First Financial Bankshares (FFIN) 10-Q 30 Jul 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Jul. 30, 2019
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Document Period End Date	Jun. 30, 2019
Entity Registrant Name	FIRST FINANCIAL BANKSHARES INC
Entity Central Index Key	0000036029
Entity Filer Category	Large Accelerated Filer
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity File Number	0-7674
Entity Incorporation, State or Country Code	TX
Entity Tax Identification Number	75-0944023
Entity Address, Address Line One	400 Pine Street
Entity Address, City or Town	Abilene
Entity Address, State or Province	TX
City Area Code	325
Local Phone Number	627-7155
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Title of 12(b) Security	Class A Common Stock
Trading Symbol	FFIN
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Document Transition Report	false
Entity Address, Postal Zip Code	79601
Entity Common Stock, Shares Outstanding		135,809,224

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
ASSETS
CASH AND DUE FROM BANKS	$ 178,345	$ 207,835	$ 178,217
FEDERAL FUNDS SOLD	700		8,450
INTEREST-BEARING DEPOSITS IN BANKS	128,652	40,812	99,499
Total cash and cash equivalents	307,697	248,647	286,166
INTEREST-BEARING TIME DEPOSITS IN BANKS	960	1,458	1,458
SECURITIES AVAILABLE-FOR-SALE, at fair value	3,259,492	3,158,777	3,197,567
LOANS:
Held for investment	4,040,952	3,953,636	3,831,480
Less – allowance for loan losses	(51,820)	(51,202)	(49,951)
Net loans held for investment	3,989,132	3,902,434	3,781,529
Held-for-sale ($18,981, $5,061 and $19,185 at fair value at June 30, 2019 and 2018 and December 31, 2018, respectively)	22,305	21,672	24,289
Net loans	4,011,437	3,924,106	3,805,818
BANK PREMISES AND EQUIPMENT, net	134,322	133,421	130,366
INTANGIBLE ASSETS	174,151	174,683	175,185
OTHER ASSETS	91,234	90,762	88,910
Total assets	7,979,293	7,731,854	7,685,470
LIABILITIES AND SHAREHOLDERS' EQUITY
NONINTEREST-BEARING DEPOSITS	2,167,552	2,116,107	2,105,953
INTEREST-BEARING DEPOSITS	4,202,214	4,064,282	4,104,654
Total deposits	6,369,766	6,180,389	6,210,607
DIVIDENDS PAYABLE	16,294	14,227	14,211
BORROWINGS	362,005	468,706	456,935
OTHER LIABILITIES	66,480	15,237	18,089
Total liabilities	6,814,545	6,678,559	6,699,842
SHAREHOLDERS' EQUITY:
Common stock – ($0.01 par value, authorized 200,000,000 shares; 135,809,224, 67,669,658 and 67,753,133 shares issued at June 30, 2019 and 2018 and December 31, 2018, respectively)	1,358	678	677
Capital surplus	448,349	443,114	439,731
Retained earnings	655,794	606,658	556,615
Treasury stock (shares at cost: 929,441, 491,170 and 467,811 at June 30, 2019 and 2018 and December 31, 2018, respectively)	(7,823)	(7,507)	(7,419)
Deferred compensation	7,823	7,507	7,419
Accumulated other comprehensive earnings (loss)	59,247	2,845	(11,395)
Total shareholders' equity	1,164,748	1,053,295	985,628
Total liabilities and shareholders' equity	$ 7,979,293	$ 7,731,854	$ 7,685,470

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Statement of Financial Position [Abstract]
Loans held-for-sale, fair value	$ 18,981	$ 19,185	$ 5,061
Common stock, par value	$ 0.01	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000	200,000,000
Common stock, shares issued	135,809,224	67,753,133	67,669,658
Treasury stock, shares	929,441	467,811	491,170

Consolidated Statements of Earn

Consolidated Statements of Earnings - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
INTEREST INCOME:
Interest and fees on loans	$ 55,740	$ 49,105	$ 108,971	$ 95,851
Interest on investment securities:
Taxable	13,925	12,719	27,213	24,073
Exempt from federal income tax	9,244	9,983	19,007	20,324
Interest on federal funds sold and interest-bearing deposits in banks	667	271	1,286	912
Total interest income	79,576	72,078	156,477	141,160
INTEREST EXPENSE:
Interest on deposits	7,286	4,005	13,947	7,524
Other	675	462	1,401	576
Total interest expense	7,961	4,467	15,348	8,100
Net interest income	71,615	67,611	141,129	133,060
PROVISION FOR LOAN LOSSES	600	1,105	1,565	2,415
Net interest income after provision for loan losses	71,015	66,506	139,564	130,645
NONINTEREST INCOME:
Trust Fees	7,027	7,070	14,006	13,975
Service Charges on Deposit Accounts	5,374	5,375	10,550	10,259
ATM, interchange and credit card fees	7,352	7,041	14,192	14,037
Real estate mortgage operations	4,721	3,951	8,195	6,884
Net gain on sale of available-for-sale securities (includes $676 and $67 for the three months ended June 30, 2019 and 2018, respectively, and $676 and $1,288 for the six months ended June 30, 2019 and 2018, respectively, related to accumulated other comprehensive earnings reclassifications)	676	67	676	1,288
Net gain (loss) on sale of foreclosed assets	53	19	122	118
Net gain (loss) on sale of assets	6		6	(91)
Interest on loan recoveries	903	289	1,241	408
Other	1,864	1,676	3,425	3,034
Total noninterest income	27,976	25,488	52,413	49,912
NONINTEREST EXPENSE:
Salaries and employee benefits	27,394	26,862	53,918	53,065
Loss from partial settlement of pension plan			900
Net occupancy expense	2,779	2,806	5,542	5,689
Equipment expense	2,827	3,440	5,954	6,957
FDIC insurance premiums	538	632	1,076	1,199
ATM, interchange and credit card expenses	2,427	2,205	4,810	4,348
Professional and service fees	1,987	2,026	3,820	4,439
Printing, stationery and supplies	502	612	868	1,098
Operational and other losses	480	305	746	871
Software amortization and expense	1,287	479	2,210	1,003
Amortization of intangible assets	264	384	532	771
Other	7,819	7,393	15,297	15,503
Total noninterest expense	48,304	47,144	95,673	94,943
EARNINGS BEFORE INCOME TAXES	50,687	44,850	96,304	85,614
INCOME TAX EXPENSE (includes $142 and $14 for the three months ended June 30, 2019 and 2018, respectively, and $142 and $270 for the six months ended June 30, 2019 and 2018, respectively, related to income tax expense from reclassification items)	8,594	7,217	15,959	13,462
NET EARNINGS	$ 42,093	$ 37,633	$ 80,345	$ 72,152
EARNINGS PER SHARE, BASIC	$ 0.31	$ 0.28	$ 0.59	$ 0.53
EARNINGS PER SHARE, ASSUMING DILUTION	0.31	0.28	0.59	0.53
DIVIDENDS PER SHARE	$ 0.12	$ 0.11	$ 0.23	$ 0.20

Consolidated Statements of Ea_2

Consolidated Statements of Earnings (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Reclassifications adjustment for realized gains on investment securities included in net earnings (loss), before income tax	$ 676	$ 67	$ 676	$ 1,288
Income tax expense from reclassification items	$ 142	$ 14	$ 142	$ 270

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Earnings - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
NET EARNINGS	$ 42,093	$ 37,633	$ 80,345	$ 72,152
OTHER ITEMS OF COMPREHENSIVE EARNINGS (LOSS):
Change in unrealized gain on investment securities available-for-sale, before income taxes	37,057	(11,600)	72,071	(54,306)
Reclassification adjustment for realized gains on investment securities included in net earnings, before income tax	(676)	(67)	(676)	(1,288)
Total other items of comprehensive earnings	36,381	(11,667)	71,395	(55,594)
Income tax benefit (expense) related to other items of comprehensive earnings	(7,640)	2,450	(14,993)	11,675
Reclassification of certain income tax effects related to the change in the U.S. statutory federal income tax rate under the Tax Cuts and Jobs Act to retained earnings.				5,759
COMPREHENSIVE EARNINGS	$ 70,834	$ 28,416	$ 136,747	$ 33,992

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 (Losses) [Member]
Beginning Balance at Dec. 31, 2017	$ 922,768	$ 663	$ 378,062	$ 517,257	$ (7,148)	$ 7,148	$ 26,786
Beginning Balance, Shares at Dec. 31, 2017		66,260,444			(495,964)
Net earnings (unaudited)	72,152			72,152
Stock option exercises (unaudited)	2,319	$ 1	2,318
Stock option exercises, Shares		109,133
Restricted stock grant (unaudited)	523		523
Restricted stock grant (unaudited), Shares		10,710
Cash dividends declared	(27,056)			(27,056)
Stock issued in acquisition of Commercial Bancshares, Inc.	58,087	$ 13	58,074
Stock issued in acquisition of Commercial Bancshares, Inc, Shares		1,289,371
Change in unrealized gain in investment securities available-for-sale, net of related income taxes (unaudited)	(43,919)						(43,919)
Shares purchased (redeemed) in connection with directors' deferred compensation plan, net (unaudited)					$ (271)	271
Shares purchased (redeemed) in connection with directors' deferred compensation plan, net, Shares					4,794
Stock option expense (unaudited)	754		754
Reclassification of certain income tax effects related to the change in the U.S. statutory federal income tax rate under the Tax Cuts and Jobs Act to retained earnings				(5,759)			5,759
Reclassification of unrealized gain in equity securities at December 31, 2017 from accumulated other comprehensive earnings to retained earnings (unaudited)				21			(21)
Ending Balance at Jun. 30, 2018	$ 985,628	$ 677	439,731	556,615	$ (7,419)	7,419	(11,395)
Ending Balance, Shares at Jun. 30, 2018		67,669,658
Treasury Stock, Ending Balance, Shares at Jun. 30, 2018	(491,170)				(491,170)
Beginning Balance at Mar. 31, 2018	$ 969,814	$ 676	437,868	533,427	$ (7,291)	7,291	(2,157)
Beginning Balance, Shares at Mar. 31, 2018		67,612,760
Treasury Stock, Beginning Balance, Shares at Mar. 31, 2018					(493,994)
Net earnings (unaudited)	37,633			37,633
Stock option exercises (unaudited)	964	$ 1	963
Stock option exercises, Shares		46,188
Restricted stock grant (unaudited)	523		523
Restricted stock grant (unaudited), Shares		10,710
Cash dividends declared	(14,466)			(14,466)
Change in unrealized gain in investment securities available-for-sale, net of related income taxes (unaudited)	(9,217)						(9,217)
Shares purchased (redeemed) in connection with directors' deferred compensation plan, net (unaudited)					$ (128)	128
Shares purchased (redeemed) in connection with directors' deferred compensation plan, net, Shares					2,824
Stock option expense (unaudited)	377		377
Reclassification of unrealized gain in equity securities at December 31, 2017 from accumulated other comprehensive earnings to retained earnings (unaudited)				21			(21)
Ending Balance at Jun. 30, 2018	$ 985,628	$ 677	439,731	556,615	$ (7,419)	7,419	(11,395)
Ending Balance, Shares at Jun. 30, 2018		67,669,658
Treasury Stock, Ending Balance, Shares at Jun. 30, 2018	(491,170)				(491,170)
Beginning Balance at Dec. 31, 2018	$ 1,053,295	$ 678	443,114	606,658	$ (7,507)	7,507	2,845
Beginning Balance, Shares at Dec. 31, 2018		67,753,133
Treasury Stock, Beginning Balance, Shares at Dec. 31, 2018	(467,811)				(467,811)
Net earnings (unaudited)	$ 80,345			80,345
Stock option exercises (unaudited)	3,186	$ 2	3,184
Stock option exercises, Shares		168,349
Restricted stock grant (unaudited)	1,426		1,426
Restricted stock grant (unaudited), Shares		47,532
Cash dividends declared	(30,531)			(30,531)
Change in unrealized gain in investment securities available-for-sale, net of related income taxes (unaudited)	56,402						56,402
Shares purchased (redeemed) in connection with directors' deferred compensation plan, net (unaudited)					$ (316)	316
Shares purchased (redeemed) in connection with directors' deferred compensation plan, net, Shares					2,709
Stock option expense (unaudited)	625		625
Two-for-one stock split in the form of a 100% stock dividend (unaudited)		$ 678		(678)
Two-for-one stock split in the form of a 100% stock dividend (unaudited), shares		67,840,210			(464,339)
Ending Balance at Jun. 30, 2019	$ 1,164,748	$ 1,358	448,349	655,794	$ (7,823)	7,823	59,247
Ending Balance, Shares at Jun. 30, 2019		135,809,224
Treasury Stock, Ending Balance, Shares at Jun. 30, 2019	(929,441)				(929,441)
Beginning Balance at Mar. 31, 2019	$ 1,107,522	$ 1,356	445,672	629,988	$ (7,660)	7,660	30,506
Beginning Balance, Shares at Mar. 31, 2019		135,680,420
Treasury Stock, Beginning Balance, Shares at Mar. 31, 2019					(928,678)
Net earnings (unaudited)	42,093			42,093
Stock option exercises (unaudited)	940	$ 2	938
Stock option exercises, Shares		81,272
Restricted stock grant (unaudited)	1,426		1,426
Restricted stock grant (unaudited), Shares		47,532
Cash dividends declared	(16,287)			(16,287)
Change in unrealized gain in investment securities available-for-sale, net of related income taxes (unaudited)	28,741						28,741
Shares purchased (redeemed) in connection with directors' deferred compensation plan, net (unaudited)	0				$ (163)	163
Shares purchased (redeemed) in connection with directors' deferred compensation plan, net, Shares					(763)
Stock option expense (unaudited)	313		313
Ending Balance at Jun. 30, 2019	$ 1,164,748	$ 1,358	$ 448,349	$ 655,794	$ (7,823)	$ 7,823	$ 59,247
Ending Balance, Shares at Jun. 30, 2019		135,809,224
Treasury Stock, Ending Balance, Shares at Jun. 30, 2019	(929,441)				(929,441)

Consolidated Statements of Sh_2

Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Cash dividend per share	$ 0.12	$ 0.11	$ 0.23	$ 0.20
Common Stock Dividend Percentage			100.00%
Retained Earnings [Member]
Cash dividend per share	$ 0.012	$ 0.11	$ 0.23	$ 0.20

