Independent Bank (IBTX) 10-K 1 Mar 21 2020 FY Annual report Financial data

Cover

Cover - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 25, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	001-35854
Entity Registrant Name	Independent Bank Group, Inc.
Entity Incorporation, State or Country Code	TX
Entity Tax Identification Number	13-4219346
Entity Address, Address Line One	7777 Henneman Way
Entity Address, City or Town	McKinney,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75070-1711
City Area Code	972
Local Phone Number	562-9004
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	IBTX
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1,494,273,058
Entity Common Stock, Shares Outstanding		43,192,020
Documents Incorporated by Reference	Portions of the Company’s Proxy Statement relating to the 2021 Annual Meeting of Shareholders, which will be filed within 120 days after December 31, 2020, are incorporated by reference into Part III, Items 10 - 14 of this Annual Report on Form 10-K.
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0001564618
Current Fiscal Year End Date	--12-31

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets
Cash and due from banks	$ 250,485	$ 186,299
Interest-bearing deposits in other banks	1,563,502	378,871
Cash and cash equivalents	1,813,987	565,170
Certificates of deposit held in other banks	4,482	5,719
Securities available for sale, at fair value	1,153,693	1,085,936
Loans held for sale (includes $71,769 and $29,204 carried at fair value, respectively)	82,647	35,645
Loans, net	12,978,238	11,562,814
Premises and equipment, net	249,467	242,874
Other real estate owned	475	4,819
Federal Home Loan Bank (FHLB) of Dallas stock and other restricted stock	20,305	30,052
Bank-owned life insurance (BOLI)	220,428	215,081
Deferred tax asset	3,933	6,943
Goodwill	994,021	994,021
Other intangible assets, net	88,070	100,741
Other assets	143,730	108,392
Total assets	17,753,476	14,958,207
Deposits:
Noninterest-bearing	4,164,800	3,240,185
Interest-bearing	10,234,127	8,701,151
Total deposits	14,398,927	11,941,336
FHLB advances	375,000	325,000
Other borrowings	312,175	202,251
Junior subordinated debentures	54,023	53,824
Other liabilities	97,980	96,023
Total liabilities	15,238,105	12,618,434
Commitments and contingencies
Stockholders’ equity:
Preferred stock (0 and 0 shares outstanding, respectively)	0	0
Common stock (43,137,104 and 42,950,228 shares outstanding, respectively)	431	430
Additional paid-in capital	1,934,807	1,926,359
Retained earnings	543,800	393,674
Accumulated other comprehensive income	36,333	19,310
Total stockholders’ equity	2,515,371	2,339,773
Total liabilities and stockholders’ equity	$ 17,753,476	$ 14,958,207

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Loans held for sale, fair value option	$ 71,769	$ 29,204
Operating lease, liability, statement of financial position	us-gaap:OtherLiabilities	us-gaap:OtherLiabilities
Preferred stock, shares outstanding (shares)	0	0
Common stock, shares outstanding (shares)	43,137,104	42,950,228

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest income:
Interest and fees on loans	$ 579,085	$ 611,589	$ 384,791
Interest on taxable securities	19,150	21,324	14,007
Interest on nontaxable securities	8,472	8,482	4,580
Interest on interest-bearing deposits and other	4,799	11,537	3,912
Total interest income	611,506	652,932	407,290
Interest expense:
Interest on deposits	76,266	123,384	60,767
Interest on FHLB advances	4,170	10,173	10,264
Interest on other borrowings	12,462	11,590	8,398
Interest on junior subordinated debentures	2,162	3,028	1,609
Total interest expense	95,060	148,175	81,038
Net interest income	516,446	504,757	326,252
Provision for loan losses	42,993	14,805	9,860
Net interest income after provision for loan losses	473,453	489,952	316,392
Noninterest income:
Service charges on deposit accounts	9,303	12,145	7,039
Investment management and trust	7,546	9,330	0
Mortgage banking revenue	36,491	15,461	15,512
Gain on sale of loans	356	6,779	0
Gain on sale of branches	0	1,549	0
Gain on sale of trust business	0	1,319	0
(Loss) gain on sale of other real estate	(36)	875	269
Gain (loss) on sale of securities available for sale	382	275	(581)
Gain (loss) on sale and disposal of premises and equipment	370	(585)	123
Increase in cash surrender value of BOLI	5,347	5,525	3,170
Other	25,304	25,503	16,692
Total noninterest income	85,063	78,176	42,224
Noninterest expense:
Salaries and employee benefits	157,540	162,683	111,697
Occupancy	39,210	37,654	24,786
Communications and technology	23,113	22,248	14,107
FDIC assessment	6,912	1,065	3,306
Advertising and public relations	2,416	2,527	1,907
Other real estate owned expenses, net	487	418	318
Impairment of other real estate	784	1,801	85
Amortization of other intangible assets	12,671	12,880	5,739
Professional fees	12,630	7,936	4,556
Acquisition expense, including legal	16,225	33,445	6,157
Other	34,146	39,207	25,961
Total noninterest expense	306,134	321,864	198,619
Income before taxes	252,382	246,264	159,997
Income tax expense	51,173	53,528	31,738
Net income	$ 201,209	$ 192,736	$ 128,259
Basic earnings per share (usd per share)	$ 4.67	$ 4.46	$ 4.33
Diluted earnings per share (usd per share)	$ 4.67	$ 4.46	$ 4.33

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 201,209	$ 192,736	$ 128,259
Other comprehensive income (loss) before tax:
Change in net unrealized gains (losses) on available for sale securities during the year	21,540	35,620	(10,182)
Reclassification for amount realized through sales of securities available for sale included in net income	(382)	(275)	581
Other comprehensive income (loss) before tax	21,158	35,345	(9,601)
Income tax expense (benefit)	4,135	7,730	(2,016)
Other comprehensive income (loss), net of tax	17,023	27,615	(7,585)
Comprehensive income	$ 218,232	$ 220,351	$ 120,674

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock $0.01 Par Value 10 million shares authorized	Common Stock $0.01 Par Value 100 million shares authorized	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Cumulative effect of change in accounting principles	Cumulative effect of change in accounting principlesRetained Earnings	Cumulative effect of change in accounting principlesAccumulated Other Comprehensive (Loss) Income	Cumulative effect, period of adoption, adjusted balance	Cumulative effect, period of adoption, adjusted balancePreferred Stock $0.01 Par Value 10 million shares authorized	Cumulative effect, period of adoption, adjusted balanceCommon Stock $0.01 Par Value 100 million shares authorized	Cumulative effect, period of adoption, adjusted balanceAdditional Paid in Capital	Cumulative effect, period of adoption, adjusted balanceRetained Earnings	Cumulative effect, period of adoption, adjusted balanceAccumulated Other Comprehensive (Loss) Income
Beginning balance (in shares) at Dec. 31, 2017			28,254,893									28,254,893
Beginning balance at Dec. 31, 2017	$ 1,336,018	$ 0	$ 283	$ 1,151,990	$ 184,232	$ (487)	$ 0	$ 233	$ (233)	$ 1,336,018	$ 0	$ 283	$ 1,151,990	$ 184,465	$ (720)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	128,259				128,259
Other comprehensive income (loss), net of tax	(7,585)					(7,585)
Stock issued for acquisition of bank, net of offering costs (in shares)			2,071,981
Stock issued for acquisition of bank, net of offering costs of $209 and $804 as of December 31, 2018 and 2019, respectively	157,054		$ 21	157,033
Restricted stock forfeited (in shares)			(3,845)
Restricted stock forfeited	0
Restricted stock granted (in shares)			130,212
Restricted stock granted	0		$ 1	(1)
Stock based compensation expense	6,062			6,062
Exercise of warrants (in shares)			147,341
Exercise of warrants	2,533		$ 1	2,532
Cash dividends ($0.54, $1.00 and $1.05 per share as of December 31, 2018, 2019 and 2020, respectively)	(15,908)				(15,908)
Ending balance (in shares) at Dec. 31, 2018			30,600,582									30,600,582
Ending balance at Dec. 31, 2018	1,606,433	0	$ 306	1,317,616	296,816	(8,305)	$ (926)	$ (926)		$ 1,605,507	$ 0	$ 306	$ 1,317,616	$ 295,890	$ (8,305)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	192,736				192,736
Other comprehensive income (loss), net of tax	27,615					27,615
Stock issued for acquisition of bank, net of offering costs (in shares)			13,179,748
Stock issued for acquisition of bank, net of offering costs of $209 and $804 as of December 31, 2018 and 2019, respectively	601,068		$ 132	600,936
Common stock repurchased (shares)			(952,844)
Common stock repurchased	(51,659)		$ (9)		(51,650)
Restricted stock forfeited (in shares)			(15,866)
Restricted stock forfeited	0		$ 0
Restricted stock granted (in shares)			138,608
Restricted stock granted	0		$ 1	(1)
Stock based compensation expense	7,808			7,808
Cash dividends ($0.54, $1.00 and $1.05 per share as of December 31, 2018, 2019 and 2020, respectively)	(43,302)				(43,302)
Ending balance (in shares) at Dec. 31, 2019			42,950,228
Ending balance at Dec. 31, 2019	2,339,773	0	$ 430	1,926,359	393,674	19,310
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	201,209				201,209
Other comprehensive income (loss), net of tax	17,023					17,023
Common stock repurchased (shares)			(112,499)
Common stock repurchased	(5,819)		$ (1)		(5,818)
Restricted stock forfeited (in shares)			(10,915)
Restricted stock forfeited	0
Restricted stock granted (in shares)			310,290
Restricted stock granted	0		$ 2	(2)
Stock based compensation expense	8,450			8,450
Cash dividends ($0.54, $1.00 and $1.05 per share as of December 31, 2018, 2019 and 2020, respectively)	(45,265)				(45,265)
Ending balance (in shares) at Dec. 31, 2020			43,137,104
Ending balance at Dec. 31, 2020	$ 2,515,371	$ 0	$ 431	$ 1,934,807	$ 543,800	$ 36,333

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 201,209	$ 192,736	$ 128,259
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation expense	12,728	11,783	8,391
Accretion of income recognized on acquired loans	(30,378)	(46,071)	(13,523)
Amortization of other intangibles assets	12,671	12,880	5,739
Amortization of premium on securities, net	2,892	2,671	3,316
Amortization of discount and origination costs on borrowings	720	633	633
Stock based compensation expense	8,450	7,808	6,062
Excess tax expense (benefit) on restricted stock vested	243	21	(646)
FHLB stock dividends	(567)	(854)	(791)
(Gain) loss on sale and disposal of premises and equipment	(370)	585	(123)
Gain on sale of loans	(356)	(6,779)	0
Gain on sale of branch	0	(1,549)	0
Gain on sale of trust business	0	(1,319)	0
(Gain) loss on sale of securities available for sale	(382)	(275)	581
Loss (gain) on sale of other real estate owned	36	(875)	(269)
Impairment of other real estate	784	1,801	85
Impairment of other assets	462	1,173	0
Deferred tax (benefit) expense	(1,633)	14,102	1,937
Provision for loan losses	42,993	14,805	9,860
Increase in cash surrender value of BOLI	(5,347)	(5,525)	(3,170)
Net gain on mortgage loans held for sale	(38,175)	(15,133)	(13,794)
Originations of loans held for sale	(901,163)	(435,076)	(384,178)
Proceeds from sale of loans held for sale	892,336	447,291	404,447
Net change in other assets	(35,025)	(5,878)	(14,352)
Net change in other liabilities	(7,833)	(15,636)	20,277
Net cash provided by operating activities	154,295	173,319	158,741
Cash flows from investing activities:
Proceeds from maturities, calls and pay downs of securities available for sale	5,507,844	5,400,634	3,660,624
Proceeds from sale of securities available for sale	13,862	192,417	102,647
Purchases of securities available for sale	(5,570,815)	(5,390,543)	(3,674,396)
Purchases of certificates of deposit held in other banks	0	(5,705)	0
Proceeds from maturities of certificates of deposit held in other banks	1,237	1,473	11,760
Proceeds from surrender of bank owned life insurance contracts	0	802	0
Purchase of bank owned life insurance contracts	0	0	(5,000)
Purchases of FHLB stock and other restricted stock	(27,037)	(9,397)	(6,144)
Proceeds from redemptions of FHLB stock and other restricted stock	37,351	34,863	12,606
Proceeds from sale of loans	19,181	90,025	0
Net loans originated held for investment	(674,142)	(469,023)	(746,804)
Originations of mortgage warehouse purchase loans	(25,833,339)	(12,835,522)	(5,128,767)
Proceeds from pay-offs of mortgage warehouse purchase loans	25,066,859	12,318,495	5,123,171
Additions to premises and equipment	(21,135)	(31,680)	(38,110)
Proceeds from sale of premises and equipment	2,022	2,100	14,479
Proceeds from sale of other real estate owned	6,724	8,207	3,520
Cash acquired in connection with acquisition	0	39,913	44,723
Cash paid in connection with acquisition	0	(9)	(31,016)
Selling costs paid in connection with branch sale	0	(144)	0
Net cash transferred in branch sale	0	(25,163)	0
Proceeds from sale of trust business	0	4,269	0
Net cash used in investing activities	(1,471,388)	(673,988)	(656,707)
Cash flows from financing activities:
Net increase in demand deposits, money market and savings accounts	2,871,869	876,842	363,003
Net (decrease) increase in time deposits	(414,278)	237,136	148,891
Repayments of FHLB advances	(1,550,000)	(1,807,653)	(1,985,667)
Proceeds from FHLB advances	1,600,000	1,700,000	1,685,000
Proceeds from other borrowings	156,489	65,000	0
Repayments of other borrowings	(47,086)	(40,500)	0
Proceeds from exercise of common stock warrants	0	0	2,533
Offering costs paid in connection with acquired bank	0	(804)	(209)
Repurchase of common stock	(5,819)	(51,659)	0
Dividends paid	(45,265)	(43,302)	(15,908)
Net cash provided by (used in) financing activities	2,565,910	935,060	197,643
Net change in cash and cash equivalents	1,248,817	434,391	(300,323)
Cash and cash equivalents at beginning of period	565,170	130,779	431,102
Cash and cash equivalents at end of period	$ 1,813,987	$ 565,170	$ 130,779

