First Financial Bankshares (FFIN) 10-Q 28 Jul 20 2020 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2020	Jul. 28, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Document Period End Date	Jun. 30, 2020
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	Common Stock
Trading Symbol	FFIN
Security Exchange Name	NASDAQ
Entity Address, Postal Zip Code	79601
Entity Common Stock, Shares Outstanding		142,035,396

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
ASSETS
CASH AND DUE FROM BANKS	$ 188,373	$ 231,534	$ 178,345
FEDERAL FUNDS SOLD	0	3,150	700
INTEREST-BEARING DEMAND DEPOSITS IN BANKS	196,426	47,920	128,652
Total cash and cash equivalents	384,799	282,604	307,697
INTEREST-BEARING TIME DEPOSITS IN BANKS			960
SECURITIES AVAILABLE-FOR-SALE, at fair value	4,118,863	3,413,317	3,259,492
LOANS:
Held for investment	5,253,067	4,194,969	4,040,952
Less - allowance for loan losses	(68,947)	(52,499)	(51,820)
Net loans held for investment	5,184,120	4,142,470	3,989,132
Held for sale ($63,293, $18,981 and $23,076 at fair value at June 30, 2020 and 2019 and December 31, 2019, respectively)	66,370	28,228	22,305
Net loans	5,250,490	4,170,698	4,011,437
BANK PREMISES AND EQUIPMENT, net	138,933	131,022	134,322
GOODWILL AND INTANGIBLE ASSETS, net	319,365	173,667	174,151
OTHER ASSETS	127,367	90,919	91,234
Total assets	10,339,817	8,262,227	7,979,293
LIABILITIES AND SHAREHOLDERS' EQUITY
NONINTEREST-BEARING DEPOSITS	2,941,679	2,065,128	2,167,552
INTEREST-BEARING DEPOSITS	5,215,963	4,538,678	4,202,214
Total deposits	8,157,642	6,603,806	6,369,766
DIVIDENDS PAYABLE	18,462	16,306	16,294
BORROWINGS	449,224	381,356	362,005
OTHER LIABILITIES	132,040	33,562	66,480
Total liabilities	8,757,368	7,035,030	6,814,545
COMMITMENTS AND CONTINGENCIES
SHAREHOLDERS' EQUITY:
Common stock – ($0.01 par value, authorized 200,000,000 shares; 142,035,396, 135,809,224 and 135,891,755 shares issued at June 30, 2020 and 2019 and December 31, 2019, respectively)	1,420	1,359	1,358
Capital surplus	666,963	450,676	448,349
Retained earnings	762,830	707,656	655,794
Treasury stock (shares at cost: 932,018, 929,441 and 927,408 at June 30, 2020 and 2019 and December 31, 2019, respectively)	(8,697)	(8,222)	(7,823)
Deferred Compensation	8,697	8,222	7,823
Accumulated other comprehensive earnings, net of income taxes	151,236	67,506	59,247
Total shareholders' equity	1,582,449	1,227,197	1,164,748
Total liabilities and shareholders' equity	$ 10,339,817	$ 8,262,227	$ 7,979,293

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Statement of Financial Position [Abstract]
Loans held-for-sale, fair value	$ 63,293	$ 23,076	$ 18,981
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	142,035,396	135,891,755	135,809,224
Treasury stock, shares	932,018	927,408	929,441

Consolidated Statements of Earn

Consolidated Statements of Earnings - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
INTEREST INCOME:
Interest and fees on loans	$ 65,932	$ 55,740	$ 128,927	$ 108,971
Interest on investment securities:
Taxable	14,029	13,925	28,684	27,213
Exempt from federal income tax	12,149	9,244	21,844	19,007
Interest on federal funds sold and interest-bearing deposits in banks	87	667	842	1,286
Total interest income	92,197	79,576	180,297	156,477
INTEREST EXPENSE:
Interest on deposits	2,550	7,286	9,230	13,947
Other	412	675	929	1,401
Total interest expense	2,962	7,961	10,159	15,348
Net interest income	89,235	71,615	170,138	141,129
PROVISION FOR LOAN LOSSES	8,700	600	18,550	1,565
Net interest income after provision for loan losses	80,535	71,015	151,588	139,564
NONINTEREST INCOME:
Trust fees	6,961	7,027	14,398	14,006
Service charges on deposit accounts	4,318	5,374	10,233	10,550
ATM, interchange and credit card fees	8,049	7,352	15,449	14,192
Gain on sale and fees on mortgage loans	13,676	4,721	17,528	8,195
Net gain on sale of available-for-sale securities (includes $1,512 and $676 for the three months ended June 30, 2020 and 2019, respectively, and $3,574 and $676 for the six months ended June 30, 2020 and 2019, respectively, related to accumulated other comprehensive earnings reclassifications)	1,512	676	3,574	676
Net gain on sale of foreclosed assets	52	53	53	122
Net gain (loss) on sale of assets	(24)	6	92	6
Interest on loan recoveries	154	903	419	1,241
Other	2,221	1,864	3,905	3,425
Total noninterest income	36,919	27,976	65,651	52,413
NONINTEREST EXPENSE:
Salaries, commissions and employee benefits	30,814	27,394	60,456	53,918
Loss from partial settlement of pension plan	0	0	0	900
Net occupancy expense	3,101	2,779	6,128	5,542
Equipment expense	2,010	2,331	4,085	4,784
FDIC insurance premiums	463	538	508	1,076
ATM, interchange and credit card expenses	2,610	2,427	5,595	4,810
Professional and service fees	2,497	1,987	5,090	3,820
Printing, stationery and supplies	533	502	1,099	868
Operational and other losses	728	480	1,304	746
Software amortization and expense	2,010	1,783	4,034	3,380
Amortization of intangible assets	508	264	1,017	532
Other	8,047	7,819	19,324	15,297
Total noninterest expense	53,321	48,304	108,640	95,673
EARNINGS BEFORE INCOME TAXES	64,133	50,687	108,599	96,304
INCOME TAX EXPENSE (includes $318 and $142 for the three months ended June 30, 2020 and 2019, respectively, and $751 and $142 for the six months ended June 30, 2020 and 2019, respectively, related to income tax expense from reclassification items)	10,663	8,594	17,898	15,959
NET EARNINGS	$ 53,470	$ 42,093	$ 90,701	$ 80,345
EARNINGS PER SHARE, BASIC	$ 0.38	$ 0.31	$ 0.64	$ 0.59
EARNINGS PER SHARE, DILUTED	0.38	0.31	0.64	0.59
DIVIDENDS PER SHARE	$ 0.13	$ 0.12	$ 0.25	$ 0.23

Consolidated Statements of Ea_2

Consolidated Statements of Earnings (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Reclassifications adjustment for realized gains on investment securities included in net earnings (loss), before income tax	$ 1,512	$ 676	$ 3,574	$ 676
Income tax expense from reclassification items	$ 318	$ 142	$ 751	$ 142

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Earnings - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
NET EARNINGS	$ 53,470	$ 42,093	$ 90,701	$ 80,345
OTHER ITEMS OF COMPREHENSIVE EARNINGS:
Change in unrealized gain on investment securities available-for-sale, before income taxes	36,524	37,057	109,561	72,071
Reclassification adjustment for realized gains on investment securities included in net earnings, before income taxes	(1,512)	(676)	(3,574)	(676)
Total other items of comprehensive earnings	35,012	36,381	105,987	71,395
Income tax expense related to other items of comprehensive earnings	(7,352)	(7,640)	(22,257)	(14,993)
COMPREHENSIVE EARNINGS	$ 81,130	$ 70,834	$ 174,431	$ 136,747

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, 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)
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 spllit in the form of a 100% stock dividend (unaudited)		$ 678		(678)
Two-for-one stock spllit 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)					$ (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)
Beginning Balance at Dec. 31, 2019	$ 1,227,197	$ 1,359	450,676	707,656	$ (8,222)	8,222	67,506
Beginning Balance, Shares at Dec. 31, 2019		135,891,755
Stock issued in acquisition of Commercial Bancshares, Inc.	$ 220,273	$ 63	220,210
Stock issued in acquisition of Commercial Bancshares, Inc, Shares		6,275,574
Treasury Stock, Beginning Balance, Shares at Dec. 31, 2019	(927,408)				(927,408)
Net earnings (unaudited)	$ 90,701			90,701
Stock option exercises (unaudited)	2,481	$ 1	2,480
Stock option exercises, Shares		160,720
Restricted stock grant (unaudited)	913		913
Restricted stock grant (unaudited), Shares		32,149
Cash dividends declared	(35,527)			(35,527)
Change in unrealized gain in investment securities available-for-sale, net of related income taxes (unaudited)	83,730						83,730
Shares purchased (redeemed) in connection with directors' deferred compensation plan, net (unaudited)					$ (475)	475
Shares purchased (redeemed) in connection with directors' deferred compensation plan, net, Shares					(4,610)
Stock option expense (unaudited)	689		689
Shares repurchased under stock repurchase authorization (unaudited)	(8,008)	$ (3)	(8,005)
Shares repurchased under stock repurchase authorization, shares		(324,802)
Ending Balance at Jun. 30, 2020	$ 1,582,449	$ 1,420	666,963	762,830	$ (8,697)	8,697	151,236
Ending Balance, Shares at Jun. 30, 2020		142,035,396
Treasury Stock, Ending Balance, Shares at Jun. 30, 2020	(932,018)				(932,018)
Beginning Balance at Mar. 31, 2020	$ 1,526,362	$ 1,423	673,535	727,828	$ (8,437)	8,437	123,576
Beginning Balance, Shares at Mar. 31, 2020		142,314,930
Treasury Stock, Beginning Balance, Shares at Mar. 31, 2020					(928,417)
Net earnings (unaudited)	53,470	$ 0		53,470
Stock option exercises (unaudited)	289		289
Stock option exercises, Shares		16,532
Restricted stock grant (unaudited)	795		795
Restricted stock grant (unaudited), Shares		28,736
Cash dividends declared	(18,468)			(18,468)
Change in unrealized gain in investment securities available-for-sale, net of related income taxes (unaudited)	27,660						27,660
Shares purchased (redeemed) in connection with directors' deferred compensation plan, net (unaudited)					$ (260)	260
Shares purchased (redeemed) in connection with directors' deferred compensation plan, net, Shares					(3,601)
Stock option expense (unaudited)	349		349
Shares repurchased under stock repurchase authorization (unaudited)	(8,008)	$ (3)	(8,005)
Shares repurchased under stock repurchase authorization, shares		(324,802)
Ending Balance at Jun. 30, 2020	$ 1,582,449	$ 1,420	$ 666,963	$ 762,830	$ (8,697)	$ 8,697	$ 151,236
Ending Balance, Shares at Jun. 30, 2020		142,035,396
Treasury Stock, Ending Balance, Shares at Jun. 30, 2020	(932,018)				(932,018)

Consolidated Statements of Sh_2

Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Cash dividend per share	$ 0.13	$ 0.12	$ 0.25	$ 0.23
Common Stock Dividend Percentage				100.00%
Retained Earnings [Member]
Cash dividend per share	$ 0.13	$ 0.12	$ 0.25	$ 0.23

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net earnings	$ 90,701	$ 80,345
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	5,935	5,946
Provision for loan losses	18,550	1,565
Securities premium amortization (discount accretion), net	17,018	12,217
Gain on sale of assets, net	(3,719)	(804)
Deferred federal income tax (expense) benefit	(407)	2,206
Change in loans held-for-sale	(36,018)	(631)
Change in other assets	(16,452)	2,649
Change in other liabilities	38,274	5,219
Total adjustments	23,181	28,367
Net cash provided by operating activities	113,882	108,712
CASH FLOWS FROM INVESTING ACTIVITIES:
Cash received in acquisition of TB&T Bancshares, Inc.	61,028	0
Net decrease in interest-bearing time deposits in banks	0	498
Activity in available-for-sale securities:
Sales	252,958	66,052
Maturities	5,654,371	2,201,877
Purchases	(6,392,611)	(2,280,686)
Net increase in loans	(614,577)	(88,629)
Purchases of bank premises and equipment	(7,681)	(6,360)
Proceeds from sale of bank premises and equipment and other assets	1,144	187
Net cash used in investing activities	(1,045,368)	(107,061)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in noninterest-bearing deposits	638,726	51,445
Net increase in interest-bearing deposits	365,985	137,932
Net increase (decrease) in borrowings	67,868	(106,701)
Common stock transactions:
Proceeds from stock issuances	2,481	3,186
Dividends paid	(33,371)	(28,463)
Repurchase of stock	(8,008)	0
Net cash provided by financing activities	1,033,681	57,399
NET INCREASE IN CASH AND CASH EQUIVALENTS	102,195	59,050
CASH AND CASH EQUIVALENTS, beginning of period	282,604	248,647
CASH AND CASH EQUIVALENTS, end of period	384,799	307,697
SUPPLEMENTAL INFORMATION AND NONCASH TRANSACTIONS:
Interest paid	10,246	15,062
Federal income taxes paid	0	12,752
Transfer of loans and bank premises to other real estate	45	364
Investment securities purchased but not settled	33,554	29,355
Restricted stock grant to officers and directors	913	1,426
Stock issued in acquisition of TB&T Bancshares, Inc.	$ 220,273	$ 0