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net earnings	$ 80,345	$ 72,152
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	5,946	6,433
Provision for loan losses	1,565	2,415
Securities premium amortization (discount accretion), net	12,217	14,109
Gain (loss) on sale of assets, net	824	(1,245)
Deferred federal income tax expense (benefit)	2,206	(908)
Change in loans held-for-sale	(631)	(9,009)
Change in other assets	1,021	(1,192)
Change in other liabilities	5,219	6,218
Total adjustments	28,367	16,821
Net cash provided by operating activities	108,712	88,973
CASH FLOWS FROM INVESTING ACTIVITIES:
Cash received in acquisition of Commercial Bancshares, Inc.		18,653
Net decrease in interest-bearing time deposits in banks	498
Activity in available-for-sale securities:
Sales	66,052	149,125
Maturities	2,201,877	3,208,139
Purchases	(2,280,686)	(3,471,387)
Net increase in loans	(88,629)	(80,480)
Purchases of bank premises and equipment and other assets	(6,360)	(8,544)
Proceeds from sale of bank premises and equipment and other assets	187	776
Net cash used in investing activities	(107,061)	(183,718)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase (decrease) in noninterest-bearing deposits	51,445	(97,737)
Net increase in interest-bearing deposits	137,932	3,481
Net increase (decrease) in borrowings	(106,701)	125,935
Common stock transactions:
Proceeds from stock issuances	3,186	2,319
Dividends paid	(28,463)	(25,434)
Net cash provided by financing activities	57,399	8,564
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	59,050	(86,181)
CASH AND CASH EQUIVALENTS, beginning of period	248,647	372,347
CASH AND CASH EQUIVALENTS, end of period	307,697	286,166
SUPPLEMENTAL INFORMATION AND NONCASH TRANSACTIONS:
Interest paid	15,062	8,074
Federal income taxes paid	12,752	12,762
Transfer of loans and bank premises to other real estate	364	126
Investment securities purchased but not settled	29,355
Restricted Stock Grant to Officers and Directors	$ 1,426	523
Stocks issued in acquisition of Commercial Bancshares, Inc.		$ 58,087

Basis of Presentation

Basis of Presentation	6 Months Ended
	Jun. 30, 2019
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, 2019, we had 73 financial centers across Texas, with eleven locations in Abilene, three locations in Weatherford, two locations in Cleburne, Conroe, San Angelo, Stephenville and Granbury, and one location each in Acton, Albany, Aledo, Alvarado, Beaumont, Boyd, Bridgeport, Brock, Burleson, Cisco, Clyde, Cut and Shoot, Decatur, Eastland, El Campo, Fort Worth, Fulshear, Glen Rose, Grapevine, Hereford, Huntsville, Keller, Kingwood, Magnolia, Mauriceville, Merkel, Midlothian, Mineral Wells, Montgomery, Moran, New Waverly, Newton, Odessa, Orange, Palacios, Port Arthur, Ranger, Rising Star, Roby, Southlake, Spring, Sweetwater, Tomball, Trent, Trophy Club, Vidor, Waxahachie, Willis and Willow Park, all in Texas. Our trust subsidiary has eight locations which are located in Abilene, Fort Worth, Houston, Odessa, Beaumont, San Angelo, Stephenville and Sweetwater. 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, 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 and Stock Repurchas

Stock Split and Stock Repurchase	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Stock Repurchase	Note 2 – Stock Split and Stock Repurchase On April 23, 2019, the Company’s Board of Directors declared a two-for-one stock split 100 May 15, 2019 June 3, 2019 On July 25, 2017, the Company’s Board of Directors authorized the repurchase of up to 2,000,000 common shares through September 30, 2020 no no

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 30, 2019
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 months ended June 30, 2019 and 2018, the Company assumes that all dilutive outstanding options to purchase common shares have been exercised at the beginning of the period (or the time of issuance, if later). The dilutive effect of these outstanding options and the restricted shares is reflected by application of the treasury stock method, whereby the proceeds from exercised options and restricted shares are assumed to be used to purchase common shares 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, 2019 and 2018 were 135,650,599 and 135,194,550 shares, respectively. The weighted average common shares outstanding used in computing basic earnings per common share for the six months ended June 30, 2019 and 2018 were 135,572,859 and 135,124,672. The weighted average common shares outstanding used in computing fully diluted earnings per common share for the three months ended June 30, 2019 and 2018 were 136,218,235 and 135,848,336 shares, respectively. The weighted average common shares outstanding used in computing fully diluted earnings per common share for the six months ended June 30, 2019 and 2018 were 136,195,811 and 135,735,930. For the three and six months ended June 30, 2019 and 2018, there were no stock options that were anti-dilutive that have been excluded from the EPS calculation.

Interest-bearing Time Deposits

Interest-bearing Time Deposits in Banks and Securities	6 Months Ended
	Jun. 30, 2019
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 $ 960 1,458 1,458 one Management classifies debt and equity securities as held-to-maturity, available-for-sale, held-to-maturity held-to-maturity available-for-sale Available-for-sale available-for-sale Effective January 1, 2018, in accordance with ASU 2016-01 The Company records its available-for-sale When the fair value of a debt 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 held-to-maturity The Company’s investment portfolio consists of U.S. Treasury securities, 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 prices supplied by the independent pricing services by comparison to prices obtained from other third-party sources on a quarterly basis. A summary of the Company’s available-for-sale June 30, 2019 Amortized Gross Gross Estimated U.S. Treasury securities $ 9,984 $ 36 $ — $ 10,020 Obligations of states and political subdivisions 1,103,682 53,593 (61 ) 1,157,214 Corporate bonds and other 4,643 51 — 4,694 Residential mortgage-backed securities 1,579,544 19,732 (3,101 ) 1,596,175 Commercial mortgage-backed securities 484,919 6,929 (459 ) 491,389 Total securities available-for-sale $ 3,182,772 $ 80,341 $ (3,621 ) $ 3,259,492 June 30, 2018 Amortized Gross Gross Estimated U.S. Treasury Securities $ 9,957 $ 8 $ — $ 9,965 Obligations of U.S. government sponsored enterprises and agencies 304 — (1 ) 303 Obligations of states and political subdivisions 1,257,547 29,924 (2,696 ) 1,284,775 Corporate bonds and other 4,861 — (79 ) 4,782 Residential mortgage-backed securities 1,464,345 1,630 (30,718 ) 1,435,257 Commercial mortgage-backed securities 471,398 — (8,913 ) 462,485 Total securities available-for-sale $ 3,208,412 $ 31,562 $ (42,407 ) $ 3,197,567 December 31, 2018 Amortized Gross Gross Estimated U.S. Treasury securities $ 9,970 $ — $ (8 ) $ 9,962 Obligations of U.S. government sponsored enterprises and agencies 301 — — 301 Obligations of states and political subdivisions 1,229,828 30,013 (1,970 ) 1,257,871 Corporate bonds and other 4,875 — (77 ) 4,798 Residential mortgage-backed securities 1,472,228 3,928 (21,611 ) 1,454,545 Commercial mortgage-backed securities 436,366 670 (5,736 ) 431,300 Total securities available-for-sale $ 3,153,568 $ 34,611 $ (29,402 ) $ 3,158,777 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, 2019 were computed by using scheduled amortization of balances and historical prepayment rates. At June 30, 2019 and 2018, and December 31, 2018, 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 Amortized Estimated Due within one year $ 165,912 $ 167,217 Due after one year through five years 483,916 506,941 Due after five years through ten years 466,755 495,582 Due after ten years 1,726 2,188 Mortgage-backed securities 2,064,463 2,087,564 Total $ 3,182,772 $ 3,259,492 The following tables disclose the Company’s investment securities that have been in a continuous unrealized-loss Less than 12 Months 12 Months or Longer Total June 30, 2019 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Obligations of states and political subdivisions $ — $ — $ 9,777 $ 61 $ 9,777 $ 61 Residential mortgage-backed securities 17,594 77 404,946 3,024 422,540 3,101 Commercial mortgage-backed securities — — 134,881 459 134,881 459 Total $ 17,594 $ 77 $ 549,604 $ 3,544 $ 567,198 $ 3,621 Less than 12 Months 12 Months or Longer Total June 30, 2018 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Obligations of U.S. government sponsored enterprises and agencies $ 303 $ 1 $ — $ — $ 303 $ 1 Obligations of states and political subdivisions 136,950 1,122 43,239 1,574 180,189 2,696 Corporate bonds and other 4,617 76 233 3 4,850 79 Residential mortgage-backed securities 1,073,327 21,838 227,155 8,880 1,300,482 30,718 Commercial mortgage-backed securities 379,201 7,477 83,285 1,436 462,486 8,913 Total $ 1,594,398 $ 30,514 $ 353,912 $ 11,893 $ 1,948,310 $ 42,407 Less than 12 Months 12 Months or Longer Total December 31, 2018 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized U.S. Treasury securities $ 9,962 $ 8 $ — $ — $ 9,962 $ 8 Obligations of U.S. government sponsored enterprises and agencies — — 301 — 301 — Obligations of state and political subdivisions 27,489 107 114,461 1,863 141,950 1,970 Corporate bonds and other 4,348 68 450 9 4,798 77 Residential mortgage-backed securities 119,584 483 922,289 21,128 1,041,873 21,611 Commercial mortgage-backed securities 1,994 5 343,015 5,731 345,009 5,736 Total $ 163,377 $ 671 $ 1,380,516 $ 28,731 $ 1,543,893 $ 29,402 The number of investments in an unrealized loss position totaled 109 at June 30, 2019. 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, 2019 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, 2019, 84.95% of our available-for-sale At June 30, 2019, $2,137,620,000 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 three months ended June 30, 2019 and 2018, sales of investment securities that were classified as available-for-sale 65,821 57,680 During the six months ended June 30, 2019 and 2018, sales of investment securities classified as available-for-sale 66,052 149,125 six-month six-month The specific identification method was used to determine cost in order to compute the realized gains and losses.

