000
	Net charge-offs
	Charge-offs			(8,874	)		(7,982	)		(8,687	)		(24,553	)		—			(50,096	)
	Recoveries			1,174			1,421			1,139			4,557			—			8,291
	Net charge-offs			(7,700	)		(6,561	)		(7,548	)		(19,996	)		—			(41,805	)
	Ending balance		$	237,467			344,851			93,968			171,318			73,619		$	921,223
	Changes in the allowance for credit losses for the nine months ended September 30, 2013 were as follows:
			Commercial,			Real Estate
			Financial,
			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			93,736			914			3,913			43,478			959			143,000
	Allowance related to loans securitized and sold			—			—			—			(11,000	)		—			(11,000	)
	Net charge-offs
	Charge-offs			(86,787	)		(21,493	)		(18,583	)		(62,905	)		—			(189,768	)
	Recoveries			9,587			16,931			8,568			13,192			—			48,278
	Net charge-offs			(77,200	)		(4,562	)		(10,015	)		(49,713	)		—			(141,490	)
	Ending balance		$	263,295			333,453			82,705			162,183			74,734		$	916,370
	Changes in the allowance for credit losses for the nine months ended September 30, 2012 were as follows:
			Commercial,			Real Estate
			Financial,
			Leasing, etc.			Commercial			Residential			Consumer			Unallocated			Total
			(in thousands)
	Beginning balance		$	234,022			367,637			91,915			143,121			71,595		$	908,290
	Provision for credit losses			29,663			4,322			30,064			88,927			2,024			155,000
	Net charge-offs
	Charge-offs			(32,989	)		(31,578	)		(32,812	)		(77,155	)		—			(174,534	)
	Recoveries			6,771			4,470			4,801			16,425			—			32,467
	Net charge-offs			(26,218	)		(27,108	)		(28,011	)		(60,730	)		—			(142,067	)
	Ending balance		$	237,467			344,851			93,968			171,318			73,619		$	921,223
Impaired Loans and Leases	'
	The following tables provide information with respect to loans and leases that were considered impaired as of September 30, 2013 and December 31, 2012 and for the three months and nine months ended September 30, 2013 and September 30, 2012.
			September 30, 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.		$	93,568			114,572			25,530			127,282			149,534			33,829
	Real estate:
	Commercial			127,921			152,885			24,104			121,542			143,846			23,641
	Residential builder and developer			61,947			102,395			7,374			115,306			216,218			25,661
	Other commercial construction			74,116			77,180			3,104			73,544			76,869			6,836
	Residential			100,287			118,572			6,537			103,451			121,819			3,521
	Residential Alt-A			115,695			128,446			15,000			128,891			141,940			17,000
	Consumer:
	Home equity lines and loans			13,258			14,372			3,408			12,360			13,567			2,254
	Automobile			42,106			42,106			12,060			49,210			49,210			14,273
	Other			16,057			16,057			4,169			14,408			14,408			5,667
				644,955			766,585			101,286			745,994			927,411			132,682
	With no related allowance recorded:
	Commercial, financial, leasing, etc.			24,945			30,551			—			32,631			42,199			—
	Real estate:
	Commercial			77,284			99,461			—			78,380			100,337			—
	Residential builder and developer			56,015			84,852			—			74,307			105,438			—
	Other commercial construction			19,960			24,051			—			23,018			23,532			—
	Residential			83,041			93,898			—			86,342			96,448			—
	Residential Alt-A			28,397			52,565			—			31,354			58,768			—
				289,642			385,378			—			326,032			426,722			—
	Total:
	Commercial, financial, leasing, etc.			118,513			145,123			25,530			159,913			191,733			33,829
	Real estate:
	Commercial			205,205			252,346			24,104			199,922			244,183			23,641
	Residential builder and developer			117,962			187,247			7,374			189,613			321,656			25,661
	Other commercial construction			94,076			101,231			3,104			96,562			100,401			6,836
	Residential			183,328			212,470			6,537			189,793			218,267			3,521
	Residential Alt-A			144,092			181,011			15,000			160,245			200,708			17,000
	Consumer:
	Home equity lines and loans			13,258			14,372			3,408			12,360			13,567			2,254
	Automobile			42,106			42,106			12,060			49,210			49,210			14,273
	Other			16,057			16,057			4,169			14,408			14,408			5,667
	Total		$	934,597			1,151,963			101,286			1,072,026			1,354,133			132,682
Interest Income Recognized on Loans	'
	Three months ended										Three months ended
	September 30, 2013										September 30, 2012
						Interest income									Interest income
						recognized									recognized
			Average			Total			Cash			Average			Total			Cash
			recorded						basis			recorded						basis
			investment									investment
			(in thousands)
	Commercial, financial, leasing, etc.		$	149,357			516			516			141,166			1,507			1,507
	Real estate:
	Commercial			205,971			716			716			180,009			531			531
	Residential builder and developer			130,855			213			188			237,847			476			370
	Other commercial construction			95,486			208			208			84,604			9			9
	Residential			180,995			1,391			865			131,114			1,269			765
	Residential Alt-A			147,056			1,763			692			167,780			1,836			593
	Consumer:
	Home equity lines and loans			12,810			167			49			11,949			172			48
	Automobile			42,957			710			127			51,138			863			185
	Other			15,791			161			50			11,996			121			52
	Total		$	981,278			5,845			3,411			1,017,603			6,784			4,060
			Nine months ended									Nine months ended
			September 30, 2013									September 30, 2012
						Interest income									Interest income
						recognized									recognized
			Average			Total			Cash			Average			Total			Cash
			recorded						basis			recorded						basis
			investment									investment
			(in thousands)
	Commercial, financial, leasing, etc.		$	164,877			6,358			6,358			155,627			2,659			2,659
	Real estate:
	Commercial			200,354			1,428			1,428			179,524			2,087			2,087
	Residential builder and developer			159,308			871			637			260,858			1,202			801
	Other commercial construction			97,268			3,322			3,322			100,242			5,019			5,019
	Residential			184,719			4,795			3,188			128,646			3,926			2,453
	Residential Alt-A			151,992			5,173			1,799			174,390			5,432			1,666
	Consumer:
	Home equity lines and loans			12,633			499			127			11,024			502			136
	Automobile			45,075			2,226			404			52,249			2,632			553
	Other			15,438			468			153			10,097			320			138
	Total		$	1,031,664			25,140			17,416			1,072,657			23,779			15,512
Summary of Loan Grades	'
	The following table summarizes the loan grades applied to the various classes of the Company’s commercial and commercial real estate loans.
						Real Estate
			Commercial,			Commercial			Residential			Other
			Financial,						Builder and			Commercial
			Leasing, etc.						Developer			Construction
			(in thousands)
	September 30, 2013
	Pass		$	17,022,772			20,978,696			1,005,932			3,066,941
	Criticized accrual			777,261			813,422			77,474			54,983
	Criticized nonaccrual			111,116			198,397			113,096			36,326
	Total		$	17,911,149			21,990,515			1,196,502			3,158,250
	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)
	September 30, 2013
	Individually evaluated for impairment		$	25,530			34,139			21,517			19,637		$	100,823
	Collectively evaluated for impairment			234,912			298,579			59,645			141,202			734,338
	Purchased impaired			2,853			735			1,543			1,344			6,475
	Allocated		$	263,295			333,453			82,705			162,183			841,636
	Unallocated															74,734
	Total														$	916,370
	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)
	September 30, 2013
	Individually evaluated for impairment		$	118,513			413,443			326,860			71,421		$	930,237
	Collectively evaluated for impairment			17,776,379			25,623,585			8,870,942			10,100,562			62,371,468
	Purchased impaired			16,257			308,239			30,201			2,640			357,337
	Total		$	17,911,149			26,345,267			9,228,003			10,174,623		$	63,659,042
	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
Loan Modification Activities that were Considered Troubled Debt Restructurings	'
	The tables below summarize the Company’s loan modification activities that were considered troubled debt restructurings for the three months ended September 30, 2013 and 2012:
						Recorded investment						Financial effects of modification
	Three months ended September 30, 2013		Number			Pre-modification			Post-modification			Recorded			Interest (b)
												investment (a)
						(dollars in thousands)
	Commercial, financial, leasing, etc.
	Principal deferral			14		$	2,407		$	2,266		$	(141	)	$	—
	Other			2			1,773			2,067			294			—
	Combination of concession types			3			374			374			—			(25	)
	Real estate:
	Commercial
	Principal deferral			10			4,160			4,134			(26	)		—
	Other			2			449			475			26			—
	Combination of concession types			6			1,868			2,264			396			(156	)
	Residential builder and developer
	Principal deferral			1			249			241			(8	)		—
	Other commercial construction
	Principal deferral			1			226			158			(68	)		—
	Residential
	Principal deferral			6			860			912			52			—
	Combination of concession types			14			1,258			1,308			50			(197	)
	Residential Alt-A
	Principal deferral			5			764			773			9			—
	Combination of concession types			4			332			496			164			(252	)
	Consumer:
	Home equity lines and loans
	Principal deferral			2			179			179			—			—
	Combination of concession types			9			682			682			—			(79	)
	Automobile
	Principal deferral			121			1,718			1,718			—			—
	Interest rate reduction			2			19			19			—			(2	)
	Other			20			42			42			—			—
	Combination of concession types			61			551			551			—			(33	)
	Other
	Principal deferral			9			60			60			—			—
	Combination of concession types			18			470			470			—			(86	)
	Total			310		$	18,441		$	19,189		$	748		$	(830	)
	(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.
						Recorded investment						Financial effects of modification
	Three months ended September 30, 2012		Number			Pre-modification			Post-modification			Recorded			Interest (b)
												investment (a)
						(dollars in thousands)
	Commercial, financial, leasing, etc.
	Principal deferral			21		$	7,823		$	7,653		$	(170	)	$	—
	Combination of concession types			2			327			322			(5	)		(39	)
	Real estate:
	Commercial
	Principal deferral			8			5,951			6,238			287			—
	Combination of concession types			1			214			214			—			(49	)
	Residential builder and developer
	Principal deferral			11			17,383			16,275			(1,108	)		—
	Combination of concession types			1			2,486			2,486			—			—
	Other commercial construction
	Principal deferral			2			5,429			4,702			(727	)		—
	Residential
	Principal deferral			5			738			772			34			—
	Combination of concession types			18			5,490			5,553			63			(150	)
	Residential Alt-A
	Principal deferral			1			218			220			2			—
	Combination of concession types			13			2,771			2,795			24			—
	Consumer:
	Home equity lines and loans
Principal deferral			5			434			434			—			—
Combination of concession types			11			976			976			—			(125	)
Automobile
Principal deferral			135			1,721			1,721			—			—
Interest rate reduction			9			157			157			—			(11	)
Other			20			68			68			—			—
Combination of concession types			109			2,329			2,329			—			(319	)
Other
Principal deferral			14			336			336			—			—
Other			1			1			1			—			—
Combination of concession types			22			339			339			—			(97	)
Total			409		$	55,191		$	53,591		$	(1,600	)	$	(790	)
(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 tables below summarize the Company’s loan modification activities that were considered troubled debt restructurings for the nine months ended September 30, 2013 and 2012:
					Recorded investment						Financial effects of modification
Nine months ended September 30, 2013		Number			Pre-modification			Post-modification			Recorded			Interest (b)
											investment (a)
					(dollars in thousands)
Commercial, financial, leasing, etc.
Principal deferral			53		$	9,283		$	9,070		$	(213	)	$	—
Other			4			50,433			50,924			491			—
Combination of concession types			6			2,206			1,696			(510	)		(25	)
Real estate:
Commercial
Principal deferral			23			38,187			38,027			(160	)		—
Other			2			449			475			26			—
Combination of concession types			8			2,450			2,845			395			(212	)
Residential builder and developer
Principal deferral			16			19,102			18,303			(799	)		—
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			21			2,642			2,877			235			—
Other			1			195			195			—			—
Combination of concession types			52			72,917			69,734			(3,183	)		(754	)
Residential Alt-A
Principal deferral			6			863			875			12			—
Combination of concession types			17			2,426			2,715			289			(640	)
Consumer:
Home equity lines and loans
Principal deferral			6			359			361			2			—
Interest rate reduction			1			99			99			—			(8	)
Other			1			106			106			—			—
Combination of concession types			19			1,299			1,299			—			(176	)
Automobile
Principal deferral			359			4,933			4,933			—			—
Interest rate reduction			11			159			159			—			(17	)
Other			65			274			274			—			—
Combination of concession types			184			2,148			2,148			—			(162	)
Other
Principal deferral			29			290			290			—			—
Interest rate reduction			1			12			12			—			(2	)
Other			1			12			12			—			—
Combination of concession types			90			2,394			2,394			—			(587	)
Total			983		$	233,447		$	229,746		$	(3,701	)	$	(3,118	)
(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.
					Recorded investment						Financial effects of modification
Nine months ended September 30, 2012		Number			Pre-modification			Post-modification			Recorded			Interest (b)
											investment (a)
					(dollars in thousands)
Commercial, financial, leasing, etc.
Principal deferral			39		$	21,027		$	19,668		$	(1,359	)	$	—
Other			3			2,967			3,052			85			—
Combination of concession types			3			372			366			(6	)		(72	)
Real estate:
Commercial
Principal deferral			11			10,387			10,642			255			—
Interest rate reduction			1			383			430			47			(89	)
Combination of concession types			5			1,424			1,445			21			(305	)
Residential builder and developer
Principal deferral			19			26,708			24,812			(1,896	)		—
Combination of concession types			3			4,836			5,212			376			—
Other commercial construction
Principal deferral			5			66,317			65,600			(717	)		—
Residential
Principal deferral			27			3,302			3,447			145			—
Combination of concession types			47			10,475			10,658			183			(415	)
Residential Alt-A
Principal deferral			5			768			785			17			—
Combination of concession types			28			5,640			5,732			92			(49	)
Consumer:
Home equity lines and loans
Principal deferral			15			1,285			1,285			—			—
Interest rate reduction			1			144			144			—			(6	)
Combination of concession types			17			1,691			1,691			—			(272	)
Automobile
Principal deferral			484			6,306			6,306			—			—
Interest rate reduction			16			234			234			—			(16	)
Other			51			239			239			—			—
Combination of concession types			298			5,108			5,108			—			(601	)
Other
Principal deferral			73			1,117			1,117			—			—
Interest rate reduction			3			23			23			—			(3	)
Other			10			50			50			—			—
Combination of concession types			74			700			700			—			(155	)
Total			1,238		$	171,503		$	168,746		$	(2,757	)	$	(1,983	)
(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.