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES: Nature of Operations First Financial Bankshares, Inc. (a Texas corporation) (“Company”, “we” or “us”) is a financial holding company which owns all of the capital stock of one bank with 78 locations located in Texas as of June 30, 2020. The Company’s subsidiary bank is First Financial Bank, National Association, Abilene, Texas. The Company’s primary source of revenue is providing loans and banking services to consumers and commercial customers in the market area in which First Financial Bank, National Association, is located. In addition, the Company also owns First Financial Trust & Asset Management Company, National Association, First Financial Insurance Agency, Inc., and First Technology Services, Inc. A summary of significant accounting policies of the Company and its subsidiaries applied in the preparation of the accompanying consolidated financial statements follows. The accounting principles followed by the Company and the methods of applying them are in conformity with both United States generally accepted accounting principles (“GAAP”) and prevailing practices of the banking industry. The Company evaluated subsequent events for potential recognition through the date the consolidated financial statements were issued. Use of Estimates in Preparation of Financial Statements The preparation of financial statements in conformity with generally accepted accounting principles (U.S. GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The Company’s significant estimates include its allowance for loan losses and its valuation of securities. Consolidation The accompanying consolidated financial statements include the accounts of the Company and its subsidiaries, all of which are wholly-owned. All significant intercompany accounts and transactions have been eliminated. Stock Split and Increase in Authorized Shares On April 23, 2019, the Company’s Board of Directors declared a two-for-one stock split of the Company’s outstanding common shares in the form of a 100% stock dividend - Stock Repurchase On March 12, 2020, the Company’s Board of Directors authorized the repurchase of up to 4,000,000 common shares through September 30, 2021. Previously, the Board of Directors had authorized the repurchase of up to 2,000,000 common shares through September 30, 2020. The stock repurchase plan authorizes management to repurchase the stock at such time as repurchases are considered beneficial to The s hares repurch ased were reti red. Acquisition On January 1, 2020, the Company acquired 100% of the outstanding capital stock of TB&T Bancshares, Inc. through the merger of a wholly-owned subsidiary with and into TB&T Bancshares, Inc. Following such merger, TB&T Bancshares, Inc. and its wholly-owned subsidiary, The Bank & Trust of Bryan/College Station, Texas were merged into the Company and First Financial Bank, National Association, respectively. The results of operations of TB&T Bancshares, Inc. subsequent to the acquisition date, are included in the consolidated earnings of the Company. See note 11 for additional information. Status of New Accounting Standard for Accounting for Allowance for Credit Losses On January 1, 2020, ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments off-balance 2016-13 available-for-sale available-for-sale On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (CARES Act) was signed by the President of the United States that included an option for entities to delay the implementation of ASU 2016-13 2016-13 2016-13. Prior to the CARES Act being signed and our election to delay the implementation of CECL, we were completing our CECL implementation plan with our cross-functional working group, under the direction of our Chief Credit Officer along with our Chief Accounting Officer, Chief Lending Officer and Chief Financial Officer. The working group also included individuals from various functional areas including credit, risk management, accounting and information technology, among others. Our co nti nuing s Other Recently Issued and Effective Authoritative Accounting Guidance ASU 2016-02, “Leases.” 2016-02 right-of-use 2016-02 existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Company evaluated the provision of the new lease standard and, due to the small dollar amounts and number of lease agreements, all considered operating leases, the effect for the Company on January 1, 2019 was not significant. ASU 2017-08, “Receivables – Nonrefundable Fees and Other Costs Premium Amortization on Purchased Callable Debt Securities.” 2017-08 2017-08 2017-08 ASU 2017-04, “Intangibles – Goodwill and Other.” 2017-04 qualitative 2017-04 ASU 2018-13, “Fair Value Measurement (Topic 820). – Disclosure Framework - 2018-13 2018-13 2018-13 ASU 2019-12, “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes.” ASU 2019-12 simplifies the accounting for income taxes by eliminating certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. ASU 2019 -12 also simplifies aspects of the accounting for franchise taxes and enacted changes in tax laws or rates and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. ASU 2019-12 is effective for the Company for annual reporting periods beginning after December 15, 2020, and interim periods within. Adoption of ASU 2019-12 is not expected to have a material impact on the Company’s financial statements. Investment Securities 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 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 Held-for-Investment 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 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 were on non-accrual The provisions of the CARES Act included an election to not apply the guidance on accounting for troubled debt restructurings to loan modifications, such as extensions or deferrals, related to COVID-19 COVID-19 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 non-accretable Other Real Estate Other real estate owned is foreclosed property held pending disposition and is initially recorded at fair value, less estimated costs to sell. At foreclosure, if the fair value of the real estate, less estimated costs to sell, is less than the Company’s recorded investment in the related loan, a write-down is recognized through a charge to the allowance for loan losses. Any subsequent reduction in value is recognized by a charge to income. Operating and holding expenses of such properties, net of related income, and gains and losses on their disposition are included in net gain (loss) on sale of foreclosed assets as incurred. Bank Premises and Equipment Bank premises and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization are computed principally on a straight-line basis over the estimated useful lives of the related assets. Leasehold improvements are amortized over the life of the respective lease or the estimated useful lives of the improvements, whichever is shorter. Business Combinations, Goodwill and Other Intangible Assets The Company accounts for all business combinations under the purchase method of accounting. Tangible and intangible assets and liabilities of the acquired entity are recorded at fair value. Intangible assets with - , respectively. Securities Sold Under Agreements To Repurchase Securities sold under agreements to repurchase, which are classified as borrowings, generally mature within one to four days from the transaction date. Securities sold under agreements to repurchase are reflected at the amount of the cash received in connection with the transaction. The Company may be required to provide additional collateral based on the estimated fair value of the underlying securities. Segment Reporting The Company has determined that its banking regions meet the aggregation criteria of the current authoritative accounting guidance since each of its banking regions offer similar products and services, operate in a similar manner, have similar customers and report to the same regulatory authority, and therefore operate one line of business (community banking) located in a single geographic area (Texas). Statements of Cash Flows For purposes of reporting cash flows, cash and cash equivalents includes cash on hand, amounts due from banks, including interest-bearing deposits in banks with original maturity of 90 days or less, and federal funds sold. Accumulated Other Comprehensive Income (Loss) Unrealized net gains on the Company’s available-for-sale Income Taxes The Company’s provision for income taxes is based on income before income taxes adjusted for permanent differences between financial reporting and taxable income. Deferred tax assets and liabilities are determined using the liability (or balance sheet) method. Under this method, the net deferred tax asset or liability is determined based on the tax effects of the temporary differences between the book and tax bases of the various balance sheet assets and liabilities and gives current recognition to changes in tax rates and laws. Stock Based Compensation The Company grants stock options for a fixed number of shares to employees with an exercise price equal to the fair value of the shares at the grant date. The Company recorded stock option expense totaling $349,000 and $313,000 for the three-months ended June 30, 2020 and 2019, respectively. The Company recorded stock option expense totaling $689,000 and $625,000 for the six-months The Company also grants restricted stock for a fixed number of shares. The Company recorded expenses associated with its director and officer restricted stock grants totaling $482,000 and $345,000, for the three-months ended June 30, 2020 and 2019, respectively. The Company recorded expenses associated with its director and officer restricted stock grants totaling $932,000 and $685,000 for the six-months See note 8 for further information. Advertising Costs Advertising costs are expensed as incurred. Per Share Data Net earnings per share (“EPS”) are computed by dividing net earnings by the weighted average number of common shares outstanding during the period. The Company calculates dilutive EPS assuming all outstanding stock options to purchase common shares and unvested restricted stock shares have been exercised and/or vested at the beginning of the year (or the time of issuance, if later.) The dilutive effect of the outstanding options and restricted stock is reflected by application of the treasury stock method, whereby the proceeds from the exercised options and restricted stock are assumed to be used to purchase common shares at the average market price during the respective period six-months six- Net Weighted Per Share For the three-months ended June 30, 2020: Net earnings per share, basic $ 53,470 141,973,522 $ 0.38 Effect of stock options and stock grants — 480,561 — Net earnings per share, diluted $ 53,470 142,454,083 $ 0.38 Net Weighted Per Share For the six-months Net earnings per share, basic $ 90,701 142,045,779 $ 0.64 Effect of stock options and stock grants — 473,529 — Net earnings per share, diluted $ 90,701 142,519,308 $ 0.64 Net Weighted Per Share For the three-months ended June 30, 2019: Net earnings per share, basic $ 42,093 135,650,599 $ 0.31 Effect of stock options and stock grants — 567,636 — Net earnings per share, diluted $ 42,093 136,218,235 $ 0.31 Net Weighted Per Share For the six-months Net earnings per share, basic $ 80,345 135,572,859 $ 0.59 Effect of stock options and stock grants — 622,952 — Net earnings per share, diluted $ 80,345 136,195,811 $ 0.59