Loans Held for Investment and A

Loans Held for Investment and Allowance for Loan Losses	6 Months Ended
	Jun. 30, 2019
Receivables [Abstract]
Loans Held for Investment and Allowance for Loan Losses	Note 5 – Loans Held for Investment 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 estimated loss emergence periods; 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 decline in the economy could result in increased levels of non-performing 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. charged-off charge-off 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 less cost to sell. Other loan impairments for non-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 non-accrual 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 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. Subsequent to the acquisition date, increases in expected cash flows will generally result in a recovery of any previously recorded allowance for loan loss, to the extent applicable, and/or a reclassification from the nonaccretable difference to accretable yield, which will be recognized prospectively. 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, 2019 and 2018 and December 31, 2018 were $464,000, $2,813,000 and $827,000, respectively, compared to a contractual balance of $750,000, $3,918,000 and $1,157,000, respectively. Other purchased credit impaired loan disclosures were omitted due to immateriality. Loans held-for-investment June 30, December 31, 2019 2018 2018 Commercial $ 813,887 $ 775,010 $ 844,953 Agricultural 97,535 92,583 96,677 Real estate 2,730,585 2,567,878 2,639,346 Consumer 398,945 396,009 372,660 Total loans held-for-investment $ 4,040,952 $ 3,831,480 $ 3,953,636 The Company’s non-accrual June 30, December 31, 2019 2018 2018 Non-accrual $ 26,408 $ 26,685 $ 27,534 Loans still accruing and past due 90 days or more 300 200 1,008 Troubled debt restructured loans** 471 514 513 Total $ 27,179 $ 27,399 $ 29,055 * Includes $464,000, $2,813,000 and $827,000 of purchased credit impaired loans as of June 30, 2019 and 2018, and December 31, 2018, respectively. ** Troubled debt restructured loans of $3,906,000, $4,329,000 and $3,840,000, whose interest collection, after considering economic and business conditions and collection efforts, is doubtful are included in non-accrual The Company’s recorded investment in impaired loans and the related valuation allowance are as follows (in thousands): June 30, 2019 June 30, 2018 December 31, 2018 Recorded Investment Valuation Allowance Recorded Investment Valuation Allowance Recorded Investment Valuation Allowance $26,408 $ 3,866 $ 26,685 $ 4,823 $ 27,534 $ 4,069 The Company had $27,860,000, $28,104,000 and $29,632,000 in non-accrual, Non-accrual June 30, December 31, 2019 2018 2018 Commercial $ 8,189 $ 7,580 $ 9,334 Agricultural 1,047 1,259 759 Real estate 16,787 16,715 16,714 Consumer 385 1,131 727 Total $ 26,408 $ 26,685 $ 27,534 No The Company’s impaired loans and related allowance 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, 2019 Unpaid Contractual Principal Balance Recorded Investment With No Allowance* Recorded Investment With Allowance Total Recorded Investment Related Allowance Year- to-date Average Recorded Investment Three- Month Average Recorded Investment Commercial $ 9,340 $ 6,212 $ 1,977 $ 8,189 $ 1,022 $ 8,699 $ 8,562 Agricultural 1,108 434 613 1,047 119 1,090 1,071 Real Estate 24,262 5,034 11,753 16,787 2,515 18,054 17,105 Consumer 525 27 358 385 210 465 427 Total $ 35,235 $ 11,707 $ 14,701 $ 26,408 $ 3,866 $ 28,308 $ 27,165 * Includes $464,000 of purchased credit impaired loans. June 30, 2018 Unpaid Contractual Principal Balance Recorded Investment With No Allowance* Recorded Investment With Allowance Total Recorded Investment Related Allowance Year- to-date Average Recorded Investment Three- Average Recorded Investment Commercial $ 9,432 $ 3,264 $ 4,316 $ 7,580 $ 1,379 $ 8,485 $ 8,226 Agricultural 1,278 50 1,209 1,259 368 1,670 1,589 Real Estate 22,358 3,569 13,146 16,715 2,645 18,441 18,019 Consumer 1,344 169 962 1,131 431 1,240 1,192 Total $ 34,412 $ 7,052 $ 19,633 $ 26,685 $ 4,823 $ 29,836 $ 29,026 * Includes $2,813,000 of purchased credit impaired loans. December 31, 2018 Unpaid Contractual Principal Balance Recorded Investment With No Allowance* Recorded Investment With Allowance Total Recorded Investment Related Allowance 12 Month Average Recorded Investment Commercial $ 10,808 $ 6,728 $ 2,606 $ 9,334 $ 1,133 $ 7,986 Agricultural 799 213 546 759 170 842 Real Estate 24,072 6,699 10,015 16,714 2,409 16,042 Consumer 935 101 626 727 357 914 Total $ 36,614 $ 13,741 $ 13,793 $ 27,534 $ 4,069 $ 25,784 * Includes $827,000 of purchased credit impaired loans. The Company recognized interest income on impaired loans prior to being recognized as impaired of approximately $948,000 during the year ended December 31, 2018. Such amounts for the three-month and six-month 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 Credits rated special mention show clear signs of financial weaknesses 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 June 30, 2019 Pass Special Substandard Doubtful Total Commercial $ 767,275 $ 31,124 $ 15,488 $ — $ 813,887 Agricultural 94,481 58 2,996 — 97,535 Real Estate 2,656,139 20,044 54,402 — 2,730,585 Consumer 397,017 264 1,664 — 398,945 Total $ 3,914,912 $ 51,490 $ 74,550 $ — $ 4,040,952 June 30, 2018 Pass Special Substandard Doubtful Total Commercial $ 749,387 $ 6,439 $ 19,184 $ — $ 775,010 Agricultural 87,768 1,568 3,247 — 92,583 Real Estate 2,487,399 26,182 54,297 — 2,567,878 Consumer 393,200 368 2,441 — 396,009 Total $ 3,717,754 $ 34,557 $ 79,169 $ — $ 3,831,480 December 31, 2018 Pass Special Substandard Doubtful Total Commercial $ 804,584 $ 23,392 $ 16,977 $ — $ 844,953 Agricultural 92,864 46 3,767 — 96,677 Real Estate 2,559,379 26,626 53,341 — 2,639,346 Consumer 370,510 315 1,835 — 372,660 Total $ 3,827,337 $ 50,379 $ 75,920 $ — $ 3,953,636 The Company’s past due loans are as follows (in thousands): June 30, 2019 15-59 Past Due* 60-89 Past Due Greater Days Total Past Due Current Total Loans 90 Days Commercial $ 2,671 $ 352 $ 610 $ 3,633 $ 810,254 $ 813,887 $ 58 Agricultural 315 163 30 508 97,027 97,535 30 Real Estate 16,130 712 865 17,707 2,712,878 2,730,585 180 Consumer 821 99 40 960 397,985 398,945 32 Total $ 19,937 $ 1,326 $ 1,545 $ 22,808 $ 4,018,144 $ 4,040,952 $ 300 June 30, 2018 15-59 Past Due* 60-89 Past Due Greater Days Total Past Due Current Total Loans 90 Days Commercial $ 4,950 $ 1,085 $ 3,029 $ 9,064 $ 765,946 $ 775,010 $ 74 Agricultural 626 159 — 785 91,798 92,583 — Real Estate 13,441 474 532 14,447 2,553,431 2,567,878 70 Consumer 919 232 76 1,227 394,782 396,009 56 Total $ 19,936 $ 1,950 $ 3,637 $ 25,523 $ 3,805,957 $ 3,831,480 $ 200 December 31, 2018 15-59 Past Due* 60-89 Past Due Greater Days Total Past Due Total Current Total Loans Total 90 Past Due Still Commercial $ 3,546 $ 682 $ 677 $ 4,905 $ 840,048 $ 844,953 $ — Agricultural 791 19 26 836 95,841 96,677 — Real Estate 13,185 881 2,020 16,086 2,623,260 2,639,346 960 Consumer 782 263 54 1,099 371,561 372,660 48 Total $ 18,304 $ 1,845 $ 2,777 $ 22,926 $ 3,930,710 $ 3,953,636 $ 1,008 * 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 by portfolio segment (in thousands). There were no June 30, 2019 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,022 $ 119 $ 2,515 $ 210 $ 3,866 Loans collectively evaluated for impairment 12,877 1,241 28,284 5,552 47,954 Total $ 13,899 $ 1,360 $ 30,799 $ 5,762 $ 51,820 June 30, 2018 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,379 $ 368 $ 2,645 $ 431 $ 4,823 Loans collectively evaluated for impairment 7,839 1,034 30,598 5,657 45,128 Total $ 9,218 $ 1,402 $ 33,243 $ 6,088 $ 49,951 December 31, 2018 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,133 $ 170 $ 2,409 $ 357 $ 4,069 Loans collectively evaluated for impairment 10,815 1,276 29,933 5,109 47,133 Total $ 11,948 $ 1,446 $ 32,342 $ 5,466 $ 51,202 Changes in the allowance for loan losses are summarized as follows by portfolio segment (in thousands): Three months ended June 30, 2019 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 12,475 $ 1,430 $ 31,887 $ 5,793 $ 51,585 Provision for loan losses 1,418 61 (929 ) 50 600 Recoveries 423 5 60 209 697 Charge-offs (417 ) (136 ) (219 ) (290 ) (1,062 ) Ending balance $ 13,899 $ 1,360 $ 30,799 $ 5,762 $ 51,820 Three months ended June 30, 2018 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 9,277 $ 1,512 $ 32,539 $ 6,171 $ 49,499 Provision for loan losses 335 (115 ) 799 86 1,105 Recoveries 126 5 18 147 296 Charge-offs (520 ) — (113 ) (316 ) (949 ) Ending balance $ 9,218 $ 1,402 $ 33,243 $ 6,088 $ 49,951 Six months ended June 30, 2019 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 11,948 $ 1,446 $ 32,342 $ 5,466 $ 51,202 Provision for loan losses 1,612 42 (531 ) 442 1,565 Recoveries 1,073 7 149 349 1,578 Charge-offs (734 ) (135 ) (1,161 ) (495 ) (2,525 ) Ending balance $ 13,899 $ 1,360 $ 30,799 $ 5,762 $ 51,820 Six months ended June 30, 2018 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 10,865 $ 1,305 $ 29,896 $ 6,090 $ 48,156 Provision for loan losses (1,292 ) 88 3,233 386 2,415 Recoveries 284 9 260 247 800 Charge-offs (639 ) — (146 ) (635 ) (1,420 ) Ending balance $ 9,218 $ 1,402 $ 33,243 $ 6,088 $ 49,951 The Company’s recorded investment in loans related to the balance in the allowance for loan losses on the basis of the Company’s impairment methodology is as follows (in thousands). Purchased credit impaired loans of $464,000, $2,813,000 and $827,000 at June 30, 2019 and 2018, and December 31, 2018, respectively, are included in loans individually evaluated for impairment. June 30, 2019 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 8,189 $ 1,047 $ 16,787 $ 385 $ 26,408 Loans collectively evaluated for impairment 805,698 96,488 2,713,798 398,560 4,014,544 Total $ 813,887 $ 97,535 $ 2,730,585 $ 398,945 $ 4,040,952 June 30, 2018 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 7,580 $ 1,259 $ 16,715 $ 1,131 $ 26,685 Loans collectively evaluated for impairment 767,430 91,324 2,551,163 394,878 3,804,795 Total $ 775,010 $ 92,583 $ 2,567,878 $ 396,009 $ 3,831,480 December 31, 2018 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 9,334 $ 759 $ 16,714 $ 727 $ 27,534 Loan collectively evaluated for impairment 835,619 95,918 2,622,632 371,933 3,926,102 Total $ 844,953 $ 96,677 $ 2,639,346 $ 372,660 $ 3,953,636 The Company’s loans that were modified and considered troubled debt restructurings are as follows (in thousands): Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 Number Pre- Post- Number Pre- Post- Commercial 2 $ 122 $ 122 3 $ 279 $ 279 Agricultural 2 253 253 10 619 619 Real Estate — — — 4 650 650 Consumer — — — — — — Total 4 $ 375 $ 375 17 $ 1,548 $ 1,548 Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Number Pre- Post- Number Pre- Post- Commercial 1 $ 279 $ 279 1 $ 279 $ 279 Agricultural — — — 1 4 4 Real Estate 2 162 162 4 525 525 Consumer 3 39 39 6 113 113 Total 6 $ 480 $ 480 12 $ 921 $ 921 The balances below provide information as to how the loans were modified as troubled debt restructured loans (in thousands): Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 Adjusted Extended Combined Maturity Adjusted Extended Combined Maturity Commercial $ — $ 122 $ — $ — $ 279 $ — Agricultural — 253 — — 354 265 Real Estate — — — — 202 448 Consumer — — — — — — Total $ — $ 375 $ — $ — $ 835 $ 713 Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Adjusted Extended Combined Maturity Adjusted Extended Combined Maturity Commercial $ — $ — $ 279 — $ — $ 279 Agricultural — — — — — 4 Real Estate — 162 — — 162 363 Consumer — — 39 — — 113 Total $ — $ 162 $ 318 — $ 162 $ 759 During the three months ended June 30, 2019 and 2018, no loans were modified as a troubled debt restructured loan within the previous 12 months and for which there was a payment default. During the six months ended June 30, 2019 and 2018, no loans were modified as a troubled debt restricted during 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. As of June 30, 2019, the Company has no 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, 2019, $2,563,225,000 in loans held by our bank subsidiary were subject to blanket liens as security for this line of credit. At June 30, 2019, there were no advances or letters of credit outstanding under this line of credit.

Loans Held for Sale

Loans Held for Sale	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Loans Held for Sale	Note 6 Loans Held for Sale The Company originates certain mortgage loans for sale in the secondary market. The mortgage loan sales contracts contain indemnification clauses should the loans default, generally in the first three to nine 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 held for sale totaled $22,305,000, $24,289,000 and $21,672​​​​​​​,000 at June 30, 2019 and 2018, and December 31, 2018, respectively. At June 30, 2019 and 2018, and December 31, 2018, $3,324,000, $19,228,000 and $2,487,000 are valued at the lower of cost or fair value, and the remaining amounts are valued under the fair value option. The change to the fair value option for loans held for sale was effective at June 30, 2018 and was done in conjunction with the Company’s move to mandatory delivery in the secondary market and the purchase of forward mortgage-backed securities to manage the changes in fair value (see note 7 for additional information).

Derivative Financial Instrument

Derivative Financial Instruments	6 Months Ended
	Jun. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Note 7 Derivative Financial Instruments The Company enters into interest rate lock commitments (“IRLCs”) with customers to originate residential mortgage loans at a specific interest rate that are ultimately sold in the secondary market. These commitments, which contain fixed expiration dates, offer the borrower an interest rate guarantee provided the loan meets underwriting guidelines and closes within the timeframe established by the Company. Beginning in the second quarter of 2018, the Company purchased forward mortgage-backed securities contracts to manage the changes in fair value associated with changes in interest rates related to a portion of the IRLCs. These instruments are typically entered into at the time the IRLC is made. These financial instruments are not designated as hedging instruments and are used for asset and liability management needs. All derivatives are carried at fair value in either other assets or other liabilities. The fair values of IRLCs are based on current secondary market prices for underlying loans and estimated servicing value with similar coupons, maturity and credit quality, subject to the anticipated loan funding probability (pull-through rate). The fair value of IRLCs is subject to change primarily due to changes in interest rates and the estimated pull-through rate. These commitments are classified as Level 2 in the fair value disclosures (see note 12), as the valuations are based on observable market inputs. Forward mortgage-backed securities contracts are exchange-traded or traded within highly active dealer markets. In order to determine the fair value of these instruments, the Company utilizes the exchange price or dealer market price for the particular derivative contract and these instruments are therefore classified as Level 2 in the fair value disclosures (see note 12). The estimated fair values are subject to change primarily due to changes in interest rates. The following table provides the outstanding notional balances and fair values of outstanding derivative positions (dollars in thousands): June 30, 2019: Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value IRLCs $ 89,655 $ 1,525 $ — Forward mortgage-backed securities trades 72,500 — 254 June 30, 2018: Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value IRLCs $ 61,520 $ 501 $ — Forward mortgage-backed securities trades 17,500 — 47 December 31, 2018: Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value IRLCs $ 37,088 $ 765 $ — Forward mortgage-backed securities trades 45,500 — 403

Borrowings

Borrowings	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Short-term Debt [Text Block]	Note 8 – Borrowings Borrowings consisted of the following (dollars in thousands): June 30, December 31, 2019 2018 2018 Securities sold under agreements with customers to repurchase $ 356,555 $ 389,010 $ 409,631 Federal funds purchased 5,450 7,925 4,075 Advances from Federal Home Loan Bank of Dallas — 60,000 55,000 Total $ 362,005 $ 456,935 $ 468,706 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 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”

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Note 9 Income Taxes Income tax expense was $8,594,000 for the second quarter of 2019 as compared to $7,217,000 for the same period in 2018. The Company’s effective tax rates on pretax income were 16.96% and 16.09% for the second quarters of 2019 and 2018, respectively. Income tax expense was $15,959,000 for the six months ended June 30, 2019 as compared to $13,462,000 for the same period in 2018. The Company’s effective tax rates on pretax income were 16.57% and 15.72% for the six months ended June 2019 and 2018, respectively. The effective tax rates differ from the statutory federal tax rate of 21% primarily due to tax exempt interest income earned on certain investment securities and loans, the deductibility of dividends paid to our employee stock ownership plan and excess tax benefits related to our directors’ deferred compensation plan.