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Stock issued for acquisition of bank, net of offering costs		$ 804	$ 209
Cash dividends paid (usd per share)	$ 1.05	$ 1	$ 0.54
Preferred stock par value (in usd per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Preferred stock shares authorized (shares)	10,000,000	10,000,000	10,000,000	10,000,000
Common stock, par value (usd per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Common stock shares authorized (shares)	100,000,000	100,000,000	100,000,000	100,000,000

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Nature of operations: Independent Bank Group, Inc. (IBG) through its subsidiary, Independent Bank, a Texas state banking corporation, doing business as Independent Financial (Bank) (collectively known as the Company), provides a full range of banking services to individual and corporate customers in the North, Central and Southeast, Texas areas and along the Colorado Front Range, through its various branch locations in those areas. The Company is engaged in traditional community banking activities, which include commercial and retail lending, deposit gathering, investment and liquidity management activities. The Company’s primary deposit products are demand deposits, money market accounts and certificates of deposit, and its primary lending products are commercial business and real estate, real estate mortgage and consumer loans. On January 1, 2019, the Company acquired Guaranty Bancorp (Guaranty) and its wholly owned subsidiary, Guaranty Bank and Trust Company (Guaranty Bank) and its wholly owned subsidiary, Private Capital Management, LLC. Guaranty was merged into the Company and dissolved and Guaranty Bank and its subsidiary was merged with the Bank as of acquisition date. The Company also acquired two statutory business trusts in connection with the acquisition as disclosed in Note 12, Junior Subordinated Debentures . See Note 22, Business Combinations , for more details of the Guaranty acquisition. Basis of presentation: The accompanying consolidated financial statements include the accounts of IBG and all other entities in which IBG has controlling financial interest. All material intercompany transactions and balances have been eliminated in consolidation. In addition, the Company wholly-owns nine statutory business trusts that were formed for the purpose of issuing trust preferred securities and do not meet the criteria for consolidation (See Note 12, Junior Subordinated Debentures ). Accounting standards codification: The Financial Accounting Standards Board's (FASB) Accounting Standards Codification (ASC) is the officially recognized source of authoritative U.S. generally accepted accounting principles (GAAP) applicable to all public and non-public non-governmental entities. Rules and interpretive releases of the SEC under the authority of federal securities laws are also sources of authoritative GAAP for SEC registrants. All other accounting literature is considered non-authoritative. Citing particular content in the ASC involves specifying the unique numeric path to the content through the Topic, Subtopic, Section and Paragraph structure. Segment reporting: The Company has one reportable segment. The Company’s chief operating decision-maker uses consolidated results to make operating and strategic decisions. Reclassifications: Certain prior period financial statement and disclosure amounts have been reclassified to conform to current period presentation. The reclassifications have no effect on net income or stockholders' equity as previously reported. Use of estimates: The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect certain reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Accordingly, actual results could differ from those estimates. The material estimates included in the financial statements relate to the allowance for loan losses, the valuation of goodwill and valuation of assets and liabilities acquired in business combinations. Cash and cash equivalents: For the purposes of reporting cash flows, cash and cash equivalents include cash on hand, amounts due from banks and federal funds sold. All highly liquid investments with an initial maturity of less than ninety days are considered to be cash equivalents. The Company maintains deposits with other financial institutions in amounts that exceed FDIC insurance coverage. The Company's management monitors the balance in these accounts and periodically assesses the financial condition of the other financial institutions. The Company has not experienced any losses in such accounts and believes it is not exposed to any significant credit risks on cash or cash equivalents. Certificates of deposit: Certificates of deposit are FDIC insured deposits in other financial institutions that mature within 18 months and are carried at cost. Securities: Securities classified as available for sale are those debt securities that the Company intends to hold for an indefinite period of time, but not necessarily to maturity. Any decision to sell a security classified as available for sale would be based on various factors, including significant movements in interest rates, changes in the maturity mix of the Company's assets and liabilities, liquidity needs, regulatory capital considerations and other similar factors. Securities available for sale are reported at fair value with unrealized gains or losses reported as a separate component of other comprehensive income, net of tax. The amortization of premiums and accretion of discounts, computed by the interest method generally over their contractual lives, are recognized in interest income. Premiums on callable securities are amortized to their earliest call date. Prior to the adoption of a new accounting standard in 2019, as further discussed in Note 2, Recent Accounting Pronouncements , premiums on callable securities were amortized to their respective maturity dates unless such securities were included in pools for the purposes of assessing prepayment expectations. Realized gains or losses, determined on the basis of the cost of specific securities sold, are included in earnings on the trade date. In estimating other than temporary impairment losses, management considers (1) the length of time and the extent to which the fair value has been less than cost, (2) the financial condition and near-term prospects of the issuer, and (3) the intent of the Company to retain its investment and whether it is more likely than not the Company will be required to sell its investment before its anticipated recovery in fair value. When the Company does not intend to sell the security, and it is more likely than not that it will not have to sell the security before recovery of its cost basis, it will recognize the credit component of an other than temporary impairment of a debt security in earnings and the remaining portion in other comprehensive income. Loans held for sale: The Company originates residential mortgage loans that may subsequently be sold to unaffiliated third parties. The Company elected the fair value option for certain residential mortgage loans held for sale originated after July 1, 2018 in accordance with ASC 825, Financial Instruments. This election allows for a more effective offset of the changes in fair values of the loans and the derivative instruments used to economically hedge them without the burden of complying with the requirements for hedge accounting under ASC 815, Derivatives and Hedging . The Company has not elected the fair value option for other residential mortgage loans held for sale primarily because they are not economically hedged using derivative instruments. Mortgage loans originated and intended for sale not recorded under the fair value option are carried at the lower of aggregate cost or fair value, as determined by aggregate outstanding commitments from investors. Net unrealized losses, if any, are recognized through a valuation allowance by charges to income. All mortgage loans held for sale are sold without servicing rights retained. Gains and losses on sales of loans are recognized in noninterest income at settlement dates and are determined by the difference between the sales proceeds and the carrying value of the loans. Acquired loans: Acquired loans from the transactions accounted for as a business combination include both nonperforming loans with evidence of credit deterioration since their origination date and performing loans. The Company is accounting for the nonperforming loans acquired in accordance with ASC 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality . The performing loans are being accounted for under ASC 310-20, Nonrefundable Fees and Other Costs , with the related difference in the initial fair value and unpaid principal balance (the discount) recognized as interest income on a level yield basis over the life of the loan. At the date of the acquisition, the acquired loans are recorded at their fair value with no valuation allowance. Purchased credit impaired loans are accounted for individually or aggregated into pools of loans based on common risk. The Company estimates the amount and timing of undiscounted expected cash flows for each loan, and the expected cash flows in excess of fair value is recorded as interest income over the remaining life of the loan (accretable yield). The excess of the loan's contractual principal and interest over expected cash flows is not recorded (nonaccretable difference). Over the life of the loan, expected cash flows continue to be estimated. If the expected cash flows decrease, an impairment loss is recorded. If the expected cash flows increase, it is recognized as part of future interest income. Loans, net: Loans that management has the intent and ability to hold for the foreseeable future or until maturity or pay-off are reported at their outstanding principal balance, net of unearned interest, purchase premiums and discounts, deferred loan fees or costs and an allowance for loan losses. Loan origination fees, net of direct origination costs, are deferred and recognized as an adjustment to the related loan yield using the effective interest method without anticipating prepayments. Prior to the year ended December 31, 2019, fees and costs associated with originating loans were generally recognized in the period they were incurred. Management believes that not deferring such fees and costs did not materially affect the financial position or results of operations of the Company. Allowance for loan losses: The allowance for loan losses is maintained at a level considered adequate by management to provide for probable loan losses. The allowance is increased by provisions charged to expense. Loans are charged against the allowance for loan losses when management believes that collectability of the principal is unlikely. Subsequent recoveries, if any, are credited to the allowance. The provision for loan losses is the amount, which, in the judgment of management, is necessary to establish the allowance for loan losses at a level that is adequate to absorb known and inherent risks in the loan portfolio. See Note 6, Loans, Net and Allowance for Loan Losses , for further information on the Company's policies and methodology used to estimate the allowance for loan losses. Premises and equipment, net: Land is carried at cost. Bank premises, furniture and equipment and aircraft are carried at cost, less accumulated depreciation computed principally by the straight-line method over the estimated useful lives of the assets, which range from three Leasehold improvements are carried at cost and are depreciated over the shorter of the estimated useful life or the lease period. Software: Costs incurred in connection with development or purchase of internal use software and cloud computing arrangements, including in-substance software licenses, are capitalized. Amortization is computed on a straight-line basis over the estimated useful life of the asset, which generally ranges from one Leases: On January 1, 2019, the Company adopted ASU 2016-02, Leases (Topic 842), as further explained below and in Note 2, Recent Accounting Pronouncements . For operating leases with a term greater than one year, the Company recognizes operating right-of-use (ROU) lease assets and operating lease liabilities, which are recorded in other assets and other liabilities, respectively, in the consolidated balance sheets. The Company determines if an arrangement is a lease at inception. Operating ROU lease assets and related liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As the Company's leases do not provide an implicit rate, the Company uses its incremental borrowing rate referenced to the Federal Home Loan Bank Secure Connect advance rates for borrowings of similar terms in determining the present value of lease payments. The operating ROU lease asset also includes any lease pre-payments made and excludes lease incentives. The Company's lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company has lease agreements with lease and non-lease components, which the Company has elected to account for separately as the non-lease component amounts are readily determinable under most leases. Long-term assets: Premises and equipment and other long-term assets are reviewed for impairment when events indicate that their carrying amount may not be recoverable from future undiscounted cash flows. If impaired, the assets are recorded at fair value. Other real estate owned: Real estate properties acquired through, or in lieu of, loan foreclosure are initially recorded at fair value less estimated selling costs at the date of foreclosure, establishing a new cost basis. After foreclosure, valuations are periodically performed by management and the real estate is carried at the lower of carrying amount or fair value less cost to sell. Revenue and expenses from operations of other real estate owned and impairment charges on other real estate are included in noninterest expense. Gains and losses on sale of other real estate are included in noninterest income. Goodwill and other intangible assets, net: Goodwill represents the excess of costs over fair value of net assets of businesses acquired. Goodwill is tested for impairment annually on December 31 or on an interim basis if an event triggering impairment may have occurred. On January 1, 2020, ASU 2017-04, Intangibles - Goodwill and Other (Topic 350) - Simplifying the Test for Goodwill Impairment became effective for the Company as further explained in Note 2, Recent Accounting Pronouncements . Under the new guidance, if a reporting unit’s carrying amount exceeds its fair value, an entity will record an impairment charge based on that difference. During the period ended March 31, 2020, the economic turmoil and market volatility resulting from the COVID-19 crisis resulted in a substantial decrease in the Company's stock price and market capitalization. Management believed such decrease was a triggering indicator requiring an interim goodwill impairment quantitative analysis. Under the new simplified guidance, the Company's estimated fair value to a market participant as of March 31, 2020, exceeded its carrying amount resulting in no impairment charge for the period. Over subsequent periods, the Company's stock price and market capitalization has continued to increase and management's future projections have not materially changed. As of December 31, 2020, the fair value of the Company’s stock price and calculated market capitalization exceeds its carrying value. Core deposit intangibles and other acquired customer relationship intangibles arising from bank acquisitions are amortized on a straight-line basis over their estimated useful lives of ten years and thirteen years, respectively. Other intangible assets are tested for impairment whenever events or changes in circumstances indicate the carrying amount of the assets may not be recoverable from future undiscounted cash flows. Restricted stock : The Bank is a member of the FHLB system. Members are required to own a certain amount of stock based on the level of borrowings and other factors, and may invest in additional amounts. FHLB of Dallas and other restricted stock do not have readily determinable fair values as ownership is restricted and they lack a ready market. As a result, these stocks are carried at cost and evaluated periodically by management for impairment. Both cash and stock dividends are reported as income. Bank-owned life insurance: Bank-owned life insurance is recorded at the amount that can be realized under the insurance contracts at the balance sheet date, which is the cash surrender value adjusted for other charges or other amounts due that are probable at settlement. Changes in the net cash surrender value of the policies, as well as insurance proceeds received are reflected in noninterest income. Income taxes: Income tax expense is the total of the current year income tax due or refundable and the change in deferred tax assets and liabilities (excluding deferred tax assets and liabilities related to business combinations or components of other comprehensive income). Deferred tax assets and liabilities are the expected future tax amounts for the temporary differences between carrying amounts and tax bases of assets and liabilities, computed using enacted tax rates. The effect of a change in tax rates on deferred assets and liabilities is recognized in income taxes during the period that includes the enactment date. A valuation allowance, if needed, reduces deferred tax assets to the expected amount more likely than not to be realized. Realization of deferred tax assets is dependent upon the level of historical income, prudent and feasible tax planning strategies, reversals of deferred tax liabilities and estimates of future taxable income. The Company evaluates uncertain tax positions at the end of each reporting period. The Company may recognize the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefit recognized in the financial statements from any such position is measured based on the largest benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. For tax positions not meeting the "more likely than not" test, no tax benefit is recorded. Any interest and/or penalties related to income taxes are reported as a component of income tax expense. Loan commitments and related financial instruments: In the ordinary course of business, the Company has entered into certain off-balance-sheet financial instruments consisting of commitments to extend credit, commercial letters of credit, and standby letters of credit. Such financial instruments are recorded in the financial statements when they are funded or related fees are incurred or received. Management estimates losses on off-balance-sheet financial instruments using the same methodology as for portfolio loans. Estimated losses on off-balance-sheet financial instruments are recorded by charges to the provision for losses and credits to other liabilities in the Company's consolidated balance sheet. There were no estimated losses on off-balance sheet financial instruments as of December 31, 2020 or 2019. Stock based compensation: Compensation cost is recognized for restricted stock awards/stock units issued to employees based on the market price of the Company's common stock on the grant date. Stock-based compensation expense is generally recognized using the straight-line method over the requisite service period for time-based awards. Compensation expense for performance stock units is recognized over the service period of the award based upon the probable number of units expected to vest. The impact of forfeitures of stock-based payment awards on compensation expense is recognized as forfeitures occur. Transfers of financial assets: Transfers of financial assets are accounted for as sales, when control over the assets has been relinquished. Control over transferred assets is deemed to be surrendered when the assets have been isolated from the Company, the transferee obtains the right (free of conditions that constrain it from taking advantage of that right) to pledge or exchange the transferred assets, and the Company does not maintain effective control over the transferred assets through an agreement to repurchase them before their maturity. Advertising costs: Advertising costs are expensed as incurred. Business combinations: The Company applies the acquisition method of accounting for business combinations. Under the acquisition method, the acquiring entity in a business combination recognizes 100% of the assets acquired and liabilities assumed at their acquisition date fair values. Management utilizes valuation techniques appropriate for the asset or liability being measured in determining these fair values. Any excess of the purchase price over amounts allocated to assets acquired, including identifiable intangible assets, and liabilities assumed is recorded as goodwill. Where amounts allocated to assets acquired and liabilities assumed is greater than the purchase price, a bargain purchase gain is recognized. Adjustments identified during the measurement period are recognized in the reporting period in which the adjustment amounts are determined. Acquisition-related costs are expensed as incurred. Comprehensive income: Accounting principles generally require that recognized revenue, expenses, gains and losses be included in net income. Although certain changes in assets and liabilities, such as unrealized gains and losses on available for sale securities, are reported as a separate component of the equity section of the balance sheet, such items, along with net income, are components of comprehensive income. Gains and losses on available for sale securities are reclassified to net income as the gains or losses are realized upon sale of the securities. The credit component of other than temporary impairment charges are reclassified to net income at the time of the charge. Fair values of financial instruments: Accounting standards define fair value, establish a framework for measuring fair value in U.S. generally accepted accounting principles, and require certain disclosures about fair value measurements (see Note 18, Fair Value Measurements ). In general, fair values of financial instruments are based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon 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. These adjustments may include amounts to reflect counterparty credit quality and the Company's creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time. Derivative financial instruments: The Company enters into certain derivative financial instruments: interest rate lock commitments, forward mortgage-backed securities trades and interest rate swaps. These financial instruments are not designated as hedging instruments and are used for asset and liability management related to the Company's mortgage banking activities and commercial customers' financing needs. All derivatives are carried at fair value in either other assets or other liabilities (see Note 19, Derivative Financial Instruments ) . Mortgage banking: This revenue category reflects the Company's mortgage production revenue, including fees and income derived from mortgages originated with the intent to sell, gains on sales of mortgage loans and the initial and subsequent changes in the fair value of the mortgage derivatives. Interest earned on mortgage loans is recorded in interest income. Revenue recognition: ASC Topic 606, R evenue from Contracts with Customers (ASC 606) , establishes principles for reporting information about the nature, amount, timing and uncertainty of revenue and cash flows arising from the entity's contracts to provide goods or services to customers. The core principle requires an entity to recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration that it expects to be entitled to receive in exchange for those goods or services recognized as performance obligations are satisfied. The majority of the Company's revenue-generating transactions are not subject to ASC 606, including revenue generated from financial instruments, such as loans, letters of credit, and investment securities, as well as revenue related to mortgage banking activities, and BOLI, as these activities are subject to other accounting guidance. Descriptions of revenue-generating activities that are within the scope of ASC 606, and are presented in the accompanying Consolidated Statements of Income as components of noninterest income, are as follows: • Service charges on deposit accounts - these represent general service fees for monthly account maintenance and activity or transaction-based fees and consist of transaction-based revenue, time-based revenue (service period), item-based revenue or some other individual attribute-based revenue. Revenue is recognized when the performance obligation is completed which is generally monthly for account maintenance services or when a transaction has been completed (such as a wire transfer). Payment for such performance obligations are generally received at the time the performance obligations are satisfied. • Investment management and trust - includes income related to providing investment management and trust services to customers under investment management and trust contracts. Also included are fees received from a third party broker-dealer as part of a revenue-sharing agreement for fees earned from customers that are referred to a third party. The investment management fees and referral fees are billed and paid on a quarterly basis and recognized ratably throughout the quarter as performance obligations are satisfied. • Gains/losses on the sale of other real estate owned - generally recognized when the performance obligation is complete which is typically at delivery of control over the property to the buyer at time of each real estate closing. • Other noninterest income - includes the Company's correspondent bank earnings credit, mortgage warehouse purchase program fees, acquired loan recoveries, other deposit fees, and merchant interchange income. The majority of these fees in other noninterest income are not subject to the requirements of ASC 606. The other deposit fees and merchant interchange income are in the scope of ASC 606, and payment for such performance obligations are generally received at the time the performance obligations are satisfied. The Company has made no significant judgments in applying the revenue guidance prescribed in ASC 606 that affect the determination of the amount and timing of revenue from the above-described contracts with customers. Subsequent events: Companies are required to evaluate events and transactions that occur after the balance sheet date but before the date the financial statements are issued. They must recognize in the financial statements the effect of all events or transactions that provide additional evidence of conditions that existed at the balance sheet date, including the estimates inherent in the financial statement preparation process. Entities shall not recognize the impact of events or transactions that provide evidence about conditions that did not exist at the balance sheet date but arose after that date. The Company has evaluated subsequent events through the date of filing these financial statements with the Securities and Exchange Commission (SEC) and noted no subsequent events requiring financial statement recognition or disclosure, except as disclosed in Note 24. Earnings per share: Basic earnings per common share is calculated as net income available to common shareholders divided by the weighted average number of common shares outstanding during the period. The unvested share-based payment awards that contain rights to nonforfeitable dividends are considered participating securities for this calculation. The participating nonvested common stock was not included in dilutive shares as it was anti-dilutive for the years ended December 31, 2020, 2019 and 2018. The following table presents a reconciliation of net income available to common shareholders and the number of shares used in the calculation of basic and diluted earnings per common share. Years Ended December 31, 2020 2019 2018 Basic earnings per share: Net income $ 201,209 $ 192,736 $ 128,259 Less: Undistributed earnings allocated to participating securities 1,311 971 976 Dividends paid on participating securities 380 281 139 Net income available to common shareholders $ 199,518 $ 191,484 $ 127,144 Weighted average basic shares outstanding 42,754,606 42,964,393 29,341,843 Basic earnings per share $ 4.67 $ 4.46 $ 4.33 Diluted earnings per share: Net income available to common shareholders $ 199,518 $ 191,484 $ 127,144 Total weighted average basic shares outstanding 42,754,606 42,964,393 29,341,843 Total weighted average diluted shares outstanding 42,754,606 42,964,393 29,341,843 Diluted earnings per share $ 4.67 $ 4.46 $ 4.33 Anti-dilutive participating securities 58,359 73,546 114,087

