First Financial Bankshares (FFIN) 10-Q 4 Aug 15 2015 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2015	Aug. 04, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q2
Trading Symbol	FFIN
Entity Registrant Name	FIRST FINANCIAL BANKSHARES INC
Entity Central Index Key	36,029
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		64,176,986

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
ASSETS
CASH AND DUE FROM BANKS	$ 149,524	$ 190,387	$ 166,237
FEDERAL FUNDS SOLD	5,720	8,760	3,110
INTEREST-BEARING DEPOSITS IN BANKS	18,179	54,324	68,331
Total cash and cash equivalents	173,423	253,471	237,678
INTEREST-BEARING TIME DEPOSITS IN BANKS	5,456	17,002	24,188
SECURITIES AVAILABLE-FOR-SALE, at fair value	2,729,113	2,415,856	2,173,828
SECURITIES HELD-TO-MATURITY (fair value of $301, $576 and $447 at June 30, 2015 and 2014, and December 31, 2014, respectively)	295	441	568
LOANS:
Held for investment	2,942,224	2,929,188	2,773,074
Less - allowance for loan losses	(38,999)	(36,824)	(35,892)
Net loans held for investment	2,903,225	2,892,364	2,737,182
Held for sale	25,544	8,803	13,570
Net loans	2,928,769	2,901,167	2,750,752
BANK PREMISES AND EQUIPMENT, net	104,495	103,000	96,619
INTANGIBLE ASSETS	99,039	97,359	97,429
OTHER ASSETS	74,646	59,906	65,294
Total assets	6,115,236	5,848,202	5,446,356
LIABILITIES AND SHAREHOLDERS' EQUITY
NONINTEREST-BEARING DEPOSITS	1,574,745	1,570,330	1,445,947
INTEREST-BEARING DEPOSITS	3,152,674	3,179,925	2,872,511
Total deposits	4,727,419	4,750,255	4,318,458
DIVIDENDS PAYABLE	10,265	8,972	8,968
SHORT-TERM BORROWINGS	621,155	367,110	434,583
OTHER LIABILITIES	55,204	40,328	44,311
Total liabilities	$ 5,414,043	$ 5,166,665	$ 4,806,320
COMMITMENTS AND CONTINGENCIES
SHAREHOLDERS' EQUITY:
Common stock - ($0.01 par value, authorized 120,000,000 shares; 64,156,302, 64,053,010 and 64,089,921 shares issued at June 30, 2015, 2014 and December 31, 2014, respectively)	$ 642	$ 641	$ 640
Capital surplus	306,763	305,429	304,308
Retained earnings	358,037	327,978	299,902
Treasury stock (shares at cost: 527,001, 534,905 and 529,563 at June 30, 2015, 2014 and December 31, 2014, respectively)	(6,110)	(5,878)	(5,723)
Deferred compensation	6,110	5,878	5,723
Accumulated other comprehensive earnings	35,751	47,489	35,186
Total shareholders' equity	701,193	681,537	640,036
Total liabilities and shareholders' equity	$ 6,115,236	$ 5,848,202	$ 5,446,356

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Statement of Financial Position [Abstract]
SECURITIES HELD-TO-MATURITY, fair value	$ 301	$ 447	$ 576
Common stock, par value	$ 0.01	$ 0.01	$ 0.01
Common stock, shares authorized	120,000,000	120,000,000	120,000,000
Common stock, shares issued	64,156,302	64,089,921	64,053,010
Treasury stock, shares	527,001	529,563	534,905

Consolidated Statements of Earn

Consolidated Statements of Earnings (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
INTEREST INCOME:
Interest and fees on loans	$ 36,034	$ 33,846	$ 71,095	$ 66,904
Interest on investment securities:
Taxable	7,399	7,091	15,207	14,175
Exempt from federal income tax	9,861	8,228	18,981	16,208
Interest on federal funds sold and interest-bearing deposits in banks	50	89	130	176
Total interest income	53,344	49,254	105,413	97,463
INTEREST EXPENSE:
Interest on deposits	902	955	1,829	1,895
Other	106	82	148	178
Total interest expense	1,008	1,037	1,977	2,073
Net interest income	52,336	48,217	103,436	95,390
PROVISION FOR LOAN LOSSES	1,554	1,124	2,844	2,814
Net interest income after provision for loan losses	50,782	47,093	100,592	92,576
NONINTEREST INCOME:
Trust fees	4,740	4,549	9,472	9,125
Service charges on deposit accounts	4,021	4,174	7,789	8,221
ATM, interchange and credit card fees	5,445	4,754	10,415	9,197
Real estate mortgage operations	1,942	1,337	3,368	2,361
Net gain (loss) on sale of available-for-sale securities (includes $239 and ($1) for the three months ended June 30, 2015 and 2014, respectively, and $244 and ($5) for the six months ended June 30, 2015 and 2014, respectively, related to accumulated other comprehensive earnings reclassifications)	239	(1)	244	(5)
Net gain (loss) on sale of foreclosed assets	(49)	47	(19)	499
Other	1,471	1,012	2,438	2,879
Total noninterest income	17,809	15,872	33,707	32,277
NONINTEREST EXPENSE:
Salaries and employee benefits	19,173	17,274	37,438	34,688
Net occupancy expense	2,394	2,273	4,590	4,507
Equipment expense	2,992	2,665	5,891	5,287
FDIC insurance premiums	749	684	1,498	1,343
ATM, interchange and credit card expenses	1,609	1,696	3,335	3,176
Professional and service fees	1,157	963	2,222	2,044
Printing, stationery and supplies	471	554	1,067	1,329
Amortization of intangible assets	72	74	162	148
Other	6,587	8,819	12,948	14,927
Total noninterest expense	35,204	35,002	69,151	67,449
EARNINGS BEFORE INCOME TAXES	33,387	27,963	65,148	57,404
INCOME TAX EXPENSE (includes $84 and $0 for the three months ended June 30, 2015 and 2014, respectively, and $85 and ($2) for the six months ended June 30, 2015 and 2014, respectively, related to income tax expense from reclassification items)	8,080	6,758	15,845	13,863
NET EARNINGS	$ 25,307	$ 21,205	$ 49,303	$ 43,541
EARNINGS PER SHARE, BASIC	$ 0.39	$ 0.33	$ 0.77	$ 0.68
EARNINGS PER SHARE, ASSUMING DILUTION	0.39	0.33	0.77	0.68
DIVIDENDS PER SHARE	$ 0.16	$ 0.14	$ 0.30	$ 0.27

Consolidated Statements of Ear5

Consolidated Statements of Earnings (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Statement [Abstract]
Reclassifications adjustment for realized gains on investment securities included in net earnings (loss), before income tax	$ 239	$ (1)	$ 244	$ (5)
Income tax expense from reclassification items	$ 84	$ 0	$ 85	$ (2)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Earnings (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Amounts Reclassified Out Of Accumulated Other Comprehensive Income Loss [Abstract]
NET EARNINGS	$ 25,307	$ 21,205	$ 49,303	$ 43,541
OTHER ITEMS OF COMPREHENSIVE EARNINGS (LOSS):
Change in unrealized gain (loss) on investment securities available-for-sale, before income taxes	(31,190)	16,622	(17,707)	38,182
Reclassification adjustment for realized losses (gains) on investment securities included in net earnings, before income tax	(239)	1	(244)	5
Minimum liability pension adjustment, before income taxes	(108)		(108)
Total other items of comprehensive earnings (losses)	(31,537)	16,623	(18,059)	38,187
Income tax benefit (expense) related to:
Investment securities	11,000	(5,818)	6,283	(13,365)
Minimum liability pension adjustment	38		38
Total income tax benefit (expense)	11,038	(5,818)	6,321	(13,365)
COMPREHENSIVE EARNINGS	$ 4,808	$ 32,010	$ 37,565	$ 68,363

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Deferred Compensation [Member]	Accumulated Other Comprehensive Earnings [Member]
Beginning Balance at Dec. 31, 2013	$ 587,647	$ 320	$ 302,991	$ 273,972	$ (5,490)	$ 5,490	$ 10,364
Beginning Balance, Shares at Dec. 31, 2013		31,992,497			(269,467)
NET EARNINGS (unaudited)	43,541			43,541
Stock option exercises (unaudited)	910		910
Stock option exercises, Shares (unaudited)		37,753
Cash dividends declared (unaudited)	(17,291)			(17,291)
Change in unrealized gain in investment securities available-for-sale, net of related income taxes (unaudited)	24,822						24,822
Additional tax benefit related to directors' deferred compensation plan (unaudited)	50		50
Shares redeemed in connection with directors' deferred compensation plan, net (unaudited)					$ (233)	233
Shares redeemed in connection with directors' deferred compensation plan, net, Shares (unaudited)					2,696
Stock option expense (unaudited)	357		357
Two-for-one stock split in the form of a 100% stock dividend (unaudited)		$ 320		(320)
Two-for-one stock split in the form of a 100% stock dividend, Shares (unaudited)		32,022,760			(268,134)
Ending Balance (unaudited) at Jun. 30, 2014	640,036	$ 640	304,308	299,902	$ (5,723)	5,723	35,186
Ending Balance, Shares (unaudited) at Jun. 30, 2014		64,053,010			(534,905)
Beginning Balance at Dec. 31, 2014	681,537	$ 641	305,429	327,978	$ (5,878)	5,878	47,489
Beginning Balance, Shares at Dec. 31, 2014		64,089,921			(529,563)
NET EARNINGS (unaudited)	49,303			49,303
Stock option exercises (unaudited)	925	$ 1	924
Stock option exercises, Shares (unaudited)		66,381
Cash dividends declared (unaudited)	(19,244)			(19,244)
Minimum liability pension adjustment, net of related income taxes (unaudited)	(70)						(70)
Change in unrealized gain in investment securities available-for-sale, net of related income taxes (unaudited)	(11,668)						(11,668)
Additional tax benefit related to directors' deferred compensation plan (unaudited)	50		50
Shares redeemed in connection with directors' deferred compensation plan, net (unaudited)					$ (232)	232
Shares redeemed in connection with directors' deferred compensation plan, net, Shares (unaudited)		0			2,562
Stock option expense (unaudited)	360		360
Ending Balance (unaudited) at Jun. 30, 2015	$ 701,193	$ 642	$ 306,763	$ 358,037	$ (6,110)	$ 6,110	$ 35,751
Ending Balance, Shares (unaudited) at Jun. 30, 2015		64,156,302			(527,001)

Consolidated Statements of Sha8

Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash dividend per share (unaudited)	$ 0.30	$ 0.27
Percentage of stock dividend (unaudited)		100.00%
Common Stock [Member]
Percentage of stock dividend (unaudited)		100.00%
Retained Earnings [Member]
Cash dividend per share (unaudited)	$ 0.30	$ 0.27
Percentage of stock dividend (unaudited)		100.00%

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
NET EARNINGS	$ 49,303	$ 43,541
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	5,074	4,573
PROVISION FOR LOAN LOSSES	2,844	2,814
Securities premium amortization (discount accretion), net	13,164	9,568
Gain on sale of assets, net	(226)	(541)
Deferred federal income tax benefit	(763)	(971)
Change in loans held for sale, net	(16,741)	(8,407)
Change in other assets	(15,129)	4,972
Change in other liabilities	8,022	4,877
Total adjustments	(3,755)	16,885
Net cash provided by operating activities	45,548	60,426
CASH FLOWS FROM INVESTING ACTIVITIES:
Cash paid for asset acquisition of 4Trust Mortgage, Inc.	(1,931)
Net decrease in interest-bearing time deposits in banks	11,546	7,729
Activity in available-for-sale securities:
Sales	7,760	1,445
Maturities	2,111,206	621,807
Purchases	(2,448,852)	(710,574)
Activity in held-to-maturity securities - maturities	146	116
Net increase in loans	(13,802)	(90,627)
Purchases of bank premises and equipment and other assets	(6,240)	(5,400)
Proceeds from sale of other assets	390	2,397
Net cash used in investing activities	(339,777)	(173,107)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in noninterest-bearing deposits	4,415	83,763
Net increase (decrease) in interest-bearing deposits	(27,251)	99,620
Net increase (decrease) in short-term borrowings	254,045	(29,305)
Common stock transactions:
Proceeds from stock issuances	924	910
Dividends paid	(17,952)	(16,641)
Net cash provided by financing activities	214,181	138,347
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(80,048)	25,666
CASH AND CASH EQUIVALENTS, beginning of period	253,471	212,012
CASH AND CASH EQUIVALENTS, end of period	173,423	237,678
SUPPLEMENTAL INFORMATION AND NONCASH TRANSACTIONS:
Interest paid	1,972	2,070
Federal income tax paid	13,994	14,445
Transfer of loans to foreclosed assets	97	1,015
Investment securities purchased but not settled	$ 15,483	$ 7,417

Basis of Presentation

Basis of Presentation	6 Months Ended
	Jun. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Note 1 - Basis of Presentation The unaudited interim consolidated financial statements include the accounts of the Company, a Texas corporation and a financial holding company registered under the Bank Holding Company Act of 1956, as amended, or BHCA, and its wholly-owned subsidiaries: First Financial Bank, National Association, Abilene, Texas; First Technology Services, Inc.; First Financial Trust & Asset Management Company, National Association; First Financial Investments, Inc.; and First Financial Insurance Agency, Inc. Through our subsidiary bank, we conduct a full-service commercial banking business. Our banking centers are located primarily in Central, North Central, Southeast and West Texas. As of June 30, 2015, we had 62 financial centers across Texas, with eleven locations in Abilene, three locations in San Angelo and Weatherford, two locations in Cleburne, Stephenville and Granbury, and one location each in Acton, Albany, Aledo, Alvarado, Beaumont, Boyd, Bridgeport, Brock, Burleson, Cisco, Clyde, Decatur, Eastland, Fort Worth, Glen Rose, Grapevine, Hereford, Huntsville, Keller, Mauriceville, Merkel, Midlothian, Mineral Wells, Moran, New Waverly, Newton, Odessa, Orange, Port Arthur, Ranger, Rising Star, Roby, Southlake, Sweetwater, Trent, Trophy Club, Vidor, Waxahachie, and Willow Park and three mortgage origination offices in Dallas, Ft. Worth and Southlake, Texas. Our trust subsidiary has eight locations which are located in Abilene, Fort Worth, Lubbock, Odessa, Beaumont, San Angelo, Stephenville and Sweetwater, all in Texas. In the opinion of management, the unaudited interim consolidated financial statements reflect all adjustments necessary for a fair presentation of the Company’s financial position and unaudited results of operations and should be read in conjunction with the Company’s audited consolidated financial statements, and notes thereto in the Company’s Annual Report on Form 10-K, for the year ended December 31, 2014. All adjustments were of a normal recurring nature. However, the results of operations for the three months and six months ended June 30, 2015, are not necessarily indicative of the results to be expected for the year ending December 31, 2015, due to seasonality, changes in economic conditions and loan credit quality, interest rate fluctuations, regulatory and legislative changes and other factors. The preparation of financial statements in conformity with United States generally accepted accounting principles (“GAAP”) require management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the financial statement date. Actual results could vary. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted under U. S. Securities and Exchange Commission (“SEC”) rules and regulations. The Company evaluated subsequent events for potential recognition and/or disclosure through the date the consolidated financial statements were issued. On April 28, 2015, the Company’s shareholders approved an amendment to the Company’s Amended and Restated Certificate of Formation to increase the number of authorized common shares to 120,000,000. On October 28, 2014, the Company’s Board of Directors authorized the repurchase of up to 1,500,000 common shares through September 30, 2017. The stock buyback plan authorizes management to repurchase the stock at such time as repurchases are considered beneficial to shareholders. Any repurchase of stock will be made through the open market, block trades or in privately negotiated transactions in accordance with applicable laws and regulations. Under the repurchase plan, there is no minimum number of shares that the Company is required to repurchase. Through June 30, 2015, no shares were repurchased under this authorization. Goodwill and other intangible assets are evaluated annually for impairment as of the end of the second quarter. No such impairment has been noted in connection with the current or any prior evaluations.

