International Bancshares (IBOC) 10-K 28 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 23, 2018	Jun. 30, 2017
Document and Entity Information
Entity Registrant Name	INTERNATIONAL BANCSHARES CORP
Entity Central Index Key	315,709
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 2,315,388,000
Entity Common Stock, Shares Outstanding		66,097,271
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY

Consolidated Statements of Cond

Consolidated Statements of Condition - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 265,357	$ 269,198
Investment securities:
Held to maturity (Market value of $2,400 on December 31, 2017 and $2,400 on December 31, 2016)	2,400	2,400
Available for sale (Amortized cost of $4,196,263 on December 31, 2017 and $4,218,841 on December 31, 2016)	4,152,070	4,177,349
Total investment securities	4,154,470	4,179,749
Loans	6,348,172	5,964,688
Less allowance for probable loan losses	(67,687)	(64,661)
Net loans	6,280,485	5,900,027
Bank premises and equipment, net	514,454	527,583
Accrued interest receivable	34,456	32,172
Other investments	571,415	517,162
Identified intangible assets, net		25
Goodwill	282,532	282,532
Other assets	81,529	95,593
Total assets	12,184,698	11,804,041
Deposits:
Demand - non-interest bearing	3,243,255	3,158,051
Savings and interest bearing demand	3,245,131	3,203,728
Time	2,056,506	2,248,310
Total deposits	8,544,892	8,610,089
Securities sold under repurchase agreements	353,805	504,985
Other borrowed funds	1,195,225	733,375
Junior subordinated deferrable interest debentures	160,416	160,416
Other liabilities	91,380	70,509
Total liabilities	10,345,718	10,079,374
Shareholders' equity:
Common shares of $1.00 par value. Authorized 275,000,000 shares; issued 96,019,028 shares on December 31, 2017 and 95,910,143 shares on December 31, 2016	96,019	95,910
Surplus	171,816	169,567
Retained earnings	1,891,805	1,777,963
Accumulated other comprehensive loss (including $0 on December 31, 2017 and $(3,287) on December 31, 2016 of comprehensive loss related to other-than-temporary impairment for non-credit related issues)	(28,397)	(26,697)
Total shareholders' equity before treasury stock	2,131,243	2,016,743
Less cost of shares in treasury, 29,939,545 shares on December 31, 2017 and 29,934,675 on December 31, 2016	(292,263)	(292,076)
Total shareholders' equity	1,838,980	1,724,667
Total liabilities and shareholders' equity	$ 12,184,698	$ 11,804,041

Consolidated Statements of Con3

Consolidated Statements of Condition (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Consolidated Statements of Condition
Held to maturity, Market value (in dollars)	$ 2,400	$ 2,400
Available for sale, Amortized cost (in dollars)	$ 4,196,263	$ 4,218,841
Common shares, par value (in dollars per share)	$ 1	$ 1
Common shares, Authorized shares	275,000,000	275,000,000
Common shares, issued shares	96,019,028	95,910,143
Comprehensive loss related to other-than-temporary impairment for non-credit related issues (in dollars)	$ 0	$ (3,287)
Treasury, shares	29,939,545	29,934,675

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income:
Loans, including fees	$ 322,508	$ 297,820	$ 297,283
Investment securities:
Taxable	82,347	79,533	88,008
Tax-exempt	9,656	10,356	11,319
Other interest income	625	205	144
Total interest income	415,136	387,914	396,754
Interest expense:
Savings deposits	6,208	4,562	3,593
Time deposits	9,736	9,963	11,233
Securities sold under repurchase agreements	6,617	20,876	23,777
Other borrowings	10,978	3,128	1,615
Junior subordinated deferrable interest debentures	5,392	4,600	4,099
Total interest expense	38,931	43,129	44,317
Net interest income	376,205	344,785	352,437
Provision for probable loan losses	11,221	19,859	24,405
Net interest income after provision for probable loan losses	364,984	324,926	328,032
Non-interest income:
Service charges on deposit accounts	72,868	73,581	78,825
Other service charges, commissions and fees
Banking	44,964	46,267	44,971
Non-banking	7,345	7,006	7,223
Investment securities transactions, net	(4,774)	(2,626)	(3,682)
Other investments, net	18,918	23,827	16,969
Other income	11,085	13,647	11,428
Total non-interest income	150,406	161,702	155,734
Non-interest expense:
Employee compensation and benefits	132,750	128,661	125,135
Occupancy	28,439	26,583	28,019
Depreciation of bank premises and equipment	25,281	24,738	25,009
Professional fees	13,650	13,672	12,278
Deposit insurance assessments	3,294	5,777	5,938
Net expense, other real estate owned	965	5,688	5,695
Amortization of identified intangible assets	25	128	644
Advertising	7,854	7,814	7,585
Early termination fee - securities sold under repurchase agreements	5,765	7,042	3,510
Software and software maintenance	19,189	15,087	11,225
Impairment charges (Total other-than-temporary impairment charges, $0 net of $0, $793 net of $1,147, and $371 net of $1,325 included in other comprehensive loss)		354	954
Other	56,536	54,081	50,932
Total non-interest expense	293,748	289,625	276,924
Income before income taxes	221,642	197,003	206,842
Provision for income taxes	64,206	63,071	70,116
Net income	$ 157,436	$ 133,932	$ 136,726
Basic earnings per common share:
Weighted average number of shares outstanding (in shares)	66,046,155	65,967,989	66,411,193
Net income (in dollars per share)	$ 2.38	$ 2.03	$ 2.06
Fully diluted earnings per common share:
Weighted average number of shares outstanding (in shares)	66,778,436	66,313,490	66,636,353
Net income (in dollars per share)	$ 2.36	$ 2.02	$ 2.05

Consolidated Statements of Inc5

Consolidated Statements of Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements of Income
Impairment charges, other-than-temporary impairment charges	$ 0	$ 793	$ 371
Impairment charges, other comprehensive income	$ 0	$ 1,147	$ 1,325

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements of Comprehensive Income
Net income	$ 157,436	$ 133,932	$ 136,726
Other comprehensive income, net of tax:
Net unrealized holding losses on securities available for sale arising during period (net of tax effects of $(2,586), $(16,585), and $(6,593))	(4,803)	(30,801)	(12,243)
Reclassification adjustment for losses on securities available for sale included in net income (net of tax effects of $1,671, $919, and $1,289)	3,103	1,707	2,393
Reclassification adjustment for impairment charges on available for sale securities included in net income (net of tax effects of $0, $124, and $334)		230	620
Other comprehensive (loss) income, net of tax	(1,700)	(28,864)	(9,230)
Comprehensive income	$ 155,736	$ 105,068	$ 127,496

Consolidated Statements of Com7

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements of Comprehensive Income
Net unrealized holding (losses) gains on securities available for sale arising during period, tax effects	$ (2,586)	$ (16,585)	$ (6,593)
Reclassification adjustment for (losses) gains on securities available for sale included in net income, tax effects	1,671	919	1,289
Reclassification adjustment for impairment charges on available for sale securities included in net income, tax effects	$ 0	$ 124	$ 334

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Total
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
Increase (decrease) in shareholders' equity
Net Income				136,726			136,726
Dividends:
Cash ($.66, $.60 and $.58 per share) for the year ended December 31, 2017, 2016 and 2015, respectively)				(38,515)			(38,515)
Purchase of treasury stock (4,870, 349,029 and 261,079 shares) for the years ended December 31, 2017, 2016 and 2015, respectively)						(6,678)	(6,678)
Exercise of stock options		82	1,288				1,370
Options exercised (in shares)	82
Stock compensation expense recognized in earnings			1,172				1,172
Other comprehensive income, net of tax:
Net change in unrealized gains and losses on available for sale securities, net of reclassification adjustments					(9,230)		(9,230)
Balance at Dec. 31, 2015		95,866	167,980	1,683,600	2,167	(284,110)	1,665,503
Balance (in shares) at Dec. 31, 2015	95,866
Increase (decrease) in shareholders' equity
Net Income				133,932			133,932
Dividends:
Cash ($.66, $.60 and $.58 per share) for the year ended December 31, 2017, 2016 and 2015, respectively)				(39,569)			(39,569)
Purchase of treasury stock (4,870, 349,029 and 261,079 shares) for the years ended December 31, 2017, 2016 and 2015, respectively)						(7,966)	(7,966)
Exercise of stock options		44	505				549
Options exercised (in shares)	44
Stock compensation expense recognized in earnings			1,082				1,082
Other comprehensive income, net of tax:
Net change in unrealized gains and losses on available for sale securities, net of reclassification adjustments					(28,864)		(28,864)
Balance at Dec. 31, 2016		95,910	169,567	1,777,963	(26,697)	(292,076)	1,724,667
Balance (in shares) at Dec. 31, 2016	95,910
Increase (decrease) in shareholders' equity
Net Income				157,436			157,436
Dividends:
Cash ($.66, $.60 and $.58 per share) for the year ended December 31, 2017, 2016 and 2015, respectively)				(43,594)			(43,594)
Purchase of treasury stock (4,870, 349,029 and 261,079 shares) for the years ended December 31, 2017, 2016 and 2015, respectively)						(187)	(187)
Exercise of stock options		109	1,346				1,455
Options exercised (in shares)	109
Stock compensation expense recognized in earnings			903				903
Other comprehensive income, net of tax:
Net change in unrealized gains and losses on available for sale securities, net of reclassification adjustments					(1,700)		(1,700)
Balance at Dec. 31, 2017		$ 96,019	$ 171,816	$ 1,891,805	$ (28,397)	$ (292,263)	$ 1,838,980
Balance (in shares) at Dec. 31, 2017	96,019

Consolidated Statements of Sha9

Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements of Shareholders' Equity
Cash Dividends (in dollars per share)	$ 0.66	$ 0.60	$ 0.58
Purchase of treasury stock (in shares)	4,870	349,029	261,079

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income	$ 157,436	$ 133,932	$ 136,726
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for probable loan losses	11,221	19,859	24,405
Specific reserve, other real estate owned	710	2,351	1,023
Depreciation of bank premises and equipment	25,281	24,738	25,009
(Gain) loss on sale of bank premises and equipment	(38)	(450)	14
(Gain) loss on sale of other real estate owned	(703)	86	(57)
Accretion of investment securities discounts	(393)	(539)	(1,704)
Amortization of investment securities premiums	24,040	26,873	28,000
Investment securities transactions, net	4,774	2,626	3,682
Impairment charges on available for sale securities		354	954
Amortization of identified intangible assets	25	128	644
Stock based compensation expense	903	1,082	1,172
Earnings from affiliates and other investments	(13,198)	(14,315)	(12,176)
Deferred tax expense (benefit)	4,570	7,306	(332)
Increase in accrued interest receivable	(2,284)	(600)	(111)
(Increase) decrease in other assets	(16,117)	7,494	2,967
Net increase (decrease)in other liabilities	592	(7,705)	(6,567)
Net cash provided by operating activities	196,819	203,220	203,649
Investing activities:
Proceeds from maturities of securities		1,200	1,075
Proceeds from sales and calls of available for sale securities	396,066	352,743	164,163
Purchases of available for sale securities	(1,182,006)	(1,325,657)	(352,513)
Principal collected on mortgage backed securities	780,097	919,594	854,736
Net increase in loans	(394,267)	(38,523)	(297,689)
Purchases of other investments	(26,193)	(49,013)	(16,355)
Distributions from other investments	20,344	23,276	18,293
Purchases of bank premises and equipment	(14,315)	(38,856)	(19,831)
Proceeds from sales of bank premises and equipment	2,201	3,701	4,515
Proceeds from sales of other real estate owned	14,266	13,772	16,831
Net cash (used in) provided by investing activities	(403,807)	(137,763)	373,225
Financing activities:
Net increase in non-interest bearing demand deposits	85,204	8,433	219,365
Net increase (decrease) in savings and interest bearing demand deposits	41,403	183,506	(5,458)
Net decrease in time deposits	(191,804)	(118,103)	(116,279)
Net decrease in securities sold under repurchase agreements	(151,180)	(322,787)	(30,578)
Net increase (decrease) in other borrowed funds	461,850	227,625	(568,194)
Redemption of long-term debt		(1,000)	(14,000)
Purchase of treasury stock	(187)	(7,966)	(6,678)
Proceeds from stock transactions	1,455	549	1,370
Payments of cash dividends - common	(43,594)	(39,569)	(38,515)
Net cash provided by (used in) financing activities	203,147	(69,312)	(558,967)
(Decrease) increase in cash and cash equivalents	(3,841)	(3,855)	17,907
Cash and cash equivalents at beginning of period	269,198	273,053
Cash and cash equivalents at end of period	265,357	269,198	273,053
Supplemental cash flow information:
Interest paid	38,995	44,069	44,560
Income taxes paid	66,983	49,925	65,234
Non-cash investing and financing activities:
Net transfers from loans to other real estate owned	$ 2,588	$ 2,563	$ 3,775

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
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 U.S. generally accepted accounting principles (“GAAP”) 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”), International Bank of Commerce, Oklahoma City, 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 (which was terminated in September 2016), 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 the Oklahoma 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 one insurance‑related subsidiary, IBC Insurance Agency, Inc., a wholly owned subsidiary of IBC, the bank subsidiary. The insurance‑related subsidiary does not conduct underwriting activities. 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 (loss) until realized. The Company did not maintain any trading securities during the three year period ended December 31, 2017. Mortgage‑backed securities held at December 31, 2017 and 2016 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 (i) the length of time and the extent to which the fair value has been less than cost, (ii) the financial condition and near‑term prospects of the issuer, and (iii) 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 (i) it intends to sell the security or (ii) 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 of the security. If the Company determines that it (i) does not intend to sell the security and (ii) 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 (i) the amount of impairment related to credit loss and (ii) 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 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 accreted or 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, is at the current market rate, 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 through a valuation allowance. Other real estate owned totaled approximately $30,519,000 and $42,204,000 at December 31, 2017 and 2016, 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, 2017 and 2016, 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, 2017, 2016 and 2015, 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 2014. 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, 2017, 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, 2017, 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 five active operating subsidiaries, namely, the bank subsidiaries, otherwise known as International Bank of Commerce, Laredo, International Bank of Commerce, Oklahoma City, 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 May 2014, the FASB 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 to in exchange for those goods or services. The update also outlines the steps that entities should take to determine and record the current revenue number including: (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract(s), (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract(s), and (v) recognize revenue when (or as) the entity satisfies the identified performance obligations in the contract(s). The update was originally effective for annual periods beginning after December 31, 2016 and the interim periods within that reporting period. In August 2015, the FASB issued Accounting Standards Update No. 2015-14 which deferred the effective date of ASU 2014-09 by one year to annual and interim periods beginning after December 15, 2017. The Company’s revenue is primarily comprised of net interest income on financial assets and financial liabilities, which is explicitly excluded from the scope of the update. The Company has evaluated the impact of the update to certain other non-interest revenue streams, including, service charges, insurance agency commissions and sales of other real estate, among others and has determined that the adoption of the update will not have a significant impact on the Company’s consolidated financial statements. In January 2016, the FASB issued Accounting Standards Update No. 2016-01 to ASC 825-10, “Financial Instruments – Overall.” The update amends existing standards regarding certain aspects of recognition and measurement of financial assets and financial liabilities. The amendments in the update establish the following guidance: (i) requires equity investments, except those accounted for under the equity method of accounting or those that result in consolidation of the investee, to be measured at fair value with changes in fair value recognized in net income, (ii) simplifies the impairment assessment of equity securities without readily determinable fair values by requiring a qualitative assessment, (iii) eliminates the requirement to disclose the fair value of financial instruments measured at amortized cost for entities that are not public business entities, (iv) eliminates the requirement for public business entities to disclose the methods and significant assumptions used to estimate fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet, (v) requires public business entities to use the exit price notion when measuring fair value for disclosure purposes, (vi) requires an entity to present separately, in other comprehensive income, the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option, (vii) requires separate presentation of financial assets and liabilities by measurement category and form of financial assets on the balance sheet or in the accompanying notes to the financial statements, and (viii) clarifies that an entity should evaluate the need to a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity’s other deferred tax assets. The update is effective for interim and annual periods beginning after December 15, 2017. The adoption of the update is will not have a significant impact to the Company’s consolidated financial statements. In February 2016, the FASB issued Accounting Standards Update No. 2016-02 to ASC 820, “Leases.” The update amends existing standards for accounting for leases by lessees, with accounting for leases by lessors remaining mainly unchanged from current guidance. The update requires that lessees recognize a lease liability and a right of use asset for all leases (with the exception of short-term leases) at the commencement date of the lease and disclose key information about leasing arrangements. The update is to be applied on a modified retrospective basis for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the consolidated financial statements. The update is effective for interim and annual periods beginning after December 15, 2018. In January 2018, the FASB issued a proposal that provides an additional transition method that would allow entities to not apply the guidance in the update in the comparative periods presented in the consolidated financial statements, but instead recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The Company is evaluating the potential impact to the Company’s consolidated financial statements. In March 2016, the FASB issued Accounting Standards Update No. 2016-09 to ASC 718, “Compensation – Stock Compensation.” The update amends existing standards for accounting for share-based payment transactions, including the income tax effects, the classification of awards on the balance sheet and the classification on the statement of cash flows. The update is effective for annual and interim periods after December 15, 2016. The adoption of the update did not have a significant impact to the Company’s consolidated financial statements. In June 2016, the FASB issued Accounting Standards Update No. 2016-13 to ASC 326, “Financial Instruments – Credit Losses.” The update amends existing standards for accounting for credit losses for financial assets. The update requires that the expected credit losses on the financial instruments held as of the end of the period being reported be measured based on historical experience, current conditions, and reasonable and supportable forecasts. The update also expands the required disclosures related to significant estimates and judgements used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s financial assets. The update also amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration and effective for interim and annual periods beginning after December 15, 2019. The change in accounting method represents a significant difference to current accounting practice over the accounting for credit losses on financial assets. The Company has formed a task force including key members of the teams that work with the current calculation of the allowance for probable loan losses and members representing the corporate accounting and risk management areas. The task force will be working with a plan to develop and implement the changes to current practice with support from third-party vendors. The Company cannot estimate at this time the impact of ASC 326. In January 2017, the FASB issued Accounting Standards Update No. 2017-04 to ASC 350, “Intangibles – Goodwill and Other.” The update amends existing guidance in evaluating goodwill for impairment. The update requires that an entity perform its annual or interim goodwill test by comparing the fair value of a reporting unit with its carrying amount, with any impairment charges being recognized as the difference between the fair value and carrying value. The update is intended to standardize the impairment test for all business entities and also reduce the complexity and cost of evaluating goodwill for impairment. The update is effective for any annual or interim goodwill impairment tests in fiscal years beginning after December 15, 2019. The adoption of the update is not expected to have a significant impact to the Company’s consolidated financial statements. In March 2017, the FASB issued Accounting Standards Update No. 2017-08 to ASC 310, “Receivables – Nonrefundable Fees and Other Costs.” The update amends existing guidance on the amortization period for certain callable debt securities held at a premium. The update shortens the amortization period of the premium to the earliest call date. The update is effective for fiscal years beginning after December 15, 2018. The update is to be applied on a modified retrospective basis through a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption. The adoption of the update is not expected to have a significant impact to the Company’s consolidated financial statements. In February 2018, the FASB issued Accounting Standards Update No. 2018-02 to ASC 220, “Income Statement – Reporting Comprehensive Income.” The update amends current guidance surrounding the reclassification of certain tax effects from accumulated other comprehensive income. The update is being issued as a result of the 2017 Tax Cu

Investment Securities

Investment Securities	12 Months Ended
	Dec. 31, 2017
Investment Securities
Investment Securities	(2) Investment Securities The amortized cost and estimated fair value by type of investment security at December 31, 2017 are as follows: Held to Maturity Gross Gross Amortized unrealized unrealized Estimated Carrying cost gains losses fair value value (Dollars in Thousands) Other securities $ 2,400 $ — $ — $ 2,400 $ 2,400 Total investment securities $ 2,400 $ — $ — $ 2,400 $ 2,400 Available for Sale Gross Gross Amortized unrealized unrealized Estimated Carrying cost gains losses fair value value (1) (Dollars in Thousands) Residential mortgage-backed securities $ 3,943,092 $ 14,110 $ (65,969) $ 3,891,233 $ 3,891,233 Obligations of states and political subdivisions 225,096 7,871 (16) 232,951 232,951 Equity securities 28,075 293 (482) 27,886 27,886 Total investment securities $ 4,196,263 $ 22,274 $ (66,467) $ 4,152,070 $ 4,152,070 (1) Included in the carrying value of residential mortgage‑ backed securities are $654,063 of mortgage‑backed securities issued by Ginnie Mae and $3,237,170 of mortgage‑backed securities issued by Fannie Mae and Freddie Mac The amortized cost and estimated fair value of investment securities at December 31, 2017 , 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 $ 2,275 $ 2,275 $ — $ — Due after one year through five years 125 125 — — Due after five years through ten years — — 1,939 1,967 Due after ten years — — 223,157 230,984 Residential mortgage-backed securities — — 3,943,092 3,891,233 Equity securities — — 28,075 27,886 Total investment securities $ 2,400 $ 2,400 $ 4,196,263 $ 4,152,070 The amortized cost and estimated fair value by type of investment security at December 31, 2016 are as follows: Held to Maturity Gross Gross Amortized unrealized unrealized Estimated Carrying cost gains losses fair value value (Dollars in Thousands) Other securities $ 2,400 $ — $ — $ 2,400 $ 2,400 Total investment securities $ 2,400 $ — $ — $ 2,400 $ 2,400 Available for Sale Gross Gross Estimated Amortized unrealized unrealized fair Carrying cost gains losses value value (1) (Dollars in Thousands) Residential mortgage-backed securities $ 3,946,144 $ 18,246 $ (69,920) $ 3,894,470 $ 3,894,470 Obligations of states and political subdivisions 244,622 10,783 (433) 254,972 254,972 Equity securities 28,075 314 (482) 27,907 27,907 Total investment securities $ 4,218,841 $ 29,343 $ (70,835) $ 4,177,349 $ 4,177,349 (1) Included in the carrying value of residential mortgage‑ backed securities are $850,033 of mortgage‑backed securities issued by Ginnie Mae, $3,026,832 of mortgage‑backed securities issued by Fannie Mae and Freddie Mac and $17,605 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 $1,428,387,000 and $1,403,084,000, respectively, at December 31, 2017. Proceeds from the sale and call of securities available‑for‑sale were $396,066,000, $352,743,000 and $164,163,000 during 2017, 2016 and 2015, respectively, which amounts included $377,756,000, $338,138,000 and $128,444,000 of mortgage‑backed securities. Gross gains of $1,186,000, $586,000 and $2,450,000, and gross losses of $5,960,000, $3,212,000 and $6,132,000 were realized on the sales in 2017, 2016 and 2015, 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, 2017 were as follows: Less than 12 months 12 months or more Total Unrealized Unrealized Unrealized Fair Value Losses Fair Value Losses Fair Value Losses (Dollars in Thousands) Available for sale: Residential mortgage-backed securities $ 1,061,577 $ (13,157) $ 2,029,455 $ (52,812) $ 3,091,032 $ (65,969) Obligations of states and political subdivisions 5,534 (9) 522 (7) 6,056 (16) Equity securities 11,499 (251) 8,019 (231) 19,518 (482) $ 1,078,610 $ (13,417) $ 2,037,996 $ (53,050) $ 3,116,606 $ (66,467) 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, 2016 were as follows: Less than 12 months 12 months or more Total Unrealized Unrealized Unrealized Fair Value Losses Fair Value Losses Fair Value Losses (Dollars in Thousands) Available for sale: Residential mortgage-backed securities $ 2,513,872 $ (52,245) $ 396,695 $ (17,675) $ 2,910,567 $ (69,920) Obligations of states and political subdivisions 31,104 (433) — — 31,104 (433) Equity securities 14,066 (184) 5,452 (298) 19,518 (482) $ 2,559,042 $ (52,862) $ 402,147 $ (17,973) $ 2,961,189 $ (70,835) 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 more likely than 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 had a small investment in non‑agency residential mortgage‑backed securities that had additional market volatility beyond economically induced interest rate events, which were sold in the first quarter of 2017. The Company concluded that the investments in non‑agency residential mortgage‑backed securities were other‑than‑temporarily impaired due to both credit and other than credit issues. No impairment charges were recorded in 2017. Impairment charges of $354,000 ($230,100, after tax) and $954,000 ($620,1000, after tax) were recorded in 2016 and 2015, 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 likely than 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, 2017 (in Thousands): Balance at December 31, 2016 $ Sale of other-than-temporarily impaired available-for-sale securities during period (13,931) Balance at December 31, 2017 $ — 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, 2016 (in Thousands): Balance at December 31, 2015 $ Impairment charges recognized during period Balance at December 31, 2016 $ 13,931 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, 2015 (in Thousands): Balance at December 31, 2014 $ Impairment charges recognized during period Balance at December 31, 2015 $ 13,577