Shareholders_Equity_Tables

Shareholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]	'
Issued and Outstanding Preferred Stock	'
	Issued and outstanding preferred stock of M&T is presented below:
			Shares		Carrying		Carrying
			issued and		value		value
			outstanding		September 30, 2013		December 31, 2012
					(dollars in thousands)
	Series A (a)
	Fixed Rate Cumulative Perpetual Preferred Stock, Series A, $1,000 liquidation preference per share			230,000	$	229,236	$	226,965
	Series C (a)(b)
	Fixed Rate Cumulative Perpetual Preferred Stock, Series C, $1,000 liquidation preference per share			151,500		149,774		145,535
	Series D (c)
	Fixed Rate Non-Cumulative Perpetual Preferred Stock, Series D, $10,000 liquidation preference per share			50,000		500,000		500,000
	(a)	Shares were originally issued as part of the Troubled Asset Relief Program – Capital Purchase Program (“TARP”) of the U.S. Department of Treasury (“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, will accrue and be paid quarterly at a rate of 5% per year through November 14, 2013 and at 6.375% thereafter, and that M&T will 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 the third quarter of 2013, 57,327 of the Series A warrants were exercised in a “cashless” exercise, resulting in the issuance of 21,130 common shares. Remaining outstanding Series A warrants were 1,161,195 at September 30, 2013.
	(b)	Shares were assumed in an acquisition and a new Series C Preferred Stock was designated.
	(c)	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.

Pension_Plans_and_Other_Postre1

Pension Plans and Other Postretirement Benefits (Tables)	9 Months Ended
	Sep. 30, 2013
Compensation And Retirement Disclosure [Abstract]	'
Net Periodic Benefit Cost for Defined Benefit Plans	'
	Net periodic defined benefit cost for defined benefit plans consisted of the following:
		Pension						Other
		benefits						postretirement
								benefits
		Three months ended September 30
		2013			2012			2013			2012
		(in thousands)
	Service cost	$	6,090			7,387			186			167
	Interest cost on projected benefit obligation		15,032			15,509			673			934
	Expected return on plan assets		(21,838	)		(17,627	)		—			—
	Amortization of prior service cost		(1,639	)		(1,640	)		(340	)		5
	Amortization of net actuarial loss		10,269			9,291			90			133
	Net periodic benefit cost	$	7,914			12,920			609			1,239
		Pension						Other
		benefits						postretirement
								benefits
		Nine months ended September 30
		2013			2012			2013			2012
		(in thousands)
	Service cost	$	18,270			22,162			557			501
	Interest cost on projected benefit obligation		45,097			46,527			2,018			2,803
	Expected return on plan assets		(65,515	)		(52,883	)		—			—
	Amortization of prior service cost		(4,917	)		(4,919	)		(1,019	)		15
	Amortization of net actuarial loss		30,807			27,874			270			398
	Net periodic benefit cost	$	23,742			38,761			1,826			3,717

Earnings_Per_Common_Share_Tabl

Earnings Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]	'
Computations of Basic Earnings Per Common Share	'
	The computations of basic earnings per common share follow:
			Three months ended						Nine months ended
			September 30						September 30
			2013			2012			2013			2012
			(in thousands, except per share)
	Income available to common shareholders:
	Net income		$	294,479			293,462		$	917,058			733,305
	Less: Preferred stock dividends (a)			(13,363	)		(13,363	)		(40,088	)		(40,088	)
	Amortization of preferred stock discount (a)			(2,235	)		(2,033	)		(6,575	)		(5,921	)
	Net income available to common equity			278,881			278,066			870,395			687,296
	Less: Income attributable to unvested stock-based compensation awards			(3,545	)		(4,181	)		(11,451	)		(10,475	)
	Net income available to common shareholders		$	275,336			273,885		$	858,944			676,821
	Weighted-average shares outstanding:
	Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards			130,836			127,741			130,088			127,449
	Less: Unvested stock-based compensation awards			(1,665	)		(1,923	)		(1,719	)		(1,939	)
	Weighted-average shares outstanding			129,171			125,818			128,369			125,510
	Basic earnings per common share		$	2.13			2.18		$	6.69			5.39
	(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:
			Three months ended						Nine months ended
			September 30						September 30
			2013			2012			2013			2012
			(in thousands, except per share)
	Net income available to common equity		$	278,881			278,066		$	870,395			687,296
	Less: Income attributable to unvested stock-based compensation awards			(3,525	)		(4,170	)		(11,395	)		(10,454	)
	Net income available to common shareholders		$	275,356			273,896		$	859,000			676,842
	Adjusted weighted-average shares outstanding:
	Common and unvested stock-based compensation awards			130,836			127,741			130,088			127,449
	Less: Unvested stock-based compensation awards			(1,665	)		(1,923	)		(1,719	)		(1,939	)
	Plus: Incremental shares from assumed conversion of stock-based compensation awards and warrants to purchase common stock			1,094			474			943			426
	Adjusted weighted-average shares outstanding			130,265			126,292			129,312			125,936
	Diluted earnings per common share		$	2.11			2.17		$	6.64			5.37

Comprehensive_Income_Tables

Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]	'
Components of Other Comprehensive Income (Loss) and Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	'
	The following table displays the components of other comprehensive income (loss) and amounts reclassified from accumulated other comprehensive income (loss) to net income:
			Investment Securities
			With			All			Defined			Other			Total			Income			Net
			OTTI			other			benefit						amount			tax
									plans						before tax
			(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			59,523			(61,706	)		—			—			(2,183	)		814			(1,369	)
	Foreign currency translation adjustment			—			—			—			296			296			(91	)		205
	Total other comprehensive income before reclassifications			59,523			(61,706	)		—			296			(1,887	)		723			(1,164	)
	Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income:
	Accretion of unrealized holding losses on held-to-maturity (“HTM”) securities			230			3,127			—			—			3,357	(a)		(1,318	)		2,039
	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			—			—			(5,936	)		—			(5,936	) (e)		2,330			(3,606	)
	Amortization of actuarial losses			—			—			31,077			—			31,077	(e)		(12,198	)		18,879
	Total reclassifications			51,247			(5,002	)		25,141			—			71,386			(28,020	)		43,366
	Total gain (loss) during the period			110,770			(66,708	)		25,141			296			69,499			(27,297	)		42,202
	Balance – September 30, 2013		$	18,935			85,491			(430,449	)		(135	)	$	(326,158	)		128,096		$	(198,062	)
			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			(8,099	)		153,908			—			—			145,809			(57,183	)		88,626
	Foreign currency translation adjustment			—			—			—			552			552			(201	)		351
	Total other comprehensive income before reclassifications			(8,099	)		153,908			—			552			146,361			(57,384	)		88,977
	Amounts reclassified from accumulated other comprehensive income that (increase) decrease net income:
	Accretion of unrealized holding losses on HTM securities			1,544			3,495			—			—			5,039	(a)		(1,978	)		3,061
	OTTI charges recognized in net income			33,331			—			—			—			33,331	(b)		(13,082	)		20,249
	Gains realized in net income			—			(9	)		—			—			(9	) (c)		4			(5	)
	Amortization of gains on terminated cash flow hedges			—			—			—			(178	)		(178	) (d)		66			(112	)
	Amortization of prior service credit			—			—			(4,904	)		—			(4,904	) (e)		1,925			(2,979	)
	Amortization of actuarial losses			—			—			28,272			—			28,272	(e)		(11,097	)		17,175
	Total reclassifications			34,875			3,486			23,368			(178	)		61,551			(24,162	)		37,389
	Total gain (loss) during the period			26,776			157,394			23,368			374			207,912			(81,546	)		126,366
	Balance – September 30,2012		$	(111,543	)		167,151			(433,777	)		(688	)	$	(378,857	)		148,782		$	(230,075	)
	(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 the following:
			Investment securities						Defined			Other			Total
									benefit
			With			All			plans
			OTTI			other
	Balance – December 31, 2012		$	(55,790	)		92,581			(276,771	)		(284	)	$	(240,264	)
	Net gain (loss) during period			67,293			(40,569	)		15,273			205			42,202
	Balance – September 30, 2013		$	11,503			52,012			(261,498	)		(79	)	$	(198,062	)

Derivative_Financial_Instrumen1

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 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-
			amount			maturity			average rate
									Fixed			Variable
			(in thousands)			(in years)
	September 30, 2013
	Fair value hedges:
	Fixed rate long-term borrowings (a)		$	1,400,000			3.9			4.42	%		1.22	%
	December 31, 2012
	Fair value hedges:
	Fixed rate long-term borrowings (a)		$	900,000			4.4			6.07	%		1.85	%
	(a)	Under the terms of these agreements, the Company receives settlement amounts at a fixed rate and pays at a variable rate.
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
			September 30,			December 31,			September 30,			December 31,
			2013			2012			2013			2012
			(in thousands)
	Derivatives designated and qualifying as hedging instruments
	Fair value hedges:
	Interest rate swap agreements (a)		$	114,083			143,179		$	—			—
	Commitments to sell real estate loans (a)			2,477			1,114			11,665			3,825
				116,560			144,293			11,665			3,825
	Derivatives not designated and qualifying as hedging instruments
	Mortgage-related commitments to originate real estate loans for sale (a)			18,185			48,056			5,110			197
	Commitments to sell real estate loans (a)			6,880			1,982			7,435			6,570
	Trading:
	Interest rate contracts (b)			285,442			399,963			248,311			365,616
	Foreign exchange and other option and futures contracts (b)			13,451			8,725			13,138			8,658
				323,958			458,726			273,994			381,041
	Total derivatives		$	440,518			603,019		$	285,659			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
			Three months ended						Three months ended
			September 30, 2013						September 30, 2012
			Derivative			Hedged item			Derivative			Hedged item
			(in thousands)
	Derivatives in fair value hedging relationships
	Interest rate swap agreements:
	Fixed rate long-term borrowings (a)		$	(86	)		(20	)	$	3,273			(3,252	)
	Derivatives not designated as hedging instruments
	Trading:
	Interest rate contracts (b)		$	2,778					$	777
	Foreign exchange and other option and futures contracts (b)			(862	)					74
	Total		$	1,916					$	851
			Amount of unrealized gain (loss) recognized
			Nine months ended						Nine months ended
			September 30, 2013						30-Sep-12
			Derivative			Hedged item			Derivative			Hedged item
			(in thousands)
	Derivatives in fair value hedging relationships
	Interest rate swap agreements:
	Fixed rate long-term borrowings (a)		$	(29,097	)		27,733		$	5,918			(5,876	)
	Derivatives not designated as hedging instruments
	Trading:
	Interest rate contracts (b)		$	5,974					$	3,996
	Foreign exchange and other option and futures contracts (b)			(2,469	)					(3,071	)
	Total		$	3,505					$	925
	(a)	Reported as other revenues from operations.
	(b)	Reported as trading account and foreign exchange gains.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Assets and Liabilities Measured at Estimated Fair Value on Recurring Basis	'
	The following tables present assets and liabilities at September 30, 2013 and December 31, 2012 measured at estimated fair value on a recurring basis:
			Fair value			Level 1 (a)			Level 2 (a)			Level 3
			measurements at
			September 30,
			2013
			(in thousands)
	Trading account assets		$	371,370			48,344			323,026			—
	Investment securities available for sale:
	U.S. Treasury and federal agencies			37,887			—			37,887			—
	Obligations of states and political subdivisions			17,963			—			17,963			—
	Mortgage-backed securities:
	Government issued or guaranteed			4,330,399			—			4,330,399			—
	Privately issued			3,816			—			—			3,816
	Collateralized debt obligations			59,303			—			—			59,303
	Other debt securities			119,404			—			119,404			—
	Equity securities			123,408			91,075			32,333			—
				4,692,180			91,075			4,537,986			63,119
	Real estate loans held for sale			819,029			—			819,029			—
	Other assets (b)			141,625			—			123,440			18,185
	Total assets		$	6,024,204			139,419			5,803,481			81,304
	Trading account liabilities		$	261,449			—			261,449			—
	Other liabilities (b)			24,210			—			19,100			5,110
	Total liabilities		$	285,659			—			280,549			5,110
			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 three months and nine months ended September 30, 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 a Recurring Basis	'
	The changes in Level 3 assets and liabilities measured at estimated fair value on a recurring basis during the three months ended September 30, 2013 were as follows:
			Investment securities available for sale
			Privately issued			Collateralized			Other assets
			mortgage-backed			debt			and other
			securities			obligations			liabilities
			(in thousands)
	Balance – June 30, 2013		$	5,272		$	59,916		$	7,408
	Total gains (losses) realized/unrealized:
	Included in earnings			—			—			24,440	(b)
	Included in other comprehensive income			400	(e)		213	(e)		—
	Settlements			(1,856	)		(826	)		—
	Transfers in and/or out of Level 3 (c)			—			—			(18,773	)(d)
	Balance – September 30, 2013		$	3,816		$	59,303		$	13,075
	Changes in unrealized gains (losses) included in earnings related to assets still held at September 30, 2013		$	—		$	—		$	(1,727	)(b)
	The changes in Level 3 assets and liabilities measured at estimated fair value on a recurring basis during the three months ended September 30, 2012 were as follows:
			Investment securities available for sale
			Privately issued			Collateralized			Other assets
			mortgage-backed			debt			and other
			securities			obligations			liabilities
			(in thousands)
	Balance – June 30, 2012		$	1,080,519		$	55,098		$	34,051
	Total gains (losses) realized/unrealized:
	Included in earnings			(5,672	)(a)		—			84,864	(b)
	Included in other comprehensive income			40,603	(e)		3,297	(e)		—
	Settlements			(49,814	)		(1,194	)		—
	Transfers in and/or out of Level 3 (c)			—			—			(48,570	)(d)
	Balance – September 30, 2012		$	1,065,636		$	57,201		$	70,345
	Changes in unrealized gains (losses) included in earnings related to assets still held at September 30, 2012		$	(5,672	)(a)	$	—		$	63,357	(b)
	The changes in Level 3 assets and liabilities measured at estimated fair value on a recurring basis during the nine months ended September 30, 2013 were as follows:
			Investment securities available for sale
			Privately issued			Collateralized			Other assets
			mortgage-backed			debt			and other
			securities			obligations			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)		—			83,252	(b)
	Included in other comprehensive income			116,984	(e)		(324	)(e)		—
	Sales			(978,608	)		—			—
	Settlements			(102,344	)		(2,242	)		—
	Transfers in and/or out of Level 3 (c)			—			—			(118,036	)(d)
	Balance – September 30, 2013		$	3,816		$	59,303		$	13,075
	Changes in unrealized gains included in earnings related to assets still held at September 30, 2013		$	—		$	—		$	925	(b)
	The changes in Level 3 assets and liabilities measured at estimated fair value on a recurring basis during the nine months ended September 30, 2012 were as follows:
			Investment securities available for sale
			Privately issued			Collateralized			Other assets
			mortgage-backed			debt			and other
			securities			obligations			liabilities
			(in thousands)
	Balance – January 1, 2012		$	1,151,285		$	52,500		$	6,923
	Total gains (losses) realized/unrealized:
	Included in earnings			(27,976	)(a)		—			157,381	(b)
	Included in other comprehensive income			89,397	(e)		7,008	(e)		—
	Settlements			(147,070	)		(2,307	)		—
	Transfers in and/or out of Level 3 (c)			—			—			(93,959	)(d)
	Balance – September 30, 2012		$	1,065,636		$	57,201		$	70,345
	Changes in unrealized gains (losses) included in earnings related to assets still held at September 30, 2012		$	(27,976	)(a)	$	—		$	70,187	(b)
	(a)	Reported as an OTTI 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 tables present quantitative information about significant unobservable inputs used in the fair value measurements for Level 3 assets and liabilities at September 30, 2013 and December 31, 2012.
			Fair value at			Valuation		Unobservable	Range
			September 30, 2013						(weighted-
						technique		input/assumptions	average)
			(in thousands)
	Recurring fair value measurements
	Privately issued mortgage–backed securities		$	3,816		Two independent price quotes		—	—
	Collateralized debt obligations			59,303		Discounted cash flow		Probability of default	13%-55% (39%)
								Loss severity	100%
	Net other assets (liabilities)(a)			13,075		Discounted cash flow		Commitment expirations	0%-91% (21%)
			Fair value at			Valuation		Unobservable	Range
			December 31, 2012						(weighted-
						technique		input/assumptions	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:
			September 30, 2013
			Carrying			Estimated			Level 1			Level 2			Level 3
			amount			fair value
			(in thousands)
	Financial assets:
	Cash and cash equivalents		$	2,059,753		$	2,059,753		$	1,992,949		$	66,804		$	—
	Interest-bearing deposits at banks			1,925,811			1,925,811			—			1,925,811			—
	Trading account assets			371,370			371,370			48,344			323,026			—
	Investment securities			8,309,773			8,268,045			91,075			7,945,975			230,995
	Loans and leases:
	Commercial loans and leases			17,911,149			17,685,646			—			—			17,685,646
	Commercial real estate loans			26,345,267			26,256,932			—			151,690			26,105,242
	Residential real estate loans			9,228,003			9,198,681			—			5,757,491			3,441,190
	Consumer loans			10,174,623			10,151,004			—			—			10,151,004
	Allowance for credit losses			(916,370	)		—			—			—			—
	Loans and leases, net			62,742,672			63,292,263			—			5,909,181			57,383,082
	Accrued interest receivable			234,208			234,208			—			234,208			—
	Financial liabilities:
	Noninterest-bearing deposits		$	(24,150,771	)	$	(24,150,771	)	$	—		$	(24,150,771	)	$	—
	Savings deposits and NOW accounts			(38,253,417	)		(38,253,417	)		—			(38,253,417	)		—
	Time deposits			(3,831,443	)		(3,853,552	)		—			(3,853,552	)		—
	Deposits at Cayman Islands office			(316,510	)		(316,510	)		—			(316,510	)		—
	Short-term borrowings			(246,019	)		(246,019	)		—			(246,019	)		—
	Long-term borrowings			(5,121,326	)		(5,257,947	)		—			(5,257,947	)		—
	Accrued interest payable			(62,773	)		(62,773	)		—			(62,773	)		—
	Trading account liabilities			(261,449	)		(261,449	)		—			(261,449	)		—
	Other financial instruments:
	Commitments to originate real estate loans for sale		$	13,075		$	13,075		$	—		$	—		$	13,075
	Commitments to sell real estate loans			(9,743	)		(9,743	)		—			(9,743	)		—
	Other credit-related commitments			(114,048	)		(114,048	)		—			—			(114,048	)
	Interest rate swap agreements used for interest rate risk management			114,083			114,083			—			114,083			—
			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)	9 Months Ended
	Sep. 30, 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.
		September 30,		December 31,
		2013		2012
		(in thousands)
	Commitments to extend credit
	Home equity lines of credit	$	6,239,383		6,282,615
	Commercial real estate loans to be sold		60,479		139,929
	Other commercial real estate and construction		3,877,466		3,819,342
	Residential real estate loans to be sold		647,523		1,550,441
	Other residential real estate		410,647		445,268
	Commercial and other		10,629,010		10,070,711
	Standby letters of credit		3,684,608		4,025,329
	Commercial letters of credit		49,757		53,201
	Financial guarantees, indemnification contracts and other		2,394,180		2,120,361
	Commitments to sell real estate loans		1,294,488		2,625,408