Stock Split

Stock Split	6 Months Ended
	Jun. 30, 2015
Text Block [Abstract]
Stock Split	Note 2 - Stock Split On April 22, 2014, the Company’s Board of Directors declared a two-for-one stock split in the form of a 100% stock dividend effective for shareholders of record on May 15, 2014 that was distributed on June 2, 2014. All per share amounts in this report have been restated to reflect this stock split. An amount equal to the par value of the additional common shares issued pursuant to the stock split was reflected as a transfer from retained earnings to common stock on the consolidated financial statements as of and for the six months ended June 30, 2014.

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 30, 2015
Earnings Per Share [Abstract]
Earnings Per Share	Note 3 - Earnings Per Share Basic earnings per common share is computed by dividing net income available to common shareholders by the weighted average number of shares outstanding during the periods presented. In computing diluted earnings per common share for the three and six months ended June 30, 2015 and 2014, the Company assumes that all dilutive outstanding options to purchase common stock have been exercised at the beginning of the period (or the time of issuance, if later). The dilutive effect of the outstanding options is reflected by application of the treasury stock method, whereby the proceeds from the exercised options are assumed to be used to purchase common stock at the average market price during the respective periods. The weighted average common shares outstanding used in computing basic earnings per common share for the three months ended June 30, 2015 and 2014 were 64,148,356 and 64,045,282 shares, respectively. The weighted average common shares outstanding used in computing basic earnings per common share for the six months ended June 30, 2015 and 2014 were 64,135,731 and 64,027,776 shares, respectively. The weighted average common shares outstanding used in computing fully diluted earnings per common share for the three months ended June 30, 2015 and 2014 were 64,354,720 and 64,301,306 shares, respectively. The weighted average common shares outstanding used in computing fully diluted earnings per common share for the six months ended June 30, 2015 and 2014 were 64,328,672 and 64,298,525 shares, respectively.

Interest-bearing Time Deposits

Interest-bearing Time Deposits in Banks and Securities	6 Months Ended
	Jun. 30, 2015
Cash and Cash Equivalents [Abstract]
Interest-bearing Time Deposits in Banks and Securities	Note 4 - Interest-bearing Time Deposits in Banks and Securities Interest-bearing time deposits in banks totaled $5,456,000, $24,188,000 and $17,002,000 at June 30, 2015 and 2014 and December 31, 2014, respectively, and have original maturities generally ranging from one to four years. Of these amounts, $983,000, $5,269,000 and $3,195,000 are time deposits with balances greater than $250,000, the FDIC insured limit, at June 30, 2015 and 2014 and December 31, 2014, respectively. Management classifies debt and equity securities as held-to-maturity, available-for-sale, or trading based on its intent. Debt securities that management has the positive intent and ability to hold to maturity are classified as held-to-maturity and recorded at cost, adjusted for amortization of premiums and accretion of discounts, which are recognized as adjustments to interest income using the interest method. Securities not classified as held-to-maturity or trading are classified as available-for-sale and recorded at fair value, with all unrealized gains and unrealized losses judged to be temporary, net of deferred income taxes, excluded from earnings and reported in the consolidated statements of comprehensive earnings. Available-for-sale securities that have unrealized losses that are judged other-than-temporary are included in gain (loss) on sale of securities and a new cost basis is established. Securities classified as trading are recorded at fair value with unrealized gains and losses included in earnings. The Company records its available-for-sale and trading securities portfolio at fair value. Fair values of these securities are determined based on methodologies in accordance with current authoritative accounting guidance. Fair values are volatile and may be influenced by a number of factors, including market interest rates, prepayment speeds, discount rates, credit ratings and yield curves. Fair values for investment securities are based on quoted market prices, where available. If quoted market prices are not available, fair values are based on the quoted prices of similar instruments or an estimate of fair value by using a range of fair value estimates in the market place as a result of the illiquid market specific to the type of security. When the fair value of a security is below its amortized cost, and depending on the length of time the condition exists and the extent the fair value is below amortized cost, additional analysis is performed to determine whether an other-than-temporary impairment condition exists. Available-for-sale and held-to-maturity securities are analyzed quarterly for possible other-than-temporary impairment. The analysis considers (i) whether we have the intent to sell our securities prior to recovery and/or maturity, (ii) whether it is more likely than not that we will have to sell our securities prior to recovery and/or maturity, (iii) the length of time and extent to which the fair value has been less than amortized cost, and (iv) the financial condition of the issuer. Often, the information available to conduct these assessments is limited and rapidly changing, making estimates of fair value subject to judgment. If actual information or conditions are different than estimated, the extent of the impairment of the security may be different than previously estimated, which could have a material effect on the Company’s results of operations and financial condition. The Company’s investment portfolio consists of U.S. Treasury securities, obligations of U. S. government sponsored enterprises and agencies, obligations of state and political subdivisions, mortgage pass-through securities, corporate bonds and general obligation or revenue based municipal bonds. Pricing for such securities is generally readily available and transparent in the market. The Company utilizes independent third party pricing services to value its investment securities, which the Company reviews as well as the underlying pricing methodologies for reasonableness and to ensure such prices are aligned with pricing matrices. The Company validates quarterly, on a sample basis, prices supplied by the independent pricing services by comparison to prices obtained from other third party sources. A summary of the Company’s available-for-sale securities follows (in thousands): June 30, 2015 Amortized Gross Gross Estimated U.S. Treasury securities $ 10,864 $ 72 $ — $ 10,936 Obligations of U.S. government sponsored enterprises and agencies 164,351 985 — 165,336 Obligations of states and political subdivisions 1,340,163 49,483 (5,400 ) 1,384,246 Corporate bonds and other 94,485 2,623 — 97,108 Residential mortgage-backed securities 856,546 14,383 (2,838 ) 868,091 Commercial mortgage-backed securities 203,482 591 (677 ) 203,396 Total securities available-for-sale $ 2,669,891 $ 68,137 $ (8,915 ) $ 2,729,113 June 30, 2014 Amortized Gross Gross Estimated Obligations of U.S. government sponsored-enterprises and agencies $ 118,907 $ 1,210 $ — $ 120,117 Obligations of states and political subdivisions 1,027,503 49,171 (2,016 ) 1,074,658 Corporate bonds and other 97,119 3,621 — 100,740 Residential mortgage-backed securities 734,301 16,183 (5,011 ) 745,473 Commercial mortgage-backed securities 135,214 34 (2,408 ) 132,840 Total securities available-for-sale $ 2,113,044 $ 70,219 $ (9,435 ) $ 2,173,828 December 31, 2014 Amortized Gross Gross Estimated U.S. Treasury securities $ 518 $ 2 $ — $ 520 Obligations of U.S. government sponsored enterprises and agencies 128,919 864 (28 ) 129,755 Obligations of states and political subdivisions 1,107,795 60,083 (250 ) 1,167,628 Corporate bonds and other 95,864 2,894 — 98,758 Residential mortgage-backed securities 871,265 16,804 (2,858 ) 885,211 Commercial mortgage-backed securities 134,322 555 (893 ) 133,984 Total securities available-for-sale $ 2,338,683 $ 81,202 $ (4,029 ) $ 2,415,856 Disclosures related to the Company’s held-to-maturity securities, which totaled $295,000, $568,000 and $441,000 at June 30, 2015 and 2014, and December 31, 2014, respectively, have not been presented due to insignificance. The Company invests in mortgage-backed securities that have expected maturities that differ from their contractual maturities. These differences arise because borrowers may have the right to call or prepay obligations with or without a prepayment penalty. These securities include collateralized mortgage obligations (CMOs) and other asset backed securities. The expected maturities of these securities at June 30, 2015 were computed by using scheduled amortization of balances and historical prepayment rates. At June 30, 2015 and 2014 and December 31, 2014, the Company did not hold CMOs that entail higher risks than standard mortgage-backed securities. The amortized cost and estimated fair value of available-for-sale securities at June 30, 2015, by contractual and expected maturity, are shown below (in thousands): Amortized Estimated Due within one year $ 133,995 $ 135,181 Due after one year through five years 707,981 737,467 Due after five years through ten years 750,600 767,300 Due after ten years 17,287 17,678 Mortgage-backed securities 1,060,028 1,071,487 Total $ 2,669,891 $ 2,729,113 The following tables disclose, as of June 30, 2015 and 2014, and December 31, 2014, the Company’s investment securities that have been in a continuous unrealized-loss position for less than 12 months and for 12 or more months (in thousands): Less than 12 Months 12 Months or Longer Total June 30, 2015 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Obligations of states and political subdivisions $ 304,510 $ 5,335 $ 2,531 $ 65 $ 307,041 $ 5,400 Residential mortgage-backed securities 176,569 844 65,562 1,994 242,131 2,838 Commercial mortgage-backed securities 134,151 628 9,504 49 143,655 677 Total $ 615,230 $ 6,807 $ 77,597 $ 2,108 $ 692,827 $ 8,915 Less than 12 Months 12 Months or Longer Total June 30, 2014 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Obligations of states and political subdivisions $ 41,095 $ 160 $ 101,800 $ 1,856 $ 142,895 $ 2,016 Residential mortgage-backed securities 133,104 4,417 23,427 594 156,531 5,011 Commercial mortgage-backed securities 97,972 2,075 10,142 333 108,114 2,408 Total $ 272,171 $ 6,652 $ 135,369 $ 2,783 $ 407,540 $ 9,435 Less than 12 Months 12 Months or Longer Total December 31, 2014 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Obligations of U.S. government sponsored enterprises and agencies $ 25,480 $ 28 $ — $ — $ 25,480 $ 28 Obligations of states and political subdivisions 15,128 60 21,249 190 36,377 250 Residential mortgage-backed securities 76,350 148 128,368 2,710 204,718 2,858 Commercial mortgage-backed securities 48,399 273 55,065 620 103,464 893 Total $ 165,357 $ 509 $ 204,682 $ 3,520 $ 370,039 $ 4,029 The number of investments in an unrealized loss position totaled 262 at June 30, 2015. We do not believe these unrealized losses are “other-than-temporary” as (i) we do not have the intent to sell our securities prior to recovery and/or maturity and (ii) it is more likely than not that we will not have to sell our securities prior to recovery and/or maturity. In making this determination, we also consider the length of time and extent to which fair value has been less than cost and the financial condition of the issuer. The unrealized losses noted are interest rate related due to the level of interest rates at June 30, 2015 compared to the time of purchase. We have reviewed the ratings of the issuers and have not identified any issues related to the ultimate repayment of principal as a result of credit concerns on these securities. Our mortgage related securities are backed by GNMA, FNMA and FHLMC or are collateralized by securities backed by these agencies. At June 30, 2015, $1,543,543,000 of the Company’s securities were pledged as collateral for public or trust fund deposits, repurchase agreements and for other purposes required or permitted by law. During the quarters ended June 30, 2015 and 2014, sales of investment securities that were classified as available-for-sale totaled $6,631,000 and $541,000, respectively. Gross realized gains from security sales in the second quarter of 2015 totaled $243,000. There were no gross realized gains on security sales in the second quarter of 2014. Gross realized losses from security sales during the second quarter of 2015 and 2014 totaled $4,000 and $1,000, respectively. During the six months ended June 30, 2015 and 2014, sales of investment securities that were classified as available-for-sale totaled $7,760,000 and $1,445,000, respectively. Gross realized gains from security sales during the six-month periods ended June 30, 2015 and 2014 totaled $248,000 and $1,000, respectively. Gross realized losses from security sales during the six-month periods ended June 30, 2015 and 2014 totaled $4,000 and $6,000, respectively. The specific identification method was used to determine cost in order to compute the realized gains and losses.