Loans

Loans	12 Months Ended
	Dec. 31, 2017
Loans
Loans	(3) Loans A summary of loans, by loan type at December 31, 2017 and 2016 is as follows: December 31, December 31, 2017 2016 (Dollars in Thousands) Commercial, financial and agricultural $ 3,322,668 $ 2,993,203 Real estate - mortgage 1,133,525 1,032,222 Real estate - construction 1,683,550 1,716,875 Consumer 49,543 55,168 Foreign 158,886 167,220 Total loans $ 6,348,172 $ 5,964,688

Allowance for Probable Loan Los

Allowance for Probable Loan Losses	12 Months Ended
	Dec. 31, 2017
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. 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. World and U.S. economic conditions have continued to improve; however, there remains some uncertainty created by continued issues with negative demographic trends, weak labor participation rates, enormous government debt, excessive regulations, and unfunded entitlement programs that could create a financial crisis. The impact to the world and U.S. economy from these issues is being magnified by a lack of appropriate government action to find solutions to the problems. In the Company’s market area, the challenges are further magnified by the uncertainty around the renegotiation of the North American Free Trade Agreement (“NAFTA”), and whether such negotiations will advance NAFTA or repeal it. 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 is 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, 2017 Domestic Foreign Commercial real estate: other Commercial construction & real estate: Commercial land farmland & real estate: Residential: Residential: Commercial development commercial multifamily first lien junior lien Consumer Foreign Total (Dollars in Thousands) Balance at December 31, $ 25,649 $ 13,889 $ 16,731 $ 806 $ 2,455 $ 3,716 $ 531 $ 884 $ 64,661 Losses charge to allowance (12,094) (213) (40) — (101) (340) (309) (1) (13,098) Recoveries credited to allowance 4,020 21 527 — 11 258 45 21 4,903 Net losses charged to allowance (8,074) (192) 487 — (90) (82) (264) 20 (8,195) Provision (credit) charged to operations 10,330 (2,022) (555) 303 585 2,469 173 (62) 11,221 Balance at December 31, $ 27,905 $ 11,675 $ 16,663 $ 1,109 $ 2,950 $ 6,103 $ 440 $ 842 $ 67,687 December 31, 2016 Domestic Foreign Commercial real estate: other Commercial construction & real estate: Commercial land farmland & real estate: Residential: Residential: Commercial development commercial multifamily first lien junior lien Consumer Foreign Total (Dollars in Thousands) Balance at December 31, $ 21,431 $ 13,920 $ 19,769 $ 1,248 $ 3,509 $ 5,321 $ 638 $ 1,152 $ 66,988 Losses charge to allowance (32,959) (16) (1,890) (180) (70) (331) (414) (41) (35,901) Recoveries credited to allowance 7,110 6,099 119 — 21 278 69 19 13,715 Net losses charged to allowance (25,849) 6,083 (1,771) (180) (49) (53) (345) (22) (22,186) Provision (credit) charged to operations 30,067 (6,114) (1,267) (262) (1,005) (1,552) 238 (246) 19,859 Balance at December 31, $ 25,649 $ 13,889 $ 16,731 $ 806 $ 2,455 $ 3,716 $ 531 $ 884 $ 64,661 December 31, 2015 Domestic Foreign Commercial real estate: other Commercial construction & real estate: Commercial land farmland & real estate: Residential: Residential: Commercial development commercial multifamily first lien junior lien Consumer Foreign Total (Dollars in Thousands) Balance at December 31, $ 22,352 $ 12,955 $ 18,683 $ 846 $ 3,589 $ 4,683 $ 660 $ 1,060 $ 64,828 Losses charge to allowance (24,802) (695) (492) — (157) (275) (704) — (27,125) Recoveries credited to allowance 3,135 141 963 — 30 431 170 10 4,880 Net losses charged to allowance (21,667) (554) 471 — (127) 156 (534) 10 (22,245) Provision (credit) charged to operations 20,746 1,519 615 402 47 482 512 82 24,405 Balance at December 31, $ 21,431 $ 13,920 $ 19,769 $ 1,248 $ 3,509 $ 5,321 $ 638 $ 1,152 $ 66,988 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 decrease in the provision for probable loan losses charged to expense for the year ended December 31, 2017 can be attributed to a decrease in the historical loss experience in the commercial category of the calculation. As discussed in prior periods, charge-offs increased from historical levels due to the deterioration of one relationship that is secured by multiple pieces of transportation equipment beginning in the fourth quarter of 2014. The Company uses a three year historical charge-off experience in the calculation, therefore, as those charge-offs are eliminated from the calculation, the allowance for probable loan losses is impacted. On August 26, 2017, Hurricane Harvey made landfall in Rockport, Texas, as a category four storm and followed the Gulf Coast of Texas north to the Houston metro area and finally the State of Louisiana. The Texas Gulf Coast is an area where the Company serves many consumer and commercial customers. The Company has reviewed the exposure to losses of property arising from the impact of Hurricane Harvey and has determined that the impact is not significant to warrant a specific reserve; however, it is still evaluating the impact, therefore the Company’s allowance for probable loan losses at December 31, 2017 includes factors in the qualitative ratios used in the calculation to incorporate the potential impact of losses arising from the impact of Hurricane Harvey on certain portions of the loan portfolio. The increase in losses charged to the allowance for probable loan losses for the year ended December 31, 2016 can be attributed to further deterioration in the previously identified and charged down relationship primarily secured by multiple pieces of transportation equipment. In March 2016, litigation against the management of the borrower was filed in the State of Nevada, resulting in a going concern issue with the borrower’s operations and the future use of the transportation equipment pledged as collateral on the relationship. As a result, management, in accordance with its credit review procedures, re-evaluated the collateral values on the equipment in light of the new circumstances and reduced the collateral values accordingly, resulting in a further charge-down of the relationship of approximately $19.4 million, which is included in the losses charged to the allowance in the commercial category in the table detailing the year ended December 31, 2016 activity. The impact of the charge-down is also reflected in the various tables in this Note including impaired loans, non-accrual loans and the credit quality indicator summary. Two large recoveries on loans charged off in prior years are included in the recoveries credited to the allowance in the table detailing activity for the year ended December 31, 2016. The recoveries occurred in the first and third quarters of 2016 in the amounts of $4.4 million and $6 million, respectively and are included in the Commercial and Commercial Real Estate: Other Construction and Land Development categories. The increase in charge-offs for the years ended December 31, 2015 in the Commercial category can be attributed to a charge down of the previously discussed relationship that is primarily secured by multiple pieces of transportation equipment. The relationship was charged down by $13.5 million for the year ended December 31, 2015. 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, 2017 Loans Individually Loans Collectively Evaluated For Evaluated For Impairment Impairment Recorded Recorded Investment Allowance Investment Allowance (Dollars in Thousands) Domestic Commercial $ 17,947 $ 300 $ 1,068,520 $ 27,605 Commercial real estate: other construction & land development 2,455 116 1,681,095 11,559 Commercial real estate: farmland & commercial 33,123 18 2,010,162 16,645 Commercial real estate: multifamily 476 — 192,440 1,109 Residential: first lien 6,852 — 425,925 2,950 Residential: junior lien 723 — 700,025 6,103 Consumer 1,281 — 48,262 440 Foreign 347 — 158,539 842 Total $ 63,204 $ 434 $ 6,284,968 $ 67,253 December 31, 2016 Loans Individually Loans Collectively Evaluated For Evaluated For Impairment Impairment Recorded Recorded Investment Allowance Investment Allowance (Dollars in Thousands) Domestic Commercial $ 22,412 $ — $ 887,255 $ 25,649 Commercial real estate: other construction & land development 4,776 371 1,712,099 13,518 Commercial real estate: farmland & commercial 10,810 546 1,932,260 16,185 Commercial real estate: multifamily 552 — 139,914 806 Residential: first lien 6,836 44 415,068 2,411 Residential: junior lien 978 — 609,340 3,716 Consumer 1,295 — 53,873 531 Foreign 746 — 166,474 884 Total $ 48,405 $ 961 $ 5,916,283 $ 63,700 Loans accounted for on a non‑accrual basis at December 31, 2017, 2016 and 2015 amounted to $54,730,000, $37,245,000 and $47,685,000, respectively. The effect of such non‑accrual loans reduced interest income by approximately $977,000, $2,461,000 and $3,298,000 for the years ended December 31, 2017, 2016 and 2015, 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, 2017, 2016 and 2015 amounted to approximately $7,257,000, $5,226,000 and $11,616,000, respectively. The table below provides additional information on loans accounted for on a non‑accrual basis by loan class: December 31, 2017 December 31, 2016 (Dollars in Thousands) Domestic Commercial $ 17,909 $ 22,369 Commercial real estate: other construction & land development 2,455 4,776 Commercial real estate: farmland & commercial 33,123 8,314 Commercial real estate: multifamily 476 552 Residential: first lien 712 655 Residential: junior lien 11 166 Consumer 44 26 Foreign — 387 Total non-accrual loans $ 54,730 $ 37,245 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 (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 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 following tables detail key information regarding the Company’s impaired loans by loan class for the year ended December 31, 2017: December 31, 2017 Unpaid Average Recorded Principal Related Recorded Interest Investment Balance Allowance Investment Recognized (Dollars in Thousands) Loans with Related Allowance Domestic Commercial $ 1,300 $ 1,577 $ 300 $ 1,346 $ — Commercial real estate: other construction & land development 145 169 116 150 — Commercial real estate: farmland & commercial 449 590 18 489 — Total impaired loans with related allowance $ 1,894 $ 2,336 $ 434 $ 1,985 $ — December 31, 2017 Unpaid Average Recorded Principal Recorded Interest Investment Balance Investment Recognized (Dollars in Thousands) Loans with No Related Allowance Domestic Commercial $ 16,646 $ 44,095 $ 19,615 $ 3 Commercial real estate: other construction & land development 2,310 2,455 3,493 — Commercial real estate: farmland & commercial 32,675 33,275 38,536 — Commercial real estate: multifamily 476 505 511 — Residential: first lien 6,852 6,968 7,249 324 Residential: junior lien 723 736 970 45 Consumer 1,281 1,283 1,293 3 Foreign 347 347 750 16 Total impaired loans with no related allowance $ 61,310 $ 89,664 $ 72,417 $ 391 The following tables detail key information regarding the Company’s impaired loans by loan class for the year ended December 31, 2016: December 31, 2016 Unpaid Average Recorded Principal Related Recorded Interest Investment Balance Allowance Investment Recognized (Dollars in Thousands) Loans with Related Allowance Domestic Commercial real estate: other construction & land development $ 1,958 $ 1,971 $ 371 2,512 — Commercial real estate: farmland & commercial 2,808 3,948 546 3,247 — Commercial real estate: multifamily 62 62 44 62 — Total impaired loans with related allowance $ 4,828 $ 5,981 $ 961 $ 9,579 $ — December 31, 2016 Unpaid Average Recorded Principal Recorded Interest Investment Balance Investment Recognized (Dollars in Thousands) Loans with No Related Allowance Domestic Commercial $ 21,412 $ 50,737 $ 19,354 $ 3 Commercial real estate: other construction & land development 2,818 4,419 2,336 67 Commercial real estate: farmland & commercial 8,002 9,054 8,523 110 Commercial real estate: multifamily 552 562 401 — Residential: first lien 6,774 6,847 6,860 298 Residential: junior lien 978 1,017 1,011 52 Consumer 1,295 1,295 1,214 1 Foreign 746 746 751 16 Total impaired loans with no related allowance $ 42,577 $ 74,677 $ 40,450 $ 547 A portion of the impaired loans have adequate collateral and credit enhancements not requiring a related allowance for loan loss. 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. 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 collectible 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, 2017 December 31, 2016 (Dollars in Thousands) Domestic Commercial $ 6,910 $ 10,710 Commercial real estate: farmland & commercial — 3,086 Residential: first lien 6,140 6,181 Residential: junior lien 712 812 Consumer 1,237 1,269 Foreign 347 360 Total troubled debt restructuring $ 15,346 $ 22,418 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, 2017 and December 31, 2016, 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, 2017 90 Days or Total 30 - 59 60 - 89 90 Days or greater & Past Total Days Days Greater still accruing Due Current Portfolio (Dollars in Thousands) Domestic Commercial $ 3,790 $ 398 $ 18,308 $ 537 $ 22,496 $ 1,063,971 $ 1,086,467 Commercial real estate: other construction & land development 354 308 820 6 1,482 1,682,068 1,683,550 Commercial real estate: farmland & commercial 3,925 518 31,133 954 35,576 2,007,709 2,043,285 Commercial real estate: multifamily 84 — 476 — 560 192,356 192,916 Residential: first lien 4,295 2,458 4,095 3,861 10,848 421,929 432,777 Residential: junior lien 1,310 580 1,110 1,099 3,000 697,748 700,748 Consumer 868 98 160 133 1,126 48,417 49,543 Foreign 1,229 69 667 667 1,965 156,921 158,886 Total past due loans $ 15,855 $ 4,429 $ 56,769 $ 7,257 $ 77,053 $ 6,271,119 $ 6,348,172 December 31, 2016 90 Days or Total 30 - 59 60 - 89 90 Days or greater & Past Total Days Days Greater still accruing Due Current Portfolio (Dollars in Thousands) Domestic Commercial $ 4,081 $ 829 $ 21,123 $ 392 $ 26,033 $ 883,634 $ 909,667 Commercial real estate: other construction & land development 1,502 396 4,456 9 6,354 1,710,521 1,716,875 Commercial real estate: farmland & commercial 3,454 3,054 6,150 289 12,658 1,930,412 1,943,070 Commercial real estate: multifamily 44 — 552 — 596 139,870 140,466 Residential: first lien 5,615 1,350 4,143 3,756 11,108 410,796 421,904 Residential: junior lien 762 178 540 382 1,480 608,838 610,318 Consumer 910 95 413 387 1,418 53,750 55,168 Foreign 931 425 397 11 1,753 165,467 167,220 Total past due loans $ 17,299 $ 6,327 $ 37,774 $ 5,226 $ 61,400 $ 5,903,288 $ 5,964,688 The increase in the commercial real estate: farmland and commercial in the 90 days and greater category at December 31, 2017 compared to December 31, 2016 can be attributed to a relationship that is secured by a water park that is currently classified as Impaired. 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 provision 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. A summary of the loan portfolio by credit quality indicator by loan class is as follows: December 31, 2017 Special Watch Watch List— Watch List— Pass Review List—Pass Substandard Impaired (Dollars in Thousands) Domestic Commercial $ 905,707 $ — $ 3,170 $ 159,643 $ 17,947 Commercial real estate: other construction & land development 1,616,604 1,288 672 62,531 2,455 Commercial real estate: farmland & commercial 1,863,763 5,134 41,820 99,445 33,123 Commercial real estate: multifamily 192,440 — — — 476 Residential: first lien 425,811 40 — 74 6,852 Residential: junior lien 699,875 150 — — 723 Consumer 48,262 — — — 1,281 Foreign 158,539 — — — 347 Total $ 5,911,001 $ 6,612 $ 45,662 $ 321,693 $ 63,204 December 31, 2016 Special Watch Watch List— Watch List— Pass Review List—Pass Substandard Impaired (Dollars in Thousands) Domestic Commercial $ 720,350 $ 90,746 $ 1,121 $ 75,038 $ 22,412 Commercial real estate: other construction & land development 1,648,633 1,986 — 61,480 4,776 Commercial real estate: farmland & commercial 1,792,542 7,983 59,872 71,863 10,810 Commercial real estate: multifamily 139,914 — — — 552 Residential: first lien 413,638 814 — 616 6,836 Residential: junior lien 609,190 150 — — 978 Consumer 53,873 — — — 1,295 Foreign 166,474 — — — 746 Total $ 5,544,614 $ 101,679 $ 60,993 $ 208,997 $ 48,405 The decrease in Special review credits for December 31, 2017 compared to December 31, 2016 can be attributed to the reclassification of a relationship secured by barges used in the transportation of petroleum products from Special Review to Watch List - Substandard and by the reclassification of a relationship secured by equipment used in oil and gas production from Special Review to the Pass category. The decrease in the Watch List – Pass credits for December 31, 2017 compared to December 31, 2016 can be attributed to a relationship secured by real estate from Watch List – Pass to the Pass category. The increase in Watch List – Substandard credits at December 31, 2017 compared to December 31, 2016 can be primarily attributed to the relationship mentioned above, in addition to the reclassification of three additional relationships from Pass to Watch List – Substandard. One such relationship is in the oil and gas production business, one is in the water park business and is secured by a water park, and one is secured by construction equipment. Additionally, there was an increase in the outstanding balance on a relationship primarily secured by transportation equipment, which was already classified as Watch List-Substandard at December 31, 2016 .

Bank Premises and Equipment

Bank Premises and Equipment	12 Months Ended
	Dec. 31, 2017
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, 2017 and 2016 were as follows: Estimated useful lives 2017 2016 (Dollars in Thousands) Bank buildings and improvements 5 - 40 years $ 550,094 $ 542,063 Furniture, equipment and vehicles 1 - 20 years 289,743 280,586 Land 123,087 125,213 Real estate held for future expansion: Land, building, furniture, fixture and equipment 7 - 27 years — — Less: accumulated depreciation (448,470) (420,279) Bank premises and equipment, net $ 514,454 $ 527,583

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2017
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. A small portion of the fully amortized identified intangibles represent 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 Amount Amortization Net (Dollars in Thousands) December 31, 2017: Core deposit premium $ 58,675 $ 58,675 $ — Identified intangible (contract rights) 2,022 2,022 — Total identified intangibles $ 60,697 $ 60,697 $ — December 31, 2016: Core deposit premium $ 58,675 $ 58,650 $ 25 Identified intangible (contract rights) 2,022 2,022 — Total identified intangibles $ 60,697 $ 60,672 $ 25 Amortization expense of intangible assets for the years ended December 31, 2017, 2016 and 2015, was $25,000, $128,000 and $644,000, respectively. There were no changes in the carrying amount of goodwill for the years ended December 31, 2017 and 2016.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2017
Deposits.
Deposits	(7) Deposits Deposits as of December 31, 2017 and 2016 and related interest expense for the years ended December 31, 2017, 2016 and 2015 were as follows: 2017 2016 (Dollars in Thousands) Deposits: Demand - non-interest bearing Domestic $ 2,609,932 $ 2,509,544 Foreign 633,323 648,507 Total demand non-interest bearing 3,243,255 3,158,051 Savings and interest bearing demand Domestic 2,615,143 2,589,675 Foreign 629,988 614,053 Total savings and interest bearing demand 3,245,131 3,203,728 Time, certificates of deposit $100,000 or more Domestic 637,006 748,104 Foreign 808,881 838,161 Less than $100,000 Domestic 354,998 389,682 Foreign 255,621 272,363 Total time, certificates of deposit 2,056,506 2,248,310 Total deposits $ 8,544,892 $ 8,610,089 2017 2016 2015 (Dollars in Thousands) Interest expense: Savings and interest bearing demand Domestic $ 5,453 $ 3,922 $ 3,026 Foreign 755 640 567 Total savings and interest bearing demand 6,208 4,562 3,593 Time, certificates of deposit $100,000 or more Domestic 3,644 3,881 4,693 Foreign 4,105 3,929 4,116 Less than $100,000 Domestic 1,312 1,447 1,680 Foreign 675 706 744 Total time, certificates of deposit 9,736 9,963 11,233 Total interest expense on deposits $ 15,944 $ 14,525 $ 14,826 Scheduled maturities of time deposits as of December 31, 2017 were as follows: Total (in Thousands) 2018 $ 1,859,507 2019 139,276 2020 41,572 2021 13,303 2022 2,760 Thereafter 88 Total $ 2,056,506 Scheduled maturities of time deposits in amounts of $100,000 or more at December 31, 2017, were as follows: Total (in Thousands) Due within 3 months or less $ 557,206 Due after 3 months and within 6 months 348,695 Due after 6 months and within 12 months 404,776 Due after 12 months 135,210 $ 1,445,887 Time deposits that meet or exceed the FDIC insurance limit of $250,000 at December 31, 2017 and December 31, 2016 were $894,000 and $1,005,000, in thousands, respectively.