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]	'
Information about Company's Segments	'
	Information about the Company’s segments is presented in the following table:
			Three months ended September 30
			2013								2012
			Total		Inter-			Net			Total			Inter-			Net
			revenues (a)		segment			income			revenues (a)			segment			income
					revenues			(loss)						revenues			(loss)
			(in thousands)
	Business Banking		$	107,887		1,237			26,552			114,181			1,011			38,411
	Commercial Banking			257,317		1,383			97,221			255,498			1,561			112,654
	Commercial Real Estate			171,094		399			79,450			169,806			5,031			75,896
	Discretionary Portfolio			44,040		(19,584	)		25,182			1,805			(25,593	)		(5,039	)
	Residential Mortgage Banking			92,505		15,241			12,731			138,662			28,454			44,727
	Retail Banking			314,273		3,351			53,965			318,567			2,841			58,441
	All Other			163,380		(2,027	)		(622	)		109,936			(13,305	)		(31,628	)
	Total		$	1,150,496		—			294,479			1,108,455			—			293,462
			Nine months ended September 30
			2013								2012
			Total		Inter-			Net			Total			Inter-			Net
			revenues (a)		segment			income			revenues (a)			segment			income
					revenues			(loss)						revenues			(loss)
			(in thousands)
	Business Banking		$	319,791		3,750			89,675			335,475			3,202			110,829
	Commercial Banking			760,074		4,048			291,828			741,714			4,832			315,373
	Commercial Real Estate			524,160		2,505			245,826			491,433			5,860			225,025
	Discretionary Portfolio			41,972		(38,200	)		18,992			(11,162	)		(60,990	)		(28,037	)
	Residential Mortgage Banking			324,168		55,528			81,235			341,699			100,350			94,238
	Retail Banking			898,295		10,206			157,815			939,409			8,931			165,289
	All Other			557,244		(37,837	)		31,687			306,632			(62,185	)		(149,412	)
	Total		$	3,425,704		—			917,058			3,145,200			—			733,305
Summary of Segment Information	'
			Average total assets
			Nine months ended					Year ended
			September 30					December 31
			2013		2012			2012
			(in millions)
	Business Banking		$	5,041		4,918			4,909
	Commercial Banking			21,554		19,691			19,946
	Commercial Real Estate			17,112		16,364			16,437
	Discretionary Portfolio			16,224		16,428			16,583
	Residential Mortgage Banking			2,783		2,316			2,451
	Retail Banking			11,304		11,746			11,705
	All Other			9,082		8,055			7,952
	Total		$	83,100		79,518			79,983
	(a)	Total revenues are comprised of net interest income and other income. Net interest income is the difference between 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 allocation 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 $6,105,000 and $6,534,000 for the three-month periods ended September 30, 2013 and 2012, respectively, and $18,772,000 and $19,884,000 for the nine-month periods ended September 30, 2013 and 2012, respectively, and is eliminated in “All Other” total revenues. Intersegment revenues are included in total revenues of the reportable segments. The elimination of intersegment revenues is included in the determination of “All Other” total revenues.

Acquisitions_Additional_Inform

Acquisitions - Additional Information (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Aug. 27, 2012
Business Acquisition [Line Items]	'	'	'
Purchase consideration per common share	'	'	0.08403
Total consideration to be paid	$4,800,000,000	'	'
Assets	84,427,485,000	83,008,803,000	'
Investment securities	8,309,773,000	6,074,361,000	'
Liabilities	73,411,283,000	72,806,210,000	'
Deposits	66,552,141,000	65,611,253,000	'
Hudson City [Member]	'	'	'
Business Acquisition [Line Items]	'	'	'
Assets	39,200,000,000	'	'
Loans	24,700,000,000	'	'
Investment securities	10,000,000,000	'	'
Liabilities	34,500,000,000	'	'
Deposits	$22,100,000,000	'	'
Cash [Member]	'	'	'
Business Acquisition [Line Items]	'	'	'
Percentage of total consideration	'	'	40.00%
Common stock [Member]	'	'	'
Business Acquisition [Line Items]	'	'	'
Percentage of total consideration	'	'	60.00%

Acquisitions_Summary_of_Merger

Acquisitions - Summary of Merger-Related Expenses (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Summary of merger-related expenses	'	'	'	'
Salaries and employee benefits	$339,332	$321,746	$1,019,019	$991,530
Equipment and net occupancy	66,220	64,248	195,657	194,667
Printing, postage and supplies	9,752	8,272	30,749	31,512
Other costs of operations	217,817	183,875	558,905	540,927
Bank Acquisition [Member]	'	'	'	'
Summary of merger-related expenses	'	'	'	'
Salaries and employee benefits	'	'	836	4,997
Equipment and net occupancy	'	'	690	15
Printing, postage and supplies	'	'	1,825	'
Other costs of operations	'	'	9,013	4,867
Total merger-related expenses	'	'	$12,364	$9,879

Investment_securities_Amortize

Investment securities - Amortized Cost and Estimated Fair Value of Investment Securities (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Other securities, Amortized cost	$298,479	$302,648
Other securities, Gross unrealized gains	'	'
Other securities, Gross unrealized losses	'	'
Other securities, Estimated fair value	298,479	302,648
Investment securities, available for sale, amortized cost	4,555,109	4,643,070
Gross unrealized gains	160,328	253,619
Gross unrealized losses	23,257	157,252
Estimated fair value	4,692,180	4,739,437
Amortized cost for held to maturity	3,319,114	1,032,276
Gross unrealized gains for held to maturity	44,266	39,534
Gross unrealized losses for held to maturity	85,994	94,927
Estimated fair value for held to maturity	3,277,386	976,883
Total Amortized cost	8,172,702	5,977,994
Total for Gross unrealized gains	204,594	293,153
Total for Gross unrealized losses	109,251	252,179
Total for Estimated fair value	8,268,045	6,018,968
Government Issued or Guaranteed [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Investment securities, available for sale, amortized cost	4,214,895	3,163,210
Gross unrealized gains	116,758	208,060
Gross unrealized losses	1,254	229
Estimated fair value	4,330,399	3,371,041
Amortized cost for held to maturity	2,914,687	597,340
Gross unrealized gains for held to maturity	39,987	31,727
Gross unrealized losses for held to maturity	29,015	'
Estimated fair value for held to maturity	2,925,659	629,067
Privately issued [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Amortized cost for held to maturity	224,767	242,378
Gross unrealized gains for held to maturity	'	160
Gross unrealized losses for held to maturity	56,891	94,900
Estimated fair value for held to maturity	167,876	147,638
Privately Issued Mortgage-Backed Securities [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Investment securities, available for sale, amortized cost	2,789	1,142,287
Gross unrealized gains	1,032	7,272
Gross unrealized losses	5	125,673
Estimated fair value	3,816	1,023,886
Collateralized Debt Obligations [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Investment securities, available for sale, amortized cost	42,686	43,228
Gross unrealized gains	17,724	19,663
Gross unrealized losses	1,107	1,022
Estimated fair value	59,303	61,869
Obligations of States and Political Subdivisions [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Investment securities, available for sale, amortized cost	17,614	20,375
Gross unrealized gains	355	534
Gross unrealized losses	6	8
Estimated fair value	17,963	20,901
Amortized cost for held to maturity	170,370	182,103
Gross unrealized gains for held to maturity	4,279	7,647
Gross unrealized losses for held to maturity	88	27
Estimated fair value for held to maturity	174,561	189,723
Other Debt Securities [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Investment securities, available for sale, amortized cost	137,661	136,603
Gross unrealized gains	1,758	2,247
Gross unrealized losses	20,015	26,900
Estimated fair value	119,404	111,950
Amortized cost for held to maturity	9,290	10,455
Gross unrealized gains for held to maturity	'	'
Gross unrealized losses for held to maturity	'	'
Estimated fair value for held to maturity	9,290	10,455
U.S. Treasury and Federal Agencies [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Investment securities, available for sale, amortized cost	37,432	38,422
Gross unrealized gains	480	922
Gross unrealized losses	25	'
Estimated fair value	37,887	39,344
Equity Securities [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Investment securities, available for sale, amortized cost	102,032	98,945
Gross unrealized gains	22,221	14,921
Gross unrealized losses	845	3,420
Estimated fair value	$123,408	$110,446

Investment_securities_Addition

Investment securities - Additional Information (Detail) (USD $)	9 Months Ended		3 Months Ended	9 Months Ended			9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
	Investment		Privately Issued Mortgage-Backed Securities [Member]	Privately Issued Mortgage-Backed Securities [Member]	Privately Issued Mortgage-Backed Securities [Member]	Securities Backed by Trust Preferred Securities [Member]	Visa Class B [Member]	MasterCard Class B [Member]
Investment Holdings [Line Items]	'	'	'	'	'	'	'	'
Gross realized gains on investment securities	$116,000,000	'	'	'	'	'	'	'
Gain on sale of holdings	'	'	'	'	'	'	90,000,000	13,000,000
Gross realized losses on investment securities	60,000,000	'	'	'	'	'	'	'
Privately issued mortgage backed securities sold	'	'	'	1,000,000,000	'	'	'	'
Net loss on securities sold	'	'	'	46,000,000	'	'	'	'
Pre-tax other-than-temporary impairment losses	'	'	6,000,000	10,000,000	33,000,000	'	'	'
Number of investment securities with aggregate gross unrealized losses	299	'	'	'	'	'	'	'
Unrealized losses on individual investment securities	109,251,000	252,179,000	'	'	'	'	'	'
Unrealized losses on privately issued residential mortgage-backed securities	57,000,000	'	'	'	'	'	'	'
Investment securities owned at cost	'	'	'	225,000,000	'	132,000,000	'	'
Unrealized losses on trust preferred securities issued by financial institutions and securities backed by trust preferred securities	21,000,000	'	'	'	'	'	'	'
Cost Method Investment Securities	$298,000,000	'	'	'	'	'	'	'

