International Bancshares (IBOC) 10-K 27 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Feb. 20, 2015	Jun. 30, 2014
Document and Entity Information
Entity Registrant Name	INTERNATIONAL BANCSHARES CORP
Entity Central Index Key	315709
Document Type	10-K
Document Period End Date	31-Dec-14
Amendment Flag	FALSE
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$1,805,961,000
Entity Common Stock, Shares Outstanding		66,405,410
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY

Consolidated_Statements_of_Con

Consolidated Statements of Condition (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Assets
Cash and cash equivalents	$255,146	$274,785
Investment securities:
Held to maturity (Market value of $2,400 on December 31, 2014 and $2,400 on December 31, 2013)	2,400	2,400
Available for sale (Amortized cost of $4,914,428 on December 31, 2014 and $5,372,594 on December 31, 2013)	4,931,963	5,304,579
Total investment securities	4,934,363	5,306,979
Loans	5,679,245	5,199,235
Less allowance for probable loan losses	-64,828	-70,161
Net loans	5,614,417	5,129,074
Bank premises and equipment, net	526,423	504,842
Accrued interest receivable	31,461	30,654
Other investments	420,670	388,563
Identified intangible assets, net	797	3,186
Goodwill	282,532	282,532
Other assets	130,711	158,862
Total assets	12,196,520	12,079,477
Deposits:
Demand - non-interest bearing	2,930,253	2,666,510
Savings and interest bearing demand	3,025,680	2,925,612
Time	2,482,692	2,651,303
Total deposits	8,438,625	8,243,425
Securities sold under repurchase agreements	858,350	957,381
Other borrowed funds	1,073,944	1,223,950
Junior subordinated deferrable interest debentures	175,416	190,726
Other liabilities	69,527	39,587
Total liabilities	10,615,862	10,655,069
Shareholders' equity:
Common shares of $1.00 par value. Authorized 275,000,000 shares; issued 95,783,977 shares on December 31, 2014 and 95,743,592 shares on December 31, 2013	95,784	95,744
Surplus	165,520	163,947
Retained earnings	1,585,389	1,467,000
Accumulated other comprehensive income (loss) (including $(4,881) on December 31, 2014 and $(5,646) on December 31, 2013 of comprehensive loss related to other-than-temporary impairment for non-credit related issues)	11,397	-43,774
Total shareholders' equity before treasury stock	1,858,090	1,682,917
Less cost of shares in treasury, 29,324,567 shares on December 31,2014 and December 31, 2013	-277,432	-258,509
Total shareholders' equity	1,580,658	1,424,408
Total liabilities and shareholders' equity	$12,196,520	$12,079,477

Consolidated_Statements_of_Con1

Consolidated Statements of Condition (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Consolidated Statements of Condition
Held to maturity, Market value (in dollars)	$2,400	$2,400
Available for sale, Amortized cost (in dollars)	4,914,428	5,372,594
Common shares, par value (in dollars per share)	$1	$1
Common shares, Authorized shares	275,000,000	275,000,000
Common shares, issued shares	95,783,977	95,743,592
Accumulated other comprehensive income, comprehensive loss related to other-than-temporary impairment for non-credit related issues (in dollars)	($4,881)	($5,646)
Treasury, shares	29,324,567	28,537,180

Consolidated_Statements_of_Inc

Consolidated Statements of Income (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Interest income:
Loans, including fees	$281,546	$263,027	$268,588
Investment securities:
Taxable	100,095	87,198	94,885
Tax-exempt	11,767	12,877	11,663
Other interest income	191	115	503
Total interest income	393,599	363,217	375,639
Interest expense:
Savings and interest bearing demand deposits	3,597	3,762	5,288
Time deposits	12,033	15,444	23,973
Securities sold under repurchase agreements	24,616	29,171	37,645
Other borrowings	2,033	1,590	998
Junior subordinated deferrable interest debentures	4,264	4,665	6,595
Total interest expense	46,543	54,632	74,499
Net interest income	347,056	308,585	301,140
Provision for probable loan losses	14,423	22,968	27,959
Net interest income after provision for probable loan losses	332,633	285,617	273,181
Non-interest income:
Service charges on deposit accounts	88,586	97,087	93,128
Other service charges, commissions and fees
Banking	44,435	41,075	38,523
Non-banking	7,463	7,116	6,998
Investment securities transactions, net	1,283	9,601	38,446
Other investments, net	22,023	22,383	13,339
Other income	14,558	12,343	10,157
Total non-interest income	178,348	189,605	200,591
Non-interest expense:
Employee compensation and benefits	121,511	119,845	118,041
Occupancy	32,530	31,766	34,608
Depreciation of bank premises and equipment	24,013	26,017	26,756
Professional fees	10,925	13,146	14,369
Deposit insurance assessments	6,082	6,737	7,709
Net expense, other real estate owned	2,358	6,896	8,929
Amortization of identified intangible assets	2,389	4,633	4,651
Advertising	7,742	7,034	7,017
Early termination fee - securities sold under repurchase agreements	11,000	12,303	31,550
Impairment charges (Total other-than-temporary impairment charges, $(366) less loss of $1,183, $(431) less loss of $1,805, and $(916) less gain of $(123), included in other comprehensive loss)	817	1,374	1,039
Other	61,676	62,881	60,703
Total non-interest expense	281,043	292,632	315,372
Income before income taxes	229,938	182,590	158,400
Provision for income taxes	76,787	56,239	50,565
Net income	153,151	126,351	107,835
Preferred stock dividends and discount accretion			14,362
Net income available to common shareholders	$153,151	$126,351	$93,473
Basic earnings per common share:
Weighted average number of shares outstanding: (in shares)	66,872,500	67,195,180	67,236,681
Net income (in dollars per share)	$2.29	$1.88	$1.39
Fully diluted earnings per common share:
Weighted average number of shares outstanding: (in shares)	67,056,456	67,314,859	67,313,963
Net income (in dollars per share)	$2.28	$1.88	$1.39

Consolidated_Statements_of_Inc1

Consolidated Statements of Income (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Income
Impairment charges, other-than-temporary impairment charges	($366)	($431)	($916)
Impairment charges, other comprehensive (loss) income	$1,183	$1,805	($123)

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Comprehensive Income
Net income	$153,151	$126,351	$107,835
Other comprehensive income (loss), net of tax:
Net unrealized holding gains (losses) on securities available for sale arising during period (net of tax effects of $29870, $(56,048), and $2,701)	55,474	-104,088	5,018
Reclassification adjustment for gains on securities available for sale included in net income (net of tax effects of $(449), $(3,360), and $(13,456)),	-834	-6,241	-24,990
Reclassification adjustment for impairment charges on available for sale securities included in net income (net of tax effects of $286, $481, and $364, )	531	893	675
Other comprehensive income (loss), net of tax	55,171	-109,436	-19,297
Comprehensive income	$208,322	$16,915	$88,538

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Comprehensive Income
Net unrealized holding gains (losses) on securities available for sale arising during period, tax effects	$29,870	($56,048)	$2,701
Reclassification adjustment for gains on securities available for sale included in net income, tax effects	-449	-3,360	-13,456
Reclassification adjustment for impairment charges on available for sale securities included in net income, tax effects	$286	$481	$364

Consolidated_Statements_of_Sha

Consolidated Statements of Shareholders' Equity (USD $)	Preferred Stock	Common Stock	Surplus	Retained Earnings	Other Comprehensive Income (Loss)	Treasury Stock	Total
In Thousands, except Share data, unless otherwise specified
Balance at Dec. 31, 2011	$210,548	$95,720	$162,767	$1,302,964	$84,959	($256,793)	$1,600,165
Balance (in shares) at Dec. 31, 2011	95,720
Increase (decrease) in shareholders' equity
Net Income				107,835			107,835
Dividends:
Cash ($.52, $.43 and $.40 per share for the year ended December 31, 2014, 2013 and 2012, respectively)				-26,894			-26,894
Preferred stock (5%) including discount accretion	5,452			-14,362			-8,910
Redemption of Series A Preferred Shares (216,000 shares for the year ended December 31, 2012)	-216,000						-216,000
Purchase of treasury stock (95,466 and 787,387 shares for the year ended December 31, 2012 and 2014, respectively)						-1,716	-1,716
Exercise of stock options		5	46				51
Exercise of stock options (in shares)	5
Stock compensation expense recognized in earnings			474				474
Other comprehensive income (loss), net of tax:
Net change in unrealized gains and losses on available for sale securities, net of reclassification adjustments					-19,297		-19,297
Balance at Dec. 31, 2012		95,725	163,287	1,369,543	65,662	-258,509	1,435,708
Balance (in shares) at Dec. 31, 2012	95,725
Increase (decrease) in shareholders' equity
Net Income				126,351			126,351
Dividends:
Cash ($.52, $.43 and $.40 per share for the year ended December 31, 2014, 2013 and 2012, respectively)				-28,894			-28,894
Exercise of stock options		19	246				265
Exercise of stock options (in shares)	19
Stock compensation expense recognized in earnings			414				414
Other comprehensive income (loss), net of tax:
Net change in unrealized gains and losses on available for sale securities, net of reclassification adjustments					-109,436		-109,436
Balance at Dec. 31, 2013		95,744	163,947	1,467,000	-43,774	-258,509	1,424,408
Balance (in shares) at Dec. 31, 2013	95,744
Increase (decrease) in shareholders' equity
Net Income				153,151			153,151
Dividends:
Cash ($.52, $.43 and $.40 per share for the year ended December 31, 2014, 2013 and 2012, respectively)				-34,762			-34,762
Purchase of treasury stock (95,466 and 787,387 shares for the year ended December 31, 2012 and 2014, respectively)						-18,923	-18,923
Exercise of stock options		40	515				555
Exercise of stock options (in shares)	40
Stock compensation expense recognized in earnings			1,058				1,058
Other comprehensive income (loss), net of tax:
Net change in unrealized gains and losses on available for sale securities, net of reclassification adjustments					55,171		55,171
Balance at Dec. 31, 2014		$95,784	$165,520	$1,585,389	$11,397	($277,432)	$1,580,658
Balance (in shares) at Dec. 31, 2014	95,784

Consolidated_Statements_of_Sha1

Consolidated Statements of Shareholders' Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Shareholders' Equity
Cash Dividends (in dollars per share)	$0.52	$0.43	$0.40
Preferred stock, Rate (as a percent)			5.00%
Redemption of Series A Preferred Shares			216,000
Purchase of treasury stock (in shares)	787,387		95,466

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net income	$153,151,000	$126,351,000	$107,835,000
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for probable loan losses	14,423,000	22,968,000	27,959,000
Specific reserve, other real estate owned	779,000	1,204,000	1,776,000
Depreciation of bank premises and equipment	24,013,000	26,017,000	26,756,000
Gain on sale of bank premises and equipment	-3,658,000	-2,089,000	-538,000
(Gain) loss on sale of other real estate owned	-933,000	-460,000	488,000
Accretion of investment securities discounts	-2,608,000	-4,025,000	-3,195,000
Amortization of investment securities premiums	26,729,000	44,245,000	30,501,000
Investment securities transactions, net	-1,283,000	-9,601,000	-38,446,000
Impairment charges on available for sale securities	817,000	1,374,000	1,039,000
Amortization of identified intangible assets	2,389,000	4,633,000	4,651,000
Stock based compensation expense	1,058,000	414,000	474,000
Earnings from affiliates and other investments	-10,903,000	-18,806,000	-9,892,000
Deferred tax (benefit) expense	-1,027,000	-1,817,000	7,923,000
(Increase) decrease in accrued interest receivable	-807,000	380,000	968,000
(Increase) decrease in other assets	-1,621,000	20,612,000	-5,392,000
Increase (decrease) in other liabilities	-7,482,000	-2,274,000	7,106,000
Net cash provided by operating activities	193,037,000	209,126,000	160,013,000
Investing activities:
Proceeds from maturities of securities		1,200,000	1,125,000
Proceeds from sales and calls of available for sale securities	621,588,000	178,123,000	1,382,231,000
Purchases of available for sale securities	-971,358,000	-1,384,254,000	-3,081,034,000
Principal collected on mortgage backed securities	787,361,000	1,223,532,000	1,294,197,000
Net (increase) decrease in loans	-502,129,000	-444,919,000	170,072,000
Purchases of other investments	-20,602,000	-2,475,000	-4,228,000
Distributions from (contributions) to other investments	18,152,000	5,457,000	-7,410,000
Purchases of bank premises and equipment	-50,360,000	-50,016,000	-62,030,000
Proceeds from sales of bank premises and equipment	8,424,000	2,533,000	7,575,000
Proceeds from sales of other real estate owned	18,525,000	23,170,000	38,766,000
Purchase of identified intangible asset			-280,000
Net cash used in investing activities	-90,399,000	-447,649,000	-261,016,000
Financing activities:
Net increase in non-interest bearing demand deposits	263,743,000	200,760,000	538,732,000
Net increase in savings and interest bearing demand deposits	100,068,000	58,461,000	159,458,000
Net decrease in time deposits	-168,611,000	-303,009,000	-357,069,000
Net decrease in securities sold under repurchase agreements	-99,031,000	-172,298,000	-218,950,000
Other borrowed funds, net	-150,006,000	474,923,000	254,866,000
Repayment of long-term debt	-15,310,000
Purchase of treasury stock	-18,923,000		-1,716,000
Redemption of Series A preferred shares			-216,000,000
Proceeds from stock transactions	555,000	265,000	51,000
Payments of cash dividends - common	-34,762,000	-28,894,000	-26,894,000
Payments of cash dividends - preferred			-10,260,000
Net cash (used in) provided by financing activities	-122,277,000	230,208,000	122,218,000
(Decrease) increase in cash and cash equivalents	-19,639,000	-8,315,000	21,215,000
Cash and cash equivalents at beginning of year	274,785,000	283,100,000	261,885,000
Cash and cash equivalents at end of year	255,146,000	274,785,000	283,100,000
Supplemental cash flow information:
Interest paid	47,273,000	56,818,000	77,431,000
Income taxes paid	80,374,000	60,532,000	36,303,000
Non-cash investing and financing activities:
Net transfers from loans to other real estate owned	$2,363,000	$9,688,000	$54,441,000

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	(1) Summary of Significant Accounting Policies
	The accounting and reporting policies of International Bancshares Corporation ("Corporation") and Subsidiaries (the Corporation and Subsidiaries collectively referred to herein as the "Company") conform to accounting principles generally accepted in the United States of America and to general practices within the banking industry. The following is a description of the more significant of those policies.
	Consolidation and Basis of Presentation
	The consolidated financial statements include the accounts of the Corporation and its wholly-owned bank subsidiaries, International Bank of Commerce, Laredo ("IBC"), Commerce Bank, International Bank of Commerce, Zapata, International Bank of Commerce, Brownsville, and the Corporation's wholly-owned non-bank subsidiaries, IBC Subsidiary Corporation, IBC Life Insurance Company, IBC Trading Company, Premier Tierra Holdings, Inc., IBC Charitable and Community Development Corporation, and IBC Capital Corporation. All significant inter-company balances and transactions have been eliminated in consolidation.
	The Company, through its subsidiaries, is primarily engaged in the business of banking, including the acceptance of checking and savings deposits and the making of commercial, real estate, personal, home improvement, automobile and other installment and term loans. The primary markets of the Company are South, Central, and Southeast Texas and the state of Oklahoma. Each bank subsidiary is very active in facilitating international trade along the United States border with Mexico and elsewhere. Although the Company's loan portfolio is diversified, the ability of the Company's debtors to honor their contracts is primarily dependent upon the economic conditions in the Company's trade area. In addition, the investment portfolio is directly impacted by fluctuations in market interest rates. The Company and its bank subsidiaries are subject to the regulations of certain Federal agencies as well as the Texas Department of Banking and undergo periodic examinations by those regulatory authorities. Such agencies may require certain standards or impose certain limitations based on their judgments or changes in law and regulations.
	The Company owns two insurance-related subsidiaries, IBC Life Insurance Company and IBC Insurance Agency, Inc., a wholly owned subsidiary of IBC, the bank subsidiary. Neither of the insurance-related subsidiaries conducts underwriting activities. The IBC Life Insurance Company is in the business of reinsuring credit life and credit accident and health insurance. The business is assumed from an unaffiliated insurer and the only business written is generated by the bank subsidiaries of the Company. The risk assumed on each of the policies is not significant to the consolidated financial statements.
	The preparation of the consolidated financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the dates of the statement of condition and income and expenses for the periods. Actual results could differ significantly from those estimates. Material estimates that are particularly susceptible to significant changes in the near-term relate to the determination of the allowance for probable loan losses.
	Subsequent Events
	The Company has evaluated all events or transactions that occurred through the date the Company issued these financial statements. During this period, the Company did not have any material recognizable or non-recognizable subsequent events.
	Investment Securities
	The Company classifies debt and equity securities into one of these categories: held-to-maturity, available-for-sale, or trading. Such classifications are reassessed for appropriate classification at each reporting date. Securities that are intended and expected to be held until maturity are classified as "held-to-maturity" and are carried at amortized cost for financial statement reporting. Securities that are not positively expected to be held until maturity, but are intended to be held for an indefinite period of time are classified as "available-for-sale" or "trading" and are carried at their fair value. Unrealized holding gains and losses are included in net income for those securities classified as "trading", while unrealized holding gains and losses related to those securities classified as "available-for-sale" are excluded from net income and reported net of tax as other comprehensive income and in shareholders' equity as accumulated other comprehensive income until realized. The Company did not maintain any trading securities during the three year period ended December 31, 2014.
	Mortgage-backed securities held at December 31, 2014 and 2013 represent participating interests in pools of long-term first mortgage loans originated and serviced by the issuers of the securities. Mortgage-backed securities are either issued or guaranteed by the U.S. Government or its agencies including the Federal Home Loan Mortgage Corporation ("Freddie Mac"), the Federal National Mortgage Association ("Fannie Mae"), the Government National Mortgage Association ("Ginnie Mae") or other non-government entities. Investments in residential mortgage-backed securities issued by Ginnie Mae are fully guaranteed by the U. S. Government. Investments in residential mortgage-backed securities issued by Freddie Mac and Fannie Mae are not fully guaranteed by the U.S. Government, however, the Company believes that the quality of the bonds is similar to other AAA rated bonds with limited credit risk, particularly given the placement of Fannie Mae and Freddie Mac into conservatorship by the federal government in 2008 and because securities issued by others that are collateralized by residential mortgage-backed securities issued by Fannie Mae or Freddie Mac are rated consistently as AAA rated securities. Market interest rate fluctuations can affect the prepayment speed of principal and the yield on the security.
	Premiums and discounts are amortized using the level yield or "interest method" over the terms of the securities. Declines in the fair value of held-to-maturity and available-for sale-securities below their cost that are deemed to be other than temporary are reflected in earnings as realized losses. In determining whether other-than-temporary impairment exists, management considers many factors, including (1) the length of time and the extent to which the fair value has been less than cost, (2) the financial condition and near-term prospects of the issuer, and (3) the intent of the Company to hold and the determination of whether the Company will more likely than not be required to sell the security prior to a recovery in fair value. If the Company determines that (1) it intends to sell the security or (2) it is more likely than not that it will be required to sell the security before it's anticipated recovery, the other-than-temporary impairment that is recognized in earnings is equal to the difference between the fair value of the security and the Company's amortized cost in the security. If the Company determines that it (1) does not intend to sell the security and (2) it will not be more likely than not required to sell the security before it's anticipated recovery, the other-than-temporary impairment is segregated into its two components (1) the amount of impairment related to credit loss and (2) the amount of impairment related to other factors. The difference between the present value of the cash flows expected to be collected and the amortized cost is the credit loss recognized through earnings and an adjustment to the cost basis of the security. The amount of impairment related to other factors is included in other comprehensive income (loss). Gains and losses on the sale of securities are recorded on the trade date and are determined using the specific identification method.
	Provision and Allowance for Probable Loan Losses
	The allowance for probable loan losses is maintained at a level considered adequate by management to provide for probable loan losses. The allowance is increased by provisions charged to operating expense and reduced by net charge-offs. The provision for probable loan losses is the amount, which, in the judgment of management, is necessary to establish the allowance for probable loan losses at a level that is adequate to absorb known and inherent risks in the loan portfolio.
	Management believes that the allowance for probable loan losses is adequate. While management uses available information to recognize losses on loans, future additions to the allowance may be necessary based on changes in economic conditions. In addition, various regulatory agencies, as an integral part of their examination process, periodically review the Company's bank subsidiaries' allowances for probable loan losses. Such agencies may require the Company's bank subsidiaries to make additions or reductions to their U.S. generally accepted accounting principles ("GAAP") allowances based on their judgments of information available to them at the time of their examination.
	The bank subsidiaries charge off that portion of any loan which management considers to represent a loss as well as that portion of any other loan which is classified as a "loss" by bank examiners. Commercial, financial and agricultural or real estate loans are generally considered by management to represent a loss, in whole or part, (i) when an exposure beyond any collateral coverage is apparent, (ii) when no further collection of the portion of the loan so exposed is anticipated based on actual results, (iii) when the credit enhancements, if any, are not adequate, and (iv) when the borrower's financial condition would indicate so. Generally, unsecured consumer loans are charged off when 90 days past due.
	Loans
	Loans are reported at the principal balance outstanding, net of unearned discounts. Interest income on loans is reported on an accrual basis. Loan fees and costs associated with originating the loans are amortized over the life of the loan using the interest method. The Company originates mortgage loans that may subsequently be sold to an unaffiliated third party. The loans are not securitized and if sold, are sold without recourse. Loans held for sale are carried at cost and the principal amount outstanding is not significant to the consolidated financial statements.
	Impaired Loans
	Impaired loans are those loans where it is probable that all amounts due according to contractual terms of the loan agreement will not be collected. Impaired loans are measured based on (1) the present value of expected future cash flows discounted at the loan's effective interest rate; (2) the loan's observable market price; or (3) the fair value of the collateral if the loan is collateral dependent. Substantially all of the Company's impaired loans are measured at the fair value of the collateral. In limited cases the Company may use other methods to determine the level of impairment of a loan if such loan is not collateral dependent.
	Troubled Debt Restructured Loans
	Troubled debt restructured loans ("TDR") are those loans where, for reasons related to a borrower's difficulty to repay a loan, the Company grants a concession to the borrower that the Company would not normally consider in the normal course of business. The original terms of the loan are modified or restructured. The terms that may be modified include a reduction in the original stated interest rate, an extension of the original maturity of the loan, a renewal of the loan at an interest rate below current market rates, a reduction in the principal amount of debt outstanding, a reduction in accrued interest or deferral of interest payments. A loan classified as a TDR is classified as an impaired loan and included in the impaired loan totals. A TDR loan may be returned to accrual status when the loan is brought current, has performed in accordance with the restructured terms for a reasonable period of time and the ultimate collectability of the outstanding principal and interest is no longer questionable, however, although those loans may be placed back on accrual status, they will continue to be classified as impaired. Consistent with regulatory guidance, a TDR loan that is subsequently modified, but has shown sustained performance and classification as a TDR, will be removed from TDR status provided that the modified terms were market-based at the time of modification.
	Non-Accrual Loans
	The non-accrual loan policy of the Company's bank subsidiaries is to discontinue the accrual of interest on loans when management determines that it is probable that future interest accruals will be un-collectible. As it relates to consumer loans, management charges off those loans when the loan is contractually 90 days past due. Under special circumstances, a consumer or non-consumer loan may be more than 90 days delinquent as to interest or principal and not be placed on non-accrual status. This situation generally results when a bank subsidiary has a borrower who is experiencing financial difficulties, but not to the extent that requires a restructuring of indebtedness. The majority of this category is composed of loans that are considered to be adequately secured and/or for which there are expected future payments. When a loan is placed on non-accrual status, any interest accrued, not paid is reversed and charged to operations against interest income. As it relates to non-consumer loans that are not 90 days past due, management will evaluate each of these loans to determine if placing the loan on non-accrual status is warranted. Interest income on non-accrual loans is recognized only to the extent payments are received or when, in management's opinion, the debtor's financial condition warrants reestablishment of interest accruals.
	Other Real Estate Owned
	Other real estate owned is comprised of real estate acquired by foreclosure and deeds in lieu of foreclosure. Other real estate is carried at the lower of the recorded investment in the property or its fair value less estimated costs to sell such property (as determined by independent appraisal). Prior to foreclosure, the value of the underlying loan is written down to the fair value of the real estate to be acquired by a charge to the allowance for probable loan losses, if necessary. Any subsequent write-downs are charged against other non-interest expense. Other real estate owned totaled $69,872,000 and $85,879,000 at December 31, 2014 and 2013, respectively. Other real estate owned is included in other assets.
	Bank Premises and Equipment
	Bank premises and equipment are stated at cost less accumulated depreciation. Depreciation is computed on straight-line and accelerated methods over the estimated useful lives of the assets. Repairs and maintenance are charged to operations as incurred and expenditures for renewals and betterments are capitalized.
	Other Investments
	Other investments include equity investments in non-financial companies, bank owned life insurance, as well as equity securities with no readily determinable fair market value. Equity investments are accounted for using the equity method of accounting. Equity securities with no readily determinable fair value are accounted for using the cost method.
	Income Taxes
	Deferred income tax assets and liabilities are determined using the asset and liability method. Under this method, the net deferred tax asset or liability is determined based on the tax effects of the differences between the book and tax basis of the various balance sheet assets and liabilities and gives current recognition to changes in tax rates and laws. The Company files a consolidated federal income tax return with its subsidiaries.
	Recognition of deferred tax assets is based on management's assessment that the benefit related to certain temporary differences, tax operating loss carry forwards, and tax credits are more likely than not to be realized. A valuation allowance is recorded for the amount of the deferred tax items for which it is more likely than not that the tax benefits will not be realized.
	The Company evaluates uncertain tax positions at the end of each reporting period. The Company may recognize the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefit recognized in the financial statements from any such a position is measured based on the largest benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. As of December 31, 2014 and 2013, respectively, after evaluating all uncertain tax positions, the Company has recorded no liability for unrecognized tax benefits at the end of the reporting period. The Company would recognize any interest accrued on unrecognized tax benefits as other interest expense and penalties as other non-interest expense. During the years ended December 31, 2014, 2013 and 2012, the Company recognized no interest expense or penalties related to uncertain tax positions.
	The Company files consolidated tax returns in the U.S. Federal jurisdiction and various state jurisdictions. The Company is no longer subject to U.S. federal or state income tax examinations by tax authorities for years before 2011.
	Stock Options
	Compensation expense for stock awards is based on the market price of the stock on the measurement date, which is generally the date of grant, and is recognized ratably over the service period of the award. The fair value of stock options granted was estimated, using the Black-Sholes-Merton option-pricing model. This model was developed for use in estimating the fair value of publicly traded options that have no vesting restrictions and are fully transferable. Additionally, the model requires the input of highly subjective assumptions. Because the Company's employee stock options have characteristics significantly different from those of publicly traded options, and because changes in the subjective input assumptions can materially affect the fair value estimate, in management's opinion, the Black-Scholes-Merton option-pricing model does not necessarily provide a reliable single measure of the fair value of the Company's stock options.
	Net Income Per Share
	Basic Earnings Per Share ("EPS") is calculated by dividing net income by the weighted average number of common shares outstanding. The computation of diluted EPS assumes the issuance of common shares for all dilutive potential common shares outstanding during the reporting period. The dilutive effect of stock options is considered in earnings per share calculations, if dilutive, using the treasury stock method.
	Goodwill and Identified Intangible Assets
	Goodwill represents the excess of costs over fair value of assets of businesses acquired. Goodwill is tested for impairment at least annually or on an interim basis if an event triggering impairment may have occurred. As of October 1, 2014, after completing goodwill testing, the Company has determined that no goodwill impairment exists.
	Identified intangible assets are acquired assets that lack physical substance but can be distinguished from goodwill because of contractual or other legal rights or because the asset is capable of being sold or exchanged either on its own or in combination with a related contract, asset, or liability. The Company's identified intangible assets relate to core deposits and contract rights. As of December 31, 2014, the Company has determined that no impairment of identified intangibles exists. Identified intangible assets with definite useful lives are amortized on an accelerated basis over their estimated life. See Note 6—Goodwill and Other Intangible Assets.
	Impairment of Long-Lived Assets
	Long-lived assets, such as property, plant and equipment, and purchased intangibles subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying value of the asset to the estimated undiscounted future cash flows expected to be generated by the asset. If the carrying value of an asset exceeds its estimated future cash flows, an impairment charge is recognized by the amount by which the carrying value of the asset exceeds the fair value of the asset. Assets to be disposed of would be separately presented in the statement of condition and reported at the lower of the carrying value or fair value less costs to sell, and are no longer depreciated. The assets and liabilities of a disposed group classified as held for sale would be presented separately in the appropriate asset and liability sections of the statement of condition.
	Consolidated Statements of Cash Flows
	For purposes of the consolidated statements of cash flows, the Company considers all short-term investments with a maturity at date of purchase of three months or less to be cash equivalents. Also, the Company reports transactions related to deposits and loans to customers on a net basis.
	Accounting for Transfers and Servicing of Financial Assets
	The Company accounts for transfers and servicing of financial assets and extinguishments of liabilities based on the application of a financial-components approach that focuses on control. After a transfer of financial assets, the Company recognizes the financial and servicing assets it controls and liabilities it has incurred, derecognizes financial assets when control has been surrendered and derecognizes liabilities when extinguished. The Company has retained mortgage servicing rights in connection with the sale of mortgage loans. Because the Company may not initially identify loans as originated for resale, all loans are initially treated as held for investment. The value of the mortgage servicing rights are reviewed periodically for impairment and are amortized in proportion to, and over the period of estimated net servicing income or net servicing losses. The value of the mortgage servicing rights is not significant to the consolidated statements of condition.
	Segments of an Enterprise and Related Information
	The Company operates as one segment. The operating information used by the Company's chief executive officer for purposes of assessing performance and making operating decisions about the Company is the consolidated financial statements presented in this report. The Company has four active operating subsidiaries, namely, the bank subsidiaries, otherwise known as International Bank of Commerce, Laredo, Commerce Bank, International Bank of Commerce, Zapata and International Bank of Commerce, Brownsville. The Company applies the provisions of ASC Topic 280, "Segment Reporting," in determining its reportable segments and related disclosures.
	Comprehensive Income (Loss)
	Comprehensive income (loss) consists of net income and other comprehensive income (loss). Other comprehensive income (loss) includes unrealized gains and losses on securities available for sale.
	Advertising
	Advertising costs are expensed as incurred.
	Reclassifications
	Certain amounts in the prior year's presentations have been reclassified to conform to the current presentation. These reclassifications had no effect on previously reported net income or shareholders' equity.
	New Accounting Standards
	In February 2013, the Financial Accounting Standards Board issued Accounting Standards Update No. 2013-02 to ASC 220, "Comprehensive Income." The update amends existing literature to require an entity to provide information about the amounts reclassified out of other comprehensive income by component, and it also requires enhanced disclosure and cross reference on items reclassified out of accumulated other comprehensive income during the reporting period. The update is effective for reporting periods beginning after December 15, 2012. The adoption of the update to existing standards did not have a significant impact to the Company's consolidated financial statements.
	In July 2013, the Financial Accounting Standards Board issued Accounting Standards Update No. 2013-11 to ASC 740, "Income Taxes." The update amends existing literature to eliminate diversity in practice in the presentation of unrecognized tax benefits in instances where a net operating loss carryforward, a similar tax loss or a tax credit carryforward also exist. The update clarifies how the unrecognized tax benefit should be presented in those situations where other tax losses or tax credit carryforwards exist. The update does not change the currently required disclosures for unrecognized tax benefits under current ASC 740 guidance. The update is effective for fiscal years and interim periods within those years beginning after December 15, 2013. The adoption of the update to existing standards did not have a significant impact to the Company's consolidated financial statements.
	In January 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-01 to ASC 323-70, "Investments—Equity Method and Joint Ventures—Accounting for Investments in Qualified Affordable Housing Project." The update issues new guidance for investments in qualified affordable housing projects which permits entities to elect to apply the proportional amortization method to account for the investment when certain conditions are met. The update is effective for public entities for annual and interim periods beginning after December 15, 2014 and is able to be applied retrospectively. The adoption of the update is not expected to have a significant impact to the Company's consolidated financial statements.
	In January 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-04 to ASC 310-40, "Receivables—Troubled Debt Restructurings by Creditors." The update amends existing literature to eliminate diversity in practice by clarifying and defining when an in substance repossession or foreclosure occurs. The terms "in substance repossession or foreclosure" and "physical possession" are not currently defined in the accounting literature, resulting in diversity in practice when a creditor derecognizes a loan receivable and recognizes the real estate property collateralizing the loan receivable as an asset. Additionally, the update requires interim and annual disclosures of both the amount of foreclosed residential real estate property and the recorded investment in consumer mortgage loans collateralized by residential real estate property that are in the process of foreclosure. The update is effective for annual periods and the interim periods within those annual periods beginning after December 15, 2014. The adoption of the update to existing standards is not expected to have a significant impact to the Company's consolidated financial statements.
	In April 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-08 to ASC 205, "Presentation of Financial Statements," and ASC 360, "Property, Plant and Equipment." The update to existing standards change the requirements for reporting discontinued operations, primarily by clarifying that the disposal of a component or group of components of an entity could constitute discontinued operations under certain circumstances. The update also defines required information in disclosures about discontinued operations, including a discussion of the entity's continued involvement in the discontinued operation, if any. The update is applicable to all disposals of components of an entity that occurred within interim and annual periods beginning after December 15, 2014 and for acquisitions that are classified as held for sale for interim and annual periods beginning after December 15, 2014. The adoption of the update is not expected to have a significant impact to the Company's consolidated financial statements.
	In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-09 to ASC 606, "Revenue from Contracts with Customers." The update sets a common standard that defines revenue and the principles for recognizing revenue. The update outlines when an entity should recognize revenue, among other matters. At its core, the update states that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The update also outlines the steps that entities should take to determine and record the correct revenue number. The update is effective for annual periods beginning after December 15, 2016 and the interim periods within that reporting period. The Company is evaluating the potential impact to the Company's consolidated financial statements.
In June 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-11 to ASC 860, "Transfers and Servicing." The update amends existing standards to require that repurchase-to-maturity transactions be accounted for as secured borrowings, in line with accounting standards for other similar instruments. Additionally, the update requires various disclosures including information regarding transfers accounted for as sales in transactions that are economically similar as repurchase agreements, in addition to disclosures related to collateral, remaining contractual tenor and a discussion of the potential risks associated with repurchase agreements, securities lending transactions and repurchase-to-maturity transactions. The update is effective for interim and annual periods beginning after December 15, 2014. The adoption of the update to existing standards is not expected to have a significant impact to the Company's consolidated financial statements.
In August 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-14 to ASC 310-40, "Receivables—Troubled Debt Restructurings by Creditors." The update is new guidance regarding classification and measurement of foreclosed mortgage loans that are government guaranteed. The update specifies that government secured mortgage loans foreclosed upon should be classified as other assets and measured based on the amount of the loan balance that is expected to be recovered from the guarantor. The new guidance is effective for interim and annual periods after December 15, 2014. The adoption of the update is not expected to have a significant impact to the Company's consolidated financial statements.
In January 2015, the Financial Accounting Standards Board issued Accounting Standards Update No. 2015-01 to ASC 225-20, "Income Statement- Extraordinary and Unusual Items." The update amends existing standards and is being issued as part of the FASB's initiative to reduce complexity in accounting standards. The update eliminates the concept of extraordinary items. The update is effective for interim and annual periods after December 15, 2015. The adoption of the update to existing standards is not expected to have a significant impact to the Company's consolidated financial statements.
In February 2015, the Financial Accounting Standards Board issued Accounting Standards Update No. 2015-02 to ASC 810, "Consolidation." The update amends existing standards regarding the evaluation of certain legal entities and their consolidation in the financial statements. The amendments modify the evaluation process to assess whether limited partnerships and similar legal entities are variable interest entities or voting interest entities, eliminate the presumption that a general partner should consolidate a limited partnership, affect the consolidation analysis of entities that are involved in variable interest entities, particularly those that have fee arrangements and related party relationships and provides a scope exception for reporting entities with legal interests that are required to comply with or operate in accordance with requirements that are similar to those in Rule 2a-7 of the Investment Company Act of 1940 for registered money market funds. The update is effective for interim and annual periods after December 15, 2015. The Company is evaluating the impact of the adoption of the update.