Securities Sold Under Repurchas

Securities Sold Under Repurchase Agreements	12 Months Ended
	Dec. 31, 2017
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 securities and averaged $ 402,396,000 and $759,458,000 during 2017 and 2016, respectively, and the maximum amount outstanding at any month end during 2017 and 2016 was $514,616,000 and $819,155,000 respectively. Further information related to repurchase agreements at December 31, 2017 and 2016 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, 2017 term: Overnight agreements $ 340,054 $ 334,506 $ 242,824 0.25 % 1 to 29 days — — — — 30 to 90 days 109,300 107,238 100,000 3.99 Over 90 days 11,327 11,168 10,981 0.74 Total $ 460,681 $ 452,912 $ 353,805 1.32 % December 31, 2016 term: Overnight agreements $ 295,282 $ 292,286 $ 190,915 0.15 % 1 to 29 days 10,250 10,148 9,863 30 to 90 days 2,315 2,317 2,300 0.33 Over 90 days 382,304 375,060 301,907 4.01 Total $ 690,151 $ 679,811 $ 504,985 2.46 % 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, 2017
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. The increase in other borrowed funds is a result of purchases of available‑for‑sale securities. Further information regarding the Company’s other borrowed funds at December 31, 2017 and 2016 is set forth in the following table: December 31, 2017 2016 (Dollars in Thousands) Federal Home Loan Bank advances—short-term Balance at year end $ 945,225 $ 583,375 Rate on balance outstanding at year end 1.44 % 0.66 % Average daily balance $ 839,858 $ 483,379 Average rate 1.23 % 0.47 % Maximum amount outstanding at any month end $ 1,043,250 $ 600,875 Federal Home Loan Bank advances—long-term (1) Balance at year end $ 250,000 $ 150,000 Rate on balance outstanding at year end 1.26 % 0.58 % Average daily balance $ 51,644 $ 150,000 Average rate 1.26 % 0.58 % Maximum amount outstanding at any month end $ 250,000 $ 150,000 (1) Long-term advances outstanding at December 31, 2017 mature in the following increments: $100,000,000 in November 2027 and $150,000,000 in December 2027 and are callable by the FHLB on a quarterly basis. Long-Term advances outstanding at December 31, 2016 matured in January 2017.

Junior Subordinated Deferrable

Junior Subordinated Deferrable Interest Debentures	12 Months Ended
	Dec. 31, 2017
Junior Subordinated Deferrable Interest Debentures
Junior Subordinated Deferrable Interest Debentures	(10) Junior Subordinated Deferrable Interest Debentures The Company has formed six statutory business trusts under the laws of the State of Delaware, for the purpose of issuing trust preferred securities. The 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, 2017 and December 31, 2016, the principal amount of debentures outstanding totaled $160,416,000. On July 29, 2015, the Company bought back a portion of the Capital Securities of IB Capital Trusts X and XI from the holder of the securities for a price that reflected an approximate 24.5% discount from the redemption prices of the securities. The Company thereby retired $13,000,000 of the total $34,021,000 of related Junior Subordinated Deferrable Interest Debentures related to IB Capital Trust X and $1,000,000 of the total $27,990,000 of related Junior Subordinated Deferrable Interest Debentures related to IB Capital Trust XI. On November 1, 2016, 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 24% discount from the redemption price of the securities. The Company thereby retired $1,000,000 of the total $26,990,000 of related Junior Subordinated Deferrable Interest Debentures related to IB Capital Trust XI. The discounts recorded in connection with the repurchases of the outstanding Capital Securities are included in other income on the consolidated financial statements. 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, 2017 and December 31, 2016, the total $160,416,000 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, 2017: Junior Subordinated Deferrable Interest Repricing Interest Interest Optional Debentures Frequency Rate Rate Index(1) Maturity Date Redemption Date (1) (Dollars in Thousands) Trust VI $ 25,774 Quarterly 4.87 % LIBOR + November 2032 February 2008 Trust VIII 25,774 Quarterly 4.41 % LIBOR + October 2033 October 2008 Trust IX 41,238 Quarterly 2.96 % LIBOR + October 2036 October 2011 Trust X 21,021 Quarterly 3.03 % LIBOR + February 2037 February 2012 Trust XI 25,990 Quarterly 2.96 % LIBOR + July 2037 July 2012 Trust XII 20,619 Quarterly 2.93 % LIBOR + September 2037 September 2012 $ 160,416 (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, 2017
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, 2017, 2016, and 2015 is set forth in the following table: Net Income Shares Per Share (Numerator) (Denominator) Amount (Dollars in Thousands, Except Per Share Amounts) December 31, 2017: Basic EPS Net income available to common shareholders $ 157,436 66,046,155 $ 2.38 Potential dilutive common shares and warrants — 732,281 Diluted EPS $ 157,436 66,778,436 $ 2.36 December 31, 2016: Basic EPS Net income available to common shareholders $ 133,932 65,967,989 $ 2.03 Potential dilutive common shares and warrants — 345,501 Diluted EPS $ 133,932 66,313,490 $ 2.02 December 31, 2015: Basic EPS Net income available to common shareholders $ 136,726 66,411,193 $ 2.06 Potential dilutive common shares — 225,160 Diluted EPS $ 136,726 66,636,353 $ 2.05

Employees' Profit Sharing Plan

Employees' Profit Sharing Plan	12 Months Ended
	Dec. 31, 2017
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 $3,750,000 $3,650,000 and $3,525,000 were charged to income for the years ended December 31, 2017, 2016, and 2015, respectively.

International Operations

International Operations	12 Months Ended
	Dec. 31, 2017
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, 2017 and 2016 are as follows: 2017 2016 (Dollars in Thousands) Loans: Commercial $ 113,019 $ 124,079 Others 45,867 43,141 158,886 167,220 Less allowance for probable loan losses (842) (884) Net loans $ 158,044 $ 166,336 Accrued interest receivable $ 671 $ 603 At December 31, 2017, the Company had $99,547,000 in outstanding standby and commercial letters of credit to facilitate trade activities. Revenues directly attributable to international operations were approximately $5,248,000, $5,495,000 and $6,113,000 for the years ended December 31, 2017, 2016 and 2015, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
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: 2017 2016 2015 (Dollars in Thousands) Current U.S. $ 56,974 $ 52,403 $ 65,196 State 2,662 3,362 5,258 Foreign — — (6) Total current taxes 59,636 55,765 70,448 Deferred U.S. 4,620 7,279 (261) State (50) 27 (71) Total deferred taxes 4,570 7,306 (332) Total income taxes $ 64,206 $ 63,071 $ 70,116 Total income tax expense differs from the amount computed by applying the U.S. Federal income tax rate of 35% for 2017, 2016 and 2015 to income before income taxes. The reasons for the differences for the years ended December 31 are as follows: 2017 2016 2015 (Dollars in Thousands) Computed expected tax expense $ 77,643 $ 69,253 $ 72,389 Change in taxes resulting from: Tax-exempt interest income (4,701) (3,940) (3,910) State tax, net of federal income taxes, tax credit and refunds 1,697 3,287 3,371 Resolution of IRS exam (4,985) — — Other investment income (3,198) (3,694) (3,540) Deferred tax adjustment due to federal tax rate change (3,168) — — Other 918 (1,835) 1,806 Actual tax expense $ 64,206 $ 63,071 $ 70,116 The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and deferred tax liabilities at December 31, 2017 and 2016 are reflected below: 2017 2016 (Dollars in Thousands) Deferred tax assets: Loans receivable, principally due to the allowance for probable loan losses $ 14,546 $ 24,315 Other real estate owned 2,053 3,652 Impairment charges on available-for-sale securities 844 6,086 Accrued expenses 81 137 Net unrealized losses on available for sale investment securities 9,680 14,791 Other 4,434 6,917 Total deferred tax assets 31,638 55,898 Deferred tax liabilities: Bank premises and equipment, principally due to differences on depreciation (10,940) (19,837) Identified intangible assets and goodwill (13,417) (21,386) Other (12,474) (16,300) Total deferred tax liabilities (36,831) (57,523) Net deferred tax liability $ (5,193) $ (1,625) The net deferred tax liability of $5,193,000 at December 31, 2017 and $1,625,000 at December 31, 2016 is included in other liabilities in the consolidated statements of condition. In September 2014, the Company amended its 2012 federal income tax return as a result of a tax opinion obtained regarding a judgment against the Company paid in 2012 afer litigation related to tax matters in the Company’s 2004 acquidition of Local Financial Corporation (“LFIN”). Litigation against the Company was initiated by the former controlling shareholders of LFIN with respect to such tax matters. On March 5, 2010, a judgment against the Company was entered on a jury verdict in the U.S. District Court for the Western District of Oklahoma. The Company subsequently appealed the decision and on January 5, 2012, the United States Court of Appeals Tenth Circuit affirmed the judgment and it became final and unappealable and the Company recorded the majority of the payment of the judgment as a non-deductible expense in the Company’s 2012 federal income tax return. The Company engaged legal counsel to review the deductibility of the judgment and, upon receiving the tax opinion, amended the 2012 tax return to report the payment as a deductible expense. The Internal Revenue Service examined the amended return and at the conclusion of the exam, allowed a certain portion of the judgment to be deducted as a necessary and ordinary business expense, resulting in a tax refund of $4.9 million. On December 22, 2017, the Tax Cuts and Jobs Act (“Tax Act”) was signed into law. The Tax Act materially changes U.S. corporate income tax rates, among other things. The Company was in a net deferred tax liability position at the time the Tax Act was enacted and subsequently revalued the carrying value of the net deferred liability and its components to the new 21% effective tax rate. The change in the tax rate resulted in a net benefit to the Company of $3,168,000 and is included as a reduction to income tax expense in the consolidated income statement.

Stock Options

Stock Options	12 Months Ended
	Dec. 31, 2017
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, 2017, 216,400 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. 2017 (1) 2016 Expected Life (Years) — 7.61 Dividend yield — % 2.50 % Interest rate — % 1.50 % Volatility — % 41.32 % (1) No stock options were granted during the twelve months ended December 31, 2017. A summary of option activity under the stock option plans for the twelve months ended December 31, 2017 is as follows: Weighted Weighted average average remaining Aggregate Number of exercise contractual intrinsic options price term (years) value ($) (in Thousands) Options outstanding at December 31, 2016 800,502 $ Plus: Options granted — — Less: Options exercised 108,885 Options expired 2,188 Options forfeited 21,263 Options outstanding at December 31, 2017 668,166 $ 12,887 Options fully vested and exercisable at December 31, 2017 283,472 $ $ 5,975 Stock‑based compensation expense included in the consolidated statements of income for the years ended December 31, 2017, 2016 and 2015 was approximately $903,000, $1,082,000 and $1,172,000, respectively. As of December 31, 2017, there was approximately $1,418,000 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 1.4 years. Other information pertaining to option activity during the twelve month period ending December 31, 2017, 2016 and 2015 is as follows: Twelve Months Ended December 31, 2017 (1) 2016 2015 Weighted average grant date fair value of stock options granted $ — $ 8.74 $ 9.42 Total fair value of stock options vested $ 1,182,000 $ 1,015,000 $ 872,000 Total intrinsic value of stock options exercised $ 2,595,000 $ 792,000 $ 781,000 (1) No stock options were granted during the twelve months ended December 31, 2017.

Long Term Restricted Stock Unit

Long Term Restricted Stock Units	12 Months Ended
	Dec. 31, 2017
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. No grants have been made under the Plan since December 2012 and there are currently no outstanding grants under the Plan.

Commitments, Contingent Liabili

Commitments, Contingent Liabilities and Other Matters	12 Months Ended
	Dec. 31, 2017
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, 2017, 2016 and 2015 were approximately $5,258,000, $5,870,000 and $6,200,000, respectively. Future minimum lease payments due under non‑cancellable operating leases at December 31, 2017 were as follows: Fiscal year ending: Total (in thousands) 2018 $ 3,563 2019 3,376 2020 3,087 2021 2,037 2022 494 Thereafter 180 Total $ 12,737 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, 2017 were $92,416,000. Cash of approximately $116,129,000 and $111,353,000 at December 31, 2017 and 2016, respectively, was maintained to satisfy regulatory reserve requirements. The Company is involved in various legal proceedings that are in various stages of litigation. 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 Parti

Transactions with Related Parties	12 Months Ended
	Dec. 31, 2017
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 $27,626,000 and $26,547,000 at December 31, 2017 and 2016, respectively.

Financial Instruments with Off-

Financial Instruments with Off-Statement of Condition Risk and Concentrations of Credit Risk	12 Months Ended
	Dec. 31, 2017
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, 2017, the following financial amounts of instruments, whose contract amounts represent credit risks, were outstanding: Commitments to extend credit $ 2,795,137,000 Credit card lines 20,643,000 Standby letters of credit 95,402,000 Commercial letters of credit 4,145,000 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, 2017, the maximum potential amount of future payments is approximately $95,402,000. At December 31, 2017, the fair value of these guarantees is not significant. Unsecured letters of credit totaled approximately $35,409,000 and $40,738,000 at December 31, 2017 and 2016, 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, 2017
Capital Requirements
Capital Requirements	(20) Capital Requirements On December 23, 2008, as part of the Troubled Asset Relief Program Capital Purchase Program of the United States Department of the Treasury (“Treasury”), the Company issued to the Treasury 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”). On June 12, 2013, the U.S. Treasury sold the Warrant to a third party. As of February 20, 2016, 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, 2017, the subsidiary banks could pay dividends of up to $731,850,000 to the Corporation without prior regulatory approval and without adversely affecting their “well‑capitalized” status under regulatory capital rules in effect at December 31, 2017. 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, 2017, that the Company and each of the bank subsidiaries met all capital adequacy requirements to which they are subject. On November 21, 2017, the OCC, the Federal Reserve and the FDIC finalized a proposed rule that extends the current treatment under the regulatory capital rules for certain regulatory capital deductions and risk weights and certain minority interest requirements, as they apply to banking organizations that are not subject to the advanced approaches capital rules. Effective January 1, 2018, the rule also pauses the full transition to the Basel III treatment of mortgage servicing assets, certain deferred tax assets, investments in the capital of unconsolidated financial institutions and minority interests. The agencies are also considering whether to make adjustments to the capital rules in response to CECL (the FASB Standard relating to current expected credit loss) and its potential impact on regulatory capital. On December 7, 2017, the Basel Committee on Banking Supervision unveiled the latest round of its regulatory capital framework, commonly called “Basel IV.” The framework makes changes to the capital framework first introduced as “Basel III” in 2010. The committee targeted 2022-2027 as the timeframe for implementation by regulators in individual countries, including the U.S. federal bank regulatory agencies (after notice and comment). The aforementioned capital conservation buffer is designed to absorb losses during periods of economic stress. Banking institutions with a ratio of CET1 capital to risk-weighted assets above the minimum but below the conservation buffer will face constraints on dividends, equity repurchases and compensation based on the amount of the shortfall. As of December 31, 2017, capital levels at the Company exceed all capital adequacy requirements under the Basel III Capital Rules as currently applicable to the Company. Based on the ratios presented below, capital levels as of December 31, 2017 at the Company exceed the minimum levels necessary to be considered “well capitalized.” As of December 31, 2017, 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 2017 under current guidelines are presented in the following table: For Capital Adequacy To Be Well-Capitalized Purposes Under Prompt Corrective Actual Phase In Schedule 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, 2017: Common Equity Tier 1 (to Risk Weighted Assets): Consolidated $ 1,584,665 % $ 532,579 % N/A N/A International Bank of Commerce, Laredo 1,119,173 376,245 $ 425,320 % International Bank of Commerce, Oklahoma 169,279 72,586 82,054 International Bank of Commerce, Brownsville 165,034 36,583 41,355 International Bank of Commerce, Zapata 66,406 12,487 14,116 Commerce Bank 79,330 13,733 15,524 Total Capital (to Risk Weighted Assets): Consolidated $ 1,807,107 % $ 856,757 % N/A N/A International Bank of Commerce, Laredo 1,173,068 605,263 $ 654,339 % International Bank of Commerce, Oklahoma 178,057 116,769 126,237 International Bank of Commerce, Brownsville 170,613 58,851 63,623 International Bank of Commerce, Zapata 68,718 20,088 21,717 Commerce Bank 81,278 22,092 23,884 Tier 1 Capital (to Risk Weighted Assets): Consolidated $ 1,734,595 % $ 671,512 % N/A N/A International Bank of Commerce, Laredo 1,119,173 474,395 $ 523,471 % International Bank of Commerce, Oklahoma 169,279 91,521 100,989 International Bank of Commerce, Brownsville 165,034 46,127 50,899 International Bank of Commerce, Zapata 66,406 15,745 17,374 Commerce Bank 79,330 17,316 19,107 Tier 1 Capital (to Average Assets): Consolidated $ 1,734,595 % $ 474,675 % $ N/A N/A International Bank of Commerce, Laredo 1,119,173 333,166 416,458 % International Bank of Commerce, Oklahoma 169,279 59,854 74,818 International Bank of Commerce, Brownsville 165,034 38,440 48,050 International Bank of Commerce, Zapata 66,406 18,701 23,376 Commerce Bank 79,330 21,789 27,236 The Company’s and the bank subsidiaries’ actual capital amounts and ratios for 2016 are also presented in the following table: To Be Well-Capitalized For Capital Adequacy Under Prompt Corrective Actual Purposes 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, 2016: Common Equity Tier 1 (to Risk Weighted Assets): Consolidated $ 1,468,662 % $ 444,190 % N/A N/A International Bank of Commerce, Laredo 1,201,527 370,342 $ 469,701 % International Bank of Commerce, Brownsville 158,533 31,720 40,230 International Bank of Commerce, Zapata 65,989 9,922 12,584 Commerce Bank 73,765 11,872 15,058 Total Capital (to Risk Weighted Assets): Consolidated $ 1,687,501 % $ 747,540 % N/A N/A International Bank of Commerce, Laredo 1,260,886 623,258 $ 722,618 % International Bank of Commerce, Brownsville 163,937 53,382 61,892 International Bank of Commerce, Zapata 67,464 16,698 19,360 Commerce Bank 76,093 19,980 23,166 Tier 1 Capital (to Risk Weighted Assets): Consolidated $ 1,618,935 % $ 574,197 % N/A N/A International Bank of Commerce, Laredo 1,201,527 478,734 $ 578,094 % International Bank of Commerce, Brownsville 158,533 41,004 49,514 International Bank of Commerce, Zapata 65,989 12,826 15,488 Commerce Bank 73,765 15,347 18,532 Tier 1 Capital (to Average Assets): Consolidated $ 1,618,935 % $ 465,438 % $ N/A N/A International Bank of Commerce, Laredo 1,201,527 384,342 480,427 % International Bank of Commerce, Brownsville 158,533 37,509 46,886 International Bank of Commerce, Zapata 65,989 19,029 23,786 Commerce Bank 73,765 22,607 28,259

Fair Value

Fair Value	12 Months Ended
	Dec. 31, 2017
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, 2017 by level within the fair value measurement hierarchy. Fair Value Measurements at Reporting Date Using (in Thousands) Quoted Prices in Active Significant Assets/Liabilities Markets for Other Significant Measured at Identical Observable Unobservable Fair Value Assets Inputs Inputs December 31, 2017 (Level 1) (Level 2) (Level 3) Measured on a recurring basis: Assets: Available for sale securities Residential mortgage-backed securities $ 3,891,233 $ — $ 3,891,233 $ — States and political subdivisions 232,951 — 232,951 — Equity Securities 27,886 27,886 — — $ 4,152,070 $ 27,886 $ 4,124,184 $ — The following table represents financial instruments reported on the consolidated balance sheets at their fair value as of December 31, 2016 by level within the fair value measurement hierarchy. Fair Value Measurements at Reporting Date Using (in Thousands) Quoted Prices in Active Significant Assets/Liabilities Markets for Other Significant Measured at Identical Observable Unobservable Fair Value Assets Inputs Inputs December 31, 2016 (Level 1) (Level 2) (Level 3) Measured on a recurring basis: Assets: Available for sale securities Residential mortgage - backed securities $ 3,894,470 $ — $ 3,876,865 $ 17,605 States and political subdivisions 254,972 — 254,972 — Equity Securities 27,907 27,907 — — $ 4,177,349 $ 27,907 $ 4,131,837 $ 17,605 For the year ended December 31, 2017, investment securities available‑for‑sale are classified within level 2 of the valuation hierarchy, with the exception of certain equity investments that are classified within level 1. For the year ended December 31, 2016, the Company had certain securities classified within level 3 of the fair value hierarchy. Those investments were sold in the first quarter of 2017. 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, 2016 for investment securities classified within level 3 of the fair value hierarchy, 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 four years (2013, 2014, 2015, and 2016), and (iv) a discount rate of 13%. The estimates used in the model to determine fair value were based on observable historical data of the underlying collateral. The following table presents a reconciliation of activity for such mortgage‑backed securities on a net basis (Dollars in Thousands): Balance at December 31, 2016 $ Principal paydowns (798) Sales of available for sale securities (21,904) Reclassification of unrealized gains (losses) included in other comprehensive loss due to sale 5,097 Balance at December 31, 2017 $ — 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, 2017 by level within the fair value measurement hierarchy: Fair Value Measurements at Reporting Date Using (in thousands) Quoted Assets/Liabilities Prices in Measured at Active Significant Fair Value Markets for Other Significant Net Provision Year ended Identical Observable Unobservable (Credit) December 31, Assets Inputs Inputs During 2017 (Level 1) (Level 2) (Level 3) Period Measured on a non-recurring basis: Assets: Impaired loans $ 11,210 $ — $ — $ 11,210 $ 2,138 Other real estate owned 2,000 — — 2,000 710 The following table represents financial instruments measured at fair value on a non‑recurring basis as of and for the year ended December 31, 2016 by level within the fair value measurement hierarchy: Fair Value Measurements at Reporting Date Using (in thousands) Quoted Assets/Liabilities Prices in Measured at Active Significant Fair Value Markets Other Significant Net (Credit) Year ended for Identical Observable Unobservable Provision December 31, Assets Inputs Inputs During 2016 (Level 1) (Level 2) (Level 3) Period Measured on a non-recurring basis: Assets: Impaired loans $ 38,794 $ — $ — $ 38,794 $ 19,699 Other real estate owned 9,445 — — 9,445 2,351 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, 2017, the Company had approximately $53,267,000 of impaired commercial collateral dependent loans, of which approximately $18,585,000 had an appraisal performed within the immediately preceding twelve months and of which approximately $0 had an evaluation performed within the immediately preceding twelve months. As of December 31, 2016, the Company had approximately $38,108,000 of impaired commercial collateral dependent loans, of which approximately $26,162,000 had an appraisal performed within the immediately preceding twelve months and of which approximately $6,836,000 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, 2017, December 31, 2016 and December 31, 2015, respectively the Company recorded approximately $30,000, $381,000 and $696,000 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, 2017, December 31, 2016 and December 31, 2015, respectively, the Company recorded approximately $710,000, $2,351,000 and $1,023,000 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, 2017 and December 31, 2016 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, 2017, and December 31, 2016, the carrying amount of fixed rate performing loans was $1,505,531,000 and $1,411,272,000, respectively, and the estimated fair value was $1,454,434,000 and $1,375,807,000, 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, 2017 and December 31, 2016. 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, 2017 and December 31, 2016, the carrying amount of time deposits was $2,056,506,000 and $2,248,310,000, respectively, and the estimated fair value was $2,058,621,000 and $2,247,648,000, 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, 2017 and December 31, 2016. The fair value of the long‑term instruments is based on established market spread using option adjusted spreads methodology. Long‑term repurchase agreements are within level 3 of the fair value hierarchy. At December 31, 2017 and December 31, 2016, respectively, the carrying amount of long‑term repurchase agreements was $100,000,000 and $300,000,000 and the estimated fair value was $99,504,000 and $289,324,000, 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, 2017 and December 31, 2016. 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, 2017 and December 31, 2016. The long-term borrowings outstanding at December 31, 2017 are fixed-rate borrowings and the fair value is based on established market spreads for similar types of borrowings. The fixed-rate long-term borrowings are included in Level 2 of the fair value hierarchy. At December 31, 2017, the carrying amount of the fixed-rate long-term FHLB borrowings was $250,000,000 and the estimated fair value was $249,728,000. 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 Corpor