Investment_securities_Changes_

Investment securities - Changes in Credit Losses Associated with Debt Securities for Which OTTI Losses (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Investments Debt And Equity Securities [Abstract]	'	'	'	'
Beginning balance	$794	$264,197	$197,809	$285,399
Additions for credit losses not previously recognized	'	5,672	9,800	33,331
Reductions for realized losses	-626	-67,926	-207,441	-116,787
Ending balance	$168	$201,943	$168	$201,943

Investment_securities_Amortize1

Investment securities - Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Debt securities available for sale:	'	'
Due in one year or less	$24,886	'
Due after one year through five years	21,212	'
Due after five years through ten years	8,282	'
Due after ten years	181,013	'
Total available for sale (amortized cost)	235,393	'
Mortgage-backed securities available for sale	4,217,684	'
Total	4,453,077	'
Debt securities held to maturity:	'	'
Due in one year or less	18,617	'
Due after one year through five years	65,392	'
Due after five years through ten years	86,361	'
Due after ten years	9,290	'
Total available for held to maturity (amortized cost)	179,660	'
Mortgage-backed securities held to maturity	3,139,454	'
Total	3,319,114	1,032,276
Debt securities available for sale:	'	'
Due in one year or less	24,971	'
Due after one year through five years	22,016	'
Due after five years through ten years	8,553	'
Due after ten years	179,017	'
Total available for available for sale (fair value)	234,557	'
Mortgage-backed securities available for sale	4,334,215	'
Total	4,568,772	'
Debt securities held to maturity:	'	'
Due in one year or less	18,751	'
Due after one year through five years	67,400	'
Due after five years through ten years	88,410	'
Due after ten years	9,290	'
Total available for held to maturity (fair value)	183,851	'
Mortgage-backed securities held to maturity	3,093,535	'
Estimated fair value for held to maturity	$3,277,386	$976,883

Investment_securities_Investme

Investment securities - Investment Securities in Continuous Unrealized Loss Position (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Estimated fair value, Less than 12 months	$185,779	$139,295
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	-2,005	-2,053
Estimated fair value, 12 months or more	115,290	888,499
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	-21,252	-155,199
Held to maturity, Estimated fair value, Less than 12 months	1,274,104	1,026
Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses	-29,085	-5
Held to maturity, Estimated fair value, 12 months or more	169,434	150,831
Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Aggregate Losses	-56,909	-94,922
Total investment securities, fair value less than 12 months	1,459,883	140,321
Investment Securities Continuous Unrealized Loss Position Less Than Twelve Months Aggregate Losses	-31,090	-2,058
Total of investment securities, fair value, 12 Months or More	284,724	1,039,330
Investment Securities Continuous Unrealized Loss Position Twelve Months or Longer Aggregate Losses	-78,161	-250,121
Government Issued or Guaranteed [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Estimated fair value, Less than 12 months	174,503	12,107
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	-1,126	-65
Estimated fair value, 12 months or more	5,731	8,804
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	-128	-164
Held to maturity, Estimated fair value, Less than 12 months	1,259,353	'
Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses	-29,015	'
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 Securities [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	167,876	147,273
Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Aggregate Losses	-56,891	-94,900
Privately Issued Mortgage-Backed Securities [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity Securities [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	107	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 Securities [Line Items]	'	'
Estimated fair value, Less than 12 months	577	166
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	-2	-1
Estimated fair value, 12 months or more	559	683
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	-4	-7
Held to maturity, Estimated fair value, Less than 12 months	14,751	1,026
Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Aggregate Losses	-70	-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	-18	-22
U.S. Treasury and federal agencies [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Estimated fair value, Less than 12 months	6,346	'
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	-25	'
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 Securities [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	5,995	6,043
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	-1,107	-1,022
Other Debt Securities [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Estimated fair value, Less than 12 months	1,576	'
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	-7	'
Estimated fair value, 12 months or more	102,898	95,685
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or More Aggregate Losses	-20,008	-26,900
Equity Securities [Member]	'	'
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]	'	'
Estimated fair value, Less than 12 months	2,777	5,535
Available For Sale Securities Continuous Unrealized Losses Position Less Than Twelve Months Aggregate Losses	-845	-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_and_the_Allow2

Loans and Leases and the Allowance for Credit Losses - Outstanding Principal Balance and Carrying Amount of Loans that is Included in Consolidated Balance Sheet (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Outstanding principal and carrying value of acquired loans recorded at fair value	'	'
Outstanding principal balance	$5,274,466	$6,705,120
Carrying amount	4,563,252	5,840,353
Commercial, Financial, Leasing, etc. [Member]	'	'
Outstanding principal and carrying value of acquired loans recorded at fair value	'	'
Carrying amount	730,743	928,107
Real Estate Commercial [Member]	'	'
Outstanding principal and carrying value of acquired loans recorded at fair value	'	'
Carrying amount	1,875,842	2,567,050
Residential Real Estate [Member]	'	'
Outstanding principal and carrying value of acquired loans recorded at fair value	'	'
Carrying amount	598,820	707,309
Consumer [Member]	'	'
Outstanding principal and carrying value of acquired loans recorded at fair value	'	'
Carrying amount	$1,357,847	$1,637,887

Loans_and_Leases_and_the_Allow3

Loans and Leases and the Allowance for Credit Losses - Additional Information (Detail) (USD $)	9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013	Dec. 30, 2012	Sep. 30, 2013	Dec. 30, 2012
				Residential mortgage loans [Member]	Residential mortgage loans [Member]	Commercial Real Estate [Member]	Commercial Real Estate [Member]
Loans And Leases Receivable [Line Items]	'	'	'	'	'	'	'
Contractual principal and interest payments	$357	'	$447	'	'	'	'
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	'	'	'	'
Mortgage loans held for sale	'	'	'	667	1,200	'	'
Commercial mortgage loans held for sale	'	'	'	'	'	152	200
Loan delinquent period	'90 days or more	'	'	'	'	'	'
Maturity period of line of credit	'More than 150 days	'	'	'	'	'	'
Payment default for troubled debt restructuring	$20	$13	'	'	'	'	'

Loans_and_Leases_and_the_Allow4

Loans and Leases and the Allowance for Credit Losses - Summary of Changes in Accretable Yield for Acquired Loans (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Purchased impaired [Member]	'	'	'	'
Summary of changes in Accretable Yield for acquired loans	'	'	'	'
Balance at beginning of period	$55,149	$55,599	$42,252	$30,805
Interest income	-10,428	-12,436	-28,879	-29,721
Reclassifications from nonaccretable balance, net	172	542	31,520	42,621
Other	'	'	'	'
Balance at end of period	44,893	43,705	44,893	43,705
Other [Member]	'	'	'	'
Summary of changes in Accretable Yield for acquired loans	'	'	'	'
Balance at beginning of period	622,093	733,161	638,272	807,960
Interest income	-60,786	-74,936	-190,072	-228,908
Reclassifications from nonaccretable balance, net	'	'	122,519	98,165
Other	6,254	1,382	-3,158	-17,610
Balance at end of period	$567,561	$659,607	$567,561	$659,607

Loans_and_Leases_and_the_Allow5

Loans and Leases and the Allowance for Credit Losses - Summary of Current, Past Due and Nonaccrual Loans (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Loans And Leases Receivable [Line Items]	'	'
Current	$61,166,841	$63,854,815
30-89 Days past due	725,616	730,901
Purchased impaired	357,337	447,114
Nonaccrual	915,871	1,013,176
Total	63,659,042	66,570,957
Commercial, Financial, Leasing, etc. [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	17,678,290	17,511,052
30-89 Days past due	91,757	62,479
Purchased impaired	16,257	17,437
Nonaccrual	111,116	151,908
Total	17,911,149	17,776,953
Commercial [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	21,447,385	21,759,997
30-89 Days past due	179,972	118,249
Purchased impaired	101,049	132,962
Nonaccrual	198,397	193,859
Total	21,990,515	22,273,173
Residential Builder and Developer [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	921,728	757,311
30-89 Days past due	10,622	35,419
Purchased impaired	138,651	187,764
Nonaccrual	113,096	181,865
Total	1,196,502	1,189,526
Other Commercial Construction [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	3,029,504	2,379,953
30-89 Days past due	16,903	35,274
Purchased impaired	68,539	68,971
Nonaccrual	36,326	36,812
Total	3,158,250	2,531,091
Residential [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	7,884,094	9,811,956
30-89 Days past due	301,564	337,969
Purchased impaired	30,201	36,769
Nonaccrual	252,987	249,314
Total	8,830,995	10,794,316
Residential Alt-A [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	297,840	331,021
30-89 Days past due	18,263	19,692
Purchased impaired	'	'
Nonaccrual	80,905	95,808
Total	397,008	446,521
Home Equity Lines and Loans [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	6,027,315	6,199,591
30-89 Days past due	32,428	40,759
Purchased impaired	2,640	3,211
Nonaccrual	77,537	58,071
Total	6,169,392	6,321,950
Automobile [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	1,144,216	2,442,502
30-89 Days past due	39,221	40,461
Purchased impaired	'	'
Nonaccrual	22,087	25,107
Total	1,205,705	2,508,321
Other [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Current	2,736,469	2,661,432
30-89 Days past due	34,886	40,599
Purchased impaired	'	'
Nonaccrual	23,420	20,432
Total	2,799,526	2,729,106
Non-Acquired [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	339,792	358,397
Non-Acquired [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	2,582	23,490
Non-Acquired [Member] | Commercial [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	12,859	13,111
Non-Acquired [Member] | Residential Builder and Developer [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	52	3,258
Non-Acquired [Member] | Other Commercial Construction [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	1,888	509
Non-Acquired [Member] | Residential [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	317,660	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 [Member] | Home Equity Lines and Loans [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	'	'
Non-Acquired [Member] | Automobile [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	'	'
Non-Acquired [Member] | Other [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	4,751	4,845
Acquired [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	153,585	166,554
Acquired [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	11,147	10,587
Acquired [Member] | Commercial [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	50,853	54,995
Acquired [Member] | Residential Builder and Developer [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	12,353	23,909
Acquired [Member] | Other Commercial Construction [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	5,090	9,572
Acquired [Member] | Residential [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	44,489	45,124
Acquired [Member] | Residential Alt-A [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	'	'
Acquired [Member] | Home Equity Lines and Loans [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	29,472	20,318
Acquired [Member] | Automobile [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	181	251
Acquired [Member] | Other [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
90 Days or more past due and accruing	'	$1,798

Recovered_Sheet1

Loans and leases and the allowance for credit losses - Changes in Allowance for Credit Losses (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'	'
Beginning balance	$927,065	$917,028	$925,860	$908,290
Provision for credit losses	48,000	46,000	143,000	155,000
Allowance related to loans securitized and sold	-11,000	'	-11,000	'
Net charge-offs	'	'	'	'
Charge-offs	-64,194	-50,096	-189,768	-174,534
Recoveries	16,499	8,291	48,278	32,467
Net charge-offs	-47,695	-41,805	-141,490	-142,067
Ending balance	916,370	921,223	916,370	921,223
Commercial, Financial, Leasing, etc. [Member]	'	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'	'
Beginning balance	268,867	244,728	246,759	234,022
Provision for credit losses	20,209	439	93,736	29,663
Allowance related to loans securitized and sold	'	'	'	'
Net charge-offs	'	'	'	'
Charge-offs	-30,931	-8,874	-86,787	-32,989
Recoveries	5,150	1,174	9,587	6,771
Net charge-offs	-25,781	-7,700	-77,200	-26,218
Ending balance	263,295	237,467	263,295	237,467
Real Estate Commercial [Member]	'	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'	'
Beginning balance	324,264	341,521	337,101	367,637
Provision for credit losses	12,139	9,891	914	4,322
Allowance related to loans securitized and sold	'	'	'	'
Net charge-offs	'	'	'	'
Charge-offs	-7,701	-7,982	-21,493	-31,578
Recoveries	4,751	1,421	16,931	4,470
Net charge-offs	-2,950	-6,561	-4,562	-27,108
Ending balance	333,453	344,851	333,453	344,851
Residential Real Estate [Member]	'	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'	'
Beginning balance	85,311	93,269	88,807	91,915
Provision for credit losses	315	8,247	3,913	30,064
Allowance related to loans securitized and sold	'	'	'	'
Net charge-offs	'	'	'	'
Charge-offs	-5,320	-8,687	-18,583	-32,812
Recoveries	2,399	1,139	8,568	4,801
Net charge-offs	-2,921	-7,548	-10,015	-28,011
Ending balance	82,705	93,968	82,705	93,968
Consumer [Member]	'	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'	'
Beginning balance	174,291	164,352	179,418	143,121
Provision for credit losses	14,935	26,962	43,478	88,927
Allowance related to loans securitized and sold	-11,000	'	-11,000	'
Net charge-offs	'	'	'	'
Charge-offs	-20,242	-24,553	-62,905	-77,155
Recoveries	4,199	4,557	13,192	16,425
Net charge-offs	-16,043	-19,996	-49,713	-60,730
Ending balance	162,183	171,318	162,183	171,318
Unallocated [Member]	'	'	'	'
Financing Receivable, Allowance for Credit Losses [Line Items]	'	'	'	'
Beginning balance	74,332	73,158	73,775	71,595
Provision for credit losses	402	461	959	2,024
Allowance related to loans securitized and sold	'	'	'	'
Net charge-offs	'	'	'	'
Charge-offs	'	'	'	'
Recoveries	'	'	'	'
Net charge-offs	'	'	'	'
Ending balance	$74,734	$73,619	$74,734	$73,619