Stock Option Plan and Restricte

Stock Option Plan and Restricted Stock Plan	6 Months Ended
	Jun. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option Plan and Restricted Stock Plan	Note 10 Stock Option Plan and Restricted Stock Plan 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. On June 26, 2019, the Company granted 398,850 incentive stock options with an exercise price of $29.70 per share. The fair value of the options was $7.31 per option and was estimated using the Black-Scholes options pricing model with the following weighted average assumptions: risk free interest rate of 1.83%; expected dividend yield of 1.62%; expected life of 6.64 years; and expected volatility of 26.69%. No options were granted in 2018. The Company recorded stock option expense totaling $313,000 and $377,000 for the three-month periods ended June 30, 2019 and 2018, respectively. The Company recorded stock option expense totaling $625,000 and $754,000 for the six months ended June 30, 2019 and 2018, respectively. The additional disclosure requirements under authoritative accounting guidance have been omitted due to the amounts being insignificant. On April 25, 2017, upon re-election non-employee re-election non-employee re-election non-employee On October 27, 2015, the Company granted 62,546 restricted shares with a total value of $1,060,000 to certain officers that was expensed over the vesting period of three years three years three-year six-month

Pension Plan

Pension Plan	6 Months Ended
	Jun. 30, 2019
Retirement Benefits [Abstract]
Pension Plan	Note 11 Pension Plan The Company’s defined benefit pension plan was frozen effective January 1, 2004, whereby no new participants were added to the plan and no additional years of service were accrued to participants. 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. As a result of its evaluation of its funding status, the Company made no contribution in 2018, and has not made a contribution through June 30, 2019. In December 2018, due to the rising interest rate environment, the Company determined it was in the best of interest of its shareholders to settle its pension obligation to its retiree group in payout, approximately 53% of the pension benefit obligation on that date, and recorded a loss on settlement totaling $1,546,000 for the year ended December 31, 2018. In 2019, the Company made a decision to terminate and settle the remaining obligation in its pension plan with an effective termination date of June 30, 2019, following which date the Company is obligated to settle the Company’s remaining obligations of the plan upon receipt of regulatory approval. Final settlement of the Company’s remaining obligation under the plan is expected to be made in the fourth quarter of 2019 or first or second quarter of 2020, subject to regulatory approval. In addition, the Company had a multiple employer pension plan related to its acquisition of Orange Savings Bank in 2013. This plan was likewise frozen. During the first quarter of 2019, the Company made a decision to remove this plan from the multiple employer plan and merge it into the Company’s existing pension plan. The Company recorded $900,000 in pension merger expense for the three months ended March 31, 2019 in connection with this merger of the Orange pension plan. In May 2019, the Company assumed the Orange pension obligation of $2,740,000 and received related assets totaling $1,829,000. Net periodic benefit costs totaling $19,000 and $56,000 were recorded for the three months ended June 30, 2019 and 2018, respectively. Net periodic benefit costs totaling $942,000 and $111,000 were recorded for the six months ended June 30, 2019 and 2018, respectively, which includes the Orange pension merger costs discussed above.

Fair Value Disclosures

Fair Value Disclosures	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Disclosures	Note 12 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 – • Level 2 Inputs – • 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 See notes 6 and 7 related to the determination of fair value for loans held-for-sale, There were no transfers between Level 1 and Level 2 or Level 2 and Level 3 during the three and six months ended June 30, 2019 and 2018, and the year ended December 31, 2018. The following table summarizes the Company’s available-for-sale June 30, 2019 Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value Available-for-sale U.S. Treasury securities $ 10,020 $ — $ — $ 10,020 Obligations of states and political subdivisions — 1,157,214 — 1,157,214 Corporate bonds — 228 — 228 Residential mortgage-backed securities — 1,596,175 — 1,596,175 Commercial mortgage-backed securities — 491,389 — 491,389 Other securities 4,466 — — 4,466 Total $ 14,486 $ 3,245,006 $ — $ 3,259,492 Loans held-for-sale $ — $ 18,981 $ — $ 18,981 IRLCs $ — $ 1,525 $ — $ 1,525 Forward mortgage-backed securities trades $ — $ 254 $ — $ 254 June 30, 2018 Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value Available-for-sale U.S. Treasury securities $ 9,965 $ — $ — $ 9,965 Obligations of U. S. government sponsored enterprises and agencies — 303 — 303 Obligations of states and political subdivisions — 1,284,775 — 1,284,775 Corporate bonds — 451 — 451 Residential mortgage-backed securities — 1,435,257 — 1,435,257 Commercial mortgage-backed securities — 462,485 — 462,485 Other securities 4,331 — — 4,331 Total $ 14,296 $ 3,183,271 $ — $ 3,197,567 Loans held-for-sale $ $ 5,061 $ — $ 5,061 IRLCs $ $ 501 $ — $ 501 Forward mortgage-backed securities trades $ — $ 47 $ — $ 47 December 31, 2018 Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value Available-for-sale U.S. Treasury securities $ 9,962 $ — $ — $ 9,962 Obligations of U. S. government sponsored enterprises and agencies — 301 — 301 Obligations of states and political subdivisions — 1,257,871 — 1,257,871 Corporate bonds — 450 — 450 Residential mortgage-backed securities — 1,454,545 — 1,454,545 Commercial mortgage-backed securities — 431,300 — 431,300 Other securities 4,348 — — 4,348 Total $ 14,310 $ 3,144,467 $ — $ 3,158,777 Loans held-for-sale $ — $ 19,185 $ — $ 19,185 IRLCs $ — $ 765 $ — $ 765 Forward mortgage-backed securities trades $ — $ 403 $ — $ 403 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 Impaired Loans – Impaired loans are reported at the fair value of the underlying collateral less selling costs if repayment is expected solely from the collateral. Collateral values are estimated using Level 2 inputs based on observable market data. At June 30, 2019, impaired loans with a carrying value of $14,701,000 were reduced by specific valuation reserves totaling $3,866,000 resulting in a net fair value of $10,835,000. The Company also had impaired loans of $11,707,000 with no specific valuation reserve at June 30, 2019, due to the loans carrying value generally being lower than the value of the collateral associated with the loan. Loans Held-for-Sale held-for-sale Certain non-financial non-financial non-recurring non-financial Non-financial non-recurring re-measured Re-evaluation The following table presents other real estate owned that were re-measured Three Months Ended June 30, 2019 2018 Carrying value of other real estate owned prior to re-measurement $ — $ 526 Write-downs included in gain (loss) on sale of other real estate owned — (126 ) Fair value $ — $ 400 Six Months Ended June 30, 2019 2018 Carrying value of other real estate owned prior to re-measurement $ — $ 526 Write-downs included in gain (loss) on sale of other real estate owned — (126 ) Fair value $ — $ 400 At June 30, 2019 and 2018, and December 31, 2018, other real estate owned totaled $635,000, $642,000 and $448,000, 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 The estimated fair values and carrying values of all financial instruments under current authoritative guidance were as follows (in thousands). June 30, December 31, 2019 2018 2018 Carrying Estimated Carrying Estimated Carrying Estimated Fair Value Cash and due from banks $ 178,345 $ 178,345 $ 178,217 $ 178,217 $ 207,835 $ 207,835 Level 1 Federal funds sold 700 700 8,450 8,450 — — Level 1 Interest-bearing deposits in banks 128,652 128,652 99,499 99,499 40,812 40,812 Level 1 Interest-bearing time deposits in banks 960 960 1,458 1,458 1,458 1,458 Level 2 Available-for-sale 3,259,492 3,259,492 3,197,567 3,197,567 3,158,777 3,158,777 Levels 1 and 2 Loans held for investment 3,989,132 4,026,543 3,781,529 3,807,267 3,902,434 3,947,391 Level 3 Loans held for sale 22,305 22,347 24,289 24,550 21,672 21,779 Level 2 Accrued interest receivable 36,954 36,954 36,513 36,513 36,765 36,765 Level 2 Deposits with stated maturities 433,511 433,811 483,230 484,230 442,161 441,727 Level 2 Deposits with no stated maturities 5,936,255 5,936,255 5,727,377 5,727,377 5,738,228 5,738,228 Level 1 Borrowings 362,005 362,005 456,935 456,935 468,706 468,706 Level 2 Accrued interest payable 694 694 223 223 408 408 Level 2 IRLCs 1,525 1,525 501 501 765 765 Level 2 Forward mortgage backed securities trades 254 254 47 47 403 403 Level 2

Recently Issued Authoritative A

Recently Issued Authoritative Accounting Guidance	6 Months Ended
	Jun. 30, 2019
Accounting Changes and Error Corrections [Abstract]
Recently Issued Authoritative Accounting Guidance	Note 13 Recently Issued Authoritative Accounting Guidance Accounting Standards Update (“ASU”) 2014-09, “Revenue from Contracts with Customers 2014-09 2015-4 2014-09 2014-09, non-interest ASU 2016-01, ASU 2016-01 “Financial Instruments – Overall: Recognition and Measurement of Financial Assets and Financial Liabilities 2016-01, available-for-sale 2016-1 ASU 2016-02, “Leases 2016-02 right-of-use 2016-02 ASU 2016-13, “Financial Instruments – Credit Losses 2016-13 2016-13 2016-13 available-for-sale 2016-13 2016-13. 2016-13 ASU 2017-04, “Intangibles – Goodwill and Other 2017-04 2017-04 ASU 2018-02, “Income Statement – Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” 2018-02 2018-02 ASU 2018-13, “Fair Value Measurement – Changes to the Disclosure Requirements for Fair Value Measurement 2018-13 2018-13

Acquisition

Acquisition	6 Months Ended
	Jun. 30, 2019
Business Combinations [Abstract]
Acquisition	Note 14 – Acquisition On October 12, 2017 At closing, Commercial Bancshares, Inc. was merged into the Company and Commercial State Bank, Kingwood, Texas, was merged into First Financial Bank, National Association, Abilene, Texas, a wholly owned subsidiary of the Company. The primary purpose of the acquisition was to expand the Company’s market share around Houston. Factors that contributed to a purchase price resulting in goodwill include Commercial State Bank’s record of earnings, strong management and board of directors, strong local economic environment and opportunity for growth. The results of operations from this acquisition are included in the consolidated earnings of the Company commencing January 1, 2018. The following table presents the amounts recorded on the consolidated balance sheet on the acquisition date (dollars in thousands): Fair value of consideration paid: Common stock issued (1,289,371 shares) $ 58,087 Fair value of identifiable assets acquired: Cash and cash equivalents 18,653 Securities available-for-sale 64,501 Loans 266,327 Identifiable intangible assets 3,167 Other assets 15,375 Total identifiable assets acquired 368,023 Fair value of liabilities assumed: Deposits 341,902 Other liabilities (373 ) Total liabilities assumed 341,529 Fair value of net identifiable assets acquired 26,494 Goodwill resulting from acquisition $ 31,593 Goodwill recorded in the acquisition was accounted for in accordance with the authoritative business combination guidance. Accordingly, goodwill will not be amortized but will be tested for impairment annually. The goodwill recorded is not deductible for federal income tax purposes. The fair value of total loans acquired was $266,327,000 at acquisition compared to contractual amounts of $271,714,000. The fair value of purchased credit impaired loans at acquisition was $3,013,000 compared to contractual amounts of $3,806,000. Additional purchased credit impaired loan disclosures were omitted due to immateriality. All other acquired loans were considered performing loans.

Summary of Significant Accounti

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Investment Securities	Management classifies debt and equity securities as held-to-maturity, available-for-sale, held-to-maturity held-to-maturity available-for-sale The Company records its available-for-sale When the fair value of a debt 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 held-to-maturity The Company’s investment portfolio consists of U.S. Treasury securities, 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 prices supplied by the independent pricing services by comparison to prices obtained from other third-party sources on a quarterly basis.
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 estimated loss emergence periods; 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 decline in the economy could result in increased levels of non-performing 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. charged-off charge-off 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 less cost to sell. Other loan impairments for non-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 non-accrual 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 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. Subsequent to the acquisition date, increases in expected cash flows will generally result in a recovery of any previously recorded allowance for loan loss, to the extent applicable, and/or a reclassification from the nonaccretable difference to accretable yield, which will be recognized prospectively. 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, 2019 and 2018 and December 31, 2018 were $464,000, $2,813,000 and $827,000, respectively, compared to a contractual balance of $750,000, $3,918,000 and $1,157,000, respectively. Other purchased credit impaired loan disclosures were omitted due to immateriality.
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 – • Level 2 Inputs – • 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
Recently Issued Authoritative Accounting Guidance	Accounting Standards Update (“ASU”) 2014-09, “Revenue from Contracts with Customers 2014-09 2015-4 2014-09 2014-09, non-interest ASU 2016-01, ASU 2016-01 “Financial Instruments – Overall: Recognition and Measurement of Financial Assets and Financial Liabilities 2016-01, available-for-sale 2016-1 ASU 2016-02, “Leases 2016-02 right-of-use 2016-02 ASU 2016-13, “Financial Instruments – Credit Losses 2016-13 2016-13 2016-13 available-for-sale 2016-13 2016-13. 2016-13 ASU 2017-04, “Intangibles – Goodwill and Other 2017-04 2017-04 ASU 2018-02, “Income Statement – Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” 2018-02 2018-02 ASU 2018-13, “Fair Value Measurement – Changes to the Disclosure Requirements for Fair Value Measurement 2018-13 2018-13

Interest-bearing Time Deposit_2

Interest-bearing Time Deposits in Banks and Securities (Tables)	6 Months Ended
	Jun. 30, 2019
Cash and Cash Equivalents [Abstract]
Summary of Available-for-Sale Securities	A summary of the Company’s available-for-sale June 30, 2019 Amortized Gross Gross Estimated U.S. Treasury securities $ 9,984 $ 36 $ — $ 10,020 Obligations of states and political subdivisions 1,103,682 53,593 (61 ) 1,157,214 Corporate bonds and other 4,643 51 — 4,694 Residential mortgage-backed securities 1,579,544 19,732 (3,101 ) 1,596,175 Commercial mortgage-backed securities 484,919 6,929 (459 ) 491,389 Total securities available-for-sale $ 3,182,772 $ 80,341 $ (3,621 ) $ 3,259,492 June 30, 2018 Amortized Gross Gross Estimated U.S. Treasury Securities $ 9,957 $ 8 $ — $ 9,965 Obligations of U.S. government sponsored enterprises and agencies 304 — (1 ) 303 Obligations of states and political subdivisions 1,257,547 29,924 (2,696 ) 1,284,775 Corporate bonds and other 4,861 — (79 ) 4,782 Residential mortgage-backed securities 1,464,345 1,630 (30,718 ) 1,435,257 Commercial mortgage-backed securities 471,398 — (8,913 ) 462,485 Total securities available-for-sale $ 3,208,412 $ 31,562 $ (42,407 ) $ 3,197,567 December 31, 2018 Amortized Gross Gross Estimated U.S. Treasury securities $ 9,970 $ — $ (8 ) $ 9,962 Obligations of U.S. government sponsored enterprises and agencies 301 — — 301 Obligations of states and political subdivisions 1,229,828 30,013 (1,970 ) 1,257,871 Corporate bonds and other 4,875 — (77 ) 4,798 Residential mortgage-backed securities 1,472,228 3,928 (21,611 ) 1,454,545 Commercial mortgage-backed securities 436,366 670 (5,736 ) 431,300 Total securities available-for-sale $ 3,153,568 $ 34,611 $ (29,402 ) $ 3,158,777
Amortized Cost and Estimated Fair Value of Available-for-Sale Securities	The amortized cost and estimated fair value of available-for-sale Amortized Estimated Due within one year $ 165,912 $ 167,217 Due after one year through five years 483,916 506,941 Due after five years through ten years 466,755 495,582 Due after ten years 1,726 2,188 Mortgage-backed securities 2,064,463 2,087,564 Total $ 3,182,772 $ 3,259,492
Continuous Unrealized-Loss Position of Available-for-Sale Securities	The following tables disclose the Company’s investment securities that have been in a continuous unrealized-loss Less than 12 Months 12 Months or Longer Total June 30, 2019 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Obligations of states and political subdivisions $ — $ — $ 9,777 $ 61 $ 9,777 $ 61 Residential mortgage-backed securities 17,594 77 404,946 3,024 422,540 3,101 Commercial mortgage-backed securities — — 134,881 459 134,881 459 Total $ 17,594 $ 77 $ 549,604 $ 3,544 $ 567,198 $ 3,621 Less than 12 Months 12 Months or Longer Total June 30, 2018 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Obligations of U.S. government sponsored enterprises and agencies $ 303 $ 1 $ — $ — $ 303 $ 1 Obligations of states and political subdivisions 136,950 1,122 43,239 1,574 180,189 2,696 Corporate bonds and other 4,617 76 233 3 4,850 79 Residential mortgage-backed securities 1,073,327 21,838 227,155 8,880 1,300,482 30,718 Commercial mortgage-backed securities 379,201 7,477 83,285 1,436 462,486 8,913 Total $ 1,594,398 $ 30,514 $ 353,912 $ 11,893 $ 1,948,310 $ 42,407 Less than 12 Months 12 Months or Longer Total December 31, 2018 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized U.S. Treasury securities $ 9,962 $ 8 $ — $ — $ 9,962 $ 8 Obligations of U.S. government sponsored enterprises and agencies — — 301 — 301 — Obligations of state and political subdivisions 27,489 107 114,461 1,863 141,950 1,970 Corporate bonds and other 4,348 68 450 9 4,798 77 Residential mortgage-backed securities 119,584 483 922,289 21,128 1,041,873 21,611 Commercial mortgage-backed securities 1,994 5 343,015 5,731 345,009 5,736 Total $ 163,377 $ 671 $ 1,380,516 $ 28,731 $ 1,543,893 $ 29,402