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements Adoption of new accounting standards Delayed implementation of new accounting standard: ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments and subsequent updates . ASU 2016-13 requires a new credit loss methodology, the current expected credit loss (CECL) model, which requires the recognition of an allowance for lifetime expected credit losses on loans, held-to-maturity debt securities and other receivables measured at amortized cost at the time the financial asset is originated or acquired. Credit losses will be immediately recognized through net income; the amount recognized will be based on the current estimate of contractual cash flows not expected to be collected over the financial asset’s contractual term. ASU 2016-13 became effective for the Company on January 1, 2020. 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 financial institutions to delay the implementation of ASU 2016-13 until the earlier of the termination date of the national emergency declaration by the President or December 31, 2020. Due to the uncertainty of the economic forecast resulting from the coronavirus (COVID-19) pandemic and the potential impact of the government economic stimulus measures, the Company delayed its implementation of ASU 2016-13. On December 27, 2020, the Consolidated Appropriations Act, 2021 (Act 2021), was signed into law which further extended the implementation date of CECL to the earlier of the first day of the entity’s fiscal year that begins after the date on which the COVID-19 national emergency terminates or January 1, 2022. With regard to Act 2021 amendments, the SEC staff indicated it would not object to a registrant early adopting on December 31, 2020, retrospective to January 1, 2020, or January 1, 2021, effective as of January 1, 2021. Under this guidance, the Company is electing to adopt ASU 2016-13 with an effective implementation date of January 1, 2021. As a result, for 2020, the Company has calculated and recorded its provision for loan losses under the incurred loss model that existed prior to ASU 2016-13. Upon adoption, the Company expects to increase its combined allowance for loan losses and reserves for unfunded commitments by approximately $68,000 to $84,000, of which approximately $13,000 is attributable to purchase credit deteriorated loans. The Company will apply the standard's provisions as a cumulative-effect adjustment to retained earnings. The expected increase in the allowance for loan losses is a result of changing from an incurred loss model, which encompasses allowances for current known and inherent losses within the portfolio, to a CECL model, which encompasses allowances for losses expected to be incurred over the life of the portfolio. The majority of the increase is attributable to applying the CECL model to the Company's acquired loans, which, under prior guidance, were recorded at fair value without an allowance at acquisition date. Furthermore, ASU 2016-13 necessitates that the Company establish an allowance for expected credit losses for certain debt securities and other financial assets; however, such allowances, if any, are not expected to be significant. ASU 2017-04, Intangibles - Goodwill and Other (Topic 350) - Simplifying the Test for Goodwill Impairment. This ASU simplifies the accounting for goodwill impairment for all entities by requiring impairment charges to be based on the first step in today’s two-step impairment test. Under the new guidance, if a reporting unit’s carrying amount exceeds its fair value, an entity will record an impairment charge based on that difference. The impairment charge will be limited to the amount of goodwill allocated to that reporting unit. The standard eliminates today’s requirement to calculate a goodwill impairment charge using Step 2, which requires an entity to calculate any impairment charge by comparing the implied fair value of goodwill with its carrying amount. ASU 2017-04 became effective for the Company on January 1, 2020, and did not have a significant impact on its financial statements. ASU 2018-13, Fair Value Measurement (Topic 820) - Changes to the Disclosure Requirements for Fair Value Measurement. This ASU modifies the disclosure requirements on fair value measurements by requiring that Level 3 fair value disclosures include the range and weighted average of significant unobservable inputs used to develop those fair value measurements. For certain unobservable inputs, an entity may disclose other quantitative information in lieu of the weighted average if the entity determines that other quantitative information would be a more reasonable and rational method to reflect the distribution of unobservable inputs used to develop Level 3 fair value measurements. ASU 2018-13 became effective for the Company on January 1, 2020 and did not have a significant impact on its financial statements and disclosures. ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40) - Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. This ASU aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal use software license). The accounting for the service element of a hosting arrangement that is a service contract is not affected by these amendments. This ASU became effective for the Company on January 1, 2020 and did not have a significant impact on its financial statements and disclosures. ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting and subsequent updates . This ASU provides temporary optional guidance to ease the potential burden in accounting for reference rate reform. The new guidance provides optional expedients and exceptions for applying generally accepted accounting principles to contract modifications and hedging relationships, subject to meeting certain criteria, that reference LIBOR or another reference rate expected to be discontinued. The ASU is intended to help stakeholders during the global market-wide reference rate transition period. This ASU became effective upon issuance and generally can be applied through December 31, 2022. The Company anticipates this ASU will simplify any modifications it executes and is not expected to have a significant impact on its financial statements and disclosures. ASU 2016-02, Leases (Topic 842) and subsequent updates . This ASU, among other things, requires lessees to recognize a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. Under this guidance, lessor accounting is largely unchanged. This ASU became effective for annual and interim periods for the Company on January 1, 2019. The Company adopted the standard by applying the alternative transition method whereby comparative periods were not restated, and an immaterial cumulative effect adjustment to the opening balance of retained earnings was recognized as of January 1, 2019. The Company also elected the ASU’s package of three practical expedients, which allowed the Company to forego a reassessment of (i) whether any expired or existing contracts are or contain leases, (ii) the lease classification for any expired or existing leases and (iii) the initial direct costs for any existing leases. The Company also elected not to apply the recognition requirements of the ASU to any short-term leases (as defined by related accounting guidance) and will account for lease and non-lease components separately. The adoption of this standard resulted in the Company recognizing lease right-of-use assets and related lease liabilities totaling $38,812 and $33,953, respectively, as of January 1, 2019. The difference between the lease assets and the lease liabilities was $4,949 of prepaid rent, which was reclassified to lease assets, and the remainder, net of the deferred tax impact, was recorded as an adjustment reducing retained earnings in the amount of $70. The adoption of this ASU did not have a significant impact on the Company’s consolidated statement of income. See Note 1, Summary of Significant Accounting Policies , and Note 13, Leases , for required disclosures. ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20), Premium Amortization on Purchased Callable Debt Securities . This ASU requires certain premiums on callable debt securities to be amortized to the earliest call date. The amortization period for callable debt securities purchased at a discount is not impacted. Under current GAAP, premiums on callable debt securities are generally amortized over the contractual life of the security. ASU 2017-08 became effective for the Company on January 1, 2019 and, upon adoption, the Company recognized a cumulative effect adjustment reducing retained earnings by $856, net of the deferred tax impact, but otherwise did not have a significant impact to the Company's consolidated financial statements and disclosures. ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. The amendments in this update allow reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act (TCJA) which was signed into law on December 22, 2017. The Company elected to early adopt ASU 2018-02 in the first quarter of 2018 and apply the guidance to the beginning of the period, effective January 1, 2018 . The impact of adopting the amendment resulted in a cumulative effect adjustment to the consolidated balance sheet as of January 1, 2018 to reclassify approximately $233 of tax expense from accumulated other comprehensive loss to retained earnings as reflected in the accompanying Consolidated Statements of Changes in Stockholders' Equity. Newly issued but not yet effective accounting standards ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. The guidance issued in this update simplifies the accounting for income taxes by eliminating certain exceptions to the guidance in ASC 740 related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition for 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 will be effective for the Company on January 1, 2021, with early adoption permitted, and is not expected to have a significant impact on our financial statements.