Loans_and_Leases_and_the_Allow6

Loans and Leases and the Allowance for Credit Losses - Impaired Loans and Leases (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	$934,597	$1,072,026
Unpaid principal balance	1,151,963	1,354,133
Related allowance	101,286	132,682
Commercial, Financial, Leasing, etc. [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	118,513	159,913
Unpaid principal balance	145,123	191,733
Related allowance	25,530	33,829
Commercial Real Estate [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	205,205	199,922
Unpaid principal balance	252,346	244,183
Related allowance	24,104	23,641
Residential Builder and Developer [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	117,962	189,613
Unpaid principal balance	187,247	321,656
Related allowance	7,374	25,661
Other Commercial Construction [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	94,076	96,562
Unpaid principal balance	101,231	100,401
Related allowance	3,104	6,836
Residential [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	183,328	189,793
Unpaid principal balance	212,470	218,267
Related allowance	6,537	3,521
Residential Alt-A [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	144,092	160,245
Unpaid principal balance	181,011	200,708
Related allowance	15,000	17,000
Home Equity Lines and Loans [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	13,258	12,360
Unpaid principal balance	14,372	13,567
Related allowance	3,408	2,254
Automobile [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	42,106	49,210
Unpaid principal balance	42,106	49,210
Related allowance	12,060	14,273
Other [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	16,057	14,408
Unpaid principal balance	16,057	14,408
Related allowance	4,169	5,667
Impaired Financing Receivable With Related Allowance [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	644,955	745,994
Unpaid principal balance	766,585	927,411
Related allowance	101,286	132,682
Impaired Financing Receivable With Related Allowance [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	93,568	127,282
Unpaid principal balance	114,572	149,534
Related allowance	25,530	33,829
Impaired Financing Receivable With Related Allowance [Member] | Commercial Real Estate [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	127,921	121,542
Unpaid principal balance	152,885	143,846
Related allowance	24,104	23,641
Impaired Financing Receivable With Related Allowance [Member] | Residential Builder and Developer [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	61,947	115,306
Unpaid principal balance	102,395	216,218
Related allowance	7,374	25,661
Impaired Financing Receivable With Related Allowance [Member] | Other Commercial Construction [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	74,116	73,544
Unpaid principal balance	77,180	76,869
Related allowance	3,104	6,836
Impaired Financing Receivable With Related Allowance [Member] | Residential [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	100,287	103,451
Unpaid principal balance	118,572	121,819
Related allowance	6,537	3,521
Impaired Financing Receivable With Related Allowance [Member] | Residential Alt-A [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	115,695	128,891
Unpaid principal balance	128,446	141,940
Related allowance	15,000	17,000
Impaired Financing Receivable With Related Allowance [Member] | Home Equity Lines and Loans [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	13,258	12,360
Unpaid principal balance	14,372	13,567
Related allowance	3,408	2,254
Impaired Financing Receivable With Related Allowance [Member] | Automobile [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	42,106	49,210
Unpaid principal balance	42,106	49,210
Related allowance	12,060	14,273
Impaired Financing Receivable With Related Allowance [Member] | Other [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	16,057	14,408
Unpaid principal balance	16,057	14,408
Related allowance	4,169	5,667
Impaired Financing Receivable with No Related Allowance [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	289,642	326,032
Unpaid principal balance	385,378	426,722
Related allowance	'	'
Impaired Financing Receivable with No Related Allowance [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	24,945	32,631
Unpaid principal balance	30,551	42,199
Related allowance	'	'
Impaired Financing Receivable with No Related Allowance [Member] | Commercial Real Estate [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	77,284	78,380
Unpaid principal balance	99,461	100,337
Related allowance	'	'
Impaired Financing Receivable with No Related Allowance [Member] | Residential Builder and Developer [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	56,015	74,307
Unpaid principal balance	84,852	105,438
Related allowance	'	'
Impaired Financing Receivable with No Related Allowance [Member] | Other Commercial Construction [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	19,960	23,018
Unpaid principal balance	24,051	23,532
Related allowance	'	'
Impaired Financing Receivable with No Related Allowance [Member] | Residential [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	83,041	86,342
Unpaid principal balance	93,898	96,448
Related allowance	'	'
Impaired Financing Receivable with No Related Allowance [Member] | Residential Alt-A [Member]	'	'
Financing Receivable, Impaired [Line Items]	'	'
Recorded investment	28,397	31,354
Unpaid principal balance	52,565	58,768
Related allowance	'	'

Loans_and_Leases_and_the_Allow7

Loans and Leases and the Allowance for Credit Losses - Interest Income Recognized on Loans (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Loans And Leases Receivable [Line Items]	'	'	'	'
Average recorded investment	$981,278	$1,017,603	$1,031,664	$1,072,657
Interest income recognized, Total	5,845	6,784	25,140	23,779
Interest income recognized, Cash basis	3,411	4,060	17,416	15,512
Commercial, Financial, Leasing, etc. [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Average recorded investment	149,357	141,166	164,877	155,627
Interest income recognized, Total	516	1,507	6,358	2,659
Interest income recognized, Cash basis	516	1,507	6,358	2,659
Commercial Real Estate [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Average recorded investment	205,971	180,009	200,354	179,524
Interest income recognized, Total	716	531	1,428	2,087
Interest income recognized, Cash basis	716	531	1,428	2,087
Residential Builder and Developer [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Average recorded investment	130,855	237,847	159,308	260,858
Interest income recognized, Total	213	476	871	1,202
Interest income recognized, Cash basis	188	370	637	801
Other Commercial Construction [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Average recorded investment	95,486	84,604	97,268	100,242
Interest income recognized, Total	208	9	3,322	5,019
Interest income recognized, Cash basis	208	9	3,322	5,019
Residential [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Average recorded investment	180,995	131,114	184,719	128,646
Interest income recognized, Total	1,391	1,269	4,795	3,926
Interest income recognized, Cash basis	865	765	3,188	2,453
Residential Alt-A [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Average recorded investment	147,056	167,780	151,992	174,390
Interest income recognized, Total	1,763	1,836	5,173	5,432
Interest income recognized, Cash basis	692	593	1,799	1,666
Home Equity Lines and Loans [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Average recorded investment	12,810	11,949	12,633	11,024
Interest income recognized, Total	167	172	499	502
Interest income recognized, Cash basis	49	48	127	136
Automobile [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Average recorded investment	42,957	51,138	45,075	52,249
Interest income recognized, Total	710	863	2,226	2,632
Interest income recognized, Cash basis	127	185	404	553
Other [Member]	'	'	'	'
Loans And Leases Receivable [Line Items]	'	'	'	'
Average recorded investment	15,791	11,996	15,438	10,097
Interest income recognized, Total	161	121	468	320
Interest income recognized, Cash basis	$50	$52	$153	$138

Loans_and_Leases_and_the_Allow8

Loans and Leases and the Allowance for Credit Losses - Summary of Loan Grades (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	$63,659,042	$66,570,957
Commercial, Financial, Leasing, etc. [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	17,911,149	17,776,953
Commercial, Financial, Leasing, etc. [Member] | Pass [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	17,022,772	16,889,753
Commercial, Financial, Leasing, etc. [Member] | Criticized Accrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	777,261	735,292
Commercial, Financial, Leasing, etc. [Member] | Criticized Nonaccrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	111,116	151,908
Commercial [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	21,990,515	22,273,173
Commercial [Member] | Pass [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	20,978,696	21,275,182
Commercial [Member] | Criticized Accrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	813,422	804,132
Commercial [Member] | Criticized Nonaccrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	198,397	193,859
Residential Builder and Developer [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	1,196,502	1,189,526
Residential Builder and Developer [Member] | Pass [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	1,005,932	922,141
Residential Builder and Developer [Member] | Criticized Accrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	77,474	85,520
Residential Builder and Developer [Member] | Criticized Nonaccrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	113,096	181,865
Other Commercial Construction [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	3,158,250	2,531,091
Other Commercial Construction [Member] | Pass [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	3,066,941	2,307,436
Other Commercial Construction [Member] | Criticized Accrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	54,983	186,843
Other Commercial Construction [Member] | Criticized Nonaccrual [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	$36,326	$36,812

Loans_and_Leases_and_the_Allow9

Loans and Leases and the Allowance for Credit Losses - Allocation of Allowance for Credit Losses on Basis of Company's Impairment Methodology (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	$916,370	$925,860
Allocated [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	841,636	852,085
Unallocated [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	74,734	73,775
Individually Evaluated for Impairment [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	100,823	131,656
Collectively Evaluated for Impairment [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	734,338	717,064
Purchased Impaired [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	6,475	3,365
Commercial, Financial, Leasing, etc. [Member] | Allocated [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	263,295	246,759
Commercial, Financial, Leasing, etc. [Member] | Individually Evaluated for Impairment [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	25,530	33,669
Commercial, Financial, Leasing, etc. [Member] | Collectively Evaluated for Impairment [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	234,912	212,930
Commercial, Financial, Leasing, etc. [Member] | Purchased Impaired [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	2,853	160
Commercial Real Estate [Member] | Allocated [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	333,453	337,101
Commercial Real Estate [Member] | Individually Evaluated for Impairment [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	34,139	55,291
Commercial Real Estate [Member] | Collectively Evaluated for Impairment [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	298,579	280,789
Commercial Real Estate [Member] | Purchased Impaired [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	735	1,021
Residential Real Estate [Member] | Allocated [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	82,705	88,807
Residential Real Estate [Member] | Individually Evaluated for Impairment [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	21,517	20,502
Residential Real Estate [Member] | Collectively Evaluated for Impairment [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	59,645	66,684
Residential Real Estate [Member] | Purchased Impaired [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	1,543	1,621
Consumer loans [Member] | Allocated [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	162,183	179,418
Consumer loans [Member] | Individually Evaluated for Impairment [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	19,637	22,194
Consumer loans [Member] | Collectively Evaluated for Impairment [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	141,202	156,661
Consumer loans [Member] | Purchased Impaired [Member]	'	'
Loans And Leases Receivable [Line Items]	'	'
Allowance for credit losses	$1,344	$563

Recovered_Sheet2

Loans and Leases and the Allowance for Credit Losses - Recorded Investment in Loans and Leases on Basis of Company's Impairment Methodology (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	$63,659,042	$66,570,957
Individually Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	930,237	1,065,551
Collectively Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	62,371,468	65,058,292
Purchased Impaired [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	357,337	447,114
Commercial, Financial, Leasing, etc. [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	17,911,149	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	118,513	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	17,776,379	17,599,755
Commercial, Financial, Leasing, etc. [Member] | Purchased Impaired [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	16,257	17,437
Commercial Real Estate [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	26,345,267	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	413,443	480,335
Commercial Real Estate [Member] | Collectively Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	25,623,585	25,123,758
Commercial Real Estate [Member] | Purchased Impaired [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	308,239	389,697
Residential Real Estate [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	9,228,003	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	326,860	349,477
Residential Real Estate [Member] | Collectively Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	8,870,942	10,854,591
Residential Real Estate [Member] | Purchased Impaired [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	30,201	36,769
Consumer loans [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	10,174,623	11,559,377
Consumer loans [Member] | Individually Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	71,421	75,978
Consumer loans [Member] | Collectively Evaluated for Impairment [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	10,100,562	11,480,188
Consumer loans [Member] | Purchased Impaired [Member]	'	'
Financing Receivable, Recorded Investment [Line Items]	'	'
Loans and leases, net of unearned discount	$2,640	$3,211