Securities

Securities	6 Months Ended
	Jun. 30, 2020
Cash and Cash Equivalents [Abstract]
Securities	Note 2 - A summary of the Company’s available-for-sale June 30, 2020 Amortized Gross Gross Estimated U.S. Treasury securities $ 10,083 $ 40 $ (1 ) $ 10,122 Obligations of states and political subdivisions 1,836,572 113,757 (50 ) 1,950,279 Corporate bonds and other 4,398 171 — 4,569 Residential mortgage-backed securities 1,517,139 54,652 (118 ) 1,571,673 Commercial mortgage-backed securities 559,062 23,159 (1 ) 582,220 Total securities available-for-sale $ 3,927,254 $ 191,779 $ (170 ) $ 4,118,863 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 December 31, 2019 Amortized Gross Gross Estimated U.S. Treasury securities $ 9,997 $ 22 $ — $ 10,019 Obligations of states and political subdivisions 1,231,619 57,764 (400 ) 1,288,983 Corporate bonds and other 4,643 65 — 4,708 Residential mortgage-backed securities 1,586,872 23,139 (1,148 ) 1,608,863 Commercial mortgage-backed securities 494,674 6,356 (286 ) 500,744 Total securities available-for-sale $ 3,327,805 $ 87,346 $ (1,834 ) $ 3,413,317 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, 2020 were computed by using scheduled amortization of balances and historical prepayment rates. At June 30, 2020 and 2019, and December 31, 2019, 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 $ 128,535 $ 129,521 Due after one year through five years 625,856 669,229 Due after five years through ten years 1,079,767 1,148,866 Due after ten years 16,895 17,354 Mortgage-backed securities 2,076,201 2,153,893 Total $ 3,927,254 $ 4,118,863 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, 2020 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized U.S. Treasury securities $ 5,055 $ 1 $ — $ — $ 5,055 $ 1 Obligations of states and political subdivisions 18,249 50 — — 18,249 50 Residential mortgage-backed securities 12,590 45 6,454 73 19,044 118 Commercial mortgage-backed securities 4,936 1 — — 4,936 1 Total $ 40,830 $ 97 $ 6,454 $ 73 $ 47,284 $ 170 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 December 31, 2019 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Loss Obligations of state and political subdivisions $ 65,787 $ 400 $ 326 $ — $ 66,113 $ 400 Residential mortgage-backed securities 100,004 306 103,983 842 203,987 1,148 Commercial mortgage-backed securities 74,560 178 35,178 108 109,738 286 Total $ 240,351 $ 884 $ 139,487 $ 950 $ 379,838 $ 1,834 The number of investments in an unrealized loss position totaled 14 at June 30, 2020. 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, 2020 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, 2020, 88.76% of our available-for-sale At June 30, 2020, $2,685,828,000 of the Company’s securities were pledged as collateral for public or trust fund deposits, repurchase agreements, a borrowing line with the Federal Reserve Bank of Dallas and for other purposes required or permitted by law. During the three months ended June 30, 2020 and 2019, sales of investment securities that were classified as available-for-sale the three-month period ended June 30, 2 During the six months ended June 30, 2020 and 2019, sales of investment securities classified as available-for-sale 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, 2020
Receivables [Abstract]
Loans Held for Investment and Allowance for Credit Losses	Note 3 – Loans Held-for-Investment and Allowance for Loan Losses Loans held-for-investment June 30, December 31, 2020 2019 2019 Commercial $ 1,509,454 $ 813,887 $ 856,326 Agricultural 97,448 97,535 103,640 Real estate 3,235,208 2,730,585 2,823,372 Consumer 410,957 398,945 411,631 Total loans held-for-investment $ 5,253,067 $ 4,040,952 $ 4,194,969 The Company’s non-accrual June 30, December 31, 202 0 2019 2019 Non-accrual $ 39,320 $ 26,408 $ 24,582 Loans still accruing and past due 90 days or more 92 300 153 Troubled debt restructured loans still accruing** 25 471 26 Total $ 39,437 $ 27,179 $ 24,761 * Includes $7,275,000, $464,000 and $251,000 of purchased credit impaired loans as of June 30, 2020 and 2019, and December 31, 2019, respectively. ** Troubled debt restructured loans of $4,673,000, $3,906,000 and $4,791,000, 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, 2020 June 30, 2019 December 31, 2019 Recorded Valuation Recorded Valuation Recorded Valuation $ 39,320 $ 3,046 $ 26,408 $ 3,866 $ 24,582 $ 3,228 The Company had $39,724,000, $27,860,000 and $25,770,000 in non-accrual, Non-accrual June 30, December 31, 2020 2019 2019 Commercial $ 4,618 $ 8,189 $ 3,093 Agricultural 1,056 1,047 1,376 Real estate 33,170 16,787 19,787 Consumer 476 385 326 Total $ 39,320 $ 26,408 $ 24,582 No significant additional funds are committed to be advanced in connection with impaired loans as of June 30, 2020. 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, 2020 Unpaid Principal Balance Recorded Recorded Total Related Year-to-date Average Three- Commercial $ 6,013 $ 739 $ 3,879 $ 4,618 $ 1,250 $ 24,270 $ 23,572 Agricultural 1,287 529 527 1,056 83 219 179 Real Estate 45,703 20,370 12,800 33,170 1,711 17,586 17,107 Consumer 585 — 476 476 2 606 552 Total $ 53,588 $ 21,638 $ 17,682 $ 39,320 $ 3,046 $ 42,681 $ 41,410 * Includes $7,275,000 of purchased credit impaired loans. June 30, 2019 Unpaid Recorded Recorded Total Related Year-to-date Average Three- 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. December 31, 2019 Unpaid Principal Balance Recorded Recorded Total Related Year-to - date Average Recorded Investment Commercial $ 4,511 $ 630 $ 2,463 $ 3,093 $ 1,042 $ 3,488 Agricultural 1,603 658 718 1,376 235 1,644 Real Estate 27,366 7,081 12,706 19,787 1,950 21,726 Consumer 469 — 326 326 1 449 Total $ 33,949 $ 8,369 $ 16,213 $ 24,582 $ 3,228 $ 27,307 * Includes $251,000 of purchased credit impaired loans. The Company recognized interest income on impaired loans prior to being recognized as impaired of approximately $750,000 during the year ended December 31, 2019. Such amounts for the three-month and six-month From a credit risk standpoint, the Company rates its loans in one of f ive 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, 2020 Pass Special Substandard Doubtful Total Commercial $ 1,465,595 $ 8,950 $ 34,909 $ — $ 1,509,454 Agricultural 90,824 4,790 1,834 — 97,448 Real Estate 3,086,894 49,493 98,821 — 3,235,208 Consumer 408,857 256 1,844 — 410,957 Total $ 5,052,170 $ 63,489 $ 137,408 $ — $ 5,253,067 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 December 31, 2019 Pass Special Substandard Doubtful Total Commercial $ 825,775 $ 20,971 $ 9,580 $ — $ 856,326 Agricultural 101,614 64 1,962 — 103,640 Real Estate 2,717,227 42,036 64,109 — 2,823,372 Consumer 409,698 300 1,633 — 411,631 Total $ 4,054,314 $ 63,371 $ 77,284 $ — $ 4,194,969 The Company’s past due loans are as follows (in thousands): June 30, 2020 15-59 Past 60-89 Past Greater Total Current Total 90 Days Commercial $ 4,563 $ 474 $ 129 $ 5,166 $ 1,504,288 $ 1,509,454 $ — Agricultural 1,080 15 — 1,095 96,353 97,448 — Real Estate 13,678 110 726 14,514 3,220,694 3,235,208 — Consumer 410 83 105 598 410,359 410,957 92 Total $ 19,731 $ 682 $ 960 $ 21,373 $ 5,231,694 $ 5,253,067 $ 92 June 30, 2019 15-59 Past 60-89 Past Greater Total Current Total 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 December 31, 2019 15-59 Past 60-89 Past Greater Total Current Total 90 Days Commercial $ 3,257 $ 557 $ 722 $ 4,536 $ 851,790 $ 856,326 $ 112 Agricultural 183 44 400 627 103,013 103,640 — Real Estate 12,890 288 195 13,373 2,809,999 2,823,372 — Consumer 572 151 45 768 410,863 411,631 41 Total $ 16,902 $ 1,040 $ 1,362 $ 19,304 $ 4,175,665 $ 4,194,969 $ 153 * 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 allowances for purchased credit impaired loans at June 30, 2020 and 2019, and December 31, 2019. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. June 30, 2020 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,250 $ 83 $ 1,711 $ 2 $ 3,046 Loans collectively evaluated for impairment 17,322 2,461 40,912 5,206 65,901 Total $ 18,572 $ 2,544 $ 42,623 $ 5,208 $ 68,947 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 December 31, 2019 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,042 $ 235 $ 1,950 $ 1 $ 3,228 Loans collectively evaluated for impairment 11,080 971 32,024 5,196 49,271 Total $ 12,122 $ 1,206 $ 33,974 $ 5,197 $ 52,499 Changes in the allowance for loan losses are summarized as follows by portfolio segment (in thousands): Three months ended June 30, 2020 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 11,773 $ 2,154 $ 41,256 $ 5,257 $ 60,440 Provision for loan losses 6,820 361 1,469 50 8,700 Recoveries 540 29 59 73 701 Charge-offs (561 ) — (161 ) (172 ) (894 ) Ending balance $ 18,572 $ 2,544 $ 42,623 $ 5,208 $ 68,947 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 Six months ended June 30, 2020 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 12,122 $ 1,206 $ 33,974 $ 5,197 $ 52,499 Provision for loan losses 7,615 1,310 9,390 235 18,550 Recoveries 690 30 135 164 1,019 Charge-offs (1,855 ) (2 ) (876 ) (388 ) (3,121 ) Ending balance $ 18,572 $ 2,544 $ 42,623 $ 5,208 $ 68,947 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 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 $7,275,000, $464,000 and $251,000 at June 30, 2020 and 2019, and December 31, 2019, respectively, are included in loans individually evaluated for impairment. June 30, 2020 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 4,618 $ 1,056 $ 33,170 $ 476 $ 39,320 Loans collectively evaluated for impairment 1,504,836 96,392 3,202,038 410,481 5,213,747 Total $ 1,509,454 $ 97,448 $ 3,235,208 $ 410,957 $ 5,253,067 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 December 31, 2019 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 3,093 $ 1,376 $ 19,787 $ 326 $ 24,582 Loans collectively evaluated for impairment 853,233 102,264 2,803,585 411,305 4,170,387 Total $ 856,326 $ 103,640 $ 2,823,372 $ 411,631 $ 4,194,969 The Company’s loans that were modified and considered troubled debt restructurings are as follows (in thousands): Three Months Ended June 30, 2020 Six Months Ended June 30, 2020 Number Pre- Post- Number Pre- Post- Commercial 4 $ 196 $ 196 9 $ 484 $ 484 Agricultural — — — 1 134 134 Real Estate 1 123 123 1 123 123 Consumer — — — 1 14 14 Total 5 $ 319 $ 319 12 $ 755 $ 755 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 The balances below provide information as to how the loans were modified as troubled debt restructured loans (in thousands): Three Months Ended June 30, 2020 Six Months Ended June 30, 2020 Adjusted Extended Combined Maturity Adjusted Extended Combined Maturity Commercial $ — $ — $ 196 $ — $ 260 $ 224 Agricultural — — — — 134 — Real Estate — — 123 — — 123 Consumer — — — — 14 — Total $ — $ — $ 319 $ — $ 408 $ 347 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 During the three - - restructured loan within the previous 12 months and for which there was a payment default. A default for purposes of this disclosure is a troubled debt restructured loan in which the borrower is 90 days past due or more or results in the foreclosure and repossession of the applicable collateral. As of June 30, 2020, the Company has no commitments to lend additional funds to loan customers whose terms have been modified in troubled debt restructurings. As discussed in note 1 to these financial statements, the CARES Act provided banks an option to elect to not account for certain loan modifications related to COVID-19 COVID-19 Beginning in mid-March of 2020, the Company began offering deferral and modification of principle and/or interest payments to selected borrowers on a case-by-case basis. At June 30, 2020, the Company had approximately 2, 2 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, 2020, $3,134,584,000 in loans held by our bank subsidiary were subject to blanket liens as security for this line of credit. At June 30, 2020, there was no balance outstanding under this line of credit.

Loans Held for Sale

Loans Held for Sale	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Loans Held for Sale	Note 4 - Loans Held for Sale Loans held for sale totaled $66,370,000, $22,305,000 and $28,228,000 at June 30, 2020 and 2019, and December 31, 2019, respectively. At June 30, 2020 and 2019, and December 31, 2019, $3,077,000, $3,324,000 and $5,152,000 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 5 for additional information). These loans, which are sold on a servicing released basis, are valued using a market approach by utilizing either: (i) the fair value of the securities backed by similar mortgage loans, adjusted for certain factors to approximate the fair value of a whole mortgage loan, including the value attributable to mortgage servicing and credit risk, (ii) current commitments to purchase loans or (iii) recent observable market trades for similar loans, adjusted for credit risk and other individual loan characteristics. As these prices are derived from market observable inputs, the Company classifies these valuations as Level 2 in the fair value disclosures (see note 10). Interest income on mortgage loans held for sale is recognized based on the contractual rates and reflected in interest income on loans in the consolidated statements of earnings. The Company has no continuing ownership in any residential mortgage loans sold. 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 six months, or if documentation is determined not to be in compliance with regulations. The Company’s historic losses as a result of these indemnities have been insignificant.

Derivative Financial Instrument

Derivative Financial Instruments	6 Months Ended
	Jun. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Note 5 - 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. The Company purchases 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 in the aggregate. 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, through earnings in the statement of earnings. 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) net of estimated costs to originate the loan. 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 10), 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 1 The following table provides the outstanding notional balances and fair values of outstanding derivative positions (dollars in thousands): June 30, 2020: Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value IRLCs $ 190,431 $ 5,037 $ — Forward mortgage-backed securities trades 201,500 — 1,099 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 December 31, 2019: Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value IRLCs $ 47,415 $ 886 $ — Forward mortgage-backed securities trades 78,500 — 152

Borrowings

Borrowings	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Borrowings	Note 6 – Borrowings Borrowings consisted of the following (dollars in thousands): June 30, December 31, 2020 2019 2019 Securities sold under agreements with customers to repurchase $ 444,249 $ 356,555 $ 375,106 Federal funds purchased 4,975 5,450 6,250 Advances from Federal Home Loan Bank of Dallas — — — Total $ 449,224 $ 362,005 $ 381,356 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, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Note 7 - Income tax expense was $10,663,000 for the second quarter of 2020 as compared to $8,594,000 for the same period in 2019. The Company’s effective tax rates on pretax income were 16.63% and 16.96% for the second quarters of 2020 and 2019, respectively. Income tax expense was $17,898,000 for the six months ended June 30, 2020 as compared to $15,959,000 for the same period in 2019. The Company’s effective tax rates on pretax income were 16.48% and 16.57% for the six months ended June 30,

Stock Option Plan and Restricte

Stock Option Plan and Restricted Stock Plan	6 Months Ended
	Jun. 30, 2020
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option Plan and Restricted Stock Plan	Note 8 - 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%. On January 28, 2020, the Company granted 11,250 incentive stock options with an exercise price of $34.55 per share. Other stock option disclosures for this grant have not been provided due to insignificance. The Company recorded stock option expense totaling $349,000 and $313,000 for the three-month periods ended June 30, 2020 and 2019, respectively. The Company recorded stock option expense totaling $689,000 and $625,000 for the six months ended June 30, 2020 and 2019, respectively. The additional disclosure requirements under authoritative accounting guidance have been omitted due to the amounts being insignificant. On April 24, 2018, upon re-election non-employee re-election non-employee non-employee shareholders’ meeting at which the director term expired. On April 28, 2020, upon the re-election non-employee On October 24, 2017, the Company granted 28,382 restricted shares with a total value of $655,000 to certain officers that are being expensed over the vesting period of one three-year three-year three-year an officer three-year

Pension Plan

Pension Plan	6 Months Ended
	Jun. 30, 2020
Retirement Benefits [Abstract]
Pension Plan	Note 9 - The Company had a defined benefit pension plan that was frozen effective January 1, 2004, whereby no new participants were added to the Plan and no additional years of service accrued to participants. The pension plan covered substantially all of the Company’s employees at the time. In December 2018, the Company determined it was in the best interest of its shareholders to work toward terminating its pension obligation. The Company annuitized approximately 53% of the pension benefit obligation at that time and recorded a loss on settlement totaling $1,546,000 for the year ended December 31, 2018. In 2019, the Company continued to take steps to completely settle and terminate its remaining pension obligation and recorded loss associated with the final termination of $2,673,000. The loss incurred included unrealized loss previously recorded in other comprehensive income and refunding to remaining participants for funding balance overages offset by a gain on hedging instrument entered into to minimize interest rate movement during the termination period. At December 31, 2019, all balances in the pension plan were zero and the Company’s obligation has been extinguished. For the three- and six-month