Restrictions on Cash and Due fr

Restrictions on Cash and Due from Banks	12 Months Ended
	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
Restrictions on Cash and Due From Banks	Restrictions on Cash and Due From BanksOn March 15, 2020, in response to COVID-19 pandemic, the Federal Reserve reduced the reserve requirement ratio to zero effective March 26, 2020 and continuing through December 31, 2020. At December 31, 2019, the Company had a required reserve balance of $63,739 with the Federal Reserve. Additionally, as of December 31, 2020 and 2019, the Company had $23,829 and $4,350, respectively, in cash collateral on deposit with other financial institution counterparties to interest rate swap transactions.

Statement of Cash Flows

Statement of Cash Flows	12 Months Ended
	Dec. 31, 2020
Supplemental Cash Flow Elements [Abstract]
Statement of Cash Flows	Statement of Cash Flows As allowed by the accounting standards, the Company has chosen to report, on a net basis, its cash receipts and cash payments for time deposits accepted and repayments of those deposits, and loans made to customers and principal collections on those loans. The Company uses the indirect method to present cash flows from operating activities. Other supplemental cash flow information is presented below: Years Ended December 31, 2020 2019 2018 Cash transactions: Interest expense paid $ 97,246 $ 144,775 $ 79,509 Income taxes paid $ 54,842 $ 40,504 $ 25,109 Noncash transactions: Transfers of loans to other real estate owned $ 5,239 $ 544 $ 410 Loans to facilitate the sale of other real estate owned $ 2,039 $ 517 $ — Securities purchased, not yet settled $ — $ 9,975 $ — Transfers of loans held for investment to loans held for sale $ — $ 83,526 $ — Right-of-use assets obtained in exchange for lease liabilities $ 105 $ 35,553 $ — Loans purchased, not yet settled $ 9,442 $ — $ — Transfer of bank premises to other real estate $ — $ 7,896 $ — Transfer of repurchase agreements to deposits $ — $ 8,475 $ — Supplemental schedule of noncash investing activities from a branch sale during 2019 is as follows: Year ended December 31, 2019 Noncash assets transferred: Loans, including accrued interest $ 796 Premises and equipment 94 Other assets 2 Total assets $ 892 Noncash liabilities transferred: Deposits, including interest $ 27,721 Other liabilities 27 Total liabilities $ 27,748 Cash and cash equivalents transferred in branch sales $ 206 Deposit premium received $ 1,386 Cash paid to buyer, net of deposit premium $ 24,957 Supplemental schedule of noncash investing activities from sale of trust business during 2019 is as follows: Year ended December 31, 2019 Noncash assets transferred: Customer relationship intangible assets, net $ 2,939 Other assets 11 Total assets $ 2,950 Net cash received from sale $ 4,269 Supplemental schedule of noncash investing activities from acquisitions is as follows: Years ended December 31, 2020 2019 2018 Noncash assets acquired Certificates of deposit held in other banks $ — $ 262 $ — Securities available for sale — 561,052 24,721 Restricted stock — 27,794 3,357 Loans — 2,789,868 651,769 Premises and equipment — 65,786 4,863 Other real estate owned — 1,829 — Goodwill — 272,224 100,339 Other intangible assets — 71,518 7,537 Bank owned life insurance — 80,837 8,181 Other assets — 31,987 6,385 Total assets acquired $ — $ 3,903,157 $ 807,152 Noncash liabilities assumed: Deposits $ — $ 3,108,810 $ 593,078 Repurchase agreements — 8,475 — FHLB advances — 142,653 60,000 Other borrowings — 40,000 — Junior subordinated debentures — 25,774 — Other liabilities — 15,477 10,518 Total liabilities assumed $ — $ 3,341,189 $ 663,596 Cash and cash equivalents acquired from acquisitions $ — $ 39,913 $ 44,723 Cash paid to shareholders of acquired banks $ — $ 9 $ 31,016 Fair value of common stock issued to shareholders of acquired banks $ — $ 601,872 $ 157,263

Securities Available for Sale

Securities Available for Sale	12 Months Ended
	Dec. 31, 2020
Debt Securities, Available-for-sale [Abstract]
Securities Available for Sale	Securities Available for Sale Securities available for sale have been classified in the consolidated balance sheets according to management’s intent. The amortized cost of securities and their approximate fair values at December 31, 2020 and 2019, are as follows: Amortized Gross Gross Fair Securities Available for Sale December 31, 2020 U.S. treasuries $ 43,060 $ 1,648 $ — $ 44,708 Government agency securities 247,764 3,169 (1,916) 249,017 Obligations of state and municipal subdivisions 373,017 20,168 (20) 393,165 Corporate bonds 21,496 608 (2) 22,102 Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 421,916 21,678 (93) 443,501 Other securities 1,200 — — 1,200 $ 1,108,453 $ 47,271 $ (2,031) $ 1,153,693 December 31, 2019 U.S. treasuries $ 48,060 $ 743 $ (7) $ 48,796 Government agency securities 178,953 926 (583) 179,296 Obligations of state and municipal subdivisions 332,715 11,150 (6) 343,859 Corporate bonds 7,011 207 — 7,218 Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 493,915 11,981 (329) 505,567 Other securities 1,200 — — 1,200 $ 1,061,854 $ 25,007 $ (925) $ 1,085,936 Securities with a carrying amount of approximately $738,519 and $571,843 at December 31, 2020 and 2019, respectively, were pledged primarily to secure deposits. Proceeds from sale of securities available for sale and gross gains and gross losses for the years ended December 31, 2020, 2019 and 2018 were as follows: Years Ended December 31, 2020 2019 2018 Proceeds from sale $ 13,862 $ 192,417 $ 102,647 Gross gains $ 385 $ 306 $ 268 Gross losses $ 3 $ 31 $ 849 The amortized cost and estimated fair value of securities available for sale at December 31, 2020, by contractual maturity, are shown below. Maturities of mortgage-backed securities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. December 31, 2020 Securities Available for Sale Amortized Fair Due in one year or less $ 39,579 $ 39,943 Due from one year to five years 128,804 135,272 Due from five to ten years 203,387 209,396 Thereafter 314,767 325,581 686,537 710,192 Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 421,916 443,501 $ 1,108,453 $ 1,153,693 The number of securities, unrealized losses and fair value, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, as of December 31, 2020 and 2019, are summarized as follows: Less Than 12 Months Greater Than 12 Months Total Description of Securities Number of Securities Estimated Unrealized Number of Securities Estimated Unrealized Estimated Unrealized Securities Available for Sale December 31, 2020 Government agency securities 20 $ 112,897 $ (1,916) — $ — $ — $ 112,897 $ (1,916) Obligations of state and municipal subdivisions 2 3,786 (20) — — — 3,786 (20) Corporate bonds 1 998 (2) — — — 998 (2) Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 10 41,344 (93) — — — 41,344 (93) 33 $ 159,025 $ (2,031) — $ — $ — $ 159,025 $ (2,031) December 31, 2019 U.S. treasuries — $ — $ — 2 $ 8,097 $ (7) $ 8,097 $ (7) Government agency securities 13 52,790 (495) 6 15,911 (88) 68,701 (583) Obligations of state and municipal subdivisions 5 2,793 (1) 1 423 (5) 3,216 (6) Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 13 46,512 (317) 1 1,193 (12) 47,705 (329) 31 $ 102,095 $ (813) 10 $ 25,624 $ (112) $ 127,719 $ (925) Unrealized losses are generally due to changes in interest rates. The Company has the intent to hold these securities until maturity or a forecasted recovery and it is more likely than not that the Company will not have to sell the securities before the recovery of their cost basis. As such, the losses are deemed to be temporary.