Loans and Allowance for Loan Lo

Loans and Allowance for Loan Losses	6 Months Ended
	Jun. 30, 2015
Receivables [Abstract]
Loans and Allowance for Loan Losses	Note 5 - Loans and Allowance for Loan Losses Loans held for investment are stated at the amount of unpaid principal, reduced by unearned income and an allowance for loan losses. Interest on loans is calculated by using the simple interest method on daily balances of the principal amounts outstanding. The Company defers and amortizes net loan origination fees and costs as an adjustment to yield. The allowance for loan losses is established through a provision for loan losses charged to expense. Loans are charged against the allowance for loan losses when management believes the collectability of the principal is unlikely. The Company has certain lending policies and procedures in place that are designed to maximize loan income with an acceptable level of risk. Management reviews and approves these policies and procedures on an annual basis and makes changes as appropriate. Management receives and reviews monthly reports related to loan originations, quality, concentrations, delinquencies, nonperforming and potential problem loans. Diversification in the loan portfolio is a means of managing risk associated with fluctuations in economic conditions, both by type of loan and geographic location. Commercial loans are underwritten after evaluating and understanding the borrower’s ability to operate profitably and effectively. Underwriting standards are designed to determine whether the borrower possesses sound business ethics and practices and to evaluate current and projected cash flows to determine the ability of the borrower to repay their obligations as agreed. Commercial loans are primarily made based on the identified cash flows of the borrower and, secondarily, on the underlying collateral provided by the borrower. Most commercial loans are secured by the assets being financed or other business assets, such as accounts receivable or inventory, and include personal guarantees. Agricultural loans are subject to underwriting standards and processes similar to commercial loans. These agricultural loans are based primarily on the identified cash flows of the borrower and secondarily on the underlying collateral provided by the borrower. Most agricultural loans are secured by the agriculture related assets being financed, such as farm land, cattle or equipment, and include personal guarantees. Real estate loans are also subject to underwriting standards and processes similar to commercial and agricultural loans. These loans are underwritten primarily based on projected cash flows and, secondarily, as loans secured by real estate. The repayment of real estate loans is generally largely dependent on the successful operation of the property securing the loans or the business conducted on the property securing the loan. Real estate loans may be more adversely affected by conditions in the real estate markets or in the general economy. The properties securing the Company’s real estate portfolio are generally diverse in terms of type and geographic location within Texas. This diversity helps reduce the exposure to adverse economic events that affect any single market or industry. Generally, real estate loans are owner occupied which further reduces the Company’s risk. Consumer loan underwriting utilizes methodical credit standards and analysis to supplement the Company’s underwriting policies and procedures. The Company’s loan policy addresses types of consumer loans that may be originated and the collateral, if secured, which must be perfected. The relatively smaller individual dollar amounts of consumer loans that are spread over numerous individual borrowers also minimize the Company’s risk. The allowance for loan losses is an amount which represents management’s best estimate of probable losses that are inherent in the Company’s loan portfolio as of the balance sheet date. The allowance for loan losses is comprised of three elements: (i) specific reserves determined based on probable losses on specific classified loans; (ii) a historical valuation reserve component that considers historical loss rates; and (iii) qualitative reserves based upon general economic conditions and other qualitative risk factors both internal and external to the Company. The allowance for loan losses is increased by charges to income and decreased by charge-offs Although we believe we use the best information available to make loan loss allowance determinations, future adjustments could be necessary if circumstances or economic conditions differ substantially from the assumptions used in making our initial determinations. A downturn in the economy and employment could result in increased levels of non-performing assets and charge-offs, increased loan provisions and reductions in income. Additionally, bank regulatory agencies periodically review our allowance for loan losses and methodology and could require, in accordance with generally accepted accounting principles, additional provisions to the allowance for loan losses based on their judgment of information available to them at the time of their examination as well as changes to our methodology. Accrual of interest is discontinued on a loan and payments are applied to principal when management believes, after considering economic and business conditions and collection efforts, the borrower’s financial condition is such that collection of interest is doubtful. Except consumer loans, generally all loans past due greater than 90 days, based on contractual terms, are placed on non-accrual. Loans are returned to accrual status when all the principal and interest amounts contractually due are brought current and future payments are reasonably assured. Consumer loans are generally charged-off when a loan becomes past due 90 days. For other loans in the portfolio, facts and circumstances are evaluated in making charge-off decisions. Loans are considered impaired when, based on current information and events, management determines that it is probable we will be unable to collect all amounts due in accordance with the loan agreement, including scheduled principal and interest payments. If a loan is impaired, a specific valuation allowance is allocated, if necessary. Interest payments on impaired loans are typically applied to principal unless collectability of the principal amount is reasonably assured, in which case interest is recognized on a cash basis. Impaired loans, or portions thereof, are charged off when deemed uncollectable. The Company’s policy requires measurement of the allowance for an impaired, collateral dependent loan based on the fair value of the collateral. Other loan impairments for non-collateral dependent loans are measured based on the present value of expected future cash flows or the loan’s observable market price. At June 30, 2015 and 2014, and December 31, 2014, all significant impaired loans have been determined to be collateral dependent and the allowance for loss has been measured utilizing the estimated fair value of the collateral. From time to time, the Company modifies its loan agreement with a borrower. A modified loan is considered a troubled debt restructuring when two conditions are met: (i) the borrower is experiencing financial difficulty and (ii) concessions are made by the Company that would not otherwise be considered for a borrower with similar credit risk characteristics. Modifications to loan terms may include a lower interest rate, a reduction of principal, or a longer term to maturity. For all impaired loans, including the Company’s troubled debt restructurings, the Company performs a periodic, well-documented credit evaluation of the borrower’s financial condition and prospects for repayment to assess the likelihood that all principal and interest payments required under the terms of the agreement will be collected in full. When doubt exists about the ultimate collectability of principal and interest, the troubled debt restructuring remains on non-accrual status and payments received are applied to reduce principal to the extent necessary to eliminate such doubt. This determination of accrual status is judgmental and is based on facts and circumstances related to each troubled debt restructuring. Each of these loans is individually evaluated for impairment and a specific reserve is recorded based on probable losses, taking into consideration the related collateral, modified loan terms and cash flow. As of June 30, 2015 and 2014, and December 31, 2014, substantially all of the Company’s troubled debt restructured loans are included in the non-accrual totals. The Company originates certain mortgage loans for sale in the secondary market. Accordingly, these loans are classified as held-for-sale and are carried at the lower of cost or fair value on an aggregate basis. The mortgage loan sales contracts contain indemnification clauses should the loans default, generally in the first three to six months, or if documentation is determined not to be in compliance with regulations. The Company’s historic losses as a result of these indemnities have been insignificant. Loans acquired, including loans acquired in a business combination, are initially recorded at fair value with no valuation allowance. Acquired loans are segregated between those considered to be credit impaired and those deemed performing. To make this determination, management considers such factors as past due status, non-accrual status and credit risk ratings. The fair value of acquired performing loans is determined by discounting expected cash flows, both principal and interest, at prevailing market interest rates. The difference between the fair value and principal balances at acquisition date, the fair value discount, is accreted into interest income over the estimated life of each loan. Purchased credit impaired loans are those loans that showed evidence of deterioration of credit quality since origination and for which it is probable, at acquisition, that the Company will be unable to collect all amounts contractually owed. Their acquisition fair value, which includes a credit component at the acquisition date, was based on the estimate of cash flows, both principal and interest, expected to be collected or estimated collateral values if cash flows are not estimable, discounted at prevailing market rates of interest. The difference between the discounted cash flows expected at acquisition and the investment in the loan is recognized as interest income on a level-yield method over the life of the loan, unless management was unable to reasonably forecast cash flows in which case the loans were placed on nonaccrual. Contractually required payments for interest and principal that exceed the cash flows expected at acquisition are not recognized as a yield adjustment. Increases in expected cash flows subsequent to the initial investment are recognized prospectively through adjustment of the yield on the loan over its remaining life. Decreases in expected cash flows subsequent to acquisition are recognized as impairment. Valuation allowances on these impaired loans reflect only losses incurred after the acquisition. The carrying amount of purchased credit impaired loans at June 30, 2015 and 2014, and December 31, 2014 was $1,123,000, $2,519,000 and $2,151,000, respectively, compared to a contractual balance of $1,648,000, $3,754,000, and $3,275,000, respectively. Other purchased credit impaired loan disclosures were omitted due to immateriality. Loans held-for-investment by class of financing receivables are as follows (in thousands): June 30, December 31, 2015 2014 2014 Commercial $ 649,909 $ 617,925 $ 639,954 Agricultural 92,317 75,133 105,694 Real estate 1,838,488 1,733,604 1,822,854 Consumer 361,510 346,412 360,686 Total loans held-for-investment $ 2,942,224 $ 2,773,074 $ 2,929,188 Loans held for sale totaled $25,544,000, $13,570,000 and $8,803,000 at June 30, 2015 and 2014, and December 31, 2014, respectively, which were recorded at cost as fair value approximated cost. The Company’s non-accrual loans, loans still accruing and past due 90 days or more and restructured loans are as follows (in thousands): June 30, December 31, 2015 2014 2014 Non-accrual loans* $ 16,854 $ 23,565 $ 20,194 Loans still accruing and past due 90 days or more 64 123 261 Troubled debt restructured loans** 172 — 226 Total $ 17,090 $ 23,688 $ 20,681 * Includes $1,123,000, $2,519,000 and $2,151,000 of purchased credit impaired loans as of June 30, 2015 and 2014, and December 31, 2014, respectively. ** Troubled debt restructured loans of $6,936,000, $10,810,000 and $9,073,000, whose interest collection, after considering economic and business conditions and collection efforts, is doubtful are included in non-accrual loans at June 30, 2015 and 2014, and December 31, 2014, respectively. The Company’s recorded investment in impaired loans and the related valuation allowance are as follows (in thousands): June 30, 2015 June 30, 2014 December 31, 2014 Recorded Valuation Recorded Valuation Recorded Valuation $ 16,854 $ 3,866 $ 23,565 $ 4,883 $ 20,194 $ 4,213 The average recorded investment in impaired loans for the three and six months ended June 30, 2015 and the year ended December 31, 2014 was approximately $16,877,000, $18,387,000 and $24,497,000, respectively. The Company had $18,135,000, $26,030,000 and $21,716,000 in non-accrual, past due 90 days or more and still accruing and restructured loans and foreclosed assets at June 30, 2015 and 2014, and December 31, 2014, respectively. Non-accrual loans at June 30, 2015 and 2014, and December 31, 2014, consisted of the following by class of financing receivables (in thousands): June 30, December 31, 2015 2014 2014 Commercial $ 3,606 $ 3,640 $ 3,193 Agricultural 118 109 165 Real estate 12,570 19,027 16,218 Consumer 560 789 618 Total $ 16,854 $ 23,565 $ 20,194 No significant additional funds are committed to be advanced in connection with impaired loans as of June 30, 2015. The Company’s impaired loans and related allowance as of June 30, 2015 and 2014, and December 31, 2014, are summarized in the following tables by class of financing receivables (in thousands). No interest income was recognized on impaired loans subsequent to their classification as impaired. June 30, 2015 Unpaid Recorded Recorded Total Related Year-to-Date Three-month Commercial $ 4,168 $ 263 $ 3,343 $ 3,606 $ 1,168 $ 3,717 $ 3,298 Agricultural 163 — 118 118 87 148 136 Real Estate 18,711 2,921 9,649 12,570 2,506 13,817 12,876 Consumer 784 367 193 560 105 705 567 Total $ 23,826 $ 3,551 $ 13,303 $ 16,854 $ 3,866 $ 18,387 $ 16,877 * Includes $1,123,000 of purchased credit impaired loans. June 30, 2014 Unpaid Recorded Recorded Total Related Year-to-Date Three-month Commercial $ 4,095 $ 271 $ 3,369 $ 3,640 $ 1,161 $ 4,083 $ 3,224 Agricultural 121 — 109 109 41 118 101 Real Estate 24,619 5,626 13,401 19,027 3,497 21,442 20,920 Consumer 960 442 347 789 184 879 759 Total $ 29,795 $ 6,339 $ 17,226 $ 23,565 $ 4,883 $ 26,522 $ 25,004 * Includes $2,519,000 of purchased credit impaired loans. December 31, 2014 Unpaid Recorded Recorded Total Related Average Commercial $ 3,749 $ 287 $ 2,906 $ 3,193 $ 1,171 $ 3,698 Agricultural 177 — 165 165 57 179 Real Estate 22,177 4,859 11,359 16,218 2,867 19,837 Consumer 838 420 198 618 118 783 Total $ 26,941 $ 5,566 $ 14,628 $ 20,194 $ 4,213 $ 24,497 * Includes $2,151,000 of purchased credit impaired loans. The Company recognized interest income on impaired loans prior to being classified as impaired of approximately $162,000 during the year ended December 31, 2014. Such amounts for the three-month and six-month periods ended June 30, 2015 and 2014 were not significant. From a credit risk standpoint, the Company rates its loans in one of four categories: (i) pass, (ii) special mention, (iii) substandard or (iv) doubtful. Loans rated as loss are charged-off. The ratings of loans reflect a judgment about the risks of default and loss associated with the loan. The Company reviews the ratings on our credits as part of our on-going monitoring of the credit quality of our loan portfolio. Ratings are adjusted to reflect the degree of risk and loss that are felt to be inherent in each credit as of each reporting period. Our methodology is structured so that specific allocations are increased in accordance with deterioration in credit quality (and a corresponding increase in risk and loss) or decreased in accordance with improvement in credit quality (and a corresponding decrease in risk and loss). Credits rated special mention show clear signs of financial weakness or deterioration in credit worthiness, however, such concerns are not so pronounced that the Company generally expects to experience significant loss within the short-term. Such credits typically maintain the ability to perform within standard credit terms and credit exposure is not as prominent as credits rated more harshly. Credits rated substandard are those in which the normal repayment of principal and interest may be, or has been, jeopardized by reason of adverse trends or developments of a financial, managerial, economic or political nature, or important weaknesses exist in collateral. A protracted workout on these credits is a distinct possibility. Prompt corrective action is therefore required to strengthen the Company’s position, and/or to reduce exposure and to assure that adequate remedial measures are taken by the borrower. Credit exposure becomes more likely in such credits and a serious evaluation of the secondary support to the credit is performed. Credits rated doubtful are those in which full collection of principal appears highly questionable, and which some degree of loss is anticipated, even though the ultimate amount of loss may not yet be certain and/or other factors exist which could affect collection of debt. Based upon available information, positive action by the Company is required to avert or minimize loss. Credits rated doubtful are generally also placed on non-accrual. The following summarizes the Company’s internal ratings of its loans held-for-investment by class of financing receivables and portfolio segments, which are the same, at June 30, 2015 and 2014, and December 31, 2014 (in thousands): June 30, 2015 Pass Special Substandard Doubtful Total Commercial $ 611,071 $ 25,438 $ 13,400 $ — $ 649,909 Agricultural 91,657 159 501 — 92,317 Real Estate 1,783,633 21,504 33,308 43 1,838,488 Consumer 360,094 308 1,108 — 361,510 Total $ 2,846,455 $ 47,409 $ 48,317 $ 43 $ 2,942,224 June 30, 2014 Pass Special Substandard Doubtful Total Commercial $ 605,163 $ 3,678 $ 9,084 $ — $ 617,925 Agricultural 74,734 102 296 1 75,133 Real Estate 1,668,844 16,628 48,001 131 1,733,604 Consumer 344,403 522 1,483 4 346,412 Total $ 2,693,144 $ 20,930 $ 58,864 $ 136 $ 2,773,074 December 31, 2014 Pass Special Substandard Doubtful Total Commercial $ 626,266 $ 3,853 $ 9,835 $ — $ 639,954 Agricultural 105,101 91 502 — 105,694 Real Estate 1,765,886 15,106 41,722 140 1,822,854 Consumer 358,953 403 1,329 1 360,686 Total $ 2,856,206 $ 19,453 $ 53,388 $ 141 $ 2,929,188 At June 30, 2015 and 2014, and December 31, 2014, the Company’s past due loans are as follows (in thousands): June 30, 2015 15-59 60-89 Greater Total Current Total Loans 90 Days Commercial $ 7,854 $ 38 $ 12 $ 7,904 $ 642,005 $ 649,909 $ — Agricultural 270 — — 270 92,047 92,317 — Real Estate 13,458 1,255 1,933 16,646 1,821,842 1,838,488 47 Consumer 1,507 342 98 1,947 359,563 361,510 17 Total $ 23,089 $ 1,635 $ 2,043 $ 26,767 $ 2,915,457 $ 2,942,224 $ 64 June 30, 2014 15-59 60-89 Greater Total Current Total Loans 90 Days Commercial $ 7,290 $ 51 $ 248 $ 7,589 $ 610,336 $ 617,925 $ 23 Agricultural 134 14 — 148 74,985 75,133 — Real Estate 16,781 823 1,973 19,577 1,714,027 1,733,604 83 Consumer 1,470 443 153 2,066 344,346 346,412 17 Total $ 25,675 $ 1,331 $ 2,374 $ 29,380 $ 2,743,694 $ 2,773,074 $ 123 December 31, 2014 15-59 60-89 Greater Total Current Total Loans 90 Days Commercial $ 4,611 $ 94 $ 175 $ 4,880 $ 635,074 $ 639,954 $ 24 Agricultural 437 42 — 479 105,215 105,694 — Real Estate 12,002 707 1,868 14,577 1,808,277 1,822,854 207 Consumer 2,322 496 134 2,952 357,734 360,686 30 Total $ 19,372 $ 1,339 $ 2,177 $ 22,888 $ 2,906,300 $ 2,929,188 $ 261 * The Company monitors commercial, agricultural and real estate loans after such loans are 15 days past due. Consumer loans are monitored after such loans are 30 days past due. The following table details the allowance for loan losses at June 30, 2015 and 2014, and December 31, 2014 by portfolio segment (in thousands). There were no allowances for purchased credit impaired loans at June 30, 2015 and 2014, or December 31, 2014. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. June 30, 2015 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,168 $ 87 $ 2,506 $ 105 $ 3,866 Loans collectively evaluated for impairment 10,288 305 21,836 2,704 35,133 Total $ 11,456 $ 392 $ 24,342 $ 2,809 $ 38,999 June 30, 2014 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,161 $ 41 $ 3,497 $ 184 $ 4,883 Loans collectively evaluated for impairment 5,700 323 23,064 1,922 31,009 Total $ 6,861 $ 364 $ 26,561 $ 2,106 $ 35,892 December 31, 2014 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,171 $ 57 $ 2,867 $ 118 $ 4,213 Loans collectively evaluated for impairment 6,819 470 23,790 1,532 32,611 Total $ 7,990 $ 527 $ 26,657 $ 1,650 $ 36,824 The tables above for 2014 have been changed to conform to the 2015 presentation. Changes in the allowance for loan losses for the three and six months ended June 30, 2015 and 2014 are summarized as follows by portfolio segment (in thousands): Three months ended June 30, 2015 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 10,375 $ 473 $ 25,239 $ 1,741 $ 37,828 Provision for loan losses 1,324 (27 ) (1,048 ) 1,305 1,554 Recoveries 117 — 302 141 560 Charge-offs (360 ) (54 ) (151 ) (378 ) (943 ) Ending balance $ 11,456 $ 392 $ 24,342 $ 2,809 $ 38,999 Three months ended June 30, 2014 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 6,645 $ 285 $ 25,629 $ 2,134 $ 34,693 Provision for loan losses 219 78 835 (8 ) 1,124 Recoveries 65 1 132 178 376 Charge-offs (68 ) — (35 ) (198 ) (301 ) Ending balance $ 6,861 $ 364 $ 26,561 $ 2,106 $ 35,892 Six months ended June 30, 2015 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 7,990 $ 527 $ 26,657 $ 1,650 $ 36,824 Provision for loan losses 3,789 (59 ) (2,515 ) 1,629 2,844 Recoveries 197 2 373 212 784 Charge-offs (520 ) (78 ) (173 ) (682 ) (1,453 ) Ending balance $ 11,456 $ 392 $ 24,342 $ 2,809 $ 38,999 Six months ended June 30, 2014 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 6,440 $ 383 $ 24,940 $ 2,137 $ 33,900 Provision for loan losses 554 (21 ) 2,068 213 2,814 Recoveries 154 3 319 300 776 Charge-offs (287 ) (1 ) (766 ) (544 ) (1,598 ) Ending balance $ 6,861 $ 364 $ 26,561 $ 2,106 $ 35,892 The Company’s recorded investment in loans as of June 30, 2015 and 2014, and December 31, 2014 related to the balance in the allowance for loan losses on the basis of the Company’s impairment methodology was as follows (in thousands). Purchased credit impaired loans of $1,123,000, $2,519,000 and $2,151,000 at June 30, 2015 and 2014, and December 31, 2014, respectively, are included in loans individually evaluated for impairment. June 30, 2015 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 3,606 $ 118 $ 12,570 $ 560 $ 16,854 Loans collectively evaluated for impairment 646,303 92,199 1,825,918 360,950 2,925,370 Total $ 649,909 $ 92,317 $ 1,838,488 $ 361,510 $ 2,942,224 June 30, 2014 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 3,640 $ 109 $ 19,027 $ 789 $ 23,565 Loans collectively evaluated for impairment 614,285 75,024 1,714,577 345,623 2,749,509 Total $ 617,925 $ 75,133 $ 1,733,604 $ 346,412 $ 2,773,074 December 31, 2014 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 3,193 $ 165 $ 16,218 $ 618 $ 20,194 Loans collectively evaluated for impairment 636,761 105,529 1,806,636 360,068 2,908,994 Total $ 639,954 $ 105,694 $ 1,822,854 $ 360,686 $ 2,929,188 The tables above for 2014 have been changed to conform to the 2015 presentation. The Company’s loans that were modified in the three and six months ended June 30, 2015 and 2014 and considered troubled debt restructurings are as follows (in thousands): Three Months Ended June 30, 2015 Six Months Ended June 30, 2015 Number Pre- Post- Number Pre- Post- Commercial 2 $ 74 $ 74 2 $ 74 $ 74 Agricultural — — — 3 128 128 Real Estate 2 336 336 2 336 336 Consumer 2 4 4 3 28 28 Total 6 $ 414 $ 414 10 $ 566 $ 566 Three Months Ended June 30, 2014 Six Months Ended June 30, 2014 Number Pre- Combined Number Pre- Combined Commercial 1 $ 302 $ 302 5 $ 399 $ 399 Agricultural 1 39 39 1 39 39 Real Estate 3 514 514 4 590 590 Consumer — — — 3 11 11 Total 5 $ 855 $ 855 13 $ 1,039 $ 1,039 The balances below provide information as to how the loans were modified as troubled debt restructured loans during the three and six months ended June 30, 2015 and 2014 (in thousands): Three Months Ended June 30, 2015 Six Months Ended June 30, 2015 Adjusted Extended Combined Adjusted Extended Combined Commercial $ — $ 74 $ — $ — $ 74 $ — Agricultural — — — — 128 — Real Estate 257 — 79 257 — 79 Consumer — 4 — — 4 24 Total $ 257 $ 78 $ 79 $ 257 $ 206 $ 103 Three Months Ended June 30, 2014 Six Months Ended June 30, 2014 Adjusted Extended Combined Adjusted Extended Combined Commercial $ — $ — $ 302 $ — $ 97 $ 302 Agricultural — — 39 — — 39 Real Estate — 42 472 — 118 472 Consumer — — — — 8 3 Total $ — $ 42 $ 813 $ — $ 223 $ 816 During the three months ended June 30, 2014, one loan was modified as troubled debt restructured loan within the previous 12 months and for which there was a payment default. There were no such defaults in the three months ended June 30, 2015. During the six months ended June 30, 2015 and 2014, one loan was modified in each six-month period as a troubled debt restructured loan within the previous 12 months and for which there was a payment default. A default for purposes of this disclosure is a troubled debt restructured loan in which the borrower is 90 days past due or more or results in the foreclosure and repossession of the applicable collateral. The loans with payment default are as follows (dollars in thousands): Six Months Ended June 30, 2015 Number Balance Commercial 1 $ 111 Agriculture — — Real Estate — — Consumer — — Total 1 $ 111 Three Months Ended June 30, 2014 Six Months Ended June 30, 2014 Number Balance Number Balance Commercial — $ — — $ — Agriculture — — — — Real Estate — — — — Consumer 1 32 1 32 Total 1 $ 32 1 $ 32 As of June 30, 2015, the Company has no commitments to lend additional funds to loan customers whose terms have been modified in troubled debt restructurings. Our subsidiary bank has established a line of credit with the Federal Home Loan Bank of Dallas (FHLB) to provide liquidity and meet pledging requirements for those customers eligible to have securities pledged to secure certain uninsured deposits. At June 30, 2015, $1,720,486,000 in loans held by our bank subsidiary were subject to blanket liens as security for this line of credit. At June 30, 2015, $265,036,000 in advances and $5,000,000 in letters of credit were outstanding under this line of credit. The letters of credit were pledged as collateral for public funds held by our bank subsidiary.