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Condition	12 Months Ended
	Dec. 31, 2017
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, 2017 and 2016 (Dollars in Thousands) 2017 2016 ASSETS Cash $ 18,398 $ 18,555 Other investments 92,620 94,908 Investment in subsidiaries 1,878,521 1,787,120 Other assets 23,120 1,098 Total assets $ 2,012,659 $ 1,901,681 LIABILITIES AND SHAREHOLDERS’ EQUITY Liabilities: Junior subordinated deferrable interest debentures $ 160,416 $ 160,416 Due to IBC Trading 21 21 Other liabilities 13,242 16,577 Total liabilities 173,679 177,014 Shareholders’ equity: Common shares 96,019 95,910 Surplus 171,816 169,567 Retained earnings 1,891,805 1,777,963 Accumulated other comprehensive (loss) income (28,397) (26,697) 2,131,243 2,016,743 Less cost of shares in treasury (292,263) (292,076) Total shareholders’ equity 1,838,980 1,724,667 Total liabilities and shareholders’ equity $ 2,012,659 $ 1,901,681

International Bancshares Corp33

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Income	12 Months Ended
	Dec. 31, 2017
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, 2017, 2016 and 2015 (Dollars in Thousands) 2017 2016 2015 Income: Dividends from subsidiaries $ 64,600 $ 84,432 $ 51,575 Interest income on notes receivable — 2 7 Interest income on other investments 8,100 8,958 5,738 Other 26 255 3,442 Total income 72,726 93,647 60,762 Expenses: Interest expense (Debentures) 5,392 4,600 4,099 Other 5,648 3,637 3,037 Total expenses 11,040 8,237 7,136 Income before federal income taxes and equity in undistributed net income of subsidiaries 61,686 85,410 53,626 Income tax expense (2,076) 311 386 Income before equity in undistributed net income of subsidiaries 63,762 85,099 53,240 Equity in undistributed net income of subsidiaries 93,674 48,833 83,486 Net income $ 157,436 $ 133,932 $ 136,726

International Bancshares Corp34

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Cash Flows	12 Months Ended
	Dec. 31, 2017
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, 2017, 2016 and 2015 (Dollars in Thousands) 2017 2016 2015 Operating activities: Net income $ 157,436 $ 133,932 $ 136,726 Adjustments to reconcile net income to net cash provided by operating activities: Investment securities transactions, net (23) — — Impairment charges on available for sale securities — 112 385 Stock compensation expense 903 1,082 1,172 (Decrease) increase in other liabilities (3,453) 3,901 (1,998) Equity in undistributed net income of subsidiaries (93,674) (48,833) (83,486) Net cash provided by operating activities 61,189 90,194 52,799 Investing activities: Principal collected on mortgage-backed securities 6,328 1,105 474 Net decrease in notes receivable — 99 105 Increase in other assets and other investments (25,348) (27,834) (1,830) Net cash used in investing activities (19,020) (26,630) (1,251) Financing activities: Redemption of long-term debt — (1,000) (14,000) Proceeds from stock transactions 1,455 549 1,370 Payments of cash dividends - common (43,594) (39,569) (38,515) Purchase of treasury stock (187) (7,966) (6,678) Net cash used in financing activities (42,326) (47,986) (57,823) (Decrease) increase in cash (157) 15,578 (6,275) Cash at beginning of year 18,555 2,977 9,252 Cash at end of year $ 18,398 $ 18,555 $ 2,977

Summary of Significant Accoun35

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
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”), International Bank of Commerce, Oklahoma City, 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 (which was terminated in September 2016), 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 the Oklahoma 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 one insurance‑related subsidiary, IBC Insurance Agency, Inc., a wholly owned subsidiary of IBC, the bank subsidiary. The insurance‑related subsidiary does not conduct underwriting activities. 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 (loss) until realized. The Company did not maintain any trading securities during the three year period ended December 31, 2017. Mortgage‑backed securities held at December 31, 2017 and 2016 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 (i) the length of time and the extent to which the fair value has been less than cost, (ii) the financial condition and near‑term prospects of the issuer, and (iii) 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 (i) it intends to sell the security or (ii) 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 of the security. If the Company determines that it (i) does not intend to sell the security and (ii) 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 (i) the amount of impairment related to credit loss and (ii) 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 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 accreted or 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, is at the current market rate, 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 through a valuation allowance. Other real estate owned totaled approximately $30,519,000 and $42,204,000 at December 31, 2017 and 2016, 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, 2017 and 2016, 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, 2017, 2016 and 2015, 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 2014.
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, 2017, 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, 2017, 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 five active operating subsidiaries, namely, the bank subsidiaries, otherwise known as International Bank of Commerce, Laredo, International Bank of Commerce, Oklahoma City, 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 May 2014, the FASB 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 to in exchange for those goods or services. The update also outlines the steps that entities should take to determine and record the current revenue number including: (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract(s), (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract(s), and (v) recognize revenue when (or as) the entity satisfies the identified performance obligations in the contract(s). The update was originally effective for annual periods beginning after December 31, 2016 and the interim periods within that reporting period. In August 2015, the FASB issued Accounting Standards Update No. 2015-14 which deferred the effective date of ASU 2014-09 by one year to annual and interim periods beginning after December 15, 2017. The Company’s revenue is primarily comprised of net interest income on financial assets and financial liabilities, which is explicitly excluded from the scope of the update. The Company has evaluated the impact of the update to certain other non-interest revenue streams, including, service charges, insurance agency commissions and sales of other real estate, among others and has determined that the adoption of the update will not have a significant impact on the Company’s consolidated financial statements. In January 2016, the FASB issued Accounting Standards Update No. 2016-01 to ASC 825-10, “Financial Instruments – Overall.” The update amends existing standards regarding certain aspects of recognition and measurement of financial assets and financial liabilities. The amendments in the update establish the following guidance: (i) requires equity investments, except those accounted for under the equity method of accounting or those that result in consolidation of the investee, to be measured at fair value with changes in fair value recognized in net income, (ii) simplifies the impairment assessment of equity securities without readily determinable fair values by requiring a qualitative assessment, (iii) eliminates the requirement to disclose the fair value of financial instruments measured at amortized cost for entities that are not public business entities, (iv) eliminates the requirement for public business entities to disclose the methods and significant assumptions used to estimate fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet, (v) requires public business entities to use the exit price notion when measuring fair value for disclosure purposes, (vi) requires an entity to present separately, in other comprehensive income, the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option, (vii) requires separate presentation of financial assets and liabilities by measurement category and form of financial assets on the balance sheet or in the accompanying notes to the financial statements, and (viii) clarifies that an entity should evaluate the need to a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity’s other deferred tax assets. The update is effective for interim and annual periods beginning after December 15, 2017. The adoption of the update is will not have a significant impact to the Company’s consolidated financial statements. In February 2016, the FASB issued Accounting Standards Update No. 2016-02 to ASC 820, “Leases.” The update amends existing standards for accounting for leases by lessees, with accounting for leases by lessors remaining mainly unchanged from current guidance. The update requires that lessees recognize a lease liability and a right of use asset for all leases (with the exception of short-term leases) at the commencement date of the lease and disclose key information about leasing arrangements. The update is to be applied on a modified retrospective basis for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the consolidated financial statements. The update is effective for interim and annual periods beginning after December 15, 2018. In January 2018, the FASB issued a proposal that provides an additional transition method that would allow entities to not apply the guidance in the update in the comparative periods presented in the consolidated financial statements, but instead recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The Company is evaluating the potential impact to the Company’s consolidated financial statements. In March 2016, the FASB issued Accounting Standards Update No. 2016-09 to ASC 718, “Compensation – Stock Compensation.” The update amends existing standards for accounting for share-based payment transactions, including the income tax effects, the classification of awards on the balance sheet and the classification on the statement of cash flows. The update is effective for annual and interim periods after December 15, 2016. The adoption of the update did not have a significant impact to the Company’s consolidated financial statements. In June 2016, the FASB issued Accounting Standards Update No. 2016-13 to ASC 326, “Financial Instruments – Credit Losses.” The update amends existing standards for accounting for credit losses for financial assets. The update requires that the expected credit losses on the financial instruments held as of the end of the period being reported be measured based on historical experience, current conditions, and reasonable and supportable forecasts. The update also expands the required disclosures related to significant estimates and judgements used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s financial assets. The update also amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration and effective for interim and annual periods beginning after December 15, 2019. The change in accounting method represents a significant difference to current accounting practice over the accounting for credit losses on financial assets. The Company has formed a task force including key members of the teams that work with the current calculation of the allowance for probable loan losses and members representing the corporate accounting and risk management areas. The task force will be working with a plan to develop and implement the changes to current practice with support from third-party vendors. The Company cannot estimate at this time the impact of ASC 326. In January 2017, the FASB issued Accounting Standards Update No. 2017-04 to ASC 350, “Intangibles – Goodwill and Other.” The update amends existing guidance in evaluating goodwill for impairment. The update requires that an entity perform its annual or interim goodwill test by comparing the fair value of a reporting unit with its carrying amount, with any impairment charges being recognized as the difference between the fair value and carrying value. The update is intended to standardize the impairment test for all business entities and also reduce the complexity and cost of evaluating goodwill for impairment. The update is effective for any annual or interim goodwill impairment tests in fiscal years beginning after December 15, 2019. The adoption of the update is not expected to have a significant impact to the Company’s consolidated financial statements. In March 2017, the FASB issued Accounting Standards Update No. 2017-08 to ASC 310, “Receivables – Nonrefundable Fees and Other Costs.” The update amends existing guidance on the amortization period for certain callable debt securities held at a premium. The update shortens the amortization period of the premium to the earliest call date. The update is effective for fiscal years beginning after December 15, 2018. The update is to be applied on a modified retrospective basis through a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption. The adoption of the update is not expected to have a significant impact to the Company’s consolidated financial statements. In February 2018, the FASB issued Accounting Standards Update No. 2018-02 to ASC 220, “Income Statement – Reporting Comprehensive Income.” The update amends current guidance surrounding the reclassification of certain tax effects from accumulated other comprehensive income. The update is being issued as a result of the 2017 Tax Cuts and Jobs Act and the related impact to comprehensive income as a result of the application of current guidance with respect to changes in tax rates. Under current guidance, entities must re-evaluate the carrying value of deferred tax assets and liabilities and adjust them for the tax effect of the rate change and record that change through earnings. The result is that the tax effects for items that normally would only be recognized in comprehensive income will be recognized through earnings and results in stranded tax effects in accumulated other comprehensive income (loss) for the impact of the rate change. The update will allow a reclassification from accumulated other comprehensive income (loss) to retained earnings for the stranded tax effects resulting from the 2017 Tax Cuts and Jobs Act. The update is effective for all entities for fiscal years beginning after December 31, 2018. The adoption of the update is not expected to have a significant impact to the Company’s consolidated financial statements

Investment Securities (Tables)

Investment Securities (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017 are as follows: Held to Maturity Gross Gross Amortized unrealized unrealized Estimated Carrying cost gains losses fair value value (Dollars in Thousands) Other securities $ 2,400 $ — $ — $ 2,400 $ 2,400 Total investment securities $ 2,400 $ — $ — $ 2,400 $ 2,400 Available for Sale Gross Gross Amortized unrealized unrealized Estimated Carrying cost gains losses fair value value (1) (Dollars in Thousands) Residential mortgage-backed securities $ 3,943,092 $ 14,110 $ (65,969) $ 3,891,233 $ 3,891,233 Obligations of states and political subdivisions 225,096 7,871 (16) 232,951 232,951 Equity securities 28,075 293 (482) 27,886 27,886 Total investment securities $ 4,196,263 $ 22,274 $ (66,467) $ 4,152,070 $ 4,152,070 (1) Included in the carrying value of residential mortgage‑ backed securities are $654,063 of mortgage‑backed securities issued by Ginnie Mae and $3,237,170 of mortgage‑backed securities issued by Fannie Mae and Freddie Mac The amortized cost and estimated fair value by type of investment security at December 31, 2016 are as follows: Held to Maturity Gross Gross Amortized unrealized unrealized Estimated Carrying cost gains losses fair value value (Dollars in Thousands) Other securities $ 2,400 $ — $ — $ 2,400 $ 2,400 Total investment securities $ 2,400 $ — $ — $ 2,400 $ 2,400 Available for Sale Gross Gross Estimated Amortized unrealized unrealized fair Carrying cost gains losses value value (1) (Dollars in Thousands) Residential mortgage-backed securities $ 3,946,144 $ 18,246 $ (69,920) $ 3,894,470 $ 3,894,470 Obligations of states and political subdivisions 244,622 10,783 (433) 254,972 254,972 Equity securities 28,075 314 (482) 27,907 27,907 Total investment securities $ 4,218,841 $ 29,343 $ (70,835) $ 4,177,349 $ 4,177,349 (1) Included in the carrying value of residential mortgage‑ backed securities are $850,033 of mortgage‑backed securities issued by Ginnie Mae, $3,029,832 of mortgage‑backed securities issued by Fannie Mae and Freddie Mac and $17,605 issued by non‑government entities
Amortized cost and fair value of investment securities, by contractual maturity	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 $ 2,275 $ 2,275 $ — $ — Due after one year through five years 125 125 — — Due after five years through ten years — — 1,939 1,967 Due after ten years — — 223,157 230,984 Residential mortgage-backed securities — — 3,943,092 3,891,233 Equity securities — — 28,075 27,886 Total investment securities $ 2,400 $ 2,400 $ 4,196,263 $ 4,152,070
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, 2017 were as follows: Less than 12 months 12 months or more Total Unrealized Unrealized Unrealized Fair Value Losses Fair Value Losses Fair Value Losses (Dollars in Thousands) Available for sale: Residential mortgage-backed securities $ 1,061,577 $ (13,157) $ 2,029,455 $ (52,812) $ 3,091,032 $ (65,969) Obligations of states and political subdivisions 5,534 (9) 522 (7) 6,056 (16) Equity securities 11,499 (251) 8,019 (231) 19,518 (482) $ 1,078,610 $ (13,417) $ 2,037,996 $ (53,050) $ 3,116,606 $ (66,467) 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, 2016 were as follows: Less than 12 months 12 months or more Total Unrealized Unrealized Unrealized Fair Value Losses Fair Value Losses Fair Value Losses (Dollars in Thousands) Available for sale: Residential mortgage-backed securities $ 2,513,872 $ (52,245) $ 396,695 $ (17,675) $ 2,910,567 $ (69,920) Obligations of states and political subdivisions 31,104 (433) — — 31,104 (433) Equity securities 14,066 (184) 5,452 (298) 19,518 (482) $ 2,559,042 $ (52,862) $ 402,147 $ (17,973) $ 2,961,189 $ (70,835)
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, 2017 (in Thousands): Balance at December 31, 2016 $ Sale of other-than-temporarily impaired available-for-sale securities during period (13,931) Balance at December 31, 2017 $ — 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, 2016 (in Thousands): Balance at December 31, 2015 $ Impairment charges recognized during period Balance at December 31, 2016 $ 13,931 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, 2015 (in Thousands): Balance at December 31, 2014 $ Impairment charges recognized during period Balance at December 31, 2015 $ 13,577

Loans (Tables)

Loans (Tables)	12 Months Ended
	Dec. 31, 2017
Loans
Summary of loans, by loan type	December 31, December 31, 2017 2016 (Dollars in Thousands) Commercial, financial and agricultural $ 3,322,668 $ 2,993,203 Real estate - mortgage 1,133,525 1,032,222 Real estate - construction 1,683,550 1,716,875 Consumer 49,543 55,168 Foreign 158,886 167,220 Total loans $ 6,348,172 $ 5,964,688