Loans, Net and Allowance for Lo

Loans, Net and Allowance for Loan Losses	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Loans, Net and Allowance for Loan Losses	Loans, Net and Allowance for Loan Losses Loans, net at December 31, 2020 and 2019, consisted of the following: December 31, 2020 2019 Commercial $ 3,902,266 $ 2,482,356 Real estate: Commercial 6,096,676 5,872,653 Commercial construction, land and land development 1,245,801 1,236,623 Residential 1,352,465 1,515,227 Single-family interim construction 326,575 378,120 Agricultural 85,014 97,767 Consumer 66,952 32,603 Other 346 621 Total loans 13,076,095 11,615,970 Deferred loan fees, net (10,037) (1,695) Allowance for loan losses (87,820) (51,461) Total loans, net $ 12,978,238 $ 11,562,814 The Company has certain lending policies and procedures in place that are designed to maximize loan income within an acceptable level of risk. Management reviews and approves these policies and procedures on a regular basis. A reporting system supplements the review process by providing management with frequent reports related to loan production, loan quality, concentrations of credit, loan delinquencies and nonperforming and potential problem loans. Commercial loans are underwritten after evaluating and understanding the borrower’s ability to operate profitably and prudently expand its business. The Company’s management examines current and projected cash flows to determine the ability of the borrower to repay their obligations as agreed. Commercial loans are primarily made based on the identified cash flows of the borrower and secondarily on the underlying collateral provided by the borrower. These cash flows, however, may not be as expected and the value of collateral securing the loans may fluctuate. Most commercial loans are secured by the assets being financed or other business assets such as accounts receivable or inventory and may incorporate a personal guarantee; however, some short term loans may be made on an unsecured basis. Additionally, our commercial loan portfolio includes loans made to customers in the energy industry, which is a complex, technical and cyclical industry. Experienced bankers with specialized energy lending experience originate our energy loans. Companies in this industry produce, extract, develop, exploit and explore for oil and natural gas. Loans are primarily collateralized with proven producing oil and gas reserves based on a technical evaluation of these reserves. At December 31, 2020 and 2019, there were approximately $205,496 and $189,781 of energy-related loans outstanding, respectively. The Company has a mortgage warehouse purchase program providing mortgage inventory financing for residential mortgage loans originated by mortgage banker clients across a broad geographic scale. Proceeds from the sale of mortgages is the primary source of repayment for warehouse inventory financing via approved investor takeout commitments. These loans typically have a very short duration ranging between a few days to 15 days. In some cases, loans to larger mortgage originators may be financed for up to 60 days. These loans are reported as commercial loans since the loans are secured by notes receivable, not real estate. As of December 31, 2020 and 2019, mortgage warehouse purchase loans outstanding totaled $1,453,797 and $687,317, respectively. With the passage of the CARES Act Paycheck Protection Program (PPP), administered by the Small Business Administration (SBA), the Company has participated in originating loans to its customers through the program. PPP loans have terms of two Commercial real estate loans are subject to underwriting standards and processes similar to commercial loans. These loans are viewed primarily as cash flow loans and secondarily as loans secured by real estate. Commercial real estate lending typically involves higher loan principal amounts and the repayment of these loans is generally largely dependent on the successful operation of the property or the business conducted on the property securing the loan. Commercial real estate loans may be more adversely affected by conditions in the real estate markets or in the general economy. The properties securing the Company’s commercial real estate portfolio are diverse in terms of type and geographic location. Management monitors the diversification of the portfolio on a quarterly basis by type and geographic location. Management also tracks the level of owner-occupied property versus non owner-occupied property. At December 31, 2020, the portfolio consisted of approximately 29% of owner-occupied property. Land and commercial land development loans are underwritten using feasibility studies, independent appraisal reviews and financial analysis of the developers or property owners. Generally, borrowers must have a proven track record of success. Commercial construction loans are generally based upon estimates of cost and value of the completed project. These estimates may not be accurate. Commercial construction loans often involve the disbursement of substantial funds with the repayment dependent on the success of the ultimate project. Sources of repayment for these loans may be pre-committed permanent financing or sale of the developed property. The loans in this portfolio are geographically diverse and due to the increased risk are monitored closely by management and the board of directors on a quarterly basis. Residential real estate and single-family interim construction loans are underwritten primarily based on borrowers’ credit scores, documented income and minimum collateral values. Relatively small loan amounts are spread across many individual borrowers which minimizes risk in the residential portfolio. In addition, management evaluates trends in past dues and current economic factors on a regular basis. Agricultural loans are collateralized by real estate and/or agricultural-related assets. Agricultural real estate loans are primarily comprised of loans for the purchase of farmland. Loan-to-value ratios on loans secured by farmland generally do not exceed 80% and have amortization periods limited to twenty years. Agricultural non-real estate loans are generally comprised of term loans to fund the purchase of equipment, livestock and seasonal operating lines to grain farmers to plant and harvest corn and soybeans. Specific underwriting standards have been established for agricultural-related loans including the establishment of projections for each operating year based on industry developed estimates of farm input costs and expected commodity yields and prices. Operating lines are typically written for one year and secured by the crop and other farm assets as considered necessary. Agricultural loans carry significant credit risks as they involve larger balances concentrated with single borrowers or groups of related borrowers. In addition, repayment of such loans depends on the successful operation or management of the farm property securing the loan or for which an operating loan is utilized. Farming operations may be affected by adverse weather conditions such as drought, hail or floods that can severely limit crop yields. Consumer loans represent less than 1% of the outstanding total loan portfolio. Collateral consists primarily of automobiles and other personal assets. Credit score analysis is used to supplement the underwriting process. Most of the Company’s lending activity occurs within the State of Texas, primarily in the north, central and southeast Texas regions and the State of Colorado, specifically along the Front Range area. As of December 31, 2020, loans in the Colorado region represented about 24% of the total portfolio. A large percentage of the Company’s portfolio consists of commercial and residential real estate loans. As of December 31, 2020 and 2019, there were no concentrations of loans related to a single industry in excess of 10% of total loans. The allowance for loan losses is an amount that management believes will be adequate to absorb estimated losses relating to specifically identified loans, as well as probable credit losses inherent in the balance of the loan portfolio. The allowance is derived from the following two components: 1) allowances established on individual impaired loans, which are based on a review of the individual characteristics of each loan, including the customer’s ability to repay the loan, the underlying collateral values and the industry the customer operates and 2) allowances based on actual historical loss experience for the last three years for similar types of loans in the Company’s loan portfolio adjusted for primarily changes in the lending policies and procedures; collection, charge-off and recovery practices; nature and volume of the loan portfolio; change in value of underlying collateral; volume and severity of nonperforming loans; existence and effect of any concentrations of credit and the level of such concentrations and current, national and local economic and business conditions. This second component also includes an unallocated allowance to cover uncertainties that could affect management’s estimate of probable losses. The unallocated allowance reflects the imprecision inherent in the underlying assumptions used in the methodologies for estimating this component. The Company’s management continually evaluates the allowance for loan losses determined from the allowances established on individual loans and the amounts determined from historical loss percentages adjusted for the qualitative factors above. Should any of the factors considered by management change, the Company’s estimate of loan losses could also change and would affect the level of future provision expense. While the calculation of the allowance for loan losses utilizes management’s best judgment and all the information available, the adequacy of the allowance for loan losses is dependent on a variety of factors beyond the Company’s control, including, among other things, the performance of the entire loan portfolio, the economy, changes in interest rates and the view of regulatory authorities towards loan classifications. In addition, regulatory agencies, as an integral part of their examination process, periodically review the Bank’s allowance for loan losses, and may require the Bank to make additions to the allowance based on their judgment about information available to them at the time of their examinations. Loans requiring an allocated loan loss provision are generally identified at the servicing officer level based on review of weekly past due reports and/or the loan officer’s communication with borrowers. In addition, the status of past due loans are routinely discussed within each lending region as well as credit committee meetings to determine if classification is warranted. The Company’s internal loan review department has implemented an internal risk based loan review process to identify potential internally classified loans that supplements the independent external loan review. External loan reviews cover a wide range of the loan portfolio, including large lending relationships and recently acquired loan portfolios. As such, the external loan review generally covers loans exceeding $3,500. These reviews include analysis of borrower’s financial condition, payment histories and collateral values to determine if a loan should be internally classified. Generally, once classified, an impaired loan analysis is completed by the credit department to determine if the loan is impaired and the amount of allocated allowance required. Following unprecedented declines caused by the pandemic and volatile energy prices, the Texas economy, specifically in the Company’s lending areas of north, central and southeast Texas, and the Colorado economy expanded at a moderate pace by the end of the fourth quarter of 2020. Activity in the manufacturing and service sectors picked up while the retail sector activity remained weak. Energy activity showed mounting signs of improvement after a prolonged contraction. Loan volume increased during the year, driven by a sharp rise in residential real estate lending. Loan pricing fell further, and credit standards and terms continue to tighten with expectations for future loan demand turning slightly negative. Outlooks are generally positive, but uncertainty remains high with continued concerns about rising COVID-19 infection rates impacting the overall economic recovery mitigated slightly by optimism about the vaccine paving the way to a resumption of normal economic activity in 2021. The pandemic crisis has been impactful and the timing and magnitude of recovery cannot be predicted. The risk of loss associated with all segments of the portfolio could increase due to these factors. The economy and other risk factors are minimized by the Company’s underwriting standards which include the following principles: 1) financial strength of the borrower including strong earnings, high net worth, significant liquidity and acceptable debt to worth ratio, 2) managerial business competence, 3) ability to repay, 4) loan to value, 5) projected cash flow and 6) guarantor financial statements as applicable. The following is a summary of the activity in the allowance for loan losses by loan class for the years ended December 31, 2020, 2019 and 2018: Commercial Commercial Residential Single-Family Agricultural Consumer Other Unallocated Total Year ended December 31, 2020 Balance at beginning of year $ 12,844 $ 33,085 $ 3,678 $ 1,606 $ 332 $ 226 $ 5 $ (315) $ 51,461 Provision for loan losses 20,025 17,769 3,108 632 5 223 493 738 42,993 Charge-offs (5,670) (735) — (82) — (44) (342) — (6,873) Recoveries 112 4 — — — 37 86 — 239 Balance at end of year $ 27,311 $ 50,123 $ 6,786 $ 2,156 $ 337 $ 442 $ 242 $ 423 $ 87,820 Year ended December 31, 2019 Balance at beginning of year $ 11,793 $ 27,795 $ 3,320 $ 1,402 $ 241 $ 186 $ 3 $ 62 $ 44,802 Provision for loan losses 8,670 5,289 498 207 91 71 356 (377) 14,805 Charge-offs (7,709) (3) (140) (3) — (79) (430) — (8,364) Recoveries 90 4 — — — 48 76 — 218 Balance at end of year $ 12,844 $ 33,085 $ 3,678 $ 1,606 $ 332 $ 226 $ 5 $ (315) $ 51,461 Year ended December 31, 2018 Balance at beginning of year $ 10,599 $ 23,301 $ 3,447 $ 1,583 $ 250 $ 205 $ (32) $ 49 $ 39,402 Provision for loan losses 4,973 4,909 (124) (181) (9) 69 210 13 9,860 Charge-offs (3,863) (435) (6) — — (93) (228) — (4,625) Recoveries 84 20 3 — — 5 53 — 165 Balance at end of year $ 11,793 $ 27,795 $ 3,320 $ 1,402 $ 241 $ 186 $ 3 $ 62 $ 44,802 The following table details the amount of the allowance for loan losses and recorded investment in loans by class as of December 31, 2020 and 2019: Commercial Commercial Residential Single-Family Agricultural Consumer Other Unallocated Total December 31, 2020 Allowance for losses: Individually evaluated for impairment $ 8,281 $ 243 $ — $ — $ — $ — $ — $ — $ 8,524 Collectively evaluated for impairment 18,836 49,880 6,786 2,156 337 442 242 423 79,102 Loans acquired with deteriorated credit quality 194 — — — — — — — 194 Ending balance $ 27,311 $ 50,123 $ 6,786 $ 2,156 $ 337 $ 442 $ 242 $ 423 $ 87,820 Loans: Individually evaluated for impairment $ 39,298 $ 21,880 $ 2,550 $ — $ 613 $ 42 $ — $ — $ 64,383 Collectively evaluated for impairment 3,823,982 7,149,610 1,345,234 326,575 84,284 66,895 346 — 12,796,926 Acquired with deteriorated credit quality 38,986 170,987 4,681 — 117 15 — — 214,786 Ending balance $ 3,902,266 $ 7,342,477 $ 1,352,465 $ 326,575 $ 85,014 $ 66,952 $ 346 $ — $ 13,076,095 December 31, 2019 Allowance for losses: Individually evaluated for impairment $ 357 $ — $ — $ — $ — $ 1 $ — $ — $ 358 Collectively evaluated for impairment 12,108 32,615 3,678 1,606 332 225 5 (315) 50,254 Loans acquired with deteriorated credit quality 379 470 — — — — — — 849 Ending balance $ 12,844 $ 33,085 $ 3,678 $ 1,606 $ 332 $ 226 $ 5 $ (315) $ 51,461 Loans: Individually evaluated for impairment $ 3,130 $ 6,813 $ 2,008 $ — $ 114 $ 22 $ — $ — $ 12,087 Collectively evaluated for impairment 2,416,569 6,883,639 1,505,896 378,120 93,837 32,556 621 — 11,311,238 Acquired with deteriorated credit quality 62,657 218,824 7,323 — 3,816 25 — — 292,645 Ending balance $ 2,482,356 $ 7,109,276 $ 1,515,227 $ 378,120 $ 97,767 $ 32,603 $ 621 $ — $ 11,615,970 Nonperforming loans by loan class (excluding loans acquired with deteriorated credit quality) at December 31, 2020 and 2019, are summarized as follows: Commercial Commercial Residential Real Estate Single-Family Agricultural Consumer Other Total December 31, 2020 Nonaccrual loans $ 25,898 $ 20,072 $ 2,372 $ — $ 613 $ 42 $ — $ 48,997 Loans past due 90 days and still accruing 433 — — — — — — 433 Troubled debt restructurings (not included in nonaccrual or loans past due and still accruing) — 1,808 178 — — — — 1,986 $ 26,331 $ 21,880 $ 2,550 $ — $ 613 $ 42 $ — $ 51,416 December 31, 2019 Nonaccrual loans $ 3,130 $ 6,461 $ 1,820 $ — $ 114 $ 22 $ — $ 11,547 Loans past due 90 days and still accruing 14,529 — — — — — — 14,529 Troubled debt restructurings (not included in nonaccrual or loans past due and still accruing) — 352 188 — — — — 540 $ 17,659 $ 6,813 $ 2,008 $ — $ 114 $ 22 $ — $ 26,616 The accrual of interest is discontinued on a loan when management believes that, after considering collection efforts and other factors, the borrower's financial condition is such that collection of interest is doubtful. All interest accrued but not collected for loans that are placed on nonaccrual status or charged-off is reversed against interest income. Cash collections on nonaccrual loans are generally credited to the loan receivable balance, and no interest income is recognized on those loans until the principal balance has been collected. Loans are returned to accrual status when all the principal and interest amounts contractually due are brought current and future payments are reasonably assured. Impaired loans are those loans where it is probable that all amounts due according to contractual terms of the loan agreement will not be collected. The Company has identified these loans through its normal loan review procedures. Impaired loans are measured based on 1) the present value of expected future cash flows discounted at the loan's effective interest rate; 2) the loan's observable market price; or 3) the fair value of collateral if the loan is collateral dependent. Substantially all of the Company’s impaired loans are measured at the fair value of the collateral. In limited cases, the Company may use other methods to determine the level of impairment of a loan if such loan is not collateral dependent. All commercial, real estate, agricultural loans and troubled debt restructurings are considered for individual impairment analysis. Smaller balance consumer loans are collectively evaluated for impairment. Impaired loans by loan class (excluding loans acquired with deteriorated credit quality) at December 31, 2020 and 2019 and for the years ended December 31, 2020, 2019 and 2018, are summarized as follows: Commercial Commercial Residential Single-Family Agricultural Consumer Other Total December 31, 2020 Recorded investment in impaired loans: Impaired loans with an allowance for loan losses $ 24,540 $ 475 $ — $ — $ — $ — $ — $ 25,015 Impaired loans with no allowance for loan losses 14,758 21,405 2,550 — 613 42 — 39,368 Total $ 39,298 $ 21,880 $ 2,550 $ — $ 613 $ 42 $ — $ 64,383 Unpaid principal balance of impaired loans $ 63,817 $ 22,543 $ 2,742 $ — $ 650 $ 44 $ — $ 89,796 Allowance for loan losses on impaired loans $ 8,281 $ 243 $ — $ — $ — $ — $ — $ 8,524 December 31, 2019 Recorded investment in impaired loans: Impaired loans with an allowance for loan losses $ 1,580 $ — $ — $ — $ — $ 1 $ — $ 1,581 Impaired loans with no allowance for loan losses 1,550 6,813 2,008 — 114 21 — 10,506 Total $ 3,130 $ 6,813 $ 2,008 $ — $ 114 $ 22 $ — $ 12,087 Unpaid principal balance of impaired loans $ 8,580 $ 6,967 $ 2,197 $ — $ 123 $ 24 $ — $ 17,891 Allowance for loan losses on impaired loans $ 357 $ — $ — $ — $ — $ 1 $ — $ 358 For the year ended December 31, 2020 Average recorded investment in impaired loans $ 21,559 $ 9,497 $ 2,362 $ — $ 442 $ 30 $ — $ 33,890 Interest income recognized on impaired loans $ 168 $ 139 $ 208 $ — $ — $ — $ — $ 515 For the year ended December 31, 2019 Average recorded investment in impaired loans $ 6,266 $ 3,979 $ 1,746 $ 716 $ 57 $ 30 $ — $ 12,794 Interest income recognized on impaired loans $ 30 $ 39 $ 39 $ 119 $ — $ 6 $ — $ 233 For the year ended December 31, 2018 Average recorded investment in impaired loans $ 8,919 $ 2,667 $ 2,033 $ 716 $ — $ 46 $ — $ 14,381 Interest income recognized on impaired loans $ 119 $ 65 $ 81 $ 1 $ — $ 2 $ — $ 268 Certain impaired loans have adequate collateral and do not require a related allowance for loan loss. The Company will charge-off that portion of any loan which management considers a loss. Commercial and real estate loans are generally considered for charge-off when exposure beyond collateral coverage is apparent and when no further collection of the loss portion is anticipated based on the borrower’s financial condition. The restructuring of a loan is considered a “troubled debt restructuring” (TDR) if both 1) the borrower is experiencing financial difficulties and 2) the creditor has granted a concession. Concessions may include interest rate reductions or below market interest rates, principal forgiveness, extending amortization and other actions intended to minimize potential losses. A TDR loan is identified as impaired and measured for credit impairment as of each reporting period in accordance with the guidance in Accounting Standards Codification ASC 310-10-35. Modifications primarily relate to extending the amortization periods of the loans and interest rate concessions. The majority of these loans were identified as impaired prior to restructuring; therefore, the modifications did not materially impact the Company’s determination of the allowance for loan losses. The recorded investment in troubled debt restructurings, including those on nonaccrual, was $2,564 and $1,208 as of December 31, 2020 and 2019, respectively. Following is a summary of loans modified under troubled debt restructurings during the years ended December 31, 2020 and 2019: Commercial Commercial Residential Single-Family Agricultural Consumer Other Total Troubled debt restructurings during the year ended December 31, 2020 Number of contracts — 1 — — — — — 1 Pre-restructuring outstanding recorded investment $ — $ 1,517 $ — $ — $ — $ — $ — $ 1,517 Post-restructuring outstanding recorded investment $ — $ 1,517 $ — $ — $ — $ — $ — $ 1,517 Troubled debt restructurings during the year ended December 31, 2019 Number of contracts — — 1 — — — — 1 Pre-restructuring outstanding recorded investment $ — $ — $ 29 $ — $ — $ — $ — $ 29 Post-restructuring outstanding recorded investment $ — $ — $ 29 $ — $ — $ — $ — $ 29 At December 31, 2020 and 2019, there were no loans modified under troubled debt restructurings during the previous twelve month period that subsequently defaulted during the years ended December 31, 2020 and 2019. At December 31, 2020 and 2019, the Company had no commitments to lend additional funds to any borrowers with loans whose terms have been modified under troubled debt restructurings. Under ASC Subtopic 310-40 and federal banking agencies interagency guidance, certain short-term loan modifications made on a good faith basis in response to COVID-19 (as defined by the guidance) are not considered TDRs. Additionally, under section 4013 of the CARES Act, banks may elect to suspend the requirement for certain loan modifications to be categorized as a TDR. In response to the COVID-19 pandemic, the Company has implemented prudent modifications allowing for primarily short-term payment deferrals or other payment relief to borrowers with pandemic-related economic hardships, where appropriate, that complies with the above guidance. As such, the Company's TDR loans noted above do not include loans that are modifications to borrowers impacted by COVID-19. Deferred payments along with any interest accrued during the deferral period are due and payable on the maturity date. As of December 31, 2020, the Company has 1,298 loans with outstanding deferred accrued interest of $22,128 on balances of $1,651,376. Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. The following table presents information regarding the aging of past due loans by loan class as of December 31, 2020 and 2019: Loans Loans Total Past Current Total December 31, 2020 Commercial $ 3,243 $ 13,227 $ 16,470 $ 3,846,810 $ 3,863,280 Commercial real estate, construction, land and land development 2,453 16,790 19,243 7,152,247 7,171,490 Residential real estate 5,169 1,028 6,197 1,341,587 1,347,784 Single-family interim construction — — — 326,575 326,575 Agricultural — 1 1 84,896 84,897 Consumer 86 41 127 66,810 66,937 Other — — — 346 346 10,951 31,087 42,038 12,819,271 12,861,309 Acquired with deteriorated credit quality 624 3,219 3,843 210,943 214,786 $ 11,575 $ 34,306 $ 45,881 $ 13,030,214 $ 13,076,095 December 31, 2019 Commercial $ 4,512 $ 17,656 $ 22,168 $ 2,397,531 $ 2,419,699 Commercial real estate, construction, land and land development 9,153 2,905 12,058 6,878,394 6,890,452 Residential real estate 3,242 642 3,884 1,504,020 1,507,904 Single-family interim construction 2,836 — 2,836 375,284 378,120 Agricultural 22 114 136 93,815 93,951 Consumer 167 22 189 32,389 32,578 Other — — — 621 621 19,932 21,339 41,271 11,282,054 11,323,325 Acquired with deteriorated credit quality 2,556 6,766 9,322 283,323 292,645 $ 22,488 $ 28,105 $ 50,593 $ 11,565,377 $ 11,615,970 The Company’s internal classified report is segregated into the following categories: 1) Pass/Watch, 2) Special Mention, 3) Substandard and 4) Doubtful. The loans placed in the Pass/Watch category reflect the Company’s opinion that the loans reflect potential weakness that requires monitoring on a more frequent basis. The loans in the Special Mention category reflect the Company’s opinion that the credit contains weaknesses which represent a greater degree of risk and warrant extra attention. These loans are reviewed monthly by officers and senior management to determine if a change in category is warranted. The loans placed in the Substandard category are considered to be potentially inadequately protected by the current debt service capacity of the borrower and/or the pledged collateral. These credits, even if apparently protected by collateral value, have shown weakness related to adverse financial, managerial, economic, market or political conditions which may jeopardize repayment of principal and interest. There is a possibility that some future loss could be sustained by the Company if such weakness is not corrected. The Doubtful category includes loans that are in default or principal exposure is probable. Substandard and Doubtful loans are individually evaluated to determine if they should be classified as impaired and an allowance is allocated if deemed necessary under ASC 310-10. The loans that are not impaired are included with the remaining “pass” credits in determining the portion of the allowance for loan loss based on historical loss experience and other qualitative factors. The portfolio is segmented into categories including: commercial loans, consumer loans, commercial real estate loans, residential real estate loans and agricultural loans. The adjusted historical loss percentage is applied to each category. Each category is then added together to determine the allowance allocated under ASC 450-20. A summary of loans by credit quality indicator by class as of December 31, 2020 and 2019, is as follows: Pass Pass/ Special Mention Substandard Doubtful Total December 31, 2020 Commercial $ 3,700,626 $ 55,960 $ 38,186 $ 97,403 $ 10,091 $ 3,902,266 Commercial real estate, construction, land and land development 6,504,933 352,910 360,963 123,671 — 7,342,477 Residential real estate 1,332,757 6,296 5,726 7,686 — 1,352,465 Single-family interim construction 323,800 2,775 — — — 326,575 Agricultural 76,951 6,194 1,205 664 — 85,014 Consumer 66,854 8 — 90 — 66,952 Other 346 — — — — 346 $ 12,006,267 $ 424,143 $ 406,080 $ 229,514 $ 10,091 $ 13,076,095 December 31, 2019 Commercial $ 2,332,611 $ 71,642 $ 37,739 $ 40,364 $ — $ 2,482,356 Commercial real estate, construction, land and land development 6,814,780 184,720 46,889 62,887 — 7,109,276 Residential real estate 1,501,019 4,850 994 8,364 — 1,515,227 Single-family interim construction 376,887 1,233 — — — 378,120 Agricultural 88,044 5,287 1,864 2,572 — 97,767 Consumer 32,459 33 2 109 — 32,603 Other 621 — — — — 621 $ 11,146,421 $ 267,765 $ 87,488 $ 114,296 $ — $ 11,615,970 The Company has acquired certain loans which experienced credit deterioration since origination (purchased credit impaired (PCI) loans). The Company has included PCI loans in the above grading tables. The following provides additional detail on the grades applied to those loans at December 31, 2020 and 2019: Pass Pass/ Special Mention Substandard Doubtful Total December 31, 2020 $ 117,896 $ 45,672 $ 32,557 $ 18,661 $ — $ 214,786 December 31, 2019 232,095 21,284 4,502 34,764 — 292,645 PCI loans may remain on accrual status to the extent the company can reasonably estimate the amount and timing of expected future cash flows. At December 31, 2020 and 2019, nonaccrual PCI loans were $6,699 and $10,850, respectively. Accretion on PCI loans is based on estimated future cash flows, regardless of contractual maturity. The following table summarizes the outstanding balance and related carrying amount of PCI loans by acquired bank as of the acquisition date for the acquisition occurring in 2019. Acquisition Date January 1, 2019 Guaranty Bancorp Outstanding balance $ 341,645 Nonaccretable difference (16,622) Accretable yield (13,299) Carrying amount $ 311,724 The carrying amount of all acquired PCI loans included in the consolidated balance sheet and the related outstanding balance at December 31, 2020 and 2019, were as follows: December 31, 2020 2019 Outstanding balance $ 237,786 $ 326,077 Carrying amount 214,786 292,645 There was an allocation of $194 and $849 established in the allowance for loan losses relating to PCI loans at December 31, 2020 and 2019, respectively. The changes in accretable yield during the years ended December 31, 2020 and 2019 in regard to loans transferred at acquisition for which it was probable that all contractually required payments would not be collected are presented in the table below. 2020 2019 Balance at January 1 $ 8,905 $ 1,436 Additions — 13,299 Accretion (3,287) (5,830) Transfers from nonaccretable — — Balance at December 31 $ 5,618 $ 8,905