Recovered_Sheet3

Loans and Leases and the Allowance for Credit Losses - Loan Modification Activities that were Considered Troubled Debt Restructurings (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
	Modification	Modification	Modification	Modification
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	310	409	983	1,238
Pre-modification, Recorded investment	$18,441	$55,191	$233,447	$171,503
Post-modification, Recorded investment	19,189	53,591	229,746	168,746
Financial effects of modification, Recorded investment	748	-1,600	-3,701	-2,757
Financial effects of modification, Interest	-830	-790	-3,118	-1,983
Principal deferral [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	14	21	53	39
Pre-modification, Recorded investment	2,407	7,823	9,283	21,027
Post-modification, Recorded investment	2,266	7,653	9,070	19,668
Financial effects of modification, Recorded investment	-141	-170	-213	-1,359
Financial effects of modification, Interest	'	'	'	'
Principal deferral [Member] | Commercial Real Estate [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	10	8	23	11
Pre-modification, Recorded investment	4,160	5,951	38,187	10,387
Post-modification, Recorded investment	4,134	6,238	38,027	10,642
Financial effects of modification, Recorded investment	-26	287	-160	255
Financial effects of modification, Interest	'	'	'	'
Principal deferral [Member] | Residential Builder and Developer [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	1	11	16	19
Pre-modification, Recorded investment	249	17,383	19,102	26,708
Post-modification, Recorded investment	241	16,275	18,303	24,812
Financial effects of modification, Recorded investment	-8	-1,108	-799	-1,896
Financial effects of modification, Interest	'	'	'	'
Principal deferral [Member] | Other Commercial Construction [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	1	2	3	5
Pre-modification, Recorded investment	226	5,429	590	66,317
Post-modification, Recorded investment	158	4,702	521	65,600
Financial effects of modification, Recorded investment	-68	-727	-69	-717
Financial effects of modification, Interest	'	'	'	'
Principal deferral [Member] | Residential [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	6	5	21	27
Pre-modification, Recorded investment	860	738	2,642	3,302
Post-modification, Recorded investment	912	772	2,877	3,447
Financial effects of modification, Recorded investment	52	34	235	145
Financial effects of modification, Interest	'	'	'	'
Principal deferral [Member] | Residential Alt-A [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	5	1	6	5
Pre-modification, Recorded investment	764	218	863	768
Post-modification, Recorded investment	773	220	875	785
Financial effects of modification, Recorded investment	9	2	12	17
Financial effects of modification, Interest	'	'	'	'
Principal deferral [Member] | Home Equity Lines and Loans [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	2	5	6	15
Pre-modification, Recorded investment	179	434	359	1,285
Post-modification, Recorded investment	179	434	361	1,285
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	121	135	359	484
Pre-modification, Recorded investment	1,718	1,721	4,933	6,306
Post-modification, Recorded investment	1,718	1,721	4,933	6,306
Financial effects of modification, Recorded investment	'	'	'	'
Financial effects of modification, Interest	'	'	'	'
Principal deferral [Member] | Other [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	9	14	29	73
Pre-modification, Recorded investment	60	336	290	1,117
Post-modification, Recorded investment	60	336	290	1,117
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	2	'	4	3
Pre-modification, Recorded investment	1,773	'	50,433	2,967
Post-modification, Recorded investment	2,067	'	50,924	3,052
Financial effects of modification, Recorded investment	294	'	491	85
Financial effects of modification, Interest	'	'	'	'
Other [Member] | Commercial Real Estate [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	2	'	2	'
Pre-modification, Recorded investment	449	'	449	'
Post-modification, Recorded investment	475	'	475	'
Financial effects of modification, Recorded investment	26	'	26	'
Financial effects of modification, Interest	'	'	'	'
Other [Member] | Residential Builder and Developer [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	'	'	1	'
Pre-modification, Recorded investment	'	'	4,039	'
Post-modification, Recorded investment	'	'	3,888	'
Financial effects of modification, Recorded investment	'	'	-151	'
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	'
Pre-modification, Recorded investment	'	'	106	'
Post-modification, Recorded investment	'	'	106	'
Financial effects of modification, Recorded investment	'	'	'	'
Financial effects of modification, Interest	'	'	'	'
Other [Member] | Automobile [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	20	20	65	51
Pre-modification, Recorded investment	42	68	274	239
Post-modification, Recorded investment	42	68	274	239
Financial effects of modification, Recorded investment	'	'	'	'
Financial effects of modification, Interest	'	'	'	'
Other [Member] | Other [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	'	1	1	10
Pre-modification, Recorded investment	'	1	12	50
Post-modification, Recorded investment	'	1	12	50
Financial effects of modification, Recorded investment	'	'	'	'
Financial effects of modification, Interest	'	'	'	'
Interest rate reduction [Member] | Commercial Real Estate [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	'	'	'	1
Pre-modification, Recorded investment	'	'	'	383
Post-modification, Recorded investment	'	'	'	430
Financial effects of modification, Recorded investment	'	'	'	47
Financial effects of modification, Interest	'	'	'	-89
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	2	9	11	16
Pre-modification, Recorded investment	19	157	159	234
Post-modification, Recorded investment	19	157	159	234
Financial effects of modification, Recorded investment	'	'	'	'
Financial effects of modification, Interest	-2	-11	-17	-16
Interest rate reduction [Member] | Other [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	'	'	1	3
Pre-modification, Recorded investment	'	'	12	23
Post-modification, Recorded investment	'	'	12	23
Financial effects of modification, Recorded investment	'	'	'	'
Financial effects of modification, Interest	'	'	-2	-3
Combination of concession types [Member] | Commercial, Financial, Leasing, etc. [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	3	2	6	3
Pre-modification, Recorded investment	374	327	2,206	372
Post-modification, Recorded investment	374	322	1,696	366
Financial effects of modification, Recorded investment	'	-5	-510	-6
Financial effects of modification, Interest	-25	-39	-25	-72
Combination of concession types [Member] | Commercial Real Estate [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	6	1	8	5
Pre-modification, Recorded investment	1,868	214	2,450	1,424
Post-modification, Recorded investment	2,264	214	2,845	1,445
Financial effects of modification, Recorded investment	396	'	395	21
Financial effects of modification, Interest	-156	-49	-212	-305
Combination of concession types [Member] | Residential Builder and Developer [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	'	1	3	3
Pre-modification, Recorded investment	'	2,486	15,580	4,836
Post-modification, Recorded investment	'	2,486	15,514	5,212
Financial effects of modification, Recorded investment	'	'	-66	376
Financial effects of modification, Interest	'	'	-535	'
Combination of concession types [Member] | Residential [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	14	18	52	47
Pre-modification, Recorded investment	1,258	5,490	72,917	10,475
Post-modification, Recorded investment	1,308	5,553	69,734	10,658
Financial effects of modification, Recorded investment	50	63	-3,183	183
Financial effects of modification, Interest	-197	-150	-754	-415
Combination of concession types [Member] | Residential Alt-A [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	4	13	17	28
Pre-modification, Recorded investment	332	2,771	2,426	5,640
Post-modification, Recorded investment	496	2,795	2,715	5,732
Financial effects of modification, Recorded investment	164	24	289	92
Financial effects of modification, Interest	-252	'	-640	-49
Combination of concession types [Member] | Home Equity Lines and Loans [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	9	11	19	17
Pre-modification, Recorded investment	682	976	1,299	1,691
Post-modification, Recorded investment	682	976	1,299	1,691
Financial effects of modification, Recorded investment	'	'	'	'
Financial effects of modification, Interest	-79	-125	-176	-272
Combination of concession types [Member] | Automobile [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	61	109	184	298
Pre-modification, Recorded investment	551	2,329	2,148	5,108
Post-modification, Recorded investment	551	2,329	2,148	5,108
Financial effects of modification, Recorded investment	'	'	'	'
Financial effects of modification, Interest	-33	-319	-162	-601
Combination of concession types [Member] | Other [Member]	'	'	'	'
Financing Receivable, Modifications [Line Items]	'	'	'	'
Number of modifications	18	22	90	74
Pre-modification, Recorded investment	470	339	2,394	700
Post-modification, Recorded investment	470	339	2,394	700
Financial effects of modification, Recorded investment	'	'	'	'
Financial effects of modification, Interest	($86)	($97)	($587)	($155)

Borrowings_Additional_Informat

Borrowings - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended		3 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Mar. 31, 2013	Mar. 31, 2013	Mar. 31, 2013
			Junior Subordinated Debenture due January 31, 2068 [Member]	Unsecured senior and subordinated notes [Member]	Floating rate senior notes due March 2016 [Member]	Fixed rate senior notes due March 2018 [Member]
				M&T Bank [Member]	M&T Bank [Member]	M&T Bank [Member]
Schedule Of Borrowings [Line Items]	'	'	'	'	'	'
Junior subordinated debentures	$1,200,000,000	'	$350,000,000	'	'	'
Percentage of outstanding securities in Tier 1 capital in 2015	25.00%	'	'	'	'	'
Percentage outstanding securities included in tier one capital beginning in 2016	0.00%	'	'	'	'	'
Junior Subordinated Debentures Maturity Date	31-Jan-68	'	'	'	'	'
Debt Maturity, Start Year	1-Jan-27	'	'	'	'	'
Debt Maturity, End Year	31-Dec-68	'	'	'	'	'
Maximum unsecured senior and subordinate notes available for offering	'	'	'	5,000,000,000	'	'
Senior notes	'	'	'	'	300,000,000	500,000,000
Term of senior notes, year	'	'	'	'	'3 years	'5 years
Interest rate of senior notes	'	'	'	'	'	1.45%
Maturity period of senior notes	'	'	'	'	'2016-03	'2018-03
Agreements to repurchase securities	1,400,000,000	1,400,000,000	'	'	'	'
Collateral posted	$1,600,000,000	$1,600,000,000	'	'	'	'

Shareholders_Equity_Additional

Shareholders' Equity - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 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 expiring date	16-May-21	'

Shareholders_Equity_Issued_and

Shareholders' Equity - Issued and Outstanding Preferred Stock (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Class of Stock [Line Items]	'	'
Carrying value	$879,010	$872,500
Series A Fixed Rate Cumulative Perpetual Preferred Stock [Member]	'	'
Class of Stock [Line Items]	'	'
Preferred stock, shares issued and outstanding	230,000	'
Carrying value	229,236	226,965
Series C Fixed Rate Cumulative Perpetual Preferred Stock [Member]	'	'
Class of Stock [Line Items]	'	'
Preferred stock, shares issued and outstanding	151,500	'
Carrying value	149,774	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	'
Carrying value	$500,000	$500,000

Shareholders_Equity_Issued_and1

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

1 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

3 Months Ended

Aug. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Mar. 31, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Ten Year Warrant Series A Preferred [Member]

Series A [Member]

Ten Year Warrant Series C Preferred [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 D [Member]

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]

Series A Warrants [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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Issuance of common shares

'

130,194,232

128,176,912

'

'

'

'

'

'

186,589

'

'

'

'

'

'

'

'

Cashless warrants exercised

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

57,327

Common stock shares, Issued as a result of warrants exercised

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

21,130

Warrants and rights outstanding

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,161,195

Redemption days of shares by Company

'

'90 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Pension_Plans_and_Other_Postre2

Pension Plans and Other Postretirement Benefits - Net Periodic Benefit Cost for Defined Benefit Plans (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension benefits [Member]	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'
Service cost	$6,090	$7,387	$18,270	$22,162
Interest cost on projected benefit obligation	15,032	15,509	45,097	46,527
Expected return on plan assets	-21,838	-17,627	-65,515	-52,883
Amortization of prior service cost	-1,639	-1,640	-4,917	-4,919
Amortization of net actuarial loss	10,269	9,291	30,807	27,874
Net periodic benefit cost	7,914	12,920	23,742	38,761
Other postretirement benefits [Member]	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'
Service cost	186	167	557	501
Interest cost on projected benefit obligation	673	934	2,018	2,803
Expected return on plan assets	'	'	'	'
Amortization of prior service cost	-340	5	-1,019	15
Amortization of net actuarial loss	90	133	270	398
Net periodic benefit cost	$609	$1,239	$1,826	$3,717

Pension_Plans_and_Other_Postre3

Pension Plans and Other Postretirement Benefits - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Compensation And Retirement Disclosure [Abstract]	'	'	'	'
Defined contribution pension and retirement savings plans total expense	$12,440,000	$11,289,000	$40,757,000	$37,304,000

Earnings_Per_Common_Share_Comp

Earnings Per Common Share - Computations of Basic Earnings Per Common Share (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income available to common shareholders:	'	'	'	'
Net income	$294,479	$293,462	$917,058	$733,305
Less: Preferred stock dividends	-13,363	-13,363	-40,088	-40,088
Amortization of preferred stock discount	-2,235	-2,033	-6,575	-5,921
Net income available to common equity	278,881	278,066	870,395	687,296
Less: Income attributable to unvested stock-based compensation awards	-3,545	-4,181	-11,451	-10,475
Net income available to common shareholders	$275,336	$273,885	$858,944	$676,821
Weighted-average shares outstanding:	'	'	'	'
Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards	130,836	127,741	130,088	127,449
Less: Unvested stock-based compensation awards	-1,665	-1,923	-1,719	-1,939
Weighted-average shares outstanding	129,171	125,818	128,369	125,510
Basic earnings per common share	$2.13	$2.18	$6.69	$5.39

Earnings_Per_Common_Share_Comp1

Earnings Per Common Share - Computations of Diluted Earnings Per Common Share (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]	'	'	'	'
Net income available to common equity	$278,881	$278,066	$870,395	$687,296
Less: Income attributable to unvested stock-based compensation awards	-3,525	-4,170	-11,395	-10,454
Net income available to common shareholders	$275,356	$273,896	$859,000	$676,842
Adjusted weighted-average shares outstanding:	'	'	'	'
Common and unvested stock-based compensation awards	130,836	127,741	130,088	127,449
Less: Unvested stock-based compensation awards	-1,665	-1,923	-1,719	-1,939
Plus: Incremental shares from assumed conversion of stock-based compensation awards and warrants to purchase common stock	1,094	474	943	426
Adjusted weighted-average shares outstanding	130,265	126,292	129,312	125,936
Diluted earnings per common share	$2.11	$2.17	$6.64	$5.37

Earnings_Per_Common_Share_Addi

Earnings Per Common Share - Additional Information (Detail)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]	'	'	'	'
Antidilutive securities excluded from computation of earnings per share	3.1	9.7	4.1	9.9