Fair Value Disclosures

Fair Value Disclosures	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Disclosures	Note 10 - Fair Value Disclosures The authoritative accounting guidance for fair value measurements defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. A fair value measurement assumes that the transaction to sell the asset or transfer the liability occurs in the principal market for the asset or liability or, in the absence of a principal market, the most advantageous market for the asset or liability. The price in the principal (or most advantageous) market used to measure the fair value of the asset or liability shall not be adjusted for transaction costs. An orderly transaction is a transaction that assumes exposure to the market for a period prior to the measurement date to allow for marketing activities that are usual and customary for transactions involving such assets and liabilities; it is not a forced transaction. Market participants are buyers and sellers in the principal market that are (i) independent, (ii) knowledgeable, (iii) able to transact, and (iv) willing to transact. The authoritative accounting guidance requires the use of valuation techniques that are consistent with the market approach, the income approach and/or the cost approach. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets and liabilities. The income approach uses valuation techniques to convert future amounts, such as cash flows or earnings, to a single present amount on a discounted basis. The cost approach is based on the amount that currently would be required to replace the service capacity of an asset (replacement costs). Valuation techniques should be consistently applied. Inputs to valuation techniques refer to the assumptions that market participants would use in pricing the asset or liability. Inputs may be observable, meaning those that reflect the assumptions market participants would use in pricing the asset or liability developed based on market data obtained from independent sources, or unobservable, meaning those that reflect the reporting entity’s own assumptions about the assumptions market participants would use in pricing the asset or liability developed based on the best information available in the circumstances. In that regard, the authoritative guidance establishes a fair value hierarchy for valuation inputs that gives the highest priority to quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. The fair value hierarchy is as follows: • Level 1 Inputs – Unadjusted quoted prices in active markets for identical assets or liabilities that the reporting entity has the ability to access at the measurement date. • Level 2 Inputs – Inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. These include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (for example, interest rates, volatilities, prepayment speeds, loss severities, credit risks and default rates) or inputs that are derived principally from or corroborated by observable market data by correlation or other means. • Level 3 Inputs – Significant unobservable inputs that reflect an entity’s own assumptions that market participants would use in pricing the assets or liabilities. A description of the valuation methodologies used for assets and liabilities measured at fair value, as well as the general classification of such instruments pursuant to the valuation hierarchy, is set forth below. In general, fair value is based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon internally developed models that primarily use, as inputs, observable market-based parameters. Valuation adjustments may be made to ensure that financial instruments are recorded at fair value. While management believes the Company’s valuation methodologies are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different estimate of fair value at the reporting date. Securities classified as available-for-sale See notes 4 and 5 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 - The following table summarizes the Company’s available-for-sale held-for-sale, June 30, 2020 Level 1 Level 2 Level 3 Total Fair Available-for-sale U.S. Treasury securities $ 10,122 $ — $ — $ 10,122 Obligations of states and political subdivisions — 1,950,279 — 1,950,279 Residential mortgage-backed securities — 1,571,673 — 1,571,673 Commercial mortgage-backed securities — 582,220 — 582,220 Other securities 4,569 — — 4,569 Total $ 14,691 $ 4,104,172 $ — $ 4,118,863 Loans held-for-sale $ — $ 63,293 $ — $ 63,293 IRLCs $ — $ 5,037 $ — $ 5,037 Forward mortgage-backed securities trades $ (1,099 ) $ — $ — $ (1,099 ) June 30, 2019 Level 1 Level 2 Level 3 Total Fair 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 ) December 31, 2019 Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value Available-for-sale U.S. Treasury securities $ 10,019 $ — $ — $ 10,019 Obligations of states and political subdivisions — 1,288,983 1,288,983 Corporate bonds — 230 — 230 Residential mortgage-backed securities — 1,608,863 — 1,608,863 Commercial mortgage-backed securities — 500,744 — 500,744 Other securities 4,478 — — 4,478 Total $ 14,497 $ 3,398,820 $ — $ 3,413,317 Loans held-for-sale $ — $ 23,076 $ — $ 23,076 IRLCs $ — $ 886 $ — $ 886 Forward mortgage-backed securities trades $ (152 ) $ — $ — $ (152 ) 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). 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, 2020, impaired loans with a carrying value of $17,682,000 were reduced by specific valuation reserves totaling $3,046,000 resulting in a net fair value of $14,636,000. Certain non-financial assets and non-financial liabilities measured at fair value on a non-recurring basis include other real estate owned, goodwill and other intangible assets and other non-financial long-lived assets. Non-financial assets measured at fair value on a non-recurring basis during the three and six- June 30 re-measured Re-evaluation re-measured six-months At June 30, 2020 and 2019, and December 31, 2019, other real estate owned totaled $202,000, $635,000 and $982,000, 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, 2020 2019 2019 Carrying Estimated Carrying Estimated Carrying Estimated Fair Value Cash and due from banks $ 188,373 $ 188,373 $ 178,345 $ 178,345 $ 231,534 $ 231,534 Level 1 Federal Funds Sold — — 700 700 3,150 3,150 Level 1 Interest-bearing demand deposits in banks 196,426 196,426 128,652 128,652 47,920 47,920 Level 1 Interest-bearing time deposits in banks — — 960 960 — — Level 2 Available-for-sale 4,118,863 4,118,863 3,259,492 3,259,492 3,413,317 3,413,317 Levels 1 and 2 Loans held for investment 5,184,120 5,174,126 3,989,132 4,026,543 4,142,470 4,209,826 Level 3 Loans held for sale 66,370 66,630 22,305 22,347 28,228 28,343 Level 2 Accrued interest receivable 45,801 45,801 36,954 36,954 36,894 36,894 Level 2 Deposits with stated maturities 466,122 468,819 433,511 433,811 420,013 421,397 Level 2 Deposits with no stated maturities 7,691,520 7,691,520 5,936,255 5,936,255 6,183,793 6,183,793 Level 1 Borrowings 449,224 449,224 362,005 362,005 381,356 381,356 Level 2 Accrued interest payable 541 541 694 694 628 628 Level 2 IRLCs 5,037 5,037 1,525 1,525 886 886 Level 2 Forward mortgage-backed securities trades 1,099 1,099 254 254 152 152 Level 1

Acquisition

Acquisition	6 Months Ended
	Jun. 30, 2020
Business Combinations [Abstract]
Acquisition	Note 11 – Acquisition On September 19, 2019, we entered into an agreement and plan of reorganization to acquire TB&T Bancshares, Inc. and its wholly-owned bank subsidiary, The Bank & Trust of Bryan/College Station, Texas. On January 1, 2020, the transaction was completed. Pursuant to the agreement, we issued 6,275,574 shares of the Company’s common stock in exchange for all of the outstanding shares of TB&T Bancshares, Inc. In addition, TBT Bancshares, Inc. made a $1,920,000 special dividend to its shareholders prior to closing of the transaction. At closing, a wholly - The following table presents the preliminary amounts recorded on the consolidated balance sheet on the acquisition date (dollars in thousands): Fair value of consideration paid: Common stock issued (6,275,574 shares) $ 220,273 Fair value of identifiable assets acquired: Cash and cash equivalents $ 61,028 Securities available-for-sale 93,967 Loans 447,702 Identifiable intangible assets 4,798 Other assets 25,377 Total identifiable assets acquired $ 632,872 Fair value of liabilities assumed: Deposits $ 549,125 Other liabilities 5,397 Total liabilities assumed $ 554,522 Fair value of net identifiable assets acquired 78,350 Goodwill resulting from acquisition $ 141,923 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 $447,702,000 at acquisition compared to contractual amounts of $455,181,000. The fair value of purchased credit impaired loans at acquisition was $7,517,000 compared to contractual amounts of $10,061,000. Additional purchased credit impaired loan disclosures were omitted due to immateriality. All other acquired loans were considered performing loans.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations First Financial Bankshares, Inc. (a Texas corporation) (“Company”, “we” or “us”) is a financial holding company which owns all of the capital stock of one bank with 78 locations located in Texas as of June 30, 2020. The Company’s subsidiary bank is First Financial Bank, National Association, Abilene, Texas. The Company’s primary source of revenue is providing loans and banking services to consumers and commercial customers in the market area in which First Financial Bank, National Association, is located. In addition, the Company also owns First Financial Trust & Asset Management Company, National Association, First Financial Insurance Agency, Inc., and First Technology Services, Inc. A summary of significant accounting policies of the Company and its subsidiaries applied in the preparation of the accompanying consolidated financial statements follows. The accounting principles followed by the Company and the methods of applying them are in conformity with both United States generally accepted accounting principles (“GAAP”) and prevailing practices of the banking industry. The Company evaluated subsequent events for potential recognition through the date the consolidated financial statements were issued.
Use of Estimates in Preparation of Financial Statements	Use of Estimates in Preparation of Financial Statements The preparation of financial statements in conformity with generally accepted accounting principles (U.S. GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The Company’s significant estimates include its allowance for loan losses and its valuation of securities.
Consolidation	Consolidation The accompanying consolidated financial statements include the accounts of the Company and its subsidiaries, all of which are wholly-owned. All significant intercompany accounts and transactions have been eliminated.
Stock Split and Increase in Authorized Shares	Stock Split and Increase in Authorized Shares On April 23, 2019, the Company’s Board of Directors declared a two-for-one stock split of the Company’s outstanding common shares in the form of a 100% stock dividend -
Stock Repurchase	Stock Repurchase On March 12, 2020, the Company’s Board of Directors authorized the repurchase of up to 4,000,000 common shares through September 30, 2021. Previously, the Board of Directors had authorized the repurchase of up to 2,000,000 common shares through September 30, 2020. The stock repurchase plan authorizes management to repurchase the stock at such time as repurchases are considered beneficial to The s hares repurch ased were reti red.
Acquisition	Acquisition On January 1, 2020, the Company acquired 100% of the outstanding capital stock of TB&T Bancshares, Inc. through the merger of a wholly-owned subsidiary with and into TB&T Bancshares, Inc. Following such merger, TB&T Bancshares, Inc. and its wholly-owned subsidiary, The Bank & Trust of Bryan/College Station, Texas were merged into the Company and First Financial Bank, National Association, respectively. The results of operations of TB&T Bancshares, Inc. subsequent to the acquisition date, are included in the consolidated earnings of the Company. See note 11 for additional information.
Status of New Accounting Standard for Accounting for Allowance for Credit Losses	Status of New Accounting Standard for Accounting for Allowance for Credit Losses On January 1, 2020, ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments off-balance 2016-13 available-for-sale available-for-sale On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (CARES Act) was signed by the President of the United States that included an option for entities to delay the implementation of ASU 2016-13 2016-13 2016-13. Prior to the CARES Act being signed and our election to delay the implementation of CECL, we were completing our CECL implementation plan with our cross-functional working group, under the direction of our Chief Credit Officer along with our Chief Accounting Officer, Chief Lending Officer and Chief Financial Officer. The working group also included individuals from various functional areas including credit, risk management, accounting and information technology, among others. Our co nti nuing s
Other Recently Issued and Effective Authoritative Accounting Guidance	Other Recently Issued and Effective Authoritative Accounting Guidance ASU 2016-02, “Leases.” 2016-02 right-of-use 2016-02 existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Company evaluated the provision of the new lease standard and, due to the small dollar amounts and number of lease agreements, all considered operating leases, the effect for the Company on January 1, 2019 was not significant. ASU 2017-08, “Receivables – Nonrefundable Fees and Other Costs Premium Amortization on Purchased Callable Debt Securities.” 2017-08 2017-08 2017-08 ASU 2017-04, “Intangibles – Goodwill and Other.” 2017-04 qualitative 2017-04 ASU 2018-13, “Fair Value Measurement (Topic 820). – Disclosure Framework - 2018-13 2018-13 2018-13 ASU 2019-12, “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes.” ASU 2019-12 simplifies the accounting for income taxes by eliminating certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. ASU 2019 -12 also simplifies aspects of the accounting for franchise taxes and enacted changes in tax laws or rates and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. ASU 2019-12 is effective for the Company for annual reporting periods beginning after December 15, 2020, and interim periods within. Adoption of ASU 2019-12 is not expected to have a material impact on the Company’s financial statements.
Investment Securities	Investment Securities 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 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 Held-for-Investment and Allowance for Loan Losses	Loans Held-for-Investment 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 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 were on non-accrual The provisions of the CARES Act included an election to not apply the guidance on accounting for troubled debt restructurings to loan modifications, such as extensions or deferrals, related to COVID-19 COVID-19 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 non-accretable
Other Real Estate	Other Real Estate Other real estate owned is foreclosed property held pending disposition and is initially recorded at fair value, less estimated costs to sell. At foreclosure, if the fair value of the real estate, less estimated costs to sell, is less than the Company’s recorded investment in the related loan, a write-down is recognized through a charge to the allowance for loan losses. Any subsequent reduction in value is recognized by a charge to income. Operating and holding expenses of such properties, net of related income, and gains and losses on their disposition are included in net gain (loss) on sale of foreclosed assets as incurred.
Bank Premises and Equipment	Bank Premises and Equipment Bank premises and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization are computed principally on a straight-line basis over the estimated useful lives of the related assets. Leasehold improvements are amortized over the life of the respective lease or the estimated useful lives of the improvements, whichever is shorter.
Business Combinations, Goodwill and Other Intangible Assets	Business Combinations, Goodwill and Other Intangible Assets The Company accounts for all business combinations under the purchase method of accounting. Tangible and intangible assets and liabilities of the acquired entity are recorded at fair value. Intangible assets with - , respectively.
Securities Sold Under Agreements To Repurchase	Securities Sold Under Agreements To Repurchase Securities sold under agreements to repurchase, which are classified as borrowings, generally mature within one to four days from the transaction date. Securities sold under agreements to repurchase are reflected at the amount of the cash received in connection with the transaction. The Company may be required to provide additional collateral based on the estimated fair value of the underlying securities.
Segment Reporting	Segment Reporting The Company has determined that its banking regions meet the aggregation criteria of the current authoritative accounting guidance since each of its banking regions offer similar products and services, operate in a similar manner, have similar customers and report to the same regulatory authority, and therefore operate one line of business (community banking) located in a single geographic area (Texas).
Statements of Cash Flows	Statements of Cash Flows For purposes of reporting cash flows, cash and cash equivalents includes cash on hand, amounts due from banks, including interest-bearing deposits in banks with original maturity of 90 days or less, and federal funds sold.
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Unrealized net gains on the Company’s available-for-sale
Income Taxes	Income Taxes The Company’s provision for income taxes is based on income before income taxes adjusted for permanent differences between financial reporting and taxable income. Deferred tax assets and liabilities are determined using the liability (or balance sheet) method. Under this method, the net deferred tax asset or liability is determined based on the tax effects of the temporary differences between the book and tax bases of the various balance sheet assets and liabilities and gives current recognition to changes in tax rates and laws.
Stock Based Compensation	Stock Based Compensation The Company grants stock options for a fixed number of shares to employees with an exercise price equal to the fair value of the shares at the grant date. The Company recorded stock option expense totaling $349,000 and $313,000 for the three-months ended June 30, 2020 and 2019, respectively. The Company recorded stock option expense totaling $689,000 and $625,000 for the six-months The Company also grants restricted stock for a fixed number of shares. The Company recorded expenses associated with its director and officer restricted stock grants totaling $482,000 and $345,000, for the three-months ended June 30, 2020 and 2019, respectively. The Company recorded expenses associated with its director and officer restricted stock grants totaling $932,000 and $685,000 for the six-months See note 8 for further information.
Advertising Costs	Advertising Costs Advertising costs are expensed as incurred.
Per Share Data	Per Share Data Net earnings per share (“EPS”) are computed by dividing net earnings by the weighted average number of common shares outstanding during the period. The Company calculates dilutive EPS assuming all outstanding stock options to purchase common shares and unvested restricted stock shares have been exercised and/or vested at the beginning of the year (or the time of issuance, if later.) The dilutive effect of the outstanding options and restricted stock is reflected by application of the treasury stock method, whereby the proceeds from the exercised options and restricted stock are assumed to be used to purchase common shares at the average market price during the respective period six-months six- Net Weighted Per Share For the three-months ended June 30, 2020: Net earnings per share, basic $ 53,470 141,973,522 $ 0.38 Effect of stock options and stock grants — 480,561 — Net earnings per share, diluted $ 53,470 142,454,083 $ 0.38 Net Weighted Per Share For the six-months Net earnings per share, basic $ 90,701 142,045,779 $ 0.64 Effect of stock options and stock grants — 473,529 — Net earnings per share, diluted $ 90,701 142,519,308 $ 0.64 Net Weighted Per Share For the three-months ended June 30, 2019: Net earnings per share, basic $ 42,093 135,650,599 $ 0.31 Effect of stock options and stock grants — 567,636 — Net earnings per share, diluted $ 42,093 136,218,235 $ 0.31 Net Weighted Per Share For the six-months Net earnings per share, basic $ 80,345 135,572,859 $ 0.59 Effect of stock options and stock grants — 622,952 — Net earnings per share, diluted $ 80,345 136,195,811 $ 0.59