Allowance for Probable Loan L38

Allowance for Probable Loan Losses (Tables)	12 Months Ended
	Dec. 31, 2017
Allowance for Probable Loan Losses
Summary of the transactions in the allowance for probable loan losses by loan class	December 31, 2017 Domestic Foreign Commercial real estate: other Commercial construction & real estate: Commercial land farmland & real estate: Residential: Residential: Commercial development commercial multifamily first lien junior lien Consumer Foreign Total (Dollars in Thousands) Balance at December 31, $ 25,649 $ 13,889 $ 16,731 $ 806 $ 2,455 $ 3,716 $ 531 $ 884 $ 64,661 Losses charge to allowance (12,094) (213) (40) — (101) (340) (309) (1) (13,098) Recoveries credited to allowance 4,020 21 527 — 11 258 45 21 4,903 Net losses charged to allowance (8,074) (192) 487 — (90) (82) (264) 20 (8,195) Provision (credit) charged to operations 10,330 (2,022) (555) 303 585 2,469 173 (62) 11,221 Balance at December 31, $ 27,905 $ 11,675 $ 16,663 $ 1,109 $ 2,950 $ 6,103 $ 440 $ 842 $ 67,687 December 31, 2016 Domestic Foreign Commercial real estate: other Commercial construction & real estate: Commercial land farmland & real estate: Residential: Residential: Commercial development commercial multifamily first lien junior lien Consumer Foreign Total (Dollars in Thousands) Balance at December 31, $ 21,431 $ 13,920 $ 19,769 $ 1,248 $ 3,509 $ 5,321 $ 638 $ 1,152 $ 66,988 Losses charge to allowance (32,959) (16) (1,890) (180) (70) (331) (414) (41) (35,901) Recoveries credited to allowance 7,110 6,099 119 — 21 278 69 19 13,715 Net losses charged to allowance (25,849) 6,083 (1,771) (180) (49) (53) (345) (22) (22,186) Provision (credit) charged to operations 30,067 (6,114) (1,267) (262) (1,005) (1,552) 238 (246) 19,859 Balance at December 31, $ 25,649 $ 13,889 $ 16,731 $ 806 $ 2,455 $ 3,716 $ 531 $ 884 $ 64,661 December 31, 2015 Domestic Foreign Commercial real estate: other Commercial construction & real estate: Commercial land farmland & real estate: Residential: Residential: Commercial development commercial multifamily first lien junior lien Consumer Foreign Total (Dollars in Thousands) Balance at December 31, $ 22,352 $ 12,955 $ 18,683 $ 846 $ 3,589 $ 4,683 $ 660 $ 1,060 $ 64,828 Losses charge to allowance (24,802) (695) (492) — (157) (275) (704) — (27,125) Recoveries credited to allowance 3,135 141 963 — 30 431 170 10 4,880 Net losses charged to allowance (21,667) (554) 471 — (127) 156 (534) 10 (22,245) Provision (credit) charged to operations 20,746 1,519 615 402 47 482 512 82 24,405 Balance at December 31, $ 21,431 $ 13,920 $ 19,769 $ 1,248 $ 3,509 $ 5,321 $ 638 $ 1,152 $ 66,988
Loans individually or collectively evaluated for their impairment and related allowance, by loan class	December 31, 2017 Loans Individually Loans Collectively Evaluated For Evaluated For Impairment Impairment Recorded Recorded Investment Allowance Investment Allowance (Dollars in Thousands) Domestic Commercial $ 17,947 $ 300 $ 1,068,520 $ 27,605 Commercial real estate: other construction & land development 2,455 116 1,681,095 11,559 Commercial real estate: farmland & commercial 33,123 18 2,010,162 16,645 Commercial real estate: multifamily 476 — 192,440 1,109 Residential: first lien 6,852 — 425,925 2,950 Residential: junior lien 723 — 700,025 6,103 Consumer 1,281 — 48,262 440 Foreign 347 — 158,539 842 Total $ 63,204 $ 434 $ 6,284,968 $ 67,253 December 31, 2016 Loans Individually Loans Collectively Evaluated For Evaluated For Impairment Impairment Recorded Recorded Investment Allowance Investment Allowance (Dollars in Thousands) Domestic Commercial $ 22,412 $ — $ 887,255 $ 25,649 Commercial real estate: other construction & land development 4,776 371 1,712,099 13,518 Commercial real estate: farmland & commercial 10,810 546 1,932,260 16,185 Commercial real estate: multifamily 552 — 139,914 806 Residential: first lien 6,836 44 415,068 2,411 Residential: junior lien 978 — 609,340 3,716 Consumer 1,295 — 53,873 531 Foreign 746 — 166,474 884 Total $ 48,405 $ 961 $ 5,916,283 $ 63,700
Loans accounted on non-accrual basis, by loan class	December 31, 2017 December 31, 2016 (Dollars in Thousands) Domestic Commercial $ 17,909 $ 22,369 Commercial real estate: other construction & land development 2,455 4,776 Commercial real estate: farmland & commercial 33,123 8,314 Commercial real estate: multifamily 476 552 Residential: first lien 712 655 Residential: junior lien 11 166 Consumer 44 26 Foreign — 387 Total non-accrual loans $ 54,730 $ 37,245
Impaired loans, by loan class	The following tables detail key information regarding the Company’s impaired loans by loan class for the year ended December 31, 2017: December 31, 2017 Unpaid Average Recorded Principal Related Recorded Interest Investment Balance Allowance Investment Recognized (Dollars in Thousands) Loans with Related Allowance Domestic Commercial $ 1,300 $ 1,577 $ 300 $ 1,346 $ — Commercial real estate: other construction & land development 145 169 116 150 — Commercial real estate: farmland & commercial 449 590 18 489 — Total impaired loans with related allowance $ 1,894 $ 2,336 $ 434 $ 1,985 $ — December 31, 2017 Unpaid Average Recorded Principal Recorded Interest Investment Balance Investment Recognized (Dollars in Thousands) Loans with No Related Allowance Domestic Commercial $ 16,646 $ 44,095 $ 19,615 $ 3 Commercial real estate: other construction & land development 2,310 2,455 3,493 — Commercial real estate: farmland & commercial 32,675 33,275 38,536 — Commercial real estate: multifamily 476 505 511 — Residential: first lien 6,852 6,968 7,249 324 Residential: junior lien 723 736 970 45 Consumer 1,281 1,283 1,293 3 Foreign 347 347 750 16 Total impaired loans with no related allowance $ 61,310 $ 89,664 $ 72,417 $ 391 The following tables detail key information regarding the Company’s impaired loans by loan class for the year ended December 31, 2016: December 31, 2016 Unpaid Average Recorded Principal Related Recorded Interest Investment Balance Allowance Investment Recognized (Dollars in Thousands) Loans with Related Allowance Domestic Commercial real estate: other construction & land development $ 1,958 $ 1,971 $ 371 2,512 — Commercial real estate: farmland & commercial 2,808 3,948 546 3,247 — Commercial real estate: multifamily 62 62 44 62 — Total impaired loans with related allowance $ 4,828 $ 5,981 $ 961 $ 9,579 $ — December 31, 2016 Unpaid Average Recorded Principal Recorded Interest Investment Balance Investment Recognized (Dollars in Thousands) Loans with No Related Allowance Domestic Commercial $ 21,412 $ 50,737 $ 19,354 $ 3 Commercial real estate: other construction & land development 2,818 4,419 2,336 67 Commercial real estate: farmland & commercial 8,002 9,054 8,523 110 Commercial real estate: multifamily 552 562 401 — Residential: first lien 6,774 6,847 6,860 298 Residential: junior lien 978 1,017 1,011 52 Consumer 1,295 1,295 1,214 1 Foreign 746 746 751 16 Total impaired loans with no related allowance $ 42,577 $ 74,677 $ 40,450 $ 547
Loans accounted for as trouble debt restructuring, by loan class	December 31, 2017 December 31, 2016 (Dollars in Thousands) Domestic Commercial $ 6,910 $ 10,710 Commercial real estate: farmland & commercial — 3,086 Residential: first lien 6,140 6,181 Residential: junior lien 712 812 Consumer 1,237 1,269 Foreign 347 360 Total troubled debt restructuring $ 15,346 $ 22,418
Information regarding the aging of past due loans, by loan class	December 31, 2017 90 Days or Total 30 - 59 60 - 89 90 Days or greater & Past Total Days Days Greater still accruing Due Current Portfolio (Dollars in Thousands) Domestic Commercial $ 3,790 $ 398 $ 18,308 $ 537 $ 22,496 $ 1,063,971 $ 1,086,467 Commercial real estate: other construction & land development 354 308 820 6 1,482 1,682,068 1,683,550 Commercial real estate: farmland & commercial 3,925 518 31,133 954 35,576 2,007,709 2,043,285 Commercial real estate: multifamily 84 — 476 — 560 192,356 192,916 Residential: first lien 4,295 2,458 4,095 3,861 10,848 421,929 432,777 Residential: junior lien 1,310 580 1,110 1,099 3,000 697,748 700,748 Consumer 868 98 160 133 1,126 48,417 49,543 Foreign 1,229 69 667 667 1,965 156,921 158,886 Total past due loans $ 15,855 $ 4,429 $ 56,769 $ 7,257 $ 77,053 $ 6,271,119 $ 6,348,172 December 31, 2016 90 Days or Total 30 - 59 60 - 89 90 Days or greater & Past Total Days Days Greater still accruing Due Current Portfolio (Dollars in Thousands) Domestic Commercial $ 4,081 $ 829 $ 21,123 $ 392 $ 26,033 $ 883,634 $ 909,667 Commercial real estate: other construction & land development 1,502 396 4,456 9 6,354 1,710,521 1,716,875 Commercial real estate: farmland & commercial 3,454 3,054 6,150 289 12,658 1,930,412 1,943,070 Commercial real estate: multifamily 44 — 552 — 596 139,870 140,466 Residential: first lien 5,615 1,350 4,143 3,756 11,108 410,796 421,904 Residential: junior lien 762 178 540 382 1,480 608,838 610,318 Consumer 910 95 413 387 1,418 53,750 55,168 Foreign 931 425 397 11 1,753 165,467 167,220 Total past due loans $ 17,299 $ 6,327 $ 37,774 $ 5,226 $ 61,400 $ 5,903,288 $ 5,964,688
Summary of the loan portfolio by credit quality indicator, by loan class	December 31, 2017 Special Watch Watch List— Watch List— Pass Review List—Pass Substandard Impaired (Dollars in Thousands) Domestic Commercial $ 905,707 $ — $ 3,170 $ 159,643 $ 17,947 Commercial real estate: other construction & land development 1,616,604 1,288 672 62,531 2,455 Commercial real estate: farmland & commercial 1,863,763 5,134 41,820 99,445 33,123 Commercial real estate: multifamily 192,440 — — — 476 Residential: first lien 425,811 40 — 74 6,852 Residential: junior lien 699,875 150 — — 723 Consumer 48,262 — — — 1,281 Foreign 158,539 — — — 347 Total $ 5,911,001 $ 6,612 $ 45,662 $ 321,693 $ 63,204 December 31, 2016 Special Watch Watch List— Watch List— Pass Review List—Pass Substandard Impaired (Dollars in Thousands) Domestic Commercial $ 720,350 $ 90,746 $ 1,121 $ 75,038 $ 22,412 Commercial real estate: other construction & land development 1,648,633 1,986 — 61,480 4,776 Commercial real estate: farmland & commercial 1,792,542 7,983 59,872 71,863 10,810 Commercial real estate: multifamily 139,914 — — — 552 Residential: first lien 413,638 814 — 616 6,836 Residential: junior lien 609,190 150 — — 978 Consumer 53,873 — — — 1,295 Foreign 166,474 — — — 746 Total $ 5,544,614 $ 101,679 $ 60,993 $ 208,997 $ 48,405

Bank Premises and Equipment (Ta

Bank Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Bank Premises and Equipment
Summary of bank premises and equipment, by asset classification	Estimated useful lives 2017 2016 (Dollars in Thousands) Bank buildings and improvements 5 - 40 years $ 550,094 $ 542,063 Furniture, equipment and vehicles 1 - 20 years 289,743 280,586 Land 123,087 125,213 Real estate held for future expansion: Land, building, furniture, fixture and equipment 7 - 27 years — — Less: accumulated depreciation (448,470) (420,279) Bank premises and equipment, net $ 514,454 $ 527,583

Goodwill and Other Intangible40

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Other Intangible Assets
Schedule of the entity's identified intangible assets	Carrying Accumulated Amount Amortization Net (Dollars in Thousands) December 31, 2017: Core deposit premium $ 58,675 $ 58,675 $ — Identified intangible (contract rights) 2,022 2,022 — Total identified intangibles $ 60,697 $ 60,697 $ — December 31, 2016: Core deposit premium $ 58,675 $ 58,650 $ 25 Identified intangible (contract rights) 2,022 2,022 — Total identified intangibles $ 60,697 $ 60,672 $ 25

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2017
Deposits.
Schedule of deposits and related interest expense	2017 2016 (Dollars in Thousands) Deposits: Demand - non-interest bearing Domestic $ 2,609,932 $ 2,509,544 Foreign 633,323 648,507 Total demand non-interest bearing 3,243,255 3,158,051 Savings and interest bearing demand Domestic 2,615,143 2,589,675 Foreign 629,988 614,053 Total savings and interest bearing demand 3,245,131 3,203,728 Time, certificates of deposit $100,000 or more Domestic 637,006 748,104 Foreign 808,881 838,161 Less than $100,000 Domestic 354,998 389,682 Foreign 255,621 272,363 Total time, certificates of deposit 2,056,506 2,248,310 Total deposits $ 8,544,892 $ 8,610,089 2017 2016 2015 (Dollars in Thousands) Interest expense: Savings and interest bearing demand Domestic $ 5,453 $ 3,922 $ 3,026 Foreign 755 640 567 Total savings and interest bearing demand 6,208 4,562 3,593 Time, certificates of deposit $100,000 or more Domestic 3,644 3,881 4,693 Foreign 4,105 3,929 4,116 Less than $100,000 Domestic 1,312 1,447 1,680 Foreign 675 706 744 Total time, certificates of deposit 9,736 9,963 11,233 Total interest expense on deposits $ 15,944 $ 14,525 $ 14,826
Scheduled maturities of time deposits	Scheduled maturities of time deposits as of December 31, 2017 were as follows: Total (in Thousands) 2018 $ 1,859,507 2019 139,276 2020 41,572 2021 13,303 2022 2,760 Thereafter 88 Total $ 2,056,506
Scheduled maturities of time deposits in amounts of $100,000 or more	Total (in Thousands) Due within 3 months or less $ 557,206 Due after 3 months and within 6 months 348,695 Due after 6 months and within 12 months 404,776 Due after 12 months 135,210 $ 1,445,887

Securities Sold Under Repurch42

Securities Sold Under Repurchase Agreements (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017 term: Overnight agreements $ 340,054 $ 334,506 $ 242,824 0.25 % 1 to 29 days — — — — 30 to 90 days 109,300 107,238 100,000 3.99 Over 90 days 11,327 11,168 10,981 0.74 Total $ 460,681 $ 452,912 $ 353,805 1.32 % December 31, 2016 term: Overnight agreements $ 295,282 $ 292,286 $ 190,915 0.15 % 1 to 29 days 10,250 10,148 9,863 30 to 90 days 2,315 2,317 2,300 0.33 Over 90 days 382,304 375,060 301,907 4.01 Total $ 690,151 $ 679,811 $ 504,985 2.46 %

Other Borrowed Funds (Tables)

Other Borrowed Funds (Tables)	12 Months Ended
	Dec. 31, 2017
Other Borrowed Funds
Schedule of other borrowed funds	December 31, 2017 2016 (Dollars in Thousands) Federal Home Loan Bank advances—short-term Balance at year end $ 945,225 $ 583,375 Rate on balance outstanding at year end 1.44 % 0.66 % Average daily balance $ 839,858 $ 483,379 Average rate 1.23 % 0.47 % Maximum amount outstanding at any month end $ 1,043,250 $ 600,875 Federal Home Loan Bank advances—long-term (1) Balance at year end $ 250,000 $ 150,000 Rate on balance outstanding at year end 1.26 % 0.58 % Average daily balance $ 51,644 $ 150,000 Average rate 1.26 % 0.58 % Maximum amount outstanding at any month end $ 250,000 $ 150,000 Long-term advances outstanding at December 31, 2017 mature in the following increments: $100,000,000 in November 2027 and $150,000,000 in December 2027 and are callable by the FHLB on a quarterly basis. Long-Term advances outstanding at December 31, 2016 matured in January 2017.

Junior Subordinated Interest De

Junior Subordinated Interest Deferrable Debentures (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017: Junior Subordinated Deferrable Interest Repricing Interest Interest Optional Debentures Frequency Rate Rate Index(1) Maturity Date Redemption Date (1) (Dollars in Thousands) Trust VI $ 25,774 Quarterly 4.87 % LIBOR + November 2032 February 2008 Trust VIII 25,774 Quarterly 4.41 % LIBOR + October 2033 October 2008 Trust IX 41,238 Quarterly 2.96 % LIBOR + October 2036 October 2011 Trust X 21,021 Quarterly 3.03 % LIBOR + February 2037 February 2012 Trust XI 25,990 Quarterly 2.96 % LIBOR + July 2037 July 2012 Trust XII 20,619 Quarterly 2.93 % LIBOR + September 2037 September 2012 $ 160,416 (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") (Tab

Earnings per Share ("EPS") (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017: Basic EPS Net income available to common shareholders $ 157,436 66,046,155 $ 2.38 Potential dilutive common shares and warrants — 732,281 Diluted EPS $ 157,436 66,778,436 $ 2.36 December 31, 2016: Basic EPS Net income available to common shareholders $ 133,932 65,967,989 $ 2.03 Potential dilutive common shares and warrants — 345,501 Diluted EPS $ 133,932 66,313,490 $ 2.02 December 31, 2015: Basic EPS Net income available to common shareholders $ 136,726 66,411,193 $ 2.06 Potential dilutive common shares — 225,160 Diluted EPS $ 136,726 66,636,353 $ 2.05

International Operations (Table

International Operations (Tables)	12 Months Ended
	Dec. 31, 2017
International Operations
Summary of assets attributable to international operations	2017 2016 (Dollars in Thousands) Loans: Commercial $ 113,019 $ 124,079 Others 45,867 43,141 158,886 167,220 Less allowance for probable loan losses (842) (884) Net loans $ 158,044 $ 166,336 Accrued interest receivable $ 671 $ 603

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Taxes
Schedule of current and deferred portions of net income tax expense	2017 2016 2015 (Dollars in Thousands) Current U.S. $ 56,974 $ 52,403 $ 65,196 State 2,662 3,362 5,258 Foreign — — (6) Total current taxes 59,636 55,765 70,448 Deferred U.S. 4,620 7,279 (261) State (50) 27 (71) Total deferred taxes 4,570 7,306 (332) Total income taxes $ 64,206 $ 63,071 $ 70,116
Schedule of income tax expense differences from the amount computed by applying the U.S. Federal income tax rate to income before income taxes	2017 2016 2015 (Dollars in Thousands) Computed expected tax expense $ 77,643 $ 69,253 $ 72,389 Change in taxes resulting from: Tax-exempt interest income (4,701) (3,940) (3,910) State tax, net of federal income taxes, tax credit and refunds 1,697 3,287 3,371 Resolution of IRS exam (4,985) — — Other investment income (3,198) (3,694) (3,540) Deferred tax adjustment due to federal tax rate change (3,168) — — Other 918 (1,835) 1,806 Actual tax expense $ 64,206 $ 63,071 $ 70,116
Schedule of tax effects of temporary difference that give rise to significant portions of the deferred tax assets and deferred tax liabilities	2017 2016 (Dollars in Thousands) Deferred tax assets: Loans receivable, principally due to the allowance for probable loan losses $ 14,546 $ 24,315 Other real estate owned 2,053 3,652 Impairment charges on available-for-sale securities 844 6,086 Accrued expenses 81 137 Net unrealized losses on available for sale investment securities 9,680 14,791 Other 4,434 6,917 Total deferred tax assets 31,638 55,898 Deferred tax liabilities: Bank premises and equipment, principally due to differences on depreciation (10,940) (19,837) Identified intangible assets and goodwill (13,417) (21,386) Other (12,474) (16,300) Total deferred tax liabilities (36,831) (57,523) Net deferred tax liability $ (5,193) $ (1,625)

Stock Options (Tables)

Stock Options (Tables)	12 Months Ended
	Dec. 31, 2017
Stock Options
Schedule of Black-Scholes-Merton option valuation model assumptions	2017 (1) 2016 Expected Life (Years) — 7.61 Dividend yield — % 2.50 % Interest rate — % 1.50 % Volatility — % 41.32 % (1) No stock options were granted during the twelve months ended December 31, 2017.
Summary of option activity under stock option plans	Weighted Weighted average average remaining Aggregate Number of exercise contractual intrinsic options price term (years) value ($) (in Thousands) Options outstanding at December 31, 2016 800,502 $ Plus: Options granted — — Less: Options exercised 108,885 Options expired 2,188 Options forfeited 21,263 Options outstanding at December 31, 2017 668,166 $ 12,887 Options fully vested and exercisable at December 31, 2017 283,472 $ $ 5,975
Schedule of other information pertaining to option activity	Twelve Months Ended December 31, 2017 (1) 2016 2015 Weighted average grant date fair value of stock options granted $ — $ 8.74 $ 9.42 Total fair value of stock options vested $ 1,182,000 $ 1,015,000 $ 872,000 Total intrinsic value of stock options exercised $ 2,595,000 $ 792,000 $ 781,000 (1) No stock options were granted during the twelve months ended December 31, 2017.

Commitments, Contingent Liabi49

Commitments, Contingent Liabilities and Other Matters (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments, Contingent Liabilities and Other Matters
Schedule of future minimum lease payments due under non-cancellable operating leases	Total (in thousands) 2018 $ 3,563 2019 3,376 2020 3,087 2021 2,037 2022 494 Thereafter 180 Total $ 12,737

Financial Instruments with Of50

Financial Instruments with Off-Statement of Condition Risk and Concentrations of Credit Risk (Tables)	12 Months Ended
	Dec. 31, 2017
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	Commitments to extend credit $ 2,795,137,000 Credit card lines 20,643,000 Standby letters of credit 95,402,000 Commercial letters of credit 4,145,000

Capital Requirements (Tables)

Capital Requirements (Tables)	12 Months Ended
	Dec. 31, 2017
Capital Requirements
Schedule of the Company's and the bank subsidiaries' actual capital amounts and ratios	The Company’s and the bank subsidiaries’ actual capital amounts and ratios for 2017 under current guidelines are presented in the following table: For Capital Adequacy To Be Well-Capitalized Purposes Under Prompt Corrective Actual Phase In Schedule 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, 2017: Common Equity Tier 1 (to Risk Weighted Assets): Consolidated $ 1,584,665 % $ 532,579 % N/A N/A International Bank of Commerce, Laredo 1,119,173 376,245 $ 425,320 % International Bank of Commerce, Oklahoma 169,279 72,586 82,054 International Bank of Commerce, Brownsville 165,034 36,583 41,355 International Bank of Commerce, Zapata 66,406 12,487 14,116 Commerce Bank 79,330 13,733 15,524 Total Capital (to Risk Weighted Assets): Consolidated $ 1,807,107 % $ 856,757 % N/A N/A International Bank of Commerce, Laredo 1,173,068 605,263 $ 654,339 % International Bank of Commerce, Oklahoma 178,057 116,769 126,237 International Bank of Commerce, Brownsville 170,613 58,851 63,623 International Bank of Commerce, Zapata 68,718 20,088 21,717 Commerce Bank 81,278 22,092 23,884 Tier 1 Capital (to Risk Weighted Assets): Consolidated $ 1,734,595 % $ 671,512 % N/A N/A International Bank of Commerce, Laredo 1,119,173 474,395 $ 523,471 % International Bank of Commerce, Oklahoma 169,279 91,521 100,989 International Bank of Commerce, Brownsville 165,034 46,127 50,899 International Bank of Commerce, Zapata 66,406 15,745 17,374 Commerce Bank 79,330 17,316 19,107 Tier 1 Capital (to Average Assets): Consolidated $ 1,734,595 % $ 474,675 % $ N/A N/A International Bank of Commerce, Laredo 1,119,173 333,166 416,458 % International Bank of Commerce, Oklahoma 169,279 59,854 74,818 International Bank of Commerce, Brownsville 165,034 38,440 48,050 International Bank of Commerce, Zapata 66,406 18,701 23,376 Commerce Bank 79,330 21,789 27,236 The Company’s and the bank subsidiaries’ actual capital amounts and ratios for 2016 are also presented in the following table: To Be Well-Capitalized For Capital Adequacy Under Prompt Corrective Actual Purposes 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, 2016: Common Equity Tier 1 (to Risk Weighted Assets): Consolidated $ 1,468,662 % $ 444,190 % N/A N/A International Bank of Commerce, Laredo 1,201,527 370,342 $ 469,701 % International Bank of Commerce, Brownsville 158,533 31,720 40,230 International Bank of Commerce, Zapata 65,989 9,922 12,584 Commerce Bank 73,765 11,872 15,058 Total Capital (to Risk Weighted Assets): Consolidated $ 1,687,501 % $ 747,540 % N/A N/A International Bank of Commerce, Laredo 1,260,886 623,258 $ 722,618 % International Bank of Commerce, Brownsville 163,937 53,382 61,892 International Bank of Commerce, Zapata 67,464 16,698 19,360 Commerce Bank 76,093 19,980 23,166 Tier 1 Capital (to Risk Weighted Assets): Consolidated $ 1,618,935 % $ 574,197 % N/A N/A International Bank of Commerce, Laredo 1,201,527 478,734 $ 578,094 % International Bank of Commerce, Brownsville 158,533 41,004 49,514 International Bank of Commerce, Zapata 65,989 12,826 15,488 Commerce Bank 73,765 15,347 18,532 Tier 1 Capital (to Average Assets): Consolidated $ 1,618,935 % $ 465,438 % $ N/A N/A International Bank of Commerce, Laredo 1,201,527 384,342 480,427 % International Bank of Commerce, Brownsville 158,533 37,509 46,886 International Bank of Commerce, Zapata 65,989 19,029 23,786 Commerce Bank 73,765 22,607 28,259