Investment_Securities

Investment Securities	12 Months Ended
	Dec. 31, 2014
Investment Securities
Investment Securities	(2) Investment Securities
	The amortized cost and estimated fair value by type of investment security at December 31, 2014 are as follows:
			Held to Maturity
			Amortized		Gross			Gross			Estimated			Carrying
			cost		unrealized			unrealized			fair value			value
					gains			losses
			(Dollars in Thousands)
	Other securities		$	2,400	$	—		$	—		$	2,400		$	2,400
	Total investment securities		$	2,400	$	—		$	—		$	2,400		$	2,400
			Available for Sale
			Amortized		Gross			Gross			Estimated			Carrying
			cost		unrealized			unrealized			fair value			value(1)
					gains			losses
			(Dollars in Thousands)
	Residential mortgage-backed securities		$	4,597,590	$	47,960		$	(45,178	)	$	4,600,372		$	4,600,372
	Obligations of states and political subdivisions			268,763		19,131			(5,618	)		282,276			282,276
	Other debt securities			20,000		—			—			20,000			20,000
	Equity securities			28,075		1,425			(185	)		29,315			29,315
	Total investment securities		$	4,914,428	$	68,516		$	(50,981	)	$	4,931,963		$	4,931,963
	-1	Included in the carrying value of residential mortgage-backed securities are $1,503,774 of mortgage-backed securities issued by Ginnie Mae, $3,072,535 of mortgage-backed securities issued by Fannie Mae and Freddie Mac and $24,063 issued by non-government entities
	The amortized cost and estimated fair value of investment securities at December 31, 2014, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to prepay obligations with or without prepayment penalties.
			Held to Maturity					Available for Sale
			Amortized		Estimated			Amortized			Estimated
			Cost		fair value			Cost			fair value
			(Dollars in Thousands)
	Due in one year or less		$	1,075	$	1,075		$	—		$	—
	Due after one year through five years			1,325		1,325			—			—
	Due after five years through ten years			—		—			735			812
	Due after ten years			—		—			288,028			301,464
	Residential mortgage-backed securities			—		—			4,597,590			4,600,372
	Equity securities			—		—			28,075			29,315
	Total investment securities		$	2,400	$	2,400		$	4,914,428		$	4,931,963
	The amortized cost and estimated fair value by type of investment security at December 31, 2013 are as follows:
			Held to Maturity
			Amortized		Gross			Gross			Estimated			Carrying
			cost		unrealized			unrealized			fair value			value
					gains			losses
			(Dollars in Thousands)
	Other securities		$	2,400	$	—		$	—		$	2,400		$	2,400
	Total investment securities		$	2,400	$	—		$	—		$	2,400		$	2,400
			Available for Sale
			Amortized		Gross			Gross			Estimated			Carrying
			cost		unrealized			unrealized			fair value			value(1)
					gains			losses
			(Dollars in Thousands)
	Residential mortgage-backed securities		$	5,096,165	$	56,110		$	(124,574	)	$	5,027,701		$	5,027,701
	Obligations of states and political subdivisions			248,354		8,063			(8,007	)		248,410			248,410
	Equity securities			28,075		931			(538	)		28,468			28,468
	Total investment securities		$	5,372,594	$	65,104		$	(133,119	)	$	5,304,579		$	5,304,579
	-1	Included in the carrying value of residential mortgage-backed securities are $1,799,807 of mortgage-backed securities issued by Ginnie Mae, $3,200,042 of mortgage-backed securities issued by Fannie Mae and Freddie Mac and $27,852 issued by non-government entities
	Residential mortgage-backed securities are securities issued by Freddie Mac, Fannie Mae, Ginnie Mae or non-government entities. Investments in residential mortgage-backed securities issued by Ginnie Mae are fully guaranteed by the U.S. Government. Investments in mortgage-backed securities issued by Freddie Mac and Fannie Mae are not fully guaranteed by the U.S. Government, however, the Company believes that the quality of the bonds is similar to other AAA rated bonds with limited credit risk, particularly given the placement of Fannie Mae and Freddie Mac into conservatorship by the federal government in early September 2008 and because securities issued by others that are collateralized by residential mortgage-backed securities issued by Fannie Mae and Freddie Mac are rated consistently as AAA rated securities.
	The amortized cost and fair value of available for sale investment securities pledged to qualify for fiduciary powers, to secure public monies as required by law, repurchase agreements and short-term fixed borrowings was $2,182,579,000 and $2,196,169,000, respectively, at December 31, 2014.
	Proceeds from the sale and call of securities available-for-sale were $621,588,000, $178,123,000 and $1,382,231,000 during 2014, 2013 and 2012, respectively, which amounts included $620,933,000, $177,623,000 and $1,338,723,000 of mortgage-backed securities. Gross gains of $9,479,000, $9,601,000 and $38,447,000 and gross losses of $8,196,000, $0 and $1,000 were realized on the sales in 2014, 2013 and 2012, respectively.
	Gross unrealized losses on investment securities and the fair value of the related securities, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at December 31, 2014 were as follows:
			Less than 12 months					12 months or more						Total
			Fair Value		Unrealized			Fair Value			Unrealized			Fair Value		Unrealized
					Losses						Losses					Losses
			(Dollars in Thousands)
	Available for sale:
	Residential mortgage-backed securities		$	808,072	$	(4,910	)	$	1,836,218		$	(40,268	)	$	2,644,290	$	(45,178	)
	Obligations of states and political subdivisions			8,833		(97	)		27,793			(5,521	)		36,626		(5,618	)
	Equity securities			74		(1	)		8,066			(184	)		8,140		(185	)
			$	816,979	$	(5,008	)	$	1,872,077		$	(45,973	)	$	2,689,056	$	(50,981	)
	Gross unrealized losses on investment securities and the fair value of the related securities, aggregated by investment category and length of time that individual securities have been in a continuous loss position, at December 31, 2013 were as follows:
		Less than 12 months					12 months or more						Total
		Fair Value		Unrealized			Fair Value			Unrealized			Fair Value		Unrealized
				Losses						Losses					Losses
		(Dollars in Thousands)
Available for sale:
Residential mortgage-backed securities		$	2,459,565	$	(98,022	)	$	420,262		$	(26,552	)	$	2,879,827	$	(124,574	)
Obligations of states and political subdivisions			55,327		(3,025	)		14,292			(4,982	)		69,619		(8,007	)
Equity securities			19,462		(538	)		—			—			19,462		(538	)
		$	2,534,354	$	(101,585	)	$	434,554		$	(31,534	)	$	2,968,908	$	(133,119	)
The unrealized losses on investments in residential mortgage-backed securities are primarily caused by changes in market interest rates. Residential mortgage-backed securities are primarily securities issued by Freddie Mac, Fannie Mae and Ginnie Mae. The contractual cash obligations of the securities issued by Ginnie Mae are fully guaranteed by the U.S. Government. The contractual cash obligations of the securities issued by Freddie Mac and Fannie Mae are not fully guaranteed by the U.S. Government; however, the Company believes that the quality of the bonds is similar to other AAA rated bonds with limited credit risk, particularly given the placement of Fannie Mae and Freddie Mac into conservatorship by the federal government in early September 2008 and because securities issued by others that are collateralized by residential mortgage-backed securities issued by Fannie Mae and Freddie Mac are rated consistently as AAA rated securities. The decrease in fair value on residential mortgage-backed securities issued by Freddie Mac, Fannie Mae and Ginnie Mae is due to market interest rates. The Company has no intent to sell and will more than likely not be required to sell before a market price recovery or maturity of the securities; therefore, it is the conclusion of the Company that the investments in residential mortgage-backed securities issued by Freddie Mac, Fannie Mae and Ginnie Mae are not considered other-than-temporarily impaired. In addition, the Company has a small investment in non-agency residential mortgage-backed securities that have strong credit backgrounds and include additional credit enhancements to protect the Company from losses arising from high foreclosure rates. These securities have additional market volatility beyond economically induced interest rate events. It is the conclusion of the Company that the investments in non-agency residential mortgage-backed securities are other-than-temporarily impaired due to both credit and other than credit issues. An impairment charge of $817,000 ($531,050, after tax), was recorded in 2014 on the non-agency residential mortgage backed securities. Impairment charges of $1,374,000 ($893,100, after tax) and $1,039,000 ($675,000, after tax) were recorded in 2013 and 2012, respectively on the non-agency residential mortgage backed securities. The impairment charges represent the credit related impairment on the securities.
The unrealized losses on investments in other securities are caused by fluctuations in market interest rates. The underlying cash obligations of the securities are guaranteed by the entity underwriting the debt instrument. It is the belief of the Company that the entity issuing the debt will honor its interest payment schedule, as well as the full debt at maturity. The securities are purchased by the Company for their economic value. The decrease in fair value is primarily due to market interest rates and not other factors, and because the Company has no intent to sell and will more than likely not be required to sell before a market price recovery or maturity of the securities, it is the conclusion of the Company that the investments are not considered other-than-temporarily impaired.
The following table presents a reconciliation of credit-related impairment charges on available-for-sale investments recognized in earnings for the twelve months ended December 31, 2014 (in Thousands):
Balance at December 31, 2013		$	11,806
Impairment charges recognized during period			817
Balance at December 31, 2014		$	12,623
The following table presents a reconciliation of credit-related impairment charges on available-for-sale investments recognized in earnings for the twelve months ended December 31, 2013 (in Thousands):
Balance at December 31, 2012		$	10,432
Impairment charges recognized during period			1,374
Balance at December 31, 2013		$	11,806
The following table presents a reconciliation of credit-related impairment charges on available-for-sale investments recognized in earnings for the twelve months ended December 31, 2012 (in Thousands):
Balance at December 31, 2011		$	9,393
Impairment charges recognized during period			1,039
Balance at December 31, 2012		$	10,432

Loans

Loans	12 Months Ended
	Dec. 31, 2014
Loans
Loans	(3) Loans
	A summary of loans, by loan type at December 31, 2014 and 2013 is as follows:
		December 31,		December 31,
		2014		2013
		(Dollars in Thousands)
	Commercial, financial and agricultural	$	3,107,584	$	2,894,779
	Real estate—mortgage		910,326		847,692
	Real estate—construction		1,414,977		1,208,508
	Consumer		61,137		66,414
	Foreign		185,221		181,842
	Total loans	$	5,679,245	$	5,199,235

Allowance_for_Probable_Loan_Lo

Allowance for Probable Loan Losses	12 Months Ended
	Dec. 31, 2014
Allowance for Probable Loan Losses
Allowance for Probable Loan Losses	(4) Allowance for Probable Loan Losses
	The allowance for probable loan losses primarily consists of the aggregate loan loss allowances of the bank subsidiaries. The allowances are established through charges to operations in the form of provisions for probable loan losses. Loan losses or recoveries are charged or credited directly to the allowances. The allowance for probable loan losses of each bank subsidiary is maintained at a level considered appropriate by management, based on estimated probable losses in the loan portfolio. The allowance for probable loan losses is derived from the following elements: (i) allowances established on specific impaired loans, which are based on a review of the individual characteristics of each loan, including the customer's ability to repay the loan, the underlying collateral values, and the industry in which the customer operates, (ii) allowances based on actual historical loss experience for similar types of loans in the Company's loan portfolio, and (iii) allowances based on general economic conditions, changes in the mix of loans, company resources, border risk and credit quality indicators, among other things. All segments of the loan portfolio continue to be impacted by the prolonged economic downturn. Loans secured by real estate could be impacted negatively by the continued economic environment and resulting decrease in collateral values. Consumer loans may be impacted by continued and prolonged unemployment rates.
	The Company's management continually reviews the allowance for loan losses of the bank subsidiaries using the amounts determined from the allowances established on specific impaired loans, the allowance established on quantitative historical loss percentages, and the allowance based on qualitative data to establish an appropriate amount to maintain in the Company's allowance for loan losses. Should any of the factors considered by management in evaluating the adequacy of the allowance for probable loan losses change, the Company's estimate of probable loan losses could also change, which could affect the level of future provisions for probable loan losses. While the calculation of the allowance for probable loan losses utilizes management's best judgment and all information available, the adequacy of the allowance is dependent on a variety of factors beyond the Company's control, including, among other things, the performance of the entire loan portfolio, the economy, changes in interest rates and the view of regulatory authorities towards loan classifications.
	The loan loss provision is determined using the following methods. On a weekly basis, loan past due reports are reviewed by the credit quality committee to determine if a loan has any potential problems and if a loan should be placed on the Company's internal classified report. Additionally, the Company's credit department reviews the majority of the Company's loans for proper internal classification purposes regardless of whether they are past due and segregates any loans with potential problems for further review. The credit department will discuss the potential problem loans with the servicing loan officers to determine any relevant issues that were not discovered in the evaluation. Also, an analysis of loans that is provided through examinations by regulatory authorities is considered in the review process. After the above analysis is completed, the Company will determine if a loan should be placed on an internal classified report because of issues related to the analysis of the credit, credit documents, collateral and/or payment history.
	While the Texas and Oklahoma economies are performing better than other parts of the country, Texas and Oklahoma are not completely immune to the problems associated with the U.S. economy. The increase in income and capital gains taxes on certain individuals, the increase in payroll taxes, the recent substantial decrease in oil prices, and the unprecedented debt and large deficit of the United States not yet resolved, add uncertainty to the possibility of robust economic growth and may create an adverse effect on the economies of Texas and Oklahoma. Thus, the risk of loss associated with all segments of the loan portfolio in these markets continues to be impacted by prolonged economic uncertainty. Economic risk factors are minimized by the underwriting standards of the bank subsidiaries. The general underwriting standards encompass the following principles: (i) the financial strength of the borrower including strong earnings, a high net worth, significant liquidity and an acceptable debt to worth ratio, (ii) managerial and business competence, (iii) the ability to repay, (iv) for a new business, projected cash flows, (v) loan to value, (vi) in the case of a secondary guarantor, a guarantor financial statement, and (vii) financial and/or other character references. Although the underwriting standards reduce the risk of loss, unique risk factors exist in each type of loan in which the bank subsidiaries invest.
	Commercial and industrial loans are mostly secured by the collateral pledged by the borrower that are directly related to the business activities of the company such as accounts receivable and inventory. The ability of the borrower to collect accounts receivable, and to turn inventory into sales are risk factors in the repayment of the loan.
	Construction and land development loans can carry risk of repayment when projects incur cost overruns, have an increase in the price of building materials, encounter zoning and environmental issues, or encounter other factors that may affect the completion of a project on time and on budget. Additionally, repayment risk may be negatively impacted when the market experiences a deterioration in the value of real estate. Risks specifically related to 1-4 family development loans also include the practice by the mortgage industry of more restrictive underwriting standards, which inhibits the buyer from obtaining long term financing and excessive housing and lot inventory in the market.
	Commercial real estate loans demonstrate a risk of repayment when market values deteriorate, the business experiences turnover in key management, the business has an inability to attract or keep occupancy levels stable, or when the market experiences an exit of a specific business industry that is significant to the local economy, such as a manufacturing plant.
	First and second lien residential 1-4 family mortgage and consumer loan repayments may be affected by unemployment or underemployment and deteriorating market values of real estate.
	A summary of the changes in the allowance for probable loan losses by loan class is as follows:
		December 31, 2014
		Domestic																					Foreign
		Commercial			Commercial			Commercial			Commercial			Residential:			Residential:			Consumer			Foreign			Total
					real estate:			real estate:			real estate:			first lien			junior lien
					other			farmland &			multifamily
					construction &			commercial
					land
					development
		(Dollars in Thousands)
	Balance at December 31,	$	22,433		$	12,541		$	24,467		$	776		$	3,812		$	4,249		$	750		$	1,133		$	70,161
	Losses charge to allowance		(19,110	)		(680	)		(1,893	)		—			(351	)		(661	)		(719	)		(51	)		(23,465	)
	Recoveries credited to allowance		2,979			72			107			—			49			242			210			50			3,709
	Net losses charged to allowance		(16,131	)		(608	)		(1,786	)		—			(302	)		(419	)		(509	)		(1	)		(19,756	)
	Provision (credit) charged to operations		16,050			1,022			(3,998	)		70			79			853			419			(72	)		14,423
	Balance at December 31,	$	22,352		$	12,955		$	18,683		$	846		$	3,589		$	4,683		$	660		$	1,060		$	64,828
		December 31, 2013
		Domestic																					Foreign
		Commercial			Commercial			Commercial			Commercial			Residential:			Residential:			Consumer			Foreign			Total
					real estate:			real estate:			real estate:			first lien			junior lien
					other			farmland &			multifamily
					construction &			commercial
					land
					development
		(Dollars in Thousands)
	Balance at December 31,	$	11,632		$	12,720		$	21,880		$	694		$	4,390		$	4,448		$	1,289		$	1,140		$	58,193
	Losses charge to allowance		(11,737	)		(278	)		(600	)		(5	)		(632	)		(620	)		(561	)		(22	)		(14,455	)
	Recoveries credited to allowance		2,690			87			152			—			61			298			162			5			3,455
	Net losses charged to allowance		(9,047	)		(191	)		(448	)		(5	)		(571	)		(322	)		(399	)		(17	)		(11,000	)
	Provision (credit) charged to operations		19,848			12			3,035			87			(7	)		123			(140	)		10			22,968
	Balance at December 31,	$	22,433		$	12,541		$	24,467		$	776		$	3,812		$	4,249		$	750		$	1,133		$	70,161
		December 31, 2012
		Domestic																					Foreign
		Commercial			Commercial			Commercial			Commercial			Residential:			Residential:			Consumer			Foreign			Total
					real estate:			real estate:			real estate:			first lien			junior lien
					other			farmland &			multifamily
					construction &			commercial
					land
					development
		(Dollars in Thousands)
	Balance at December 31,	$	26,617		$	19,940		$	24,227		$	1,003		$	4,562		$	4,760		$	1,724		$	1,359		$	84,192
	Losses charge to allowance		(34,721	)		(7,617	)		(13,724	)		—			(227	)		(1,190	)		(756	)		(111	)		(58,346	)
	Recoveries credited to allowance		3,547			229			220			—			13			195			184			—			4,388
	Net losses charged to allowance		(31,174	)		(7,388	)		(13,504	)		—			(214	)		(995	)		(572	)		(111	)		(53,958	)
	Provision (credit) charged to operations		16,189			168			11,157			(309	)		42			683			137			(108	)		27,959
	Balance at December 31,	$	11,632		$	12,720		$	21,880		$	694		$	4,390		$	4,448		$	1,289		$	1,140		$	58,193
	The allowance for probable loan losses is a reserve established through a provision for probable loan losses charged to expense, which represents management's best estimate of probable loan losses when evaluating loans (i) individually or (ii) collectively. The Company's allowance for probable loan losses decreased for the year ended December 31, 2014 primarily due to a charge down of a relationship that is mainly secured by multiple pieces of transportation equipment. The relationship also contributed to a change in net losses charged against the allowance for probable loan losses for the same period.
	The table below provides additional information on the balance of loans individually or collectively evaluated for impairment and their related allowance, by loan class:
		December 31, 2014
		Loans individually						Loans collectively
		evaluated for						evaluated for
		impairment						impairment
		Recorded			Allowance			Recorded			Allowance
		Investment						Investment
		(Dollars in Thousands)
Domestic
Commercial	$	40,175		$	9,112		$	1,049,311		$	13,240
Commercial real estate: other construction & land development		10,876			1,890			1,404,101			11,065
Commercial real estate: farmland & commercial		14,166			1,219			1,887,233			17,464
Commercial real estate: multifamily		835			—			115,864			846
Residential: first lien		5,840			—			416,186			3,589
Residential: junior lien		2,895			—			485,405			4,683
Consumer		1,384			—			59,753			660
Foreign		—			—			185,221			1,060
Total	$	76,171		$	12,221		$	5,603,074		$	52,607
	December 31, 2013
	Loans individually						Loans collectively
	evaluated for						evaluated for
	impairment						impairment
	Recorded			Allowance			Recorded			Allowance
	Investment						Investment
	(Dollars in Thousands)
Domestic
Commercial	$	34,183		$	12,234		$	1,008,459		$	10,199
Commercial real estate: other construction & land development		13,976			852			1,194,532			11,689
Commercial real estate: farmland & commercial		16,038			2,916			1,734,001			21,551
Commercial real estate: multifamily		295			—			101,803			776
Residential: first lien		6,153			—			432,309			3,812
Residential: junior lien		3,206			—			406,024			4,249
Consumer		1,606			—			64,808			750
Foreign		436			—			181,406			1,133
Total	$	75,893		$	16,002		$	5,123,342		$	54,159
Loans accounted for on a non-accrual basis at December 31, 2014, 2013 and 2012 amounted to $63,559,000, $62,823,000 and $71,768,000, respectively. The effect of such non-accrual loans reduced interest income by $4,013,000, $4,088,000 and $2,549,000 for the years ended December 31, 2014, 2013 and 2012, respectively. Amounts received on non-accruals are applied, for financial accounting purposes, first to principal and then to interest after all principal has been collected. Accruing loans contractually past due 90 days or more as to principal or interest payments at December 31, 2014, 2013 and 2012 amounted to $9,988,000, $7,197,000 and $15,033,000, respectively.
The table below provides additional information on loans accounted for on a non-accrual basis by loan class:
	December 31,
	2014			2013
	(Dollars in Thousands)
Domestic
Commercial	$	40,121		$	34,110
Commercial real estate: other construction & land development		8,621			11,726
Commercial real estate: farmland & commercial		11,903			13,775
Commercial real estate: multifamily		835			295
Residential: first lien		527			1,266
Residential: junior lien		1,523			1,576
Consumer		29			75
Foreign		—			—
Total non-accrual loans	$	63,559		$	62,823
Impaired loans are those loans where it is probable that all amounts due according to contractual terms of the loan agreement will not be collected. The Company has identified these loans through its normal loan review procedures. Impaired loans are measured based on (1) the present value of expected future cash flows discounted at the loan's effective interest rate; (2) the loan's observable market price; or (3) the fair value of the collateral if the loan is collateral dependent. Substantially all of the Company's impaired loans are measured at the fair value of the collateral. In limited cases the Company may use other methods to determine the level of impairment of a loan if such loan is not collateral dependent. The increase in commercial non-accrual loans at December 31, 2014 compared to December 31, 2013 is mainly due to the addition of a relationship secured by accounts receivables.
The following tables detail key information regarding the Company's impaired loans by loan class for the year ended December 31, 2014:
	December 31, 2014
	Recorded			Unpaid			Related			Average			Interest
	Investment			Principal			Allowance			Recorded			Recognized
				Balance						Investment
	(Dollars in Thousands)
Loans with Related Allowance
Domestic
Commercial	$	19,944		$	20,026		$	9,112		$	19,313		$	—
Commercial real estate: other construction & land development		6,714			6,949			1,890			7,183			—
Commercial real estate: farmland & commercial		5,107			5,257			1,219			6,790			92
Total impaired loans with related allowance	$	31,765		$	32,232		$	12,221		$	33,286		$	92
	December 31, 2014
	Recorded			Unpaid			Average			Interest
	Investment			Principal			Recorded			Recognized
				Balance			Investment
	(Dollars in Thousands)
Loans with No Related Allowance
Domestic
Commercial	$	20,231		$	20,260		$	18,563		$	4
Commercial real estate: other construction & land development		4,162			4,270			4,882			74
Commercial real estate: farmland & commercial		9,059			10,562			8,664			—
Commercial real estate: multifamily		835			835			363			—
Residential: first lien		5,840			6,034			6,293			273
Residential: junior lien		2,895			2,915			3,035			90
Consumer		1,384			1,386			1,402			3
Foreign		—			—			—			—
Total impaired loans with no related allowance	$	44,406		$	46,262		$	43,202		$	444
The following tables detail key information regarding the Company's impaired loans by loan class for the year ended December 31, 2013:
	December 31, 2013
	Recorded			Unpaid			Related			Average			Interest
	Investment			Principal			Allowance			Recorded			Recognized
				Balance						Investment
	(Dollars in Thousands)
Loans with Related Allowance
Domestic
Commercial	$	17,178		$	17,177		$	12,234		$	18,019		$	38
Commercial real estate: other construction & land development		6,818			6,825			852			6,058			—
Commercial real estate: farmland & commercial		7,259			10,697			2,916			7,167			92
Total impaired loans with related allowance	$	31,255		$	34,699		$	16,002		$	31,244		$	130
	December 31, 2013
	Recorded			Unpaid			Average			Interest
	Investment			Principal			Recorded			Recognized
				Balance			Investment
	(Dollars in Thousands)
Loans with No Related Allowance
Domestic
Commercial	$	17,005		$	17,023		$	16,778		$	2
Commercial real estate: other construction & land development		7,158			7,187			18,164			74
Commercial real estate: farmland & commercial		8,779			9,949			7,313			—
Commercial real estate: multifamily		295			295			322			—
Residential: first lien		6,153			6,258			4,860			179
Residential: junior lien		3,206			3,226			2,347			99
Consumer		1,606			1,612			1,380			1
Foreign		436			436			452			19
Total impaired loans with no related allowance	$	44,638		$	45,986		$	51,616		$	374
A portion of the impaired loans have adequate collateral and credit enhancements not requiring a related allowance for loan loss. The level of impaired loans is reflective of the economic weakness that has been created by the financial crisis and the subsequent economic downturn. Management is confident the Company's loss exposure regarding these credits will be significantly reduced due to the Company's long-standing practices that emphasize secured lending with strong collateral positions and guarantor support. Management is likewise confident the reserve for probable loan losses is adequate. The Company has no direct exposure to sub-prime loans in its loan portfolio, but the sub-prime crisis has affected the credit markets on a national level, and as a result, the Company has experienced an increasing amount of impaired loans; however, management's decision to place loans in this category does not necessarily mean that the Company will experience significant losses from these loans or significant increases in impaired loans from these levels.
Management of the Company recognizes the risks associated with these impaired loans. However, management's decision to place loans in this category does not necessarily mean that losses will occur. In the current environment, troubled loan management can be protracted because of the legal and process problems that delay the collection of an otherwise collectable loan. Additionally, management believes that the collateral related to these impaired loans and/or the secondary support from guarantors mitigates the potential for losses from impaired loans.
The following table details loans accounted for as "troubled debt restructuring," segregated by loan class. Loans accounted for as troubled debt restructuring are included in impaired loans.
	December 31,			December 31,
	2014			2013
	(Dollars in Thousands)
Domestic
Commercial	$	2,500		$	150
Commercial real estate: other construction & land development		2,254			8,860
Commercial real estate: farmland & commercial		2,861			2,863
Residential: first lien		5,313			4,887
Residential: junior lien		1,371			1,631
Consumer		1,354			1,531
Foreign		—			436
Total troubled debt restructuring	$	15,653		$	20,358
The bank subsidiaries charge off that portion of any loan which management considers to represent a loss as well as that portion of any other loan which is classified as a "loss" by bank examiners. Commercial and industrial or real estate loans are generally considered by management to represent a loss, in whole or part, when an exposure beyond any collateral coverage is apparent and when no further collection of the loss portion is anticipated based on the borrower's financial condition and general economic conditions in the borrower's industry. Generally, unsecured consumer loans are charged-off when 90 days past due.
While management of the Company considers that it is generally able to identify borrowers with financial problems reasonably early and to monitor credit extended to such borrowers carefully, there is no precise method of predicting loan losses. The determination that a loan is likely to be uncollectible and that it should be wholly or partially charged-off as a loss is an exercise of judgment. Similarly, the determination of the adequacy of the allowance for probable loan losses can be made only on a subjective basis. It is the judgment of the Company's management that the allowance for probable loan losses at December 31, 2014 was adequate to absorb probable losses from loans in the portfolio at that date.
The following table presents information regarding the aging of past due loans by loan class:
	December 31, 2014
	30 - 59			60 - 89			90 Days or			90 Days or			Total			Current			Total
	Days			Days			Greater			greater &			Past due						Portfolio
										still accruing
	(Dollars in Thousands)
Domestic
Commercial	$	4,103		$	2,665		$	40,665		$	2,890		$	47,433		$	1,042,053		$	1,089,486
Commercial real estate: other construction & land development		596			10			8,707			439			9,313			1,405,664			1,414,977
Commercial real estate: farmland & commercial		2,905			7,131			10,724			1,711			20,760			1,880,639			1,901,399
Commercial real estate: multifamily		351			—			856			21			1,207			115,492			116,699
Residential: first lien		5,895			1,864			4,267			3,901			12,026			410,000			422,026
Residential: junior lien		899			231			1,931			431			3,061			485,239			488,300
Consumer		896			216			507			482			1,619			59,518			61,137
Foreign		1,616			98			113			113			1,827			183,394			185,221
Total past due loans	$	17,261		$	12,215		$	67,770		$	9,988		$	97,246		$	5,581,999		$	5,679,245
The increase in loans past due 60 - 89 days at December 31, 2014 compared to December 31, 2013 is primarily due to one loan secured by farmland that was delinquent at year end.
	December 31, 2013
	30 - 59			60 - 89			90 Days or			90 Days or			Total			Current			Total
	Days			Days			Greater			greater &			Past due						Portfolio
										still accruing
	(Dollars in Thousands)
Domestic
Commercial	$	4,240		$	538		$	36,066		$	2,051		$	40,844		$	1,001,798		$	1,042,642
Commercial real estate: other construction & land development		1,042			—			9,942			62			10,984			1,197,524			1,208,508
Commercial real estate: farmland & commercial		6,216			520			6,990			417			13,726			1,736,313			1,750,039
Commercial real estate: multifamily		39			142			295			—			476			101,622			102,098
Residential: first lien		4,758			3,046			4,541			3,518			12,345			426,117			438,462
Residential: junior lien		606			198			1,900			368			2,704			406,526			409,230
Consumer		1,523			469			803			781			2,795			63,619			66,414
Foreign		1,467			417			—			—			1,884			179,958			181,842
Total past due loans	$	19,891		$	5,330		$	60,537		$	7,197		$	85,758		$	5,113,477		$	5,199,235
The Company's internal classified report is segregated into the following categories: (i) "Special Review Credits," (ii) "Watch List—Pass Credits," or (iii) "Watch List—Substandard Credits." The loans placed in the "Special Review Credits" category reflect the Company's opinion that the loans reflect potential weakness which require monitoring on a more frequent basis. The "Special Review Credits" are reviewed and discussed on a regular basis with the credit department and the lending staff to determine if a change in category is warranted. The loans placed in the "Watch List—Pass Credits" category reflect the Company's opinion that the credit contains weaknesses which represent a greater degree of risk, which warrant "extra attention." The "Watch List—Pass Credits" are reviewed and discussed on a regular basis with the credit department and the lending staff to determine if a change in category is warranted. The loans placed in the "Watch List—Substandard Credits" classification are considered to be potentially inadequately protected by the current sound worth and debt service capacity of the borrower or of any pledged collateral. These credit obligations, even if apparently protected by collateral value, have shown defined weaknesses related to adverse financial, managerial, economic, market or political conditions which may jeopardize repayment of principal and interest. Furthermore, there is the possibility that some future loss could be sustained by the Company if such weaknesses are not corrected. For loans that are classified as impaired, management evaluates these credits in accordance with the provisions of ASC 310-10, "Receivables," and, if deemed necessary, a specific reserve is allocated to the credit. The specific reserve allocated under ASC 310-10, is based on (i) the present value of expected future cash flows discounted at the loan's effective interest rate; (ii) the loan's observable market price; or (iii) the fair value of the collateral if the loan is collateral dependent. Substantially all of the Company's loans evaluated as impaired under ASC 310-10 are measured using the fair value of collateral method. In limited cases, the Company may use other methods to determine the specific reserve of a loan under ASC 310-10 if such loan is not collateral dependent.
The allowance based on historical loss experience on the Company's remaining loan portfolio, which includes the "Special Review Credits," "Watch List—Pass Credits," and "Watch List—Substandard Credits" is determined by segregating the remaining loan portfolio into certain categories such as commercial loans, installment loans, international loans, loan concentrations and overdrafts. Installment loans are then further segregated by number of days past due. A historical loss percentage, adjusted for (i) management's evaluation of changes in lending policies and procedures, (ii) current economic conditions in the market area served by the Company, (iii) other risk factors, (iv) the effectiveness of the internal loan review function, (v) changes in loan portfolios, and (vi) the composition and concentration of credit volume is applied to each category. Each category is then added together to determine the allowance allocated under ASC 450-20.
As discussed above and in line with its customary loan review process, the Company identified and re-classified a loan relationship in the commercial category to Special Review, causing an increase in that category at December 31, 2014 compared to December 31, 2013. Additionally, there was a decrease in the commercial real estate farmland and commercial Special Review category at December 31, 2014 compared to December 31, 2013 due to a relationship being reclassified to the Watch List-Substandard category during 2014. A construction and land development loan within the relationship was classified as Watch List-Substandard from pass during the same period. The decrease in commercial construction and land development Special Review credits at December 31, 2014 compared to December 31, 2013 can be attributed to a relationship that was paid off in 2014.
A summary of the loan portfolio by credit quality indicator by loan class is as follows:
				December 31, 2014
	Pass			Special			Watch			Watch List—			Watch List—
				Review			List—Pass			Substandard			Impaired
				(Dollars in Thousands)
Domestic
Commercial	$	961,490		$	38,382		$	3,793		$	45,646		$	40,175
Commercial real estate: other construction & land development		1,353,971			1,005			10,428			38,697			10,876
Commercial real estate: farmland & commercial		1,754,741			11,674			23,453			97,365			14,166
Commercial real estate: multifamily		115,729			—			—			135			835
Residential: first lien		412,668			3,500			—			18			5,840
Residential: junior lien		484,968			—			—			437			2,895
Consumer		59,622			—			—			131			1,384
Foreign		185,221			—			—			—			—
Total	$	5,328,410		$	54,561		$	37,674		$	182,429		$	76,171
				December 31, 2013
	Pass			Special			Watch			Watch List—			Watch List—
				Review			List—Pass			Substandard			Impaired
				(Dollars in Thousands)
Domestic
Commercial	$	955,522		$	2,270		$	4,389		$	46,278		$	34,183
Commercial real estate: other construction & land development		1,167,295			14,247			9,318			3,672			13,976
Commercial real estate: farmland & commercial		1,635,179			56,438			21,912			20,472			16,038
Commercial real estate: multifamily		100,948			—			—			855			295
Residential: first lien		432,067			122			—			120			6,153
Residential: junior lien		405,731			—			—			293			3,206
Consumer		64,808			—			—			—			1,606
Foreign		180,837			—			—			569			436
Total	$	4,942,387		$	73,077		$	35,619		$	72,259		$	75,893