Short-Term Borrowings

Short-Term Borrowings	6 Months Ended
	Jun. 30, 2015
Debt Disclosure [Abstract]
Short-Term Borrowings	Note 6 – Short-Term Borrowings Short-Term borrowings at June 30, 2015 and 2014, and December 31, 2014 consisted of the following (dollars in thousands): June 30, December 31, 2015 2014 2014 Securities sold under agreements with customers to repurchase $ 346,369 $ 312,893 $ 357,400 Federal funds purchased 9,750 10,625 8,700 Advances from Federal Home Loan Bank of Dallas 265,036 111,065 1,010 Total $ 621,155 $ 434,583 $ 367,110 Securities sold under repurchase agreements are generally with significant customers of the Company that require short-term liquidity for their funds for which the Company pledges certain securities that have a fair value equal to at least the amount of the short-term borrowings. The agreements mature daily and therefore the risk arising from a decline in the fair value of the collateral pledged is minimal. The securities pledged are mortgage-backed securities. These agreements do not include “right of set-off” provisions and therefore the Company does not offset such agreements for financial reporting purposes.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Note 7 - Income Taxes Income tax expense was $8,080,000 for the second quarter of 2015 as compared to $6,758,000 for the same period in 2014. The Company’s effective tax rates on pretax income were 24.20% and 24.17% for the second quarters of 2015 and 2014, respectively. Income tax expense was $15,845,000 for the six months ended June 2015 as compared to $13,863,000 for the same period in 2014. The Company’s effective tax rates on pretax income were 24.32% and 24.15% for the six months ended June 2015 and 2014, respectively. The effective tax rates differ from the statutory federal tax rate of 35% primarily due to tax exempt interest income earned on certain investment securities and loans and the deductibility of dividends paid to our employee stock ownership plan.

Stock Based Compensation

Stock Based Compensation	6 Months Ended
	Jun. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Based Compensation	Note 8 - Stock Based Compensation The Company grants incentive stock options for a fixed number of shares with an exercise price equal to the fair value of the shares at the date of grant to employees. Through June 30, 2015, no options have been granted in 2015 and no options were granted in 2014. The Company recorded stock option expense totaling $182,000 and $212,000 for the three months ended June 30, 2015 and 2014, respectively. The Company recorded stock option expense totaling $360,000 and $357,000 for the six months ended June 30, 2015 and 2014, respectively. The additional disclosure requirements under authoritative accounting guidance have been omitted due to immateriality. On April 28, 2015, shareholders of the Company approved a restricted stock plan for selected employees, officers, non-employee directors and consultants. On July 21, 2015, 7,070 shares were granted to the ten non-employee directors. Total value of these shares totaled $250,000 and will be expensed over the period from grant date to April 26, 2016, the next scheduled annual shareholders’ meeting whereby the directors term will expire.

Pension Plan

Pension Plan	6 Months Ended
	Jun. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Pension Plan	Note 9 - Pension Plan The Company’s defined benefit pension plan was frozen effective January 1, 2004, whereby no new participants will be added to the plan and no additional years of service will accrue to participants, unless the pension plan is reinstated at a future date. The pension plan covered substantially all of the Company’s employees at the time. The benefits for each employee were based on years of service and a percentage of the employee’s qualifying compensation during the final years of employment. The Company’s funding policy was and is to contribute annually the amount necessary to satisfy the Internal Revenue Service’s funding standards. Contributions to the pension plan, prior to freezing the plan, were intended to provide not only for benefits attributed to service to date but also for those expected to be earned in the future. As a result of the Pension Protection Act of 2006 (the “Protection Act”), the Company will be required to contribute amounts in future years to fund any shortfalls. The Company has evaluated the provisions of the Protection Act as well as the Internal Revenue Service’s funding standards to develop a plan for funding in future years. The Company made a contribution totaling $250,000 in 2014 and has to date made no contributions in 2015. During the fourth quarter of 2014, as permitted by the Internal Revenue Service, the Company offered settlement of a portion of its pension obligations to those plan participants who no longer were employed by the Company. As a result of the partial settlement of the plan, the Company recognized in the fourth quarter of 2014 $2,909,000, in pension expense, before income tax. The effect of this transaction was relatively neutral to shareholders’ equity since the recorded pension obligation associated with the plan participants who accepted the settlement closely approximated the amount offered to such plan participants and the amount recognized in pension expense had been previously recognized as unrealized losses in other comprehensive earnings. As a result, the Company paid $10,626,000 out of pension plan assets, or approximately 43% of the total outstanding obligation balance, to plan participants and the number of participants was reduced by 335, or 44%. The Company’s investment risk and administrative expense associated with the Company’s pension plan should be significantly reduced going forward. Net periodic benefit costs totaling $74,000 and $84,000 were recorded for the three months ended June 30, 2015 and 2014, respectively. Net periodic benefit costs totaling $149,000 and $214,000 were recorded for the six months ended June 30, 2015 and 2014, respectively.

Fair Value Disclosures

Fair Value Disclosures	6 Months Ended
	Jun. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value Disclosures	Note 10 - Fair Value Disclosures The authoritative accounting guidance for fair value measurements 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. A fair value measurement assumes that the transaction to sell the asset or transfer the liability occurs in the principal market for the asset or liability or, in the absence of a principal market, the most advantageous market for the asset or liability. The price in the principal (or most advantageous) market used to measure the fair value of the asset or liability shall not be adjusted for transaction costs. An orderly transaction is a transaction that assumes exposure to the market for a period prior to the measurement date to allow for marketing activities that are usual and customary for transactions involving such assets and liabilities; it is not a forced transaction. Market participants are buyers and sellers in the principal market that are (i) independent, (ii) knowledgeable, (iii) able to transact, and (iv) willing to transact. The authoritative accounting guidance requires the use of valuation techniques that are consistent with the market approach, the income approach and/or the cost approach. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets and liabilities. The income approach uses valuation techniques to convert future amounts, such as cash flows or earnings, to a single present amount on a discounted basis. The cost approach is based on the amount that currently would be required to replace the service capacity of an asset (replacement costs). Valuation techniques should be consistently applied. Inputs to valuation techniques refer to the assumptions that market participants would use in pricing the asset or liability. Inputs may be observable, meaning those that reflect the assumptions market participants would use in pricing the asset or liability developed based on market data obtained from independent sources, or unobservable, meaning those that reflect the reporting entity’s own assumptions about the assumptions market participants would use in pricing the asset or liability developed based on the best information available in the circumstances. In that regard, the authoritative guidance establishes a fair value hierarchy for valuation inputs that gives the highest priority to quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. The fair value hierarchy is as follows: • Level 1 Inputs – Unadjusted quoted prices in active markets for identical assets or liabilities that the reporting entity has the ability to access at the measurement date. • Level 2 Inputs – Inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. These include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (for example, interest rates, volatilities, prepayment speeds, loss severities, credit risks and default rates) or inputs that are derived principally from or corroborated by observable market data by correlation or other means. • Level 3 Inputs – Significant unobservable inputs that reflect an entity’s own assumptions that market participants would use in pricing the assets or liabilities. A description of the valuation methodologies used for assets and liabilities measured at fair value, as well as the general classification of such instruments pursuant to the valuation hierarchy, is set forth below. In general, fair value is based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. While management believes the Company’s valuation methodologies are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different estimate of fair value at the reporting date. Securities classified as available-for-sale and trading are reported at fair value utilizing Level 1 and Level 2 inputs. For these securities, the Company obtains fair value measurements from an independent pricing service. The fair value measurements consider observable data that may include market spreads, cash flows, the United States Treasury yield curve, live trading levels, trade execution data, dealer quotes, market consensus prepayments speeds, credit information and the security’s terms and conditions, among other items. There were no transfers between Level 2 and Level 3 during the three and six months ended June 30, 2015 or 2014. The following table summarizes financial assets and financial liabilities measured at fair value on a recurring basis as of June 30, 2015 and 2014, and December 31, 2014, respectively, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value (dollars in thousands): June 30, 2015 Level 1 Level 2 Level 3 Total Fair Available-for-sale investment securities: U.S. Treasury securities $ 10,936 $ — $ — $ 10,936 Obligations of U. S. government sponsored-enterprises and agencies — 165,336 — 165,336 Obligations of states and political subdivisions — 1,384,246 — 1,384,246 Corporate bonds — 92,188 — 92,188 Residential mortgage-backed securities — 868,091 — 868,091 Commercial mortgage-backed securities — 203,396 — 203,396 Other securities 4,920 — — 4,920 Total $ 15,856 $ 2,713,257 $ — $ 2,729,113 June 30, 2014 Level 1 Level 2 Level 3 Total Fair Available-for-sale investment securities: Obligations of U. S. government sponsored-enterprises and agencies $ — $ 120,117 $ — $ 120,117 Obligations of states and political subdivisions — 1,074,658 — 1,074,658 Corporate bonds — 95,940 — 95,940 Residential mortgage-backed securities — 745,473 — 745,473 Commercial mortgage-backed securities — 132,840 — 132,840 Other securities 4,800 — — 4,800 Total $ 4,800 $ 2,169,028 $ — $ 2,173,828 December 31, 2014 Level 1 Level 2 Level 3 Total Fair Available-for-sale investment securities: U.S. Treasury securities $ 520 $ — $ — $ 520 Obligations of U. S. government sponsored-enterprises and agencies — 129,755 — 129,755 Obligations of states and political subdivisions — 1,167,628 — 1,167,628 Corporate bonds — 94,065 — 94,065 Residential mortgage-backed securities — 885,211 — 885,211 Commercial mortgage-backed securities — 133,984 — 133,984 Other securities 4,693 — — 4,693 Total $ 5,213 $ 2,410,643 $ — $ 2,415,856 The tables above for 2014 has been changed to conform to the 2015 presentation. Certain financial assets and financial liabilities are measured at fair value on a nonrecurring basis, that is, the instruments 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). Financial assets and financial liabilities measured at fair value on a non-recurring basis include the following at June 30, 2015: Impaired Loans – Impaired loans are reported at the fair value of the underlying collateral if repayment is expected solely from the collateral. Collateral values are estimated using Level 2 inputs based on observable market data. At June 30, 2015, impaired loans with a carrying value of $16,854,000 were reduced by specific valuation reserves totaling $3,866,000 resulting in a net fair value of $12,988,000. Loans Held-for-Sale – Loans held-for-sale are reported at the lower of cost or fair value. In determining whether the fair value of loans held-for-sale is less than cost when quoted market prices are not available, the Company considers investor commitments/contracts. These loans are considered Level 2 of the fair value hierarchy. At June 30, 2015, the Company’s mortgage loans held-for-sale were recorded at cost as fair value approximated cost. Certain non-financial assets and non-financial liabilities measured at fair value on a non-recurring basis include other real estate owned, goodwill and other intangible assets and other non-financial long-lived assets. Non-financial assets measured at fair value on a non-recurring basis during the three and six months ended June 30, 2015 and 2014 include other real estate owned which, subsequent to their initial transfer to other real estate owned from loans, were re-measured at fair value through a write-down included in gain (loss) on sale of foreclosed assets. During the reported periods, all fair value measurements for foreclosed assets utilized Level 2 inputs based on observable market data, generally third-party appraisals, or Level 3 inputs based on customized discounting criteria. These appraisals are evaluated individually and discounted as necessary due to the age of the appraisal, lack of comparable sales, expected holding periods of property or special use type of the property. Such discounts vary by appraisal based on the above factors but generally range from 5% to 25% of the appraised value. Reevaluation of other real estate owned is performed at least annually as required by regulatory guidelines or more often if particular circumstances arise. The following table presents other real estate owned that were re-measured subsequent to their initial transfer to other real estate owned (dollars in thousands): Three Months Ended 2015 2014 Carrying value of other real estate owned prior to re-measurement $ 341 $ 708 Write-downs included in gain (loss) on sale of other real estate owned (85 ) (89 ) Fair value $ 256 $ 619 Six Months Ended 2015 2014 Carrying value of other real estate owned prior to re-measurement $ 351 $ 708 Write-downs included in gain (loss) on sale of other real estate owned (95 ) (89 ) Fair value $ 256 $ 619 At June 30, 2015 and 2014, and December 31, 2014, other real estate owned totaled $635,000, $2,208,000 and $943,000, respectively. The Company is required under current authoritative accounting guidance to disclose the estimated fair value of their financial instrument assets and liabilities including those subject to the requirements discussed above. For the Company, as for most financial institutions, substantially all of its assets and liabilities are considered financial instruments. Many of the Company’s financial instruments, however, lack an available trading market as characterized by a willing buyer and willing seller engaging in an exchange transaction. The estimated fair value amounts of financial instruments have been determined by the Company using available market information and appropriate valuation methodologies. However, considerable judgment is required to interpret data to develop the estimates of fair value. Accordingly, the estimates presented herein are not necessarily indicative of the amounts the Company could realize in a current market exchange. The use of different market assumptions and/or estimation methodologies may have a material effect on the estimated fair value amounts. In addition, reasonable comparability between financial institutions may not be likely due to the wide range of permitted valuation techniques and numerous estimates that must be made given the absence of active secondary markets for many of the financial instruments. This lack of uniform valuation methodologies also introduces a greater degree of subjectivity to these estimated fair values. Cash and due from banks, federal funds sold, interest-bearing deposits and time deposits in banks and accrued interest receivable and payable are liquid in nature and considered Levels 1 or 2 of the fair value hierarchy. Financial instruments with stated maturities have been valued using a present value discounted cash flow with a discount rate approximating current market for similar assets and liabilities and are considered Levels 2 and 3 of the fair value hierarchy. Financial instrument liabilities with no stated maturities have an estimated fair value equal to both the amount payable on demand and the carrying value and are considered Level 1 of the fair value hierarchy. The carrying value and the estimated fair value of the Company’s contractual off-balance-sheet unfunded lines of credit, loan commitments and letters of credit, which are generally priced at market at the time of funding, are not material. The estimated fair values and carrying values of all financial instruments under current authoritative guidance at June 30, 2015 and 2014, and December 31, 2014, were as follows (in thousands): June 30, June 30, December 31, 2015 2014 2014 Carrying Estimated Carrying Estimated Carrying Estimated Fair Value Value Fair Value Value Fair Value Value Fair Value Hierarchy Cash and due from banks $ 149,524 $ 149,524 $ 166,237 $ 166,237 $ 190,387 $ 190,387 Level 1 Federal funds sold 5,720 5,720 3,110 3,110 8,760 8,760 Level 1 Interest-bearing deposits in banks 18,179 18,179 68,331 68,331 54,324 54,324 Level 1 Interest-bearing time deposits in banks 5,456 5,466 24,188 24,266 17,002 17,032 Level 2 Available-for-sale securities 2,729,113 2,729,113 2,173,828 2,173,828 2,415,856 2,415,856 Levels 1 and 2 Held-to-maturity securities 295 301 568 576 441 447 Level 2 Loans 2,928,769 2,935,344 2,750,752 2,764,118 2,901,167 2,906,399 Level 3 Accrued interest receivable 32,003 32,003 27,583 27,583 28,998 28,998 Level 2 Deposits with stated maturities 598,404 600,093 692,937 695,006 648,992 650,893 Level 2 Deposits with no stated maturities 4,129,015 4,129,015 3,625,521 3,625,521 4,101,263 4,101,263 Level 1 Short-term borrowings 621,155 621,155 434,583 434,583 367,110 367,110 Level 2 Accrued interest payable 242 242 291 291 237 237 Level 2