Premises and Equipment, Net

Premises and Equipment, Net	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Premises and Equipment, Net	Premises and Equipment, Net Premises and equipment, net at December 31, 2020 and 2019 consisted of the following: December 31, 2020 2019 Land $ 65,103 $ 58,643 Building 191,940 184,589 Furniture, fixtures and equipment 39,282 39,855 Aircraft 8,947 8,947 Leasehold and tenant improvements 5,798 5,466 Construction in progress 915 834 311,985 298,334 Less accumulated depreciation (62,518) (55,460) $ 249,467 $ 242,874 Depreciation expense amounted to $12,728, $11,783 and $8,391 for the years ended December 31, 2020, 2019 and 2018, respectively.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets, Net	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets, Net	Goodwill and Other Intangible Assets, Net At December 31, 2020 and 2019, goodwill totaled $994,021. The Company recorded goodwill of $272,224 relating to the Guaranty Bancorp acquisition in 2019 (see Note 22, Business Combinations ). The following is a summary of other intangible assets activity: December 31, 2020 2019 Core deposit intangible: Balance at beginning of the year $ 125,884 $ 63,891 Additions: Guaranty acquisition — 61,993 Balance at end of the year 125,884 125,884 Less accumulated amortization (43,235) (31,057) Total core deposit intangible, net $ 82,649 $ 94,827 Customer relationship intangible: Balance at beginning of the year $ 6,407 $ — Additions: Guaranty acquisition — 9,525 Deletions: sale of trust business — (3,118) Balance at end of the year 6,407 6,407 Less accumulated amortization (986) (493) Total customer relationship intangible, net $ 5,421 $ 5,914 Total other intangible assets, net $ 88,070 $ 100,741 Amortization expense related to intangible assets amounted to $12,671, $12,880 and $5,739 for the years ended December 31, 2020, 2019 and 2018, respectively. The remaining weighted average amortization period for intangible assets is 7.4 years as of December 31, 2020. The future amortization expense related to other intangible assets remaining at December 31, 2020 is as follows: First year $ 12,580 Second year 12,491 Third year 12,439 Fourth year 11,752 Fifth year 11,238 Thereafter 27,570 $ 88,070

Deposits

Deposits	12 Months Ended
	Dec. 31, 2020
Deposits [Abstract]
Deposits	Deposits Deposits at December 31, 2020 and 2019 consisted of the following: December 31, 2020 2019 Amount Percent Amount Percent Noninterest-bearing demand accounts $ 4,164,800 28.9 % $ 3,240,185 27.1 % Interest-bearing checking accounts 5,420,548 37.6 4,198,772 35.2 Savings accounts 654,733 4.6 552,585 4.6 Limited access money market accounts 2,743,208 19.1 2,119,878 17.8 Certificates of deposit and individual retirement accounts (IRA), less than $250,000 675,329 4.7 892,639 7.5 Certificates of deposit and individual retirement accounts (IRA), $250,000 and greater 740,309 5.1 937,277 7.8 $ 14,398,927 100.0 % $ 11,941,336 100.0 % At December 31, 2020, the scheduled maturities of certificates of deposit, including IRAs, were as follows: First year $ 1,263,633 Second year 117,521 Third year 19,362 Fourth year 5,058 Fifth year 10,059 Thereafter 5 $ 1,415,638

Federal Home Loan Bank Advances

Federal Home Loan Bank Advances	12 Months Ended
	Dec. 31, 2020
Advances from Federal Home Loan Banks [Abstract]
Federal Home Loan Bank Advances	Federal Home Loan Bank Advances At December 31, 2020, the Company has advances from the FHLB of Dallas under note payable arrangements with maturities which range from July 2021 to February 2035. Interest payments on these notes are made monthly. The weighted average interest rate of all notes was 0.57% and 2.17% at December 31, 2020 and 2019, respectively. The balances outstanding on these advances were $375,000 and $325,000 at December 31, 2020 and 2019, respectively. Contractual maturities of FHLB advances at December 31, 2020 were as follows: First year $ 25,000 Second year — Third year 200,000 Fourth year — Fifth year — Thereafter 150,000 $ 375,000 The advances are secured by $17,156 of FHLB stock owned by the Company and a blanket lien on certain loans along with specific listed loans for an aggregate available carrying value of $5,708,883 at December 31, 2020. The Company had remaining credit available under the FHLB advance program of $4,091,643 at December 31, 2020. At December 31, 2020, the Company had $1,240,851 in undisbursed advance commitments (letters of credit) with the FHLB. As of December 31, 2020, these commitments mature on various dates from January 2021 through June 2022. The FHLB letters of credit were obtained in lieu of pledging securities to secure public fund deposits that are over the FDIC insurance limit. At December 31, 2020, there were no disbursements against the advance commitments.