Bank_Premises_and_Equipment

Bank Premises and Equipment	12 Months Ended
	Dec. 31, 2014
Bank Premises and Equipment
Bank Premises and Equipment	(5) Bank Premises and Equipment
	A summary of bank premises and equipment, by asset classification, at December 31, 2014 and 2013 were as follows:
		Estimated	2014			2013
		useful lives
			(Dollars in Thousands)
	Bank buildings and improvements	5 - 40 years	$	509,830		$	470,386
	Furniture, equipment and vehicles	1 - 20 years		269,861			260,932
	Land			125,414			128,805
	Real estate held for future expansion:
	Land, building, furniture, fixture and equipment	7 - 27 years		—			511
	Less: accumulated depreciation			(378,682	)		(355,792	)
	Bank premises and equipment, net		$	526,423		$	504,842

Goodwill_and_Other_Intangible_

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2014
Goodwill and Other Intangible Assets
Goodwill and Other Intangible Assets	(6) Goodwill and Other Intangible Assets
	The majority of the Company's identified intangibles are in the form of amortizable core deposit premium, with the exception of $501,000, which represents identified intangibles in the acquisition of the rights to the insurance agency contracts of InsCorp, Inc., acquired in 2008. Information on the Company's identified intangible assets follows:
		Carrying		Accumulated		Net
		Amount		Amortization
		(Dollars in Thousands)
	December 31, 2014:
	Core deposit premium		58,675		58,379		296
		$		$		$
	Identified intangible (contract rights)		2,022		1,521		501
	Total identified intangibles	$	60,697	$	59,900	$	797
	December 31, 2013:
	Core deposit premium		58,675		56,298		2,377
		$		$		$
	Identified intangible (contract rights)		2,022		1,213		809
	Total identified intangibles	$	60,697	$	57,511	$	3,186
	Amortization expense of intangible assets for the years ended December 31, 2014, 2013 and 2012, was $2,389,000, $4,633,000 and $4,651,000, respectively. Estimated amortization expense for each of the five succeeding fiscal years, and thereafter, is as follows:
	Fiscal year ending December 31:
		Total
		(in thousands)
	2015	$	452
	2016		295
	2017		25
	2018		25
	2019		—
	Thereafter		—
	Total	$	797
	There were no changes in the carrying amount of goodwill for the years ended December 31, 2014 and 2013.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2014
Deposits.
Deposits	(7) Deposits
	Deposits as of December 31, 2014 and 2013 and related interest expense for the years ended December 31, 2014, 2013 and 2012 were as follows:
		2014		2013
		(Dollars in Thousands)
	Deposits:
	Demand—non-interest bearing
	Domestic	$	2,382,935	$	2,175,694
	Foreign		547,318		490,816
	Total demand non-interest bearing		2,930,253		2,666,510
	Savings and interest bearing demand
	Domestic		2,488,458		2,364,905
	Foreign		537,222		560,707
	Total savings and interest bearing demand		3,025,680		2,925,612
	Time, certificates of deposit $100,000 or more
	Domestic		835,792		856,700
	Foreign		864,346		938,940
	Less than $100,000
	Domestic		482,089		531,503
	Foreign		300,465		324,160
	Total time, certificates of deposit		2,482,692		2,651,303
	Total deposits	$	8,438,625	$	8,243,425
		2014		2013		2012
		(Dollars in Thousands)
	Interest expense:
	Savings and interest bearing demand
	Domestic	$	2,998	$	3,182	$	4,487
	Foreign		599		580		801
	Total savings and interest bearing demand		3,597		3,762		5,288
	Time, certificates of deposit $100,000 or more
	Domestic		4,615		5,761		8,263
	Foreign		4,529		5,590		9,148
	Less than $100,000
	Domestic		2,074		3,065		4,945
	Foreign		815		1,028		1,617
	Total time, certificates of deposit		12,033		15,444		23,973
	Total interest expense on deposits	$	15,630	$	19,206	$	29,261
	Scheduled maturities of time deposits as of December 31, 2014 were as follows:
		Total
		(in thousands)
	2015	$	2,177,266
	2016		203,928
	2017		76,206
	2018		23,481
	2019		1,751
	Thereafter		60
	Total	$	2,482,692
	Scheduled maturities of time deposits in amounts of $100,000 or more at December 31, 2014, were as follows:
	Due within 3 months or less	$	631,083
	Due after 3 months and within 6 months		409,400
	Due after 6 months and within 12 months		443,860
	Due after 12 months		215,795
		$	1,700,138
	Time deposits that meet or exceed the FDIC insurance limit of $250,000 at December 31, 2014 and December 31, 2013 were $1,027,000 and $1,076,000, respectively.

Securities_Sold_Under_Repurcha

Securities Sold Under Repurchase Agreements	12 Months Ended
	Dec. 31, 2014
Securities Sold Under Repurchase Agreements
Securities Sold Under Repurchase Agreements	(8) Securities Sold Under Repurchase Agreements
	The Company's bank subsidiaries have entered into repurchase agreements with an investment banking firm and individual customers of the bank subsidiaries. The purchasers have agreed to resell to the bank subsidiaries identical securities upon the maturities of the agreements. Securities sold under repurchase agreements were mortgage-backed book entry securities and averaged $893,830,000 and $1,041,186,000 during 2014 and 2013, respectively, and the maximum amount outstanding at any month end during 2014 and 2013 was $892,341,000 and $1,119,531,000, respectively.
	Further information related to repurchase agreements at December 31, 2014 and 2013 is set forth in the following table:
		Collateral Securities				Repurchase Borrowing
		Book Value of		Fair Value of		Balance of		Weighted Average
		Securities Sold		Securities Sold		Liability		Interest Rate
		(Dollars in Thousands)
	December 31, 2014 term:
	Overnight agreements	$	366,731	$	370,704	$	236,077		0.16	%
	1 to 29 days		3,717		3,781		1,016		0.45
	30 to 90 days		13,399		13,628		6,705		0.38
	Over 90 days		743,323		746,305		614,552		3.83
	Total	$	1,127,170	$	1,134,418	$	858,350		2.79	%
	December 31, 2013 term:
	Overnight agreements	$	332,042	$	341,238	$	209,899		0.17	%
	1 to 29 days		27,954		28,288		18,666		0.4
	30 to 90 days		8,106		8,263		3,295		0.43
	Over 90 days		945,535		940,209		725,521		3.78
	Total	$	1,313,637	$	1,317,998	$	957,381		2.91	%
	The book value and fair value of securities sold includes the entire book value and fair value of securities partially or fully pledged under repurchase agreements.

Other_Borrowed_Funds

Other Borrowed Funds	12 Months Ended
	Dec. 31, 2014
Other Borrowed Funds
Other Borrowed Funds	(9) Other Borrowed Funds
	Other borrowed funds include Federal Home Loan Bank borrowings, which are short and long-term fixed borrowings issued by the Federal Home Loan Bank of Dallas at the market price offered at the time of funding. These borrowings are secured by mortgage-backed investment securities and a portion of the Company's loan portfolio.
	Further information regarding the Company's other borrowed funds at December 31, 2014 and 2013 is set forth in the following table:
			December 31,
			2014			2013
			(Dollars in Thousands)
	Federal Home Loan Bank advances—short-term
	Balance at year end		$	1,067,700		$	1,215,000
	Rate on balance outstanding at year end			0.15	%		0.17	%
	Average daily balance		$	1,077,973		$	833,868
	Average rate			0.16	%		0.16	%
	Maximum amount outstanding at any month end		$	1,352,500		$	1,280,500
	Federal Home Loan Bank advances—long-term(1)
	Balance at year end		$	6,244		$	8,950
	Rate on balance outstanding at year end			3.51	%		3.53	%
	Average daily balance		$	7,338		$	7,289
	Average rate			3.51	%		3.53	%
	Maximum amount outstanding at any month end		$	8,934		$	8,993
	-1	The amortization of the long-term advances is approximately $160,000 per year for each of the next five years and the final maturity date is January 3, 2028.

Junior_Subordinated_Deferrable

Junior Subordinated Deferrable Interest Debentures

12 Months Ended

Dec. 31, 2014

Junior Subordinated Deferrable Interest Debentures

Junior Subordinated Deferrable Interest Debentures

(10) Junior Subordinated Deferrable Interest Debentures

The Company has formed seven statutory business trusts under the laws of the State of Delaware, for the purpose of issuing trust preferred securities. The seven statutory business trusts formed by the Company (the "Trusts") have each issued Capital and Common Securities and invested the proceeds thereof in an equivalent amount of junior subordinated debentures (the "Debentures") issued by the Company. As of December 31, 2014 and December 31, 2013, the principal amount of debentures outstanding totaled $175,416,000 and $190,726,000, respectively. On February 11, 2014, the Company bought back all of the Capital and Common Securities of IB Capital Trust VII from the holder of the securities for a price that reflected an approximate six percent discount from the redemption price of the securities and thereby retired the $10,310,000 of related Junior Subordinated Deferrable Interest Debentures related to IB Capital Trust VII. On December 24, 2014, the Company bought back a portion of the Capital Securities of IB Capital Trust XI from the holder of the securities for a price that reflected an approximate 23.6% discount from the redemption price of the securities and thereby retired $5,000,000 of the total $32,900,000 of related Junior Subordinated Deferrable Interest Debentures related to IB Capital Trust XI resulting in Junior Subordinated Deferrable Interest Debentures on Trust XI of $27,990,000 as of December 31, 2014.

The Debentures are subordinated and junior in right of payment to all present and future senior indebtedness (as defined in the respective indentures) of the Company, and are pari passu with one another. The interest rate payable on, and the payment terms of the Debentures are the same as the distribution rate and payment terms of the respective issues of Capital and Common Securities issued by the Trusts. The Company has fully and unconditionally guaranteed the obligations of each of the Trusts with respect to the Capital and Common Securities. The Company has the right, unless an Event of Default (as defined in the Indentures) has occurred and is continuing, to defer payment of interest on the Debentures for up to twenty consecutive quarterly periods on Trusts VI, VIII, IX, X, XI and XII. If interest payments on any of the Debentures are deferred, distributions on both the Capital and Common Securities related to that Debenture would also be deferred. The redemption prior to maturity of any of the Debentures may require the prior approval of the Federal Reserve and/or other regulatory bodies.

For financial reporting purposes, the Trusts are treated as investments of the Company and not consolidated in the consolidated financial statements. Although the Capital Securities issued by each of the Trusts are not included as a component of shareholders' equity on the consolidated statement of condition, the Capital Securities are treated as capital for regulatory purposes. Specifically, under applicable regulatory guidelines, the Capital Securities issued by the Trusts qualify as Tier 1 capital up to a maximum of 25% of Tier 1 capital on an aggregate basis. Any amount that exceeds the 25% threshold would qualify as Tier 2 capital. At December 31, 2014 and December 31, 2013, the total $175,416,000 and $190,726,000, respectively, of the Capital Securities outstanding qualified as Tier 1 capital.

The following table illustrates key information about each of the Debentures and their interest rates at December 31, 2014:

Junior

Repricing

Interest

Interest

Maturity Date

Optional

Subordinated

Frequency

Rate

Rate Index(1)

Redemption Date(1)

Deferrable

Interest

Debentures

(in thousands)

Trust VI

$

25,774

Quarterly

3.68

%

LIBOR + 3.45

Nov-32

Feb-08

Trust VIII

25,774

Quarterly

3.28

%

LIBOR + 3.05

Oct-33

Oct-08

Trust IX

41,238

Quarterly

1.86

%

LIBOR + 1.62

Oct-36

Oct-11

Trust X

34,021

Quarterly

1.88

%

LIBOR + 1.65

Feb-37

Feb-12

Trust XI

27,990

Quarterly

1.86

%

LIBOR + 1.62

Jul-37

Jul-12

Trust XII

20,619

Quarterly

1.69

%

LIBOR + 1.45

Sep-37

Sep-12

$

175,416

-1

The Capital Securities may be redeemed in whole or in part on any interest payment date after the Optional Redemption Date.

Earnings_per_Share_EPS

Earnings per Share ("EPS")	12 Months Ended
	Dec. 31, 2014
Earnings per Share ("EPS")
Earnings per Share ("EPS")	(11) Earnings per Share ("EPS")
	Basic EPS is calculated by dividing net income by the weighted average number of common shares outstanding. The computation of diluted EPS assumes the issuance of common shares for all dilutive potential common shares outstanding during the reporting period. The calculation of the basic EPS and the diluted EPS for the years ended December 31, 2014, 2013, and 2012 is set forth in the following table:
		Net Income		Shares		Per Share
		(Numerator)		(Denominator)		Amount
		(Dollars in Thousands,
		Except Per Share Amounts)
	December 31, 2014:
	Basic EPS
	Net income available to common shareholders	$	153,151		66,872,500	$	2.29
	Potential dilutive common shares and warrants				183,956
			—
	Diluted EPS	$	153,151		67,056,456	$	2.28
	December 31, 2013:
	Basic EPS
	Net income available to common shareholders	$	126,351		67,195,180	$	1.88
	Potential dilutive common shares				119,679
			—
	Diluted EPS	$	126,351		67,314,859	$	1.88
	December 31, 2012:
	Basic EPS
	Net income available to common shareholders	$	93,473		67,236,681	$	1.39
	Potential dilutive common shares				77,282
			—
	Diluted EPS	$	93,473		67,313,963	$	1.39

Employees_Profit_Sharing_Plan

Employees' Profit Sharing Plan	12 Months Ended
	Dec. 31, 2014
Employees' Profit Sharing Plan
Employees' Profit Sharing Plan	(12) Employees' Profit Sharing Plan
	The Company has a deferred profit sharing plan for full-time employees with a minimum of one year of continuous employment. The Company's annual contribution to the plan is based on a percentage, as determined by the Board of Directors, of income before income taxes, as defined, for the year. Allocation of the contribution among officers and employees' accounts is based on length of service and amount of salary earned. Profit sharing costs of $3,510,000, $3,500,000 and $3,400,000 were charged to income for the years ended December 31, 2014, 2013, and 2012, respectively.

International_Operations

International Operations	12 Months Ended
	Dec. 31, 2014
International Operations
International Operations	(13) International Operations
	The Company provides international banking services for its customers through its bank subsidiaries. Neither the Company nor its bank subsidiaries have facilities located outside the United States. International operations are distinguished from domestic operations based upon the domicile of the customer.
	Because the resources employed by the Company are common to both international and domestic operations, it is not practical to determine net income generated exclusively from international activities.
	A summary of assets attributable to international operations at December 31, 2014 and 2013 are as follows:
		2014			2013
		(Dollars in Thousands)
	Loans:
	Commercial	$	150,078		$	142,145
	Others		35,143			39,697
			185,221			181,842
	Less allowance for probable loan losses		(1,060	)		(1,133	)
	Net loans	$	184,161		$	180,709
	Accrued interest receivable	$	702		$	617
	At December 31, 2014, the Company had $114,672,000 in outstanding standby and commercial letters of credit to facilitate trade activities.
	Revenues directly attributable to international operations were $6,034,000, $6,085,000 and $7,714,000 for the years ended December 31, 2014, 2013 and 2012, respectively.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Taxes
Income Taxes	(14) Income Taxes
	The Company files a consolidated U.S. Federal and State income tax return. The current and deferred portions of net income tax expense included in the consolidated statements of income are presented below for the years ended December 31:
		2014			2013			2012
		(Dollars in Thousands)
	Current
	U.S.	$	72,561		$	59,583		$	40,375
	State		5,252			(1,530	)		2,234
	Foreign		1			3			33
	Total current taxes		77,814			58,056			42,642
	Deferred
	U.S.		(969	)		(1,692	)		7,928
	State		(58	)		(125	)		(5	)
	Total deferred taxes		(1,027	)		(1,817	)		7,923
	Total income taxes	$	76,787		$	56,239		$	50,565
	Total income tax expense differs from the amount computed by applying the U.S. Federal income tax rate of 35% for 2014, 2013 and 2012 to income before income taxes. The reasons for the differences for the years ended December 31 are as follows:
		2014			2013			2012
		(Dollars in Thousands)
	Computed expected tax expense	$	80,560		$	64,183		$	55,634
	Change in taxes resulting from:
	Tax-exempt interest income		(4,554	)		(4,828	)		(4,381	)
	State tax, net of federal income taxes and tax credit		3,377			(110	)		1,446
	Tax refunds		—			(966	)		—
	Other investment income		(3,615	)		(2,656	)		(2,691	)
	Other		1,019			616			557
	Actual tax expense	$	76,787		$	56,239		$	50,565
	The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and deferred tax liabilities at December 31, 2014 and 2013 are reflected below:
		2014			2013
		(Dollars in Thousands)
	Deferred tax assets:
	Loans receivable, principally due to the allowance for probable loan losses	$	24,849		$	25,365
	Other real estate owned		3,453			3,878
	Impairment charges on available-for-sale securities		5,618			5,327
	Accrued expenses		268			399
	Net unrealized gains on available for sale investment securities		—			24,235
	Other		5,809			4,816
	Total deferred tax assets		39,997			64,020
	Deferred tax liabilities:
	Bank premises and equipment, principally due to differences on depreciation		(18,314	)		(20,729	)
	Net unrealized gains on available for sale investment securities		(6,182	)		—
	Identified intangible assets and goodwill		(18,787	)		(18,051	)
	Other		(12,303	)		(11,476	)
	Total deferred tax liabilities		(55,586	)		(50,256	)
	Net deferred tax asset (liability)	$	(15,589	)	$	13,764
	The net deferred tax (liability) asset of ($15,589,000) at December 31, 2014 and $13,764,000 at December 31, 2013 is included in other assets or liabilities, respectively in the consolidated statements of condition.

Stock_Options

Stock Options	12 Months Ended
	Dec. 31, 2014
Stock Options
Stock Options	(15) Stock Options
	On April 5, 2012, the Board of Directors adopted the 2012 International Bancshares Corporation Stock Option Plan (the "2012 Plan"). There are 800,000 shares available for stock option grants under the 2012 Plan. Under the 2012 Plan, both qualified incentive stock options ("ISOs") and non-qualified stock options ("NQSOs") may be granted. Options granted may be exercisable for a period of up to 10 years from the date of grant, excluding ISOs granted to 10% shareholders, which may be exercisable for a period of up to only five years. As of December 31, 2014, 204,750 shares were available for future grants under the 2012 Plan.
	The fair value of each option award granted under the plan is estimated on the date of grant using a Black-Scholes-Merton option valuation model that uses the assumptions noted in the following table. Expected volatility is based on the historical volatility of the price of the Company's stock. The Company uses historical data to estimate the expected dividend yield and employee termination rates within the valuation model. The expected term of options is derived from historical exercise behavior. The risk-free rate for periods within the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant.
		2014			2013
	Expected Life (Years)		7.63			7.63
	Dividend yield		2.01	%		2.33	%
	Interest rate		2.28	%		2.86	%
	Volatility		47.36	%		47.28	%
	A summary of option activity under the stock option plans for the twelve months ended December 31, 2014 is as follows:
		Number of			Weighted			Weighted		Aggregate
		options			average			average		intrinsic
					exercise			remaining		value ($)
					price			contractual
								term (years)
										(in Thousands)
	Options outstanding at December 31, 2013		515,143		$	15.98
	Plus: Options granted		564,750			21.48
	Less:
	Options exercised		40,385			13.75
	Options expired		15,125			27.02
	Options forfeited		30,494			18.84
	Options outstanding at December 31, 2014		993,889			18.94			6.62	$	7,567
	Options fully vested and exercisable at December 31, 2014		250,487		$	16.76			2.28	$	2,461
	Stock-based compensation expense included in the consolidated statements of income for the years ended December 31, 2014, 2013 and 2012 was approximately $1,058,000, $414,000 and $474,000, respectively. As of December 31, 2014, there was approximately $3,934,000 of total unrecognized stock-based compensation cost related to non-vested options granted under the Company plans that will be recognized over a weighted average period of 2.3 years.
	Other information pertaining to option activity during the twelve month period ending December 31, 2014, 2013 and 2012 is as follows:
		Twelve Months Ended December 31,
		2014			2013			2012
	Weighted average grant date fair value of stock options granted	$	9.07		$	9.05		$	8.71
	Total fair value of stock options vested	$	376,000		$	480,000		$	524,000
	Total intrinsic value of stock options exercised	$	468,000		$	171,000		$	41,000

Long_Term_Restricted_Stock_Uni

Long Term Restricted Stock Units	12 Months Ended
	Dec. 31, 2014
Long Term Restricted Stock Units
Long Term Restricted Stock Units	(16) Long Term Restricted Stock Units
	As a participant in the Troubled Asset Relief Program Capital Purchase Program (the "CPP") until November 28, 2012, the Company was subject to certain compensation restrictions, which included a prohibition on the payment or accrual of any bonuses (including equity-based incentive compensation) to certain officers and employees except for awards of CPP-compliant long-term restricted stock and stock units.
	On December 18, 2009, the Company's board of directors (the "Board") adopted the 2009 International Bancshares Corporation Long-Term Restricted Stock Unit Plan (the "Plan") to give the Company additional flexibility in the compensation of its officers, employees, consultants and advisors in compliance with all applicable laws and restrictions.
	The Plan authorizes the Company to issue Restricted Stock Units ("RSUs") to officers, employees, consultants and advisors of the Company and its subsidiaries. The Plan provides that RSUs shall be issued by a committee of the Board appointed by the Board from time to time consisting of at least two (2) members of the Board, each of whom is both a non-employee director and an outside director. On December 18, 2009, the Board adopted resolutions creating the Long-Term Restricted Stock Unit Plan Committee to administer the Plan. RSUs issued under the Plan are not equity and are payable only in cash. The Plan provides for both the issuance of CPP-compliant long-term RSUs as well as RSUs that are not CPP-compliant.
	Dennis E. Nixon, the Company's President, Chairman of the Board and a director of the Company, was awarded CPP-compliant RSU's granted as of December 19, 2012, December 16, 2011, December 15, 2010 and December 18, 2009 of $425,000, $400,000, $400,000 and $250,000 for his performance in 2012, 2011, 2010 and 2009, respectively. In order to meet the requirements of a CPP-compliant RSU, Mr. Nixon's RSUs do not exceed one-third of his total annual compensation in the respective year. Mr. Nixon's 2009 and 2010 RSU's vested and were paid in December 2012 in the respective cash amounts of $262,842 and $358,782. The 2011 RSU vested and was paid in December 2013 in the cash amount of $591,344. The 2012 RSU vested and was paid in December 2014 in the cash amount of $572,746.

Commitments_Contingent_Liabili

Commitments, Contingent Liabilities and Other Matters	12 Months Ended
	Dec. 31, 2014
Commitments, Contingent Liabilities and Other Matters
Commitments, Contingent Liabilities and Other Matters	(17) Commitments, Contingent Liabilities and Other Matters
	The Company leases portions of its banking premises and equipment under operating leases. Total rental expense for the years ended December 31, 2014, 2013 and 2012 were $7,200,000, $7,300,000 and $8,300,000, respectively. Future minimum lease payments due under non-cancellable operating leases at December 31, 2014 were as follows:
	Fiscal year ending:
		Total
		(in thousands)
	2015	$	3,505
	2016		2,454
	2017		1,168
	2018		631
	2019		157
	Thereafter		122
	Total	$	8,037
	It is expected that certain leases will be renewed, as these leases expire. Aggregate future minimum rentals to be received under non-cancellable sub-leases greater than one year at December 31, 2014 were $85,875,000.
	Cash of approximately $106,841,000 and $96,087,000 at December 31, 2014 and 2013, respectively, was maintained to satisfy regulatory reserve requirements.
	The Company is involved in various legal proceedings that are in various stages of litigation. Some of these actions allege "lender liability" claims on a variety of theories and claim substantial actual and punitive damages. The Company has determined, based on discussions with its counsel that any material loss in such actions, individually or in the aggregate, is remote or the damages sought, even if fully recovered, would not be considered material to the consolidated statements of condition and related statements of income, comprehensive income, shareholders' equity and cash flows of the Company. However, many of these matters are in various stages of proceedings and further developments could cause management to revise its assessment of these matters.

Transactions_with_Related_Part

Transactions with Related Parties	12 Months Ended
	Dec. 31, 2014
Transactions with Related Parties
Transactions with Related Parties	(18) Transactions with Related Parties
	In the ordinary course of business, the subsidiaries of the Company make loans to directors and executive officers of the Corporation, including their affiliates, families and companies in which they are principal owners. In the opinion of management, these loans are made on substantially the same terms, including interest rates and collateral, as those prevailing at the time for comparable transactions with other persons and do not involve more than normal risk of collectability or present other unfavorable features. The aggregate amounts receivable from such related parties amounted to approximately $26,382,000 and $51,554,000 at December 31, 2014 and 2013, respectively.