Loans Held for Investment and_2

Loans Held for Investment and Allowance for Loan Losses (Tables)	6 Months Ended
	Jun. 30, 2019
Receivables [Abstract]
Loans Held-for-Investment by Class of Financing Receivables	Loans held-for-investment June 30, December 31, 2019 2018 2018 Commercial $ 813,887 $ 775,010 $ 844,953 Agricultural 97,535 92,583 96,677 Real estate 2,730,585 2,567,878 2,639,346 Consumer 398,945 396,009 372,660 Total loans held-for-investment $ 4,040,952 $ 3,831,480 $ 3,953,636
Non-Accrual Loans, Loans Still Accruing and Past Due 90 Days or More and Restructured Loans	The Company’s non-accrual June 30, December 31, 2019 2018 2018 Non-accrual $ 26,408 $ 26,685 $ 27,534 Loans still accruing and past due 90 days or more 300 200 1,008 Troubled debt restructured loans** 471 514 513 Total $ 27,179 $ 27,399 $ 29,055 * Includes $464,000, $2,813,000 and $827,000 of purchased credit impaired loans as of June 30, 2019 and 2018, and December 31, 2018, respectively. ** Troubled debt restructured loans of $3,906,000, $4,329,000 and $3,840,000, whose interest collection, after considering economic and business conditions and collection efforts, is doubtful are included in non-accrual
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, 2019 June 30, 2018 December 31, 2018 Recorded Investment Valuation Allowance Recorded Investment Valuation Allowance Recorded Investment Valuation Allowance $26,408 $ 3,866 $ 26,685 $ 4,823 $ 27,534 $ 4,069
Schedule of Non-Accrual Loans	Non-accrual June 30, December 31, 2019 2018 2018 Commercial $ 8,189 $ 7,580 $ 9,334 Agricultural 1,047 1,259 759 Real estate 16,787 16,715 16,714 Consumer 385 1,131 727 Total $ 26,408 $ 26,685 $ 27,534
Schedule of Impaired Loans and Related Allowance	The Company’s impaired loans and related allowance 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, 2019 Unpaid Contractual Principal Balance Recorded Investment With No Allowance* Recorded Investment With Allowance Total Recorded Investment Related Allowance Year- to-date Average Recorded Investment Three- Month Average Recorded Investment Commercial $ 9,340 $ 6,212 $ 1,977 $ 8,189 $ 1,022 $ 8,699 $ 8,562 Agricultural 1,108 434 613 1,047 119 1,090 1,071 Real Estate 24,262 5,034 11,753 16,787 2,515 18,054 17,105 Consumer 525 27 358 385 210 465 427 Total $ 35,235 $ 11,707 $ 14,701 $ 26,408 $ 3,866 $ 28,308 $ 27,165 * Includes $464,000 of purchased credit impaired loans. June 30, 2018 Unpaid Contractual Principal Balance Recorded Investment With No Allowance* Recorded Investment With Allowance Total Recorded Investment Related Allowance Year- to-date Average Recorded Investment Three- Average Recorded Investment Commercial $ 9,432 $ 3,264 $ 4,316 $ 7,580 $ 1,379 $ 8,485 $ 8,226 Agricultural 1,278 50 1,209 1,259 368 1,670 1,589 Real Estate 22,358 3,569 13,146 16,715 2,645 18,441 18,019 Consumer 1,344 169 962 1,131 431 1,240 1,192 Total $ 34,412 $ 7,052 $ 19,633 $ 26,685 $ 4,823 $ 29,836 $ 29,026 * Includes $2,813,000 of purchased credit impaired loans. December 31, 2018 Unpaid Contractual Principal Balance Recorded Investment With No Allowance* Recorded Investment With Allowance Total Recorded Investment Related Allowance 12 Month Average Recorded Investment Commercial $ 10,808 $ 6,728 $ 2,606 $ 9,334 $ 1,133 $ 7,986 Agricultural 799 213 546 759 170 842 Real Estate 24,072 6,699 10,015 16,714 2,409 16,042 Consumer 935 101 626 727 357 914 Total $ 36,614 $ 13,741 $ 13,793 $ 27,534 $ 4,069 $ 25,784 * Includes $827,000 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 June 30, 2019 Pass Special Substandard Doubtful Total Commercial $ 767,275 $ 31,124 $ 15,488 $ — $ 813,887 Agricultural 94,481 58 2,996 — 97,535 Real Estate 2,656,139 20,044 54,402 — 2,730,585 Consumer 397,017 264 1,664 — 398,945 Total $ 3,914,912 $ 51,490 $ 74,550 $ — $ 4,040,952 June 30, 2018 Pass Special Substandard Doubtful Total Commercial $ 749,387 $ 6,439 $ 19,184 $ — $ 775,010 Agricultural 87,768 1,568 3,247 — 92,583 Real Estate 2,487,399 26,182 54,297 — 2,567,878 Consumer 393,200 368 2,441 — 396,009 Total $ 3,717,754 $ 34,557 $ 79,169 $ — $ 3,831,480 December 31, 2018 Pass Special Substandard Doubtful Total Commercial $ 804,584 $ 23,392 $ 16,977 $ — $ 844,953 Agricultural 92,864 46 3,767 — 96,677 Real Estate 2,559,379 26,626 53,341 — 2,639,346 Consumer 370,510 315 1,835 — 372,660 Total $ 3,827,337 $ 50,379 $ 75,920 $ — $ 3,953,636
Schedule of Past Due Loans	The Company’s past due loans are as follows (in thousands): June 30, 2019 15-59 Past Due* 60-89 Past Due Greater Days Total Past Due Current Total Loans 90 Days Commercial $ 2,671 $ 352 $ 610 $ 3,633 $ 810,254 $ 813,887 $ 58 Agricultural 315 163 30 508 97,027 97,535 30 Real Estate 16,130 712 865 17,707 2,712,878 2,730,585 180 Consumer 821 99 40 960 397,985 398,945 32 Total $ 19,937 $ 1,326 $ 1,545 $ 22,808 $ 4,018,144 $ 4,040,952 $ 300 June 30, 2018 15-59 Past Due* 60-89 Past Due Greater Days Total Past Due Current Total Loans 90 Days Commercial $ 4,950 $ 1,085 $ 3,029 $ 9,064 $ 765,946 $ 775,010 $ 74 Agricultural 626 159 — 785 91,798 92,583 — Real Estate 13,441 474 532 14,447 2,553,431 2,567,878 70 Consumer 919 232 76 1,227 394,782 396,009 56 Total $ 19,936 $ 1,950 $ 3,637 $ 25,523 $ 3,805,957 $ 3,831,480 $ 200 December 31, 2018 15-59 Past Due* 60-89 Past Due Greater Days Total Past Due Total Current Total Loans Total 90 Past Due Still Commercial $ 3,546 $ 682 $ 677 $ 4,905 $ 840,048 $ 844,953 $ — Agricultural 791 19 26 836 95,841 96,677 — Real Estate 13,185 881 2,020 16,086 2,623,260 2,639,346 960 Consumer 782 263 54 1,099 371,561 372,660 48 Total $ 18,304 $ 1,845 $ 2,777 $ 22,926 $ 3,930,710 $ 3,953,636 $ 1,008 * 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 by portfolio segment (in thousands). There were no June 30, 2019 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,022 $ 119 $ 2,515 $ 210 $ 3,866 Loans collectively evaluated for impairment 12,877 1,241 28,284 5,552 47,954 Total $ 13,899 $ 1,360 $ 30,799 $ 5,762 $ 51,820 June 30, 2018 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,379 $ 368 $ 2,645 $ 431 $ 4,823 Loans collectively evaluated for impairment 7,839 1,034 30,598 5,657 45,128 Total $ 9,218 $ 1,402 $ 33,243 $ 6,088 $ 49,951 December 31, 2018 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,133 $ 170 $ 2,409 $ 357 $ 4,069 Loans collectively evaluated for impairment 10,815 1,276 29,933 5,109 47,133 Total $ 11,948 $ 1,446 $ 32,342 $ 5,466 $ 51,202
Changes in Allowance for Loan Losses	Changes in the allowance for loan losses are summarized as follows by portfolio segment (in thousands): Three months ended June 30, 2019 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 12,475 $ 1,430 $ 31,887 $ 5,793 $ 51,585 Provision for loan losses 1,418 61 (929 ) 50 600 Recoveries 423 5 60 209 697 Charge-offs (417 ) (136 ) (219 ) (290 ) (1,062 ) Ending balance $ 13,899 $ 1,360 $ 30,799 $ 5,762 $ 51,820 Three months ended June 30, 2018 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 9,277 $ 1,512 $ 32,539 $ 6,171 $ 49,499 Provision for loan losses 335 (115 ) 799 86 1,105 Recoveries 126 5 18 147 296 Charge-offs (520 ) — (113 ) (316 ) (949 ) Ending balance $ 9,218 $ 1,402 $ 33,243 $ 6,088 $ 49,951 Six months ended June 30, 2019 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 11,948 $ 1,446 $ 32,342 $ 5,466 $ 51,202 Provision for loan losses 1,612 42 (531 ) 442 1,565 Recoveries 1,073 7 149 349 1,578 Charge-offs (734 ) (135 ) (1,161 ) (495 ) (2,525 ) Ending balance $ 13,899 $ 1,360 $ 30,799 $ 5,762 $ 51,820 Six months ended June 30, 2018 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 10,865 $ 1,305 $ 29,896 $ 6,090 $ 48,156 Provision for loan losses (1,292 ) 88 3,233 386 2,415 Recoveries 284 9 260 247 800 Charge-offs (639 ) — (146 ) (635 ) (1,420 ) Ending balance $ 9,218 $ 1,402 $ 33,243 $ 6,088 $ 49,951
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 related to the balance in the allowance for loan losses on the basis of the Company’s impairment methodology is as follows (in thousands). Purchased credit impaired loans of $464,000, $2,813,000 and $827,000 at June 30, 2019 and 2018, and December 31, 2018, respectively, are included in loans individually evaluated for impairment. June 30, 2019 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 8,189 $ 1,047 $ 16,787 $ 385 $ 26,408 Loans collectively evaluated for impairment 805,698 96,488 2,713,798 398,560 4,014,544 Total $ 813,887 $ 97,535 $ 2,730,585 $ 398,945 $ 4,040,952 June 30, 2018 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 7,580 $ 1,259 $ 16,715 $ 1,131 $ 26,685 Loans collectively evaluated for impairment 767,430 91,324 2,551,163 394,878 3,804,795 Total $ 775,010 $ 92,583 $ 2,567,878 $ 396,009 $ 3,831,480 December 31, 2018 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 9,334 $ 759 $ 16,714 $ 727 $ 27,534 Loan collectively evaluated for impairment 835,619 95,918 2,622,632 371,933 3,926,102 Total $ 844,953 $ 96,677 $ 2,639,346 $ 372,660 $ 3,953,636
Schedule of Loans Modified and Considered Troubled Debt Restructurings	The Company’s loans that were modified and considered troubled debt restructurings are as follows (in thousands): Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 Number Pre- Post- Number Pre- Post- Commercial 2 $ 122 $ 122 3 $ 279 $ 279 Agricultural 2 253 253 10 619 619 Real Estate — — — 4 650 650 Consumer — — — — — — Total 4 $ 375 $ 375 17 $ 1,548 $ 1,548 Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Number Pre- Post- Number Pre- Post- Commercial 1 $ 279 $ 279 1 $ 279 $ 279 Agricultural — — — 1 4 4 Real Estate 2 162 162 4 525 525 Consumer 3 39 39 6 113 113 Total 6 $ 480 $ 480 12 $ 921 $ 921
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 (in thousands): Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 Adjusted Extended Combined Maturity Adjusted Extended Combined Maturity Commercial $ — $ 122 $ — $ — $ 279 $ — Agricultural — 253 — — 354 265 Real Estate — — — — 202 448 Consumer — — — — — — Total $ — $ 375 $ — $ — $ 835 $ 713 Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Adjusted Extended Combined Maturity Adjusted Extended Combined Maturity Commercial $ — $ — $ 279 — $ — $ 279 Agricultural — — — — — 4 Real Estate — 162 — — 162 363 Consumer — — 39 — — 113 Total $ — $ 162 $ 318 — $ 162 $ 759