Comprehensive_Income_Component

Comprehensive Income - Components of Other Comprehensive Income (Loss) and Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Components Of Comprehensive Income [Line Items]	'	'	'	'
Beginning balance	'	'	($395,657)	($586,769)
Unrealized holding gains (losses), net	'	'	-2,183	145,809
Foreign currency translation adjustment	'	'	296	552
Total other comprehensive income before reclassifications	'	'	-1,887	146,361
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	'	'	3,357	5,039
OTTI charges recognized in net income	'	'	9,800	33,331
Losses (gains) realized in net income	'	'	33,088	-9
Amortization of gains on terminated cash flow hedges	'	'	'	-178
Amortization of prior service credit	'	'	-5,936	-4,904
Amortization of actuarial losses	'	'	31,077	28,272
Total reclassifications	'	'	71,386	61,551
Total gain (loss) during the period	'	'	69,499	207,912
Ending balance	-326,158	-378,857	-326,158	-378,857
Beginning balance	'	'	155,393	230,328
Unrealized holding gains (losses), net	'	'	814	-57,183
Foreign currency translation adjustment	'	'	-91	-201
Total other comprehensive income before reclassifications	'	'	723	-57,384
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	'	'	-1,318	-1,978
OTTI charges recognized in net income	'	'	-3,847	-13,082
Losses (gains) realized in net income	'	'	-12,987	4
Amortization of gains on terminated cash flow hedges	'	'	'	66
Amortization of prior service credit	'	'	2,330	1,925
Amortization of actuarial losses	'	'	-12,198	-11,097
Total reclassifications	'	'	-28,020	-24,162
Total gain (loss) during the period	'	'	-27,297	-81,546
Ending balance	128,096	148,782	128,096	148,782
Beginning balance	'	'	-240,264	-356,441
Unrealized holding gains (losses), net	'	'	-1,369	88,626
Foreign currency translation adjustment	1,251	482	205	351
Total other comprehensive income before reclassifications	'	'	-1,164	88,977
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	'	'	2,039	3,061
OTTI charges recognized in net income	'	'	5,953	20,249
Losses (gains) realized in net income	'	'	20,101	-5
Amortization of gains on terminated cash flow hedges	'	'	'	-112
Amortization of prior service credit	'	'	-3,606	-2,979
Amortization of actuarial losses	'	'	18,879	17,175
Total reclassifications	'	'	43,366	37,389
Total other comprehensive income	29,709	47,774	42,202	126,366
Ending Balance	-198,062	-230,075	-198,062	-230,075
Investment Securities With OTTI [Member]	'	'	'	'
Components Of Comprehensive Income [Line Items]	'	'	'	'
Beginning balance	'	'	-91,835	-138,319
Unrealized holding gains (losses), net	'	'	59,523	-8,099
Foreign currency translation adjustment	'	'	'	'
Total other comprehensive income before reclassifications	'	'	59,523	-8,099
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	'	'	230	1,544
OTTI charges recognized in net income	'	'	9,800	33,331
Losses (gains) realized in net income	'	'	41,217	'
Amortization of gains on terminated cash flow hedges	'	'	'	'
Amortization of prior service credit	'	'	'	'
Amortization of actuarial losses	'	'	'	'
Total reclassifications	'	'	51,247	34,875
Total gain (loss) during the period	'	'	110,770	26,776
Ending balance	18,935	-111,543	18,935	-111,543
Investment Securities All Other [Member]	'	'	'	'
Components Of Comprehensive Income [Line Items]	'	'	'	'
Beginning balance	'	'	152,199	9,757
Unrealized holding gains (losses), net	'	'	-61,706	153,908
Foreign currency translation adjustment	'	'	'	'
Total other comprehensive income before reclassifications	'	'	-61,706	153,908
Accretion of unrealized holding losses on held-to-maturity ("HTM") securities	'	'	3,127	3,495
OTTI charges recognized in net income	'	'	'	'
Losses (gains) realized in net income	'	'	-8,129	-9
Amortization of gains on terminated cash flow hedges	'	'	'	'
Amortization of prior service credit	'	'	'	'
Amortization of actuarial losses	'	'	'	'
Total reclassifications	'	'	-5,002	3,486
Total gain (loss) during the period	'	'	-66,708	157,394
Ending balance	85,491	167,151	85,491	167,151
Defined Benefit Plans [Member]	'	'	'	'
Components Of Comprehensive Income [Line Items]	'	'	'	'
Beginning balance	'	'	-455,590	-457,145
Unrealized holding gains (losses), net	'	'	'	'
Foreign currency translation adjustment	'	'	'	'
Total other comprehensive income before reclassifications	'	'	'	'
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	'	'	-5,936	-4,904
Amortization of actuarial losses	'	'	31,077	28,272
Total reclassifications	'	'	25,141	23,368
Total gain (loss) during the period	'	'	25,141	23,368
Ending balance	-430,449	-433,777	-430,449	-433,777
Beginning balance	'	'	-276,771	'
Total other comprehensive income	'	'	15,273	'
Ending Balance	-261,498	'	-261,498	'
Other [Member]	'	'	'	'
Components Of Comprehensive Income [Line Items]	'	'	'	'
Beginning balance	'	'	-431	-1,062
Unrealized holding gains (losses), net	'	'	'	'
Foreign currency translation adjustment	'	'	296	552
Total other comprehensive income before reclassifications	'	'	296	552
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
Amortization of prior service credit	'	'	'	'
Amortization of actuarial losses	'	'	'	'
Total reclassifications	'	'	'	-178
Total gain (loss) during the period	'	'	296	374
Ending balance	($135)	($688)	($135)	($688)

Comprehensive_Income_Accumulat

Comprehensive Income - Accumulated Other Comprehensive Income (Loss), Net Consisted of Unrealized Gains (Losses) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Beginning balance	'	'	($240,264)	($356,441)
Net gain (loss) during period	29,709	47,774	42,202	126,366
Ending Balance	-198,062	-230,075	-198,062	-230,075
Defined Benefit Plans [Member]	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Beginning balance	'	'	-276,771	'
Net gain (loss) during period	'	'	15,273	'
Ending Balance	-261,498	'	-261,498	'
Accumulated Other Adjustment [Member]	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Beginning balance	'	'	-284	'
Net gain (loss) during period	'	'	205	'
Ending Balance	-79	'	-79	'
Investment Securities [Member] | Investment Securities With OTTI [Member]	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Beginning balance	'	'	-55,790	'
Net gain (loss) during period	'	'	67,293	'
Ending Balance	11,503	'	11,503	'
Investment Securities [Member] | Investment Securities All Other [Member]	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Beginning balance	'	'	92,581	'
Net gain (loss) during period	'	'	-40,569	'
Ending Balance	$52,012	'	$52,012	'

Derivative_Financial_Instrumen2

Derivative Financial Instruments - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Derivative [Line Items]	'	'	'	'	'
Increase in net interest income due to interest rate swap agreements	$11,000,000	$9,000,000	$30,000,000	$27,000,000	'
Notional value of foreign currency and other option and futures contracts entered into for trading purposes	904,000,000	'	904,000,000	'	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	'	'	27,000,000	'	89,000,000
Aggregate fair value of derivative financial instruments in a liability position	229,000,000	'	229,000,000	'	374,000,000
Net liability positions with counterparties	132,000,000	'	132,000,000	'	281,000,000
Post collateral requirements relating to positions	118,000,000	'	118,000,000	'	266,000,000
Fair value of additional collateral to be posted for derivative financial instruments	13,000,000	'	13,000,000	'	'
Aggregate fair value of derivative financial instruments in asset position	187,000,000	'	187,000,000	'	164,000,000
Net asset positions with counterparties	98,000,000	'	98,000,000	'	71,000,000
Counterparties posted collateral relating to positions	96,000,000	'	96,000,000	'	69,000,000
Credit Risk Derivative [Member]	'	'	'	'	'
Derivative [Line Items]	'	'	'	'	'
Aggregate fair value of derivative financial instruments in a net liability position	42,000,000	'	42,000,000	'	'
Fair value of collateral already posted for derivative financial instruments	29,000,000	'	29,000,000	'	'
Interest rate contracts [Member]	'	'	'	'	'
Derivative [Line Items]	'	'	'	'	'
Notional value of interest rate contracts entered into trading purposes	$15,900,000,000	'	$15,900,000,000	'	$15,500,000,000

Derivative_Financial_Instrumen3

Derivative Financial Instruments - Information about Interest Rate Swap Agreements (Detail) (Fixed rate long-term borrowings [Member], Fair Value Hedges [Member], USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 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 10 months 24 days	'4 years 4 months 24 days
Weighted-average rate, Fixed	4.42%	6.07%
Weighted-average rate, Variable	1.22%	1.85%

Derivative_Financial_Instrumen4

Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Balance Sheet (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Derivatives, Fair Value [Line Items]	'	'
Asset derivatives, Fair value	$440,518	$603,019
Liability derivatives, Fair value	285,659	384,866
Derivatives designated and qualifying as hedging instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Asset derivatives, Fair value	116,560	144,293
Liability derivatives, Fair value	11,665	3,825
Derivatives not designated and qualifying as hedging instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Asset derivatives, Fair value	323,958	458,726
Liability derivatives, Fair value	273,994	381,041
Interest rate swap agreements [Member] | Derivatives designated and qualifying as hedging instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Asset derivatives, Fair value	114,083	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	2,477	1,114
Liability derivatives, Fair value	11,665	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	6,880	1,982
Liability derivatives, Fair value	7,435	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	18,185	48,056
Liability derivatives, Fair value	5,110	197
Interest rate contracts [Member] | Derivatives not designated and qualifying as hedging instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Asset derivatives, Fair value	285,442	399,963
Liability derivatives, Fair value	248,311	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	13,451	8,725
Liability derivatives, Fair value	$13,138	$8,658

Derivative_Financial_Instrumen5

Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Statement of Income (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Derivatives not designated as hedging instruments, Derivatives	$1,916	$851	$3,505	$925
Interest rate contracts [Member]	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Derivatives not designated as hedging instruments, Derivatives	2,778	777	5,974	3,996
Foreign exchange and other option and futures contracts [Member]	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Derivatives not designated as hedging instruments, Derivatives	-862	74	-2,469	-3,071
Interest rate swap agreements [Member] | Fixed rate long-term borrowings [Member]	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Derivatives in fair value hedging relationships, Derivatives	-86	3,273	-29,097	5,918
Derivatives in fair value hedging relationships, Hedged item	($20)	($3,252)	$27,733	($5,876)

Variable_Interest_Entities_and1

Variable Interest Entities and Asset Securitizations - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012
Variable Interest Entity Disclosure [Abstract]	'	'	'
Residential mortgage loans securitized with Ginnie Mae	$1,800,000,000	$2,800,000,000	'
Residential mortgage loans securitized formerly held in Company's portfolio	1,000,000,000	1,400,000,000	'
Residential mortgage loans securitized newly originated	811,000,000	1,400,000,000	'
Recognized gain	35,000,000	42,000,000	'
Gains of newly originated loans	15,000,000	25,000,000	'
Automobile loans securitized and sold	1,400,000,000	'	'
Recognized gains sale of securities	21,000,000	'	'
Carrying value of loans in the Securitization trusts	126,000,000	126,000,000	151,000,000
Combined outstanding principal amount of mortgage-backed securities issued by qualified special purpose trust held by unrelated parties	19,000,000	19,000,000	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	34,000,000
Total assets of real estate partnerships in which the company invested	1,400,000,000	1,400,000,000	1,500,000,000
Maximum exposure to loss of investments in real estate partnerships	250,000,000	250,000,000	270,000,000
Unfunded commitments included in company's maximum exposure to loss of investments in real estate partnerships	$57,000,000	$57,000,000	$71,000,000

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
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	'	2	'	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	43,000,000	'	43,000,000	'	43,000,000
Fair value of securities issued by financial institutions and other entities backed by trust preferred securities	59,000,000	'	59,000,000	'	62,000,000
OTTI losses	'	'	'	5,000,000	'
Loans measured at fair value on nonrecurring basis	247,000,000	320,000,000	247,000,000	320,000,000	'
Change in fair value of nonrecurring fair value measured loans for charge-offs and impairment reserves	33,000,000	17,000,000	82,000,000	47,000,000	'
Nonrecurring fair value measurement	20,000,000	51,000,000	20,000,000	51,000,000	'
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	163,000,000	221,000,000	163,000,000	221,000,000	'
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	$84,000,000	$99,000,000	$84,000,000	$99,000,000	'
Minimum [Member]	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Discount margin over LIBOR	5.00%	'	5.00%	'	'
Discount rates for fair value estimations	'	'	10.00%	'	'
Maximum [Member]	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Discount margin over LIBOR	11.00%	'	11.00%	'	'
Discount rates for fair value estimations	'	'	80.00%	'	'

Fair_Value_Measurements_Assets

Fair Value Measurements - Assets and Liabilities Measured at Estimated Fair Value on Recurring Basis (Detail) (USD $)	Sep. 30, 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	$371,370	$488,966
Investment securities	4,692,180	4,739,437
Real estate loans held for sale	819,029	1,387,491
Other assets	141,625	194,331
Total assets	6,024,204	6,810,225
Trading account liabilities	261,449	374,274
Other liabilities	24,210	10,592
Total liabilities	285,659	384,866
U.S. Treasury and Federal Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	37,887	39,344
Obligations of States and Political Subdivisions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	17,963	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	4,330,399	3,371,041
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Mortgage-backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	3,816	1,023,886
Collateralized Debt Obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	59,303	61,869
Other Debt Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	119,404	111,950
Equity Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	123,408	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	48,344	56,106
Investment securities	91,075	98,364
Real estate loans held for sale	'	'
Other assets	'	'
Total assets	139,419	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] | Mortgage-backed Securities, Issued by Private Enterprises [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	91,075	98,364
Significant Observable Inputs (Level 2) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading account assets	323,026	432,860
Investment securities	4,537,986	3,555,318
Real estate loans held for sale	819,029	1,387,491
Other assets	123,440	146,275
Total assets	5,803,481	5,521,944
Trading account liabilities	261,449	374,274
Other liabilities	19,100	10,395
Total liabilities	280,549	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	37,887	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	17,963	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	4,330,399	3,371,041
Significant Observable Inputs (Level 2) [Member] | Mortgage-backed Securities, Issued by Private Enterprises [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	119,404	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	32,333	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	63,119	1,085,755
Real estate loans held for sale	'	'
Other assets	18,185	48,056
Total assets	81,304	1,133,811
Trading account liabilities	'	'
Other liabilities	5,110	197
Total liabilities	5,110	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] | Mortgage-backed Securities, Issued by Private Enterprises [Member] | Mortgage-backed Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Investment securities	3,816	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	59,303	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 $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Total gains (losses) realized/unrealized:	'	'	'	'
Included in other comprehensive income	'	'	'	'
Sales	'	'	'	'
Settlements	'	'	'	'
Other assets and other liabilities [Member]	'	'	'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'	'	'
Beginning Balance	7,408	34,051	47,859	6,923
Total gains (losses) realized/unrealized:	'	'	'	'
Included in earnings	24,440	84,864	83,252	157,381
Transfers in and/or out of Level 3	-18,773	-48,570	-118,036	-93,959
Ending Balance	13,075	70,345	13,075	70,345
Changes in unrealized gains (losses) included in earnings related to assets still held at end of period	-1,727	63,357	925	70,187
Mortgage-backed Securities, Issued by Private Enterprises [Member]	'	'	'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'	'	'
Beginning Balance	5,272	1,080,519	1,023,886	1,151,285
Total gains (losses) realized/unrealized:	'	'	'	'
Included in earnings	'	-5,672	-56,102	-27,976
Included in other comprehensive income	400	40,603	116,984	89,397
Sales	'	'	-978,608	'
Settlements	-1,856	-49,814	-102,344	-147,070
Transfers in and/or out of Level 3	'	'	'	'
Ending Balance	3,816	1,065,636	3,816	1,065,636
Changes in unrealized gains (losses) included in earnings related to assets still held at end of period	'	-5,672	'	-27,976
Collateralized Debt Obligations [Member]	'	'	'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'	'	'
Beginning Balance	59,916	55,098	61,869	52,500
Total gains (losses) realized/unrealized:	'	'	'	'
Included in earnings	'	'	'	'
Included in other comprehensive income	213	3,297	-324	7,008
Settlements	-826	-1,194	-2,242	-2,307
Transfers in and/or out of Level 3	'	'	'	'
Ending Balance	59,303	57,201	59,303	57,201
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 $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Privately Issued Mortgage-Backed Securities [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Investments	$3,816	$1,023,886
Valuation technique	'Two independent price quotes	'Discounted cash flow
Unobservable inputs/assumptions	'-	'Probability of default and Loss severity
Privately Issued Mortgage-Backed Securities [Member] | Weighted Average [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Probability of default	'	19.00%
Loss severity	'	51.00%
Privately Issued Mortgage-Backed Securities [Member] | Minimum [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Probability of default	'	1.00%
Loss severity	'	32.00%
Privately Issued Mortgage-Backed Securities [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	59,303	61,869
Valuation technique	'Discounted cash flow	'Discounted cash flow
Unobservable inputs/assumptions	'Probability of default and Loss severity	'Probability of default and 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	13.00%	22.00%
Loss severity	'	'
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%
Net Other Assets (Liabilities) [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Investments	$13,075	$47,859
Valuation technique	'Discounted cash flow	'Discounted cash flow
Unobservable inputs/assumptions	'Commitment expirations	'Commitment expirations
Net Other Assets (Liabilities) [Member] | Weighted Average [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Commitment expirations weighted-average	21.00%	20.00%
Net Other Assets (Liabilities) [Member] | Minimum [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Commitment expirations	0.00%	0.00%
Net Other Assets (Liabilities) [Member] | Maximum [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Commitment expirations	91.00%	69.00%