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value
Assets and liabilities measured at fair value on a recurring basis	The following table represents financial instruments reported on the consolidated statements of condition at their fair value as of December 31, 2017 by level within the fair value measurement hierarchy. Fair Value Measurements at Reporting Date Using (in Thousands) Quoted Prices in Active Significant Assets/Liabilities Markets for Other Significant Measured at Identical Observable Unobservable Fair Value Assets Inputs Inputs December 31, 2017 (Level 1) (Level 2) (Level 3) Measured on a recurring basis: Assets: Available for sale securities Residential mortgage-backed securities $ 3,891,233 $ — $ 3,891,233 $ — States and political subdivisions 232,951 — 232,951 — Equity Securities 27,886 27,886 — — $ 4,152,070 $ 27,886 $ 4,124,184 $ — The following table represents financial instruments reported on the consolidated balance sheets at their fair value as of December 31, 2016 by level within the fair value measurement hierarchy. Fair Value Measurements at Reporting Date Using (in Thousands) Quoted Prices in Active Significant Assets/Liabilities Markets for Other Significant Measured at Identical Observable Unobservable Fair Value Assets Inputs Inputs December 31, 2016 (Level 1) (Level 2) (Level 3) Measured on a recurring basis: Assets: Available for sale securities Residential mortgage - backed securities $ 3,894,470 $ — $ 3,876,865 $ 17,605 States and political subdivisions 254,972 — 254,972 — Equity Securities 27,907 27,907 — — $ 4,177,349 $ 27,907 $ 4,131,837 $ 17,605
Reconciliation of activity for mortgage-backed securities on a net basis	Balance at December 31, 2016 $ Principal paydowns (798) Sales of available for sale securities (21,904) Reclassification of unrealized gains (losses) included in other comprehensive loss due to sale 5,097 Balance at December 31, 2017 $ —
Assets measured at fair value on a non-recurring basis	The following table represents financial instruments measured at fair value on a non‑recurring basis as of and for the period ended December 31, 2017 by level within the fair value measurement hierarchy: Fair Value Measurements at Reporting Date Using (in thousands) Quoted Assets/Liabilities Prices in Measured at Active Significant Fair Value Markets for Other Significant Net Provision Year ended Identical Observable Unobservable (Credit) December 31, Assets Inputs Inputs During 2017 (Level 1) (Level 2) (Level 3) Period Measured on a non-recurring basis: Assets: Impaired loans $ 11,210 $ — $ — $ 11,210 $ 2,138 Other real estate owned 2,000 — — 2,000 710 The following table represents financial instruments measured at fair value on a non‑recurring basis as of and for the year ended December 31, 2016 by level within the fair value measurement hierarchy: Fair Value Measurements at Reporting Date Using (in thousands) Quoted Assets/Liabilities Prices in Measured at Active Significant Fair Value Markets Other Significant Net (Credit) Year ended for Identical Observable Unobservable Provision December 31, Assets Inputs Inputs During 2016 (Level 1) (Level 2) (Level 3) Period Measured on a non-recurring basis: Assets: Impaired loans $ 38,794 $ — $ — $ 38,794 $ 19,699 Other real estate owned 9,445 — — 9,445 2,351

International Bancshares Corp53

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Condition (Tables)	12 Months Ended
	Dec. 31, 2017
International Bancshares Corporation (Parent Company Only) Financial Information Statements of Condition
Schedule of condensed statements of condition of Parent Company	(Dollars in Thousands) 2017 2016 ASSETS Cash $ 18,398 $ 18,555 Other investments 92,620 94,908 Investment in subsidiaries 1,878,521 1,787,120 Other assets 23,120 1,098 Total assets $ 2,012,659 $ 1,901,681 LIABILITIES AND SHAREHOLDERS’ EQUITY Liabilities: Junior subordinated deferrable interest debentures $ 160,416 $ 160,416 Due to IBC Trading 21 21 Other liabilities 13,242 16,577 Total liabilities 173,679 177,014 Shareholders’ equity: Common shares 96,019 95,910 Surplus 171,816 169,567 Retained earnings 1,891,805 1,777,963 Accumulated other comprehensive (loss) income (28,397) (26,697) 2,131,243 2,016,743 Less cost of shares in treasury (292,263) (292,076) Total shareholders’ equity 1,838,980 1,724,667 Total liabilities and shareholders’ equity $ 2,012,659 $ 1,901,681

International Bancshares Corp54

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Income (Tables)	12 Months Ended
	Dec. 31, 2017
International Bancshares Corporation (Parent Company Only) Financial Information Statements of Income
Schedule of condensed statements of income of Parent Company	(Dollars in Thousands) 2017 2016 2015 Income: Dividends from subsidiaries $ 64,600 $ 84,432 $ 51,575 Interest income on notes receivable — 2 7 Interest income on other investments 8,100 8,958 5,738 Other 26 255 3,442 Total income 72,726 93,647 60,762 Expenses: Interest expense (Debentures) 5,392 4,600 4,099 Other 5,648 3,637 3,037 Total expenses 11,040 8,237 7,136 Income before federal income taxes and equity in undistributed net income of subsidiaries 61,686 85,410 53,626 Income tax expense (2,076) 311 386 Income before equity in undistributed net income of subsidiaries 63,762 85,099 53,240 Equity in undistributed net income of subsidiaries 93,674 48,833 83,486 Net income $ 157,436 $ 133,932 $ 136,726

International Bancshares Corp55

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Cash Flows (Tables)	12 Months Ended
	Dec. 31, 2017
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) 2017 2016 2015 Operating activities: Net income $ 157,436 $ 133,932 $ 136,726 Adjustments to reconcile net income to net cash provided by operating activities: Investment securities transactions, net (23) — — Impairment charges on available for sale securities — 112 385 Stock compensation expense 903 1,082 1,172 (Decrease) increase in other liabilities (3,453) 3,901 (1,998) Equity in undistributed net income of subsidiaries (93,674) (48,833) (83,486) Net cash provided by operating activities 61,189 90,194 52,799 Investing activities: Principal collected on mortgage-backed securities 6,328 1,105 474 Net decrease in notes receivable — 99 105 Increase in other assets and other investments (25,348) (27,834) (1,830) Net cash used in investing activities (19,020) (26,630) (1,251) Financing activities: Redemption of long-term debt — (1,000) (14,000) Proceeds from stock transactions 1,455 549 1,370 Payments of cash dividends - common (43,594) (39,569) (38,515) Purchase of treasury stock (187) (7,966) (6,678) Net cash used in financing activities (42,326) (47,986) (57,823) (Decrease) increase in cash (157) 15,578 (6,275) Cash at beginning of year 18,555 2,977 9,252 Cash at end of year $ 18,398 $ 18,555 $ 2,977

Summary of Significant Accoun56

Summary of Significant Accounting Policies (Details)	Oct. 01, 2016USD ($)	Dec. 31, 2017USD ($)item	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Summary of Significant Accounting Policies
Number of insurance-related subsidiaries | item		1
Investment Securities
Number of components in which other-than-temporary impairment is segregated | item		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		$ 30,519,000	$ 42,204,000
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 | item		1
Number of active operating bank subsidiaries | item		5

Investment Securities (Details)

Investment Securities (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Held-to-maturity securities
Amortized cost	$ 2,400,000	$ 2,400,000
Estimated fair value	2,400,000	2,400,000
Carrying Value	2,400,000	2,400,000
Available-for-sale securities
Amortized Cost	4,196,263,000	4,218,841,000
Gross Unrealized Gains	22,274,000	29,343,000
Gross Unrealized Losses	(66,467,000)	(70,835,000)
Total Investment Securities	4,152,070,000	4,177,349,000
Assets/liabilities measured at fair value
Available-for-sale securities
Total Investment Securities	4,152,070,000	4,177,349,000
Carrying Value
Available-for-sale securities
Total Investment Securities	4,152,070,000	4,177,349,000
Residential mortgage-backed securities
Available-for-sale securities
Amortized Cost	3,943,092,000	3,946,144,000
Gross Unrealized Gains	14,110,000	18,246,000
Gross Unrealized Losses	(65,969,000)	(69,920,000)
Residential mortgage-backed securities | Assets/liabilities measured at fair value
Available-for-sale securities
Total Investment Securities	3,891,233,000	3,894,470,000
Residential mortgage-backed securities | Carrying Value
Available-for-sale securities
Total Investment Securities	3,891,233,000	3,894,470,000
Mortgage-backed securities by Ginnie Mae
Available-for-sale securities
Total Investment Securities	654,063,000	850,033,000
Mortgage-backed securities by Fannie Mae and Freddie Mac
Available-for-sale securities
Total Investment Securities	3,237,170,000	3,026,832
Mortgage-backed securities by non-government entities
Available-for-sale securities
Total Investment Securities		17,605,000
Obligations of states and political subdivisions
Available-for-sale securities
Amortized Cost	225,096,000	244,622,000
Gross Unrealized Gains	7,871,000	10,783,000
Gross Unrealized Losses	(16,000)	(433,000)
Obligations of states and political subdivisions | Assets/liabilities measured at fair value
Available-for-sale securities
Total Investment Securities	232,951,000	254,972,000
Obligations of states and political subdivisions | Carrying Value
Available-for-sale securities
Total Investment Securities	232,951,000	254,972,000
Other securities
Held-to-maturity securities
Amortized cost	2,400,000	2,400,000
Estimated fair value	2,400,000	2,400,000
Carrying Value	2,400,000	2,400,000
Equity securities
Available-for-sale securities
Amortized Cost	28,075,000	28,075,000
Gross Unrealized Gains	293,000	314,000
Gross Unrealized Losses	(482,000)	(482,000)
Equity securities | Assets/liabilities measured at fair value
Available-for-sale securities
Total Investment Securities	27,886,000	27,907,000
Equity securities | Carrying Value
Available-for-sale securities
Total Investment Securities	$ 27,886,000	$ 27,907,000

Investment Securities (Contract

Investment Securities (Contractual Maturities and Estimated Fair Values) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Held-to-maturity debt securities amortized cost disclosures
Due in one year or less, held-to-maturity debt securities amortized cost	$ 2,275,000
Due after one year through five years, held-to-maturity debt securities amortized cost	125,000
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	2,275,000
Due after one year through five years, held-to-maturity debt securities, Estimated fair value	125,000
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	1,939,000
Due after ten years, available-for-sale debt securities amortized cost	223,157,000
Residential mortgage-backed securities, amortized cost	3,943,092,000
Equity securities, amortized cost	28,075,000
Amortized cost, Available-for-sale securities	4,196,263,000	4,218,841,000
Available for sale debt securities, Estimated Fair Value Disclosures
Due after five years through ten years, available-for-sale debt securities, Estimated Fair Value	1,967,000
Due after ten years, available-for-sale debt securities, Estimated Fair Value	230,984,000
Residential mortgage-backed securities, Estimated Fair Value	3,891,233,000
Equity securities, Estimated Fair Value	27,886,000
Estimated fair value, Available for sale securities	4,152,070,000	4,177,349,000
Amortized cost of available for sale investment securities pledged	1,428,387,000
Fair value of available for sale investment securities pledged	1,403,084,000
Proceeds from sales and calls of available for sale securities	396,066,000	352,743,000	$ 164,163,000
Proceeds from sales of mortgage-backed securities	377,756,000	338,138,000	128,444,000
Gross gains realized on sales	1,186,000	586,000	2,450,000
Gross losses realized on sales	$ 5,960,000	$ 3,212,000	$ 6,132,000

Investment Securities (Fair Val

Investment Securities (Fair Value and Gross Unrealized Loss) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available for sale:
Fair value, less than 12 months	$ 1,078,610	$ 2,559,042
Unrealized losses, less than 12 Months	(13,417)	(52,862)
Fair value, 12 months or more	2,037,996	402,147
Unrealized losses, 12 Months or More	(53,050)	(17,973)
Fair value, total	3,116,606	2,961,189
Unrealized losses, total	(66,467)	(70,835)
Residential mortgage-backed securities
Available for sale:
Fair value, less than 12 months	1,061,577	2,513,872
Unrealized losses, less than 12 Months	(13,157)	(52,245)
Fair value, 12 months or more	2,029,455	396,695
Unrealized losses, 12 Months or More	(52,812)	(17,675)
Fair value, total	3,091,032	2,910,567
Unrealized losses, total	(65,969)	(69,920)
Obligations of states and political subdivisions
Available for sale:
Fair value, less than 12 months	5,534	31,104
Unrealized losses, less than 12 Months	(9)	(433)
Fair value, 12 months or more	522
Unrealized losses, 12 Months or More	(7)
Fair value, total	6,056	31,104
Unrealized losses, total	(16)	(433)
Equity securities
Available for sale:
Fair value, less than 12 months	11,499	14,066
Unrealized losses, less than 12 Months	(251)	(184)
Fair value, 12 months or more	8,019	5,452
Unrealized losses, 12 Months or More	(231)	(298)
Fair value, total	19,518	19,518
Unrealized losses, total	$ (482)	$ (482)

Investment Securities (Reconcil

Investment Securities (Reconciliation of Credit Related Impairment Charges ) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of credit-related impairment charges on investments recognized in earnings
Impairment charges on available for sale securities		$ 354,000	$ 954,000
Impairment charges on available-for-sale investment securities, after tax		230,100	6,201,000
Available-for-sale investments
Reconciliation of credit-related impairment charges on investments recognized in earnings
Balance at the beginning	$ 13,931,000	13,577,000	12,623,000
Sale of other-than-temporarily impaired available-for-sale securities during period	$ (13,931,000)
Impairment charges recognized during period		(354,000)	(954,000)
Balance at the end		$ 13,931,000	$ 13,577,000

Loans (Details)

Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Summary of loans, by loan type
Total loans	$ 6,348,172	$ 5,964,688
Commercial, financial and agricultural
Summary of loans, by loan type
Total loans	3,322,668	2,993,203
Real estate - mortgage
Summary of loans, by loan type
Total loans	1,133,525	1,032,222
Commercial Real Estate: Other Construction and Land Development
Summary of loans, by loan type
Total loans	1,683,550	1,716,875
Consumer
Summary of loans, by loan type
Total loans	49,543	55,168
Foreign
Summary of loans, by loan type
Total loans	$ 158,886	$ 167,220

Allowance for Probable Loan L62

Allowance for Probable Loan Losses (By Loan Class) (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)item	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Allowance for probable loan losses
Balance at the beginning of the period		$ 66,988	$ 64,661	$ 66,988	$ 64,828
Losses charged to allowance			(13,098)	(35,901)	(27,125)
Recoveries credited to allowance			4,903	13,715	4,880
Net losses charged to allowance			(8,195)	(22,186)	(22,245)
Provision (credit) charged to operations			11,221	19,859	24,405
Balance at the end of the period			$ 67,687	64,661	66,988
Period of time for determining the historical charge-off experience			3 years
Number of large recoveries | item			2
Watch - List Impaired
Allowance for probable loan losses
Losses charged to allowance			$ (19,400)
Commercial
Allowance for probable loan losses
Balance at the beginning of the period		21,431	25,649	21,431	22,352
Losses charged to allowance			(12,094)	(32,959)	(24,802)
Recoveries credited to allowance		4,400	4,020	7,110	3,135
Net losses charged to allowance			(8,074)	(25,849)	(21,667)
Provision (credit) charged to operations			10,330	30,067	20,746
Balance at the end of the period			27,905	25,649	21,431
Commercial | Transportation Equipment
Allowance for probable loan losses
Losses charged to allowance					(13,500)
Commercial Real Estate: Other Construction and Land Development
Allowance for probable loan losses
Balance at the beginning of the period		13,920	13,889	13,920	12,955
Losses charged to allowance			(213)	(16)	(695)
Recoveries credited to allowance	$ 6,000		21	6,099	141
Net losses charged to allowance			(192)	6,083	(554)
Provision (credit) charged to operations			(2,022)	(6,114)	1,519
Balance at the end of the period			11,675	13,889	13,920
Commercial Real Estate: Farmland & Commercial
Allowance for probable loan losses
Balance at the beginning of the period		19,769	16,731	19,769	18,683
Losses charged to allowance			(40)	(1,890)	(492)
Recoveries credited to allowance			527	119	963
Net losses charged to allowance			487	(1,771)	471
Provision (credit) charged to operations			(555)	(1,267)	615
Balance at the end of the period			16,663	16,731	19,769
Commercial Real Estate: Multifamily
Allowance for probable loan losses
Balance at the beginning of the period		1,248	806	1,248	846
Losses charged to allowance				(180)
Net losses charged to allowance				(180)
Provision (credit) charged to operations			303	(262)	402
Balance at the end of the period			1,109	806	1,248
Residential First Lien
Allowance for probable loan losses
Balance at the beginning of the period		3,509	2,455	3,509	3,589
Losses charged to allowance			(101)	(70)	(157)
Recoveries credited to allowance			11	21	30
Net losses charged to allowance			(90)	(49)	(127)
Provision (credit) charged to operations			585	(1,005)	47
Balance at the end of the period			2,950	2,455	3,509
Residential Junior Lien
Allowance for probable loan losses
Balance at the beginning of the period		5,321	3,716	5,321	4,683
Losses charged to allowance			(340)	(331)	(275)
Recoveries credited to allowance			258	278	431
Net losses charged to allowance			(82)	(53)	156
Provision (credit) charged to operations			2,469	(1,552)	482
Balance at the end of the period			6,103	3,716	5,321
Consumer
Allowance for probable loan losses
Balance at the beginning of the period		638	531	638	660
Losses charged to allowance			(309)	(414)	(704)
Recoveries credited to allowance			45	69	170
Net losses charged to allowance			(264)	(345)	(534)
Provision (credit) charged to operations			173	238	512
Balance at the end of the period			440	531	638
Foreign
Allowance for probable loan losses
Balance at the beginning of the period		$ 1,152	884	1,152	1,060
Losses charged to allowance			(1)	(41)
Recoveries credited to allowance			21	19	10
Net losses charged to allowance			20	(22)	10
Provision (credit) charged to operations			(62)	(246)	82
Balance at the end of the period			$ 842	$ 884	$ 1,152

Allowance for Probable Loan L63

Allowance for Probable Loan Losses (Impairment By Loan Class) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	$ 63,204	$ 48,405
Loans Individually Evaluated for Impairment, Allowance	434	961
Loans Collectively Evaluated for Impairment, Recorded Investment	6,284,968	5,916,283
Loans Collectively Evaluated for Impairment, Allowance	67,253	63,700
Commercial
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	17,947	22,412
Loans Individually Evaluated for Impairment, Allowance	300
Loans Collectively Evaluated for Impairment, Recorded Investment	1,068,520	887,255
Loans Collectively Evaluated for Impairment, Allowance	27,605	25,649
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	2,455	4,776
Loans Individually Evaluated for Impairment, Allowance	116	371
Loans Collectively Evaluated for Impairment, Recorded Investment	1,681,095	1,712,099
Loans Collectively Evaluated for Impairment, Allowance	11,559	13,518
Commercial Real Estate: Farmland & Commercial
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	33,123	10,810
Loans Individually Evaluated for Impairment, Allowance	18	546
Loans Collectively Evaluated for Impairment, Recorded Investment	2,010,162	1,932,260
Loans Collectively Evaluated for Impairment, Allowance	16,645	16,185
Commercial Real Estate: Multifamily
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	476	552
Loans Collectively Evaluated for Impairment, Recorded Investment	192,440	139,914
Loans Collectively Evaluated for Impairment, Allowance	1,109	806
Residential First Lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	6,852	6,836
Loans Individually Evaluated for Impairment, Allowance		44
Loans Collectively Evaluated for Impairment, Recorded Investment	425,925	415,068
Loans Collectively Evaluated for Impairment, Allowance	2,950	2,411
Residential Junior Lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	723	978
Loans Collectively Evaluated for Impairment, Recorded Investment	700,025	609,340
Loans Collectively Evaluated for Impairment, Allowance	6,103	3,716
Consumer
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	1,281	1,295
Loans Collectively Evaluated for Impairment, Recorded Investment	48,262	53,873
Loans Collectively Evaluated for Impairment, Allowance	440	531
Foreign
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	347	746
Loans Collectively Evaluated for Impairment, Recorded Investment	158,539	166,474
Loans Collectively Evaluated for Impairment, Allowance	$ 842	$ 884

Allowance for Probable Loan L64

Allowance for Probable Loan Losses (Non-accrual Basis By Loan Class) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loan loss allowances, financing receivable past due
Non-accrual loans, total	$ 54,730,000	$ 37,245,000	$ 47,685,000
Reduced interest income on non-accrual loans	977,000	2,461,000	$ 3,298,000
Commercial
Loan loss allowances, financing receivable past due
Non-accrual loans, total	17,909,000	22,369,000
Commercial Real Estate: Other Construction and Land Development
Loan loss allowances, financing receivable past due
Non-accrual loans, total	2,455,000	4,776,000
Commercial Real Estate: Farmland & Commercial
Loan loss allowances, financing receivable past due
Non-accrual loans, total	33,123,000	8,314,000
Commercial Real Estate: Multifamily
Loan loss allowances, financing receivable past due
Non-accrual loans, total	476,000	552,000
Residential First Lien
Loan loss allowances, financing receivable past due
Non-accrual loans, total	712,000	655,000
Residential Junior Lien
Loan loss allowances, financing receivable past due
Non-accrual loans, total	11,000	166,000
Consumer
Loan loss allowances, financing receivable past due
Non-accrual loans, total	$ 44,000	26,000
Foreign
Loan loss allowances, financing receivable past due
Non-accrual loans, total		$ 387,000