Other Borrowings

Other Borrowings	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Other Borrowings	Other Borrowings Other borrowings at December 31, 2020 and 2019 consisted of the following: December 31, 2020 2019 Unsecured fixed rate subordinated debentures in the amount of $110,000. The balance of borrowings at December 31, 2020 and 2019 is net of discount and origination costs of $1,271 and $1,628, respectively. Interest payments of 5.875% are made semiannually on February 1 and August 1. The maturity date is August 1, 2024. The notes may not be redeemed prior to maturity and meet the criteria to be recognized as Tier 2 capital for regulatory purposes. (1)(2) $ 108,729 $ 108,372 Unsecured fixed-to-floating subordinated debentures in the original amount of $40,000. Interest payments initially of 5.75% are made semiannually on January 20 and July 20 through July 20, 2021. Thereafter, floating rate payments of 3 month LIBOR plus 4.73% are made quarterly in arrears beginning on October 20, 2021. The maturity date is July 20, 2026 with an optional redemption at July 20, 2021. The notes meet the criteria to be recognized as Tier 2 capital for regulatory purposes. (2)(3) 40,000 40,000 Unsecured fixed-to-floating subordinated debentures in the amount of $30,000. The balance of borrowings at December 31, 2020 and 2019 is net of origination costs of $543 and $621, respectively. Interest payments initially of 5.00% fixed rate are made semiannually on June 30 and December 31 through December 31, 2022. Thereafter, floating rate payments of 3 month LIBOR plus 2.83% are made quarterly in arrears beginning on March 31, 2023. The maturity date is December 31, 2027 with an optional redemption at December 31, 2022. The notes meet the criteria to be recognized as Tier 2 capital for regulatory purposes. (2) 29,457 29,379 Unsecured fixed-to-floating subordinated debentures in the amount of $130,000. The balance of borrowings at December 31, 2020 is net of origination costs of $2,511. Interest payments initially of 4.00% fixed rate are made semiannually on March 15 and September 15 through September 15, 2025. Thereafter, floating rate payments equal to a benchmark rate (which is expected to be 3 month Secured Overnight Financing Rate (SOFR)) plus 3.885% payable quarterly in arrears beginning on December 15, 2025. The maturity date is September 15, 2030 with an optional redemption at September 15, 2025. The notes meet the criteria to be recognized as Tier 2 capital for regulatory purposes. (2) 127,489 — Unsecured revolving line of credit with an unrelated commercial bank in the amount of $100,000. The line bears interest at LIBOR plus 1.75% and matures January 17, 2021. The Company is required to meet certain financial covenants on a quarterly basis, which includes certain restrictions on cash at IBG and meeting minimum capital ratios. (4) 6,500 24,500 $ 312,175 $ 202,251 ____________ (1) At December 31, 2020 and 2019, other borrowings included amounts owed to related parties of $50. (2) The permissible portion of qualified subordinated notes decreases 20% per year during the final five years of the term of the notes. (3) Assumed on January 1, 2019 with the Guaranty acquisition (see Note 22, Business Combinations ). (4) Subsequent to December 31, 2020, the Company renewed the line (see Note 24, Subsequent Events ). The Company has established federal funds lines of credit notes with nine unaffiliated banks totaling $365,000 of borrowing capacity at December 31, 2020 and ten unaffiliated banks totaling $375,000 of borrowing capacity at December 31, 2019. At December 31, 2020, two of the lines totaling $30,000 have stated maturity dates in August and September 2021. The remaining lines have no stated maturity dates and the lenders may terminate the lines at any time without notice. The lines are provided on an unsecured basis and must be repaid the following business day from when the funds are borrowed. There were no borrowings against the lines at December 31, 2020 and 2019. In addition, the Company maintains a secured line of credit with the Federal Reserve Bank with an availability to borrow approximately $716,700 and $895,110 at December 31, 2020 and 2019, respectively. Approximately $1,034,467 and $1,196,491 of commercial loans were pledged as collateral at December 31, 2020 and 2019, respectively. There were no borrowings against this line as of December 31, 2020 and 2019.

Junior Subordinated Debentures

Junior Subordinated Debentures	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Junior Subordinated Debentures	Junior Subordinated DebenturesThe Company has formed or acquired nine statutory business trusts (the Trusts) for the purpose of issuing trust preferred securities. Each of the Trusts have issued capital and common securities and invested the proceeds thereof in an equivalent amount of junior subordinated debentures (the Debentures) issued by the Company. The interest rate payable on, and the payment terms of the Debentures are the same as the distribution rate and payment terms of the respective issues of capital and common securities issued by the Trusts. The Debentures are subordinated and junior in right of payment to all present and future senior indebtedness. The Company has fully and unconditionally guaranteed the obligations of each of the Trusts with respect to the capital and common securities. Except under certain circumstances, the common securities issued to the Company by the trusts possess sole voting rights with respect to matters involving those entities. Under certain circumstances, the Company may, from time to time, defer the debentures' interest payments, which would result in a deferral of distribution payments on the related trust preferred securities and, with certain exceptions, prevent the Company from declaring or paying cash distributions on the Company's common stock and any other future debt ranking equally with or junior to the debentures. The Company may redeem the debentures, which are intended to qualify as Tier 1 capital, at the Company’s option, subject to approval of the Federal Reserve. As of December 31, 2020 and 2019, the carrying amount of debentures outstanding totaled $54,023 and $53,824, respectively. Information regarding the Debentures as of December 31, 2020 are summarized in the table below: Trust Preferred Securities Issued Debentures Carrying Value Repricing Frequency Interest Rate Interest Rate Index Maturity Date IB Trust I $ 5,155 $ 5,155 Quarterly 3.46% LIBOR + 3.25% March 2033 Guaranty Trust III (1) 10,310 10,310 Quarterly 3.34 LIBOR + 3.10 July 2033 IB Trust II 3,093 3,093 Quarterly 3.09 LIBOR + 2.85 March 2034 Cenbank Trust III (1) 15,464 15,464 Quarterly 2.89 LIBOR + 2.65 April 2034 IB Trust III 3,712 3,712 Quarterly 2.61 LIBOR +2.40 December 2035 IB Centex Trust I 2,578 2,578 Quarterly 3.46 LIBOR + 3.25 February 2035 Community Group Statutory Trust I 3,609 3,609 Quarterly 1.82 LIBOR + 1.60 June 2037 Northstar Trust II (2) 5,155 3,892 Quarterly 1.89 LIBOR + 1.67 June 2037 Northstar Trust III (2) 8,248 6,210 Quarterly 1.89 LIBOR + 1.67 September 2037 $ 57,324 $ 54,023 ____________ (1) Assumed on January 1, 2019 with the Guaranty acquisition (see Note 22, Business Combinations ).

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	Leases The Company’s primary leasing activities relate to certain real estate operating leases entered into in support of the Company’s branch operations and back office operations. The Company leases 21 of its 93 branches. The Company’s branch locations operated under lease agreements have all been designated as operating leases. In addition, the Company leases certain equipment under operating leases. The Company does not have leases designated as finance leases. As of December 31, 2020 and 2019 the Company’s lease ROU assets were $24,841 and $38,813, respectively, and related lease liabilities were $23,413 and $28,978, respectively. Leases have remaining terms ranging from 1 to 30 years, including extension options that the Company is reasonably certain will be exercised. The table below summarizes net lease cost: Year Ended December 31, 2020 2019 Operating lease cost $ 6,937 $ 7,025 Short term lease cost 124 103 Variable lease cost 1,631 1,829 Sublease income (221) (228) Net lease cost $ 8,471 $ 8,729 Rent expense for the year ended December 31, 2018, prior to the adoption of ASU 2016-2, was $3,758. The table below summarizes other information related to operating leases: Year Ended December 31, 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 6,091 $ 6,965 Weighted average remaining lease term - operating leases, in years 7.23 7.58 Weighted average discount rate - operating leases 3.47 % 3.35 % The following table outlines lease payment obligations as outlined in the Company’s lease agreements for each of the next five years and thereafter in addition to a reconcilement to the Company’s current lease liability as of December 31, 2020. 2021 $ 5,615 2022 4,876 2023 4,054 2024 3,438 2025 2,754 Thereafter 5,700 Total lease payments 26,437 Less imputed interest (3,024) $ 23,413 As of December 31, 2020, the Company had not entered into any material leases that have not yet commenced.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense for the years ended December 31, 2020, 2019 and 2018 was as follows: Years Ended December 31, 2020 2019 2018 Current income tax expense $ 52,806 $ 39,426 $ 29,801 Deferred income tax (benefit) expense (1,633) 14,102 2,000 Deferred income tax benefit related to remeasurement of deferred taxes — — (63) Income tax expense, as reported $ 51,173 $ 53,528 $ 31,738 A reconciliation between reported income tax expense and the amounts computed by applying the U.S. federal statutory income tax rate of 21% for the years ended December 31, 2020, 2019 and 2018 to income before income taxes is presented below: Years Ended December 31, 2020 2019 2018 Income tax expense computed at the statutory rate $ 53,000 $ 51,715 $ 33,599 Tax-exempt interest income from municipal securities (1,779) (1,781) (962) Tax-exempt loan income (1,245) (1,174) (490) Bank owned life insurance income (1,123) (1,288) (666) Non-deductible acquisition expenses — 281 142 State taxes, net of federal benefit 2,660 3,455 375 Non-deductible compensation — 2,017 — Net tax expense (benefit) from stock based compensation 243 21 (646) Deferred tax adjustment related to reduction in U.S. Federal statutory income tax rate — — (63) Other (583) 282 449 $ 51,173 $ 53,528 $ 31,738 Components of deferred tax assets and liabilities are presented in the table below. Deferred taxes as of December 31, 2020 and 2019 are based on the U.S. statutory federal income tax rate of 21%. December 31, 2020 2019 Deferred tax assets: Allowance for loan losses $ 19,238 $ 11,466 Lease liabilities under operating leases 5,129 6,457 NOL and tax credit carryforwards from acquisitions 3,718 4,209 Acquired loan fair market value adjustments 12,986 21,645 Stock-based compensation 1,567 1,218 Reserve for bonuses and other accrued expenses 3,409 2,773 Acquisition costs — 416 Acquired securities 2,095 2,529 Acquired intangibles 1,369 1,546 Start up costs 171 230 Other real estate owned — 362 Unearned income 715 774 Deferred compensation 857 1,101 Noncompete agreements 597 663 Nonaccrual loans 550 390 Other 727 785 53,128 56,564 Deferred tax liabilities: Premises and equipment (12,392) (13,170) Right-of-use assets under operating leases (4,911) (6,233) Net unrealized gain on available for sale securities (9,501) (5,367) Intangible assets (19,293) (22,447) Acquired junior subordinated debentures fair value adjustment (723) (780) PPP deferred loan costs (952) — FHLB and other restricted stocks (308) (673) Acquired tax goodwill (572) (413) Other (543) (538) (49,195) (49,621) Net deferred tax asset $ 3,933 $ 6,943 At December 31, 2020, the Company had federal net operating loss carryforwards of approximately $15,765 which expire in various years from 2023 to 2032 and state net operating loss carryforwards of approximately $11,150 which expire in various years from 2025 to 2027. Deferred tax assets are recognized for net operating losses because the benefit is more likely than not to be realized. No valuation allowance for deferred tax assets was recorded at December 31, 2020 or 2019 as management believes it is more likely than not that all of the deferred tax assets will be realized.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Financial Instruments with Off-Balance Sheet Risk The Company is a party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. The commitments involve, to varying degrees, elements of credit and interest rate risk in excess of the amount recognized in the balance sheet. The Company’s exposure to credit loss in the event of nonperformance by the other party to the financial instrument for commitments to extend credit is represented by the contractual amount of this instrument. The Company uses the same credit policies in making commitments and conditional obligations as it does for on-balance sheet instruments. At December 31, 2020 and 2019, the approximate amounts of these financial instruments were as follows: December 31, 2020 2019 Commitments to extend credit $ 2,268,216 $ 2,337,385 Standby letters of credit 25,917 23,406 $ 2,294,133 $ 2,360,791 Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company evaluates each customer’s credit worthiness on a case-by-case basis. The amount of collateral obtained if deemed necessary by the Company upon extension of credit is based on management’s credit evaluation of the counterparty. Collateral held varies but may include accounts receivable, inventory, farm crops, property, plant and equipment and income-producing commercial properties. Letters of credit are written conditional commitments used by the Company to guarantee the performance of a customer to a third party. The Company’s policies generally require that letter of credit arrangements contain security and debt covenants similar to those contained in loan arrangements. In the event the customer does not perform in accordance with the terms of the agreement with the third party, the Company would be required to fund the commitment. The maximum potential amount of future payments the Company could be required to make is represented by the contractual amount shown in the table above. If the commitment is funded, the Company would be entitled to seek recovery from the customer. As of December 31, 2020 and 2019, no amounts have been recorded as liabilities for the Company’s potential obligations under these guarantees. Litigation The Company is involved in certain legal actions arising from normal business activities. Management believes that the outcome of such proceedings will not materially affect the financial position, results of operations or cash flows of the Company. A legal proceeding that the Company believes could become material is described below.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions In the ordinary course of business, the Company has and expects to continue to have transactions, including loans to its officers, directors and their affiliates. In the opinion of management, such transactions are on the same terms as those prevailing at the time for comparable transactions with unaffiliated persons. Loan activity for officers, directors and their affiliates for the year ended December 31, 2020 is as follows: Balance at beginning of year $ 38,796 New loans 30,912 Repayments (38,570) Changes in affiliated persons 1,333 Balance at end of year $ 32,471 See Note 11, Other Borrowings , for related party borrowings.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit PlansThe Company has a 401(k) profit sharing plan (Plan) which covers employees over the age of eighteen