Recently Issued Authoritative A

Recently Issued Authoritative Accounting Guidance	6 Months Ended
	Jun. 30, 2015
Accounting Changes and Error Corrections [Abstract]
Recently Issued Authoritative Accounting Guidance	Note 11 - Recently Issued Authoritative Accounting Guidance In 2014, the Financial Accounting Standards Board (the “FASB”) amended its authoritative guidance related to residential real estate to clarify that an in substance repossession or foreclosure occurs, and a creditor is considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan, upon either (1) the creditor obtaining legal title to the residential real estate property upon completion of a foreclosure or (2) the borrower conveying all interest in the residential real estate property to the creditor to satisfy that loan through completion of a deed in lieu of foreclosure or through a similar legal agreement. Additionally, the amendment requires interim and annual disclosure of both (1) the amount of foreclosed residential real estate property held by the creditor and (2) the recorded investment in consumer mortgage loans collateralized by residential real estate property that are in the process of foreclosure according to local requirements of the applicable jurisdiction. The new guidance was effective for the Company on January 1, 2015 and did not have a significant impact to the Company’s financial statements. In 2014, the FASB issued a comprehensive new revenue recognition standard that will supersede substantially all existing revenue recognition guidance. The new standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under existing guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. The new standard will be effective in the first quarter of 2017. The Company is continuing to evaluate the potential impact to the Company’s financial statements. In 2014, the FASB amended its authoritative guidance related to repurchase-to-maturity transactions to require that repurchase-to-maturity transactions be accounted for as secured borrowings consistent with the accounting for other repurchase agreements. In addition, the amendment requires separate accounting for repurchase financings, which entails the transfer of a financial asset executed contemporaneously with a repurchase agreement with the same counterparty. The amendment requires entities to disclose certain information about transfers accounted for as sales in transactions that are economically similar to repurchase agreements. In addition, the amendment requires disclosures related to collateral, remaining contractual term and of the potential risks associated with repurchase agreements, securities lending transactions and repurchase-to-maturity transactions. The amendment was effective for the Company on January 1, 2015 and did not have a significant impact on the Company’s financial statements. In 2015, the FASB eliminated from U.S. GAAP the concept of extraordinary items, which, among other things, required an entity to show the item separately in the income statement, net of tax, after income from continuing operations. The new guidance is effective for the Company beginning January 1, 2016, though early adoption is permitted, and is not expected to have a significant impact on the Company’s financial statements.

Acquisition and Asset Purchase

Acquisition and Asset Purchase	6 Months Ended
	Jun. 30, 2015
Business Combinations [Abstract]
Acquisition and Asset Purchase	Note 12 – Acquisition and Asset Purchase On April 1, 2015, the Company announced that it has entered into a definitive agreement to acquire FBC Bancshares, Inc. and its wholly owned bank subsidiary, First Bank, N.A., Conroe, Texas for a purchase price of $61,000,000 to be paid in stock of the Company and calculated in accordance with the terms of the definitive agreement. At June 30, 2015, First Bank, N.A. had gross loans totaling $257,046,000, total deposits of $339,423,000 and total assets of $372,188,000. The acquisition was consummated on July 31, 2015. On April 8, 2015, the Company announced that it had entered into an asset purchase agreement with 4Trust Mortgage, Inc. for a cash purchase price of $1,900,000. The acquisition was finalized on May 31, 2015.

Interest-bearing Time Deposit22

Interest-bearing Time Deposits in Banks and Securities (Tables)	6 Months Ended
	Jun. 30, 2015
Cash and Cash Equivalents [Abstract]
Summary of Available-for-Sale Securities	A summary of the Company’s available-for-sale securities follows (in thousands): June 30, 2015 Amortized Gross Gross Estimated U.S. Treasury securities $ 10,864 $ 72 $ — $ 10,936 Obligations of U.S. government sponsored enterprises and agencies 164,351 985 — 165,336 Obligations of states and political subdivisions 1,340,163 49,483 (5,400 ) 1,384,246 Corporate bonds and other 94,485 2,623 — 97,108 Residential mortgage-backed securities 856,546 14,383 (2,838 ) 868,091 Commercial mortgage-backed securities 203,482 591 (677 ) 203,396 Total securities available-for-sale $ 2,669,891 $ 68,137 $ (8,915 ) $ 2,729,113 June 30, 2014 Amortized Gross Gross Estimated Obligations of U.S. government sponsored-enterprises and agencies $ 118,907 $ 1,210 $ — $ 120,117 Obligations of states and political subdivisions 1,027,503 49,171 (2,016 ) 1,074,658 Corporate bonds and other 97,119 3,621 — 100,740 Residential mortgage-backed securities 734,301 16,183 (5,011 ) 745,473 Commercial mortgage-backed securities 135,214 34 (2,408 ) 132,840 Total securities available-for-sale $ 2,113,044 $ 70,219 $ (9,435 ) $ 2,173,828 December 31, 2014 Amortized Gross Gross Estimated U.S. Treasury securities $ 518 $ 2 $ — $ 520 Obligations of U.S. government sponsored enterprises and agencies 128,919 864 (28 ) 129,755 Obligations of states and political subdivisions 1,107,795 60,083 (250 ) 1,167,628 Corporate bonds and other 95,864 2,894 — 98,758 Residential mortgage-backed securities 871,265 16,804 (2,858 ) 885,211 Commercial mortgage-backed securities 134,322 555 (893 ) 133,984 Total securities available-for-sale $ 2,338,683 $ 81,202 $ (4,029 ) $ 2,415,856
Amortized Cost and Estimated Fair Value of Available-for-Sale Securities	The amortized cost and estimated fair value of available-for-sale securities at June 30, 2015, by contractual and expected maturity, are shown below (in thousands): Amortized Estimated Due within one year $ 133,995 $ 135,181 Due after one year through five years 707,981 737,467 Due after five years through ten years 750,600 767,300 Due after ten years 17,287 17,678 Mortgage-backed securities 1,060,028 1,071,487 Total $ 2,669,891 $ 2,729,113
Continuous Unrealized-Loss Position of Available-for-Sale Securities	The following tables disclose, as of June 30, 2015 and 2014, and December 31, 2014, the Company’s investment securities that have been in a continuous unrealized-loss position for less than 12 months and for 12 or more months (in thousands): Less than 12 Months 12 Months or Longer Total June 30, 2015 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Obligations of states and political subdivisions $ 304,510 $ 5,335 $ 2,531 $ 65 $ 307,041 $ 5,400 Residential mortgage-backed securities 176,569 844 65,562 1,994 242,131 2,838 Commercial mortgage-backed securities 134,151 628 9,504 49 143,655 677 Total $ 615,230 $ 6,807 $ 77,597 $ 2,108 $ 692,827 $ 8,915 Less than 12 Months 12 Months or Longer Total June 30, 2014 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Obligations of states and political subdivisions $ 41,095 $ 160 $ 101,800 $ 1,856 $ 142,895 $ 2,016 Residential mortgage-backed securities 133,104 4,417 23,427 594 156,531 5,011 Commercial mortgage-backed securities 97,972 2,075 10,142 333 108,114 2,408 Total $ 272,171 $ 6,652 $ 135,369 $ 2,783 $ 407,540 $ 9,435 Less than 12 Months 12 Months or Longer Total December 31, 2014 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Obligations of U.S. government sponsored enterprises and agencies $ 25,480 $ 28 $ — $ — $ 25,480 $ 28 Obligations of states and political subdivisions 15,128 60 21,249 190 36,377 250 Residential mortgage-backed securities 76,350 148 128,368 2,710 204,718 2,858 Commercial mortgage-backed securities 48,399 273 55,065 620 103,464 893 Total $ 165,357 $ 509 $ 204,682 $ 3,520 $ 370,039 $ 4,029