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Computation of Basic EPS to Dilutive EPS	The following table reconciles the computation of basic EPS to dilutive EPS: Net Weighted Per Share For the three-months ended June 30, 2020: Net earnings per share, basic $ 53,470 141,973,522 $ 0.38 Effect of stock options and stock grants — 480,561 — Net earnings per share, diluted $ 53,470 142,454,083 $ 0.38 Net Weighted Per Share For the six-months Net earnings per share, basic $ 90,701 142,045,779 $ 0.64 Effect of stock options and stock grants — 473,529 — Net earnings per share, diluted $ 90,701 142,519,308 $ 0.64 Net Weighted Per Share For the three-months ended June 30, 2019: Net earnings per share, basic $ 42,093 135,650,599 $ 0.31 Effect of stock options and stock grants — 567,636 — Net earnings per share, diluted $ 42,093 136,218,235 $ 0.31 Net Weighted Per Share For the six-months Net earnings per share, basic $ 80,345 135,572,859 $ 0.59 Effect of stock options and stock grants — 622,952 — Net earnings per share, diluted $ 80,345 136,195,811 $ 0.59

Securities (Tables)

Securities (Tables)	6 Months Ended
	Jun. 30, 2020
Cash and Cash Equivalents [Abstract]
Summary of Available-for-Sale Securities	A summary of the Company’s available-for-sale June 30, 2020 Amortized Gross Gross Estimated U.S. Treasury securities $ 10,083 $ 40 $ (1 ) $ 10,122 Obligations of states and political subdivisions 1,836,572 113,757 (50 ) 1,950,279 Corporate bonds and other 4,398 171 — 4,569 Residential mortgage-backed securities 1,517,139 54,652 (118 ) 1,571,673 Commercial mortgage-backed securities 559,062 23,159 (1 ) 582,220 Total securities available-for-sale $ 3,927,254 $ 191,779 $ (170 ) $ 4,118,863 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 December 31, 2019 Amortized Gross Gross Estimated U.S. Treasury securities $ 9,997 $ 22 $ — $ 10,019 Obligations of states and political subdivisions 1,231,619 57,764 (400 ) 1,288,983 Corporate bonds and other 4,643 65 — 4,708 Residential mortgage-backed securities 1,586,872 23,139 (1,148 ) 1,608,863 Commercial mortgage-backed securities 494,674 6,356 (286 ) 500,744 Total securities available-for-sale $ 3,327,805 $ 87,346 $ (1,834 ) $ 3,413,317
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 $ 128,535 $ 129,521 Due after one year through five years 625,856 669,229 Due after five years through ten years 1,079,767 1,148,866 Due after ten years 16,895 17,354 Mortgage-backed securities 2,076,201 2,153,893 Total $ 3,927,254 $ 4,118,863
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, 2020 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized U.S. Treasury securities $ 5,055 $ 1 $ — $ — $ 5,055 $ 1 Obligations of states and political subdivisions 18,249 50 — — 18,249 50 Residential mortgage-backed securities 12,590 45 6,454 73 19,044 118 Commercial mortgage-backed securities 4,936 1 — — 4,936 1 Total $ 40,830 $ 97 $ 6,454 $ 73 $ 47,284 $ 170 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 December 31, 2019 Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Loss Obligations of state and political subdivisions $ 65,787 $ 400 $ 326 $ — $ 66,113 $ 400 Residential mortgage-backed securities 100,004 306 103,983 842 203,987 1,148 Commercial mortgage-backed securities 74,560 178 35,178 108 109,738 286 Total $ 240,351 $ 884 $ 139,487 $ 950 $ 379,838 $ 1,834

Loans Held for Investment and_2

Loans Held for Investment and Allowance for Loan Losses (Tables)	6 Months Ended
	Jun. 30, 2020
Receivables [Abstract]
Loans Held-for-Investment by Class of Financing Receivables	Loans held-for-investment June 30, December 31, 2020 2019 2019 Commercial $ 1,509,454 $ 813,887 $ 856,326 Agricultural 97,448 97,535 103,640 Real estate 3,235,208 2,730,585 2,823,372 Consumer 410,957 398,945 411,631 Total loans held-for-investment $ 5,253,067 $ 4,040,952 $ 4,194,969
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, 202 0 2019 2019 Non-accrual $ 39,320 $ 26,408 $ 24,582 Loans still accruing and past due 90 days or more 92 300 153 Troubled debt restructured loans still accruing** 25 471 26 Total $ 39,437 $ 27,179 $ 24,761 * Includes $7,275,000, $464,000 and $251,000 of purchased credit impaired loans as of June 30, 2020 and 2019, and December 31, 2019, respectively. ** Troubled debt restructured loans of $4,673,000, $3,906,000 and $4,791,000, 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, 2020 June 30, 2019 December 31, 2019 Recorded Valuation Recorded Valuation Recorded Valuation $ 39,320 $ 3,046 $ 26,408 $ 3,866 $ 24,582 $ 3,228
Schedule of Non-Accrual Loans	Non-accrual June 30, December 31, 2020 2019 2019 Commercial $ 4,618 $ 8,189 $ 3,093 Agricultural 1,056 1,047 1,376 Real estate 33,170 16,787 19,787 Consumer 476 385 326 Total $ 39,320 $ 26,408 $ 24,582
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, 2020 Unpaid Principal Balance Recorded Recorded Total Related Year-to-date Average Three- Commercial $ 6,013 $ 739 $ 3,879 $ 4,618 $ 1,250 $ 24,270 $ 23,572 Agricultural 1,287 529 527 1,056 83 219 179 Real Estate 45,703 20,370 12,800 33,170 1,711 17,586 17,107 Consumer 585 — 476 476 2 606 552 Total $ 53,588 $ 21,638 $ 17,682 $ 39,320 $ 3,046 $ 42,681 $ 41,410 * Includes $7,275,000 of purchased credit impaired loans. June 30, 2019 Unpaid Recorded Recorded Total Related Year-to-date Average Three- 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. December 31, 2019 Unpaid Principal Balance Recorded Recorded Total Related Year-to - date Average Recorded Investment Commercial $ 4,511 $ 630 $ 2,463 $ 3,093 $ 1,042 $ 3,488 Agricultural 1,603 658 718 1,376 235 1,644 Real Estate 27,366 7,081 12,706 19,787 1,950 21,726 Consumer 469 — 326 326 1 449 Total $ 33,949 $ 8,369 $ 16,213 $ 24,582 $ 3,228 $ 27,307 * Includes $251,000 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, 2020 Pass Special Substandard Doubtful Total Commercial $ 1,465,595 $ 8,950 $ 34,909 $ — $ 1,509,454 Agricultural 90,824 4,790 1,834 — 97,448 Real Estate 3,086,894 49,493 98,821 — 3,235,208 Consumer 408,857 256 1,844 — 410,957 Total $ 5,052,170 $ 63,489 $ 137,408 $ — $ 5,253,067 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 December 31, 2019 Pass Special Substandard Doubtful Total Commercial $ 825,775 $ 20,971 $ 9,580 $ — $ 856,326 Agricultural 101,614 64 1,962 — 103,640 Real Estate 2,717,227 42,036 64,109 — 2,823,372 Consumer 409,698 300 1,633 — 411,631 Total $ 4,054,314 $ 63,371 $ 77,284 $ — $ 4,194,969
Schedule of Past Due Loans	The Company’s past due loans are as follows (in thousands): June 30, 2020 15-59 Past 60-89 Past Greater Total Current Total 90 Days Commercial $ 4,563 $ 474 $ 129 $ 5,166 $ 1,504,288 $ 1,509,454 $ — Agricultural 1,080 15 — 1,095 96,353 97,448 — Real Estate 13,678 110 726 14,514 3,220,694 3,235,208 — Consumer 410 83 105 598 410,359 410,957 92 Total $ 19,731 $ 682 $ 960 $ 21,373 $ 5,231,694 $ 5,253,067 $ 92 June 30, 2019 15-59 Past 60-89 Past Greater Total Current Total 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 December 31, 2019 15-59 Past 60-89 Past Greater Total Current Total 90 Days Commercial $ 3,257 $ 557 $ 722 $ 4,536 $ 851,790 $ 856,326 $ 112 Agricultural 183 44 400 627 103,013 103,640 — Real Estate 12,890 288 195 13,373 2,809,999 2,823,372 — Consumer 572 151 45 768 410,863 411,631 41 Total $ 16,902 $ 1,040 $ 1,362 $ 19,304 $ 4,175,665 $ 4,194,969 $ 153 * 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 allowances for purchased credit impaired loans at June 30, 2020 and 2019, and December 31, 2019. Allocation of a portion of the allowance to one category of loans does not preclude its availability to absorb losses in other categories. June 30, 2020 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,250 $ 83 $ 1,711 $ 2 $ 3,046 Loans collectively evaluated for impairment 17,322 2,461 40,912 5,206 65,901 Total $ 18,572 $ 2,544 $ 42,623 $ 5,208 $ 68,947 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 December 31, 2019 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 1,042 $ 235 $ 1,950 $ 1 $ 3,228 Loans collectively evaluated for impairment 11,080 971 32,024 5,196 49,271 Total $ 12,122 $ 1,206 $ 33,974 $ 5,197 $ 52,499
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, 2020 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 11,773 $ 2,154 $ 41,256 $ 5,257 $ 60,440 Provision for loan losses 6,820 361 1,469 50 8,700 Recoveries 540 29 59 73 701 Charge-offs (561 ) — (161 ) (172 ) (894 ) Ending balance $ 18,572 $ 2,544 $ 42,623 $ 5,208 $ 68,947 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 Six months ended June 30, 2020 Commercial Agricultural Real Estate Consumer Total Beginning balance $ 12,122 $ 1,206 $ 33,974 $ 5,197 $ 52,499 Provision for loan losses 7,615 1,310 9,390 235 18,550 Recoveries 690 30 135 164 1,019 Charge-offs (1,855 ) (2 ) (876 ) (388 ) (3,121 ) Ending balance $ 18,572 $ 2,544 $ 42,623 $ 5,208 $ 68,947 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
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 $7,275,000, $464,000 and $251,000 at June 30, 2020 and 2019, and December 31, 2019, respectively, are included in loans individually evaluated for impairment. June 30, 2020 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 4,618 $ 1,056 $ 33,170 $ 476 $ 39,320 Loans collectively evaluated for impairment 1,504,836 96,392 3,202,038 410,481 5,213,747 Total $ 1,509,454 $ 97,448 $ 3,235,208 $ 410,957 $ 5,253,067 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 December 31, 2019 Commercial Agricultural Real Estate Consumer Total Loans individually evaluated for impairment $ 3,093 $ 1,376 $ 19,787 $ 326 $ 24,582 Loans collectively evaluated for impairment 853,233 102,264 2,803,585 411,305 4,170,387 Total $ 856,326 $ 103,640 $ 2,823,372 $ 411,631 $ 4,194,969
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, 2020 Six Months Ended June 30, 2020 Number Pre- Post- Number Pre- Post- Commercial 4 $ 196 $ 196 9 $ 484 $ 484 Agricultural — — — 1 134 134 Real Estate 1 123 123 1 123 123 Consumer — — — 1 14 14 Total 5 $ 319 $ 319 12 $ 755 $ 755 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
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, 2020 Six Months Ended June 30, 2020 Adjusted Extended Combined Maturity Adjusted Extended Combined Maturity Commercial $ — $ — $ 196 $ — $ 260 $ 224 Agricultural — — — — 134 — Real Estate — — 123 — — 123 Consumer — — — — 14 — Total $ — $ — $ 319 $ — $ 408 $ 347 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