Fair_Value_Measurements_Carryi

Fair Value Measurements - Carrying Amounts and Estimated Fair Value for Financial Instrument Assets (Liabilities) (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Financial assets:	'	'	'	'
Cash and cash equivalents	$2,059,753	$1,986,615	$1,622,928	$1,452,397
Interest-bearing deposits at banks	1,925,811	129,945	'	'
Trading account assets	371,370	488,966	'	'
Loans and leases:	'	'	'	'
Allowance for credit losses	-916,370	-925,860	'	'
Loans and leases, net	62,742,672	65,645,097	'	'
Financial liabilities:	'	'	'	'
Noninterest-bearing deposits	-24,150,771	-24,240,802	'	'
Time deposits	-3,831,443	-4,562,366	'	'
Deposits at Cayman Islands office	-316,510	-1,044,519	'	'
Long-term borrowings	-5,121,326	-4,607,758	'	'
Carrying Amount [Member]	'	'	'	'
Financial assets:	'	'	'	'
Cash and cash equivalents	2,059,753	1,986,615	'	'
Interest-bearing deposits at banks	1,925,811	129,945	'	'
Trading account assets	371,370	488,966	'	'
Investment securities	8,309,773	6,074,361	'	'
Loans and leases:	'	'	'	'
Commercial loans and leases	17,911,149	17,776,953	'	'
Commercial real estate loans	26,345,267	25,993,790	'	'
Residential real estate loans	9,228,003	11,240,837	'	'
Consumer loans	10,174,623	11,559,377	'	'
Allowance for credit losses	-916,370	-925,860	'	'
Loans and leases, net	62,742,672	65,645,097	'	'
Accrued interest receivable	234,208	222,897	'	'
Financial liabilities:	'	'	'	'
Noninterest-bearing deposits	-24,150,771	-24,240,802	'	'
Savings deposits and NOW accounts	-38,253,417	-35,763,566	'	'
Time deposits	-3,831,443	-4,562,366	'	'
Deposits at Cayman Islands office	-316,510	-1,044,519	'	'
Short-term borrowings	-246,019	-1,074,482	'	'
Long-term borrowings	-5,121,326	-4,607,758	'	'
Accrued interest payable	-62,773	-54,281	'	'
Trading account liabilities	-261,449	-374,274	'	'
Other financial instruments:	'	'	'	'
Commitments to originate real estate loans for sale	13,075	47,859	'	'
Commitments to sell real estate loans	-9,743	-7,299	'	'
Other credit-related commitments	-114,048	-119,464	'	'
Interest rate swap agreements used for interest rate risk management	114,083	143,179	'	'
Estimate Fair Value [Member]	'	'	'	'
Financial assets:	'	'	'	'
Cash and cash equivalents	2,059,753	1,986,615	'	'
Interest-bearing deposits at banks	1,925,811	129,945	'	'
Trading account assets	371,370	488,966	'	'
Investment securities	8,268,045	6,018,968	'	'
Loans and leases:	'	'	'	'
Commercial loans and leases	17,685,646	17,554,562	'	'
Commercial real estate loans	26,256,932	25,858,482	'	'
Residential real estate loans	9,198,681	11,381,319	'	'
Consumer loans	10,151,004	11,504,799	'	'
Allowance for credit losses	'	'	'	'
Loans and leases, net	63,292,263	66,299,162	'	'
Accrued interest receivable	234,208	222,897	'	'
Financial liabilities:	'	'	'	'
Noninterest-bearing deposits	-24,150,771	-24,240,802	'	'
Savings deposits and NOW accounts	-38,253,417	-35,763,566	'	'
Time deposits	-3,853,552	-4,584,384	'	'
Deposits at Cayman Islands office	-316,510	-1,044,519	'	'
Short-term borrowings	-246,019	-1,074,482	'	'
Long-term borrowings	-5,257,947	-4,768,408	'	'
Accrued interest payable	-62,773	-54,281	'	'
Trading account liabilities	-261,449	-374,274	'	'
Other financial instruments:	'	'	'	'
Commitments to originate real estate loans for sale	13,075	47,859	'	'
Commitments to sell real estate loans	-9,743	-7,299	'	'
Other credit-related commitments	-114,048	-119,464	'	'
Interest rate swap agreements used for interest rate risk management	114,083	143,179	'	'
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'	'	'
Financial assets:	'	'	'	'
Cash and cash equivalents	1,992,949	1,895,423	'	'
Interest-bearing deposits at banks	'	'	'	'
Trading account assets	48,344	56,106	'	'
Investment securities	91,075	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	66,804	91,192	'	'
Interest-bearing deposits at banks	1,925,811	129,945	'	'
Trading account assets	323,026	432,860	'	'
Investment securities	7,945,975	4,687,211	'	'
Loans and leases:	'	'	'	'
Commercial loans and leases	'	'	'	'
Commercial real estate loans	151,690	199,997	'	'
Residential real estate loans	5,757,491	8,100,915	'	'
Consumer loans	'	'	'	'
Allowance for credit losses	'	'	'	'
Loans and leases, net	5,909,181	8,300,912	'	'
Accrued interest receivable	234,208	222,897	'	'
Financial liabilities:	'	'	'	'
Noninterest-bearing deposits	-24,150,771	-24,240,802	'	'
Savings deposits and NOW accounts	-38,253,417	-35,763,566	'	'
Time deposits	-3,853,552	-4,584,384	'	'
Deposits at Cayman Islands office	-316,510	-1,044,519	'	'
Short-term borrowings	-246,019	-1,074,482	'	'
Long-term borrowings	-5,257,947	-4,768,408	'	'
Accrued interest payable	-62,773	-54,281	'	'
Trading account liabilities	-261,449	-374,274	'	'
Other financial instruments:	'	'	'	'
Commitments to originate real estate loans for sale	'	'	'	'
Commitments to sell real estate loans	-9,743	-7,299	'	'
Other credit-related commitments	'	'	'	'
Interest rate swap agreements used for interest rate risk management	114,083	143,179	'	'
Significant Unobservable Inputs (Level 3) [Member]	'	'	'	'
Financial assets:	'	'	'	'
Cash and cash equivalents	'	'	'	'
Interest-bearing deposits at banks	'	'	'	'
Trading account assets	'	'	'	'
Investment securities	230,995	1,233,393	'	'
Loans and leases:	'	'	'	'
Commercial loans and leases	17,685,646	17,554,562	'	'
Commercial real estate loans	26,105,242	25,658,485	'	'
Residential real estate loans	3,441,190	3,280,404	'	'
Consumer loans	10,151,004	11,504,799	'	'
Allowance for credit losses	'	'	'	'
Loans and leases, net	57,383,082	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	13,075	47,859	'	'
Commitments to sell real estate loans	'	'	'	'
Other credit-related commitments	-114,048	-119,464	'	'
Interest rate swap agreements used for interest rate risk management	'	'	'	'

Commitments_and_Contingencies_1

Commitments and Contingencies - Company's Significant Commitments (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Commitments to extend credit	'	'
Home equity lines of credit	$6,239,383	$6,282,615
Commercial real estate loans to be sold	60,479	139,929
Other commercial real estate and construction	3,877,466	3,819,342
Residential real estate loans to be sold	647,523	1,550,441
Other residential real estate	410,647	445,268
Commercial and other	10,629,010	10,070,711
Standby letters of credit	3,684,608	4,025,329
Commercial letters of credit	49,757	53,201
Financial guarantees, indemnification contracts and other	2,394,180	2,120,361
Commitments to sell real estate loans	$1,294,488	$2,625,408

Commitments_and_Contingencies_2

Commitments and Contingencies - Additional Information (Detail) (USD $)	Sep. 30, 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	$2,200,000,000	$2,000,000,000
Outstanding loan principal balances reinsured	46,000,000	'
Assets of subsidiaries providing reinsurance to satisfy claims	37,000,000	'
Range of reasonably possible losses, minimum	0	'
Range of reasonably possible losses, maximum	70,000,000	'
2011 - 2013 [Member]	'	'
Significant Commitments [Line Items]	'	'
Naming rights of football stadium per year	5,000,000	'
2014 - 2017 [Member]	'	'
Significant Commitments [Line Items]	'	'
Naming rights of football stadium per year	$6,000,000	'

Segment_Information_Informatio

Segment Information - Information about Company's Segments (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]	'	'	'	'
Net income (loss)	$294,479	$293,462	$917,058	$733,305
Business Banking [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net income (loss)	26,552	38,411	89,675	110,829
Commercial Banking [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net income (loss)	97,221	112,654	291,828	315,373
Commercial Real Estate [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net income (loss)	79,450	75,896	245,826	225,025
Discretionary Portfolio [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net income (loss)	25,182	-5,039	18,992	-28,037
Residential Mortgage Banking [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net income (loss)	12,731	44,727	81,235	94,238
Retail Banking [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net income (loss)	53,965	58,441	157,815	165,289
All Other [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net income (loss)	-622	-31,628	31,687	-149,412
Operating Segments [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	1,150,496	1,108,455	3,425,704	3,145,200
Operating Segments [Member] | Business Banking [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	107,887	114,181	319,791	335,475
Operating Segments [Member] | Commercial Banking [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	257,317	255,498	760,074	741,714
Operating Segments [Member] | Commercial Real Estate [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	171,094	169,806	524,160	491,433
Operating Segments [Member] | Discretionary Portfolio [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	44,040	1,805	41,972	-11,162
Operating Segments [Member] | Residential Mortgage Banking [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	92,505	138,662	324,168	341,699
Operating Segments [Member] | Retail Banking [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	314,273	318,567	898,295	939,409
Operating Segments [Member] | All Other [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	163,380	109,936	557,244	306,632
Intersegment activity eliminated in consolidated totals [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	'	'	'	'
Intersegment activity eliminated in consolidated totals [Member] | Business Banking [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	1,237	1,011	3,750	3,202
Intersegment activity eliminated in consolidated totals [Member] | Commercial Banking [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	1,383	1,561	4,048	4,832
Intersegment activity eliminated in consolidated totals [Member] | Commercial Real Estate [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	399	5,031	2,505	5,860
Intersegment activity eliminated in consolidated totals [Member] | Discretionary Portfolio [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	-19,584	-25,593	-38,200	-60,990
Intersegment activity eliminated in consolidated totals [Member] | Residential Mortgage Banking [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	15,241	28,454	55,528	100,350
Intersegment activity eliminated in consolidated totals [Member] | Retail Banking [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	3,351	2,841	10,206	8,931
Intersegment activity eliminated in consolidated totals [Member] | All Other [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Total revenues	($2,027)	($13,305)	($37,837)	($62,185)

Segment_information_Summary_of

Segment information - Summary of Segment Information (Detail) (Reporting Segment [Member], USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
In Millions, unless otherwise specified
Sales Information [Line Items]	'	'	'
Average Assets	$83,100	$79,983	$79,518
Business Banking [Member]	'	'	'
Sales Information [Line Items]	'	'	'
Average Assets	5,041	4,909	4,918
Commercial Banking [Member]	'	'	'
Sales Information [Line Items]	'	'	'
Average Assets	21,554	19,946	19,691
Commercial Real Estate [Member]	'	'	'
Sales Information [Line Items]	'	'	'
Average Assets	17,112	16,437	16,364
Discretionary Portfolio [Member]	'	'	'
Sales Information [Line Items]	'	'	'
Average Assets	16,224	16,583	16,428
Residential Mortgage Banking [Member]	'	'	'
Sales Information [Line Items]	'	'	'
Average Assets	2,783	2,451	2,316
Retail Banking [Member]	'	'	'
Sales Information [Line Items]	'	'	'
Average Assets	11,304	11,705	11,746
All Other [Member]	'	'	'
Sales Information [Line Items]	'	'	'
Average Assets	$9,082	$7,952	$8,055

Segment_information_Summary_of1

Segment information - Summary of Segment Information (Parenthetical) (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting [Abstract]	'	'	'	'
Taxable-equivalent adjustment	$6,105,000	$6,534,000	$18,772,000	$19,884,000

Relationship_with_Bayview_Lend1

Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P. - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Schedule Of Equity Method Investments Joint Ventures [Line Items]	'	'	'	'	'
Minority interest in Bayview Lending Group LLC	'	'	20.00%	'	'
Carrying value of minority interest investment in Bayview Lending Group LLC	$80,000,000	'	$80,000,000	'	'
Outstanding principal balances of commercial mortgage servicing rights obtained from Bayview Financial	3,400,000,000	'	3,400,000,000	'	3,800,000,000
Outstanding principal balances of residential mortgage loans from Bayview Financial	2,400,000,000	'	2,400,000,000	'	2,700,000,000
Revenues from servicing residential and small balance commercial mortgage loans purchased from BLG and Bayview Financial	7,000,000	9,000,000	23,000,000	27,000,000	'
Collateralized mortgage obligations in available-for-sale investment securities portfolio securitized by Bayview Financial	4,000,000	'	4,000,000	'	11,000,000
Investment securities in held-to-maturity portfolio securitized by Bayview Financial	225,000,000	'	225,000,000	'	242,000,000
Bayview and Colonial [Member]	'	'	'	'	'
Schedule Of Equity Method Investments Joint Ventures [Line Items]	'	'	'	'	'
Outstanding principal balances of residential mortgage loans from Bayview Financial	45,500,000,000	'	45,500,000,000	'	11,400,000,000
Revenues from servicing residential and small balance commercial mortgage loans purchased from BLG and Bayview Financial	8,000,000	2,000,000	12,000,000	7,000,000	'
Residential real estate loans addition	$35,000,000,000	'	'	'	'