Loans and Allowance for Loan 23

Loans and Allowance for Loan Losses (Tables)	6 Months Ended
	Jun. 30, 2015
Receivables [Abstract]
Loans Held-for-Investment by Class of Financing Receivables	Loans held-for-investment by class of financing receivables are as follows (in thousands): June 30, December 31, 2015 2014 2014 Commercial $ 649,909 $ 617,925 $ 639,954 Agricultural 92,317 75,133 105,694 Real estate 1,838,488 1,733,604 1,822,854 Consumer 361,510 346,412 360,686 Total loans held-for-investment $ 2,942,224 $ 2,773,074 $ 2,929,188
Non-Accrual Loans, Loans Still Accruing and Past Due 90 Days or More and Restructured Loans	The Company’s non-accrual loans, loans still accruing and past due 90 days or more and restructured loans are as follows (in thousands): June 30, December 31, 2015 2014 2014 Non-accrual loans* $ 16,854 $ 23,565 $ 20,194 Loans still accruing and past due 90 days or more 64 123 261 Troubled debt restructured loans** 172 — 226 Total $ 17,090 $ 23,688 $ 20,681 * Includes $1,123,000, $2,519,000 and $2,151,000 of purchased credit impaired loans as of June 30, 2015 and 2014, and December 31, 2014, respectively. ** Troubled debt restructured loans of $6,936,000, $10,810,000 and $9,073,000, whose interest collection, after considering economic and business conditions and collection efforts, is doubtful are included in non-accrual loans at June 30, 2015 and 2014, and December 31, 2014, respectively.
Recorded Investment in Impaired Loans and Related Valuation Allowance	The Company’s recorded investment in impaired loans and the related valuation allowance are as follows (in thousands): June 30, 2015 June 30, 2014 December 31, 2014 Recorded Valuation Recorded Valuation Recorded Valuation $ 16,854 $ 3,866 $ 23,565 $ 4,883 $ 20,194 $ 4,213
Schedule of Non-Accrual Loans	Non-accrual loans at June 30, 2015 and 2014, and December 31, 2014, consisted of the following by class of financing receivables (in thousands): June 30, December 31, 2015 2014 2014 Commercial $ 3,606 $ 3,640 $ 3,193 Agricultural 118 109 165 Real estate 12,570 19,027 16,218 Consumer 560 789 618 Total $ 16,854 $ 23,565 $ 20,194
Schedule of Impaired Loans and Related Allowance	The Company’s impaired loans and related allowance as of June 30, 2015 and 2014, and December 31, 2014, are summarized in the following tables by class of financing receivables (in thousands). No interest income was recognized on impaired loans subsequent to their classification as impaired. June 30, 2015 Unpaid Recorded Recorded Total Related Year-to-Date Three-month Commercial $ 4,168 $ 263 $ 3,343 $ 3,606 $ 1,168 $ 3,717 $ 3,298 Agricultural 163 — 118 118 87 148 136 Real Estate 18,711 2,921 9,649 12,570 2,506 13,817 12,876 Consumer 784 367 193 560 105 705 567 Total $ 23,826 $ 3,551 $ 13,303 $ 16,854 $ 3,866 $ 18,387 $ 16,877 * Includes $1,123,000 of purchased credit impaired loans. June 30, 2014 Unpaid Recorded Recorded Total Related Year-to-Date Three-month Commercial $ 4,095 $ 271 $ 3,369 $ 3,640 $ 1,161 $ 4,083 $ 3,224 Agricultural 121 — 109 109 41 118 101 Real Estate 24,619 5,626 13,401 19,027 3,497 21,442 20,920 Consumer 960 442 347 789 184 879 759 Total $ 29,795 $ 6,339 $ 17,226 $ 23,565 $ 4,883 $ 26,522 $ 25,004 * Includes $2,519,000 of purchased credit impaired loans. December 31, 2014 Unpaid Recorded Recorded Total Related Average Commercial $ 3,749 $ 287 $ 2,906 $ 3,193 $ 1,171 $ 3,698 Agricultural 177 — 165 165 57 179 Real Estate 22,177 4,859 11,359 16,218 2,867 19,837 Consumer 838 420 198 618 118 783 Total $ 26,941 $ 5,566 $ 14,628 $ 20,194 $ 4,213 $ 24,497 * Includes $2,151,000 of purchased credit impaired loans.
Schedule of Internal Ratings of Loans	The following summarizes the Company’s internal ratings of its loans held-for-investment by class of financing receivables and portfolio segments, which are the same, at June 30, 2015 and 2014, and December 31, 2014 (in thousands): June 30, 2015 Pass Special Substandard Doubtful Total Commercial $ 611,071 $ 25,438 $ 13,400 $ — $ 649,909 Agricultural 91,657 159 501 — 92,317 Real Estate 1,783,633 21,504 33,308 43 1,838,488 Consumer 360,094 308 1,108 — 361,510 Total $ 2,846,455 $ 47,409 $ 48,317 $ 43 $ 2,942,224 June 30, 2014 Pass Special Substandard Doubtful Total Commercial $ 605,163 $ 3,678 $ 9,084 $ — $ 617,925 Agricultural 74,734 102 296 1 75,133 Real Estate 1,668,844 16,628 48,001 131 1,733,604 Consumer 344,403 522 1,483 4 346,412 Total $ 2,693,144 $ 20,930 $ 58,864 $ 136 $ 2,773,074 December 31, 2014 Pass Special Substandard Doubtful Total Commercial $ 626,266 $ 3,853 $ 9,835 $ — $ 639,954 Agricultural 105,101 91 502 — 105,694 Real Estate 1,765,886 15,106 41,722 140 1,822,854 Consumer 358,953 403 1,329 1 360,686 Total $ 2,856,206 $ 19,453 $ 53,388 $ 141 $ 2,929,188
Schedule of Past Due Loans	At June 30, 2015 and 2014, and December 31, 2014, the Company’s past due loans are as follows (in thousands): June 30, 2015 15-59 60-89 Greater Total Current Total Loans 90 Days Commercial $ 7,854 $ 38 $ 12 $ 7,904 $ 642,005 $ 649,909 $ — Agricultural 270 — — 270 92,047 92,317 — Real Estate 13,458 1,255 1,933 16,646 1,821,842 1,838,488 47 Consumer 1,507 342 98 1,947 359,563 361,510 17 Total $ 23,089 $ 1,635 $ 2,043 $ 26,767 $ 2,915,457 $ 2,942,224 $ 64 June 30, 2014 15-59 60-89 Greater Total Current Total Loans 90 Days Commercial $ 7,290 $ 51 $ 248 $ 7,589 $ 610,336 $ 617,925 $ 23 Agricultural 134 14 — 148 74,985 75,133 — Real Estate 16,781 823 1,973 19,577 1,714,027 1,733,604 83 Consumer 1,470 443 153 2,066 344,346 346,412 17 Total $ 25,675 $ 1,331 $ 2,374 $ 29,380 $ 2,743,694 $ 2,773,074 $ 123 December 31, 2014 15-59 60-89 Greater Total Current Total Loans 90 Days Commercial $ 4,611 $ 94 $ 175 $ 4,880 $ 635,074 $ 639,954 $ 24 Agricultural 437 42 — 479 105,215 105,694 — Real Estate 12,002 707 1,868 14,577 1,808,277 1,822,854 207 Consumer 2,322 496 134 2,952 357,734 360,686 30 Total $ 19,372 $ 1,339 $ 2,177 $ 22,888 $ 2,906,300 $ 2,929,188 $ 261 * The Company monitors commercial, agricultural and real estate loans after such loans are 15 days past due. Consumer loans are monitored after such loans are 30 days past due.
Schedule of Allowance for Loan Losses by Portfolio Segment	The following table details the allowance for loan losses at June 30, 2015 and 2014, and December 31, 2014 by portfolio segment (in thousands). There were no allowances for purchased credit impaired loans at June 30, 2015 and 2014, or December 31, 2014. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. June 30, 2015 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,168 $ 87 $ 2,506 $ 105 $ 3,866 Loans collectively evaluated for impairment 10,288 305 21,836 2,704 35,133 Total $ 11,456 $ 392 $ 24,342 $ 2,809 $ 38,999 June 30, 2014 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,161 $ 41 $ 3,497 $ 184 $ 4,883 Loans collectively evaluated for impairment 5,700 323 23,064 1,922 31,009 Total $ 6,861 $ 364 $ 26,561 $ 2,106 $ 35,892 December 31, 2014 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,171 $ 57 $ 2,867 $ 118 $ 4,213 Loans collectively evaluated for impairment 6,819 470 23,790 1,532 32,611 Total $ 7,990 $ 527 $ 26,657 $ 1,650 $ 36,824
Changes in Allowance for Loan Losses	Changes in the allowance for loan losses for the three and six months ended June 30, 2015 and 2014 are summarized as follows by portfolio segment (in thousands): Three months ended June 30, 2015 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 10,375 $ 473 $ 25,239 $ 1,741 $ 37,828 Provision for loan losses 1,324 (27 ) (1,048 ) 1,305 1,554 Recoveries 117 — 302 141 560 Charge-offs (360 ) (54 ) (151 ) (378 ) (943 ) Ending balance $ 11,456 $ 392 $ 24,342 $ 2,809 $ 38,999 Three months ended June 30, 2014 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 6,645 $ 285 $ 25,629 $ 2,134 $ 34,693 Provision for loan losses 219 78 835 (8 ) 1,124 Recoveries 65 1 132 178 376 Charge-offs (68 ) — (35 ) (198 ) (301 ) Ending balance $ 6,861 $ 364 $ 26,561 $ 2,106 $ 35,892 Six months ended June 30, 2015 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 7,990 $ 527 $ 26,657 $ 1,650 $ 36,824 Provision for loan losses 3,789 (59 ) (2,515 ) 1,629 2,844 Recoveries 197 2 373 212 784 Charge-offs (520 ) (78 ) (173 ) (682 ) (1,453 ) Ending balance $ 11,456 $ 392 $ 24,342 $ 2,809 $ 38,999 Six months ended June 30, 2014 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 6,440 $ 383 $ 24,940 $ 2,137 $ 33,900 Provision for loan losses 554 (21 ) 2,068 213 2,814 Recoveries 154 3 319 300 776 Charge-offs (287 ) (1 ) (766 ) (544 ) (1,598 ) Ending balance $ 6,861 $ 364 $ 26,561 $ 2,106 $ 35,892
Schedule of Investment in Loans Related to Balance in Allowance for Loan Losses on Basis of Company's Impairment Methodology	The Company’s recorded investment in loans as of June 30, 2015 and 2014, and December 31, 2014 related to the balance in the allowance for loan losses on the basis of the Company’s impairment methodology was as follows (in thousands). Purchased credit impaired loans of $1,123,000, $2,519,000 and $2,151,000 at June 30, 2015 and 2014, and December 31, 2014, respectively, are included in loans individually evaluated for impairment. June 30, 2015 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 3,606 $ 118 $ 12,570 $ 560 $ 16,854 Loans collectively evaluated for impairment 646,303 92,199 1,825,918 360,950 2,925,370 Total $ 649,909 $ 92,317 $ 1,838,488 $ 361,510 $ 2,942,224 June 30, 2014 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 3,640 $ 109 $ 19,027 $ 789 $ 23,565 Loans collectively evaluated for impairment 614,285 75,024 1,714,577 345,623 2,749,509 Total $ 617,925 $ 75,133 $ 1,733,604 $ 346,412 $ 2,773,074 December 31, 2014 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 3,193 $ 165 $ 16,218 $ 618 $ 20,194 Loans collectively evaluated for impairment 636,761 105,529 1,806,636 360,068 2,908,994 Total $ 639,954 $ 105,694 $ 1,822,854 $ 360,686 $ 2,929,188
Schedule of Loans Modified and Considered Troubled Debt Restructurings	The Company’s loans that were modified in the three and six months ended June 30, 2015 and 2014 and considered troubled debt restructurings are as follows (in thousands): Three Months Ended June 30, 2015 Six Months Ended June 30, 2015 Number Pre- Post- Number Pre- Post- Commercial 2 $ 74 $ 74 2 $ 74 $ 74 Agricultural — — — 3 128 128 Real Estate 2 336 336 2 336 336 Consumer 2 4 4 3 28 28 Total 6 $ 414 $ 414 10 $ 566 $ 566 Three Months Ended June 30, 2014 Six Months Ended June 30, 2014 Number Pre- Combined Number Pre- Combined Commercial 1 $ 302 $ 302 5 $ 399 $ 399 Agricultural 1 39 39 1 39 39 Real Estate 3 514 514 4 590 590 Consumer — — — 3 11 11 Total 5 $ 855 $ 855 13 $ 1,039 $ 1,039
Schedule of How Loans Were Modified as Troubled Debt Restructured Loans	The balances below provide information as to how the loans were modified as troubled debt restructured loans during the three and six months ended June 30, 2015 and 2014 (in thousands): Three Months Ended June 30, 2015 Six Months Ended June 30, 2015 Adjusted Extended Combined Adjusted Extended Combined Commercial $ — $ 74 $ — $ — $ 74 $ — Agricultural — — — — 128 — Real Estate 257 — 79 257 — 79 Consumer — 4 — — 4 24 Total $ 257 $ 78 $ 79 $ 257 $ 206 $ 103 Three Months Ended June 30, 2014 Six Months Ended June 30, 2014 Adjusted Extended Combined Adjusted Extended Combined Commercial $ — $ — $ 302 $ — $ 97 $ 302 Agricultural — — 39 — — 39 Real Estate — 42 472 — 118 472 Consumer — — — — 8 3 Total $ — $ 42 $ 813 $ — $ 223 $ 816
Schedule of Troubled Debt Restructurings	The loans with payment default are as follows (dollars in thousands): Six Months Ended June 30, 2015 Number Balance Commercial 1 $ 111 Agriculture — — Real Estate — — Consumer — — Total 1 $ 111 Three Months Ended June 30, 2014 Six Months Ended June 30, 2014 Number Balance Number Balance Commercial — $ — — $ — Agriculture — — — — Real Estate — — — — Consumer 1 32 1 32 Total 1 $ 32 1 $ 32

Short-Term Borrowings (Tables)

Short-Term Borrowings (Tables)	6 Months Ended
	Jun. 30, 2015
Debt Disclosure [Abstract]
Schedule of Short-Term Borrowings	Short-Term borrowings at June 30, 2015 and 2014, and December 31, 2014 consisted of the following (dollars in thousands): June 30, December 31, 2015 2014 2014 Securities sold under agreements with customers to repurchase $ 346,369 $ 312,893 $ 357,400 Federal funds purchased 9,750 10,625 8,700 Advances from Federal Home Loan Bank of Dallas 265,036 111,065 1,010 Total $ 621,155 $ 434,583 $ 367,110

Fair Value Disclosures (Tables)

Fair Value Disclosures (Tables)	6 Months Ended
	Jun. 30, 2015
Fair Value Disclosures [Abstract]
Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis	The following table summarizes financial assets and financial liabilities measured at fair value on a recurring basis as of June 30, 2015 and 2014, and December 31, 2014, respectively, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value (dollars in thousands): June 30, 2015 Level 1 Level 2 Level 3 Total Fair Available-for-sale investment securities: U.S. Treasury securities $ 10,936 $ — $ — $ 10,936 Obligations of U. S. government sponsored-enterprises and agencies — 165,336 — 165,336 Obligations of states and political subdivisions — 1,384,246 — 1,384,246 Corporate bonds — 92,188 — 92,188 Residential mortgage-backed securities — 868,091 — 868,091 Commercial mortgage-backed securities — 203,396 — 203,396 Other securities 4,920 — — 4,920 Total $ 15,856 $ 2,713,257 $ — $ 2,729,113 June 30, 2014 Level 1 Level 2 Level 3 Total Fair Available-for-sale investment securities: Obligations of U. S. government sponsored-enterprises and agencies $ — $ 120,117 $ — $ 120,117 Obligations of states and political subdivisions — 1,074,658 — 1,074,658 Corporate bonds — 95,940 — 95,940 Residential mortgage-backed securities — 745,473 — 745,473 Commercial mortgage-backed securities — 132,840 — 132,840 Other securities 4,800 — — 4,800 Total $ 4,800 $ 2,169,028 $ — $ 2,173,828 December 31, 2014 Level 1 Level 2 Level 3 Total Fair Available-for-sale investment securities: U.S. Treasury securities $ 520 $ — $ — $ 520 Obligations of U. S. government sponsored-enterprises and agencies — 129,755 — 129,755 Obligations of states and political subdivisions — 1,167,628 — 1,167,628 Corporate bonds — 94,065 — 94,065 Residential mortgage-backed securities — 885,211 — 885,211 Commercial mortgage-backed securities — 133,984 — 133,984 Other securities 4,693 — — 4,693 Total $ 5,213 $ 2,410,643 $ — $ 2,415,856
Other Real Estate Owned	The following table presents other real estate owned that were re-measured subsequent to their initial transfer to other real estate owned (dollars in thousands): Three Months Ended 2015 2014 Carrying value of other real estate owned prior to re-measurement $ 341 $ 708 Write-downs included in gain (loss) on sale of other real estate owned (85 ) (89 ) Fair value $ 256 $ 619 Six Months Ended 2015 2014 Carrying value of other real estate owned prior to re-measurement $ 351 $ 708 Write-downs included in gain (loss) on sale of other real estate owned (95 ) (89 ) Fair value $ 256 $ 619
Schedule of Estimated Fair Values and Carrying Values of All Financial Instruments	The estimated fair values and carrying values of all financial instruments under current authoritative guidance at June 30, 2015 and 2014, and December 31, 2014, were as follows (in thousands): June 30, June 30, December 31, 2015 2014 2014 Carrying Estimated Carrying Estimated Carrying Estimated Fair Value Value Fair Value Value Fair Value Value Fair Value Hierarchy Cash and due from banks $ 149,524 $ 149,524 $ 166,237 $ 166,237 $ 190,387 $ 190,387 Level 1 Federal funds sold 5,720 5,720 3,110 3,110 8,760 8,760 Level 1 Interest-bearing deposits in banks 18,179 18,179 68,331 68,331 54,324 54,324 Level 1 Interest-bearing time deposits in banks 5,456 5,466 24,188 24,266 17,002 17,032 Level 2 Available-for-sale securities 2,729,113 2,729,113 2,173,828 2,173,828 2,415,856 2,415,856 Levels 1 and 2 Held-to-maturity securities 295 301 568 576 441 447 Level 2 Loans 2,928,769 2,935,344 2,750,752 2,764,118 2,901,167 2,906,399 Level 3 Accrued interest receivable 32,003 32,003 27,583 27,583 28,998 28,998 Level 2 Deposits with stated maturities 598,404 600,093 692,937 695,006 648,992 650,893 Level 2 Deposits with no stated maturities 4,129,015 4,129,015 3,625,521 3,625,521 4,101,263 4,101,263 Level 1 Short-term borrowings 621,155 621,155 434,583 434,583 367,110 367,110 Level 2 Accrued interest payable 242 242 291 291 237 237 Level 2

Basis of Presentation - Additio

Basis of Presentation - Additional Information (Detail)	Jun. 30, 2015LocationOfficeshares	Jun. 30, 2015shares	Jun. 30, 2015shares	Apr. 28, 2015shares	Dec. 31, 2014shares	Oct. 28, 2014shares	Jun. 30, 2014shares
Basis Of Presentation [Line Items]
Number of locations	62
Number of mortgage origination offices | Office	3
Common stock, shares authorized | shares	120,000,000	120,000,000	120,000,000	120,000,000	120,000,000		120,000,000
Stock repurchase program expiration date		Sep. 30, 2017
Minimum number of shares that company is required to repurchase | shares		0
Stock repurchased under authorization | shares			0
Subsidiary of Common Parent [Member]
Basis Of Presentation [Line Items]
Number of locations	8
Maximum [Member]
Basis Of Presentation [Line Items]
Stock repurchase program, number of shares authorized to be repurchased | shares						1,500,000
Abilene [Member]
Basis Of Presentation [Line Items]
Number of locations	11
Abilene [Member] | Subsidiary of Common Parent [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Cleburne [Member]
Basis Of Presentation [Line Items]
Number of locations	2
Stephenville [Member]
Basis Of Presentation [Line Items]
Number of locations	2
Stephenville [Member] | Subsidiary of Common Parent [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Granbury [Member]
Basis Of Presentation [Line Items]
Number of locations	2
San Angelo [Member]
Basis Of Presentation [Line Items]
Number of locations	3
San Angelo [Member] | Subsidiary of Common Parent [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Weatherford [Member]
Basis Of Presentation [Line Items]
Number of locations	3
Mineral Wells [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Hereford [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Sweetwater [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Sweetwater [Member] | Subsidiary of Common Parent [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Eastland [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Ranger [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Rising Star [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Cisco [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Southlake [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Number of mortgage origination offices | Office	1
Grapevine [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Aledo [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Willow Park [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Brock [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Alvarado [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Beaumont [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Beaumont [Member] | Subsidiary of Common Parent [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Burleson [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Keller [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Trophy Club [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Boyd [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Bridgeport [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Decatur [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Roby [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Trent [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Merkel [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Clyde [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Moran [Member]
Basis Of Presentation [Line Items]
Number of locations	1
New Waverly [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Albany [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Midlothian [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Glen Rose [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Odessa [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Odessa [Member] | Subsidiary of Common Parent [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Waxahachie [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Acton [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Fort Worth [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Fort Worth [Member] | Subsidiary of Common Parent [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Orange [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Newton [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Port Arthur [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Vidor [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Mauriceville [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Huntsville [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Lubbock [Member] | Subsidiary of Common Parent [Member]
Basis Of Presentation [Line Items]
Number of locations	1
Dallas [Member]
Basis Of Presentation [Line Items]
Number of mortgage origination offices | Office	1
Ft. Worth [Member]
Basis Of Presentation [Line Items]
Number of mortgage origination offices | Office	1