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Outstanding Notional Balances and Fair Values of Outstanding Derivative Positions	The following table provides the outstanding notional balances and fair values of outstanding derivative positions (dollars in thousands): June 30, 2019: Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value IRLCs $ 89,655 $ 1,525 $ — Forward mortgage-backed securities trades 72,500 — 254 June 30, 2018: Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value IRLCs $ 61,520 $ 501 $ — Forward mortgage-backed securities trades 17,500 — 47 December 31, 2018: Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value IRLCs $ 37,088 $ 765 $ — Forward mortgage-backed securities trades 45,500 — 403

Borrowings (Tables)

Borrowings (Tables)	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Schedule of Borrowings	Borrowings consisted of the following (dollars in thousands): June 30, December 31, 2019 2018 2018 Securities sold under agreements with customers to repurchase $ 356,555 $ 389,010 $ 409,631 Federal funds purchased 5,450 7,925 4,075 Advances from Federal Home Loan Bank of Dallas — 60,000 55,000 Total $ 362,005 $ 456,935 $ 468,706

Fair Value Disclosures (Tables)

Fair Value Disclosures (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis	The following table summarizes the Company’s available-for-sale June 30, 2019 Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value Available-for-sale U.S. Treasury securities $ 10,020 $ — $ — $ 10,020 Obligations of states and political subdivisions — 1,157,214 — 1,157,214 Corporate bonds — 228 — 228 Residential mortgage-backed securities — 1,596,175 — 1,596,175 Commercial mortgage-backed securities — 491,389 — 491,389 Other securities 4,466 — — 4,466 Total $ 14,486 $ 3,245,006 $ — $ 3,259,492 Loans held-for-sale $ — $ 18,981 $ — $ 18,981 IRLCs $ — $ 1,525 $ — $ 1,525 Forward mortgage-backed securities trades $ — $ 254 $ — $ 254 June 30, 2018 Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value Available-for-sale U.S. Treasury securities $ 9,965 $ — $ — $ 9,965 Obligations of U. S. government sponsored enterprises and agencies — 303 — 303 Obligations of states and political subdivisions — 1,284,775 — 1,284,775 Corporate bonds — 451 — 451 Residential mortgage-backed securities — 1,435,257 — 1,435,257 Commercial mortgage-backed securities — 462,485 — 462,485 Other securities 4,331 — — 4,331 Total $ 14,296 $ 3,183,271 $ — $ 3,197,567 Loans held-for-sale $ $ 5,061 $ — $ 5,061 IRLCs $ $ 501 $ — $ 501 Forward mortgage-backed securities trades $ — $ 47 $ — $ 47 December 31, 2018 Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value Available-for-sale U.S. Treasury securities $ 9,962 $ — $ — $ 9,962 Obligations of U. S. government sponsored enterprises and agencies — 301 — 301 Obligations of states and political subdivisions — 1,257,871 — 1,257,871 Corporate bonds — 450 — 450 Residential mortgage-backed securities — 1,454,545 — 1,454,545 Commercial mortgage-backed securities — 431,300 — 431,300 Other securities 4,348 — — 4,348 Total $ 14,310 $ 3,144,467 $ — $ 3,158,777 Loans held-for-sale $ — $ 19,185 $ — $ 19,185 IRLCs $ — $ 765 $ — $ 765 Forward mortgage-backed securities trades $ — $ 403 $ — $ 403
Other Real Estate Owned	The following table presents other real estate owned that were re-measured Three Months Ended June 30, 2019 2018 Carrying value of other real estate owned prior to re-measurement $ — $ 526 Write-downs included in gain (loss) on sale of other real estate owned — (126 ) Fair value $ — $ 400 Six Months Ended June 30, 2019 2018 Carrying value of other real estate owned prior to re-measurement $ — $ 526 Write-downs included in gain (loss) on sale of other real estate owned — (126 ) Fair value $ — $ 400
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 were as follows (in thousands). June 30, December 31, 2019 2018 2018 Carrying Estimated Carrying Estimated Carrying Estimated Fair Value Cash and due from banks $ 178,345 $ 178,345 $ 178,217 $ 178,217 $ 207,835 $ 207,835 Level 1 Federal funds sold 700 700 8,450 8,450 — — Level 1 Interest-bearing deposits in banks 128,652 128,652 99,499 99,499 40,812 40,812 Level 1 Interest-bearing time deposits in banks 960 960 1,458 1,458 1,458 1,458 Level 2 Available-for-sale 3,259,492 3,259,492 3,197,567 3,197,567 3,158,777 3,158,777 Levels 1 and 2 Loans held for investment 3,989,132 4,026,543 3,781,529 3,807,267 3,902,434 3,947,391 Level 3 Loans held for sale 22,305 22,347 24,289 24,550 21,672 21,779 Level 2 Accrued interest receivable 36,954 36,954 36,513 36,513 36,765 36,765 Level 2 Deposits with stated maturities 433,511 433,811 483,230 484,230 442,161 441,727 Level 2 Deposits with no stated maturities 5,936,255 5,936,255 5,727,377 5,727,377 5,738,228 5,738,228 Level 1 Borrowings 362,005 362,005 456,935 456,935 468,706 468,706 Level 2 Accrued interest payable 694 694 223 223 408 408 Level 2 IRLCs 1,525 1,525 501 501 765 765 Level 2 Forward mortgage backed securities trades 254 254 47 47 403 403 Level 2

Acquisition (Tables)

Acquisition (Tables)	6 Months Ended
	Jun. 30, 2019
Schedule of Preliminary Estimated Fair Value Amounts Assigned to Major Asset and Liability Categories at Acquisition Date	The following table presents the amounts recorded on the consolidated balance sheet on the acquisition date (dollars in thousands): Fair value of consideration paid: Common stock issued (1,289,371 shares) $ 58,087 Fair value of identifiable assets acquired: Cash and cash equivalents 18,653 Securities available-for-sale 64,501 Loans 266,327 Identifiable intangible assets 3,167 Other assets 15,375 Total identifiable assets acquired 368,023 Fair value of liabilities assumed: Deposits 341,902 Other liabilities (373 ) Total liabilities assumed 341,529 Fair value of net identifiable assets acquired 26,494 Goodwill resulting from acquisition $ 31,593

Stock Split and Stock Repurch_2

Stock Split and Stock Repurchase - Additional Information (Detail) - shares	Apr. 23, 2019	Jun. 30, 2019	Jul. 25, 2017
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program expiration date		Sep. 30, 2020
Minimum number of shares that company is required to repurchase		0
Stock repurchased under authorization		0
Dividends Common Stock Percentage of Stock Dividend	100.00%
Stockholders' Equity Note, Stock Split	two-for-one stock split
Dividends Payable, Date of Record	May 15, 2019
Dividends Payable, Date to be Paid	Jun. 3, 2019
Maximum [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, number of shares authorized to be repurchased			2,000,000

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Weighted average common shares outstanding, basic	135,650,599	135,194,550	135,572,859	135,124,672
Weighted average common shares outstanding, diluted	136,218,235	135,848,336	136,195,811	135,735,930

Interest-bearing Time Deposit_3

Interest-bearing Time Deposits in Banks and Securities - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2019USD ($)Investment	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)Investment	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)
Interest Bearing Time Deposits In Banks And Securities [Line Items]
INTEREST-BEARING TIME DEPOSITS IN BANKS	$ 960,000	$ 1,458,000	$ 960,000	$ 1,458,000	$ 1,458,000
Interest-bearing time deposits, maturity period, years			1 month
Number of investment positions | Investment	109		109
Securities pledged as collateral	$ 2,137,620,000		$ 2,137,620,000
Sales of investment securities available-for-sale	65,821,000	57,680,000	66,052,000	149,125,000
Gross realized gains from security sales	689,000	287,000	693,000	1,529,000
Gross realized losses from security sales or calls	$ 13,000	$ 220,000	$ 17,000	$ 241,000
Maximum [Member]
Interest Bearing Time Deposits In Banks And Securities [Line Items]
Interest-bearing time deposits, maturity period, years			3 months
Obligations of State and Political Subdivisions [Member] | Texas [Member]
Interest Bearing Time Deposits In Banks And Securities [Line Items]
Percentage of securities guaranteed by Texas Permanent School Fund	33.55%		33.55%
Obligations of State and Political Subdivisions [Member] | Texas [Member] | Available-for-Sale Securities [Member] | Geographic Concentration Risk [Member]
Interest Bearing Time Deposits In Banks And Securities [Line Items]
Concentration risk, percentage			84.95%

Interest-bearing Time Deposit_4

Interest-bearing Time Deposits in Banks and Securities - Summary of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost Basis, Total	$ 3,182,772	$ 3,153,568	$ 3,208,412
Securities available-for-sale, Gross Unrealized Holding Gains	80,341	34,611	31,562
Securities available-for-sale, Gross Unrealized Holding Losses	(3,621)	(29,402)	(42,407)
Securities available-for-sale, Estimated Fair Value	3,259,492	3,158,777	3,197,567
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost Basis, Total	9,984	9,970	9,957
Securities available-for-sale, Gross Unrealized Holding Gains	36		8
Securities available-for-sale, Gross Unrealized Holding Losses		(8)
Securities available-for-sale, Estimated Fair Value	10,020	9,962	9,965
Obligations of U.S. Government Sponsored Enterprises and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost Basis, Total		301	304
Securities available-for-sale, Gross Unrealized Holding Losses			(1)
Securities available-for-sale, Estimated Fair Value		301	303
Obligations of State and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost Basis, Total	1,103,682	1,229,828	1,257,547
Securities available-for-sale, Gross Unrealized Holding Gains	53,593	30,013	29,924
Securities available-for-sale, Gross Unrealized Holding Losses	(61)	(1,970)	(2,696)
Securities available-for-sale, Estimated Fair Value	1,157,214	1,257,871	1,284,775
Corporate Bonds and Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost Basis, Total	4,643	4,875	4,861
Securities available-for-sale, Gross Unrealized Holding Gains	51
Securities available-for-sale, Gross Unrealized Holding Losses		(77)	(79)
Securities available-for-sale, Estimated Fair Value	4,694	4,798	4,782
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost Basis, Total	1,579,544	1,472,228	1,464,345
Securities available-for-sale, Gross Unrealized Holding Gains	19,732	3,928	1,630
Securities available-for-sale, Gross Unrealized Holding Losses	(3,101)	(21,611)	(30,718)
Securities available-for-sale, Estimated Fair Value	1,596,175	1,454,545	1,435,257
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost Basis, Total	484,919	436,366	471,398
Securities available-for-sale, Gross Unrealized Holding Gains	6,929	670	0
Securities available-for-sale, Gross Unrealized Holding Losses	(459)	(5,736)	(8,913)
Securities available-for-sale, Estimated Fair Value	$ 491,389	$ 431,300	$ 462,485

Interest-bearing Time Deposit_5

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, 2019	Dec. 31, 2018	Jun. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale, Amortized Cost Basis, Due within one year	$ 165,912
Available-for-Sale, Amortized Cost Basis, Due after one year through five years	483,916
Available-for-Sale, Amortized Cost Basis, Due after five years through ten years	466,755
Available-for-Sale, Amortized Cost Basis, Due after ten years	1,726
Available-for-Sale, Amortized Cost Basis, Mortgage-backed securities	2,064,463
Available-for-Sale, Amortized Cost Basis, Total	3,182,772	$ 3,153,568	$ 3,208,412
Available-for-Sale, Estimated Fair Value, Due within one year	167,217
Available-for-Sale, Estimated Fair Value, Due after one year through five years	506,941
Available-for-Sale, Estimated Fair Value, Due after five years through ten years	495,582
Available-for-Sale, Estimated Fair Value, Due after ten years	2,188
Available-for-Sale, Estimated Fair Value, Mortgage-backed securities	2,087,564
Securities available-for-sale, Estimated Fair Value, Total	$ 3,259,492	$ 3,158,777	$ 3,197,567

Interest-bearing Time Deposit_6

Interest-bearing Time Deposits in Banks and Securities - Continuous Unrealized-Loss Position of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Fair Value	$ 17,594	$ 163,377	$ 1,594,398
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	77	671	30,514
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value	549,604	1,380,516	353,912
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss	3,544	28,731	11,893
Available-for-sale securities, continuous unrealized loss position, Fair Value	567,198	1,543,893	1,948,310
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss	3,621	29,402	42,407
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			303
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss			1
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value		301
Available-for-sale securities, continuous unrealized loss position, Fair Value		301	303
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss			1
Obligations of State 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		27,489	136,950
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss		107	1,122
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value	9,777	114,461	43,239
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss	61	1,863	1,574
Available-for-sale securities, continuous unrealized loss position, Fair Value	9,777	141,950	180,189
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss	61	1,970	2,696
Corporate Bonds and Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Fair Value		4,348	4,617
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss		68	76
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value		450	233
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss		9	3
Available-for-sale securities, continuous unrealized loss position, Fair Value		4,798	4,850
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss		77	79
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	17,594	119,584	1,073,327
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	77	483	21,838
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value	404,946	922,289	227,155
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss	3,024	21,128	8,880
Available-for-sale securities, continuous unrealized loss position, Fair Value	422,540	1,041,873	1,300,482
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss	3,101	21,611	30,718
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		1,994	379,201
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss		5	7,477
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value	134,881	343,015	83,285
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss	459	5,731	1,436
Available-for-sale securities, continuous unrealized loss position, Fair Value	134,881	345,009	462,486
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss	$ 459	5,736	$ 8,913
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Fair Value		9,962
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss		8
Available-for-sale securities, continuous unrealized loss position, Fair Value		9,962
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss		$ 8

Loans Held for Investment and_3

Loans Held for Investment and Allowance for Loan Losses - Loans Held-for-Investment by Class of Financing Receivables (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Loans and Leases Receivable Disclosure [Line Items]
Total	$ 4,040,952	$ 3,953,636	$ 3,831,480
Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total	813,887	844,953	775,010
Agriculture [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total	97,535	96,677	92,583
Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total	2,730,585	2,639,346	2,567,878
Consumer [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total	$ 398,945	$ 372,660	$ 396,009

Loans Held for Investment and_4

Loans Held for Investment 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		Jul. 30, 2019	Jun. 30, 2019		Dec. 31, 2018		Jun. 30, 2018
Receivables [Abstract]
Non-accrual loans		$ 26,408	$ 26,408	[1]	$ 27,534	[1]	$ 26,685	[1]
Loans still accruing and past due 90 days or more			300		1,008		200
Troubled debt restructured loans	[2]		471		513		514
Total			$ 27,179		$ 29,055		$ 27,399
[1]	Includes $464,000, $2,813,000 and $827,000 of purchased credit impaired loans as of June 30, 2019 and 2018, and December 31, 2018, respectively.
[2]	Troubled debt restructured loans of $3,906,000, $4,329,000 and $3,840,000, whose interest collection, after considering economic and business conditions and collection efforts, is doubtful are included in non-accrual loans at June 30, 2019 and 2018, and December 31, 2018, respectively.