Financial_Instruments_with_Off

Financial Instruments with Off-Statement of Condition Risk and Concentrations of Credit Risk	12 Months Ended
	Dec. 31, 2014
Financial Instruments with Off-Statement of Condition Risk and Concentrations of Credit Risk
Financial Instruments with Off-Statement of Condition Risk and Concentrations of Credit Risk	(19) Financial Instruments with Off-Statement of Condition Risk and Concentrations of Credit Risk
	In the normal course of business, the bank subsidiaries are party to financial instruments with off-statement of condition risk to meet the financing needs of their customers. These financial instruments include commitments to their customers. These financial instruments involve, to varying degrees, elements of credit risk in excess of the amounts recognized in the consolidated statement of condition. The contract amounts of these instruments reflect the extent of involvement the bank subsidiaries have in particular classes of financial instruments. At December 31, 2014, the following financial amounts of instruments, whose contract amounts represent credit risks, were outstanding:
	Commitments to extend credit	$	1,662,516,000
	Credit card lines		16,687,000
	Standby letters of credit		103,793,000
	Commercial letters of credit		10,879,000
	The Company enters into a standby letter of credit to guarantee performance of a customer to a third party. These guarantees are primarily issued to support public and private borrowing arrangements. The credit risk involved is represented by the contractual amounts of those instruments. Under the standby letters of credit, the Company is required to make payments to the beneficiary of the letters of credit upon request by the beneficiary so long as all performance criteria have been met. At December 31, 2014, the maximum potential amount of future payments is $103,793,000. At December 31, 2014, the fair value of these guarantees is not significant. Unsecured letters of credit totaled $40,875,000 and $42,503,000 at December 31, 2014 and 2013, respectively.
	The Company enters into commercial letters of credit on behalf of its customers which authorize a third party to draw drafts on the Company up to a stipulated amount and with specific terms and conditions. A commercial letter of credit is a conditional commitment on the part of the Company to provide payment on drafts drawn in accordance with the terms of the commercial letter of credit.
	The bank subsidiaries' exposure to credit loss in the event of nonperformance by the other party to the above financial instruments is represented by the contractual amounts of the instruments. The bank subsidiaries use the same credit policies in making commitments and conditional obligations as they do for on-statement of condition instruments. The bank subsidiaries control the credit risk of these transactions through credit approvals, limits and monitoring procedures. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates normally less than one year or other termination clauses and may require the payment of a fee. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The bank subsidiaries evaluate each customer's credit-worthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary by the subsidiary banks upon extension of credit, is based on management's credit evaluation of the customer. Collateral held varies, but may include residential and commercial real estate, bank certificates of deposit, accounts receivable and inventory.
	The bank subsidiaries make commercial, real estate and consumer loans to customers principally located in South, Central and Southeast Texas and the State of Oklahoma. Although the loan portfolio is diversified, a substantial portion of its debtors' ability to honor their contracts is dependent upon the economic conditions in these areas, especially in the real estate and commercial business sectors.

Capital_Requirements

Capital Requirements	12 Months Ended
	Dec. 31, 2014
Capital Requirements
Capital Requirements	(20) Capital Requirements
	On December 23, 3008, as part of the Troubled Asset Relief Program Capital Purchase Program (the "TARP Capital Purchase Program") of the United States Department of the Treasury ("Treasury"), the Company issued to the Treasury, in exchange for aggregate consideration of $216 million, (i) 216,000 shares of the Company's fixed-rate cumulative perpetual preferred stock, Series A, par value $.01 per share (the "Senior Preferred Stock"), having a liquidation preference of $1,000 per share and (ii) a warrant to purchase 1,326,238 shares of the Company's common stock at a price per share of $24.43 and with a term of ten years (the "Warrant"). The Senior Preferred Stock paid a coupon rate of 5% of the first five years and 9% per year thereafter.
	On November 28, 2012, the Company completed the repurchase of all of the 216,000 shares of the Senior Preferred Stock held by Treasury. The Company commenced the $216 million repayment during the third quarter of 2012 and completed the final payment in the fourth quarter of 2012. The Company paid a total of $41,520,139 in preferred stock dividends to the U.S. Treasury from December of 2008 to November 28, 2012. On June 12, 2013, the U.S. Treasury sold the Warrant to a third party. As of the date of this report the Warrant is still outstanding. Adjustments to the $24.43 per share Exercise Price of the Warrant will be made if the Company pays cash dividends in excess of 33 cents per semi-annual period or makes certain other shareholder distributions before the Warrants expires on December 23, 2018.
	Bank regulatory agencies limit the amount of dividends, which the bank subsidiaries can pay the Corporation, through IBC Subsidiary Corporation, without obtaining prior approval from such agencies. At December 31, 2014, the subsidiary banks could pay dividends of up to $702,750,000 to the Corporation without prior regulatory approval and without adversely affecting their "well-capitalized" status under regulatory capital rules in effect at December 31, 2014. In addition to legal requirements, regulatory authorities also consider the adequacy of the bank subsidiaries' total capital in relation to their deposits and other factors. These capital adequacy considerations also limit amounts available for payment of dividends. The Company historically has not allowed any subsidiary bank to pay dividends in such a manner as to impair its capital adequacy.
	The Company and the bank subsidiaries are subject to various regulatory capital requirements administered by the federal banking agencies. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Company's consolidated financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Company must meet specific capital guidelines that involve quantitative measures of the Company's assets, liabilities, and certain off-statement of condition items as calculated under regulatory accounting practices. The Company's capital amounts and classification are also subject to qualitative judgments by the regulators about components, risk weightings, and other factors.
	Current quantitative measures established by regulation to ensure capital adequacy require the Company to maintain minimum amounts and ratios (set forth in the table on the following page) of Total and Tier 1 capital to risk-weighted assets and of Tier 1 capital to average assets. Management believes, as of December 31, 2014, that the Company and each of the bank subsidiaries met all capital adequacy requirements to which they are subject.
	In July 2013, the FDIC and other regulatory bodies issued final rules consisting of minimum requirements that increase both the quantity and quality of capital held by banking organizations. The final rules are a result of the implementation of the BASEL III capital reforms and various Dodd-Frank Act related capital provisions and impact all U.S. banking organizations with more than $500 million in assets. Consistent with the Basel international framework, the new rule includes a new minimum ratio of common equity tier 1 to risk-weighted assets of 4.5 percent and a common equity tier 1 capital conservation buffer of 2.5 percent of risk-weighted assets. The rule also raised the minimum ratio of tier 1 capital to risk-weighted assets from 4 percent to 6 percent and includes a minimum leverage ratio of 4 percent for all banking organizations. Regarding the quality of capital, the new rule emphasizes common equity tier 1 capital and implements strict eligibility criteria for regulatory capital instruments. The new rule also improves the methodology for calculating risk-weighted assets to enhance risk sensitivity. The new rule is subject to a four year phase in period for mandatory compliance and the Company is required to begin to phase in the new rules beginning on January 1, 2015. Management believes that after the phase in of the new capital standards, the Company and its bank subsidiaries will remain classified as "well-capitalized."
	As of December 31, 2014, the most recent notification from the Federal Deposit Insurance Corporation categorized all the bank subsidiaries as well-capitalized under the regulatory framework for prompt corrective action. To be categorized as "well-capitalized," the Company and the bank subsidiaries must maintain minimum Total risk-based, Tier 1 risk based, and Tier 1 leverage ratios as set forth in the table. There are no conditions or events since that notification that management believes have changed the categorization of the Company or any of the bank subsidiaries as well-capitalized.
	The Company's and the bank subsidiaries' actual capital amounts and ratios for 2014 under current guidelines are presented in the following table:
		Actual					For Capital Adequacy					To Be Well-Capitalized
							Purposes					Under Prompt Corrective
												Action Provisions
		Amount		Ratio			Amount		Ratio			Amount		Ratio
							(greater than		(greater than			(greater than		(greater than
							or equal to)		or equal to)			or equal to)		or equal to)
		(Dollars in Thousands)
	As of December 31, 2014:
	Total Capital (to Risk Weighted Assets):
	Consolidated	$	1,524,998		20.24	%	$	602,847		8.00	%		N/A		N/A
	International Bank of Commerce, Laredo		1,131,528		17.31			523,006		8.00		$	653,757		10.00	%
	International Bank of Commerce, Brownsville		151,489		28.60			42,381		8.00			52,976		10.00
	International Bank of Commerce, Zapata		60,946		33.83			14,412		8.00			18,041		10.00
	Commerce Bank		68,291		37.42			14,600		8.00			18,251		10.00
	Tier 1 Capital (to Risk Weighted Assets):
	Consolidated	$	1,457,068		19.34	%	$	301,424		4.00	%		N/A		N/A
	International Bank of Commerce, Laredo		1,071,360		16.39			261,503		4.00		$	392,254		6.00	%
	International Bank of Commerce, Brownsville		145,584		27.48			21,190		4.00			31,785		6.00
	International Bank of Commerce, Zapata		60,035		33.33			7,206		4.00			10,809		6.00
	Commerce Bank		67,347		36.90			7,300		4.00			10,950		6.00
	Tier 1 Capital (to Average Assets):
	Consolidated	$	1,457,068		12.33	%	$	472,864		4.00	%	$	N/A		N/A
	International Bank of Commerce, Laredo		1,071,360		11.22			381,804		4.00			477,255		5.00	%
	International Bank of Commerce, Brownsville		145,584		13.96			41,717		4.00			52,146		5.00
	International Bank of Commerce, Zapata		60,035		10.88			22,081		4.00			27,602		5.00
	Commerce Bank		67,347		12.04			22,373		4.00			27,966		5.00
	The Company's and the bank subsidiaries' actual capital amounts and ratios for 2013 are also presented in the following table:
		Actual					For Capital Adequacy					To Be Well-Capitalized
							Purposes					Under Prompt Corrective
												Action Provisions
		Amount		Ratio			Amount		Ratio			Amount		Ratio
							(greater than		(greater than			(greater than		(greater than
							or equal to)		or equal to)			or equal to)		or equal to)
		(Dollars in Thousands)
	As of December 31, 2013:
	Total Capital (to Risk Weighted Assets):
	Consolidated	$	1,442,837		20.36	%	$	566,870		8.00	%		N/A		N/A
	International Bank of Commerce, Laredo		1,035,189		16.96			488,303		8.00		$	610,378		10.00	%
	International Bank of Commerce, Brownsville		143,879		27.63			41,652		8.00			52,065		10.00
	International Bank of Commerce, Zapata		57,675		32.65			14,130		8.00			17,663		10.00
	Commerce Bank		64,585		36.45			14,175		8.00			17,719		10.00
	Tier 1 Capital (to Risk Weighted Assets):
	Consolidated	$	1,369,657		19.33	%	$	283,435		4.00	%		N/A		N/A
	International Bank of Commerce, Laredo		969,731		15.89			244,151		4.00		$	366,227		6.00	%
	International Bank of Commerce, Brownsville		138,467		26.60			20,826		4.00			31,239		6.00
	International Bank of Commerce, Zapata		56,459		31.96			7,065		4.00			10,598		6.00
	Commerce Bank		63,491		35.83			7,087		4.00			10,631		6.00
	Tier 1 Capital (to Average Assets):
	Consolidated	$	1,369,657		11.61	%	$	472,044		4.00	%	$	N/A		N/A
	International Bank of Commerce, Laredo		969,731		10.09			384,497		4.00			480,622		5.00	%
	International Bank of Commerce, Brownsville		138,467		13.33			41,553		4.00			51,942		5.00
	International Bank of Commerce, Zapata		56,459		10.64			21,219		4.00			26,523		5.00
	Commerce Bank		63,491		11.88			21,372		4.00			26,715		5.00

Fair_Value

Fair Value

12 Months Ended

Dec. 31, 2014

Fair Value

Fair Value

(21) Fair Value

ASC Topic 820,"Fair Value Measurements and Disclosures" ("ASC 820") defines fair value, establishes a framework for measuring fair value in generally accepted accounting principles, and expands disclosures about fair value measurements. ASC 820 applies to all financial instruments that are being measured and reported on a fair value basis. ASC 820 defines fair value 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; it also establishes a fair value hierarchy that prioritizes the inputs used in valuation methodologies into the following three levels:

•

Level 1 Inputs—Unadjusted quoted prices in active markets for identical assets or liabilities.

•

Level 2 Inputs—Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

•

Level 3 Inputs—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial instruments whose value is determined using pricing models, discounted cash flow methodologies, or other valuation techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation.

A description of the valuation methodologies used for instruments measured at fair value, as well as the general classification of such instruments pursuant to the valuation hierarchy is set forth below.

The following table represents financial instruments reported on the consolidated statements of condition at their fair value as of December 31, 2014 by level within the fair value measurement hierarchy.

Fair Value Measurements at

Reporting Date Using

(in thousands)

Assets/Liabilities

Quoted

Significant

Significant

Measured at

Prices in

Other

Unobservable

Fair Value

Active

Observable

Inputs

December 31,

Markets for

Inputs

(Level 3)

2014

Identical

(Level 2)

Assets

(Level 1)

Measured on a recurring basis:

Assets:

Available for sale securities

Residential mortgage-backed securities

$

4,600,372

$

—

$

4,576,309

$

24,063

States and political subdivisions

282,276

—

282,276

—

Other

49,315

29,315

20,000

—

$

4,931,963

$

29,315

$

4,878,585

$

24,063

The following table represents financial instruments reported on the consolidated balance sheets at their fair value as of December 31, 2013 by level within the fair value measurement hierarchy.

Fair Value Measurements at

Reporting Date Using

(in thousands)

Assets/Liabilities

Quoted

Significant

Significant

Measured at

Prices in

Other

Unobservable

Fair Value

Active

Observable

Inputs

December 31,

Markets for

Inputs

(Level 3)

2013

Identical

(Level 2)

Assets

(Level 1)

Measured on a recurring basis:

Assets:

Available for sale securities

Residential mortgage-backed securities

$

5,027,701

$

—

$

4,999,849

$

27,852

States and political subdivisions

248,410

—

248,410

—

Other

28,468

28,468

—

—

$

5,304,579

$

28,468

$

5,248,259

$

27,852

Investment securities available-for-sale are classified within level 2 and level 3 of the valuation hierarchy, with the exception of certain equity investments that are classified within level 1. For investments classified as level 2 in the fair value hierarchy, the Company obtains fair value measurements for investment securities from an independent pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond's terms and conditions, among other things. Investment securities classified as level 3 are non-agency mortgage-backed securities. The non-agency mortgage-backed securities held by the Company are traded in inactive markets and markets that have experienced significant decreases in volume and level of activity, as evidenced by few recent transactions, a significant decline or absence of new issuances, price quotations that are not based on comparable securities transactions and wide bid-ask spreads among other factors. As a result of the inability to use quoted market prices to determine fair value for these securities, the Company determined that fair value, as determined by level 3 inputs in the fair value hierarchy, is more appropriate for financial reporting and more consistent with the expected performance of the investments. For the investments classified within level 3 of the fair value hierarchy, the Company used a discounted cash flow model to determine fair value. Inputs in the model included both historical performance and expected future performance based on information currently available.

Assumptions used in the discounted cash flow model as of December 31, 2014 and December 31, 2013 were applied separately to those portions of the bond where the underlying residential mortgage loans had been performing under original contract terms for at least the prior 24 months and those where the underlying residential mortgages had not been meeting the original contractual obligation for the same period. Unobservable inputs included in the model are estimates on future principal prepayment rates, and default and loss severity rates. For that portion of the bond where the underlying residential mortgage had been meeting the original contract terms for at least 24 months, the Company used the following estimates in the model: (i) a voluntary prepayment rate of 7%, (ii) a 1% default rate, (iii) a loss severity rate of 25%, and (iv) a discount rate of 13%. The assumptions used in the model for the rest of the bond included the following estimates: (i) a voluntary prepayment rate of 2%, (ii) a default rate of 4.5%, (iii) a loss severity rate that started at 60% for the first year (2012) then declines by 5% for the following five years (2013, 2014, 2015, 2016 and 2017) and remains at 25% thereafter (2018 and beyond), and (iv) a discount rate of 13%. The estimates used in the model to determine fair value are based on observable historical data of the underlying collateral. The model anticipates that the housing market will gradually improve and that the underlying collateral will eventually all perform in accordance with the original contract terms on the bond. Should the number of loans in the underlying collateral that default and go into foreclosure or the severity of the losses in the underlying collateral significantly change, the results of the model would be impacted. The Company will continue to evaluate the actual historical performance of the underlying collateral and will modify the assumptions used in the model as necessary.

The following table presents a reconciliation of activity for such mortgage-backed securities on a net basis (Dollars in thousands):

Balance at December 31, 2013

$

27,852

Principal paydowns

(4,154

)

Total unrealized gains (losses) included in:

Other comprehensive income

1,182

Impairment realized in earnings

(817

)

Balance at December 31, 2014

$

24,063

Certain financial instruments are measured at fair value on a nonrecurring basis. They are not measured at fair value on an ongoing basis but are subject to fair value adjustments in certain circumstances (for example, when there is evidence of impairment).

The following table represents financial instruments measured at fair value on a non-recurring basis as of and for the period ended December 31, 2014 by level within the fair value measurement hierarchy:

Fair Value Measurements at Reporting

Date Using

(in thousands)

Assets/Liabilities

Quoted

Significant

Significant

Net

Measured at

Prices in

Other

Unobservable

(Credit)

Fair Value

Active

Observable

Inputs

Provision

Year ended

Markets for

Inputs

(Level 3)

During

December 31,

Identical

(Level 2)

Period

2014

Assets

(Level 1)

Measured on a non-recurring basis:

Assets:

Impaired loans

$

29,501

$

—

$

—

$

29,501

$

(1,557

)

Other real estate owned

6,112

—

—

6,112

597

The following table represents financial instruments measured at fair value on a non-recurring basis as of and for the year ended December 31, 2013 by level within the fair value measurement hierarchy:

Fair Value Measurements at Reporting

Date Using

(in thousands)

Assets/Liabilities

Quoted

Significant

Significant

Net

Measured at

Prices in

Other

Unobservable

Provision

Fair Value

Active

Observable

Inputs

During

Year ended

Markets

Inputs

(Level 3)

Period

December 31,

for Identical

(Level 2)

2013

Assets

(Level 1)

Measured on a non-recurring basis:

Assets:

Impaired loans

$

28,391

$

—

$

—

$

28,391

$

13,229

Other real estate owned

16,329

—

—

16,329

1,204

The Company's assets measured at fair value on a non-recurring basis are limited to impaired loans and other real estate owned. Impaired loans are classified within level 3 of the valuation hierarchy. The fair value of impaired loans is derived in accordance with FASB ASC 310, "Receivables". Impaired loans are primarily comprised of collateral-dependent commercial loans. Understanding that as the primary sources of loan repayments decline, the secondary repayment source comes into play and correctly evaluating the fair value of that secondary source, the collateral, becomes even more important. Re-measurement of the impaired loan to fair value is done through a specific valuation allowance included in the allowance for probable loan losses. The fair value of impaired loans is based on the fair value of the collateral, as determined through either an appraisal or evaluation process. The basis for the Company's appraisal and appraisal review process is based on regulatory guidelines and strives to comply with all regulatory appraisal laws, regulations and the Uniform Standards of Professional Appraisal Practice. All appraisals and evaluations are "as is" (the property's highest and best use) valuations based on the current conditions of the property/project at that point in time. The determination of the fair value of the collateral is based on the net realizable value, which is the appraised value less any closing costs, when applicable. As of December 31, 2014, the Company had $65,551,000 of impaired commercial collateral dependent loans, of which $52,092,000 had an appraisal performed within the immediately preceding twelve months and of which $5,307,000 had an evaluation performed within the immediately preceding twelve months. As of December 31, 2013, the Company had $64,585,000 of impaired commercial collateral dependent loans, of which $50,346,000 had an appraisal performed within the immediately preceding twelve months and of which $0 had an evaluation performed within the immediately preceding twelve months.

The determination to either seek an appraisal or to perform an evaluation begins in weekly credit quality meetings, where the committee analyzes the existing collateral values of the impaired loans and where obsolete appraisals are identified. In order to determine whether the Company would obtain a new appraisal or perform an internal evaluation to determine the fair value of the collateral, the credit committee reviews the existing appraisal to determine if the collateral value is reasonable in view of the current use of the collateral and the economic environment related to the collateral. If the analysis of the existing appraisal does not find that the collateral value is reasonable under the current circumstances, the Company would obtain a new appraisal on the collateral or perform an internal evaluation of the collateral. The ultimate decision to get a new appraisal rests with the independent credit administration group. A new appraisal is not required if an internal evaluation, as performed by in-house experts, is able to appropriately update the original appraisal assumptions to reflect current market conditions and provide an estimate of the collateral's market value for impairment analysis. The internal evaluations must be in writing and contain sufficient information detailing the analysis, assumptions and conclusions and they must support performing an evaluation in lieu of ordering a new appraisal.

Other real estate owned is comprised of real estate acquired by foreclosure and deeds in lieu of foreclosure. Other real estate owned is carried at the lower of the recorded investment in the property or its fair value less estimated costs to sell such property (as determined by independent appraisal) within level 3 of the fair value hierarchy. Prior to foreclosure, the value of the underlying loan is written down to the fair value of the real estate to be acquired by a charge to the allowance for probable loan losses, if necessary. The fair value is reviewed periodically and subsequent write downs are made accordingly through a charge to operations. Other real estate owned is included in other assets on the consolidated financial statements. For the twelve months ended December 31, 2014 and December 31, 2013, respectively the Company recorded $367,000 and $402,000 in charges to the allowance for probable loan losses in connection with loans transferred to other real estate owned. For the twelve months ended December 31, 2014 and December 31, 2013, respectively, the Company recorded $597,000 and $1,204,000 in adjustments to fair value in connection with other real estate owned.

The fair value estimates, methods, and assumptions for the Company's financial instruments at December 31, 2014 and December 31, 2013 are outlined below.

Cash and Cash Equivalents

For these short-term instruments, the carrying amount is a reasonable estimate of fair value.

Investment securities held-to-maturity

The carrying amounts of investments held-to-maturity approximate fair value.

Investment Securities

For investment securities, which include U. S. Treasury securities, obligations of other U. S. government agencies, obligations of states and political subdivisions and mortgage pass through and related securities, fair values are from an independent pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond's terms and conditions, among other things. See disclosures of fair value of investment securities in Note 2.

Loans

Fair values are estimated for portfolios of loans with similar financial characteristics. Loans are segregated by type such as commercial, real estate and consumer loans as outlined by regulatory reporting guidelines. Each category is segmented into fixed and variable interest rate terms and by performing and non-performing categories.

For variable rate performing loans, the carrying amount approximates the fair value. For fixed rate performing loans, except residential mortgage loans, the fair value is calculated by discounting scheduled cash flows through the estimated maturity using estimated market discount rates that reflect the credit and interest rate risk inherent in the loan. For performing residential mortgage loans, fair value is estimated by discounting contractual cash flows adjusted for prepayment estimates using discount rates based on secondary market sources or the primary origination market. Fixed rate performing loans are within Level 3 of the fair value hierarchy. At December 31, 2014, and December 31, 2013, the carrying amount of fixed rate performing loans was $1,352,147,000 and $1,243,252,000 respectively, and the estimated fair value was $1,285,648,000 and $1,196,916,000, respectively.

Accrued Interest

The carrying amounts of accrued interest approximate fair value.

Deposits

The fair value of deposits with no stated maturity, such as non-interest bearing demand deposit accounts, savings accounts and interest bearing demand deposit accounts, was equal to the amount payable on demand as of December 31, 2014 and December 31, 2013. The fair value of time deposits is based on the discounted value of contractual cash flows. The discount rate is based on currently offered rates. Time deposits are within Level 3 of the fair value hierarchy. At December 31, 2014 and December 31, 2013, the carrying amount of time deposits was $2,482,692,000 and $2,651,303,000, respectively, and the estimated fair value was $2,480,390,000 and $2,649,452,000, respectively.

Securities Sold Under Repurchase Agreements

Securities sold under repurchase agreements include both short and long-term maturities. Due to the contractual terms of the short-term instruments, the carrying amounts approximated fair value at December 31, 2014 and December 31, 2013. The fair value of the long-term instruments is based on established market spreads using option adjusted spread methodology. Long-term repurchase agreements are within level 3 of the fair value hierarchy. At December 31, 2014 and December 31, 2013, respectively, the carrying amount of long-term repurchase agreements was $610,000,000 and $710,000,000 and the estimated fair value was $558,097,100 and $792,215,500, respectively.

Junior Subordinated Deferrable Interest Debentures

The Company currently has floating rate junior subordinated deferrable interest debentures outstanding. Due to the contractual terms of the floating rate junior subordinated deferrable interest debentures, the carrying amounts approximated fair value at December 31, 2014 and December 31, 2013.

Other Borrowed Funds

The Company currently has short and long-term borrowings issued from the Federal Home Loan Bank ("FHLB"). Due to the contractual terms of the short-term borrowings, the carrying amounts approximated fair value at December 31, 2014 and December 31, 2013. The fair value of the long-term borrowings is based on established market spreads for similar types of borrowings. The long-term borrowings are included in Level 2 of the fair value hierarchy. At December 31, 2014 and December 31, 2013, the carrying amount of the long-term FHLB borrowings was $6,244,000 and $8,950,000 respectively, and the estimated fair value was $6,645,000 and $8,950,000, respectively.

Commitments to Extend Credit and Letters of Credit

Commitments to extend credit and fund letters of credit are principally at current interest rates and therefore the carrying amount approximates fair value.

Limitations

Fair value estimates are made at a point in time, based on relevant market information and information about the financial instrument. These estimates do not reflect any premium or discount that could result from offering for sale at one time the Company's entire holdings of a particular financial instrument. Because no market exists for a significant portion of the Company's financial instruments, fair value estimates are based on judgments regarding future expected loss experience, current economic conditions, risk characteristics of various financial instruments and other factors. These estimates are subjective in nature and involve uncertainties and matters of significant judgment and therefore cannot be determined with precision. Changes in assumptions could significantly affect the estimates.

Fair value estimates are based on existing on-and off-statement of condition financial instruments without attempting to estimate the value of anticipated future business and the value of assets and liabilities that are not considered financial instruments. Other significant assets and liabilities that are not considered financial assets or liabilities include the bank premises and equipment and core deposit value. In addition, the tax ramifications related to the effect of fair value estimates have not been considered in the above estimates.

International_Bancshares_Corpo

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Condition	12 Months Ended
	Dec. 31, 2014
International Bancshares Corporation (Parent Company Only) Financial Information Statements of Condition
International Bancshares Corporation (Parent Company Only) Financial Information Statements of Condition	(22) International Bancshares Corporation (Parent Company Only) Financial Information
	Statements of Condition
	(Parent Company Only)
	December 31, 2014 and 2013
	(Dollars in Thousands)
		2014			2013
	ASSETS
	Cash		9,252			8,106
		$			$
	Other investments		69,042			62,381
	Notes receivable		204			313
	Investment in subsidiaries		1,691,553			1,556,932
	Other assets		50			197
	Total assets	$	1,770,101		$	1,627,929
	LIABILITIES AND SHAREHOLDERS' EQUITY
	Liabilities:
	Junior subordinated deferrable interest debentures	$	175,416		$	190,726
	Due to IBC Trading		21			21
	Other liabilities		14,006			12,774
	Total liabilities		189,443			203,521
	Shareholders' equity:
	Common shares		95,784			95,744
	Surplus		165,520			163,947
	Retained earnings		1,585,389			1,467,000
	Accumulated other comprehensive income (loss)		11,397			(43,774	)
			1,858,090			1,682,917
	Less cost of shares in treasury		(277,432			(258,509
				)			)
	Total shareholders' equity		1,580,658			1,424,408
	Total liabilities and shareholders' equity	$	1,770,101		$	1,627,929

International_Bancshares_Corpo1

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Income	12 Months Ended
	Dec. 31, 2014
International Bancshares Corporation (Parent Company Only) Financial Information Statements of Income
International Bancshares Corporation (Parent Company Only) Financial Information Statements of Income	(23) International Bancshares Corporation (Parent Company Only) Financial Information
	Statements of Income
	(Parent Company Only)
	Years ended December 31, 2014, 2013 and 2012
	(Dollars in Thousands)
		2014		2013		2012
	Income:
	Dividends from subsidiaries	$	71,389	$	30,000	$	229,250
	Interest income on notes receivable		15		18		27
	Interest income on other investments		6,862		12,301		6,759
	Other interest income		—		—		18
	Other		1,923		26		686
	Total income		80,189		42,345		236,740
	Expenses:
	Interest expense (Debentures)		4,264		4,665		6,595
	Other		1,099		1,889		3,867
	Total expenses		5,363		6,554		10,462
	Income before federal income taxes and equity in undistributed net income of subsidiaries		74,826		35,791		226,278
	Income tax expense (benefit)		1,370		2,529		(738	)
	Income before equity in undistributed net income of subsidiaries		73,456		33,262		227,016
	Equity in undistributed (distributed) net income of subsidiaries		79,695		93,089		(119,181
								)
	Net income		153,151		126,351		107,835
	Preferred stock dividends and discount accretion		—		—		14,362
	Net income available to common shareholders	$	153,151	$	126,351	$	93,473

International_Bancshares_Corpo2

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Cash Flows	12 Months Ended
	Dec. 31, 2014
International Bancshares Corporation (Parent Company Only) Financial Information Statements of Cash Flows
International Bancshares Corporation (Parent Company Only) Financial Information Statements of Cash Flows	(24) International Bancshares Corporation (Parent Company Only) Financial Information
	Statements of Cash Flows
	(Parent Company Only)
	Years ended December 31, 2014, 2013 and 2012
	(Dollars in Thousands)
		2014			2013			2012
	Operating activities:
	Net income	$	153,151		$	126,351		$	107,835
	Adjustments to reconcile net income to net cash provided by operating activities:
	Impairment charges on available for sale securities		254			754			—
	Stock compensation expense		1,058			414			474
	Increase (decrease) in other liabilities		416			(969	)		6,711
	Equity in (undistributed) distributed net income of subsidiaries		(79,695	)		(93,089	)		119,181
	Net cash provided by operating activities		75,184			33,461			234,201
	Investing activities:
	Principal collected on mortgage-backed securities		1,301			1,207			1,985
	Net decrease in notes receivable		109			96			86
	(Increase) decrease in other assets and other investments		(7,008	)		432			6,418
	Net cash (used in) provided by investing activities		(5,598	)		1,735			8,489
	Financing activities:
	Repayment of trust preferred securities		(15,310	)		—			—
	Redemption of preferred shares		—			—			(216,000	)
	Proceeds from stock transactions		555			265			51
	Payments of cash dividends—common		(34,762	)		(28,894	)		(26,894	)
	Payments of cash dividends—preferred		—			—			(10,260	)
	Purchase of treasury stock		(18,923	)		—			(1,716	)
	Net cash used in financing activities		(68,440	)		(28,629	)		(254,819	)
	Increase (decrease) in cash		1,146			6,567			(12,129	)
	Cash at beginning of year		8,106			1,539			13,668
	Cash at end of year	$	9,252		$	8,106		$	1,539