Allowance for Probable Loan L65

Allowance for Probable Loan Losses (Impaired Loans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Interest Recognized
Total trouble debt restructuring	$ 15,346	$ 22,418
Period of charge off for past due unsecured commercial loans	90 days
Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	$ 1,894	4,828
Total impaired loans with no related allowance	61,310	42,577
Unpaid principal balance:
Total impaired loans with an allowance recorded	2,336	5,981
Total impaired loans with no related allowance recorded	89,664	74,677
Related Allowance	434	961
Average recorded investment:
Total impaired loans with an allowance recorded	1,985	9,579
Total impaired loans with no related allowance recorded	72,417	40,450
Interest Recognized
Total impaired loans with no related allowance recorded	391	547
Commercial
Interest Recognized
Total trouble debt restructuring	6,910	10,710
Commercial | Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	1,300
Total impaired loans with no related allowance	16,646	21,412
Unpaid principal balance:
Total impaired loans with an allowance recorded	1,577
Total impaired loans with no related allowance recorded	44,095	50,737
Related Allowance	300
Average recorded investment:
Total impaired loans with an allowance recorded	1,346
Total impaired loans with no related allowance recorded	19,615	19,354
Interest Recognized
Total impaired loans with no related allowance recorded	3	3
Commercial Real Estate: Other Construction and Land Development | Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	145	1,958
Total impaired loans with no related allowance	2,310	2,818
Unpaid principal balance:
Total impaired loans with an allowance recorded	169	1,971
Total impaired loans with no related allowance recorded	2,455	4,419
Related Allowance	116	371
Average recorded investment:
Total impaired loans with an allowance recorded	150	2,512
Total impaired loans with no related allowance recorded	3,493	2,336
Interest Recognized
Total impaired loans with no related allowance recorded		67
Commercial Real Estate: Farmland & Commercial
Interest Recognized
Total trouble debt restructuring		3,086
Commercial Real Estate: Farmland & Commercial | Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance	449	2,808
Total impaired loans with no related allowance	32,675	8,002
Unpaid principal balance:
Total impaired loans with an allowance recorded	590	3,948
Total impaired loans with no related allowance recorded	33,275	9,054
Related Allowance	18	546
Average recorded investment:
Total impaired loans with an allowance recorded	489	3,247
Total impaired loans with no related allowance recorded	38,536	8,523
Interest Recognized
Total impaired loans with no related allowance recorded		110
Commercial Real Estate: Multifamily | Class of Financing Receivable
Recorded investment:
Total impaired loans with related allowance		62
Total impaired loans with no related allowance	476	552
Unpaid principal balance:
Total impaired loans with an allowance recorded		62
Total impaired loans with no related allowance recorded	505	562
Related Allowance		44
Average recorded investment:
Total impaired loans with an allowance recorded		62
Total impaired loans with no related allowance recorded	511	401
Residential First Lien
Interest Recognized
Total trouble debt restructuring	6,140	6,181
Residential First Lien | Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	6,852	6,774
Unpaid principal balance:
Total impaired loans with no related allowance recorded	6,968	6,847
Average recorded investment:
Total impaired loans with no related allowance recorded	7,249	6,860
Interest Recognized
Total impaired loans with no related allowance recorded	324	298
Residential Junior Lien
Interest Recognized
Total trouble debt restructuring	712	812
Residential Junior Lien | Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	723	978
Unpaid principal balance:
Total impaired loans with no related allowance recorded	736	1,017
Average recorded investment:
Total impaired loans with no related allowance recorded	970	1,011
Interest Recognized
Total impaired loans with no related allowance recorded	45	52
Consumer
Interest Recognized
Total trouble debt restructuring	1,237	1,269
Consumer | Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	1,281	1,295
Unpaid principal balance:
Total impaired loans with no related allowance recorded	1,283	1,295
Average recorded investment:
Total impaired loans with no related allowance recorded	1,293	1,214
Interest Recognized
Total impaired loans with no related allowance recorded	3	1
Foreign
Interest Recognized
Total trouble debt restructuring	347	360
Foreign | Class of Financing Receivable
Recorded investment:
Total impaired loans with no related allowance	347	746
Unpaid principal balance:
Total impaired loans with no related allowance recorded	347	746
Average recorded investment:
Total impaired loans with no related allowance recorded	750	751
Interest Recognized
Total impaired loans with no related allowance recorded	$ 16	$ 16

Allowance for Probable Loan L66

Allowance for Probable Loan Losses (Aging By Loan Class) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing receivable recorded investment
Past due	$ 77,053,000	$ 61,400,000
Past due 90 days or Greater and Still Accruing	7,257,000	5,226,000	$ 11,616,000
Loans, current	6,271,119,000	5,903,288,000
Total loans	6,348,172,000	5,964,688,000
30 to 59 Days
Financing receivable recorded investment
Past due	15,855,000	17,299,000
60 to 89 Days
Financing receivable recorded investment
Past due	4,429,000	6,327,000
90 Days or Greater
Financing receivable recorded investment
Past due	56,769,000	37,774,000
Commercial
Financing receivable recorded investment
Past due	22,496,000	26,033,000
Past due 90 days or Greater and Still Accruing	537,000	392,000
Loans, current	1,063,971,000	883,634,000
Total loans	1,086,467,000	909,667,000
Commercial | 30 to 59 Days
Financing receivable recorded investment
Past due	3,790,000	4,081,000
Commercial | 60 to 89 Days
Financing receivable recorded investment
Past due	398,000	829,000
Commercial | 90 Days or Greater
Financing receivable recorded investment
Past due	18,308,000	21,123,000
Commercial Real Estate: Other Construction and Land Development
Financing receivable recorded investment
Past due	1,482,000	6,354,000
Past due 90 days or Greater and Still Accruing	6,000	9,000
Loans, current	1,682,068,000	1,710,521,000
Total loans	1,683,550,000	1,716,875,000
Commercial Real Estate: Other Construction and Land Development | 30 to 59 Days
Financing receivable recorded investment
Past due	354,000	1,502,000
Commercial Real Estate: Other Construction and Land Development | 60 to 89 Days
Financing receivable recorded investment
Past due	308,000	396,000
Commercial Real Estate: Other Construction and Land Development | 90 Days or Greater
Financing receivable recorded investment
Past due	820,000	4,456,000
Commercial Real Estate: Farmland & Commercial
Financing receivable recorded investment
Past due	35,576,000	12,658,000
Past due 90 days or Greater and Still Accruing	954,000	289,000
Loans, current	2,007,709,000	1,930,412,000
Total loans	2,043,285,000	1,943,070,000
Commercial Real Estate: Farmland & Commercial | 30 to 59 Days
Financing receivable recorded investment
Past due	3,925,000	3,454,000
Commercial Real Estate: Farmland & Commercial | 60 to 89 Days
Financing receivable recorded investment
Past due	518,000	3,054,000
Commercial Real Estate: Farmland & Commercial | 90 Days or Greater
Financing receivable recorded investment
Past due	31,133,000	6,150,000
Commercial Real Estate: Multifamily
Financing receivable recorded investment
Past due	560,000	596,000
Loans, current	192,356,000	139,870,000
Total loans	192,916,000	140,466,000
Commercial Real Estate: Multifamily | 30 to 59 Days
Financing receivable recorded investment
Past due	84,000	44,000
Commercial Real Estate: Multifamily | 90 Days or Greater
Financing receivable recorded investment
Past due	476,000	552,000
Residential First Lien
Financing receivable recorded investment
Past due	10,848,000	11,108,000
Past due 90 days or Greater and Still Accruing	3,861,000	3,756,000
Loans, current	421,929,000	410,796,000
Total loans	432,777,000	421,904,000
Residential First Lien | 30 to 59 Days
Financing receivable recorded investment
Past due	4,295,000	5,615,000
Residential First Lien | 60 to 89 Days
Financing receivable recorded investment
Past due	2,458,000	1,350,000
Residential First Lien | 90 Days or Greater
Financing receivable recorded investment
Past due	4,095,000	4,143,000
Residential Junior Lien
Financing receivable recorded investment
Past due	3,000,000	1,480,000
Past due 90 days or Greater and Still Accruing	1,099,000	382,000
Loans, current	697,748,000	608,838,000
Total loans	700,748,000	610,318,000
Residential Junior Lien | 30 to 59 Days
Financing receivable recorded investment
Past due	1,310,000	762,000
Residential Junior Lien | 60 to 89 Days
Financing receivable recorded investment
Past due	580,000	178,000
Residential Junior Lien | 90 Days or Greater
Financing receivable recorded investment
Past due	1,110,000	540,000
Consumer
Financing receivable recorded investment
Past due	1,126,000	1,418,000
Past due 90 days or Greater and Still Accruing	133,000	387,000
Loans, current	48,417,000	53,750,000
Total loans	49,543,000	55,168,000
Consumer | 30 to 59 Days
Financing receivable recorded investment
Past due	868,000	910,000
Consumer | 60 to 89 Days
Financing receivable recorded investment
Past due	98,000	95,000
Consumer | 90 Days or Greater
Financing receivable recorded investment
Past due	160,000	413,000
Foreign
Financing receivable recorded investment
Past due	1,965,000	1,753,000
Past due 90 days or Greater and Still Accruing	667,000	11,000
Loans, current	156,921,000	165,467,000
Total loans	158,886,000	167,220,000
Foreign | 30 to 59 Days
Financing receivable recorded investment
Past due	1,229,000	931,000
Foreign | 60 to 89 Days
Financing receivable recorded investment
Past due	69,000	425,000
Foreign | 90 Days or Greater
Financing receivable recorded investment
Past due	$ 667,000	$ 397,000

Allowance for Probable Loan L67

Allowance for Probable Loan Losses (Portfolio Credit Quality By Loan Class) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)item	Dec. 31, 2016USD ($)
Loan portfolio by credit quality indicator
Portfolio, total	$ 6,348,172	$ 5,964,688
Number of additional relationships reclassified from Pass to Watch List - Substandard | item	3
Pass
Loan portfolio by credit quality indicator
Portfolio, total	$ 5,911,001	5,544,614
Special Review
Loan portfolio by credit quality indicator
Portfolio, total	6,612	101,679
Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	45,662	60,993
Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	321,693	208,997
Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	63,204	48,405
Commercial
Loan portfolio by credit quality indicator
Portfolio, total	1,086,467	909,667
Commercial | Pass
Loan portfolio by credit quality indicator
Portfolio, total	905,707	720,350
Commercial | Special Review
Loan portfolio by credit quality indicator
Portfolio, total		90,746
Commercial | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	3,170	1,121
Commercial | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	159,643	75,038
Commercial | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	17,947	22,412
Commercial Real Estate: Other Construction and Land Development
Loan portfolio by credit quality indicator
Portfolio, total	1,683,550	1,716,875
Commercial Real Estate: Other Construction and Land Development | Pass
Loan portfolio by credit quality indicator
Portfolio, total	1,616,604	1,648,633
Commercial Real Estate: Other Construction and Land Development | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	1,288	1,986
Commercial Real Estate: Other Construction and Land Development | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	672
Commercial Real Estate: Other Construction and Land Development | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	62,531	61,480
Commercial Real Estate: Other Construction and Land Development | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	2,455	4,776
Commercial Real Estate: Farmland & Commercial
Loan portfolio by credit quality indicator
Portfolio, total	2,043,285	1,943,070
Commercial Real Estate: Farmland & Commercial | Pass
Loan portfolio by credit quality indicator
Portfolio, total	1,863,763	1,792,542
Commercial Real Estate: Farmland & Commercial | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	5,134	7,983
Commercial Real Estate: Farmland & Commercial | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	41,820	59,872
Commercial Real Estate: Farmland & Commercial | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	99,445	71,863
Commercial Real Estate: Farmland & Commercial | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	33,123	10,810
Commercial Real Estate: Multifamily
Loan portfolio by credit quality indicator
Portfolio, total	192,916	140,466
Commercial Real Estate: Multifamily | Pass
Loan portfolio by credit quality indicator
Portfolio, total	192,440	139,914
Commercial Real Estate: Multifamily | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	476	552
Residential First Lien
Loan portfolio by credit quality indicator
Portfolio, total	432,777	421,904
Residential First Lien | Pass
Loan portfolio by credit quality indicator
Portfolio, total	425,811	413,638
Residential First Lien | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	40	814
Residential First Lien | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	74	616
Residential First Lien | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	6,852	6,836
Residential Junior Lien
Loan portfolio by credit quality indicator
Portfolio, total	700,748	610,318
Residential Junior Lien | Pass
Loan portfolio by credit quality indicator
Portfolio, total	699,875	609,190
Residential Junior Lien | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	150	150
Residential Junior Lien | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	723	978
Consumer
Loan portfolio by credit quality indicator
Portfolio, total	49,543	55,168
Consumer | Pass
Loan portfolio by credit quality indicator
Portfolio, total	48,262	53,873
Consumer | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	1,281	1,295
Foreign
Loan portfolio by credit quality indicator
Portfolio, total	158,886	167,220
Foreign | Pass
Loan portfolio by credit quality indicator
Portfolio, total	158,539	166,474
Foreign | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	$ 347	$ 746

Bank Premises and Equipment (De

Bank Premises and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Bank premises and equipment
Less: accumulated depreciation	$ (448,470)	$ (420,279)
Bank premises and equipment, net	514,454	527,583
Bank Building and Improvements
Bank premises and equipment
Bank premises and equipment, gross	$ 550,094	542,063
Bank Building and Improvements | Minimum
Bank premises and equipment
Estimated useful lives	5 years
Bank Building 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	$ 289,743	280,586
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	$ 123,087	$ 125,213
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 Intangible69

Goodwill and Other Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Identified intangible assets
Carrying Amount	$ 60,697	$ 60,697
Accumulated Amortization	60,697	60,672
Total identified intangibles, Net		25
Amortization expense	25	128	$ 644
Changes in carrying amount of goodwill	0	0
Core deposit premium
Identified intangible assets
Carrying Amount	58,675	58,675
Accumulated Amortization	58,675	58,650
Total identified intangibles, Net		25
Identified intangible (contract rights)
Identified intangible assets
Carrying Amount	2,022	2,022
Accumulated Amortization	$ 2,022	$ 2,022

Deposits (Details)

Deposits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Demand non-interest bearing
Domestic	$ 2,609,932	$ 2,509,544
Foreign	633,323	648,507
Total demand non-interest bearing	3,243,255	3,158,051
Savings and interest bearing demand
Domestic	2,615,143	2,589,675
Foreign	629,988	614,053
Total savings and interest bearing demand	3,245,131	3,203,728
$100,000 or more
Time, certificate of deposit	1,445,887
Less than $100,000
Domestic	354,998	389,682
Foreign	255,621	272,363
Total time, certificates of deposit	2,056,506	2,248,310
Total deposits	8,544,892	8,610,089
Savings and interest bearing demand
Domestic	5,453	3,922	$ 3,026
Foreign	755	640	567
Total savings and interest bearing demand	6,208	4,562	3,593
$100,000 or more
Domestic	3,644	3,881	4,693
Foreign	4,105	3,929	4,116
Less than $100,000
Domestic	1,312	1,447	1,680
Foreign	675	706	744
Total time, certificates of deposit	9,736	9,963	11,233
Total interest expense on deposits	15,944	14,525	$ 14,826
Domestic
$100,000 or more
Time, certificate of deposit	637,006	748,104
Foreign
$100,000 or more
Time, certificate of deposit	$ 808,881	$ 838,161

Deposits (Scheduled Maturities)

Deposits (Scheduled Maturities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Scheduled maturities of time deposits
2,018	$ 1,859,507
2,019	139,276
2,020	41,572
2,021	13,303
2,022	2,760
Thereafter	88
Total time, certificates of deposit	2,056,506	$ 2,248,310
Time Deposits 250,000 or exceed	894,000	$ 1,005,000
Scheduled maturities of time deposits in amounts of $100,000 or more
Due within 3 months or less	557,206
Due after 3 months and within 6 months	348,695
Due after 6 months and within 12 months	404,776
Due after 12 months	135,210
Total	$ 1,445,887

Securities Sold Under Repurch72

Securities Sold Under Repurchase Agreements (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Collateral Securities and Repurchase Borrowing agreements
Average outstanding amount	$ 402,396,000	$ 759,458,000
Maximum amount outstanding at any month end	514,616,000	819,155,000
Collateralized Securities, Book Value of Securities Sold	460,681,000	690,151,000
Collateralized securities, Fair Value of Securities Sold	452,912,000	679,811,000
Repurchase Borrowing, Balance of Liability	$ 353,805,000	$ 504,985,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	1.32%	2.46%
Overnight agreements
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold	$ 340,054,000	$ 295,282,000
Collateralized securities, Fair Value of Securities Sold	334,506,000	292,286,000
Repurchase Borrowing, Balance of Liability	$ 242,824,000	$ 190,915,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	0.25%	0.15%
1 to 29 days
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold		$ 10,250,000
Collateralized securities, Fair Value of Securities Sold		10,148,000
Repurchase Borrowing, Balance of Liability		$ 9,863,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)		0.50%
30 to 90 days
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold	$ 109,300,000	$ 2,315,000
Collateralized securities, Fair Value of Securities Sold	107,238,000	2,317,000
Repurchase Borrowing, Balance of Liability	$ 100,000,000	$ 2,300,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	3.99%	0.33%
Over 90 days
Collateral Securities and Repurchase Borrowing agreements
Collateralized Securities, Book Value of Securities Sold	$ 11,327,000	$ 382,304,000
Collateralized securities, Fair Value of Securities Sold	11,168,000	375,060,000
Repurchase Borrowing, Balance of Liability	$ 10,981,000	$ 301,907,000
Repurchase Borrowing, Weighted Average Interest Rate (as a percent)	0.74%	4.01%

Other Borrowed Funds (Details)

Other Borrowed Funds (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Federal Home Loan Bank advances
Other borrowed funds	$ 1,195,225,000	$ 733,375,000
Federal home loan bank advances maturing November 2027
Federal Home Loan Bank advances
Other borrowed funds	100,000,000
Federal home loan Bank advances maturing December 20207
Federal Home Loan Bank advances
Other borrowed funds	150,000,000
Federal Home Loan Bank advances - short-term
Federal Home Loan Bank advances
Other borrowed funds	$ 945,225,000	$ 583,375,000
Rate on balance outstanding at year end (as a percent)	1.44%	0.66%
Average daily balance	$ 839,858,000	$ 483,379,000
Average rate (as a percent)	1.23%	0.47%
Maximum amount outstanding at any month end	$ 1,043,250,000	$ 600,875,000
Federal Home Loan Bank advances - long-term
Federal Home Loan Bank advances
Other borrowed funds	$ 250,000,000	$ 150,000,000
Rate on balance outstanding at year end (as a percent)	1.26%	0.58%
Average daily balance	$ 51,644,000	$ 150,000,000
Average rate (as a percent)	1.26%	0.58%
Maximum amount outstanding at any month end	$ 250,000,000	$ 150,000,000

Junior Subordinated Deferrabl74

Junior Subordinated Deferrable Interest Debentures (Details)	Nov. 01, 2016USD ($)	Jul. 29, 2015USD ($)	Dec. 31, 2017USD ($)item	Dec. 31, 2016USD ($)
Junior subordinated deferrable interest debentures, major types of business trusts
Number of statutory business trusts issuing trust preferred securities | item			6
Junior subordinated deferrable interest debentures			$ 160,416,000	$ 160,416,000
Maximum number of consecutive quarterly period available for deferral of interest payment on Trusts VI, VIII, IX, X, XI and XII | item			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			$ 160,416,000	$ 160,416,000
Trust XI
Junior subordinated deferrable interest debentures, major types of business trusts
Redemption price discount (as a percent)	24.00%
Retirement of capital securities	$ 1,000,000	$ 1,000,000
Junior subordinated deferrable interest debentures	$ 26,990,000	$ 27,990,000	25,990,000
Trust X and XI
Junior subordinated deferrable interest debentures, major types of business trusts
Redemption price discount (as a percent)		24.50%
Trust X
Junior subordinated deferrable interest debentures, major types of business trusts
Retirement of capital securities		$ 13,000,000
Junior subordinated deferrable interest debentures		$ 34,021,000	$ 21,021,000

Junior Subordinated Deferrabl75

Junior Subordinated Deferrable Interest Debentures (Key Information) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Nov. 01, 2016	Jul. 29, 2015
Junior subordinated deferrable interest debentures, major types of business trusts
Junior subordinated deferrable interest debentures	$ 160,416,000	$ 160,416,000
Trust VI
Junior subordinated deferrable interest debentures, major types of business trusts
Junior subordinated deferrable interest debentures	$ 25,774,000
Interest rate (as a percent)	4.87%
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	$ 25,774,000
Interest rate (as a percent)	4.41%
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	$ 41,238,000
Interest rate (as a percent)	2.96%
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	$ 21,021,000			$ 34,021,000
Interest rate (as a percent)	3.03%
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	$ 25,990,000		$ 26,990,000	$ 27,990,000
Interest rate (as a percent)	2.96%
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	$ 20,619,000
Interest rate (as a percent)	2.93%
Interest rate index	LIBOR
Spread on interest rate index (as a percent)	1.45%

Earnings per Share ("EPS") (Det

Earnings per Share ("EPS") (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic EPS
Net income	$ 157,436	$ 133,932	$ 136,726
Shares (Denominator)	66,046,155	65,967,989	66,411,193
Per Share Amount	$ 2.38	$ 2.03	$ 2.06
Diluted EPS
Net Income	$ 157,436	$ 133,932	$ 136,726
Potential dilutive common shares and warrants	732,281	345,501	225,160
Shares (Denominator)	66,778,436	66,313,490	66,636,353
Per Share Amount (in dollars per share)	$ 2.36	$ 2.02	$ 2.05

Employees' Profit Sharing Plan

Employees' Profit Sharing Plan (Details) - Deferred profit sharing plan - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employees' profit sharing plan
Minimum period of continuous employment to be fully vested	1 year
Profit sharing costs	$ 3,750,000	$ 3,650,000	$ 3,525,000

International Operations (Detai

International Operations (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans:
Loans	$ 6,348,172,000	$ 5,964,688,000
Less allowance for probable loan losses	(67,687,000)	(64,661,000)	$ (66,988,000)	$ (64,828,000)
Net loans	6,280,485,000	5,900,027,000
Accrued interest receivable	34,456,000	32,172,000
International Banking Services
Loans:
Accrued interest receivable	671,000	603,000
Outstanding standby and commercial letters of credit	99,547,000
Revenues	5,248,000	5,495,000	$ 6,113,000
International Banking Services | Foreign
Loans:
Loans	158,886,000	167,220,000
Less allowance for probable loan losses	(842,000)	(884,000)
Net loans	158,044,000	166,336,000
International Banking Services | Foreign | Commercial
Loans:
Loans	113,019,000	124,079,000
International Banking Services | Foreign | Others
Loans:
Loans	$ 45,867,000	$ 43,141,000

Income Taxes (Current and Defer

Income Taxes (Current and Deferred Portions of Net Income Tax Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
U.S.	$ 56,974	$ 52,403	$ 65,196
State	2,662	3,362	5,258
Foreign			(6)
Total current taxes	59,636	55,765	70,448
Deferred
U.S.	4,620	7,279	(261)
State	(50)	27	(71)
Total deferred taxes	4,570	7,306	(332)
Total income taxes	$ 64,206	$ 63,071	$ 70,116

Income Taxes (Income Tax Expens

Income Taxes (Income Tax Expense Differences from the Amount Computed by Applying the U.S. Federal Income Tax Rate) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes
U.S. Federal income tax rate (as a percent)	35.00%	35.00%	35.00%
Reasons for the difference of income tax expense
Computed expected tax expense	$ 77,643	$ 69,253	$ 72,389
Change in taxes resulting from:
Tax-exempt interest income	(4,701)	(3,940)	(3,910)
State tax, net of federal income taxes and tax credit and refunds	1,697	3,287	3,371
Resolution of IRS exam	(4,985)
Other investment income	(3,198)	(3,694)	(3,540)
Deferred tax adjustment due to federal tax rate change	(3,168)
Other	918	(1,835)	1,806
Total income taxes	$ 64,206	$ 63,071	$ 70,116