Loans Held for Investment and_5

Loans Held for Investment and Allowance for Loan Losses - Non-Accrual Loans, Loans Still Accruing and Past Due 90 Days or More and Restructured Loans (Parenthetical) (Detail) - USD ($)		Jul. 30, 2019	Jun. 30, 2019		Dec. 31, 2018		Jun. 30, 2018
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans		$ 26,408,000	$ 26,408,000	[1]	$ 27,534,000	[1]	$ 26,685,000	[1]
Troubled debt restructured loans	[2]		471,000		513,000		514,000
Doubtful [Member]
Loans and Leases Receivable Disclosure [Line Items]
Troubled debt restructured loans			3,906,000		3,840,000		4,329,000
Purchased Credit Impaired Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans			$ 464,000		$ 827,000		$ 2,813,000
[1]	Includes $464,000, $2,813,000 and $827,000 of purchased credit impaired loans as of June 30, 2019 and 2018, and December 31, 2018, respectively.
[2]	Troubled debt restructured loans of $3,906,000, $4,329,000 and $3,840,000, whose interest collection, after considering economic and business conditions and collection efforts, is doubtful are included in non-accrual loans at June 30, 2019 and 2018, and December 31, 2018, respectively.

Loans Held for Investment and_6

Loans Held for Investment and Allowance for Loan Losses - Recorded Investment in Impaired Loans and Related Valuation Allowance (Detail) - USD ($) $ in Thousands	Jul. 30, 2019	Jun. 30, 2019		Dec. 31, 2018		Jun. 30, 2018
Receivables [Abstract]
Recorded Investment	$ 26,408	$ 26,408	[1]	$ 27,534	[1]	$ 26,685	[1]
Valuation Allowance		$ 3,866		$ 4,069		$ 4,823
[1]	Includes $464,000, $2,813,000 and $827,000 of purchased credit impaired loans as of June 30, 2019 and 2018, and December 31, 2018, respectively.

Loans Held for Investment and_7

Loans Held for Investment and Allowance for Loan Losses - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Jun. 30, 2019		Dec. 31, 2018		Jul. 30, 2019	Mar. 31, 2019	Jun. 30, 2018		Mar. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual, past due 90 days or more and still accruing, restructured loans and foreclosed assets	$ 27,860,000		$ 29,632,000				$ 28,104,000
Non accrual loans	26,408,000	[1]	27,534,000	[1]	$ 26,408,000		26,685,000	[1]
Additional funds advanced in connection with impaired loans	0
Interest income recognized on impaired loans			948,000
Allowance for loan losses	51,820,000		51,202,000			$ 51,585,000	49,951,000		$ 49,499,000	$ 48,156,000
Loans individually evaluated for impairment	$ 26,408,000		27,534,000				26,685,000
Default for purposes of this disclosure is a troubled debt restructured loan	90 days
Commitments to lend additional funds to borrowers with loan that have been modified as TDRs	$ 0
Loans held by subsidiaries subject to blanket liens	2,563,225,000
Impaired Financing Receivable, Unpaid Principal Balance	35,235,000		36,614,000				34,412,000
Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non accrual loans	464,000		827,000				2,813,000
Allowance for loan losses	0		0				0
Loans individually evaluated for impairment	464,000		827,000				2,813,000
Impaired Financing Receivable, Unpaid Principal Balance	$ 750,000		$ 1,157,000				$ 3,918,000
[1]	Includes $464,000, $2,813,000 and $827,000 of purchased credit impaired loans as of June 30, 2019 and 2018, and December 31, 2018, respectively.

Loans Held for Investment and_8

Loans Held for Investment and Allowance for Loan Losses - Schedule of Non-Accrual Loans (Detail) - USD ($) $ in Thousands	Jul. 30, 2019	Jun. 30, 2019		Dec. 31, 2018		Jun. 30, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	$ 26,408	$ 26,408	[1]	$ 27,534	[1]	$ 26,685	[1]
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans		8,189		9,334		7,580
Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans		1,047		759		1,259
Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans		16,787		16,714		16,715
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans		$ 385		$ 727		$ 1,131
[1]	Includes $464,000, $2,813,000 and $827,000 of purchased credit impaired loans as of June 30, 2019 and 2018, and December 31, 2018, respectively.

Loans Held for Investment and_9

Loans Held for Investment 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, 2019		Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018		Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	$ 35,235		$ 34,412		$ 35,235		$ 34,412		$ 36,614
Recorded Investment With No Allowance	11,707	[1]	7,052	[2]	11,707	[1]	7,052	[2]	13,741	[3]
Recorded Investment With Allowance	14,701		19,633		14,701		19,633		13,793
Total Recorded Investment	26,408		26,685		26,408		26,685		27,534
Related Allowance	3,866		4,823		3,866		4,823		4,069
Average Recorded Investment	27,165		29,026		28,308		29,836		25,784
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	9,340		9,432		9,340		9,432		10,808
Recorded Investment With No Allowance	6,212	[1]	3,264	[2]	6,212	[1]	3,264	[2]	6,728	[3]
Recorded Investment With Allowance	1,977		4,316		1,977		4,316		2,606
Total Recorded Investment	8,189		7,580		8,189		7,580		9,334
Related Allowance	1,022		1,379		1,022		1,379		1,133
Average Recorded Investment	8,562		8,226		8,699		8,485		7,986
Agriculture [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	1,108		1,278		1,108		1,278		799
Recorded Investment With No Allowance	434	[1]	50	[2]	434	[1]	50	[2]	213	[3]
Recorded Investment With Allowance	613		1,209		613		1,209		546
Total Recorded Investment	1,047		1,259		1,047		1,259		759
Related Allowance	119		368		119		368		170
Average Recorded Investment	1,071		1,589		1,090		1,670		842
Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	24,262		22,358		24,262		22,358		24,072
Recorded Investment With No Allowance	5,034	[1]	3,569	[2]	5,034	[1]	3,569	[2]	6,699	[3]
Recorded Investment With Allowance	11,753		13,146		11,753		13,146		10,015
Total Recorded Investment	16,787		16,715		16,787		16,715		16,714
Related Allowance	2,515		2,645		2,515		2,645		2,409
Average Recorded Investment	17,105		18,019		18,054		18,441		16,042
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	525		1,344		525		1,344		935
Recorded Investment With No Allowance	27	[1]	169	[2]	27	[1]	169	[2]	101	[3]
Recorded Investment With Allowance	358		962		358		962		626
Total Recorded Investment	385		1,131		385		1,131		727
Related Allowance	210		431		210		431		357
Average Recorded Investment	$ 427		$ 1,192		$ 465		$ 1,240		$ 914
[1]	Includes $464,000 of purchased credit impaired loans.
[2]	Includes $2,813,000 of purchased credit impaired loans.
[3]	Includes $827,000 of purchased credit impaired loans.

Loans Held for Investment an_10

Loans Held for Investment and Allowance for Loan Losses - Schedule of Impaired Loans and Related Allowance (Parenthetical) (Detail) - USD ($) $ in Thousands	Jun. 30, 2019		Dec. 31, 2018		Jun. 30, 2018
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Allowance	$ 11,707	[1]	$ 13,741	[2]	$ 7,052	[3]
Purchased Credit Impaired Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Allowance	$ 464		$ 827		$ 2,813
[1]	Includes $464,000 of purchased credit impaired loans.
[2]	Includes $827,000 of purchased credit impaired loans.
[3]	Includes $2,813,000 of purchased credit impaired loans.

Loans Held for Investment an_11

Loans Held for Investment and Allowance for Loan Losses - Schedule of Internal Ratings of Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	$ 4,040,952	$ 3,953,636	$ 3,831,480
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	813,887	844,953	775,010
Agriculture [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	97,535	96,677	92,583
Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	2,730,585	2,639,346	2,567,878
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	398,945	372,660	396,009
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	3,914,912	3,827,337	3,717,754
Pass [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	767,275	804,584	749,387
Pass [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	94,481	92,864	87,768
Pass [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	2,656,139	2,559,379	2,487,399
Pass [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	397,017	370,510	393,200
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	51,490	50,379	34,557
Special Mention [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	31,124	23,392	6,439
Special Mention [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	58	46	1,568
Special Mention [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	20,044	26,626	26,182
Special Mention [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	264	315	368
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	74,550	75,920	79,169
Substandard [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	15,488	16,977	19,184
Substandard [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	2,996	3,767	3,247
Substandard [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	54,402	53,341	54,297
Substandard [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	$ 1,664	$ 1,835	$ 2,441

Loans Held for Investment an_12

Loans Held for Investment and Allowance for Loan Losses - Schedule of Past Due Loans (Detail) - USD ($) $ in Thousands		Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		$ 22,808	$ 22,926	$ 25,523
Total Current		4,018,144	3,930,710	3,805,957
Total Loans		4,040,952	3,953,636	3,831,480
Total 90 Days Past Due Still Accruing		300	1,008	200
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		3,633	4,905	9,064
Total Current		810,254	840,048	765,946
Total Loans		813,887	844,953	775,010
Total 90 Days Past Due Still Accruing		58		74
Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		508	836	785
Total Current		97,027	95,841	91,798
Total Loans		97,535	96,677	92,583
Total 90 Days Past Due Still Accruing		30
Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		17,707	16,086	14,447
Total Current		2,712,878	2,623,260	2,553,431
Total Loans		2,730,585	2,639,346	2,567,878
Total 90 Days Past Due Still Accruing		180	960	70
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		960	1,099	1,227
Total Current		397,985	371,561	394,782
Total Loans		398,945	372,660	396,009
Total 90 Days Past Due Still Accruing		32	48	56
15-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	19,937	18,304	19,936
15-59 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	2,671	3,546	4,950
15-59 Days Past Due [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	315	791	626
15-59 Days Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	16,130	13,185	13,441
15-59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	[1]	821	782	919
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,326	1,845	1,950
60-89 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		352	682	1,085
60-89 Days Past Due [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		163	19	159
60-89 Days Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		712	881	474
60-89 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		99	263	232
Greater than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,545	2,777	3,637
Greater than 90 Days [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		610	677	3,029
Greater than 90 Days [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		30	26
Greater than 90 Days [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		865	2,020	532
Greater than 90 Days [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		$ 40	$ 54	$ 76
[1]	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.

Loans Held for Investment an_13

Loans Held for Investment and Allowance for Loan Losses - Schedule of Allowance for Loan Losses by Portfolio Segment (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	$ 3,866		$ 4,069	$ 4,823
Loans collectively evaluated for impairment	47,954		47,133	45,128
Total allowance for loan losses	51,820	$ 51,585	51,202	49,951	$ 49,499	$ 48,156
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	1,022		1,133	1,379
Loans collectively evaluated for impairment	12,877		10,815	7,839
Total allowance for loan losses	13,899	12,475	11,948	9,218	9,277	10,865
Agriculture [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	119		170	368
Loans collectively evaluated for impairment	1,241		1,276	1,034
Total allowance for loan losses	1,360	1,430	1,446	1,402	1,512	1,305
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	2,515		2,409	2,645
Loans collectively evaluated for impairment	28,284		29,933	30,598
Total allowance for loan losses	30,799	31,887	32,342	33,243	32,539	29,896
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	210		357	431
Loans collectively evaluated for impairment	5,552		5,109	5,657
Total allowance for loan losses	$ 5,762	$ 5,793	$ 5,466	$ 6,088	$ 6,171	$ 6,090

Loans Held for Investment an_14

Loans Held for Investment and Allowance for Loan Losses - Changes in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 51,585	$ 49,499	$ 51,202	$ 48,156
Provision for loan losses	600	1,105	1,565	2,415
Recoveries	697	296	1,578	800
Charge-offs	(1,062)	(949)	(2,525)	(1,420)
Ending balance	51,820	49,951	51,820	49,951
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	12,475	9,277	11,948	10,865
Provision for loan losses	1,418	335	1,612	(1,292)
Recoveries	423	126	1,073	284
Charge-offs	(417)	(520)	(734)	(639)
Ending balance	13,899	9,218	13,899	9,218
Agriculture [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,430	1,512	1,446	1,305
Provision for loan losses	61	(115)	42	88
Recoveries	5	5	7	9
Charge-offs	(136)		(135)
Ending balance	1,360	1,402	1,360	1,402
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	31,887	32,539	32,342	29,896
Provision for loan losses	(929)	799	(531)	3,233
Recoveries	60	18	149	260
Charge-offs	(219)	(113)	(1,161)	(146)
Ending balance	30,799	33,243	30,799	33,243
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	5,793	6,171	5,466	6,090
Provision for loan losses	50	86	442	386
Recoveries	209	147	349	247
Charge-offs	(290)	(316)	(495)	(635)
Ending balance	$ 5,762	$ 6,088	$ 5,762	$ 6,088

Loans Held for Investment an_15

Loans Held for Investment 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, 2019	Dec. 31, 2018	Jun. 30, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	$ 26,408	$ 27,534	$ 26,685
Loan collectively evaluated for impairment	4,014,544	3,926,102	3,804,795
Total	4,040,952	3,953,636	3,831,480
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	8,189	9,334	7,580
Loan collectively evaluated for impairment	805,698	835,619	767,430
Total	813,887	844,953	775,010
Agriculture [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	1,047	759	1,259
Loan collectively evaluated for impairment	96,488	95,918	91,324
Total	97,535	96,677	92,583
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	16,787	16,714	16,715
Loan collectively evaluated for impairment	2,713,798	2,622,632	2,551,163
Total	2,730,585	2,639,346	2,567,878
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	385	727	1,131
Loan collectively evaluated for impairment	398,560	371,933	394,878
Total	$ 398,945	$ 372,660	$ 396,009