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies
Consolidation and Basis of Presentation	Consolidation and Basis of Presentation
	The consolidated financial statements include the accounts of the Corporation and its wholly-owned bank subsidiaries, International Bank of Commerce, Laredo ("IBC"), Commerce Bank, International Bank of Commerce, Zapata, International Bank of Commerce, Brownsville, and the Corporation's wholly-owned non-bank subsidiaries, IBC Subsidiary Corporation, IBC Life Insurance Company, IBC Trading Company, Premier Tierra Holdings, Inc., IBC Charitable and Community Development Corporation, and IBC Capital Corporation. All significant inter-company balances and transactions have been eliminated in consolidation.
	The Company, through its subsidiaries, is primarily engaged in the business of banking, including the acceptance of checking and savings deposits and the making of commercial, real estate, personal, home improvement, automobile and other installment and term loans. The primary markets of the Company are South, Central, and Southeast Texas and the state of Oklahoma. Each bank subsidiary is very active in facilitating international trade along the United States border with Mexico and elsewhere. Although the Company's loan portfolio is diversified, the ability of the Company's debtors to honor their contracts is primarily dependent upon the economic conditions in the Company's trade area. In addition, the investment portfolio is directly impacted by fluctuations in market interest rates. The Company and its bank subsidiaries are subject to the regulations of certain Federal agencies as well as the Texas Department of Banking and undergo periodic examinations by those regulatory authorities. Such agencies may require certain standards or impose certain limitations based on their judgments or changes in law and regulations.
	The Company owns two insurance-related subsidiaries, IBC Life Insurance Company and IBC Insurance Agency, Inc., a wholly owned subsidiary of IBC, the bank subsidiary. Neither of the insurance-related subsidiaries conducts underwriting activities. The IBC Life Insurance Company is in the business of reinsuring credit life and credit accident and health insurance. The business is assumed from an unaffiliated insurer and the only business written is generated by the bank subsidiaries of the Company. The risk assumed on each of the policies is not significant to the consolidated financial statements.
	The preparation of the consolidated financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the dates of the statement of condition and income and expenses for the periods. Actual results could differ significantly from those estimates. Material estimates that are particularly susceptible to significant changes in the near-term relate to the determination of the allowance for probable loan losses.
Subsequent Events	Subsequent Events
	The Company has evaluated all events or transactions that occurred through the date the Company issued these financial statements. During this period, the Company did not have any material recognizable or non-recognizable subsequent events.
Investment Securities	Investment Securities
	The Company classifies debt and equity securities into one of these categories: held-to-maturity, available-for-sale, or trading. Such classifications are reassessed for appropriate classification at each reporting date. Securities that are intended and expected to be held until maturity are classified as "held-to-maturity" and are carried at amortized cost for financial statement reporting. Securities that are not positively expected to be held until maturity, but are intended to be held for an indefinite period of time are classified as "available-for-sale" or "trading" and are carried at their fair value. Unrealized holding gains and losses are included in net income for those securities classified as "trading", while unrealized holding gains and losses related to those securities classified as "available-for-sale" are excluded from net income and reported net of tax as other comprehensive income and in shareholders' equity as accumulated other comprehensive income until realized. The Company did not maintain any trading securities during the three year period ended December 31, 2014.
	Mortgage-backed securities held at December 31, 2014 and 2013 represent participating interests in pools of long-term first mortgage loans originated and serviced by the issuers of the securities. Mortgage-backed securities are either issued or guaranteed by the U.S. Government or its agencies including the Federal Home Loan Mortgage Corporation ("Freddie Mac"), the Federal National Mortgage Association ("Fannie Mae"), the Government National Mortgage Association ("Ginnie Mae") or other non-government entities. Investments in residential mortgage-backed securities issued by Ginnie Mae are fully guaranteed by the U. S. Government. Investments in residential mortgage-backed securities issued by Freddie Mac and Fannie Mae are not fully guaranteed by the U.S. Government, however, the Company believes that the quality of the bonds is similar to other AAA rated bonds with limited credit risk, particularly given the placement of Fannie Mae and Freddie Mac into conservatorship by the federal government in 2008 and because securities issued by others that are collateralized by residential mortgage-backed securities issued by Fannie Mae or Freddie Mac are rated consistently as AAA rated securities. Market interest rate fluctuations can affect the prepayment speed of principal and the yield on the security.
	Premiums and discounts are amortized using the level yield or "interest method" over the terms of the securities. Declines in the fair value of held-to-maturity and available-for sale-securities below their cost that are deemed to be other than temporary are reflected in earnings as realized losses. In determining whether other-than-temporary impairment exists, management considers many factors, including (1) the length of time and the extent to which the fair value has been less than cost, (2) the financial condition and near-term prospects of the issuer, and (3) the intent of the Company to hold and the determination of whether the Company will more likely than not be required to sell the security prior to a recovery in fair value. If the Company determines that (1) it intends to sell the security or (2) it is more likely than not that it will be required to sell the security before it's anticipated recovery, the other-than-temporary impairment that is recognized in earnings is equal to the difference between the fair value of the security and the Company's amortized cost in the security. If the Company determines that it (1) does not intend to sell the security and (2) it will not be more likely than not required to sell the security before it's anticipated recovery, the other-than-temporary impairment is segregated into its two components (1) the amount of impairment related to credit loss and (2) the amount of impairment related to other factors. The difference between the present value of the cash flows expected to be collected and the amortized cost is the credit loss recognized through earnings and an adjustment to the cost basis of the security. The amount of impairment related to other factors is included in other comprehensive income (loss). Gains and losses on the sale of securities are recorded on the trade date and are determined using the specific identification method.
Provision and Allowance for Probable Loan Losses	Provision and Allowance for Probable Loan Losses
	The allowance for probable loan losses is maintained at a level considered adequate by management to provide for probable loan losses. The allowance is increased by provisions charged to operating expense and reduced by net charge-offs. The provision for probable loan losses is the amount, which, in the judgment of management, is necessary to establish the allowance for probable loan losses at a level that is adequate to absorb known and inherent risks in the loan portfolio.
	Management believes that the allowance for probable loan losses is adequate. While management uses available information to recognize losses on loans, future additions to the allowance may be necessary based on changes in economic conditions. In addition, various regulatory agencies, as an integral part of their examination process, periodically review the Company's bank subsidiaries' allowances for probable loan losses. Such agencies may require the Company's bank subsidiaries to make additions or reductions to their U.S. generally accepted accounting principles ("GAAP") allowances based on their judgments of information available to them at the time of their examination.
	The bank subsidiaries charge off that portion of any loan which management considers to represent a loss as well as that portion of any other loan which is classified as a "loss" by bank examiners. Commercial, financial and agricultural or real estate loans are generally considered by management to represent a loss, in whole or part, (i) when an exposure beyond any collateral coverage is apparent, (ii) when no further collection of the portion of the loan so exposed is anticipated based on actual results, (iii) when the credit enhancements, if any, are not adequate, and (iv) when the borrower's financial condition would indicate so. Generally, unsecured consumer loans are charged off when 90 days past due.
Loans	Loans
	Loans are reported at the principal balance outstanding, net of unearned discounts. Interest income on loans is reported on an accrual basis. Loan fees and costs associated with originating the loans are amortized over the life of the loan using the interest method. The Company originates mortgage loans that may subsequently be sold to an unaffiliated third party. The loans are not securitized and if sold, are sold without recourse. Loans held for sale are carried at cost and the principal amount outstanding is not significant to the consolidated financial statements.
Impaired Loans	Impaired Loans
	Impaired loans are those loans where it is probable that all amounts due according to contractual terms of the loan agreement will not be collected. Impaired loans are measured based on (1) the present value of expected future cash flows discounted at the loan's effective interest rate; (2) the loan's observable market price; or (3) the fair value of the collateral if the loan is collateral dependent. Substantially all of the Company's impaired loans are measured at the fair value of the collateral. In limited cases the Company may use other methods to determine the level of impairment of a loan if such loan is not collateral dependent.
Troubled Debt Restructured Loans	Troubled Debt Restructured Loans
	Troubled debt restructured loans ("TDR") are those loans where, for reasons related to a borrower's difficulty to repay a loan, the Company grants a concession to the borrower that the Company would not normally consider in the normal course of business. The original terms of the loan are modified or restructured. The terms that may be modified include a reduction in the original stated interest rate, an extension of the original maturity of the loan, a renewal of the loan at an interest rate below current market rates, a reduction in the principal amount of debt outstanding, a reduction in accrued interest or deferral of interest payments. A loan classified as a TDR is classified as an impaired loan and included in the impaired loan totals. A TDR loan may be returned to accrual status when the loan is brought current, has performed in accordance with the restructured terms for a reasonable period of time and the ultimate collectability of the outstanding principal and interest is no longer questionable, however, although those loans may be placed back on accrual status, they will continue to be classified as impaired. Consistent with regulatory guidance, a TDR loan that is subsequently modified, but has shown sustained performance and classification as a TDR, will be removed from TDR status provided that the modified terms were market-based at the time of modification.
Non-Accrual Loans	Non-Accrual Loans
	The non-accrual loan policy of the Company's bank subsidiaries is to discontinue the accrual of interest on loans when management determines that it is probable that future interest accruals will be un-collectible. As it relates to consumer loans, management charges off those loans when the loan is contractually 90 days past due. Under special circumstances, a consumer or non-consumer loan may be more than 90 days delinquent as to interest or principal and not be placed on non-accrual status. This situation generally results when a bank subsidiary has a borrower who is experiencing financial difficulties, but not to the extent that requires a restructuring of indebtedness. The majority of this category is composed of loans that are considered to be adequately secured and/or for which there are expected future payments. When a loan is placed on non-accrual status, any interest accrued, not paid is reversed and charged to operations against interest income. As it relates to non-consumer loans that are not 90 days past due, management will evaluate each of these loans to determine if placing the loan on non-accrual status is warranted. Interest income on non-accrual loans is recognized only to the extent payments are received or when, in management's opinion, the debtor's financial condition warrants reestablishment of interest accruals.
Other Real Estate Owned	Other Real Estate Owned
	Other real estate owned is comprised of real estate acquired by foreclosure and deeds in lieu of foreclosure. Other real estate is carried at the lower of the recorded investment in the property or its fair value less estimated costs to sell such property (as determined by independent appraisal). Prior to foreclosure, the value of the underlying loan is written down to the fair value of the real estate to be acquired by a charge to the allowance for probable loan losses, if necessary. Any subsequent write-downs are charged against other non-interest expense. Other real estate owned totaled $69,872,000 and $85,879,000 at December 31, 2014 and 2013, respectively. Other real estate owned is included in other assets.
Bank Premises and Equipment	Bank Premises and Equipment
	Bank premises and equipment are stated at cost less accumulated depreciation. Depreciation is computed on straight-line and accelerated methods over the estimated useful lives of the assets. Repairs and maintenance are charged to operations as incurred and expenditures for renewals and betterments are capitalized.
Other Investments	Other Investments
	Other investments include equity investments in non-financial companies, bank owned life insurance, as well as equity securities with no readily determinable fair market value. Equity investments are accounted for using the equity method of accounting. Equity securities with no readily determinable fair value are accounted for using the cost method.
Income Taxes	Income Taxes
	Deferred income tax assets and liabilities are determined using the asset and liability method. Under this method, the net deferred tax asset or liability is determined based on the tax effects of the differences between the book and tax basis of the various balance sheet assets and liabilities and gives current recognition to changes in tax rates and laws. The Company files a consolidated federal income tax return with its subsidiaries.
	Recognition of deferred tax assets is based on management's assessment that the benefit related to certain temporary differences, tax operating loss carry forwards, and tax credits are more likely than not to be realized. A valuation allowance is recorded for the amount of the deferred tax items for which it is more likely than not that the tax benefits will not be realized.
	The Company evaluates uncertain tax positions at the end of each reporting period. The Company may recognize the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefit recognized in the financial statements from any such a position is measured based on the largest benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. As of December 31, 2014 and 2013, respectively, after evaluating all uncertain tax positions, the Company has recorded no liability for unrecognized tax benefits at the end of the reporting period. The Company would recognize any interest accrued on unrecognized tax benefits as other interest expense and penalties as other non-interest expense. During the years ended December 31, 2014, 2013 and 2012, the Company recognized no interest expense or penalties related to uncertain tax positions.
	The Company files consolidated tax returns in the U.S. Federal jurisdiction and various state jurisdictions. The Company is no longer subject to U.S. federal or state income tax examinations by tax authorities for years before 2011.
Stock Options	Stock Options
	Compensation expense for stock awards is based on the market price of the stock on the measurement date, which is generally the date of grant, and is recognized ratably over the service period of the award. The fair value of stock options granted was estimated, using the Black-Sholes-Merton option-pricing model. This model was developed for use in estimating the fair value of publicly traded options that have no vesting restrictions and are fully transferable. Additionally, the model requires the input of highly subjective assumptions. Because the Company's employee stock options have characteristics significantly different from those of publicly traded options, and because changes in the subjective input assumptions can materially affect the fair value estimate, in management's opinion, the Black-Scholes-Merton option-pricing model does not necessarily provide a reliable single measure of the fair value of the Company's stock options.
Net Income Per Share	Net Income Per Share
	Basic Earnings Per Share ("EPS") is calculated by dividing net income by the weighted average number of common shares outstanding. The computation of diluted EPS assumes the issuance of common shares for all dilutive potential common shares outstanding during the reporting period. The dilutive effect of stock options is considered in earnings per share calculations, if dilutive, using the treasury stock method.
Goodwill and Identified Intangible Assets	Goodwill and Identified Intangible Assets
	Goodwill represents the excess of costs over fair value of assets of businesses acquired. Goodwill is tested for impairment at least annually or on an interim basis if an event triggering impairment may have occurred. As of October 1, 2014, after completing goodwill testing, the Company has determined that no goodwill impairment exists.
	Identified intangible assets are acquired assets that lack physical substance but can be distinguished from goodwill because of contractual or other legal rights or because the asset is capable of being sold or exchanged either on its own or in combination with a related contract, asset, or liability. The Company's identified intangible assets relate to core deposits and contract rights. As of December 31, 2014, the Company has determined that no impairment of identified intangibles exists. Identified intangible assets with definite useful lives are amortized on an accelerated basis over their estimated life. See Note 6—Goodwill and Other Intangible Assets.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets
	Long-lived assets, such as property, plant and equipment, and purchased intangibles subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying value of the asset to the estimated undiscounted future cash flows expected to be generated by the asset. If the carrying value of an asset exceeds its estimated future cash flows, an impairment charge is recognized by the amount by which the carrying value of the asset exceeds the fair value of the asset. Assets to be disposed of would be separately presented in the statement of condition and reported at the lower of the carrying value or fair value less costs to sell, and are no longer depreciated. The assets and liabilities of a disposed group classified as held for sale would be presented separately in the appropriate asset and liability sections of the statement of condition.
Consolidated Statements of Cash Flows	Consolidated Statements of Cash Flows
	For purposes of the consolidated statements of cash flows, the Company considers all short-term investments with a maturity at date of purchase of three months or less to be cash equivalents. Also, the Company reports transactions related to deposits and loans to customers on a net basis.
Accounting for Transfers and Servicing of Financial Assets	Accounting for Transfers and Servicing of Financial Assets
	The Company accounts for transfers and servicing of financial assets and extinguishments of liabilities based on the application of a financial-components approach that focuses on control. After a transfer of financial assets, the Company recognizes the financial and servicing assets it controls and liabilities it has incurred, derecognizes financial assets when control has been surrendered and derecognizes liabilities when extinguished. The Company has retained mortgage servicing rights in connection with the sale of mortgage loans. Because the Company may not initially identify loans as originated for resale, all loans are initially treated as held for investment. The value of the mortgage servicing rights are reviewed periodically for impairment and are amortized in proportion to, and over the period of estimated net servicing income or net servicing losses. The value of the mortgage servicing rights is not significant to the consolidated statements of condition.
Segments of an Enterprise and Related Information	Segments of an Enterprise and Related Information
	The Company operates as one segment. The operating information used by the Company's chief executive officer for purposes of assessing performance and making operating decisions about the Company is the consolidated financial statements presented in this report. The Company has four active operating subsidiaries, namely, the bank subsidiaries, otherwise known as International Bank of Commerce, Laredo, Commerce Bank, International Bank of Commerce, Zapata and International Bank of Commerce, Brownsville. The Company applies the provisions of ASC Topic 280, "Segment Reporting," in determining its reportable segments and related disclosures.
Comprehensive Income (Loss)	Comprehensive Income (Loss)
	Comprehensive income (loss) consists of net income and other comprehensive income (loss). Other comprehensive income (loss) includes unrealized gains and losses on securities available for sale.
Advertising	Advertising
	Advertising costs are expensed as incurred.
Reclassifications	Reclassifications
	Certain amounts in the prior year's presentations have been reclassified to conform to the current presentation. These reclassifications had no effect on previously reported net income or shareholders' equity.
New Accounting Standards	New Accounting Standards
	In February 2013, the Financial Accounting Standards Board issued Accounting Standards Update No. 2013-02 to ASC 220, "Comprehensive Income." The update amends existing literature to require an entity to provide information about the amounts reclassified out of other comprehensive income by component, and it also requires enhanced disclosure and cross reference on items reclassified out of accumulated other comprehensive income during the reporting period. The update is effective for reporting periods beginning after December 15, 2012. The adoption of the update to existing standards did not have a significant impact to the Company's consolidated financial statements.
	In July 2013, the Financial Accounting Standards Board issued Accounting Standards Update No. 2013-11 to ASC 740, "Income Taxes." The update amends existing literature to eliminate diversity in practice in the presentation of unrecognized tax benefits in instances where a net operating loss carryforward, a similar tax loss or a tax credit carryforward also exist. The update clarifies how the unrecognized tax benefit should be presented in those situations where other tax losses or tax credit carryforwards exist. The update does not change the currently required disclosures for unrecognized tax benefits under current ASC 740 guidance. The update is effective for fiscal years and interim periods within those years beginning after December 15, 2013. The adoption of the update to existing standards did not have a significant impact to the Company's consolidated financial statements.
	In January 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-01 to ASC 323-70, "Investments—Equity Method and Joint Ventures—Accounting for Investments in Qualified Affordable Housing Project." The update issues new guidance for investments in qualified affordable housing projects which permits entities to elect to apply the proportional amortization method to account for the investment when certain conditions are met. The update is effective for public entities for annual and interim periods beginning after December 15, 2014 and is able to be applied retrospectively. The adoption of the update is not expected to have a significant impact to the Company's consolidated financial statements.
	In January 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-04 to ASC 310-40, "Receivables—Troubled Debt Restructurings by Creditors." The update amends existing literature to eliminate diversity in practice by clarifying and defining when an in substance repossession or foreclosure occurs. The terms "in substance repossession or foreclosure" and "physical possession" are not currently defined in the accounting literature, resulting in diversity in practice when a creditor derecognizes a loan receivable and recognizes the real estate property collateralizing the loan receivable as an asset. Additionally, the update requires interim and annual disclosures of both the amount of foreclosed residential real estate property and the recorded investment in consumer mortgage loans collateralized by residential real estate property that are in the process of foreclosure. The update is effective for annual periods and the interim periods within those annual periods beginning after December 15, 2014. The adoption of the update to existing standards is not expected to have a significant impact to the Company's consolidated financial statements.
	In April 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-08 to ASC 205, "Presentation of Financial Statements," and ASC 360, "Property, Plant and Equipment." The update to existing standards change the requirements for reporting discontinued operations, primarily by clarifying that the disposal of a component or group of components of an entity could constitute discontinued operations under certain circumstances. The update also defines required information in disclosures about discontinued operations, including a discussion of the entity's continued involvement in the discontinued operation, if any. The update is applicable to all disposals of components of an entity that occurred within interim and annual periods beginning after December 15, 2014 and for acquisitions that are classified as held for sale for interim and annual periods beginning after December 15, 2014. The adoption of the update is not expected to have a significant impact to the Company's consolidated financial statements.
	In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-09 to ASC 606, "Revenue from Contracts with Customers." The update sets a common standard that defines revenue and the principles for recognizing revenue. The update outlines when an entity should recognize revenue, among other matters. At its core, the update states that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The update also outlines the steps that entities should take to determine and record the correct revenue number. The update is effective for annual periods beginning after December 15, 2016 and the interim periods within that reporting period. The Company is evaluating the potential impact to the Company's consolidated financial statements.
	In June 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-11 to ASC 860, "Transfers and Servicing." The update amends existing standards to require that repurchase-to-maturity transactions be accounted for as secured borrowings, in line with accounting standards for other similar instruments. Additionally, the update requires various disclosures including information regarding transfers accounted for as sales in transactions that are economically similar as repurchase agreements, in addition to disclosures related to collateral, remaining contractual tenor and a discussion of the potential risks associated with repurchase agreements, securities lending transactions and repurchase-to-maturity transactions. The update is effective for interim and annual periods beginning after December 15, 2014. The adoption of the update to existing standards is not expected to have a significant impact to the Company's consolidated financial statements.
	In August 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-14 to ASC 310-40, "Receivables—Troubled Debt Restructurings by Creditors." The update is new guidance regarding classification and measurement of foreclosed mortgage loans that are government guaranteed. The update specifies that government secured mortgage loans foreclosed upon should be classified as other assets and measured based on the amount of the loan balance that is expected to be recovered from the guarantor. The new guidance is effective for interim and annual periods after December 15, 2014. The adoption of the update is not expected to have a significant impact to the Company's consolidated financial statements.
	In January 2015, the Financial Accounting Standards Board issued Accounting Standards Update No. 2015-01 to ASC 225-20, "Income Statement- Extraordinary and Unusual Items." The update amends existing standards and is being issued as part of the FASB's initiative to reduce complexity in accounting standards. The update eliminates the concept of extraordinary items. The update is effective for interim and annual periods after December 15, 2015. The adoption of the update to existing standards is not expected to have a significant impact to the Company's consolidated financial statements.
	In February 2015, the Financial Accounting Standards Board issued Accounting Standards Update No. 2015-02 to ASC 810, "Consolidation." The update amends existing standards regarding the evaluation of certain legal entities and their consolidation in the financial statements. The amendments modify the evaluation process to assess whether limited partnerships and similar legal entities are variable interest entities or voting interest entities, eliminate the presumption that a general partner should consolidate a limited partnership, affect the consolidation analysis of entities that are involved in variable interest entities, particularly those that have fee arrangements and related party relationships and provides a scope exception for reporting entities with legal interests that are required to comply with or operate in accordance with requirements that are similar to those in Rule 2a-7 of the Investment Company Act of 1940 for registered money market funds. The update is effective for interim and annual periods after December 15, 2015. The Company is evaluating the impact of the adoption of the update.

Investment_Securities_Tables

Investment Securities (Tables)	12 Months Ended
	Dec. 31, 2014
Investment Securities
Amortized cost and estimated fair value by type of investment security	The amortized cost and estimated fair value by type of investment security at December 31, 2014 are as follows:
			Held to Maturity
			Amortized		Gross			Gross			Estimated			Carrying
			cost		unrealized			unrealized			fair value			value
					gains			losses
			(Dollars in Thousands)
	Other securities		$	2,400	$	—		$	—		$	2,400		$	2,400
	Total investment securities		$	2,400	$	—		$	—		$	2,400		$	2,400
			Available for Sale
			Amortized		Gross			Gross			Estimated			Carrying
			cost		unrealized			unrealized			fair value			value(1)
					gains			losses
			(Dollars in Thousands)
	Residential mortgage-backed securities		$	4,597,590	$	47,960		$	(45,178	)	$	4,600,372		$	4,600,372
	Obligations of states and political subdivisions			268,763		19,131			(5,618	)		282,276			282,276
	Other debt securities			20,000		—			—			20,000			20,000
	Equity securities			28,075		1,425			(185	)		29,315			29,315
	Total investment securities		$	4,914,428	$	68,516		$	(50,981	)	$	4,931,963		$	4,931,963
	-1	Included in the carrying value of residential mortgage-backed securities are $1,503,774 of mortgage-backed securities issued by Ginnie Mae, $3,072,535 of mortgage-backed securities issued by Fannie Mae and Freddie Mac and $24,063 issued by non-government entities
	The amortized cost and estimated fair value by type of investment security at December 31, 2013 are as follows:
			Held to Maturity
			Amortized		Gross			Gross			Estimated			Carrying
			cost		unrealized			unrealized			fair value			value
					gains			losses
			(Dollars in Thousands)
	Other securities		$	2,400	$	—		$	—		$	2,400		$	2,400
	Total investment securities		$	2,400	$	—		$	—		$	2,400		$	2,400
			Available for Sale
			Amortized		Gross			Gross			Estimated			Carrying
			cost		unrealized			unrealized			fair value			value(1)
					gains			losses
			(Dollars in Thousands)
	Residential mortgage-backed securities		$	5,096,165	$	56,110		$	(124,574	)	$	5,027,701		$	5,027,701
	Obligations of states and political subdivisions			248,354		8,063			(8,007	)		248,410			248,410
	Equity securities			28,075		931			(538	)		28,468			28,468
	Total investment securities		$	5,372,594	$	65,104		$	(133,119	)	$	5,304,579		$	5,304,579
	-1	Included in the carrying value of residential mortgage-backed securities are $1,799,807 of mortgage-backed securities issued by Ginnie Mae, $3,200,042 of mortgage-backed securities issued by Fannie Mae and Freddie Mac and $27,852 issued by non-government entities
Amortized cost and fair value of investment securities, by contractual maturity	The amortized cost and estimated fair value of investment securities at December 31, 2014, by contractual maturity, are shown below.
			Held to Maturity					Available for Sale
			Amortized		Estimated			Amortized			Estimated
			Cost		fair value			Cost			fair value
			(Dollars in Thousands)
	Due in one year or less		$	1,075	$	1,075		$	—		$	—
	Due after one year through five years			1,325		1,325			—			—
	Due after five years through ten years			—		—			735			812
	Due after ten years			—		—			288,028			301,464
	Residential mortgage-backed securities			—		—			4,597,590			4,600,372
	Equity securities			—		—			28,075			29,315
	Total investment securities		$	2,400	$	2,400		$	4,914,428		$	4,931,963
Gross unrealized losses on investment securities and the related fair value	Gross unrealized losses on investment securities and the fair value of the related securities, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at December 31, 2014 were as follows:
			Less than 12 months					12 months or more						Total
			Fair Value		Unrealized			Fair Value			Unrealized			Fair Value		Unrealized
					Losses						Losses					Losses
			(Dollars in Thousands)
	Available for sale:
	Residential mortgage-backed securities		$	808,072	$	(4,910	)	$	1,836,218		$	(40,268	)	$	2,644,290	$	(45,178	)
	Obligations of states and political subdivisions			8,833		(97	)		27,793			(5,521	)		36,626		(5,618	)
	Equity securities			74		(1	)		8,066			(184	)		8,140		(185	)
			$	816,979	$	(5,008	)	$	1,872,077		$	(45,973	)	$	2,689,056	$	(50,981	)
	Gross unrealized losses on investment securities and the fair value of the related securities, aggregated by investment category and length of time that individual securities have been in a continuous loss position, at December 31, 2013 were as follows:
			Less than 12 months					12 months or more						Total
			Fair Value		Unrealized			Fair Value			Unrealized			Fair Value		Unrealized
					Losses						Losses					Losses
			(Dollars in Thousands)
	Available for sale:
	Residential mortgage-backed securities		$	2,459,565	$	(98,022	)	$	420,262		$	(26,552	)	$	2,879,827	$	(124,574	)
	Obligations of states and political subdivisions			55,327		(3,025	)		14,292			(4,982	)		69,619		(8,007	)
	Equity securities			19,462		(538	)		—			—			19,462		(538	)
			$	2,534,354	$	(101,585	)	$	434,554		$	(31,534	)	$	2,968,908	$	(133,119	)
Reconciliation of credit-related impairment charges on available-for-sale investment	The following table presents a reconciliation of credit-related impairment charges on available-for-sale investments recognized in earnings for the twelve months ended December 31, 2014 (in Thousands):
	Balance at December 31, 2013		$	11,806
	Impairment charges recognized during period			817
	Balance at December 31, 2014		$	12,623
	The following table presents a reconciliation of credit-related impairment charges on available-for-sale investments recognized in earnings for the twelve months ended December 31, 2013 (in Thousands):
	Balance at December 31, 2012		$	10,432
	Impairment charges recognized during period			1,374
	Balance at December 31, 2013		$	11,806
	The following table presents a reconciliation of credit-related impairment charges on available-for-sale investments recognized in earnings for the twelve months ended December 31, 2012 (in Thousands):
	Balance at December 31, 2011		$	9,393
	Impairment charges recognized during period			1,039
	Balance at December 31, 2012		$	10,432

Loans_Tables

Loans (Tables)	12 Months Ended
	Dec. 31, 2014
Loans
Summary of loans, by loan type
		December 31,		December 31,
		2014		2013
		(Dollars in Thousands)
	Commercial, financial and agricultural	$	3,107,584	$	2,894,779
	Real estate—mortgage		910,326		847,692
	Real estate—construction		1,414,977		1,208,508
	Consumer		61,137		66,414
	Foreign		185,221		181,842
	Total loans	$	5,679,245	$	5,199,235