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2020
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, 2020: Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value IRLCs $ 190,431 $ 5,037 $ — Forward mortgage-backed securities trades 201,500 — 1,099 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 December 31, 2019: Outstanding Notional Balance Asset Derivative Fair Value Liability Derivative Fair Value IRLCs $ 47,415 $ 886 $ — Forward mortgage-backed securities trades 78,500 — 152

Borrowings (Tables)

Borrowings (Tables)	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Schedule of Borrowings	Borrowings consisted of the following (dollars in thousands): June 30, December 31, 2020 2019 2019 Securities sold under agreements with customers to repurchase $ 444,249 $ 356,555 $ 375,106 Federal funds purchased 4,975 5,450 6,250 Advances from Federal Home Loan Bank of Dallas — — — Total $ 449,224 $ 362,005 $ 381,356

Fair Value Disclosures (Tables)

Fair Value Disclosures (Tables)	6 Months Ended
	Jun. 30, 2020
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 held-for-sale, June 30, 2020 Level 1 Level 2 Level 3 Total Fair Available-for-sale U.S. Treasury securities $ 10,122 $ — $ — $ 10,122 Obligations of states and political subdivisions — 1,950,279 — 1,950,279 Residential mortgage-backed securities — 1,571,673 — 1,571,673 Commercial mortgage-backed securities — 582,220 — 582,220 Other securities 4,569 — — 4,569 Total $ 14,691 $ 4,104,172 $ — $ 4,118,863 Loans held-for-sale $ — $ 63,293 $ — $ 63,293 IRLCs $ — $ 5,037 $ — $ 5,037 Forward mortgage-backed securities trades $ (1,099 ) $ — $ — $ (1,099 ) June 30, 2019 Level 1 Level 2 Level 3 Total Fair 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 ) December 31, 2019 Level 1 Inputs Level 2 Inputs Level 3 Inputs Total Fair Value Available-for-sale U.S. Treasury securities $ 10,019 $ — $ — $ 10,019 Obligations of states and political subdivisions — 1,288,983 1,288,983 Corporate bonds — 230 — 230 Residential mortgage-backed securities — 1,608,863 — 1,608,863 Commercial mortgage-backed securities — 500,744 — 500,744 Other securities 4,478 — — 4,478 Total $ 14,497 $ 3,398,820 $ — $ 3,413,317 Loans held-for-sale $ — $ 23,076 $ — $ 23,076 IRLCs $ — $ 886 $ — $ 886 Forward mortgage-backed securities trades $ (152 ) $ — $ — $ (152 )
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, 2020 2019 2019 Carrying Estimated Carrying Estimated Carrying Estimated Fair Value Cash and due from banks $ 188,373 $ 188,373 $ 178,345 $ 178,345 $ 231,534 $ 231,534 Level 1 Federal Funds Sold — — 700 700 3,150 3,150 Level 1 Interest-bearing demand deposits in banks 196,426 196,426 128,652 128,652 47,920 47,920 Level 1 Interest-bearing time deposits in banks — — 960 960 — — Level 2 Available-for-sale 4,118,863 4,118,863 3,259,492 3,259,492 3,413,317 3,413,317 Levels 1 and 2 Loans held for investment 5,184,120 5,174,126 3,989,132 4,026,543 4,142,470 4,209,826 Level 3 Loans held for sale 66,370 66,630 22,305 22,347 28,228 28,343 Level 2 Accrued interest receivable 45,801 45,801 36,954 36,954 36,894 36,894 Level 2 Deposits with stated maturities 466,122 468,819 433,511 433,811 420,013 421,397 Level 2 Deposits with no stated maturities 7,691,520 7,691,520 5,936,255 5,936,255 6,183,793 6,183,793 Level 1 Borrowings 449,224 449,224 362,005 362,005 381,356 381,356 Level 2 Accrued interest payable 541 541 694 694 628 628 Level 2 IRLCs 5,037 5,037 1,525 1,525 886 886 Level 2 Forward mortgage-backed securities trades 1,099 1,099 254 254 152 152 Level 1

Acquisition (Tables)

Acquisition (Tables)	6 Months Ended
	Jun. 30, 2020
Schedule of Preliminary Estimated Fair Value Amounts Assigned to Major Asset and Liability Categories at Acquisition Date	The following table presents the preliminary amounts recorded on the consolidated balance sheet on the acquisition date (dollars in thousands): Fair value of consideration paid: Common stock issued (6,275,574 shares) $ 220,273 Fair value of identifiable assets acquired: Cash and cash equivalents $ 61,028 Securities available-for-sale 93,967 Loans 447,702 Identifiable intangible assets 4,798 Other assets 25,377 Total identifiable assets acquired $ 632,872 Fair value of liabilities assumed: Deposits $ 549,125 Other liabilities 5,397 Total liabilities assumed $ 554,522 Fair value of net identifiable assets acquired 78,350 Goodwill resulting from acquisition $ 141,923

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail)	Jul. 28, 2020USD ($)shares	Apr. 23, 2019shares	Jul. 28, 2020shares	Jun. 30, 2020USD ($)shares	Jun. 30, 2019USD ($)shares	Jun. 30, 2020USD ($)Locationshares	Jun. 30, 2019USD ($)shares	Dec. 31, 2019USD ($)shares	Mar. 12, 2020shares	Jan. 01, 2020	Sep. 02, 2017shares
Equity, Class of Treasury Stock [Line Items]
Number of locations | Location						78
Stockholders' Equity Note, Stock Split		two-for-one stock split
Common stock, shares authorized | shares		200,000,000		200,000,000	200,000,000	200,000,000	200,000,000	200,000,000
Minimum number of shares that company is required to repurchase | shares						0
Minimum number of days to consider the loans as non-accrual						90 days
Loans individually evaluated for impairment				$ 39,320,000	$ 26,408,000	$ 39,320,000	$ 26,408,000	$ 24,582,000
Contractual balance				53,588,000	35,235,000	53,588,000	35,235,000	33,949,000
Impairment recorded						$ 0	0
Other identifiable intangible assets, amortized period (years)						7 years
Securities sold under agreements to repurchase maturity range (in days)						one to four days
Interest-bearing time deposits, maturity period (in days)						90 days or less
Unrealized net gains in available-for-sale securities, included in accumulated other comprehensive income				151,236,000	60,571,000	$ 151,236,000	60,571,000
Minimum pension liability, included in accumulated other comprehensive income				0	1,324,000	0	1,324,000
Stock compensation expense				$ 349,000	313,000	$ 689,000	625,000
First financial antidilutive securities excluded from eps computation | shares				448,000		35,000
Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury Stock, Shares, Acquired | shares	324,802		0
Treasury Stock, Value, Acquired	$ 8,008,000
Purchased Credit Impaired Loans [Member]
Equity, Class of Treasury Stock [Line Items]
Loans individually evaluated for impairment				$ 7,275,000	464,000	$ 7,275,000	464,000	251,000
Contractual balance				9,818,000	750,000	9,818,000	750,000
Officers [Member]
Equity, Class of Treasury Stock [Line Items]
Restricted stock expense				$ 482,000	$ 345,000	$ 932,000	$ 685,000	$ 345,000
Commercial Bancshares Inc and Commercial State Bank [Member]
Equity, Class of Treasury Stock [Line Items]
Percentage of common stock acquired										100.00%
Maximum [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, number of shares authorized to be repurchased | shares									4,000,000		2,000,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Computation of Basic EPS to Dilutive EPS (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net earnings	$ 53,470	$ 42,093	$ 90,701	$ 80,345
Effect of stock options and stock grants, Net Earnings	0	0	0	0
Net earnings per share, diluted, Net Earnings	$ 53,470	$ 42,093	$ 90,701	$ 80,345
Net earnings per share, basic, Weighted Average Shares	141,973,522	135,650,599	142,045,779	135,572,859
Effect of stock options and stock grants, Weighted Average Shares	480,561	567,636	473,529	622,952
Net earnings per share, diluted, Weighted Average Shares	142,454,083	136,218,235	142,519,308	136,195,811
Net earnings per share, basic, Per Share Amount	$ 0.38	$ 0.31	$ 0.64	$ 0.59
Effect of stock options and stock grants, Per Share Amount	0		0
Net earnings per share, diluted, Per Share Amount	$ 0.38	$ 0.31	$ 0.64	$ 0.59

Securities - Additional Informa

Securities - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020USD ($)Investment	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)Investment	Jun. 30, 2019USD ($)
Interest Bearing Time Deposits In Banks And Securities [Line Items]
Number of investment positions | Investment	14		14
Securities pledged as collateral	$ 2,685,828		$ 2,685,828
Sales of investment securities available-for-sale	157,521	$ 65,821	252,958	$ 66,052
Gross realized gains from security sales	1,516,000	689,000	3,578,000	693,000
Gross realized losses from security sales or calls	$ 4,000	$ 13,000	$ 4,000	$ 17,000
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	51.14%		51.14%
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			88.76%

Securities - Summary of Availab

Securities - Summary of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost Basis, Total	$ 3,927,254	$ 3,327,805	$ 3,182,772
Securities available-for-sale, Gross Unrealized Holding Gains	191,779	87,346	80,341
Securities available-for-sale, Gross Unrealized Holding Losses	(170)	(1,834)	(3,621)
Securities available-for-sale, Estimated Fair Value	4,118,863	3,413,317	3,259,492
U.S. Treasury securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost Basis, Total	10,083	9,997	9,984
Securities available-for-sale, Gross Unrealized Holding Gains	40	22	36
Securities available-for-sale, Gross Unrealized Holding Losses	(1)
Securities available-for-sale, Estimated Fair Value	10,122	10,019	10,020
Obligations of State and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost Basis, Total	1,836,572	1,231,619	1,103,682
Securities available-for-sale, Gross Unrealized Holding Gains	113,757	57,764	53,593
Securities available-for-sale, Gross Unrealized Holding Losses	(50)	(400)	(61)
Securities available-for-sale, Estimated Fair Value	1,950,279	1,288,983	1,157,214
Corporate Bonds and Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost Basis, Total	4,398	4,643	4,643
Securities available-for-sale, Gross Unrealized Holding Gains	171	65	51
Securities available-for-sale, Estimated Fair Value	4,569	4,708	4,694
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost Basis, Total	1,517,139	1,586,872	1,579,544
Securities available-for-sale, Gross Unrealized Holding Gains	54,652	23,139	19,732
Securities available-for-sale, Gross Unrealized Holding Losses	(118)	(1,148)	(3,101)
Securities available-for-sale, Estimated Fair Value	1,571,673	1,608,863	1,596,175
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost Basis, Total	559,062	494,674	484,919
Securities available-for-sale, Gross Unrealized Holding Gains	23,159	6,356	6,929
Securities available-for-sale, Gross Unrealized Holding Losses	(1)	(286)	(459)
Securities available-for-sale, Estimated Fair Value	$ 582,220	$ 500,744	$ 491,389

Securities - Amortized Cost and

Securities - Amortized Cost and Estimated Fair Value of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale, Amortized Cost Basis, Due within one year	$ 128,535
Available-for-Sale, Amortized Cost Basis, Due after one year through five years	625,856
Available-for-Sale, Amortized Cost Basis, Due after five years through ten years	1,079,767
Available-for-Sale, Amortized Cost Basis, Due after ten years	16,895
Available-for-Sale, Amortized Cost Basis, Mortgage-backed securities	2,076,201
Available-for-Sale, Amortized Cost Basis, Total	3,927,254	$ 3,327,805	$ 3,182,772
Available-for-Sale, Estimated Fair Value, Due within one year	129,521
Available-for-Sale, Estimated Fair Value, Due after one year through five years	669,229
Available-for-Sale, Estimated Fair Value, Due after five years through ten years	1,148,866
Available-for-Sale, Estimated Fair Value, Due after ten years	17,354
Available-for-Sale, Estimated Fair Value, Mortgage-backed securities	2,153,893
Securities available-for-sale, Estimated Fair Value, Total	$ 4,118,863	$ 3,413,317	$ 3,259,492