Loans Held for Investment an_16

Loans Held for Investment and Allowance for Loan Losses - Schedule of Loans Modified and Considered Troubled Debt Restructurings (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019USD ($)SecurityLoan	Jun. 30, 2018USD ($)SecurityLoan	Jun. 30, 2019USD ($)SecurityLoan	Jun. 30, 2018USD ($)SecurityLoan
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan	4	6	17	12
Pre-Modification Recorded Investment	$ 375	$ 480	$ 1,548	$ 921
Post-Modification Recorded Investment	$ 375	$ 480	$ 1,548	$ 921
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan	2	1	3	1
Pre-Modification Recorded Investment	$ 122	$ 279	$ 279	$ 279
Post-Modification Recorded Investment	$ 122	$ 279	$ 279	$ 279
Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan	2		10	1
Pre-Modification Recorded Investment	$ 253		$ 619	$ 4
Post-Modification Recorded Investment	$ 253		$ 619	$ 4
Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan		2	4	4
Pre-Modification Recorded Investment		$ 162	$ 650	$ 525
Post-Modification Recorded Investment		$ 162	$ 650	$ 525
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan		3		6
Pre-Modification Recorded Investment		$ 39		$ 113
Post-Modification Recorded Investment		$ 39		$ 113

Loans Held for Investment an_17

Loans Held for Investment 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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	$ 375	$ 480	$ 1,548	$ 921
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	122	279	279	279
Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	253		619	4
Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		162	650	525
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		39		113
Extended Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	375	162	835	162
Extended Maturity [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	122		279
Extended Maturity [Member] | Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	$ 253		354
Extended Maturity [Member] | Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		162	202	162
Combined Rate and Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		318	713	759
Combined Rate and Maturity [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		279		279
Combined Rate and Maturity [Member] | Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans			265	4
Combined Rate and Maturity [Member] | Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans			$ 448	363
Combined Rate and Maturity [Member] | Consumer [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		$ 39		$ 113

Loans Held for Sale - Additiona

Loans Held for Sale - Additional Information (Detail) - USD ($)	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group [Abstract]
Loans held for sale	$ 22,305,000	$ 21,672,000	$ 24,289,000
Loans held-for-sale at the lower of cost or fair value	$ 3,324,000	$ 2,487,000	$ 19,228,000

Derivative Financial Instrume_3

Derivative Financial Instruments - Summary of Outstanding Notional Balances and Fair Values of Outstanding Derivative Positions (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
IRLCs [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Outstanding Notional Balance	$ 89,655	$ 37,088	$ 61,520
Asset Derivative Fair Value	1,525	765	501
Forward Mortgage-Backed Securities Trades [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Outstanding Notional Balance	72,500	45,500	17,500
Liability Derivative Fair Value	$ 254	$ 403	$ 47

Borrowings - Schedule of Borrow

Borrowings - Schedule of Borrowings (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Debt Disclosure [Abstract]
Securities sold under agreements with customers to repurchase	$ 356,555	$ 409,631	$ 389,010
Federal funds purchased	5,450	4,075	7,925
Advances from Federal Home Loan Bank of Dallas		55,000	60,000
Total	$ 362,005	$ 468,706	$ 456,935

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Federal statutory tax rate			21.00%		35.00%
Income tax expense	$ 8,594	$ 7,217	$ 15,959	$ 13,462
Effective tax rates on pre-tax income	16.96%	16.09%	16.57%	15.72%

Stock Option Plan and Restric_2

Stock Option Plan and Restricted Stock Plan - Additional Information (Detail) - USD ($)	Jun. 26, 2019	Apr. 23, 2019	Oct. 23, 2018	Apr. 24, 2018	Oct. 24, 2017	Apr. 25, 2017	Oct. 25, 2016	Oct. 27, 2015	Jun. 26, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares vesting period			3 years
Risk-free interest rate									1.83%
Expected dividend yield									1.62%
Expected life									6 years 7 months 20 days
Expected volatility									26.69%
Weighted-average grant-date fair value of options granted									$ 7.31
Stock compensation expense										$ 313,000	$ 377,000	$ 625,000	$ 754,000
Granted, Shares									398,850					0
Granted the period exercise price									$ 29.70
Restricted Stock [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted		660,000		21,420		29,300
Restricted shares value		$ 21,714		$ 540,000		$ 600,000
Restricted Stock [Member] | Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense										135,000	140,000	270,000	290,000
Restricted Stock [Member] | Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares vesting period	3 years						3 years	3 years
Restricted shares granted	25,818		52,042		28,382		30,810	62,546
Restricted shares value	$ 766,000		$ 1,440,000		$ 655,000		$ 560,000	$ 1,060,000
Stock compensation expense										$ 210,000	$ 158,000	$ 415,000	$ 326,000

Pension Plan - Additional Infor

Pension Plan - Additional Information (Detail) - USD ($)	May 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Contributions to the plan					$ 0		$ 0
Defined benefit plan pension obligation retirement benefit percentage							53.00%
Defined benefit plan pension obligation, loss on settlement							$ 1,546,000
Net periodic benefit costs, total		$ 19,000		$ 56,000	$ 942,000	$ 111,000
Orange pension plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension merger expense			$ 900,000
Defined Benefit Plan, Benefit Obligation, Business Combination	$ 2,740,000
Defined Benefit Plan, Plan Assets, Business Combination	$ 1,829,000

Fair Value Disclosures - Additi

Fair Value Disclosures - Additional Information (Detail)	Jun. 30, 2019USD ($)		Dec. 31, 2018USD ($)		Jun. 30, 2018USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans carrying value, recorded investment with allowance	$ 14,701,000		$ 13,793,000		$ 19,633,000
Impaired loans valuation reserves	3,866,000		4,069,000		4,823,000
Impaired loans net fair value	10,835,000
Recorded Investment With No Allowance	11,707,000	[1]	13,741,000	[2]	7,052,000	[3]
Other real estate owned, total	635,000		$ 448,000		$ 642,000
Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans carrying value, recorded investment with allowance	14,701,000
Impaired loans valuation reserves	$ 3,866,000
Minimum [Member] | Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt discounts, percentage	5
Maximum [Member] | Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt discounts, percentage	25
[1]	Includes $464,000 of purchased credit impaired loans.
[2]	Includes $827,000 of purchased credit impaired loans.
[3]	Includes $2,813,000 of purchased credit impaired loans.

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, 2019	Dec. 31, 2018	Jun. 30, 2018
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	$ 3,259,492	$ 3,158,777	$ 3,197,567
Loans held-for-sale	22,305	21,672	24,289
U.S. Treasury Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	10,020	9,962	9,965
Obligations of U.S. Government Sponsored Enterprises and Agencies [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value		301	303
Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	1,157,214	1,257,871	1,284,775
Residential Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	1,596,175	1,454,545	1,435,257
Commercial Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	491,389	431,300	462,485
IRLCs [Member]
Available-for-sale investment securities:
Asset Derivative Fair Value	1,525	765	501
Forward Mortgage-Backed Securities Trades [Member]
Available-for-sale investment securities:
Forward mortgage-backed securities trades	254	403	47
Fair Value, Measurements, Recurring [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	3,259,492	3,158,777	3,197,567
Loans held-for-sale	18,981	19,185	5,061
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	10,020	9,962	9,965
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		301	303
Fair Value, Measurements, Recurring [Member] | Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	1,157,214	1,257,871	1,284,775
Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	1,596,175	1,454,545	1,435,257
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	491,389	431,300	462,485
Fair Value, Measurements, Recurring [Member] | IRLCs [Member]
Available-for-sale investment securities:
Asset Derivative Fair Value	1,525	765	501
Fair Value, Measurements, Recurring [Member] | Forward Mortgage-Backed Securities Trades [Member]
Available-for-sale investment securities:
Forward mortgage-backed securities trades	254	403	47
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	228	450	451
Fair Value, Measurements, Recurring [Member] | Other Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	4,466	4,348	4,331
Fair Value, Measurements, Recurring [Member] | Level 1 Inputs [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	14,486	14,310	14,296
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	10,020	9,962	9,965
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	4,466	4,348	4,331
Fair Value, Measurements, Recurring [Member] | Level 2 Inputs [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	3,245,006	3,144,467	3,183,271
Loans held-for-sale	18,981	19,185	5,061
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		301	303
Fair Value, Measurements, Recurring [Member] | Level 2 Inputs [Member] | Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	1,157,214	1,257,871	1,284,775
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	1,596,175	1,454,545	1,435,257
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	491,389	431,300	462,485
Fair Value, Measurements, Recurring [Member] | Level 2 Inputs [Member] | IRLCs [Member]
Available-for-sale investment securities:
Asset Derivative Fair Value	1,525	765	501
Fair Value, Measurements, Recurring [Member] | Level 2 Inputs [Member] | Forward Mortgage-Backed Securities Trades [Member]
Available-for-sale investment securities:
Forward mortgage-backed securities trades	254	403	47
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	$ 228	$ 450	$ 451

Fair Value Disclosures - Other

Fair Value Disclosures - Other Real Estate Owned (Detail) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018USD ($)	Jun. 30, 2018USD ($)
Fair Value Disclosures [Abstract]
Carrying value of other real estate owned prior to re-measurement	$ 526	$ 526
Write-downs included in gain (loss) on sale of other real estate owned	(126)	(126)
Other real estate owned, fair value	$ 400	$ 400

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, 2019	Dec. 31, 2018	Jun. 30, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 178,345	$ 207,835	$ 178,217
Federal funds sold	700		8,450
Interest-bearing deposits in banks	128,652	40,812	99,499
Interest-bearing time deposits in banks	960	1,458	1,458
Available-for-sale securities	3,259,492	3,158,777	3,197,567
Loans held for investment	3,989,132	3,902,434	3,781,529
Loans held for sale	22,305	21,672	24,289
Borrowings	362,005	468,706	456,935
IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	1,525	765	501
Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Forward mortgage-backed securities trades	254	403	47
Carrying Value [Member] | Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	178,345	207,835	178,217
Federal funds sold	700		8,450
Interest-bearing deposits in banks	128,652	40,812	99,499
Deposits with no stated maturities	5,936,255	5,738,228	5,727,377
Carrying Value [Member] | Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest-bearing time deposits in banks	960	1,458	1,458
Accrued interest receivable	36,954	36,765	36,513
Deposits with stated maturities	433,511	442,161	483,230
Borrowings	362,005	468,706	456,935
Accrued interest payable	694	408	223
Carrying Value [Member] | Level 2 Inputs [Member] | IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	1,525	765	501
Carrying Value [Member] | Level 2 Inputs [Member] | Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Forward mortgage-backed securities trades	254	403	47
Carrying Value [Member] | Levels 1 and 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	3,259,492	3,158,777	3,197,567
Carrying Value [Member] | Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for investment	3,989,132	3,902,434	3,781,529
Loans held for sale	22,305	21,672	24,289
Estimated Fair Value [Member] | Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	178,345	207,835	178,217
Federal funds sold	700		8,450
Interest-bearing deposits in banks	128,652	40,812	99,499
Deposits with no stated maturities	5,936,255	5,738,228	5,727,377
Estimated Fair Value [Member] | Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest-bearing time deposits in banks	960	1,458	1,458
Accrued interest receivable	36,954	36,765	36,513
Deposits with stated maturities	433,811	441,727	484,230
Borrowings	362,005	468,706	456,935
Accrued interest payable	694	408	223
Estimated Fair Value [Member] | Level 2 Inputs [Member] | IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	1,525	765	501
Estimated Fair Value [Member] | Level 2 Inputs [Member] | Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Forward mortgage-backed securities trades	254	403	47
Estimated Fair Value [Member] | Levels 1 and 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	3,259,492	3,158,777	3,197,567
Estimated Fair Value [Member] | Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for investment	4,026,543	3,947,391	3,807,267
Loans held for sale	$ 22,347	$ 21,779	$ 24,550

Recently Issued Authoritative_2

Recently Issued Authoritative Accounting Guidance - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Mar. 31, 2018	Jun. 30, 2019	Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Federal statutory tax rate		21.00%	35.00%
Accounting Standards Update 2018-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Reclassification of standard tax debit within accumulated other comprehensive income to retained earnings	$ 5,759,000

Acquisition - Additional Inform

Acquisition - Additional Information (Detail) - USD ($)	Jan. 02, 2018	Oct. 12, 2017	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Business Acquisition [Line Items]
Fair value of total loans			$ 266,327,000
Fair value of purchased credit impaired loans			26,408,000	$ 27,534,000	$ 26,685,000
Contractual amounts			35,235,000	36,614,000	34,412,000
Purchased Credit Impaired Loans [Member]
Business Acquisition [Line Items]
Contractual amounts			750,000	$ 1,157,000	$ 3,918,000
FBC Bancshares, Inc. and First Bank, N.A. [Member]
Business Acquisition [Line Items]
Payment for all outstanding shares of acquired entity by shares		1,289,371
Fair value of total loans			266,327,000
Total loans of contractual amounts			271,714,000
FBC Bancshares, Inc. and First Bank, N.A. [Member] | Purchased Credit Impaired Loans [Member]
Business Acquisition [Line Items]
Fair value of purchased credit impaired loans			3,013,000
Contractual amounts			$ 3,806,000
Commercial Bancshares, Inc [Member]
Business Acquisition [Line Items]
Business acquisition, agreement date			Oct. 12, 2017
Payment for all outstanding shares of acquired entity by shares	1,289,371
Business acquisition, special dividend	$ 22,075,000
Increase decrease in business acquisition, special dividend	$ 42,402,000

Acquisition - Schedule of Amoun

Acquisition - Schedule of Amounts Recorded on Consolidated Balance Sheet on Acquisition Date (Detail) $ in Thousands	Oct. 12, 2017USD ($)
FBC Bancshares, Inc. and First Bank, N.A. [Member]
Business Acquisition [Line Items]
Common stock issued (1,289,371 shares)	$ 58,087

Acquisition - Schedule of Amo_2

Acquisition - Schedule of Amounts Recorded on Consolidated Balance Sheet on Acquisition Date (Parenthetical) (Detail)	Oct. 12, 2017shares
FBC Bancshares, Inc. and First Bank, N.A. [Member]
Business Acquisition [Line Items]
Common stock issued shares	1,289,371

Acquisition - Schedule of Preli

Acquisition - Schedule of Preliminary Estimated Fair Value Amounts Assigned to Major Asset and Liability Categories at Acquisition Date (Detail) $ in Thousands	Jun. 30, 2019USD ($)
Business Acquisition [Line Items]
Loans	$ 266,327
FBC Bancshares, Inc. and First Bank, N.A. [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	18,653
Securities available-for-sale	64,501
Loans	266,327
Identifiable intangible assets	3,167
Other assets	15,375
Total identifiable assets acquired	368,023
Deposits	341,902
Other liabilities	(373)
Total liabilities assumed	341,529
Fair value of net identifiable assets acquired	26,494
Goodwill resulting from acquisition	$ 31,593