Stock Split - Additional Inform

Stock Split - Additional Information (Detail)	Apr. 22, 2014	Jun. 30, 2015
Text Block [Abstract]
Stock split conversion ratio		Two-for-one stock split
Percentage of stock dividend declared	100.00%
Dividend declared date		Apr. 22, 2014
Dividend record date		May 15, 2014
Dividend distribution date		Jun. 2, 2014

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Weighted average common shares outstanding, basic	64,148,356	64,045,282	64,135,731	64,027,776
Weighted average common shares outstanding, diluted	64,354,720	64,301,306	64,328,672	64,298,525

Interest-bearing Time Deposit29

Interest-bearing Time Deposits in Banks and Securities - Additional Information (Detail)	Jun. 30, 2015USD ($)Investment	Dec. 31, 2014USD ($)	Jun. 30, 2014USD ($)	Jun. 30, 2015USD ($)Investment	Jun. 30, 2014USD ($)	Jun. 30, 2015USD ($)Investment	Jun. 30, 2014USD ($)
Interest Bearing Time Deposits In Banks And Securities [Line Items]
INTEREST-BEARING TIME DEPOSITS IN BANKS	$ 5,456,000	$ 17,002,000	$ 24,188,000	$ 5,456,000	$ 24,188,000	$ 5,456,000	$ 24,188,000
Time deposits with balances greater than $250,000, FDIC insured limit	983,000	3,195,000	5,269,000	983,000	5,269,000	983,000	5,269,000
Held-to-maturity securities	$ 295,000	441,000	568,000	$ 295,000	568,000	$ 295,000	568,000
Number of investment positions | Investment	262			262		262
Securities pledged as collateral	$ 1,543,543,000			$ 1,543,543,000		$ 1,543,543,000
Sales of investment securities available-for-sale				6,631,000	541,000	7,760,000	1,445,000
Gross realized gains from security sales				243,000	0	248,000	1,000
Gross realized losses from security sales				$ 4,000	$ 1,000	$ 4,000	$ 6,000
Minimum [Member]
Interest Bearing Time Deposits In Banks And Securities [Line Items]
Interest-bearing time deposits, maturity period, years						1 year
Time deposits balances, FDIC insured limit	$ 250,000	$ 250,000	$ 250,000
Maximum [Member]
Interest Bearing Time Deposits In Banks And Securities [Line Items]
Interest-bearing time deposits, maturity period, years						4 years

Interest-bearing Time Deposit30

Interest-bearing Time Deposits in Banks and Securities - Summary of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, Amortized Cost Basis	$ 2,669,891	$ 2,338,683	$ 2,113,044
Securities available-for-sale, Gross Unrealized Holding Gains	68,137	81,202	70,219
Securities available-for-sale, Gross Unrealized Holding Losses	(8,915)	(4,029)	(9,435)
Securities available-for-sale, Estimated Fair Value	2,729,113	2,415,856	2,173,828
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, Amortized Cost Basis	10,864	518
Securities available-for-sale, Gross Unrealized Holding Gains	72	2
Securities available-for-sale, Estimated Fair Value	10,936	520
Obligations of U.S. Government Sponsored-Enterprises and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, Amortized Cost Basis	164,351	128,919	118,907
Securities available-for-sale, Gross Unrealized Holding Gains	985	864	1,210
Securities available-for-sale, Gross Unrealized Holding Losses		(28)
Securities available-for-sale, Estimated Fair Value	165,336	129,755	120,117
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, Amortized Cost Basis	1,340,163	1,107,795	1,027,503
Securities available-for-sale, Gross Unrealized Holding Gains	49,483	60,083	49,171
Securities available-for-sale, Gross Unrealized Holding Losses	(5,400)	(250)	(2,016)
Securities available-for-sale, Estimated Fair Value	1,384,246	1,167,628	1,074,658
Corporate Bonds and Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, Amortized Cost Basis	94,485	95,864	97,119
Securities available-for-sale, Gross Unrealized Holding Gains	2,623	2,894	3,621
Securities available-for-sale, Estimated Fair Value	97,108	98,758	100,740
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, Amortized Cost Basis	856,546	871,265	734,301
Securities available-for-sale, Gross Unrealized Holding Gains	14,383	16,804	16,183
Securities available-for-sale, Gross Unrealized Holding Losses	(2,838)	(2,858)	(5,011)
Securities available-for-sale, Estimated Fair Value	868,091	885,211	745,473
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities available-for-sale, Amortized Cost Basis	203,482	134,322	135,214
Securities available-for-sale, Gross Unrealized Holding Gains	591	555	34
Securities available-for-sale, Gross Unrealized Holding Losses	(677)	(893)	(2,408)
Securities available-for-sale, Estimated Fair Value	$ 203,396	$ 133,984	$ 132,840

Interest-bearing Time Deposit31

Interest-bearing Time Deposits in Banks and Securities - Amortized Cost and Estimated Fair Value of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale, Amortized Cost Basis, Due within one year	$ 133,995
Available-for-Sale, Amortized Cost Basis, Due after one year through five years	707,981
Available-for-Sale, Amortized Cost Basis, Due after five years through ten years	750,600
Available-for-Sale, Amortized Cost Basis, Due after ten years	17,287
Available-for-Sale, Amortized Cost Basis, Mortgage-backed securities	1,060,028
Available-for-Sale, Amortized Cost Basis, Total	2,669,891
Available-for-Sale, Estimated Fair Value, Due within one year	135,181
Available-for-Sale, Estimated Fair Value, Due after one year through five years	737,467
Available-for-Sale, Estimated Fair Value, Due after five years through ten years	767,300
Available-for-Sale, Estimated Fair Value, Due after ten years	17,678
Available-for-Sale, Estimated Fair Value, Mortgage-backed securities	1,071,487
Securities available-for-sale, Estimated Fair Value	$ 2,729,113	$ 2,415,856	$ 2,173,828

Interest-bearing Time Deposit32

Interest-bearing Time Deposits in Banks and Securities - Continuous Unrealized-Loss Position of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Fair Value	$ 615,230	$ 272,171	$ 165,357
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	6,807	6,652	509
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value	77,597	135,369	204,682
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss	2,108	2,783	3,520
Available-for-sale securities, continuous unrealized loss position, Fair Value	692,827	407,540	370,039
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss	8,915	9,435	4,029
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Fair Value	304,510	41,095	15,128
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	5,335	160	60
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value	2,531	101,800	21,249
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss	65	1,856	190
Available-for-sale securities, continuous unrealized loss position, Fair Value	307,041	142,895	36,377
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss	5,400	2,016	250
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Fair Value	176,569	133,104	76,350
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	844	4,417	148
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value	65,562	23,427	128,368
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss	1,994	594	2,710
Available-for-sale securities, continuous unrealized loss position, Fair Value	242,131	156,531	204,718
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss	2,838	5,011	2,858
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Fair Value	134,151	97,972	48,399
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	628	2,075	273
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value	9,504	10,142	55,065
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss	49	333	620
Available-for-sale securities, continuous unrealized loss position, Fair Value	143,655	108,114	103,464
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss	$ 677	$ 2,408	893
Obligations of U.S. Government Sponsored-Enterprises and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Fair Value			25,480
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss			28
Available-for-sale securities, continuous unrealized loss position, Fair Value			25,480
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss			$ 28

Loans and Allowance for Loan 33

Loans and Allowance for Loan Losses - Additional Information (Detail)	Jun. 30, 2015USD ($)	Dec. 31, 2014USD ($)	Jun. 30, 2014USD ($)	Jun. 30, 2015USD ($)Security_Loan	Jun. 30, 2014USD ($)Security_Loan	Jun. 30, 2015USD ($)Security_Loan	Jun. 30, 2014USD ($)Security_Loan	Dec. 31, 2014USD ($)
Receivables [Abstract]
Minimum number of days to consider the loans as non-accrual
Carrying amount of purchased credit impaired loans	$ 1,123,000	$ 2,151,000	$ 2,519,000			$ 1,123,000	$ 2,519,000	$ 2,151,000
Contractual balance	1,648,000	3,275,000	3,754,000	$ 1,648,000	$ 3,754,000	1,648,000	3,754,000	3,275,000
Loans held for sale	25,544,000	8,803,000	13,570,000	25,544,000	13,570,000	25,544,000	13,570,000	8,803,000
Average recorded investment in impaired loans				16,877,000		18,387,000	26,522,000	24,497,000
Nonaccrual, past due 90 days or more and still accruing, restructured loans and foreclosed assets	18,135,000	21,716,000	26,030,000	18,135,000	26,030,000	18,135,000	26,030,000	21,716,000
Additional funds advanced in connection with impaired loans	0			0		0
Interest income recognized on impaired loans	0	0	0
Interest income recognized on impaired loans								162,000
Allowance for purchased credit impaired loans	0	0	0	$ 0	$ 0	$ 0	$ 0	0
Default for purposes of this disclosure is a troubled debt restructured loan						90 days
Number of loans modified | Security_Loan				0	1	1	1
Commitments to lend additional funds to borrowers with loan that have been modified as TDRs	0			$ 0		$ 0
Loans held by subsidiaries subject to blanket liens	1,720,486,000			1,720,486,000		1,720,486,000
Letters of credit outstanding, amount	5,000,000			5,000,000		5,000,000
Advances from Federal Home Loan Bank of Dallas	$ 265,036,000	$ 1,010,000	$ 111,065,000	$ 265,036,000	$ 111,065,000	$ 265,036,000	$ 111,065,000	$ 1,010,000

Loans and Allowance for Loan 34

Loans and Allowance for Loan Losses - Loans Held-for-Investment by Class of Financing Receivables (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Receivables [Abstract]
Commercial	$ 649,909	$ 639,954	$ 617,925
Agricultural	92,317	105,694	75,133
Real estate	1,838,488	1,822,854	1,733,604
Consumer	361,510	360,686	346,412
Total	$ 2,942,224	$ 2,929,188	$ 2,773,074

Loans and Allowance for Loan 35

Loans and Allowance for Loan Losses - Non-Accrual Loans, Loans Still Accruing and Past Due 90 Days or More and Restructured Loans (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Receivables [Abstract]
Non-accrual loans	$ 16,854	$ 20,194	$ 23,565
Loans still accruing and past due 90 days or more	64	261	123
Troubled debt restructured loans	172	226
Total	$ 17,090	$ 20,681	$ 23,688

Loans and Allowance for Loan 36

Loans and Allowance for Loan Losses - Non-Accrual Loans, Loans Still Accruing and Past Due 90 Days or More and Restructured Loans (Parenthetical) (Detail) - USD ($)	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Receivables [Abstract]
Carrying amount of purchased credit impaired loans	$ 1,123,000	$ 2,151,000	$ 2,519,000	$ 1,123,000	$ 2,519,000	$ 2,151,000
Troubled debt restructured loans	$ 6,936,000	$ 9,073,000	$ 10,810,000

Loans and Allowance for Loan 37

Loans and Allowance for Loan Losses - Recorded Investment in Impaired Loans and Related Valuation Allowance (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Receivables [Abstract]
Recorded Investment	$ 16,854	$ 20,194	$ 23,565
Valuation Allowance	$ 3,866	$ 4,213	$ 4,883

Loans and Allowance for Loan 38

Loans and Allowance for Loan Losses - Schedule of Non-Accrual Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	$ 16,854	$ 20,194	$ 23,565
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	3,606	3,193	3,640
Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	118	165	109
Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	12,570	16,218	19,027
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	$ 560	$ 618	$ 789

Loans and Allowance for Loan 39

Loans and Allowance for Loan Losses - Schedule of Impaired Loans and Related Allowance (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Unpaid Contractual Principal Balance	$ 23,826	$ 23,826	$ 29,795	$ 26,941
Recorded Investment With No Allowance	3,551	3,551	6,339	5,566
Recorded Investment With Allowance	13,303	13,303	17,226	14,628
Total Recorded Investment	16,854	16,854	23,565	20,194
Related Allowance	3,866	3,866	4,883	4,213
Year-to-Date Average Recorded Investment	16,877	18,387	26,522	24,497
Three-month Average Recorded Investment		16,877	25,004
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Unpaid Contractual Principal Balance	4,168	4,168	4,095	3,749
Recorded Investment With No Allowance	263	263	271	287
Recorded Investment With Allowance	3,343	3,343	3,369	2,906
Total Recorded Investment	3,606	3,606	3,640	3,193
Related Allowance	1,168	1,168	1,161	1,171
Year-to-Date Average Recorded Investment		3,717	4,083	3,698
Three-month Average Recorded Investment		3,298	3,224
Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Unpaid Contractual Principal Balance	163	163	121	177
Recorded Investment With Allowance	118	118	109	165
Total Recorded Investment	118	118	109	165
Related Allowance	87	87	41	57
Year-to-Date Average Recorded Investment		148	118	179
Three-month Average Recorded Investment		136	101
Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Unpaid Contractual Principal Balance	18,711	18,711	24,619	22,177
Recorded Investment With No Allowance	2,921	2,921	5,626	4,859
Recorded Investment With Allowance	9,649	9,649	13,401	11,359
Total Recorded Investment	12,570	12,570	19,027	16,218
Related Allowance	2,506	2,506	3,497	2,867
Year-to-Date Average Recorded Investment		13,817	21,442	19,837
Three-month Average Recorded Investment		12,876	20,920
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Unpaid Contractual Principal Balance	784	784	960	838
Recorded Investment With No Allowance	367	367	442	420
Recorded Investment With Allowance	193	193	347	198
Total Recorded Investment	560	560	789	618
Related Allowance	$ 105	105	184	118
Year-to-Date Average Recorded Investment		705	879	$ 783
Three-month Average Recorded Investment		$ 567	$ 759

Loans and Allowance for Loan 40

Loans and Allowance for Loan Losses - Schedule of Impaired Loans and Related Allowance (Parenthetical) (Detail) - USD ($)	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Receivables [Abstract]
Carrying amount of purchased credit impaired loans	$ 1,123,000	$ 2,151,000	$ 2,519,000	$ 1,123,000	$ 2,519,000	$ 2,151,000

Loans and Allowance for Loan 41

Loans and Allowance for Loan Losses - Schedule of Internal Ratings of Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	$ 2,942,224	$ 2,929,188	$ 2,773,074
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	649,909	639,954	617,925
Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	92,317	105,694	75,133
Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	1,838,488	1,822,854	1,733,604
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	361,510	360,686	346,412
Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	2,846,455	2,856,206	2,693,144
Pass [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	611,071	626,266	605,163
Pass [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	91,657	105,101	74,734
Pass [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	1,783,633	1,765,886	1,668,844
Pass [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	360,094	358,953	344,403
Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	47,409	19,453	20,930
Special Mention [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	25,438	3,853	3,678
Special Mention [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	159	91	102
Special Mention [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	21,504	15,106	16,628
Special Mention [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	308	403	522
Substandard [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	48,317	53,388	58,864
Substandard [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	13,400	9,835	9,084
Substandard [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	501	502	296
Substandard [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	33,308	41,722	48,001
Substandard [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	1,108	1,329	1,483
Doubtful [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	43	141	136
Doubtful [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan			1
Doubtful [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan	$ 43	140	131
Doubtful [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Internal ratings of loan		$ 1	$ 4