Securities - Continuous Unreali

Securities - Continuous Unrealized-Loss Position of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Fair Value	$ 40,830	$ 240,351	$ 17,594
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	97	884	77
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value	6,454	139,487	549,604
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss	73	950	3,544
Available-for-sale securities, continuous unrealized loss position, Fair Value	47,284	379,838	567,198
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss	170	1,834	3,621
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	5,055
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	1
Available-for-sale securities, continuous unrealized loss position, Fair Value	5,055
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	18,249	65,787
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	50	400
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value		326	9,777
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss			61
Available-for-sale securities, continuous unrealized loss position, Fair Value	18,249	66,113	9,777
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss	50	400	61
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	12,590	100,004	17,594
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	45	306	77
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value	6,454	103,983	404,946
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss	73	842	3,024
Available-for-sale securities, continuous unrealized loss position, Fair Value	19,044	203,987	422,540
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss	118	1,148	3,101
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	4,936	74,560
Available-for-sale securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	1	178
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Fair Value	0	35,178	134,881
Available-for-sale securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss	0	108	459
Available-for-sale securities, continuous unrealized loss position, Fair Value	4,936	109,738	134,881
Available-for-sale securities, continuous unrealized loss position, Unrealized Loss	$ 1	$ 286	$ 459

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, 2020	Dec. 31, 2019	Jun. 30, 2019
Loans and Leases Receivable Disclosure [Line Items]
Total loans held-for-investment	$ 5,253,067	$ 4,194,969	$ 4,040,952
Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans held-for-investment	1,509,454	856,326	813,887
Agriculture [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans held-for-investment	97,448	103,640	97,535
Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans held-for-investment	3,235,208	2,823,372	2,730,585
Consumer [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans held-for-investment	$ 410,957	$ 411,631	$ 398,945

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		Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Receivables [Abstract]
Non-accrual loans	[1]	$ 39,320	$ 24,582	$ 26,408
Loans still accruing and past due 90 days or more		92	153	300
Troubled debt restructured loans still accruing	[2]	25	26	471
Total		$ 39,437	$ 24,761	$ 27,179
[1]	Includes $7,275,000, $464,000 and $251,000 of purchased credit impaired loans as of June 30, 2020 and 2019, and December 31, 2019, respectively.
[2]	Troubled debt restructured loans of $4,673,000, $3,906,000 and $4,791,000, whose interest collection, after considering economic and business conditions and collection efforts, is doubtful are included in non-accrual loans at June 30, 2020 and 2019, and December 31, 2019, 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 ($)		Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	[1]	$ 39,320,000	$ 24,582,000	$ 26,408,000
Troubled debt restructured loans	[2]	25,000	26,000	471,000
Doubtful [Member]
Loans and Leases Receivable Disclosure [Line Items]
Troubled debt restructured loans		4,673,000	4,791,000	3,906,000
Purchased Credit Impaired Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans		$ 7,275,000	$ 251,000	$ 464,000
[1]	Includes $7,275,000, $464,000 and $251,000 of purchased credit impaired loans as of June 30, 2020 and 2019, and December 31, 2019, respectively.
[2]	Troubled debt restructured loans of $4,673,000, $3,906,000 and $4,791,000, whose interest collection, after considering economic and business conditions and collection efforts, is doubtful are included in non-accrual loans at June 30, 2020 and 2019, and December 31, 2019, 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 ($)		Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Receivables [Abstract]
Recorded Investment	[1]	$ 39,320,000	$ 24,582,000	$ 26,408,000
Valuation Allowance		$ 3,046,000	$ 3,228,000	$ 3,866,000
[1]	Includes $7,275,000, $464,000 and $251,000 of purchased credit impaired loans as of June 30, 2020 and 2019, and December 31, 2019, respectively.

Loans Held for Investment and_7

Loans Held for Investment and Allowance for Loan Losses - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2018
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	$ 39,724,000	$ 25,770,000
Additional funds advanced in connection with impaired loans		0
Interest income recognized on impaired loans		0
Interest income recognized on impaired loans			750,000
Allowance for loan losses	51,820,000	68,947,000	52,499,000	$ 60,440,000	$ 51,585,000	$ 51,202,000
Loans individually evaluated for impairment	$ 26,408,000	$ 39,320,000	24,582,000
Default for purposes of this disclosure is a troubled debt restructured loan	90 days	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		3,134,584,000
Advances from Federal Home Loan Bank of Dallas		0
loans subject to deferral and modification agreements	$ 4,040,952,000	5,253,067,000	4,194,969,000
Deferral And Modification Agreement [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
loans subject to deferral and modification agreements		$ 468,539,000,000,000
Outstanding loans held for investment Percentage		10.30%
Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0	$ 0
Loans individually evaluated for impairment	$ 464,000	$ 7,275,000	$ 251,000

Loans Held for Investment and_8

Loans Held for Investment and Allowance for Loan Losses - Schedule of Non-Accrual Loans (Detail) - USD ($) $ in Thousands		Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans	[1]	$ 39,320	$ 24,582	$ 26,408
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans		4,618	3,093	8,189
Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans		1,056	1,376	1,047
Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans		33,170	19,787	16,787
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual loans		$ 476	$ 326	$ 385
[1]	Includes $7,275,000, $464,000 and $251,000 of purchased credit impaired loans as of June 30, 2020 and 2019, and December 31, 2019, 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 ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	$ 53,588,000	$ 35,235,000	$ 53,588,000	$ 35,235,000	$ 33,949,000
Recorded Investment With No Allowance	21,638,000	11,707,000	21,638,000	11,707,000	8,369,000
Recorded Investment With Allowance	17,682,000	14,701,000	17,682,000	14,701,000	16,213,000
Total Recorded Investment	39,320,000	26,408,000	39,320,000	26,408,000	24,582,000
Related Allowance	3,046,000	3,866,000	3,046,000	3,866,000	3,228,000
Average Recorded Investment	41,410,000	27,165,000	42,681,000	28,308,000	27,307,000
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	6,013,000	9,340,000	6,013,000	9,340,000	4,511,000
Recorded Investment With No Allowance	739,000	6,212,000	739,000	6,212,000	630,000
Recorded Investment With Allowance	3,879,000	1,977,000	3,879,000	1,977,000	2,463,000
Total Recorded Investment	4,618,000	8,189,000	4,618,000	8,189,000	3,093,000
Related Allowance	1,250,000	1,022,000	1,250,000	1,022,000	1,042,000
Average Recorded Investment	23,572,000	8,562,000	24,270,000	8,699,000	3,488,000
Agriculture [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	1,287,000	1,108,000	1,287,000	1,108,000	1,603,000
Recorded Investment With No Allowance	529,000	434,000	529,000	434,000	658,000
Recorded Investment With Allowance	527,000	613,000	527,000	613,000	718,000
Total Recorded Investment	1,056,000	1,047,000	1,056,000	1,047,000	1,376,000
Related Allowance	83,000	119,000	83,000	119,000	235,000
Average Recorded Investment	179,000	1,071,000	219,000	1,090,000	1,644,000
Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	45,703,000	24,262,000	45,703,000	24,262,000	27,366,000
Recorded Investment With No Allowance	20,370,000	5,034,000	20,370,000	5,034,000	7,081,000
Recorded Investment With Allowance	12,800,000	11,753,000	12,800,000	11,753,000	12,706,000
Total Recorded Investment	33,170,000	16,787,000	33,170,000	16,787,000	19,787,000
Related Allowance	1,711,000	2,515,000	1,711,000	2,515,000	1,950,000
Average Recorded Investment	17,107,000	17,105,000	17,586,000	18,054,000	21,726,000
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Contractual Principal Balance	585,000	525,000	585,000	525,000	469,000
Recorded Investment With No Allowance	0	27,000	0	27,000	0
Recorded Investment With Allowance	476,000	358,000	476,000	358,000	326,000
Total Recorded Investment	476,000	385,000	476,000	385,000	326,000
Related Allowance	2,000	210,000	2,000	210,000	1,000
Average Recorded Investment	$ 552,000	$ 427,000	$ 606,000	$ 465,000	$ 449,000

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 ($)	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Allowance	$ 21,638,000	$ 8,369,000	$ 11,707,000
Purchased Credit Impaired Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment With No Allowance	$ 7,275,000	$ 251,000	$ 464,000

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, 2020	Dec. 31, 2019	Jun. 30, 2019
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	$ 5,253,067	$ 4,194,969	$ 4,040,952
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	1,509,454	856,326	813,887
Agriculture [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	97,448	103,640	97,535
Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	3,235,208	2,823,372	2,730,585
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	410,957	411,631	398,945
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	5,052,170	4,054,314	3,914,912
Pass [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	1,465,595	825,775	767,275
Pass [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	90,824	101,614	94,481
Pass [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	3,086,894	2,717,227	2,656,139
Pass [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	408,857	409,698	397,017
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	63,489	63,371	51,490
Special Mention [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	8,950	20,971	31,124
Special Mention [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	4,790	64	58
Special Mention [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	49,493	42,036	20,044
Special Mention [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	256	300	264
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	137,408	77,284	74,550
Substandard [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	34,909	9,580	15,488
Substandard [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	1,834	1,962	2,996
Substandard [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	98,821	64,109	54,402
Substandard [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Internal ratings of loan	$ 1,844	$ 1,633	$ 1,664

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, 2020	Dec. 31, 2019	Jun. 30, 2019
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 21,373	$ 19,304	$ 22,808
Total Current	5,231,694	4,175,665	4,018,144
Total Loans	5,253,067	4,194,969	4,040,952
Total 90 Days Past Due Still Accruing	92	153	300
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,166	4,536	3,633
Total Current	1,504,288	851,790	810,254
Total Loans	1,509,454	856,326	813,887
Total 90 Days Past Due Still Accruing	0	112	58
Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,095	627	508
Total Current	96,353	103,013	97,027
Total Loans	97,448	103,640	97,535
Total 90 Days Past Due Still Accruing			30
Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	14,514	13,373	17,707
Total Current	3,220,694	2,809,999	2,712,878
Total Loans	3,235,208	2,823,372	2,730,585
Total 90 Days Past Due Still Accruing			180
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	598	768	960
Total Current	410,359	410,863	397,985
Total Loans	410,957	411,631	398,945
Total 90 Days Past Due Still Accruing	92	41	32
15-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	19,731	16,902	19,937
15-59 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	4,563	3,257	2,671
15-59 Days Past Due [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,080	183	315
15-59 Days Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	13,678	12,890	16,130
15-59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	410	572	821
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	682	1,040	1,326
60-89 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	474	557	352
60-89 Days Past Due [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	15	44	163
60-89 Days Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	110	288	712
60-89 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	83	151	99
Greater than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	960	1,362	1,545
Greater than 90 Days [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	129	722	610
Greater than 90 Days [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	400	30
Greater than 90 Days [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	726	195	865
Greater than 90 Days [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 105	$ 45	$ 40

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, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	$ 3,046		$ 3,228	$ 3,866
Loan collectively evaluated for impairment	65,901		49,271	47,954
Total allowance for loan losses	68,947	$ 60,440	52,499	51,820	$ 51,585	$ 51,202
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	1,250		1,042	1,022
Loan collectively evaluated for impairment	17,322		11,080	12,877
Total allowance for loan losses	18,572	11,773	12,122	13,899	12,475	11,948
Agriculture [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	83		235	119
Loan collectively evaluated for impairment	2,461		971	1,241
Total allowance for loan losses	2,544	2,154	1,206	1,360	1,430	1,446
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	1,711		1,950	2,515
Loan collectively evaluated for impairment	40,912		32,024	28,284
Total allowance for loan losses	42,623	41,256	33,974	30,799	31,887	32,342
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	2		1	210
Loan collectively evaluated for impairment	5,206		5,196	5,552
Total allowance for loan losses	$ 5,208	$ 5,257	$ 5,197	$ 5,762	$ 5,793	$ 5,466

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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 60,440	$ 51,585	$ 52,499	$ 51,202
Provision for loan losses	8,700	600	18,550	1,565
Recoveries	701	697	1,019	1,578
Charge-offs	(894)	(1,062)	(3,121)	(2,525)
Ending balance	68,947	51,820	68,947	51,820
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	11,773	12,475	12,122	11,948
Provision for loan losses	6,820	1,418	7,615	1,612
Recoveries	540	423	690	1,073
Charge-offs	(561)	(417)	(1,855)	(734)
Ending balance	18,572	13,899	18,572	13,899
Agriculture [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	2,154	1,430	1,206	1,446
Provision for loan losses	361	61	1,310	42
Recoveries	29	5	30	7
Charge-offs	0	(136)	(2)	(135)
Ending balance	2,544	1,360	2,544	1,360
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	41,256	31,887	33,974	32,342
Provision for loan losses	1,469	(929)	9,390	(531)
Recoveries	59	60	135	149
Charge-offs	(161)	(219)	(876)	(1,161)
Ending balance	42,623	30,799	42,623	30,799
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	5,257	5,793	5,197	5,466
Provision for loan losses	50	50	235	442
Recoveries	73	209	164	349
Charge-offs	(172)	(290)	(388)	(495)
Ending balance	$ 5,208	$ 5,762	$ 5,208	$ 5,762