Income Taxes (Deferred Tax Asse

Income Taxes (Deferred Tax Assets and Deferred Tax Liabilities) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Loans receivable, principally due to the allowance for probable loan losses		$ 14,546,000	$ 24,315,000
Other real estate owned		2,053,000	3,652,000
Impairment charges on available-for-sale securities		844,000	6,086,000
Accrued expenses		81,000	137,000
Net unrealized losses on available for sale investment securities		9,680,000	14,791,000
Other		4,434,000	6,917,000
Total deferred tax assets		31,638,000	55,898,000
Deferred tax liabilities:
Bank premises and equipment, principally due to differences on depreciation		(10,940,000)	(19,837,000)
Identified intangible assets and goodwill		(13,417,000)	(21,386,000)
Other		(12,474,000)	(16,300,000)
Total deferred tax liabilities		36,831,000	57,523,000
Net deferred tax liability		(5,193,000)	$ (1,625,000)
Income tax refund		$ 4,900,000
U.S. Federal income tax rate (as a percent)		35.00%	35.00%	35.00%
Net benefit due to change in tax rate		$ 3,168,000
Forecast
Deferred tax liabilities:
U.S. Federal income tax rate (as a percent)	21.00%

Stock Options (Details)

Stock Options (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Apr. 05, 2012
Stock options under 2012 Plan
Stock option details
Shares available for future grants	216,400			800,000
Maximum exercisable period for options granted	10 years
Black-Scholes-Merton option valuation model assumptions
Expected Life (Years)		7 years 7 months 10 days
Dividend yield (as a percent)		2.50%
Interest rate (as a percent)		1.50%
Volatility (as a percent)		41.32%
Stock option activity
Options outstanding at the beginning of the period (in shares)	800,502
Less:
Options exercised (in shares)	108,885
Options expired (in shares)	2,188
Options forfeited (in shares)	21,263
Options outstanding at the end of the period (in shares)	668,166	800,502
Options fully vested and exercisable at the end of the period (in shares)	283,472
Stock Options, Weighted average exercise price
Options outstanding at the beginning, weighted average exercise price (in dollars per share)	$ 19.43
Less:
Options exercised, weighted average exercise price (in dollars per share)	13.34
Options expired, weighted average exercise price (in dollars per share)	10.40
Options forfeited, weighted average exercise price (in dollars per share)	20.62
Options outstanding at the end, weighted average exercise price (in dollars per share)	20.41	$ 19.43
Options fully vested and exercisable at the end, weighted average exercise price (in dollars per share)	$ 18.62
Stock Options, Weighted average remaining contractual term (years)
Options outstanding at the end, weighted average remaining contractual term (years)	5 years 6 months 15 days
Options fully vested and exercisable at the end, weighted average remaining contractual term (years)	4 years 5 months 16 days
Stock Options, Aggregate intrinsic value
Options outstanding at the end, aggregate intrinsic value	$ 12,887,000
Options fully vested and exercisable at the end, aggregate intrinsic value	5,975,000
Stock-based compensation expense	903,000	$ 1,082,000	$ 1,172,000
Stock-based compensation cost, unrecognized, related to non-vested options	$ 1,418,000
Stock-based compensation cost, unrecognized, related to non-vested options, weighted-average period of recognition	1 year 4 months 24 days
Other information pertaining to option activity
Weighted average grant date fair value of stock options granted (in dollars per share)		$ 8.74	$ 9.42
Total fair value of stock options vested	$ 1,182,000	$ 1,015,000	$ 872,000
Total intrinsic value of stock options exercised	$ 2,595,000	$ 792,000	$ 781,000
Incentive stock options granted to 10% shareholders
Stock option details
Maximum exercisable period for options granted	5 years

Long Term Restricted Stock Un83

Long Term Restricted Stock Units (Details) - Plan - RSUs	1 Months Ended	12 Months Ended
	Dec. 31, 2009item	Dec. 31, 2017shares
Long-Term Restricted Stock Units
Minimum number of non-employee members of the Board needed to authorize restricted stock units | item	2
Number of options granted (in shares)		0
Outstanding grants (in shares)		0

Commitments and Contingent Liab

Commitments and Contingent Liabilities and Other Matters (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments, Contingent Liabilities and Other Matters
Total rental expense	$ 5,258,000	$ 5,870,000	$ 6,200,000
Minimum period for non-cancellable sub-leases	1 year
Aggregate future minimum rentals to be received under non-cancellable sub-leases	$ 92,416,000
Approximate cash maintained to satisfy regulatory reserve requirements	116,129,000	$ 111,353,000
Future minimum lease payments due under non-cancellable operating leases
2,018	3,563,000
2,019	3,376,000
2,020	3,087,000
2,021	2,037,000
2,022	494,000
Thereafter	180,000
Total	$ 12,737,000

Transactions with Related Par85

Transactions with Related Parties (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Transactions with Related Parties
Aggregate amount receivable from related parties	$ 27,626,000	$ 26,547,000

Financial Instruments with Of86

Financial Instruments with Off-Statement of Condition Risk and Concentrations of Credit Risk (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
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	$ 2,795,137,000
Credit card lines
Financial amounts of instruments, whose contract amounts represent credit risks
Outstanding amount of financial instruments whose, contract amounts represent credit risks	20,643,000
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	95,402,000
Guarantee obligations, maximum exposure	95,402,000
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	4,145,000
Unsecured letters of credit
Financial amounts of instruments, whose contract amounts represent credit risks
Unsecured letters of credit	$ 35,409,000	$ 40,738,000

Capital Requirements (Details)

Capital Requirements (Details) - USD ($)	Dec. 23, 2008	Dec. 31, 2017
Capital Requirements
Warrants to purchase entity's common stock (in shares)	1,326,238
Warrants, exercise price (in dollars per share)	$ 24.43	$ 24.43
Maximum cash dividend paid in semi-annual period (in dollars per share)		$ 0.33
Warrants, term	10 years
Dividend payable by subsidiaries, maximum		$ 731,850,000

Capital Requirements (Changes)

Capital Requirements (Changes) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Jan. 01, 2016	Jul. 31, 2013
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	2.50%		0.625%
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent)				6.00%
Term of mandatory compliance	4 years
Minimum
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	4.50%
CET 1 ratio		7.00%
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent)				4.00%

Capital Requirements (Capital A

Capital Requirements (Capital Amounts and Ratios) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2016	Dec. 31, 2015	Jul. 31, 2013
Capital Requirements
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)			0.625%	2.50%
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent)					6.00%
Minimum
Capital Requirements
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)				4.50%
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent)					4.00%
Parent Company
Capital Requirements
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Amount	$ 1,584,665	$ 1,468,662
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	17.11%	16.95%
Total Capital (to Risk Weighted Assets), Actual Amount	$ 1,807,107	$ 1,687,501
Tier 1 Capital (to Risk Weighted Assets), Actual Amount	1,734,595	1,618,935
Tier 1 Capital (to Average Assets), Actual Amount	$ 1,734,595	$ 1,618,935
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	19.51%	19.47%
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent)	18.73%	18.68%
Tier 1 capital (to Average Assets), Actual Ratio (as a percent)	14.62%	13.91%
Parent Company | Minimum
Capital Requirements
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	$ 532,579	$ 444,190
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	5.75%	5.125%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	$ 856,757	$ 747,540
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	671,512	574,197
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount	$ 474,675	$ 465,438
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	9.25%	8.625%
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	7.25%	6.625%
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
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Amount	$ 1,119,173	$ 1,201,527
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	17.10%	16.63%
Total Capital (to Risk Weighted Assets), Actual Amount	$ 1,173,068	$ 1,260,886
Tier 1 Capital (to Risk Weighted Assets), Actual Amount	1,119,173	1,201,527
Tier 1 Capital (to Average Assets), Actual Amount	$ 1,119,173	$ 1,201,527
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	17.93%	17.45%
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent)	17.10%	16.63%
Tier 1 capital (to Average Assets), Actual Ratio (as a percent)	13.44%	12.50%
International Bank of Commerce, Laredo | Minimum
Capital Requirements
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	$ 376,245	$ 370,342
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 425,320	$ 469,701
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	5.75%	5.125%
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	6.50%	6.50%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	$ 605,263	$ 623,258
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	654,339	722,618
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	474,395	478,734
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	523,471	578,094
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount	333,166	384,342
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 416,458	$ 480,427
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	9.25%	8.625%
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)	7.25%	6.625%
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	8.00%	8.00%
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 Oklahoma
Capital Requirements
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Amount	$ 169,279
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	13.41%
Total Capital (to Risk Weighted Assets), Actual Amount	$ 178,057
Tier 1 Capital (to Risk Weighted Assets), Actual Amount	169,279
Tier 1 Capital (to Average Assets), Actual Amount	$ 169,279
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	14.11%
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent)	13.41%
Tier 1 capital (to Average Assets), Actual Ratio (as a percent)	11.31%
International Bank Of Commerce Oklahoma | Minimum
Capital Requirements
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	$ 72,586
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 82,054
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	5.75%
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	6.50%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	$ 116,769
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	126,237
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	91,521
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	100,989
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount	59,854
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 74,818
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	9.25%
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	10.00%
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	7.25%
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	8.00%
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent)	4.00%
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	5.00%
International Bank of Commerce, Brownsville
Capital Requirements
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Amount	$ 165,034	$ 158,533
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	25.94%	25.61%
Total Capital (to Risk Weighted Assets), Actual Amount	$ 170,613	$ 163,937
Tier 1 Capital (to Risk Weighted Assets), Actual Amount	165,034	158,533
Tier 1 Capital (to Average Assets), Actual Amount	$ 165,034	$ 158,533
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	26.82%	26.49%
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent)	25.94%	25.61%
Tier 1 capital (to Average Assets), Actual Ratio (as a percent)	17.17%	16.91%
International Bank of Commerce, Brownsville | Minimum
Capital Requirements
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	$ 36,583	$ 31,720
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 41,355	$ 40,230
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	5.75%	5.125%
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	6.50%	6.50%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	$ 58,851	$ 53,382
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	63,623	61,892
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	46,127	41,004
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	50,899	49,514
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount	38,440	37,509
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 48,050	$ 46,886
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	9.25%	8.625%
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)	7.25%	6.625%
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	8.00%	8.00%
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
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Amount	$ 66,406	$ 65,989
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	30.58%	34.09%
Total Capital (to Risk Weighted Assets), Actual Amount	$ 68,718	$ 67,464
Tier 1 Capital (to Risk Weighted Assets), Actual Amount	66,406	65,989
Tier 1 Capital (to Average Assets), Actual Amount	$ 66,406	$ 65,989
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	31.64%	34.85%
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent)	30.58%	34.09%
Tier 1 capital (to Average Assets), Actual Ratio (as a percent)	14.20%	13.87%
International Bank of Commerce, Zapata | Minimum
Capital Requirements
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	$ 12,487	$ 9,922
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 14,116	$ 12,584
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	5.75%	5.125%
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	6.50%	6.50%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	$ 20,088	$ 16,698
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	21,717	19,360
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	15,745	12,826
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	17,374	15,488
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount	18,701	19,029
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 23,376	$ 23,786
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	9.25%	8.625%
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)	7.25%	6.625%
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	8.00%	8.00%
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
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Amount	$ 79,330	$ 73,765
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	33.22%	31.84%
Total Capital (to Risk Weighted Assets), Actual Amount	$ 81,278	$ 76,093
Tier 1 Capital (to Risk Weighted Assets), Actual Amount	79,330	73,765
Tier 1 Capital (to Average Assets), Actual Amount	$ 79,330	$ 73,765
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent)	34.03%	32.85%
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent)	33.22%	31.84%
Tier 1 capital (to Average Assets), Actual Ratio (as a percent)	14.56%	13.05%
Commerce Bank | Minimum
Capital Requirements
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	$ 13,733	$ 11,872
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 15,524	$ 15,058
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	5.75%	5.125%
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	6.50%	6.50%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	$ 22,092	$ 19,980
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	23,884	23,166
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount	17,316	15,347
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	19,107	18,532
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount	21,789	22,607
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 27,236	$ 28,259
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent)	9.25%	8.625%
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)	7.25%	6.625%
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	8.00%	8.00%
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 (Fair Value By Level

Fair Value (Fair Value By Level) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets:
Available-for-sale securities	$ 4,152,070	$ 4,177,349
Assets/liabilities measured at fair value
Assets:
Available-for-sale securities	4,152,070	4,177,349
Assets/liabilities measured at fair value | Residential mortgage-backed securities
Assets:
Available-for-sale securities	3,891,233	3,894,470
Assets/liabilities measured at fair value | Obligations of states and political subdivisions
Assets:
Available-for-sale securities	232,951	254,972
Assets/liabilities measured at fair value | Equity securities
Assets:
Available-for-sale securities	27,886	27,907
Measured on a recurring basis: | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Available-for-sale securities	27,886	27,907
Measured on a recurring basis: | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities
Assets:
Available-for-sale securities	27,886	27,907
Measured on a recurring basis: | Significant Other Observable Inputs (Level 2)
Assets:
Available-for-sale securities	4,124,184	4,131,837
Measured on a recurring basis: | Significant Other Observable Inputs (Level 2) | Residential mortgage-backed securities
Assets:
Available-for-sale securities	3,891,233	3,876,865
Measured on a recurring basis: | Significant Other Observable Inputs (Level 2) | Obligations of states and political subdivisions
Assets:
Available-for-sale securities	232,951	254,972
Measured on a recurring basis: | Significant Unobservable Inputs (Level 3)
Assets:
Available-for-sale securities		17,605
Measured on a recurring basis: | Significant Unobservable Inputs (Level 3) | Residential mortgage-backed securities
Assets:
Available-for-sale securities		17,605
Measured on a recurring basis: | Assets/liabilities measured at fair value
Assets:
Available-for-sale securities	4,152,070	4,177,349
Measured on a recurring basis: | Assets/liabilities measured at fair value | Residential mortgage-backed securities
Assets:
Available-for-sale securities	3,891,233	3,894,470
Measured on a recurring basis: | Assets/liabilities measured at fair value | Obligations of states and political subdivisions
Assets:
Available-for-sale securities	232,951	254,972
Measured on a recurring basis: | Assets/liabilities measured at fair value | Equity securities
Assets:
Available-for-sale securities	$ 27,886	$ 27,907

Fair Value Measurements - (Reco

Fair Value Measurements - (Reconciliation) (Details) - Residential mortgage-backed securities $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Reconciliation of activity for mortgage-backed securities on a net basis
Balance at the beginning of the period	$ 17,605
Principal paydowns	(798)
Sales of available-for-sale securities	(21,904)
Reclassification of unrealized gains (losses) included in other comprehensive loss due to sale	$ 5,097

Fair Value (Fair Value Measurem

Fair Value (Fair Value Measurement and Assumptions) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets:
Impaired Loans	$ 53,267,000	$ 38,108,000
Non-financial assets:
Other real estate owned	30,519,000	42,204,000
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	30,000	381,000	$ 696,000
Adjustment to fair value in connection with other real estate owned	710,000	2,351,000	$ 1,023,000
Impaired commercial collateral dependent loans	53,267,000	38,108,000
Impaired commercial collateral dependent receivables appraisals to determine fair value within immediately preceding twelve months	18,585,000	26,162,000
Impaired collateral dependent commercial loans with internal evaluation completed within last twelve months	$ 0	$ 6,836,000
Significant Unobservable Inputs (Level 3) | Bond meeting 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%
Decrease in loss severity rates, following five years (as a percent)	5.00%
Estimated future principal prepayment rate assumption, discount rate (as a percent)	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	$ 2,138,000	$ 19,699,000
Change in net provision, other real estate owned	710,000	2,351,000
Measured on a non-recurring basis | Significant Unobservable Inputs (Level 3)
Assets:
Impaired Loans	11,210,000	38,794,000
Non-financial assets:
Other real estate owned	2,000,000	9,445,000
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Impaired commercial collateral dependent loans	11,210,000	38,794,000
Measured on a non-recurring basis | Assets/liabilities measured at fair value
Assets:
Impaired Loans	11,210,000	38,794,000
Non-financial assets:
Other real estate owned	2,000,000	9,445,000
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Impaired commercial collateral dependent loans	$ 11,210,000	$ 38,794,000

Fair Value Measurements (Other

Fair Value Measurements (Other Assumptions) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Deposits
Carrying amount of time deposits	$ 2,056,506,000	$ 2,248,310,000
Significant Unobservable Inputs (Level 3)
Loans
Carrying amount of fixed rate performing loans	1,505,531,000	1,411,272,000
Estimated fair value of fixed rate performing loans	1,454,434,000	1,375,807,000
Deposits
Carrying amount of time deposits	2,056,506,000	2,248,310,000
Estimated fair value of time deposits	2,058,621,000	2,247,648,000
Securities Sold Under Repurchase Agreements
Carrying amount of long-term repurchase agreements	100,000,000	300,000,000
Estimated fair value of long-term repurchase agreements	99,504,000	$ 289,324,000
Significant Other Observable Inputs (Level 2)
Other borrowed funds
Carrying amount of the long-term FHLB borrowings	250,000,000
Estimated fair value of long-term FHLB borrowings	$ 249,728,000

International Bancshares Corp94

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Condition (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
ASSETS
Other investments	$ 571,415	$ 517,162
Other assets	81,529	95,593
Total assets	12,184,698	11,804,041
Liabilities:
Junior subordinated deferrable interest debentures	160,416	160,416
Other liabilities	91,380	70,509
Total liabilities	10,345,718	10,079,374
Shareholders' equity:
Common shares	96,019	95,910
Surplus	171,816	169,567
Retained earnings	1,891,805	1,777,963
Accumulated other comprehensive (loss) income	(28,397)	(26,697)
Total shareholders' equity before treasury stock	2,131,243	2,016,743
Less cost of shares in treasury	(292,263)	(292,076)
Total shareholders' equity	1,838,980	1,724,667	$ 1,665,503	$ 1,580,658
Total liabilities and shareholders' equity	12,184,698	11,804,041
Parent Company
ASSETS
Cash	18,398	18,555
Other investments	92,620	94,908
Investment in subsidiaries	1,878,521	1,787,120
Other assets	23,120	1,098
Total assets	2,012,659	1,901,681
Liabilities:
Junior subordinated deferrable interest debentures	160,416	160,416
Due to IBC Trading	21	21
Other liabilities	13,242	16,577
Total liabilities	173,679	177,014
Shareholders' equity:
Common shares	96,019	95,910
Surplus	171,816	169,567
Retained earnings	1,891,805	1,777,963
Accumulated other comprehensive (loss) income	(28,397)	(26,697)
Total shareholders' equity before treasury stock	2,131,243	2,016,743
Less cost of shares in treasury	(292,263)	(292,076)
Total shareholders' equity	1,838,980	1,724,667
Total liabilities and shareholders' equity	$ 2,012,659	$ 1,901,681

International Bancshares Corp95

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Expenses:
Interest expense (Debentures)	$ 5,392	$ 4,600	$ 4,099
Income before federal income taxes and equity in undistributed net income of subsidiaries	221,642	197,003	206,842
Income tax expense	64,206	63,071	70,116
Net income	157,436	133,932	136,726
Parent Company
Income:
Dividends from subsidiaries	64,600	84,432	51,575
Interest income on notes receivable		2	7
Interest income on other investments	8,100	8,958	5,738
Other	26	255	3,442
Total income	72,726	93,647	60,762
Expenses:
Interest expense (Debentures)	5,392	4,600	4,099
Other	5,648	3,637	3,037
Total expenses	11,040	8,237	7,136
Income before federal income taxes and equity in undistributed net income of subsidiaries	61,686	85,410	53,626
Income tax expense	(2,076)	311	386
Income before equity in undistributed net income of subsidiaries	63,762	85,099	53,240
Equity in undistributed net income of subsidiaries	93,674	48,833	83,486
Net income	$ 157,436	$ 133,932	$ 136,726

International Bancshares Corp96

International Bancshares Corporation (Parent Company Only) Financial Information Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income	$ 157,436	$ 133,932	$ 136,726
Adjustments to reconcile net income to net cash provided by operating activities:
Investment securities transactions, net	(4,774)	(2,626)	(3,682)
Impairment charges on available for sale securities		354	954
Stock compensation expense	903	1,082	1,172
(Decrease) increase in other liabilities	592	(7,705)	(6,567)
Net cash provided by operating activities	196,819	203,220	203,649
Investing activities:
Principal collected on mortgage-backed securities	780,097	919,594	854,736
Net cash (used in) provided by investing activities	(403,807)	(137,763)	373,225
Financing activities:
Repayment of long-term debt		(1,000)	(14,000)
Proceeds from stock transactions	1,455	549	1,370
Payments of cash dividends - common	(43,594)	(39,569)	(38,515)
Purchase of treasury stock	(187)	(7,966)	(6,678)
Net cash provided by (used in) financing activities	203,147	(69,312)	(558,967)
(Decrease) increase in cash and cash equivalents	(3,841)	(3,855)	17,907
Cash and cash equivalents at beginning of period	269,198	273,053
Cash and cash equivalents at end of period	265,357	269,198	273,053
Parent Company
Operating activities:
Net income	157,436	133,932	136,726
Adjustments to reconcile net income to net cash provided by operating activities:
Investment securities transactions, net	(23)
Impairment charges on available for sale securities		112	385
Stock compensation expense	903	1,082	1,172
(Decrease) increase in other liabilities	(3,453)	3,901	(1,998)
Equity in undistributed net income of subsidiaries	(93,674)	(48,833)	(83,486)
Net cash provided by operating activities	61,189	90,194	52,799
Investing activities:
Principal collected on mortgage-backed securities	6,328	1,105	474
Net decrease in notes receivable		99	105
Increase in other assets and other investments	(25,348)	(27,834)	(1,830)
Net cash (used in) provided by investing activities	(19,020)	(26,630)	(1,251)
Financing activities:
Repayment of long-term debt		(1,000)	(14,000)
Proceeds from stock transactions	1,455	549	1,370
Payments of cash dividends - common	(43,594)	(39,569)	(38,515)
Purchase of treasury stock	(187)	(7,966)	(6,678)
Net cash provided by (used in) financing activities	(42,326)	(47,986)	(57,823)
(Decrease) increase in cash and cash equivalents	(157)	15,578	(6,275)
Cash and cash equivalents at beginning of period	18,555	2,977	9,252
Cash and cash equivalents at end of period	$ 18,398	$ 18,555	$ 2,977