Allowance_for_Probable_Loan_Lo1

Allowance for Probable Loan Losses (Tables)	12 Months Ended
	Dec. 31, 2014
Allowance for Probable Loan Losses
Summary of the changes in the allowance for probable loan losses, by loan class
		December 31, 2014
		Domestic																					Foreign
		Commercial			Commercial			Commercial			Commercial			Residential:			Residential:			Consumer			Foreign			Total
					real estate:			real estate:			real estate:			first lien			junior lien
					other			farmland &			multifamily
					construction &			commercial
					land
					development
		(Dollars in Thousands)
	Balance at December 31,	$	22,433		$	12,541		$	24,467		$	776		$	3,812		$	4,249		$	750		$	1,133		$	70,161
	Losses charge to allowance		(19,110	)		(680	)		(1,893	)		—			(351	)		(661	)		(719	)		(51	)		(23,465	)
	Recoveries credited to allowance		2,979			72			107			—			49			242			210			50			3,709
	Net losses charged to allowance		(16,131	)		(608	)		(1,786	)		—			(302	)		(419	)		(509	)		(1	)		(19,756	)
	Provision (credit) charged to operations		16,050			1,022			(3,998	)		70			79			853			419			(72	)		14,423
	Balance at December 31,	$	22,352		$	12,955		$	18,683		$	846		$	3,589		$	4,683		$	660		$	1,060		$	64,828
		December 31, 2013
		Domestic																					Foreign
		Commercial			Commercial			Commercial			Commercial			Residential:			Residential:			Consumer			Foreign			Total
					real estate:			real estate:			real estate:			first lien			junior lien
					other			farmland &			multifamily
					construction &			commercial
					land
					development
		(Dollars in Thousands)
	Balance at December 31,	$	11,632		$	12,720		$	21,880		$	694		$	4,390		$	4,448		$	1,289		$	1,140		$	58,193
	Losses charge to allowance		(11,737	)		(278	)		(600	)		(5	)		(632	)		(620	)		(561	)		(22	)		(14,455	)
	Recoveries credited to allowance		2,690			87			152			—			61			298			162			5			3,455
	Net losses charged to allowance		(9,047	)		(191	)		(448	)		(5	)		(571	)		(322	)		(399	)		(17	)		(11,000	)
	Provision (credit) charged to operations		19,848			12			3,035			87			(7	)		123			(140	)		10			22,968
	Balance at December 31,	$	22,433		$	12,541		$	24,467		$	776		$	3,812		$	4,249		$	750		$	1,133		$	70,161
		December 31, 2012
		Domestic																					Foreign
		Commercial			Commercial			Commercial			Commercial			Residential:			Residential:			Consumer			Foreign			Total
					real estate:			real estate:			real estate:			first lien			junior lien
					other			farmland &			multifamily
					construction &			commercial
					land
					development
		(Dollars in Thousands)
	Balance at December 31,	$	26,617		$	19,940		$	24,227		$	1,003		$	4,562		$	4,760		$	1,724		$	1,359		$	84,192
	Losses charge to allowance		(34,721	)		(7,617	)		(13,724	)		—			(227	)		(1,190	)		(756	)		(111	)		(58,346	)
	Recoveries credited to allowance		3,547			229			220			—			13			195			184			—			4,388
	Net losses charged to allowance		(31,174	)		(7,388	)		(13,504	)		—			(214	)		(995	)		(572	)		(111	)		(53,958	)
	Provision (credit) charged to operations		16,189			168			11,157			(309	)		42			683			137			(108	)		27,959
	Balance at December 31,	$	11,632		$	12,720		$	21,880		$	694		$	4,390		$	4,448		$	1,289		$	1,140		$	58,193
Loans individually or collectively evaluated for impairment and related allowance, by loan class
		December 31, 2014
		Loans individually						Loans collectively
		evaluated for						evaluated for
		impairment						impairment
		Recorded			Allowance			Recorded			Allowance
		Investment						Investment
		(Dollars in Thousands)
	Domestic
	Commercial	$	40,175		$	9,112		$	1,049,311		$	13,240
	Commercial real estate: other construction & land development		10,876			1,890			1,404,101			11,065
	Commercial real estate: farmland & commercial		14,166			1,219			1,887,233			17,464
	Commercial real estate: multifamily		835			—			115,864			846
	Residential: first lien		5,840			—			416,186			3,589
	Residential: junior lien		2,895			—			485,405			4,683
	Consumer		1,384			—			59,753			660
	Foreign		—			—			185,221			1,060
	Total	$	76,171		$	12,221		$	5,603,074		$	52,607
		December 31, 2013
		Loans individually						Loans collectively
		evaluated for						evaluated for
		impairment						impairment
		Recorded			Allowance			Recorded			Allowance
		Investment						Investment
		(Dollars in Thousands)
	Domestic
	Commercial	$	34,183		$	12,234		$	1,008,459		$	10,199
	Commercial real estate: other construction & land development		13,976			852			1,194,532			11,689
	Commercial real estate: farmland & commercial		16,038			2,916			1,734,001			21,551
	Commercial real estate: multifamily		295			—			101,803			776
	Residential: first lien		6,153			—			432,309			3,812
	Residential: junior lien		3,206			—			406,024			4,249
	Consumer		1,606			—			64,808			750
	Foreign		436			—			181,406			1,133
	Total	$	75,893		$	16,002		$	5,123,342		$	54,159
Loans accounted on non-accrual basis, by loan class
		December 31,
		2014			2013
		(Dollars in Thousands)
	Domestic
	Commercial	$	40,121		$	34,110
	Commercial real estate: other construction & land development		8,621			11,726
	Commercial real estate: farmland & commercial		11,903			13,775
	Commercial real estate: multifamily		835			295
	Residential: first lien		527			1,266
	Residential: junior lien		1,523			1,576
	Consumer		29			75
	Foreign		—			—
	Total non-accrual loans	$	63,559		$	62,823
Impaired loans, by loan class
		December 31, 2014
		Recorded			Unpaid			Related			Average			Interest
		Investment			Principal			Allowance			Recorded			Recognized
					Balance						Investment
		(Dollars in Thousands)
	Loans with Related Allowance
	Domestic
	Commercial	$	19,944		$	20,026		$	9,112		$	19,313		$	—
	Commercial real estate: other construction & land development		6,714			6,949			1,890			7,183			—
	Commercial real estate: farmland & commercial		5,107			5,257			1,219			6,790			92
	Total impaired loans with related allowance	$	31,765		$	32,232		$	12,221		$	33,286		$	92
		December 31, 2014
		Recorded			Unpaid			Average			Interest
		Investment			Principal			Recorded			Recognized
					Balance			Investment
		(Dollars in Thousands)
	Loans with No Related Allowance
	Domestic
	Commercial	$	20,231		$	20,260		$	18,563		$	4
	Commercial real estate: other construction & land development		4,162			4,270			4,882			74
	Commercial real estate: farmland & commercial		9,059			10,562			8,664			—
	Commercial real estate: multifamily		835			835			363			—
	Residential: first lien		5,840			6,034			6,293			273
	Residential: junior lien		2,895			2,915			3,035			90
	Consumer		1,384			1,386			1,402			3
	Foreign		—			—			—			—
	Total impaired loans with no related allowance	$	44,406		$	46,262		$	43,202		$	444
		December 31, 2013
		Recorded			Unpaid			Related			Average			Interest
		Investment			Principal			Allowance			Recorded			Recognized
					Balance						Investment
		(Dollars in Thousands)
	Loans with Related Allowance
	Domestic
	Commercial	$	17,178		$	17,177		$	12,234		$	18,019		$	38
	Commercial real estate: other construction & land development		6,818			6,825			852			6,058			—
	Commercial real estate: farmland & commercial		7,259			10,697			2,916			7,167			92
	Total impaired loans with related allowance	$	31,255		$	34,699		$	16,002		$	31,244		$	130
		December 31, 2013
		Recorded			Unpaid			Average			Interest
		Investment			Principal			Recorded			Recognized
					Balance			Investment
		(Dollars in Thousands)
	Loans with No Related Allowance
	Domestic
	Commercial	$	17,005		$	17,023		$	16,778		$	2
	Commercial real estate: other construction & land development		7,158			7,187			18,164			74
	Commercial real estate: farmland & commercial		8,779			9,949			7,313			—
	Commercial real estate: multifamily		295			295			322			—
	Residential: first lien		6,153			6,258			4,860			179
	Residential: junior lien		3,206			3,226			2,347			99
	Consumer		1,606			1,612			1,380			1
	Foreign		436			436			452			19
	Total impaired loans with no related allowance	$	44,638		$	45,986		$	51,616		$	374
Loans accounted for as trouble debt restructuring, by loan class
		December 31,			December 31,
		2014			2013
		(Dollars in Thousands)
	Domestic
	Commercial	$	2,500		$	150
	Commercial real estate: other construction & land development		2,254			8,860
	Commercial real estate: farmland & commercial		2,861			2,863
	Residential: first lien		5,313			4,887
	Residential: junior lien		1,371			1,631
	Consumer		1,354			1,531
	Foreign		—			436
	Total troubled debt restructuring	$	15,653		$	20,358
Information regarding the aging of past due loans, by loan class
		December 31, 2014
		30 - 59			60 - 89			90 Days or			90 Days or			Total			Current			Total
		Days			Days			Greater			greater &			Past due						Portfolio
											still accruing
		(Dollars in Thousands)
	Domestic
	Commercial	$	4,103		$	2,665		$	40,665		$	2,890		$	47,433		$	1,042,053		$	1,089,486
	Commercial real estate: other construction & land development		596			10			8,707			439			9,313			1,405,664			1,414,977
	Commercial real estate: farmland & commercial		2,905			7,131			10,724			1,711			20,760			1,880,639			1,901,399
	Commercial real estate: multifamily		351			—			856			21			1,207			115,492			116,699
	Residential: first lien		5,895			1,864			4,267			3,901			12,026			410,000			422,026
	Residential: junior lien		899			231			1,931			431			3,061			485,239			488,300
	Consumer		896			216			507			482			1,619			59,518			61,137
	Foreign		1,616			98			113			113			1,827			183,394			185,221
	Total past due loans	$	17,261		$	12,215		$	67,770		$	9,988		$	97,246		$	5,581,999		$	5,679,245
		December 31, 2013
		30 - 59			60 - 89			90 Days or			90 Days or			Total			Current			Total
		Days			Days			Greater			greater &			Past due						Portfolio
											still accruing
		(Dollars in Thousands)
	Domestic
	Commercial	$	4,240		$	538		$	36,066		$	2,051		$	40,844		$	1,001,798		$	1,042,642
	Commercial real estate: other construction & land development		1,042			—			9,942			62			10,984			1,197,524			1,208,508
	Commercial real estate: farmland & commercial		6,216			520			6,990			417			13,726			1,736,313			1,750,039
	Commercial real estate: multifamily		39			142			295			—			476			101,622			102,098
	Residential: first lien		4,758			3,046			4,541			3,518			12,345			426,117			438,462
	Residential: junior lien		606			198			1,900			368			2,704			406,526			409,230
	Consumer		1,523			469			803			781			2,795			63,619			66,414
	Foreign		1,467			417			—			—			1,884			179,958			181,842
	Total past due loans	$	19,891		$	5,330		$	60,537		$	7,197		$	85,758		$	5,113,477		$	5,199,235
Summary of the loan portfolio by credit quality indicator, by loan class
					December 31, 2014
		Pass			Special			Watch			Watch List—			Watch List—
					Review			List—Pass			Substandard			Impaired
					(Dollars in Thousands)
	Domestic
	Commercial	$	961,490		$	38,382		$	3,793		$	45,646		$	40,175
	Commercial real estate: other construction & land development		1,353,971			1,005			10,428			38,697			10,876
	Commercial real estate: farmland & commercial		1,754,741			11,674			23,453			97,365			14,166
	Commercial real estate: multifamily		115,729			—			—			135			835
	Residential: first lien		412,668			3,500			—			18			5,840
	Residential: junior lien		484,968			—			—			437			2,895
	Consumer		59,622			—			—			131			1,384
	Foreign		185,221			—			—			—			—
	Total	$	5,328,410		$	54,561		$	37,674		$	182,429		$	76,171
					December 31, 2013
		Pass			Special			Watch			Watch List—			Watch List—
					Review			List—Pass			Substandard			Impaired
					(Dollars in Thousands)
	Domestic
	Commercial	$	955,522		$	2,270		$	4,389		$	46,278		$	34,183
	Commercial real estate: other construction & land development		1,167,295			14,247			9,318			3,672			13,976
	Commercial real estate: farmland & commercial		1,635,179			56,438			21,912			20,472			16,038
	Commercial real estate: multifamily		100,948			—			—			855			295
	Residential: first lien		432,067			122			—			120			6,153
	Residential: junior lien		405,731			—			—			293			3,206
	Consumer		64,808			—			—			—			1,606
	Foreign		180,837			—			—			569			436
	Total	$	4,942,387		$	73,077		$	35,619		$	72,259		$	75,893

Bank_Premises_and_Equipment_Ta

Bank Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Bank Premises and Equipment
Summary of bank premises and equipment, by asset classification
		Estimated	2014			2013
		useful lives
			(Dollars in Thousands)
	Bank buildings and improvements	5 - 40 years	$	509,830		$	470,386
	Furniture, equipment and vehicles	1 - 20 years		269,861			260,932
	Land			125,414			128,805
	Real estate held for future expansion:
	Land, building, furniture, fixture and equipment	7 - 27 years		—			511
	Less: accumulated depreciation			(378,682	)		(355,792	)
	Bank premises and equipment, net		$	526,423		$	504,842

Goodwill_and_Other_Intangible_1

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill and Other Intangible Assets
Schedule of the entity's identified intangible assets
		Carrying		Accumulated		Net
		Amount		Amortization
		(Dollars in Thousands)
	December 31, 2014:
	Core deposit premium		58,675		58,379		296
		$		$		$
	Identified intangible (contract rights)		2,022		1,521		501
	Total identified intangibles	$	60,697	$	59,900	$	797
	December 31, 2013:
	Core deposit premium		58,675		56,298		2,377
		$		$		$
	Identified intangible (contract rights)		2,022		1,213		809
	Total identified intangibles	$	60,697	$	57,511	$	3,186
Schedule of estimated amortization expense for each of the five succeeding fiscal years and thereafter
		Total
		(in thousands)
	2015	$	452
	2016		295
	2017		25
	2018		25
	2019		—
	Thereafter		—
	Total	$	797

Deposits_Tables

Deposits (Tables)	12 Months Ended
	Dec. 31, 2014
Deposits.
Schedule of deposits and related interest expense
		2014		2013
		(Dollars in Thousands)
	Deposits:
	Demand—non-interest bearing
	Domestic	$	2,382,935	$	2,175,694
	Foreign		547,318		490,816
	Total demand non-interest bearing		2,930,253		2,666,510
	Savings and interest bearing demand
	Domestic		2,488,458		2,364,905
	Foreign		537,222		560,707
	Total savings and interest bearing demand		3,025,680		2,925,612
	Time, certificates of deposit $100,000 or more
	Domestic		835,792		856,700
	Foreign		864,346		938,940
	Less than $100,000
	Domestic		482,089		531,503
	Foreign		300,465		324,160
	Total time, certificates of deposit		2,482,692		2,651,303
	Total deposits	$	8,438,625	$	8,243,425
		2014		2013		2012
		(Dollars in Thousands)
	Interest expense:
	Savings and interest bearing demand
	Domestic	$	2,998	$	3,182	$	4,487
	Foreign		599		580		801
	Total savings and interest bearing demand		3,597		3,762		5,288
	Time, certificates of deposit $100,000 or more
	Domestic		4,615		5,761		8,263
	Foreign		4,529		5,590		9,148
	Less than $100,000
	Domestic		2,074		3,065		4,945
	Foreign		815		1,028		1,617
	Total time, certificates of deposit		12,033		15,444		23,973
	Total interest expense on deposits	$	15,630	$	19,206	$	29,261
Scheduled maturities of time deposits
		Total
		(in thousands)
	2015	$	2,177,266
	2016		203,928
	2017		76,206
	2018		23,481
	2019		1,751
	Thereafter		60
	Total	$	2,482,692
Scheduled maturities of time deposits in amounts of $100,000 or more	Scheduled maturities of time deposits in amounts of $100,000 or more at December 31, 2014, were as follows:
	Due within 3 months or less	$	631,083
	Due after 3 months and within 6 months		409,400
	Due after 6 months and within 12 months		443,860
	Due after 12 months		215,795
		$	1,700,138

Securities_Sold_Under_Repurcha1

Securities Sold Under Repurchase Agreements (Tables)	12 Months Ended
	Dec. 31, 2014
Securities Sold Under Repurchase Agreements
Schedule of repurchase agreements
		Collateral Securities				Repurchase Borrowing
		Book Value of		Fair Value of		Balance of		Weighted Average
		Securities Sold		Securities Sold		Liability		Interest Rate
		(Dollars in Thousands)
	December 31, 2014 term:
	Overnight agreements	$	366,731	$	370,704	$	236,077		0.16	%
	1 to 29 days		3,717		3,781		1,016		0.45
	30 to 90 days		13,399		13,628		6,705		0.38
	Over 90 days		743,323		746,305		614,552		3.83
	Total	$	1,127,170	$	1,134,418	$	858,350		2.79	%
	December 31, 2013 term:
	Overnight agreements	$	332,042	$	341,238	$	209,899		0.17	%
	1 to 29 days		27,954		28,288		18,666		0.4
	30 to 90 days		8,106		8,263		3,295		0.43
	Over 90 days		945,535		940,209		725,521		3.78
	Total	$	1,313,637	$	1,317,998	$	957,381		2.91	%

Other_Borrowed_Funds_Tables

Other Borrowed Funds (Tables)	12 Months Ended
	Dec. 31, 2014
Other Borrowed Funds
Schedule of other borrowed funds
			December 31,
			2014			2013
			(Dollars in Thousands)
	Federal Home Loan Bank advances—short-term
	Balance at year end		$	1,067,700		$	1,215,000
	Rate on balance outstanding at year end			0.15	%		0.17	%
	Average daily balance		$	1,077,973		$	833,868
	Average rate			0.16	%		0.16	%
	Maximum amount outstanding at any month end		$	1,352,500		$	1,280,500
	Federal Home Loan Bank advances—long-term(1)
	Balance at year end		$	6,244		$	8,950
	Rate on balance outstanding at year end			3.51	%		3.53	%
	Average daily balance		$	7,338		$	7,289
	Average rate			3.51	%		3.53	%
	Maximum amount outstanding at any month end		$	8,934		$	8,993
	-1	The amortization of the long-term advances is approximately $160,000 per year for each of the next five years and the final maturity date is January 3, 2028.

Junior_Subordinated_Deferrable1

Junior Subordinated Deferrable Interest Debentures (Tables)

12 Months Ended

Dec. 31, 2014

Junior Subordinated Deferrable Interest Debentures

Junior subordinated deferrable interest debentures, major types of business trusts

The following table illustrates key information about each of the Debentures and their interest rates at December 31, 2014:

Junior

Repricing

Interest

Interest

Maturity Date

Optional

Subordinated

Frequency

Rate

Rate Index(1)

Redemption Date(1)

Deferrable

Interest

Debentures

(in thousands)

Trust VI

$

25,774

Quarterly

3.68

%

LIBOR + 3.45

Nov-32

Feb-08

Trust VIII

25,774

Quarterly

3.28

%

LIBOR + 3.05

Oct-33

Oct-08

Trust IX

41,238

Quarterly

1.86

%

LIBOR + 1.62

Oct-36

Oct-11

Trust X

34,021

Quarterly

1.88

%

LIBOR + 1.65

Feb-37

Feb-12

Trust XI

27,990

Quarterly

1.86

%

LIBOR + 1.62

Jul-37

Jul-12

Trust XII

20,619

Quarterly

1.69

%

LIBOR + 1.45

Sep-37

Sep-12

$

175,416

-1

The Capital Securities may be redeemed in whole or in part on any interest payment date after the Optional Redemption Date.

Earnings_per_Share_EPS_Tables

Earnings per Share ("EPS") (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings per Share ("EPS")
Schedule of calculation of the basic EPS and the diluted EPS
		Net Income		Shares		Per Share
		(Numerator)		(Denominator)		Amount
		(Dollars in Thousands,
		Except Per Share Amounts)
	December 31, 2014:
	Basic EPS
	Net income available to common shareholders	$	153,151		66,872,500	$	2.29
	Potential dilutive common shares and warrants				183,956
			—
	Diluted EPS	$	153,151		67,056,456	$	2.28
	December 31, 2013:
	Basic EPS
	Net income available to common shareholders	$	126,351		67,195,180	$	1.88
	Potential dilutive common shares				119,679
			—
	Diluted EPS	$	126,351		67,314,859	$	1.88
	December 31, 2012:
	Basic EPS
	Net income available to common shareholders	$	93,473		67,236,681	$	1.39
	Potential dilutive common shares				77,282
			—
	Diluted EPS	$	93,473		67,313,963	$	1.39

International_Operations_Table

International Operations (Tables)	12 Months Ended
	Dec. 31, 2014
International Operations
Summary of assets attributable to international operations
		2014			2013
		(Dollars in Thousands)
	Loans:
	Commercial	$	150,078		$	142,145
	Others		35,143			39,697
			185,221			181,842
	Less allowance for probable loan losses		(1,060	)		(1,133	)
	Net loans	$	184,161		$	180,709
	Accrued interest receivable	$	702		$	617

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Taxes
Schedule of current and deferred portions of net income tax expense
		2014			2013			2012
		(Dollars in Thousands)
	Current
	U.S.	$	72,561		$	59,583		$	40,375
	State		5,252			(1,530	)		2,234
	Foreign		1			3			33
	Total current taxes		77,814			58,056			42,642
	Deferred
	U.S.		(969	)		(1,692	)		7,928
	State		(58	)		(125	)		(5	)
	Total deferred taxes		(1,027	)		(1,817	)		7,923
	Total income taxes	$	76,787		$	56,239		$	50,565
Schedule of income tax expense differences from the amount computed by applying the U.S. Federal income tax rate to income before income taxes
		2014			2013			2012
		(Dollars in Thousands)
	Computed expected tax expense	$	80,560		$	64,183		$	55,634
	Change in taxes resulting from:
	Tax-exempt interest income		(4,554	)		(4,828	)		(4,381	)
	State tax, net of federal income taxes and tax credit		3,377			(110	)		1,446
	Tax refunds		—			(966	)		—
	Other investment income		(3,615	)		(2,656	)		(2,691	)
	Other		1,019			616			557
	Actual tax expense	$	76,787		$	56,239		$	50,565
Schedule of tax effects of temporary difference that give rise to significant portions of the deferred tax assets and deferred tax liabilities
		2014			2013
		(Dollars in Thousands)
	Deferred tax assets:
	Loans receivable, principally due to the allowance for probable loan losses	$	24,849		$	25,365
	Other real estate owned		3,453			3,878
	Impairment charges on available-for-sale securities		5,618			5,327
	Accrued expenses		268			399
	Net unrealized gains on available for sale investment securities		—			24,235
	Other		5,809			4,816
	Total deferred tax assets		39,997			64,020
	Deferred tax liabilities:
	Bank premises and equipment, principally due to differences on depreciation		(18,314	)		(20,729	)
	Net unrealized gains on available for sale investment securities		(6,182	)		—
	Identified intangible assets and goodwill		(18,787	)		(18,051	)
	Other		(12,303	)		(11,476	)
	Total deferred tax liabilities		(55,586	)		(50,256	)
	Net deferred tax asset (liability)	$	(15,589	)	$	13,764

Stock_Options_Tables

Stock Options (Tables)	12 Months Ended
	Dec. 31, 2014
Stock Options
Schedule of Black-Scholes-Merton option valuation model assumptions
		2014			2013
	Expected Life (Years)		7.63			7.63
	Dividend yield		2.01	%		2.33	%
	Interest rate		2.28	%		2.86	%
	Volatility		47.36	%		47.28	%
Summary of option activity under stock option plans
		Number of			Weighted			Weighted		Aggregate
		options			average			average		intrinsic
					exercise			remaining		value ($)
					price			contractual
								term (years)
										(in Thousands)
	Options outstanding at December 31, 2013		515,143		$	15.98
	Plus: Options granted		564,750			21.48
	Less:
	Options exercised		40,385			13.75
	Options expired		15,125			27.02
	Options forfeited		30,494			18.84
	Options outstanding at December 31, 2014		993,889			18.94			6.62	$	7,567
	Options fully vested and exercisable at December 31, 2014		250,487		$	16.76			2.28	$	2,461
Schedule of other information pertaining to option activity
		Twelve Months Ended December 31,
		2014			2013			2012
	Weighted average grant date fair value of stock options granted	$	9.07		$	9.05		$	8.71
	Total fair value of stock options vested	$	376,000		$	480,000		$	524,000
	Total intrinsic value of stock options exercised	$	468,000		$	171,000		$	41,000

Commitments_Contingent_Liabili1

Commitments, Contingent Liabilities and Other Matters (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments, Contingent Liabilities and Other Matters
Schedule of future minimum lease payments due under non-cancellable operating leases
		Total
		(in thousands)
	2015	$	3,505
	2016		2,454
	2017		1,168
	2018		631
	2019		157
	Thereafter		122
	Total	$	8,037

Financial_Instruments_with_Off1

Financial Instruments with Off-Statement of Condition Risk and Concentrations of Credit Risk (Tables)	12 Months Ended
	Dec. 31, 2014
Financial Instruments with Off-Statement of Condition Risk and Concentrations of Credit Risk
Schedule of financial amounts of instruments, whose contract amounts represent credit risks	At December 31, 2014, the following financial amounts of instruments, whose contract amounts represent credit risks, were outstanding:
	Commitments to extend credit	$	1,662,516,000
	Credit card lines		16,687,000
	Standby letters of credit		103,793,000
	Commercial letters of credit		10,879,000

Capital_Requirements_Tables

Capital Requirements (Tables)	12 Months Ended
	Dec. 31, 2014
Capital Requirements
Schedule of the Company's and the bank subsidiaries' actual capital amounts and ratios
		Actual					For Capital Adequacy					To Be Well-Capitalized
							Purposes					Under Prompt Corrective
												Action Provisions
		Amount		Ratio			Amount		Ratio			Amount		Ratio
							(greater than		(greater than			(greater than		(greater than
							or equal to)		or equal to)			or equal to)		or equal to)
		(Dollars in Thousands)
	As of December 31, 2014:
	Total Capital (to Risk Weighted Assets):
	Consolidated	$	1,524,998		20.24	%	$	602,847		8.00	%		N/A		N/A
	International Bank of Commerce, Laredo		1,131,528		17.31			523,006		8.00		$	653,757		10.00	%
	International Bank of Commerce, Brownsville		151,489		28.60			42,381		8.00			52,976		10.00
	International Bank of Commerce, Zapata		60,946		33.83			14,412		8.00			18,041		10.00
	Commerce Bank		68,291		37.42			14,600		8.00			18,251		10.00
	Tier 1 Capital (to Risk Weighted Assets):
	Consolidated	$	1,457,068		19.34	%	$	301,424		4.00	%		N/A		N/A
	International Bank of Commerce, Laredo		1,071,360		16.39			261,503		4.00		$	392,254		6.00	%
	International Bank of Commerce, Brownsville		145,584		27.48			21,190		4.00			31,785		6.00
	International Bank of Commerce, Zapata		60,035		33.33			7,206		4.00			10,809		6.00
	Commerce Bank		67,347		36.90			7,300		4.00			10,950		6.00
	Tier 1 Capital (to Average Assets):
	Consolidated	$	1,457,068		12.33	%	$	472,864		4.00	%	$	N/A		N/A
	International Bank of Commerce, Laredo		1,071,360		11.22			381,804		4.00			477,255		5.00	%
	International Bank of Commerce, Brownsville		145,584		13.96			41,717		4.00			52,146		5.00
	International Bank of Commerce, Zapata		60,035		10.88			22,081		4.00			27,602		5.00
	Commerce Bank		67,347		12.04			22,373		4.00			27,966		5.00
		Actual					For Capital Adequacy					To Be Well-Capitalized
							Purposes					Under Prompt Corrective
												Action Provisions
		Amount		Ratio			Amount		Ratio			Amount		Ratio
							(greater than		(greater than			(greater than		(greater than
							or equal to)		or equal to)			or equal to)		or equal to)
		(Dollars in Thousands)
	As of December 31, 2013:
	Total Capital (to Risk Weighted Assets):
	Consolidated	$	1,442,837		20.36	%	$	566,870		8.00	%		N/A		N/A
	International Bank of Commerce, Laredo		1,035,189		16.96			488,303		8.00		$	610,378		10.00	%
	International Bank of Commerce, Brownsville		143,879		27.63			41,652		8.00			52,065		10.00
	International Bank of Commerce, Zapata		57,675		32.65			14,130		8.00			17,663		10.00
	Commerce Bank		64,585		36.45			14,175		8.00			17,719		10.00
	Tier 1 Capital (to Risk Weighted Assets):
	Consolidated	$	1,369,657		19.33	%	$	283,435		4.00	%		N/A		N/A
	International Bank of Commerce, Laredo		969,731		15.89			244,151		4.00		$	366,227		6.00	%
	International Bank of Commerce, Brownsville		138,467		26.60			20,826		4.00			31,239		6.00
	International Bank of Commerce, Zapata		56,459		31.96			7,065		4.00			10,598		6.00
	Commerce Bank		63,491		35.83			7,087		4.00			10,631		6.00
	Tier 1 Capital (to Average Assets):
	Consolidated	$	1,369,657		11.61	%	$	472,044		4.00	%	$	N/A		N/A
	International Bank of Commerce, Laredo		969,731		10.09			384,497		4.00			480,622		5.00	%
	International Bank of Commerce, Brownsville		138,467		13.33			41,553		4.00			51,942		5.00
	International Bank of Commerce, Zapata		56,459		10.64			21,219		4.00			26,523		5.00
	Commerce Bank		63,491		11.88			21,372		4.00			26,715		5.00

Fair_Value_Tables

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value
Assets and liabilities measured at fair value on a recurring basis
					Fair Value Measurements at
					Reporting Date Using
					(in thousands)
		Assets/Liabilities			Quoted		Significant		Significant
		Measured at			Prices in		Other		Unobservable
		Fair Value			Active		Observable		Inputs
		December 31,			Markets for		Inputs		(Level 3)
		2014			Identical		(Level 2)
					Assets
					(Level 1)
	Measured on a recurring basis:
	Assets:
	Available for sale securities
	Residential mortgage-backed securities	$	4,600,372		$	—	$	4,576,309	$	24,063
	States and political subdivisions		282,276			—		282,276		—
	Other		49,315			29,315		20,000		—
		$	4,931,963		$	29,315	$	4,878,585	$	24,063
					Fair Value Measurements at
					Reporting Date Using
					(in thousands)
		Assets/Liabilities			Quoted		Significant		Significant
		Measured at			Prices in		Other		Unobservable
		Fair Value			Active		Observable		Inputs
		December 31,			Markets for		Inputs		(Level 3)
		2013			Identical		(Level 2)
					Assets
					(Level 1)
	Measured on a recurring basis:
	Assets:
	Available for sale securities
	Residential mortgage-backed securities	$	5,027,701		$	—	$	4,999,849	$	27,852
	States and political subdivisions		248,410			—		248,410		—
	Other		28,468			28,468		—		—
		$	5,304,579		$	28,468	$	5,248,259	$	27,852
Reconciliation of activity for mortgage-backed securities on a net basis	The following table presents a reconciliation of activity for such mortgage-backed securities on a net basis (Dollars in thousands):
	Balance at December 31, 2013	$	27,852
	Principal paydowns		(4,154	)
	Total unrealized gains (losses) included in:
	Other comprehensive income		1,182
	Impairment realized in earnings		(817	)
	Balance at December 31, 2014	$	24,063
Assets measured at fair value on a non-recurring basis
					Fair Value Measurements at Reporting
					Date Using
					(in thousands)
		Assets/Liabilities			Quoted		Significant		Significant		Net
		Measured at			Prices in		Other		Unobservable		(Credit)
		Fair Value			Active		Observable		Inputs		Provision
		Year ended			Markets for		Inputs		(Level 3)		During
		December 31,			Identical		(Level 2)				Period
		2014			Assets
					(Level 1)
	Measured on a non-recurring basis:
	Assets:
	Impaired loans	$	29,501		$	—	$	—	$	29,501	$	(1,557	)
	Other real estate owned		6,112			—		—		6,112		597
					Fair Value Measurements at Reporting
					Date Using
					(in thousands)
		Assets/Liabilities			Quoted		Significant		Significant		Net
		Measured at			Prices in		Other		Unobservable		Provision
		Fair Value			Active		Observable		Inputs		During
		Year ended			Markets		Inputs		(Level 3)		Period
		December 31,			for Identical		(Level 2)
		2013			Assets
					(Level 1)
	Measured on a non-recurring basis:
	Assets:
	Impaired loans	$	28,391		$	—	$	—	$	28,391	$	13,229
	Other real estate owned		16,329			—		—		16,329		1,204

International_Bancshares_Corpo3

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Condition (Tables)	12 Months Ended
	Dec. 31, 2014
International Bancshares Corporation (Parent Company Only) Financial Information Statements of Condition
Schedule of condensed statements of condition of Parent Company	(Dollars in Thousands)
		2014			2013
	ASSETS
	Cash		9,252			8,106
		$			$
	Other investments		69,042			62,381
	Notes receivable		204			313
	Investment in subsidiaries		1,691,553			1,556,932
	Other assets		50			197
	Total assets	$	1,770,101		$	1,627,929
	LIABILITIES AND SHAREHOLDERS' EQUITY
	Liabilities:
	Junior subordinated deferrable interest debentures	$	175,416		$	190,726
	Due to IBC Trading		21			21
	Other liabilities		14,006			12,774
	Total liabilities		189,443			203,521
	Shareholders' equity:
	Common shares		95,784			95,744
	Surplus		165,520			163,947
	Retained earnings		1,585,389			1,467,000
	Accumulated other comprehensive income (loss)		11,397			(43,774	)
			1,858,090			1,682,917
	Less cost of shares in treasury		(277,432			(258,509
				)			)
	Total shareholders' equity		1,580,658			1,424,408
	Total liabilities and shareholders' equity	$	1,770,101		$	1,627,929

International_Bancshares_Corpo4

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Income (Tables)	12 Months Ended
	Dec. 31, 2014
International Bancshares Corporation (Parent Company Only) Financial Information Statements of Income
Schedule of condensed statements of income of Parent Company	(Dollars in Thousands)
		2014		2013		2012
	Income:
	Dividends from subsidiaries	$	71,389	$	30,000	$	229,250
	Interest income on notes receivable		15		18		27
	Interest income on other investments		6,862		12,301		6,759
	Other interest income		—		—		18
	Other		1,923		26		686
	Total income		80,189		42,345		236,740
	Expenses:
	Interest expense (Debentures)		4,264		4,665		6,595
	Other		1,099		1,889		3,867
	Total expenses		5,363		6,554		10,462
	Income before federal income taxes and equity in undistributed net income of subsidiaries		74,826		35,791		226,278
	Income tax expense (benefit)		1,370		2,529		(738	)
	Income before equity in undistributed net income of subsidiaries		73,456		33,262		227,016
	Equity in undistributed (distributed) net income of subsidiaries		79,695		93,089		(119,181
								)
	Net income		153,151		126,351		107,835
	Preferred stock dividends and discount accretion		—		—		14,362
	Net income available to common shareholders	$	153,151	$	126,351	$	93,473