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, 2020	Dec. 31, 2019	Jun. 30, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	$ 39,320	$ 24,582	$ 26,408
Loan collectively evaluated for impairment	5,213,747	4,170,387	4,014,544
Total	5,253,067	4,194,969	4,040,952
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	4,618	3,093	8,189
Loan collectively evaluated for impairment	1,504,836	853,233	805,698
Total	1,509,454	856,326	813,887
Agriculture [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	1,056	1,376	1,047
Loan collectively evaluated for impairment	96,392	102,264	96,488
Total	97,448	103,640	97,535
Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	33,170	19,787	16,787
Loan collectively evaluated for impairment	3,202,038	2,803,585	2,713,798
Total	3,235,208	2,823,372	2,730,585
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	476	326	385
Loan collectively evaluated for impairment	410,481	411,305	398,560
Total	$ 410,957	$ 411,631	$ 398,945

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, 2020USD ($)SecurityLoan	Jun. 30, 2019USD ($)SecurityLoan	Jun. 30, 2020USD ($)SecurityLoan	Jun. 30, 2019USD ($)SecurityLoan
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan	5	4	12	17
Pre-Modification Recorded Investment	$ 319	$ 375	$ 755	$ 1,548
Post-Modification Recorded Investment	$ 319	$ 375	$ 755	$ 1,548
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan	4	2	9	3
Pre-Modification Recorded Investment	$ 196	$ 122	$ 484	$ 279
Post-Modification Recorded Investment	$ 196	$ 122	$ 484	$ 279
Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan		2	1	10
Pre-Modification Recorded Investment		$ 253	$ 134	$ 619
Post-Modification Recorded Investment		253	$ 134	$ 619
Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan	1		1	4
Pre-Modification Recorded Investment	$ 123		$ 123	$ 650
Post-Modification Recorded Investment	$ 123		$ 123	$ 650
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number | SecurityLoan			1
Pre-Modification Recorded Investment			$ 14
Post-Modification Recorded Investment		$ 0	$ 14

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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	$ 319	$ 375	$ 755	$ 1,548
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	196	122	484	279
Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		253	134	619
Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	123		123	650
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans			14
Extended Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		375	408	835
Extended Maturity [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		122	260	279
Extended Maturity [Member] | Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans		$ 253	134	354
Extended Maturity [Member] | Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans				202
Extended Maturity [Member] | Consumer [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans			14
Combined Rate and Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	319		347	713
Combined Rate and Maturity [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	196		224
Combined Rate and Maturity [Member] | Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans				265
Combined Rate and Maturity [Member] | Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	$ 123		$ 123	$ 448

Loans Held for Sale - Additiona

Loans Held for Sale - Additional Information (Detail) - USD ($)	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Loans Receivables Held For Sale Net [Abstract]
Loans held for sale	$ 66,370,000	$ 28,228,000	$ 22,305,000
Loans held-for-sale at the lower of cost or fair value	$ 3,077,000	$ 5,152,000	$ 3,324,000

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, 2020	Dec. 31, 2019	Jun. 30, 2019
IRLCs [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Outstanding Notional Balance	$ 190,431	$ 47,415	$ 89,655
Asset Derivative Fair Value	5,037	886	1,525
Forward Mortgage-Backed Securities Trades [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Outstanding Notional Balance	201,500	78,500	72,500
Liability Derivative Fair Value	$ 1,099	$ 152	$ 254

Borrowings - Schedule of Borrow

Borrowings - Schedule of Borrowings (Detail) - USD ($)	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Debt Disclosure [Abstract]
Securities sold under agreements with customers to repurchase	$ 444,249,000	$ 375,106,000	$ 356,555,000
Federal funds purchased	4,975,000	6,250,000	5,450,000
Advances from Federal Home Loan Bank of Dallas	0
Total	$ 449,224,000	$ 381,356,000	$ 362,005,000

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Taxes [Line Items]
Federal statutory tax rate			21.00%
Income tax expense	$ 10,663	$ 8,594	$ 17,898	$ 15,959
Effective tax rates on pre-tax income	16.63%	16.96%	16.48%	16.57%

Stock Option Plan and Restric_2

Stock Option Plan and Restricted Stock Plan - Additional Information (Detail) - USD ($)	May 18, 2020	Apr. 28, 2020	Jan. 28, 2020	Oct. 22, 2019	Jun. 26, 2019	Apr. 23, 2019	Oct. 23, 2018	Apr. 24, 2018	Oct. 24, 2017	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value assumptions method used												Black-Scholes options pricing model
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										$ 349,000	$ 313,000	$ 689,000	$ 625,000
Granted, Shares			11,250		398,850
Granted the period exercise price			$ 34.55		$ 29.70
Restricted Stock [Member] | Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted		21,560	434			21,714		21,420
Restricted shares value		$ 600,000	$ 15,000			$ 660,000		$ 540,000
Restricted Stock [Member] | Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense										160,000	135,000	335,000	270,000
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	3 years		3 years
Restricted shares granted	7,176		2,979	22,188	23,428		52,042		28,382
Restricted shares value	$ 200,000		$ 103,000	$ 785,000	$ 695,000		$ 1,440,000		$ 655,000
Stock compensation expense										$ 322,000	$ 210,000	$ 597,000	$ 415,000
Restricted Stock [Member] | Officers [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares vesting period									1 year
Restricted Stock [Member] | Officers [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares vesting period									3 years

Pension Plan - Additional Infor

Pension Plan - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan pension obligation retirement benefit percentage				53.00%
Defined benefit plan pension obligation, loss on settlement			$ 2,673,000	$ 1,546,000
Net periodic benefit costs, total	$ 19,000	$ 942,000

Fair Value Disclosures - Additi

Fair Value Disclosures - Additional Information (Detail)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets transfer between Level 2 and Level 3	$ 0	$ 0	$ 0	$ 0	$ 0
Impaired loans carrying value, recorded investment with allowance	17,682,000	14,701,000	17,682,000	14,701,000	16,213,000
Impaired loans valuation reserves	3,046,000	3,866,000	3,046,000	3,866,000	3,228,000
Impaired loans net fair value	14,636,000		14,636,000
Other real estate owned, total	$ 202,000	$ 635,000	$ 202,000	$ 635,000	$ 982,000
Minimum [Member] | Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt discounts, percentage	5		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		25

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, 2020	Dec. 31, 2019	Jun. 30, 2019
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	$ 4,118,863	$ 3,413,317	$ 3,259,492
Loans held-for-sale	66,370	28,228	22,305
U.S. Treasury Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	10,122	10,019	10,020
Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	1,950,279	1,288,983	1,157,214
Residential Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	1,571,673	1,608,863	1,596,175
Commercial Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	582,220	500,744	491,389
IRLCs [Member]
Available-for-sale investment securities:
Asset Derivative Fair Value	5,037	886	1,525
Forward Mortgage-Backed Securities Trades [Member]
Available-for-sale investment securities:
Forward mortgage-backed securities trades	1,099	152	254
Fair Value, Measurements, Recurring [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	4,118,863	3,413,317	3,259,492
Loans held-for-sale	63,293	23,076	18,981
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	10,122	10,019	10,020
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	1,950,279	1,288,983	1,157,214
Fair Value, Measurements, Recurring [Member] | Residential Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	1,571,673	1,608,863	1,596,175
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	582,220	500,744	491,389
Fair Value, Measurements, Recurring [Member] | IRLCs [Member]
Available-for-sale investment securities:
Asset Derivative Fair Value	5,037	886	1,525
Fair Value, Measurements, Recurring [Member] | Forward Mortgage-Backed Securities Trades [Member]
Available-for-sale investment securities:
Forward mortgage-backed securities trades	(1,099)	(152)	(254)
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value		230	228
Fair Value, Measurements, Recurring [Member] | Other Securities [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	4,569	4,478	4,466
Fair Value, Measurements, Recurring [Member] | Level 1 Inputs [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	14,691	14,497	14,486
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	10,122	10,019	10,020
Fair Value, Measurements, Recurring [Member] | Level 1 Inputs [Member] | Forward Mortgage-Backed Securities Trades [Member]
Available-for-sale investment securities:
Forward mortgage-backed securities trades	(1,099)	(152)	(254)
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	4,569	4,478	4,466
Fair Value, Measurements, Recurring [Member] | Level 2 Inputs [Member]
Available-for-sale investment securities:
Available-for-sale investment securities, Total Fair Value	4,104,172	3,398,820	3,245,006
Loans held-for-sale	63,293	23,076	18,981
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	1,950,279	1,288,983	1,157,214
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	1,571,673	1,608,863	1,596,175
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	582,220	500,744	491,389
Fair Value, Measurements, Recurring [Member] | Level 2 Inputs [Member] | IRLCs [Member]
Available-for-sale investment securities:
Asset Derivative Fair Value	$ 5,037	886	1,525
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		$ 230	$ 228

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, 2020	Dec. 31, 2019	Jun. 30, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 188,373	$ 231,534	$ 178,345
Federal funds sold	0	3,150	700
Interest-bearing demand deposits in banks	196,426	47,920	128,652
Interest-bearing time deposits in banks			960
Available-for-sale securities	4,118,863	3,413,317	3,259,492
Loans held for investment	5,184,120	4,142,470	3,989,132
Loans held for sale	66,370	28,228	22,305
Borrowings	449,224	381,356	362,005
IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	5,037	886	1,525
Forward Mortgage-Backed Securities Trades [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Forward mortgage-backed securities trades	1,099	152	254
Carrying Value [Member] | Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	188,373	231,534	178,345
Federal funds sold		3,150	700
Interest-bearing demand deposits in banks	196,426	47,920	128,652
Deposits with no stated maturities	7,691,520	6,183,793	5,936,255
Carrying Value [Member] | Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest-bearing time deposits in banks			960
Loans held for sale	66,370	28,228	22,305
Accrued interest receivable	45,801	36,894	36,954
Deposits with stated maturities	466,122	420,013	433,511
Borrowings	449,224	381,356	362,005
Accrued interest payable	541	628	694
Carrying Value [Member] | Level 2 Inputs [Member] | IRLCs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset Derivative Fair Value	5,037	886	1,525
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	1,099	152	254
Carrying Value [Member] | Levels 1 and 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	4,118,863	3,413,317	3,259,492
Carrying Value [Member] | Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for investment	5,184,120	4,142,470	3,989,132
Estimated Fair Value [Member] | Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	188,373	231,534	178,345
Federal funds sold		3,150	700
Interest-bearing demand deposits in banks	196,426	47,920	128,652
Deposits with no stated maturities	7,691,520	6,183,793	5,936,255
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
Loans held for sale	66,630	28,343	22,347
Accrued interest receivable	45,801	36,894	36,954
Deposits with stated maturities	468,819	421,397	433,811
Borrowings	449,224	381,356	362,005
Accrued interest payable	541	628	694
Asset Derivative Fair Value	5,037	886
Forward mortgage-backed securities trades	1,099	152
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
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
Estimated Fair Value [Member] | Levels 1 and 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	4,118,863	3,413,317	3,259,492
Estimated Fair Value [Member] | Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for investment	$ 5,174,126	$ 4,209,826	$ 4,026,543

Acquisition - Additional Inform

Acquisition - Additional Information (Detail) - USD ($)	Jan. 02, 2020	Sep. 19, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Business Acquisition [Line Items]
Fair value of total loans			$ 447,702,000
Fair value of purchased credit impaired loans			39,320,000	$ 24,582,000	$ 26,408,000
Contractual amounts			53,588,000	$ 33,949,000	35,235,000
Purchased Credit Impaired Loans [Member]
Business Acquisition [Line Items]
Contractual amounts			9,818,000		$ 750,000
FBC Bancshares, Inc. and First Bank, N.A. [Member]
Business Acquisition [Line Items]
Payment for all outstanding shares of acquired entity by shares		6,275,574
Total loans of contractual amounts			455,181,000
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			7,517,000
Contractual amounts			$ 10,061,000
Commercial Bancshares, Inc [Member]
Business Acquisition [Line Items]
Business acquisition, agreement date			Sep. 19, 2019
Payment for all outstanding shares of acquired entity by shares	6,275,574
Business acquisition, special dividend	$ 1,920,000

Acquisition - Schedule of Amoun

Acquisition - Schedule of Amounts Recorded on Consolidated Balance Sheet on Acquisition Date (Detail) $ in Thousands	Sep. 19, 2019USD ($)
FBC Bancshares, Inc. and First Bank, N.A. [Member]
Business Acquisition [Line Items]
Common stock issued (6,275,574 shares)	$ 220,273

Acquisition - Schedule of Amo_2

Acquisition - Schedule of Amounts Recorded on Consolidated Balance Sheet on Acquisition Date (Parenthetical) (Detail)	Sep. 19, 2019shares
FBC Bancshares, Inc. and First Bank, N.A. [Member]
Business Acquisition [Line Items]
Common stock issued shares	6,275,574

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, 2020USD ($)
Business Acquisition [Line Items]
Cash and cash equivalents	$ 61,028
Securities available-for-sale	93,967
Loans	447,702
Identifiable intangible assets	4,798
Other assets	25,377
Total identifiable assets acquired	632,872
Deposits	549,125
Other liabilities	5,397
Total liabilities assumed	554,522
Fair value of net identifiable assets acquired	78,350
Goodwill resulting from acquisition	$ 141,923