Loans and Allowance for Loan 42

Loans and Allowance for Loan Losses - Schedule of Past Due Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 26,767	$ 22,888	$ 29,380
Total Current	2,915,457	2,906,300	2,743,694
Total	2,942,224	2,929,188	2,773,074
Total 90 Days Past Due Still Accruing	64	261	123
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	7,904	4,880	7,589
Total Current	642,005	635,074	610,336
Total	649,909	639,954	617,925
Total 90 Days Past Due Still Accruing		24	23
Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	270	479	148
Total Current	92,047	105,215	74,985
Total	92,317	105,694	75,133
Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	16,646	14,577	19,577
Total Current	1,821,842	1,808,277	1,714,027
Total	1,838,488	1,822,854	1,733,604
Total 90 Days Past Due Still Accruing	47	207	83
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,947	2,952	2,066
Total Current	359,563	357,734	344,346
Total	361,510	360,686	346,412
Total 90 Days Past Due Still Accruing	17	30	17
15-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	23,089	19,372	25,675
15-59 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	7,854	4,611	7,290
15-59 Days Past Due [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	270	437	134
15-59 Days Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	13,458	12,002	16,781
15-59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,507	2,322	1,470
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,635	1,339	1,331
60-89 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	38	94	51
60-89 Days Past Due [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		42	14
60-89 Days Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,255	707	823
60-89 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	342	496	443
Greater than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,043	2,177	2,374
Greater than 90 Days [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	12	175	248
Greater than 90 Days [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,933	1,868	1,973
Greater than 90 Days [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 98	$ 134	$ 153

Loans and Allowance for Loan 43

Loans and Allowance for Loan Losses - Schedule of Allowance for Loan Losses by Portfolio Segment (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Apr. 01, 2015	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	$ 3,866		$ 4,213	$ 4,883
Loans collectively evaluated for impairment	35,133		32,611	31,009
Total allowance for loan losses	38,999	$ 37,828	36,824	35,892	$ 34,693	$ 33,900
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	1,168		1,171	1,161
Loans collectively evaluated for impairment	10,288		6,819	5,700
Total allowance for loan losses	11,456	10,375	7,990	6,861	6,645	6,440
Agriculture [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	87		57	41
Loans collectively evaluated for impairment	305		470	323
Total allowance for loan losses	392	473	527	364	285	383
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	2,506		2,867	3,497
Loans collectively evaluated for impairment	21,836		23,790	23,064
Total allowance for loan losses	24,342	25,239	26,657	26,561	25,629	24,940
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	105		118	184
Loans collectively evaluated for impairment	2,704		1,532	1,922
Total allowance for loan losses	$ 2,809	$ 1,741	$ 1,650	$ 2,106	$ 2,134	$ 2,137

Loans and Allowance for Loan 44

Loans and Allowance for Loan Losses - Changes in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 37,828	$ 34,693	$ 36,824	$ 33,900
PROVISION FOR LOAN LOSSES	1,554	1,124	2,844	2,814
Recoveries	560	376	784	776
Charge-offs	(943)	(301)	(1,453)	(1,598)
Ending balance	38,999	35,892	38,999	35,892
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	10,375	6,645	7,990	6,440
PROVISION FOR LOAN LOSSES	1,324	219	3,789	554
Recoveries	117	65	197	154
Charge-offs	(360)	(68)	(520)	(287)
Ending balance	11,456	6,861	11,456	6,861
Agriculture [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	473	285	527	383
PROVISION FOR LOAN LOSSES	(27)	78	(59)	(21)
Recoveries		1	2	3
Charge-offs	(54)		(78)	(1)
Ending balance	392	364	392	364
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	25,239	25,629	26,657	24,940
PROVISION FOR LOAN LOSSES	(1,048)	835	(2,515)	2,068
Recoveries	302	132	373	319
Charge-offs	(151)	(35)	(173)	(766)
Ending balance	24,342	26,561	24,342	26,561
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,741	2,134	1,650	2,137
PROVISION FOR LOAN LOSSES	1,305	(8)	1,629	213
Recoveries	141	178	212	300
Charge-offs	(378)	(198)	(682)	(544)
Ending balance	$ 2,809	$ 2,106	$ 2,809	$ 2,106

Loans and Allowance for Loan 45

Loans and Allowance for Loan Losses - Schedule of Investment in Loans Related to Balance in Allowance for Loan Losses on Basis of Company's Impairment Methodology (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Financing Receivable, Impaired [Line Items]
Loans individually evaluated for impairment	$ 16,854	$ 20,194	$ 23,565
Loans collectively evaluated for impairment	2,925,370	2,908,994	2,749,509
Total	2,942,224	2,929,188	2,773,074
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Loans individually evaluated for impairment	3,606	3,193	3,640
Loans collectively evaluated for impairment	646,303	636,761	614,285
Total	649,909	639,954	617,925
Agriculture [Member]
Financing Receivable, Impaired [Line Items]
Loans individually evaluated for impairment	118	165	109
Loans collectively evaluated for impairment	92,199	105,529	75,024
Total	92,317	105,694	75,133
Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Loans individually evaluated for impairment	12,570	16,218	19,027
Loans collectively evaluated for impairment	1,825,918	1,806,636	1,714,577
Total	1,838,488	1,822,854	1,733,604
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Loans individually evaluated for impairment	560	618	789
Loans collectively evaluated for impairment	360,950	360,068	345,623
Total	$ 361,510	$ 360,686	$ 346,412

Loans and Allowance for Loan 46

Loans and Allowance for Loan Losses - Schedule of Loans Modified and Considered Troubled Debt Restructuring (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015USD ($)SecurityLoan	Jun. 30, 2014USD ($)SecurityLoan	Jun. 30, 2015USD ($)SecurityLoan	Jun. 30, 2014USD ($)SecurityLoan
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan	6	5	10	13
Pre-Modification Recorded Investment	$ 414	$ 855	$ 566	$ 1,039
Post-Modification Recorded Investment	$ 414	$ 855	$ 566	$ 1,039
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan	2	1	2	5
Pre-Modification Recorded Investment	$ 74	$ 302	$ 74	$ 399
Post-Modification Recorded Investment	$ 74	$ 302	$ 74	$ 399
Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan		1	3	1
Pre-Modification Recorded Investment		$ 39	$ 128	$ 39
Post-Modification Recorded Investment		$ 39	$ 128	$ 39
Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan	2	3	2	4
Pre-Modification Recorded Investment	$ 336	$ 514	$ 336	$ 590
Post-Modification Recorded Investment	$ 336	$ 514	$ 336	$ 590
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan	2		3	3
Pre-Modification Recorded Investment	$ 4		$ 28	$ 11
Post-Modification Recorded Investment	$ 4		$ 28	$ 11

Loans and Allowance for Loan 47

Loans and Allowance for Loan Losses - Schedule of How Loans Were Modified as Troubled Debt Restructured Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Financing Receivable, Modifications [Line Items]
Adjusted Interest Rate	$ 257		$ 257
Extended Maturity	78	$ 42	206	$ 223
Combined Rate and Maturity	79	813	103	816
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Extended Maturity	74		74	97
Combined Rate and Maturity		302		302
Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Extended Maturity			128
Combined Rate and Maturity		39		39
Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Adjusted Interest Rate	257		257
Extended Maturity		42		118
Combined Rate and Maturity	79	$ 472	79	472
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Extended Maturity	$ 4		4	8
Combined Rate and Maturity			$ 24	$ 3

Loans and Allowance for Loan 48

Loans and Allowance for Loan Losses - Schedule of Troubled Debt Restructurings (Detail) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2014USD ($)Contract	Jun. 30, 2015USD ($)Contract	Jun. 30, 2014USD ($)Contract
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	1	1	1
Balance | $	$ 32	$ 111	$ 32
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number		1
Balance | $		$ 111
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number	1		1
Balance | $	$ 32		$ 32

Short-Term Borrowings - Schedul

Short-Term Borrowings - Schedule of Short-Term Borrowings (Detail) - USD ($)	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Debt Disclosure [Abstract]
Securities sold under agreements with customers to repurchase	$ 346,369,000	$ 357,400,000	$ 312,893,000
Federal funds purchased	9,750,000	8,700,000	10,625,000
Advances from Federal Home Loan Bank of Dallas	265,036,000	1,010,000	111,065,000
Total	$ 621,155,000	$ 367,110,000	$ 434,583,000

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Tax Disclosure [Abstract]
Income tax expense	$ 8,080	$ 6,758	$ 15,845	$ 13,863
Effective tax rates on pre-tax income	24.20%	24.17%	24.32%	24.15%
Statutory federal tax rate			35.00%

Stock Based Compensation - Addi

Stock Based Compensation - Additional Information (Detail)	Jul. 21, 2015USD ($)Non_Employee_Directorsshares	Jun. 30, 2015USD ($)	Jun. 30, 2014USD ($)	Jun. 30, 2015USD ($)shares	Jun. 30, 2014USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option expense | $		$ 182,000	$ 212,000	$ 360,000	$ 357,000
Stock options granted				0	0
Subsequent Event [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of non employee directors | Non_Employee_Directors	10
Subsequent Event [Member] | Restricted Stock [Member] | Non Employee Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted	7,070
Restricted shares value | $	$ 250,000

Pension Plan - Additional Infor

Pension Plan - Additional Information (Detail)	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2015USD ($)	Dec. 31, 2014USD ($)Participants	Jun. 30, 2014USD ($)	Jun. 30, 2015USD ($)	Jun. 30, 2014USD ($)	Dec. 31, 2014USD ($)
Compensation and Retirement Disclosure [Abstract]
Contribution towards pension plan				$ 0		$ 250,000
Recognized pension expense, before income tax		$ 2,909,000
Benefits paid out of pension plan assets to plan participants		$ 10,626,000
Percentage of benefits paid of total outstanding obligation balance to plan participants		43.00%				43.00%
Number of participants reduced | Participants		335
Number of participants reduced percentage		44.00%				44.00%
Net periodic benefit costs, total	$ 74,000		$ 84,000	$ 149,000	$ 214,000

Fair Value Disclosures - Additi

Fair Value Disclosures - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Assets transfer between Level 2 and Level 3	$ 0	$ 0	$ 0	$ 0
Impaired loans carrying value	16,854,000	23,565,000	16,854,000	23,565,000	$ 20,194,000
Impaired loans valuation reserves	3,866,000		3,866,000
Impaired loans net fair value	12,988,000		12,988,000
Other real estate owned, total	$ 635,000	$ 2,208,000	$ 635,000	$ 2,208,000	$ 943,000
Minimum [Member]
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Debt discounts, percentage			5.00%
Maximum [Member]
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Debt discounts, percentage			25.00%

Fair Value Disclosures - Financ

Fair Value Disclosures - Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	$ 2,729,113	$ 2,415,856	$ 2,173,828
U.S. Treasury Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	10,936	520
Obligations of U.S. Government Sponsored-Enterprises and Agencies [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	165,336	129,755	120,117
Obligations of States and Political Subdivisions [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	1,384,246	1,167,628	1,074,658
Residential Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	868,091	885,211	745,473
Commercial Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	203,396	133,984	132,840
Fair Value, Measurements, Recurring [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	2,729,113	2,415,856	2,173,828
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	92,188	94,065	95,940
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	10,936	520
Fair Value, Measurements, Recurring [Member] | Obligations of U.S. Government Sponsored-Enterprises and Agencies [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	165,336	129,755	120,117
Fair Value, Measurements, Recurring [Member] | Obligations of States and Political Subdivisions [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	1,384,246	1,167,628	1,074,658
Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	868,091	885,211	745,473
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	203,396	133,984	132,840
Fair Value, Measurements, Recurring [Member] | Other Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	4,920	4,693	4,800
Fair Value, Measurements, Recurring [Member] | Level 1 Inputs [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	15,856	5,213	4,800
Fair Value, Measurements, Recurring [Member] | Level 1 Inputs [Member] | U.S. Treasury Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	10,936	520
Fair Value, Measurements, Recurring [Member] | Level 1 Inputs [Member] | Other Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	4,920	4,693	4,800
Fair Value, Measurements, Recurring [Member] | Level 2 Inputs [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	2,713,257	2,410,643	2,169,028
Fair Value, Measurements, Recurring [Member] | Level 2 Inputs [Member] | Corporate Bonds [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	92,188	94,065	95,940
Fair Value, Measurements, Recurring [Member] | Level 2 Inputs [Member] | Obligations of U.S. Government Sponsored-Enterprises and Agencies [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	165,336	129,755	120,117
Fair Value, Measurements, Recurring [Member] | Level 2 Inputs [Member] | Obligations of States and Political Subdivisions [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	1,384,246	1,167,628	1,074,658
Fair Value, Measurements, Recurring [Member] | Level 2 Inputs [Member] | Residential Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	868,091	885,211	745,473
Fair Value, Measurements, Recurring [Member] | Level 2 Inputs [Member] | Commercial Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	$ 203,396	$ 133,984	$ 132,840

Fair Value Disclosures - Other

Fair Value Disclosures - Other Real Estate Owned (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Fair Value Disclosures [Abstract]
Carrying value of other real estate owned prior to re-measurement	$ 341	$ 708	$ 351	$ 708
Write-downs included in gain (loss) on sale of other real estate owned	(85)	(89)	(95)	(89)
Fair value	$ 256	$ 619	$ 256	$ 619

Fair Value Disclosures - Schedu

Fair Value Disclosures - Schedule of Estimated Fair Values and Carrying Values of All Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
CASH AND DUE FROM BANKS	$ 149,524	$ 190,387	$ 166,237
FEDERAL FUNDS SOLD	5,720	8,760	3,110
INTEREST-BEARING DEPOSITS IN BANKS	18,179	54,324	68,331
INTEREST-BEARING TIME DEPOSITS IN BANKS	5,456	17,002	24,188
Available-for-sale securities	2,729,113	2,415,856	2,173,828
Held-to-maturity securities	295	441	568
Loans	2,928,769	2,901,167	2,750,752
SHORT-TERM BORROWINGS	621,155	367,110	434,583
Carrying Value [Member] | Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
CASH AND DUE FROM BANKS	149,524	190,387	166,237
FEDERAL FUNDS SOLD	5,720	8,760	3,110
INTEREST-BEARING DEPOSITS IN BANKS	18,179	54,324	68,331
Deposits with no stated maturities	4,129,015	4,101,263	3,625,521
Carrying Value [Member] | Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
INTEREST-BEARING TIME DEPOSITS IN BANKS	5,456	17,002	24,188
Held-to-maturity securities	295	441	568
Accrued interest receivable	32,003	28,998	27,583
Deposits with stated maturities	598,404	648,992	692,937
SHORT-TERM BORROWINGS	621,155	367,110	434,583
Accrued interest payable	242	237	291
Carrying Value [Member] | Levels 1 and 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	2,729,113	2,415,856	2,173,828
Carrying Value [Member] | Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	2,928,769	2,901,167	2,750,752
Estimated Fair Value [Member] | Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
CASH AND DUE FROM BANKS	149,524	190,387	166,237
FEDERAL FUNDS SOLD	5,720	8,760	3,110
INTEREST-BEARING DEPOSITS IN BANKS	18,179	54,324	68,331
Deposits with no stated maturities	4,129,015	4,101,263	3,625,521
Estimated Fair Value [Member] | Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
INTEREST-BEARING TIME DEPOSITS IN BANKS	5,466	17,032	24,266
Held-to-maturity securities	301	447	576
Accrued interest receivable	32,003	28,998	27,583
Deposits with stated maturities	600,093	650,893	695,006
SHORT-TERM BORROWINGS	621,155	367,110	434,583
Accrued interest payable	242	237	291
Estimated Fair Value [Member] | Levels 1 and 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	2,729,113	2,415,856	2,173,828
Estimated Fair Value [Member] | Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	$ 2,935,344	$ 2,906,399	$ 2,764,118

Acquisition and Asset Purchase

Acquisition and Asset Purchase - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2015	Apr. 08, 2015	Apr. 01, 2015	Dec. 31, 2014	Jun. 30, 2014
Business Acquisition [Line Items]
Gross loans	$ 2,942,224,000			$ 2,929,188,000	$ 2,773,074,000
Total deposits	4,727,419,000			4,750,255,000	4,318,458,000
Total assets	$ 6,115,236,000			$ 5,848,202,000	$ 5,446,356,000
FBC Bancshares, Inc. and First Bank, N.A. [Member]
Business Acquisition [Line Items]
Business acquisition, definitive agreement date	Apr. 1, 2015
Business acquisition, expected stock purchase price			$ 61,000,000
First Bank, N.A. [Member]
Business Acquisition [Line Items]
Gross loans	$ 257,046,000
Total deposits	339,423,000
Total assets	$ 372,188,000
4Trust Mortgage, Inc. [Member]
Business Acquisition [Line Items]
Business acquisition, asset purchase agreement date	Apr. 8, 2015
Business acquisition, cash purchase price		$ 1,900,000