International_Bancshares_Corpo5

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Cash Flows (Tables)	12 Months Ended
	Dec. 31, 2014
International Bancshares Corporation (Parent Company Only) Financial Information Statements of Cash Flows
Schedule of condensed statements of cash flows of Parent Company	(Dollars in Thousands)
		2014			2013			2012
	Operating activities:
	Net income	$	153,151		$	126,351		$	107,835
	Adjustments to reconcile net income to net cash provided by operating activities:
	Impairment charges on available for sale securities		254			754			—
	Stock compensation expense		1,058			414			474
	Increase (decrease) in other liabilities		416			(969	)		6,711
	Equity in (undistributed) distributed net income of subsidiaries		(79,695	)		(93,089	)		119,181
	Net cash provided by operating activities		75,184			33,461			234,201
	Investing activities:
	Principal collected on mortgage-backed securities		1,301			1,207			1,985
	Net decrease in notes receivable		109			96			86
	(Increase) decrease in other assets and other investments		(7,008	)		432			6,418
	Net cash (used in) provided by investing activities		(5,598	)		1,735			8,489
	Financing activities:
	Repayment of trust preferred securities		(15,310	)		—			—
	Redemption of preferred shares		—			—			(216,000	)
	Proceeds from stock transactions		555			265			51
	Payments of cash dividends—common		(34,762	)		(28,894	)		(26,894	)
	Payments of cash dividends—preferred		—			—			(10,260	)
	Purchase of treasury stock		(18,923	)		—			(1,716	)
	Net cash used in financing activities		(68,440	)		(28,629	)		(254,819	)
	Increase (decrease) in cash		1,146			6,567			(12,129	)
	Cash at beginning of year		8,106			1,539			13,668
	Cash at end of year	$	9,252		$	8,106		$	1,539

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Details) (USD $)	0 Months Ended	12 Months Ended
	Oct. 01, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
		item
Summary of Significant Accounting Policies
Number of insurance-related subsidiaries		2
Investment Securities
Number of components in which other-than-temporary impairment is segregated		2
Non-Accrual Loans
Period of charge off for past due unsecured consumer loans		90 days
Minimum period that past due unsecured loans outstanding may not be placed on nonaccrual status under special circumstances		90 days
Maximum period of non-consumer loans outstanding that is used to evaluate whether loans should be placed on non-accrual status		90 days
Other Real Estate Owned
Other real estate owned		$69,872,000	$85,879,000
Income Taxes
Percentage of likelihood of realization of recognized tax benefit		50.00%
Liability for unrecognized tax benefits		0	0
Interest expense related to uncertain tax positions		0	0	0
Penalties related to uncertain tax positions		0	0	0
Goodwill and Identified Intangible Assets
Goodwill impairment loss	0
Impairment of identified intangible assets		$0
Segments of an Enterprise and Related Information
Number of operating segments		1
Number of active operating bank subsidiaries		4

Investment_Securities_Details

Investment Securities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Held-to-maturity securities
Amortized cost	$2,400	$2,400
Estimated fair value	2,400	2,400
Carrying value	2,400	2,400
Available-for-sale securities
Amortized cost	4,914,428	5,372,594
Gross unrealized gains	68,516	65,104
Gross unrealized losses	-50,981	-133,119
Total investment securities	4,931,963	5,304,579
Assets/Liabilities Measured at Fair Value
Available-for-sale securities
Total investment securities	4,931,963	5,304,579
Carrying value
Available-for-sale securities
Total investment securities	4,931,963	5,304,579
Other securities
Held-to-maturity securities
Amortized cost	2,400	2,400
Estimated fair value	2,400	2,400
Carrying value	2,400	2,400
Available-for-sale securities
Amortized cost	20,000
Other securities | Assets/Liabilities Measured at Fair Value
Available-for-sale securities
Total investment securities	20,000
Other securities | Carrying value
Available-for-sale securities
Total investment securities	20,000
Residential mortgage-backed securities
Available-for-sale securities
Amortized cost	4,597,590	5,096,165
Gross unrealized gains	47,960	56,110
Gross unrealized losses	-45,178	-124,574
Residential mortgage-backed securities | Assets/Liabilities Measured at Fair Value
Available-for-sale securities
Total investment securities	4,600,372	5,027,701
Residential mortgage-backed securities | Carrying value
Available-for-sale securities
Total investment securities	4,600,372	5,027,701
Mortgage-backed securities by Ginnie Mae
Available-for-sale securities
Total investment securities	1,503,774	1,799,807
Mortgage-backed securities by Fannie Mae and Freddie Mac
Available-for-sale securities
Total investment securities	3,072,535	3,200,042
Mortgage-backed securities by non-government entities
Available-for-sale securities
Total investment securities	24,063	27,852
States and political subdivisions
Available-for-sale securities
Amortized cost	268,763	248,354
Gross unrealized gains	19,131	8,063
Gross unrealized losses	-5,618	-8,007
States and political subdivisions | Assets/Liabilities Measured at Fair Value
Available-for-sale securities
Total investment securities	282,276	248,410
States and political subdivisions | Carrying value
Available-for-sale securities
Total investment securities	282,276	248,410
Other
Available-for-sale securities
Amortized cost	28,075	28,075
Gross unrealized gains	1,425	931
Gross unrealized losses	-185	-538
Other | Assets/Liabilities Measured at Fair Value
Available-for-sale securities
Total investment securities	29,315	28,468
Other | Carrying value
Available-for-sale securities
Total investment securities	$29,315	$28,468

Investment_Securities_Details_

Investment Securities (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Held-to-maturity debt securities amortized cost disclosures
Due in one year or less, held-to-maturity debt securities amortized cost	$1,075,000
Due after one year through five years, held-to-maturity debt securities amortized cost	1,325,000
Amortized cost, held-to-maturity debt securities	2,400,000	2,400,000
Held-to-maturity debt securities, Estimated fair value disclosures
Due in one year or less, held-to-maturity debt securities, Estimated fair value	1,075,000
Due after one year through five years, held-to-maturity debt securities, Estimated fair value	1,325,000
Estimated fair value	2,400,000	2,400,000
Available-for-sale debt securities amortized cost disclosures
Due after five years through ten years, available-for-sale debt securities amortized cost	735,000
Due after ten years, available-for-sale debt securities amortized cost	288,028,000
Residential mortgage-backed securities, amortized cost	4,597,590,000
Equity securities, amortized cost	28,075,000
Amortized cost, Available for sale securities	4,914,428,000	5,372,594,000
Available for sale debt securities, Estimated Fair Value Disclosures
Due after five years through ten years, available-for-sale debt securities, Estimated Fair Value	812,000
Due after ten years, available-for-sale debt securities, Estimated Fair Value	301,464,000
Residential mortgage-backed securities, Estimated Fair Value	4,600,372,000
Equity securities, Estimated Fair Value	29,315,000
Estimated fair value, Available for sale securities	4,931,963,000	5,304,579,000
Amortized cost of available for sale investment securities pledged	2,182,579,000
Fair value of available for sale investment securities pledged	2,196,169,000
Proceeds from sales and calls of available for sale securities	621,588,000	178,123,000	1,382,231,000
Proceeds from sales of mortgage-backed securities	620,933,000	177,623,000	1,338,723,000
Gross gains realized on sales	9,479,000	9,601,000	38,447,000
Gross losses realized on sales	8,196,000	0	1,000
Impairment charges on available for sale securities	817,000	1,374,000	1,039,000
Impairment charges on available-for-sale investment securities, after tax	$531,050	$893,100	$675,000

Investment_Securities_Details_1

Investment Securities (Details 3) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Available for sale:
Fair value, less than 12 months	$816,979	$2,534,354
Unrealized losses, less than 12 months	-5,008	-101,585
Fair value, 12 months or more	1,872,077	434,554
Unrealized losses, 12 months or more	-45,973	-31,534
Fair value, total	2,689,056	2,968,908
Unrealized losses, total	-50,981	-133,119
Residential mortgage-backed securities
Available for sale:
Fair value, less than 12 months	808,072	2,459,565
Unrealized losses, less than 12 months	-4,910	-98,022
Fair value, 12 months or more	1,836,218	420,262
Unrealized losses, 12 months or more	-40,268	-26,552
Fair value, total	2,644,290	2,879,827
Unrealized losses, total	-45,178	-124,574
States and political subdivisions
Available for sale:
Fair value, less than 12 months	8,833	55,327
Unrealized losses, less than 12 months	-97	-3,025
Fair value, 12 months or more	27,793	14,292
Unrealized losses, 12 months or more	-5,521	-4,982
Fair value, total	36,626	69,619
Unrealized losses, total	-5,618	-8,007
Other
Available for sale:
Fair value, less than 12 months	74	19,462
Unrealized losses, less than 12 months	-1	-538
Fair value, 12 months or more	8,066
Unrealized losses, 12 months or more	-184
Fair value, total	8,140	19,462
Unrealized losses, total	($185)	($538)

Investment_Securities_Details_2

Investment Securities (Details 4) (Available for sale investments, USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Available for sale investments
Reconciliation of credit-related impairment charges on investments recognized in earnings
Balance at the beginning	$11,806	$10,432	$9,393
Impairment charges recognized during period	817	1,374	1,039
Balance at the end	$12,623	$11,806	$10,432

Loans_Details

Loans (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Summary of loans, by loan type
Total loans	$5,679,245	$5,199,235
Commercial, financial and agricultural
Summary of loans, by loan type
Total loans	3,107,584	2,894,779
Real estate - mortgage
Summary of loans, by loan type
Total loans	910,326	847,692
Commercial real estate: other construction and land development
Summary of loans, by loan type
Total loans	1,414,977	1,208,508
Consumer Loan
Summary of loans, by loan type
Total loans	61,137	66,414
Foreign
Summary of loans, by loan type
Total loans	$185,221	$181,842

Allowance_for_Probable_Loan_Lo2

Allowance for Probable Loan Losses (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for probable loan losses
Balance at the beginning of the period	$70,161	$58,193	$84,192
Losses charged to allowance	-23,465	-14,455	-58,346
Recoveries credited to allowance	3,709	3,455	4,388
Net losses charged to allowance	-19,756	-11,000	-53,958
Provision (credit) charged to operations	14,423	22,968	27,959
Balance at the end of the period	64,828	70,161	58,193
Commercial
Allowance for probable loan losses
Balance at the beginning of the period	22,433	11,632	26,617
Losses charged to allowance	-19,110	-11,737	-34,721
Recoveries credited to allowance	2,979	2,690	3,547
Net losses charged to allowance	-16,131	-9,047	-31,174
Provision (credit) charged to operations	16,050	19,848	16,189
Balance at the end of the period	22,352	22,433	11,632
Commercial real estate: other construction and land development
Allowance for probable loan losses
Balance at the beginning of the period	12,541	12,720	19,940
Losses charged to allowance	-680	-278	-7,617
Recoveries credited to allowance	72	87	229
Net losses charged to allowance	-608	-191	-7,388
Provision (credit) charged to operations	1,022	12	168
Balance at the end of the period	12,955	12,541	12,720
Risks related to family development loans
Minimum number of family development loans	1
Maximum number of family development loans	4
Commercial real estate: farmland and commercial
Allowance for probable loan losses
Balance at the beginning of the period	24,467	21,880	24,227
Losses charged to allowance	-1,893	-600	-13,724
Recoveries credited to allowance	107	152	220
Net losses charged to allowance	-1,786	-448	-13,504
Provision (credit) charged to operations	-3,998	3,035	11,157
Balance at the end of the period	18,683	24,467	21,880
Commercial real estate: multifamily
Allowance for probable loan losses
Balance at the beginning of the period	776	694	1,003
Losses charged to allowance		-5
Net losses charged to allowance		-5
Provision (credit) charged to operations	70	87	-309
Balance at the end of the period	846	776	694
Residential: first lien
Allowance for probable loan losses
Balance at the beginning of the period	3,812	4,390	4,562
Losses charged to allowance	-351	-632	-227
Recoveries credited to allowance	49	61	13
Net losses charged to allowance	-302	-571	-214
Provision (credit) charged to operations	79	-7	42
Balance at the end of the period	3,589	3,812	4,390
Residential: junior lien
Allowance for probable loan losses
Balance at the beginning of the period	4,249	4,448	4,760
Losses charged to allowance	-661	-620	-1,190
Recoveries credited to allowance	242	298	195
Net losses charged to allowance	-419	-322	-995
Provision (credit) charged to operations	853	123	683
Balance at the end of the period	4,683	4,249	4,448
Consumer Loan
Allowance for probable loan losses
Balance at the beginning of the period	750	1,289	1,724
Losses charged to allowance	-719	-561	-756
Recoveries credited to allowance	210	162	184
Net losses charged to allowance	-509	-399	-572
Provision (credit) charged to operations	419	-140	137
Balance at the end of the period	660	750	1,289
Foreign
Allowance for probable loan losses
Balance at the beginning of the period	1,133	1,140	1,359
Losses charged to allowance	-51	-22	-111
Recoveries credited to allowance	50	5
Net losses charged to allowance	-1	-17	-111
Provision (credit) charged to operations	-72	10	-108
Balance at the end of the period	$1,060	$1,133	$1,140

Allowance_for_Probable_Loan_Lo3

Allowance for Probable Loan Losses (Details 2) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans individually evaluated for impairment, Recorded Investment	$76,171	$75,893
Loans individually evaluated for impairment, Allowance	12,221	16,002
Loans collectively evaluated for impairment, Recorded Investment	5,603,074	5,123,342
Loans collectively evaluated for impairment, Allowance	52,607	54,159
Commercial
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans individually evaluated for impairment, Recorded Investment	40,175	34,183
Loans individually evaluated for impairment, Allowance	9,112	12,234
Loans collectively evaluated for impairment, Recorded Investment	1,049,311	1,008,459
Loans collectively evaluated for impairment, Allowance	13,240	10,199
Commercial real estate: other construction and land development
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans individually evaluated for impairment, Recorded Investment	10,876	13,976
Loans individually evaluated for impairment, Allowance	1,890	852
Loans collectively evaluated for impairment, Recorded Investment	1,404,101	1,194,532
Loans collectively evaluated for impairment, Allowance	11,065	11,689
Commercial real estate: farmland and commercial
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans individually evaluated for impairment, Recorded Investment	14,166	16,038
Loans individually evaluated for impairment, Allowance	1,219	2,916
Loans collectively evaluated for impairment, Recorded Investment	1,887,233	1,734,001
Loans collectively evaluated for impairment, Allowance	17,464	21,551
Commercial real estate: multifamily
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans individually evaluated for impairment, Recorded Investment	835	295
Loans collectively evaluated for impairment, Recorded Investment	115,864	101,803
Loans collectively evaluated for impairment, Allowance	846	776
Residential: first lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans individually evaluated for impairment, Recorded Investment	5,840	6,153
Loans collectively evaluated for impairment, Recorded Investment	416,186	432,309
Loans collectively evaluated for impairment, Allowance	3,589	3,812
Residential: junior lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans individually evaluated for impairment, Recorded Investment	2,895	3,206
Loans collectively evaluated for impairment, Recorded Investment	485,405	406,024
Loans collectively evaluated for impairment, Allowance	4,683	4,249
Consumer Loan
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans individually evaluated for impairment, Recorded Investment	1,384	1,606
Loans collectively evaluated for impairment, Recorded Investment	59,753	64,808
Loans collectively evaluated for impairment, Allowance	660	750
Foreign
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans individually evaluated for impairment, Recorded Investment		436
Loans collectively evaluated for impairment, Recorded Investment	185,221	181,406
Loans collectively evaluated for impairment, Allowance	$1,060	$1,133

Allowance_for_Probable_Loan_Lo4

Allowance for Probable Loan Losses (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loan loss allowances, financing receivable past due
Non-accrual loans, total	$63,559,000	$62,823,000	$71,768,000
Reduced interest income on non-accrual loans	4,013,000	4,088,000	2,549,000
Accruing loans contractually past due 90 days or more as to principal or interest payments	9,988,000	7,197,000	15,033,000
Commercial
Loan loss allowances, financing receivable past due
Non-accrual loans, total	40,121,000	34,110,000
Accruing loans contractually past due 90 days or more as to principal or interest payments	2,890,000	2,051,000
Commercial real estate: other construction and land development
Loan loss allowances, financing receivable past due
Non-accrual loans, total	8,621,000	11,726,000
Accruing loans contractually past due 90 days or more as to principal or interest payments	439,000	62,000
Commercial real estate: farmland and commercial
Loan loss allowances, financing receivable past due
Non-accrual loans, total	11,903,000	13,775,000
Accruing loans contractually past due 90 days or more as to principal or interest payments	1,711,000	417,000
Commercial real estate: multifamily
Loan loss allowances, financing receivable past due
Non-accrual loans, total	835,000	295,000
Accruing loans contractually past due 90 days or more as to principal or interest payments	21,000
Residential: first lien
Loan loss allowances, financing receivable past due
Non-accrual loans, total	527,000	1,266,000
Accruing loans contractually past due 90 days or more as to principal or interest payments	3,901,000	3,518,000
Residential: junior lien
Loan loss allowances, financing receivable past due
Non-accrual loans, total	1,523,000	1,576,000
Accruing loans contractually past due 90 days or more as to principal or interest payments	431,000	368,000
Consumer Loan
Loan loss allowances, financing receivable past due
Non-accrual loans, total	29,000	75,000
Accruing loans contractually past due 90 days or more as to principal or interest payments	$482,000	$781,000

Allowance_for_Probable_Loan_Lo5

Allowance for Probable Loan Losses (Details 4) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Interest Recognized
Loans accounted for as troubled debt restructuring	$15,653	$20,358
Period of charge off for past due unsecured commercial loans	90 days
Total troubled debt restructuring	15,653	20,358
Class of financing receivable
Recorded investment:
Total impaired loans with related allowance	31,765	31,255
Total impaired loans with no related allowance	44,406	44,638
Unpaid principal balance:
Total impaired loans with an allowance recorded	32,232	34,699
Total impaired loans with no related allowance recorded	46,262	45,986
Related Allowance	12,221	16,002
Average recorded investment:
Total impaired loans with an allowance recorded	33,286	31,244
Total impaired loans with no related allowance recorded	43,202	51,616
Interest Recognized
Total impaired loans with an allowance recorded	92	130
Total impaired loans with no related allowance recorded	444	374
Commercial
Interest Recognized
Loans accounted for as troubled debt restructuring	2,500	150
Total troubled debt restructuring	2,500	150
Commercial | Class of financing receivable
Recorded investment:
Total impaired loans with related allowance	19,944	17,178
Total impaired loans with no related allowance	20,231	17,005
Unpaid principal balance:
Total impaired loans with an allowance recorded	20,026	17,177
Total impaired loans with no related allowance recorded	20,260	17,023
Related Allowance	9,112	12,234
Average recorded investment:
Total impaired loans with an allowance recorded	19,313	18,019
Total impaired loans with no related allowance recorded	18,563	16,778
Interest Recognized
Total impaired loans with an allowance recorded		38
Total impaired loans with no related allowance recorded	4	2
Commercial real estate: other construction and land development
Interest Recognized
Loans accounted for as troubled debt restructuring	2,254	8,860
Total troubled debt restructuring	2,254	8,860
Commercial real estate: other construction and land development | Class of financing receivable
Recorded investment:
Total impaired loans with related allowance	6,714	6,818
Total impaired loans with no related allowance	4,162	7,158
Unpaid principal balance:
Total impaired loans with an allowance recorded	6,949	6,825
Total impaired loans with no related allowance recorded	4,270	7,187
Related Allowance	1,890	852
Average recorded investment:
Total impaired loans with an allowance recorded	7,183	6,058
Total impaired loans with no related allowance recorded	4,882	18,164
Interest Recognized
Total impaired loans with no related allowance recorded	74	74
Commercial real estate: farmland and commercial
Interest Recognized
Loans accounted for as troubled debt restructuring	2,861	2,863
Total troubled debt restructuring	2,861	2,863
Commercial real estate: farmland and commercial | Class of financing receivable
Recorded investment:
Total impaired loans with related allowance	5,107	7,259
Total impaired loans with no related allowance	9,059	8,779
Unpaid principal balance:
Total impaired loans with an allowance recorded	5,257	10,697
Total impaired loans with no related allowance recorded	10,562	9,949
Related Allowance	1,219	2,916
Average recorded investment:
Total impaired loans with an allowance recorded	6,790	7,167
Total impaired loans with no related allowance recorded	8,664	7,313
Interest Recognized
Total impaired loans with an allowance recorded	92	92
Commercial real estate: multifamily | Class of financing receivable
Recorded investment:
Total impaired loans with no related allowance	835	295
Unpaid principal balance:
Total impaired loans with no related allowance recorded	835	295
Average recorded investment:
Total impaired loans with no related allowance recorded	363	322
Residential: first lien
Interest Recognized
Loans accounted for as troubled debt restructuring	5,313	4,887
Total troubled debt restructuring	5,313	4,887
Residential: first lien | Class of financing receivable
Recorded investment:
Total impaired loans with no related allowance	5,840	6,153
Unpaid principal balance:
Total impaired loans with no related allowance recorded	6,034	6,258
Average recorded investment:
Total impaired loans with no related allowance recorded	6,293	4,860
Interest Recognized
Total impaired loans with no related allowance recorded	273	179
Residential: junior lien
Interest Recognized
Loans accounted for as troubled debt restructuring	1,371	1,631
Total troubled debt restructuring	1,371	1,631
Residential: junior lien | Class of financing receivable
Recorded investment:
Total impaired loans with no related allowance	2,895	3,206
Unpaid principal balance:
Total impaired loans with no related allowance recorded	2,915	3,226
Average recorded investment:
Total impaired loans with no related allowance recorded	3,035	2,347
Interest Recognized
Total impaired loans with no related allowance recorded	90	99
Consumer Loan
Interest Recognized
Loans accounted for as troubled debt restructuring	1,354	1,531
Total troubled debt restructuring	1,354	1,531
Consumer Loan | Class of financing receivable
Recorded investment:
Total impaired loans with no related allowance	1,384	1,606
Unpaid principal balance:
Total impaired loans with no related allowance recorded	1,386	1,612
Average recorded investment:
Total impaired loans with no related allowance recorded	1,402	1,380
Interest Recognized
Total impaired loans with no related allowance recorded	3	1
Foreign
Interest Recognized
Loans accounted for as troubled debt restructuring		436
Total troubled debt restructuring		436
Foreign | Class of financing receivable
Recorded investment:
Total impaired loans with no related allowance		436
Unpaid principal balance:
Total impaired loans with no related allowance recorded		436
Average recorded investment:
Total impaired loans with no related allowance recorded		452
Interest Recognized
Total impaired loans with no related allowance recorded		$19

Allowance_for_Probable_Loan_Lo6

Allowance for Probable Loan Losses (Details 5) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing receivable recorded investment
Past due 30-59 days	$17,261,000	$19,891,000
Past due 60-89 days	12,215,000	5,330,000
Past due 90 days or greater	67,770,000	60,537,000
Past due 90 days or greater and still accruing	9,988,000	7,197,000	15,033,000
Past due, total	97,246,000	85,758,000
Loans, current	5,581,999,000	5,113,477,000
Total loans	5,679,245,000	5,199,235,000
Commercial
Financing receivable recorded investment
Past due 30-59 days	4,103,000	4,240,000
Past due 60-89 days	2,665,000	538,000
Past due 90 days or greater	40,665,000	36,066,000
Past due 90 days or greater and still accruing	2,890,000	2,051,000
Past due, total	47,433,000	40,844,000
Loans, current	1,042,053,000	1,001,798,000
Total loans	1,089,486,000	1,042,642,000
Commercial real estate: other construction and land development
Financing receivable recorded investment
Past due 30-59 days	596,000	1,042,000
Past due 60-89 days	10,000
Past due 90 days or greater	8,707,000	9,942,000
Past due 90 days or greater and still accruing	439,000	62,000
Past due, total	9,313,000	10,984,000
Loans, current	1,405,664,000	1,197,524,000
Total loans	1,414,977,000	1,208,508,000
Commercial real estate: farmland and commercial
Financing receivable recorded investment
Past due 30-59 days	2,905,000	6,216,000
Past due 60-89 days	7,131,000	520,000
Past due 90 days or greater	10,724,000	6,990,000
Past due 90 days or greater and still accruing	1,711,000	417,000
Past due, total	20,760,000	13,726,000
Loans, current	1,880,639,000	1,736,313,000
Total loans	1,901,399,000	1,750,039,000
Commercial real estate: multifamily
Financing receivable recorded investment
Past due 30-59 days	351,000	39,000
Past due 60-89 days		142,000
Past due 90 days or greater	856,000	295,000
Past due 90 days or greater and still accruing	21,000
Past due, total	1,207,000	476,000
Loans, current	115,492,000	101,622,000
Total loans	116,699,000	102,098,000
Residential: first lien
Financing receivable recorded investment
Past due 30-59 days	5,895,000	4,758,000
Past due 60-89 days	1,864,000	3,046,000
Past due 90 days or greater	4,267,000	4,541,000
Past due 90 days or greater and still accruing	3,901,000	3,518,000
Past due, total	12,026,000	12,345,000
Loans, current	410,000,000	426,117,000
Total loans	422,026,000	438,462,000
Residential: junior lien
Financing receivable recorded investment
Past due 30-59 days	899,000	606,000
Past due 60-89 days	231,000	198,000
Past due 90 days or greater	1,931,000	1,900,000
Past due 90 days or greater and still accruing	431,000	368,000
Past due, total	3,061,000	2,704,000
Loans, current	485,239,000	406,526,000
Total loans	488,300,000	409,230,000
Consumer Loan
Financing receivable recorded investment
Past due 30-59 days	896,000	1,523,000
Past due 60-89 days	216,000	469,000
Past due 90 days or greater	507,000	803,000
Past due 90 days or greater and still accruing	482,000	781,000
Past due, total	1,619,000	2,795,000
Loans, current	59,518,000	63,619,000
Total loans	61,137,000	66,414,000
Foreign
Financing receivable recorded investment
Past due 30-59 days	1,616,000	1,467,000
Past due 60-89 days	98,000	417,000
Past due 90 days or greater	113,000
Past due 90 days or greater and still accruing	113,000
Past due, total	1,827,000	1,884,000
Loans, current	183,394,000	179,958,000
Total loans	$185,221,000	$181,842,000

Allowance_for_Probable_Loan_Lo7

Allowance for Probable Loan Losses (Details 6) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Loan portfolio by credit quality indicator
Portfolio, total	$5,679,245	$5,199,235
Pass
Loan portfolio by credit quality indicator
Portfolio, total	5,328,410	4,942,387
Special Review
Loan portfolio by credit quality indicator
Portfolio, total	54,561	73,077
Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	37,674	35,619
Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	182,429	72,259
Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	76,171	75,893
Commercial
Loan portfolio by credit quality indicator
Portfolio, total	1,089,486	1,042,642
Commercial | Pass
Loan portfolio by credit quality indicator
Portfolio, total	961,490	955,522
Commercial | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	38,382	2,270
Commercial | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	3,793	4,389
Commercial | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	45,646	46,278
Commercial | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	40,175	34,183
Commercial real estate: other construction and land development
Loan portfolio by credit quality indicator
Portfolio, total	1,414,977	1,208,508
Commercial real estate: other construction and land development | Pass
Loan portfolio by credit quality indicator
Portfolio, total	1,353,971	1,167,295
Commercial real estate: other construction and land development | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	1,005	14,247
Commercial real estate: other construction and land development | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	10,428	9,318
Commercial real estate: other construction and land development | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	38,697	3,672
Commercial real estate: other construction and land development | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	10,876	13,976
Commercial real estate: farmland and commercial
Loan portfolio by credit quality indicator
Portfolio, total	1,901,399	1,750,039
Commercial real estate: farmland and commercial | Pass
Loan portfolio by credit quality indicator
Portfolio, total	1,754,741	1,635,179
Commercial real estate: farmland and commercial | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	11,674	56,438
Commercial real estate: farmland and commercial | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	23,453	21,912
Commercial real estate: farmland and commercial | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	97,365	20,472
Commercial real estate: farmland and commercial | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	14,166	16,038
Commercial real estate: multifamily
Loan portfolio by credit quality indicator
Portfolio, total	116,699	102,098
Commercial real estate: multifamily | Pass
Loan portfolio by credit quality indicator
Portfolio, total	115,729	100,948
Commercial real estate: multifamily | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	135	855
Commercial real estate: multifamily | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	835	295
Residential: first lien
Loan portfolio by credit quality indicator
Portfolio, total	422,026	438,462
Residential: first lien | Pass
Loan portfolio by credit quality indicator
Portfolio, total	412,668	432,067
Residential: first lien | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	3,500	122
Residential: first lien | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	18	120
Residential: first lien | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	5,840	6,153
Residential: junior lien
Loan portfolio by credit quality indicator
Portfolio, total	488,300	409,230
Residential: junior lien | Pass
Loan portfolio by credit quality indicator
Portfolio, total	484,968	405,731
Residential: junior lien | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	437	293
Residential: junior lien | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	2,895	3,206
Consumer Loan
Loan portfolio by credit quality indicator
Portfolio, total	61,137	66,414
Consumer Loan | Pass
Loan portfolio by credit quality indicator
Portfolio, total	59,622	64,808
Consumer Loan | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	131
Consumer Loan | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	1,384	1,606
Foreign
Loan portfolio by credit quality indicator
Portfolio, total	185,221	181,842
Foreign | Pass
Loan portfolio by credit quality indicator
Portfolio, total	185,221	180,837
Foreign | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total		569
Foreign | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total		$436

Bank_Premises_and_Equipment_De

Bank Premises and Equipment (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Bank premises and equipment
Less: accumulated depreciation	-378,682	($355,792)
Bank premises and equipment, net	526,423	504,842
Bank buildings and improvements
Bank premises and equipment
Bank premises and equipment, gross	509,830	470,386
Bank buildings and improvements | Minimum
Bank premises and equipment
Estimated useful lives	5 years
Bank buildings and improvements | Maximum
Bank premises and equipment
Estimated useful lives	40 years
Furniture, equipment and vehicles
Bank premises and equipment
Bank premises and equipment, gross	269,861	260,932
Furniture, equipment and vehicles | Minimum
Bank premises and equipment
Estimated useful lives	1 year
Furniture, equipment and vehicles | Maximum
Bank premises and equipment
Estimated useful lives	20 years
Land
Bank premises and equipment
Bank premises and equipment, gross	125,414	128,805
Land, building, furniture, fixture and equipment
Bank premises and equipment
Bank premises and equipment, gross		$511
Land, building, furniture, fixture and equipment | Minimum
Bank premises and equipment
Estimated useful lives	7 years
Land, building, furniture, fixture and equipment | Maximum
Bank premises and equipment
Estimated useful lives	27 years

Goodwill_and_Other_Intangible_2

Goodwill and Other Intangible Assets (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Identified intangible assets
Carrying Amount	$60,697	$60,697
Accumulated Amortization	59,900	57,511
Total identified intangibles, Net	797	3,186
Amortization expense	2,389	4,633	4,651
Estimated amortization expense for each of the five succeeding fiscal years and thereafter
2015	452
2016	295
2017	25
2018	25
Total	797
Changes in carrying amount of goodwill	0	0
Core deposit premium
Identified intangible assets
Carrying Amount	58,675	58,675
Accumulated Amortization	58,379	56,298
Total identified intangibles, Net	296	2,377
Identified intangible (contract rights)
Identified intangible assets
Carrying Amount	2,022	2,022
Accumulated Amortization	1,521	1,213
Total identified intangibles, Net	$501	$809

Deposits_Details

Deposits (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Demand non-interest bearing
Domestic	$2,382,935	$2,175,694
Foreign	547,318	490,816
Total demand non-interest bearing	2,930,253	2,666,510
Savings and interest bearing demand
Domestic	2,488,458	2,364,905
Foreign	537,222	560,707
Total savings and interest bearing demand	3,025,680	2,925,612
$100,000 or more
Domestic	835,792	856,700
Foreign	864,346	938,940
Less than $100,000
Domestic	482,089	531,503
Foreign	300,465	324,160
Total time, certificates of deposit	2,482,692	2,651,303
Total deposits	8,438,625	8,243,425
Savings and interest bearing demand
Domestic	2,998	3,182	4,487
Foreign	599	580	801
Total savings and interest bearing demand	3,597	3,762	5,288
$100,000 or more
Domestic	4,615	5,761	8,263
Foreign	4,529	5,590	9,148
Less than $100,000
Domestic	2,074	3,065	4,945
Foreign	815	1,028	1,617
Total time, certificates of deposit	12,033	15,444	23,973
Total interest expense on deposits	$15,630	$19,206	$29,261

Deposits_Details_2

Deposits (Details 2) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Scheduled maturities of time deposits
2015	$2,177,266,000
2016	203,928,000
2017	76,206,000
2018	23,481,000
2019	1,751,000
Thereafter	60,000
Total time, certificates of deposit	2,482,692,000	2,651,303,000
Time Deposits 250,000 or exceed	1,027,000	1,076,000
Scheduled maturities of time deposits in amounts of $100,000 or more
Due within 3 months or less	631,083,000
Due after 3 months and within 6 months	409,400,000
Due after 6 months and within 12 months	443,860,000
Due after 12 months	215,795,000
Total	$1,700,138,000

Securities_Sold_Under_Repurcha2

Securities Sold Under Repurchase Agreements (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Securities Sold Under Repurchase Agreements
Average outstanding amount	$893,830,000	$1,041,186,000
Maximum amount outstanding at any month end	892,341,000	1,119,531,000
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold	1,127,170,000	1,313,637,000
Collateralized securities, Fair Value of Securities Sold	1,134,418,000	1,317,998,000
Repurchase Borrowing, Balance of Liability	858,350,000	957,381,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	2.79%	2.91%
Overnight agreements
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold	366,731,000	332,042,000
Collateralized securities, Fair Value of Securities Sold	370,704,000	341,238,000
Repurchase Borrowing, Balance of Liability	236,077,000	209,899,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	0.16%	0.17%
1 to 29 days
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold	3,717,000	27,954,000
Collateralized securities, Fair Value of Securities Sold	3,781,000	28,288,000
Repurchase Borrowing, Balance of Liability	1,016,000	18,666,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	0.45%	0.40%
30 to 90 days
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold	13,399,000	8,106,000
Collateralized securities, Fair Value of Securities Sold	13,628,000	8,263,000
Repurchase Borrowing, Balance of Liability	6,705,000	3,295,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	0.38%	0.43%
Over 90 days
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold	743,323,000	945,535,000
Collateralized securities, Fair Value of Securities Sold	746,305,000	940,209,000
Repurchase Borrowing, Balance of Liability	$614,552,000	$725,521,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	3.83%	3.78%

Other_Borrowed_Funds_Details

Other Borrowed Funds (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Federal Home Loan Bank advances
Balance at year end	$1,073,944,000	$1,223,950,000
Federal Home Loan Bank advances short-term
Federal Home Loan Bank advances
Balance at year end	1,067,700,000	1,215,000,000
Rate on balance outstanding at year end (as a percent)	0.15%	0.17%
Average daily balance	1,077,973,000	833,868,000
Average rate (as a percent)	0.16%	0.16%
Maximum amount outstanding at any month end	1,352,500,000	1,280,500,000
Federal Home Loan Bank advances long-term
Federal Home Loan Bank advances
Balance at year end	6,244,000	8,950,000
Rate on balance outstanding at year end (as a percent)	3.51%	3.53%
Average daily balance	7,338,000	7,289,000
Average rate (as a percent)	3.51%	3.53%
Maximum amount outstanding at any month end	8,934,000	8,993,000
Amortization of long-term advances for the next five years	$160,000
Period of amortization of long-term advances	5 years

Junior_Subordinated_Deferrable2

Junior Subordinated Deferrable Interest Debentures (Details) (USD $)	12 Months Ended	0 Months Ended
	Dec. 31, 2014	Feb. 11, 2014	Dec. 31, 2013
	item
Junior subordinated deferrable interest debentures, major types of business trusts
Number of statutory business trusts issuing trust preferred securities	7
Junior subordinated deferrable interest debentures	$175,416,000		$190,726,000
Maximum number of consecutive quarterly period available for deferral of interest payment on Trusts VI, VII, VIII, IX, X, XI and XII	20
Percentage of capital securities issued by trust qualifying as Tier I capital, maximum	25.00%
Percentage of capital securities issued by trust qualifying as Tier II capital, minimum	25.00%
Capital securities issued by the trust, qualifying as Tier I capital	175,416,000		190,726,000
Trust VII
Junior subordinated deferrable interest debentures, major types of business trusts
Redemption price discount (as a percent)		6.00%
Retirement of capital securities		10,310,000
Trust XI
Junior subordinated deferrable interest debentures, major types of business trusts
Redemption price discount (as a percent)	23.60%
Retirement of capital securities	5,000,000
Junior subordinated deferrable interest debentures	$27,990,000

Junior_Subordinated_Deferrable3

Junior Subordinated Deferrable Interest Debentures (Details 2) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Junior subordinated deferrable interest debentures, major types of business trusts
Junior subordinated deferrable interest debentures	$175,416	$190,726
Trust VI
Junior subordinated deferrable interest debentures, major types of business trusts
Junior subordinated deferrable interest debentures	25,774
Interest rate (as a percent)	3.68%
Interest rate index	LIBOR
Spread on interest rate index (as a percent)	3.45%
Trust VIII
Junior subordinated deferrable interest debentures, major types of business trusts
Junior subordinated deferrable interest debentures	25,774
Interest rate (as a percent)	3.28%
Interest rate index	LIBOR
Spread on interest rate index (as a percent)	3.05%
Trust IX
Junior subordinated deferrable interest debentures, major types of business trusts
Junior subordinated deferrable interest debentures	41,238
Interest rate (as a percent)	1.86%
Interest rate index	LIBOR
Spread on interest rate index (as a percent)	1.62%
Trust X
Junior subordinated deferrable interest debentures, major types of business trusts
Junior subordinated deferrable interest debentures	34,021
Interest rate (as a percent)	1.88%
Interest rate index	LIBOR
Spread on interest rate index (as a percent)	1.65%
Trust XI
Junior subordinated deferrable interest debentures, major types of business trusts
Junior subordinated deferrable interest debentures	27,990
Interest rate (as a percent)	1.86%
Interest rate index	LIBOR
Spread on interest rate index (as a percent)	1.62%
Trust XII
Junior subordinated deferrable interest debentures, major types of business trusts
Junior subordinated deferrable interest debentures	$20,619
Interest rate (as a percent)	1.69%
Interest rate index	LIBOR
Spread on interest rate index (as a percent)	1.45%

Earnings_per_Share_EPS_Details

Earnings per Share ("EPS") (Details) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Basic EPS
Net Income (Numerator)	$153,151	$126,351	$93,473
Shares (Denominator)	66,872,500	67,195,180	67,236,681
Per Share Amount	$2.29	$1.88	$1.39
Diluted EPS
Net Income (Numerator)	$153,151	$126,351	$93,473
Potential dilutive common shares and warrants	183,956	119,679	77,282
Shares (Denominator)	67,056,456	67,314,859	67,313,963
Per Share Amount (in dollars per share)	$2.28	$1.88	$1.39

Employees_Profit_Sharing_Plan_

Employees' Profit Sharing Plan (Details) (Deferred profit sharing plan, USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Deferred profit sharing plan
Employees' profit sharing plan
Minimum period of continuous employment to be fully vested	1 year
Profit sharing costs	$3,510,000	$3,500,000	$3,400,000

International_Operations_Detai

International Operations (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loans:
Accrued interest receivable	$31,461,000	$30,654,000
International banking services
Loans:
Commercial	150,078,000	142,145,000
Others	35,143,000	39,697,000
Total loans	185,221,000	181,842,000
Less allowance for probable loan losses	-1,060,000	-1,133,000
Net loans	184,161,000	180,709,000
Accrued interest receivable	702,000	617,000
Outstanding standby and commercial letters of credit	114,672,000
Revenues	$6,034,000	$6,085,000	$7,714,000

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current
U.S.	$72,561	$59,583	$40,375
State	5,252	-1,530	2,234
Foreign	1	3	33
Total current taxes	77,814	58,056	42,642
Deferred
U.S.	-969	-1,692	7,928
State	-58	-125	-5
Total deferred taxes	-1,027	-1,817	7,923
Total income taxes	$76,787	$56,239	$50,565

Income_Taxes_Details_2

Income Taxes (Details 2) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes
Income tax expense differences from the amount computed by applying the U.S. Federal income tax rate to income before income taxes (as a percent)	35.00%	35.00%	35.00%
Reasons for the difference of income tax expense
Computed expected tax expense	$80,560	$64,183	$55,634
Change in taxes resulting from:
Tax-exempt interest income	-4,554	-4,828	-4,381
State tax, net of federal income taxes and tax credit	3,377	-110	1,446
Tax refunds		-966
Other investment income	-3,615	-2,656	-2,691
Other	1,019	616	557
Total income taxes	$76,787	$56,239	$50,565

Income_Taxes_Details_3

Income Taxes (Details 3) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred tax assets:
Loans receivable, principally due to the allowance for probable loan losses	$24,849	$25,365
Other real estate owned	3,453	3,878
Impairment charges on available-for-sale securities	5,618	5,327
Accrued expenses	268	399
Net unrealized gains on available for sale investment securities		24,235
Other	5,809	4,816
Total deferred tax assets	39,997	64,020
Deferred tax liabilities:
Bank premises and equipment, principally due to differences on depreciation	-18,314	-20,729
Net unrealized gains on available for sale investment securities	-6,182
Identified intangible assets and goodwill	-18,787	-18,051
Other	-12,303	-11,476
Total deferred tax liabilities	-55,586	-50,256
Net deferred tax asset (liability)	($15,589)	$13,764

Stock_Options_Details

Stock Options (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 05, 2012
Stock options under 2012 Plan
Stock option details
Shares available for future grants		204,750		800,000
Maximum exercisable period for options granted	10 years
Black-Scholes-Merton option valuation model assumptions
Expected Life	7 years 7 months 17 days	7 years 7 months 17 days
Dividend yield (as a percent)	2.01%	2.33%
Interest rate (as a percent)	2.28%	2.86%
Volatility (as a percent)	47.36%	47.28%
Stock option activity
Options outstanding at the beginning of the period (in shares)	515,143
Plus: Options granted (in shares)	564,750
Less:
Options exercised (in shares)	40,385
Options expired (in shares)	15,125
Options forfeited (in shares)	30,494
Options outstanding at the end of the period (in shares)	993,889	515,143
Options fully vested and exercisable at the end of the period (in shares)	250,487
Stock options, weighted average exercise price
Options outstanding at the beginning, weighted average exercise price (in dollars per share)	$15.98
Plus: Options granted, weighted average exercise price (in dollars per share)	$21.48
Less:
Options exercised, weighted average exercise price (in dollars per share)	$13.75
Options expired, weighted average exercise price (in dollars per share)	$27.02
Options forfeited, weighted average exercise price (in dollars per share)	$18.84
Options outstanding at the end, weighted average exercise price (in dollars per share)	$18.94	$15.98
Options fully vested and exercisable at the end, weighted average exercise price (in dollars per share)	$16.76
Stock options, weighted average remaining contractual term
Options outstanding at the end, weighted average remaining contractual term	6 years 7 months 13 days
Options fully vested and exercisable at the end, weighted average remaining contractual term	2 years 3 months 11 days
Stock options, aggregate intrinsic value
Options outstanding at the end, aggregate intrinsic value	$7,567,000
Options fully vested and exercisable at the end, aggregate intrinsic value	2,461,000
Stock-based compensation expense	1,058,000	414,000	474,000
Stock-based compensation cost, unrecognized, related to non-vested options	3,934,000
Stock-based compensation cost, unrecognized, related to non-vested options, weighted-average period of recognition	2 years 3 months 18 days
Other information pertaining to option activity
Weighted average grant date fair value of stock options granted (in dollars per share)	$9.07	$9.05	$8.71
Total fair value of stock options vested	376,000	480,000	524,000
Total intrinsic value of stock options exercised	$468,000	$171,000	$41,000
Incentive stock options granted to 10% shareholders
Stock option details
Maximum exercisable period for options granted	5 years

Long_Term_Restricted_Stock_Uni1

Long Term Restricted Stock Units (Details) (2009 International Bancshares Corporation Long-Term Restricted Stock Unit Plan, USD $)	12 Months Ended						1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2009
							item
CPP-compliant long-term RSUs
Long-Term Restricted Stock Units
Restricted stock compensation limit as a percentage to the total annual compensation of the President	33.00%
CPP-compliant long-term RSUs granted for performance in 2012
Long-Term Restricted Stock Units
Compensation cost		$425,000
CPP-compliant long-term RSUs granted for performance in 2011
Long-Term Restricted Stock Units
Compensation cost				400,000
Cash amounts paid on vesting of awards			572,746
CPP-compliant long-term RSUs granted for performance in 2010
Long-Term Restricted Stock Units
Compensation cost					400,000
Cash amounts paid on vesting of awards		358,782
CPP-compliant long-term RSUs granted for performance in 2009
Long-Term Restricted Stock Units
Compensation cost						250,000
Cash amounts paid on vesting of awards	591,344	$262,842
Restricted Stock Units (RSUs)
Long-Term Restricted Stock Units
Minimum number of non-employee members of the Board needed to authorize restricted stock units							2

Commitments_Contingent_Liabili2

Commitments, Contingent Liabilities and Other Matters (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Commitments, Contingent Liabilities and Other Matters
Total rental expense	$7,200,000	$7,300,000	$8,300,000
Future minimum lease payments due under non-cancellable operating leases
2014	3,505,000
2015	2,454,000
2016	1,168,000
2017	631,000
2018	157,000
Thereafter	122,000
Total	8,037,000
Minimum period for non-cancellable sub-leases	1 year
Aggregate future minimum rentals to be received under non-cancellable sub-leases	85,875,000
Approximate cash maintained to satisfy regulatory reserve requirements	$106,841,000	$96,087,000

Transactions_with_Related_Part1

Transactions with Related Parties (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Transactions with Related Parties
Aggregate amount receivable from related parties	$26,382,000	$51,554,000

Financial_Instruments_with_Off2

Financial Instruments with Off-Statement of Condition Risk and Concentrations of Credit Risk (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Maximum
Financial amounts of instruments, whose contract amounts represent credit risks
Credit risk commitment, maximum expiration date	1 year
Commitments to extend credit
Financial amounts of instruments, whose contract amounts represent credit risks
Outstanding amount of financial instruments whose, contract amounts represent credit risks	1,662,516,000
Credit card lines
Financial amounts of instruments, whose contract amounts represent credit risks
Outstanding amount of financial instruments whose, contract amounts represent credit risks	16,687,000
Standby letters of credit
Financial amounts of instruments, whose contract amounts represent credit risks
Outstanding amount of financial instruments whose, contract amounts represent credit risks	103,793,000
Commercial letters of credit
Financial amounts of instruments, whose contract amounts represent credit risks
Outstanding amount of financial instruments whose, contract amounts represent credit risks	10,879,000
Unsecured letters of credit
Financial amounts of instruments, whose contract amounts represent credit risks
Guarantee obligations, maximum exposure	103,793,000
Unsecured letters of credit	40,875,000	$42,503,000

Capital_Requirements_Details

Capital Requirements (Details) (USD $)	0 Months Ended	12 Months Ended		48 Months Ended	0 Months Ended
	Nov. 28, 2012	Dec. 31, 2014	Dec. 31, 2012	Nov. 28, 2012	Feb. 20, 2015
Series A cumulative perpetual preferred shares, aggregate liquidation value		$216,000,000
Series A cumulative perpetual preferred shares, issued		216,000
Series A cumulative perpetual preferred shares, par value (in dollars per share)		$0.01
Series A cumulative perpetual preferred shares, per share liquidation value (in dollars per share)		$1,000
Warrants to purchase entity's common stock (in shares)		1,326,238
Warrants, exercise price (in dollars per share)		$24.43
Warrants, term		10 years
Senior preferred stock, dividend rate for first five years (as a percent)		5.00%
Senior preferred stock, dividend rate thereafter (as a percent)		9.00%
Senior Preferred Stock held by Treasury repurchased (in shares)	216,000
Redemption of senior preferred shares			216,000,000
Preferred stock dividends to the U.S. Treasury			10,260,000	41,520,139
Dividend payable by subsidiaries, maximum		$702,750,000
Subsequent Event
Warrants, exercise price (in dollars per share)					$24.43
Cash dividends (as a percent)					33.00%

Capital_Requirements_Details_2

Capital Requirements (Details 2) (USD $)	0 Months Ended
In Thousands, unless otherwise specified	Jan. 01, 2015	Dec. 31, 2014	Dec. 31, 2013
Capital Requirements
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)		4.00%
Forecast
Capital Requirements
Total Capital (to Risk Weighted Assets), Actual Amount	$500,000
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	4.50%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	2.50%
Term of mandatory compliance	4 years
Parent Company
Capital Requirements
Total Capital (to Risk Weighted Assets), Actual Amount		1,524,998	1,442,837
Tier 1 Capital (to Risk Weighted Assets), Actual Amount		1,457,068	1,369,657
Tier 1 Capital (to Average Assets), Actual Amount		1,457,068	1,369,657
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)		20.24%	20.36%
Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent)		19.34%	19.33%
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent)		12.33%	11.61%
Parent Company | Minimum
Capital Requirements
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount		602,847	566,870
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount		301,424	283,435
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount		472,864	472,044
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)		8.00%	8.00%
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)		4.00%	4.00%
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent)		4.00%	4.00%
International Bank of Commerce, Laredo
Capital Requirements
Total Capital (to Risk Weighted Assets), Actual Amount		1,131,528	1,035,189
Tier 1 Capital (to Risk Weighted Assets), Actual Amount		1,071,360	969,731
Tier 1 Capital (to Average Assets), Actual Amount		1,071,360	969,731
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)		17.31%	16.96%
Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent)		16.39%	15.89%
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent)		11.22%	10.09%
International Bank of Commerce, Laredo | Minimum
Capital Requirements
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount		523,006	488,303
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		653,757	610,378
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount		261,503	244,151
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		392,254	366,227
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount		381,804	384,497
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		477,255	480,622
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)		8.00%	8.00%
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)		10.00%	10.00%
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)		4.00%	4.00%
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)		6.00%	6.00%
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent)		4.00%	4.00%
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)		5.00%	5.00%
International Bank of Commerce, Brownsville
Capital Requirements
Total Capital (to Risk Weighted Assets), Actual Amount		151,489	143,879
Tier 1 Capital (to Risk Weighted Assets), Actual Amount		145,584	138,467
Tier 1 Capital (to Average Assets), Actual Amount		145,584	138,467
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)		28.60%	27.63%
Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent)		27.48%	26.60%
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent)		13.96%	13.33%
International Bank of Commerce, Brownsville | Minimum
Capital Requirements
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount		42,381	41,652
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		52,976	52,065
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount		21,190	20,826
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		31,785	31,239
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount		41,717	41,553
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		52,146	51,942
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)		8.00%	8.00%
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)		10.00%	10.00%
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)		4.00%	4.00%
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)		6.00%	6.00%
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent)		4.00%	4.00%
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)		5.00%	5.00%
International Bank of Commerce, Zapata
Capital Requirements
Total Capital (to Risk Weighted Assets), Actual Amount		60,946	57,675
Tier 1 Capital (to Risk Weighted Assets), Actual Amount		60,035	56,459
Tier 1 Capital (to Average Assets), Actual Amount		60,035	56,459
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)		33.83%	32.65%
Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent)		33.33%	31.96%
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent)		10.88%	10.64%
International Bank of Commerce, Zapata | Minimum
Capital Requirements
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount		14,412	14,130
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		18,041	17,663
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount		7,206	7,065
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		10,809	10,598
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount		22,081	21,219
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		27,602	26,523
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)		8.00%	8.00%
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)		10.00%	10.00%
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)		4.00%	4.00%
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)		6.00%	6.00%
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent)		4.00%	4.00%
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)		5.00%	5.00%
Commerce Bank
Capital Requirements
Total Capital (to Risk Weighted Assets), Actual Amount		68,291	64,585
Tier 1 Capital (to Risk Weighted Assets), Actual Amount		67,347	63,491
Tier 1 Capital (to Average Assets), Actual Amount		67,347	63,491
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)		37.42%	36.45%
Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent)		36.90%	35.83%
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent)		12.04%	11.88%
Commerce Bank | Minimum
Capital Requirements
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount		14,600	14,175
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		18,251	17,719
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount		7,300	7,087
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		10,950	10,631
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount		22,373	21,372
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount		27,966	$26,715
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)		8.00%	8.00%
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)		10.00%	10.00%
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)		4.00%	4.00%
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)		6.00%	6.00%
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent)		4.00%	4.00%
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)		5.00%	5.00%

Fair_Value_Details

Fair Value (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Assets:
Available for sale securities	$4,931,963	$5,304,579
Measured on a recurring basis: | Assets/Liabilities Measured at Fair Value
Assets:
Available for sale securities	4,931,963	5,304,579
Measured on a recurring basis: | Assets/Liabilities Measured at Fair Value | Residential mortgage-backed securities
Assets:
Available for sale securities	4,600,372	5,027,701
Measured on a recurring basis: | Assets/Liabilities Measured at Fair Value | States and political subdivisions
Assets:
Available for sale securities	282,276	248,410
Measured on a recurring basis: | Assets/Liabilities Measured at Fair Value | Other
Assets:
Available for sale securities	49,315	28,468
Measured on a recurring basis: | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Available for sale securities	29,315	28,468
Measured on a recurring basis: | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other
Assets:
Available for sale securities	29,315	28,468
Measured on a recurring basis: | Significant Other Observable Inputs (Level 2)
Assets:
Available for sale securities	4,878,585	5,248,259
Measured on a recurring basis: | Significant Other Observable Inputs (Level 2) | Residential mortgage-backed securities
Assets:
Available for sale securities	4,576,309	4,999,849
Measured on a recurring basis: | Significant Other Observable Inputs (Level 2) | States and political subdivisions
Assets:
Available for sale securities	282,276	248,410
Measured on a recurring basis: | Significant Other Observable Inputs (Level 2) | Other
Assets:
Available for sale securities	20,000
Measured on a recurring basis: | Significant Unobservable Inputs (Level 3)
Assets:
Available for sale securities	24,063	27,852
Measured on a recurring basis: | Significant Unobservable Inputs (Level 3) | Residential mortgage-backed securities
Assets:
Available for sale securities	$24,063	$27,852

Fair_Value_Details_2

Fair Value (Details 2) (Residential mortgage-backed securities, USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014
Residential mortgage-backed securities
Reconciliation of activity for mortgage-backed securities on a net basis
Balance at the beginning of the period	$27,852
Principal paydowns	-4,154
Total unrealized gains (losses) included in:
Other comprehensive income	1,182
Impairment realized in earnings	-817
Balance at the end of the period	$24,063

Fair_Value_Details_3

Fair Value (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Assets:
Impaired Loans	$65,551,000	$64,585,000
Non-financial assets:
Other real estate owned	69,872,000	85,879,000
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Charges to allowance for probable loan losses in connection with other real estate owned	367,000	402,000
Adjustment to fair value in connection with other real estate owned	597,000	1,204,000
Impaired commercial collateral dependent loans	65,551,000	64,585,000
Impaired commercial collateral dependent receivables appraisals to determine fair value within immediately preceding twelve months	52,092,000	50,346,000
Impaired collateral dependent commercial loans with an internal evaluation completed in the last twelve months	5,307,000	0
Significant Unobservable Inputs (Level 3) | Bond meeting the original contract terms
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Minimum period of residential mortgage loan performance under original contract terms	24 months	24 months
Estimated future principal prepayment rate assumption, low end of range (as a percent)	7.00%	7.00%
Default rate assumptions (as a percent)	1.00%	1.00%
Loss severity rate assumptions, first year (as a percent)	25.00%	25.00%
Estimated future principal prepayment rate assumption, discount rate (as a percent)	13.00%	13.00%
Significant Unobservable Inputs (Level 3) | Bond not meeting the original contract terms
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Estimated future principal prepayment rate assumption, low end of range (as a percent)	2.00%	2.00%
Default rate assumptions (as a percent)	4.50%	4.50%
Loss severity rate assumptions, first year (as a percent)	60.00%	60.00%
Decrease in loss severity rates, following five years (as a percent)	5.00%	5.00%
Loss severity rate, thereafter (as a percent)	25.00%	25.00%
Estimated future principal prepayment rate assumption, discount rate (as a percent)	13.00%	13.00%
Measured on a non-recurring basis:
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Change in net provision, impaired loans	-1,557,000	13,229,000
Change in net provision, other real estate owned	597,000	1,204,000
Measured on a non-recurring basis: | Assets/Liabilities Measured at Fair Value
Assets:
Impaired Loans	29,501,000	28,391,000
Non-financial assets:
Other real estate owned	6,112,000	16,329,000
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Impaired commercial collateral dependent loans	29,501,000	28,391,000
Measured on a non-recurring basis: | Significant Unobservable Inputs (Level 3)
Assets:
Impaired Loans	29,501,000	28,391,000
Non-financial assets:
Other real estate owned	6,112,000	16,329,000
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Impaired commercial collateral dependent loans	$29,501,000	$28,391,000

Fair_Value_Details_4

Fair Value (Details 4) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Deposits
Carrying amount of time deposits	$2,482,692,000	$2,651,303,000
Significant Other Observable Inputs (Level 2)
Other borrowed funds
Carrying amount of the long-term FHLB borrowings	6,244,000	8,950,000
Estimated fair value of long-term FHLB borrowings	6,645,000	8,950,000
Significant Unobservable Inputs (Level 3)
Loans
Carrying amount of fixed rate performing loans	1,352,147,000	1,243,252,000
Estimated fair value of fixed rate performing loans	1,285,648,000	1,196,916,000
Deposits
Carrying amount of time deposits	2,482,692,000	2,651,303,000
Estimated fair value of time deposits	2,480,390,000	2,649,452,000
Securities Sold Under Repurchase Agreements
Carrying amount of long-term repurchase agreements	610,000,000	710,000,000
Estimated fair value of long-term repurchase agreements	$558,097,100	$792,215,500

International_Bancshares_Corpo6

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Condition (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
ASSETS
Other investments	$420,670	$388,563
Other assets	130,711	158,862
Total assets	12,196,520	12,079,477
Liabilities:
Junior subordinated deferrable interest debentures	175,416	190,726
Other liabilities	69,527	39,587
Total liabilities	10,615,862	10,655,069
Shareholders' equity:
Common shares	95,784	95,744
Surplus	165,520	163,947
Retained earnings	1,585,389	1,467,000
Accumulated other comprehensive income (loss)	11,397	-43,774
Total shareholders' equity before treasury stock	1,858,090	1,682,917
Less cost of shares in treasury	-277,432	-258,509
Total shareholders' equity	1,580,658	1,424,408	1,435,708	1,600,165
Total liabilities and shareholders' equity	12,196,520	12,079,477
Parent Company
ASSETS
Cash	9,252	8,106
Other investments	69,042	62,381
Notes receivable	204	313
Investment in subsidiaries	1,691,553	1,556,932
Other assets	50	197
Total assets	1,770,101	1,627,929
Liabilities:
Junior subordinated deferrable interest debentures	175,416	190,726
Due to IBC Trading	21	21
Other liabilities	14,006	12,774
Total liabilities	189,443	203,521
Shareholders' equity:
Common shares	95,784	95,744
Surplus	165,520	163,947
Retained earnings	1,585,389	1,467,000
Accumulated other comprehensive income (loss)	11,397	-43,774
Total shareholders' equity before treasury stock	1,858,090	1,682,917
Less cost of shares in treasury	-277,432	-258,509
Total shareholders' equity	1,580,658	1,424,408
Total liabilities and shareholders' equity	$1,770,101	$1,627,929

International_Bancshares_Corpo7

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Income (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income:
Other interest income	$191	$115	$503
Expenses:
Interest expense (Debentures)	4,264	4,665	6,595
Income before federal income taxes and equity in undistributed net income of subsidiaries	229,938	182,590	158,400
Income tax expense (benefit)	76,787	56,239	50,565
Net income	153,151	126,351	107,835
Preferred stock dividends and discount accretion			14,362
Net income available to common shareholders	153,151	126,351	93,473
Parent Company
Income:
Dividends from subsidiaries	71,389	30,000	229,250
Interest income on notes receivable	15	18	27
Interest income on other investments	6,862	12,301	6,759
Other interest income			18
Other	1,923	26	686
Total income	80,189	42,345	236,740
Expenses:
Interest expense (Debentures)	4,264	4,665	6,595
Other	1,099	1,889	3,867
Total expenses	5,363	6,554	10,462
Income before federal income taxes and equity in undistributed net income of subsidiaries	74,826	35,791	226,278
Income tax expense (benefit)	1,370	2,529	-738
Income before equity in undistributed net income of subsidiaries	73,456	33,262	227,016
Equity in undistributed (distributed) net income of subsidiaries	79,695	93,089	-119,181
Net income	153,151	126,351	107,835
Preferred stock dividends and discount accretion			14,362
Net income available to common shareholders	$153,151	$126,351	$93,473

International_Bancshares_Corpo8

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Cash Flows (Details) (USD $)	12 Months Ended			48 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 28, 2012
Operating activities:
Net income	$153,151,000	$126,351,000	$107,835,000
Adjustments to reconcile net income to net cash provided by operating activities:
Impairment charges on available for sale securities	817,000	1,374,000	1,039,000
Stock compensation expense	1,058,000	414,000	474,000
Increase (decrease) in other liabilities	-7,482,000	-2,274,000	7,106,000
Net cash provided by operating activities	193,037,000	209,126,000	160,013,000
Investing activities:
Principal collected on mortgage-backed securities	787,361,000	1,223,532,000	1,294,197,000
Net cash used in investing activities	-90,399,000	-447,649,000	-261,016,000
Financing activities:
Redemption of preferred shares			-216,000,000
Proceeds from stock transactions	555,000	265,000	51,000
Payments of cash dividends - common	-34,762,000	-28,894,000	-26,894,000
Payments of cash dividends - preferred			-10,260,000	-41,520,139
Purchase of treasury stock	-18,923,000		-1,716,000
Net cash (used in) provided by financing activities	-122,277,000	230,208,000	122,218,000
(Decrease) increase in cash and cash equivalents	-19,639,000	-8,315,000	21,215,000
Cash and cash equivalents at beginning of year	274,785,000	283,100,000	261,885,000
Cash and cash equivalents at end of year	255,146,000	274,785,000	283,100,000
Parent Company
Operating activities:
Net income	153,151,000	126,351,000	107,835,000
Adjustments to reconcile net income to net cash provided by operating activities:
Impairment charges on available for sale securities	254,000	754,000
Stock compensation expense	1,058,000	414,000	474,000
Increase (decrease) in other liabilities	416,000	-969,000	6,711,000
Equity in (undistributed) distributed net income of subsidiaries	-79,695,000	-93,089,000	119,181,000
Net cash provided by operating activities	75,184,000	33,461,000	234,201,000
Investing activities:
Principal collected on mortgage-backed securities	1,301,000	1,207,000	1,985,000
Net decrease in notes receivable	109,000	96,000	86,000
(Increase) decrease in other assets and other investments	-7,008,000	432,000	6,418,000
Net cash used in investing activities	-5,598,000	1,735,000	8,489,000
Financing activities:
Repayment of trust preferred securities	-15,310,000
Redemption of preferred shares			-216,000,000
Proceeds from stock transactions	555,000	265,000	51,000
Payments of cash dividends - common	-34,762,000	-28,894,000	-26,894,000
Payments of cash dividends - preferred			-10,260,000
Purchase of treasury stock	-18,923,000		-1,716,000
Net cash (used in) provided by financing activities	-68,440,000	-28,629,000	-254,819,000
(Decrease) increase in cash and cash equivalents	1,146,000	6,567,000	-12,129,000
Cash and cash equivalents at beginning of year	8,106,000	1,539,000	13,668,000
Cash and cash equivalents at end of year	$9,252,000	$8,106,000	$1,539,000