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The fair value of an asset or liability is the price that would be received to sell that asset or paid to transfer that liability in an orderly transaction occurring in the principal market (or most advantageous market in the absence of a principal market) for such asset or liability. In estimating fair value, the Company utilizes valuation techniques that are consistent with the market approach, the income approach and/or the cost approach. Such valuation techniques are consistently applied. Inputs to valuation techniques include the assumptions that market participants would use in pricing an asset or liability. ASC Topic 820, Fair Value Measurements and Disclosures , 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 might 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 (such as interest rates, volatilities, prepayment speeds, credit risks, etc.) or inputs that are derived principally from or corroborated by market data by correlation or other means. Level 3 Inputs – Unobservable inputs for determining the fair values of assets or liabilities that reflect an entity’s own assumptions about the assumptions that market participants would use in pricing the assets or liabilities. The Company elected the fair value option for certain residential mortgage loans held for sale in accordance with ASC 825, Financial Instruments. This election allows for a more effective offset of the changes in fair values of the loans and the derivative instruments used to economically hedge them without the burden of complying with the requirements for hedge accounting under ASC 815, Derivatives and Hedging . The Company has not elected the fair value option for other residential mortgage loans held for sale primarily because they are not economically hedged using derivative instruments. See below and Note 19, Derivative Financial Instruments , for additional information. Assets and Liabilities Measured on a Recurring Basis The following table represents assets and liabilities reported on the consolidated balance sheets at their fair value on a recurring basis as of December 31, 2020 and 2019 by level within the ASC Topic 820 fair value measurement hierarchy: Fair Value Measurements at Reporting Date Using Assets/ Quoted Prices Significant Significant December 31, 2020 Assets: Investment securities available for sale: U.S. treasuries $ 44,708 $ — $ 44,708 $ — Government agency securities 249,017 — 249,017 — Obligations of state and municipal subdivisions 393,165 — 393,165 — Corporate bonds 22,102 — 22,102 — Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 443,501 — 443,501 — Other securities 1,200 — 1,200 — Loans held for sale, fair value option elected (1) 71,769 — 71,769 — Derivative financial instruments: Interest rate lock commitments 3,515 — 3,515 — Loan customer counterparty 20,159 — 20,159 — Liabilities: Derivative financial instruments: Forward mortgage-backed securities trades 568 — 568 — Financial institution counterparty 21,306 — 21,306 — December 31, 2019 Assets: Investment securities available for sale: U.S. treasuries $ 48,796 $ — $ 48,796 $ — Government agency securities 179,296 — 179,296 — Obligations of state and municipal subdivisions 343,859 — 343,859 — Corporate bonds 7,218 — 7,218 — Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 505,567 — 505,567 — Other securities 1,200 — 1,200 — Loans held for sale, fair value option elected (1) 29,204 — 29,204 — Derivative financial instruments: Interest rate lock commitments 847 — 847 — Forward mortgage-backed securities trades 6 — 6 — Loan customer counterparty 6,104 — 6,104 — Liabilities: Derivative financial instruments: Forward mortgage-backed securities trades 69 — 69 — Financial institution counterparty 6,566 — 6,566 — ____________ (1) At December 31, 2020 and 2019, loans held for sale for which the fair value option was elected had an aggregate outstanding principal balance of $68,670 and $28,166, respectively. There were no mortgage loans held for sale under the fair value option that were 90 days or greater past due or on nonaccrual at December 31, 2020. A description of the valuation methodologies used for instruments measured at fair value, as well as the general classification of such instruments pursuant to the valuation hierarchy, is set forth below. Investment securities Securities classified as available for sale are reported at fair value utilizing Level 1 and Level 2 inputs. Securities are classified within Level 1 when quoted market prices are available in an active market. Inputs include securities that have quoted prices in active markets for identical assets. For securities utilizing Level 2 inputs, the Company obtains fair value measurements from an independent pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury and other yield curves, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the security’s terms and conditions, among other things. Loans held for sale Certain mortgage loans held for sale are measured at fair value on a recurring basis due to the Company's election to adopt fair value accounting treatment for those loans originated for which the Company has entered into certain derivative financial instruments as part of its mortgage banking and related risk management activities. These instruments include interest rate lock commitments and mandatory forward commitments to sell these loans to investors known as forward mortgage-backed securities trades. This election allows for a more effective offset of the changes in fair values of the assets and the mortgage related derivative instruments used to economically hedge them without the burden of complying with the requirements for hedge accounting under ASC 815, Derivatives and Hedging. Mortgage loans held for sale, for which the fair value option was elected, which are sold on a servicing released basis, are valued using a market approach by utilizing either: (i) the fair value of 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 to 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. For mortgage loans held for sale for which the fair value option was elected, the earned current contractual interest payment is recognized in interest income, loan origination costs and fees on fair value option loans are recognized in earnings as incurred and not deferred. The Company has no continuing involvement in any residential mortgage loans sold. Derivatives The estimated fair values of interest rate lock commitments utilize current secondary market prices for underlying loans and estimated servicing value with similar coupons, maturity and credit quality, subject to the anticipated loan funding probability (pull-through rate). The fair value of interest rate lock commitments 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, as the valuations are based on observable market inputs. Forward mortgage-backed securities trades are exchange-traded or traded within highly active dealer markets. In order to determine the fair value of these instruments, the Company utilized the exchange price or dealer market price for the particular derivative contract; therefore these contracts are classified as Level 2. The estimated fair values are subject to change primarily due to changes in interest rates. The Company also enters into certain interest rate derivative positions that are not designated as hedging instruments. The estimated fair value of these commercial loan interest rate swaps are obtained from a pricing service that provides the swaps' unwind value (Level 2 inputs). See Note 19, Derivative Financial Instruments , for more information. Assets and Liabilities Measured on a Nonrecurring Basis In accordance with ASC Topic 820, certain assets and liabilities are measured at fair value on a nonrecurring basis; that is, the assets and liabilities are not measured at fair value on an ongoing basis but are subject to fair value adjustments in certain circumstances (for example, when there is evidence of impairment). The following table presents the assets carried on the consolidated balance sheet by caption and by level in the fair value hierarchy at December 31, 2020 and 2019, for which a nonrecurring change in fair value has been recorded: Fair Value Measurements at Reporting Date Using Assets Quoted Prices Significant Significant Period Ended December 31, 2020 Assets: Impaired loans $ 16,903 $ — $ — $ 16,903 $ 13,041 December 31, 2019 Assets: Impaired loans $ 2,276 $ — $ — $ 2,276 $ 1,806 Other real estate owned 4,618 — — 4,618 749 Impaired loans (loans which are not expected to repay all principal and interest amounts due in accordance with the original contractual terms) are measured at an observable market price (if available) or at the fair value of the loan’s collateral (if collateral dependent). Fair value of the loan’s collateral is determined by appraisals or independent valuation, which is then adjusted for the estimated costs related to liquidation of the collateral. Management’s ongoing review of appraisal information may result in additional discounts or adjustments to valuation based upon more recent market sales activity or more current appraisal information derived from properties of similar type and/or locale. Therefore, the Company has categorized its impaired loans as Level 3. Other real estate is measured at fair value on a nonrecurring basis (upon initial recognition or subsequent impairment). Other real estate is classified within Level 3 of the valuation hierarchy. When transferred from the loan portfolio, other real estate is adjusted to fair value less estimated selling costs and is subsequently carried at the lower of carrying value or fair value less estimated selling costs. The fair value is determined using an external appraisal process, discounted based on internal criteria. Therefore, the Company has categorized its other real estate as Level 3. In addition, mortgage loans held for sale not recorded under the fair value option are required to be measured at the lower of cost or fair value. The fair value of these loans is based upon binding quotes or bids from third party investors. As of December 31, 2020 and 2019, all mortgage loans held for sale not recorded under the fair value option were recorded at cost. Fair Value of Financial Instruments not Recorded at Fair Value The carrying amount, estimated fair value and the level of the fair value hierarchy of the Company’s financial instruments that are reported at amortized cost on the Company's consolidated balance sheets were as follows at December 31, 2020 and 2019: Fair Value Measurements at Reporting Date Using Carrying Estimated Quoted Prices Significant Significant December 31, 2020 Financial assets: Cash and cash equivalents $ 1,813,987 $ 1,813,987 $ 1,813,987 $ — $ — Certificates of deposit held in other banks 4,482 4,595 — 4,595 — Loans held for sale, at cost 10,878 11,138 — 11,138 — Loans, net 12,978,238 13,093,698 — — 13,093,698 FHLB of Dallas stock and other restricted stock 20,305 20,305 — 20,305 — Accrued interest receivable 60,581 60,581 — 60,581 — Financial liabilities: Deposits 14,398,927 14,407,596 — 14,407,596 — Accrued interest payable 7,397 7,397 — 7,397 — FHLB advances 375,000 371,175 — 371,175 — Other borrowings 312,175 327,150 — 327,150 — Junior subordinated debentures 54,023 42,624 — 42,624 — Off-balance sheet assets (liabilities): Commitments to extend credit — — — — — Standby letters of credit — — — — — December 31, 2019 Financial assets: Cash and cash equivalents $ 565,170 $ 565,170 $ 565,170 $ — $ — Certificates of deposit held in other banks 5,719 5,951 — 5,951 — Loans held for sale, at cost 6,441 6,554 — 6,554 — Loans, net 11,562,814 11,689,672 — — 11,689,672 FHLB of Dallas stock and other restricted stock 30,052 30,052 — 30,052 — Accrued interest receivable 35,860 35,860 — 35,860 — Financial liabilities: Deposits 11,941,336 11,958,939 — 11,958,939 — Accrued interest payable 9,583 9,583 — 9,583 — FHLB advances 325,000 325,210 — 325,210 — Other borrowings 202,251 209,050 — 209,050 — Junior subordinated debentures 53,824 48,879 — 48,879 — Off-balance sheet assets (liabilities): Commitments to extend credit — — — — — Standby letters of credit — — — — — The methods and assumptions used by the Company in estimating fair values of financial instruments as disclosed herein in accordance with ASC Topic 825, Financial Instruments, other than for those measured at fair value on a recurring and nonrecurring basis discussed above, are as follows: Cash and cash equivalents: The carrying amounts of cash and cash equivalents approximate their fair value. Certificates of deposit held in other banks: The fair value of certificates of deposit held in other banks is based upon current market rates. Loans held for sale, at cost: The fair value of loans held for sale is determined based upon commitments on hand from investors. Loans: A discounted cash flow model is used to estimate the fair value of the loans. The discounted cash flow approach models the credit losses directly in the projected cash flows, applying various assumptions regarding credit, interest and prepayment risks for the loans based on loan types, payment types and fixed or variable classifications. Federal Home Loan Bank of Dallas and other restricted stock: The carrying value of restricted securities such as stock in the Federal Home Loan Bank of Dallas and Independent Bankers Financial Corporation approximates fair value. Deposits: The fair values disclosed for demand deposits are, by definition, equal to the amount payable on demand at the reporting date (that is their carrying amounts). The carrying amounts of variable-rate certificates of deposit (CDs) approximate their fair values at the reporting date. Fair values for fixed-rate CDs are estimated using a discounted cash flow calculation that applies interest rates currently being offered on certificates to a schedule of aggregated expected monthly maturities on time deposits. Federal Home Loan Bank advances, line of credit and federal funds purchased: The fair value of advances maturing within 90 days approximates carrying value. Fair value of other advances is based on the Company’s current borrowing rate for similar arrangements. Other borrowings: The estimated fair value approximates carrying value for short-term borrowings. The fair value of private subordinated debentures are based upon prevailing rates on similar debt in the market place. The subordinated debentures that are publicly traded are valued based on indicative bid prices based upon market pricing observations in the current market. Junior subordinated debentures: The fair value of junior subordinated debentures is estimated using discounted cash flow analyses based on the published Bloomberg US Financials BB rated corporate bond index yield. Accrued interest: The carrying amounts of accrued interest approximate their fair values. Off-balance sheet instruments: Fair values for off-balance sheet, credit-related financial instruments are based on fees currently charged to enter into similar agreements, taking into account the remaining terms of the agreements and the counterparties' credit standing. The fair value of commitments is not material.

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments The Company enters into certain derivative financial instruments as part of its hedging strategy. These financial instruments are not designated as hedging instruments and are used for asset and liability management related to the Company's mortgage banking activities and commercial customers' financing needs. All derivatives are carried at fair value in either other assets or other liabilities. Through the normal course of business, the Company enters into interest rate lock commitments with consumers to originate mortgage loans at a specified interest rate. 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 manages the changes in fair value associated with changes in interest rates related to interest rate lock commitments by using forward sold commitments known as forward mortgage-backed securities trades. These instruments are typically entered into at the time the interest rate lock commitment is made. The Company also offers certain derivatives products, primarily interest rate swaps, directly to qualified commercial banking customers to facilitate their risk management strategies. The interest rate swap derivative positions relate to transactions in which the Company enters into an interest rate swap with a customer, while at the same time entering into an offsetting interest rate swap with another financial institution. An interest rate swap transaction allows customers to effectively convert a variable rate loan to a fixed rate. In connection with each swap, the Company agrees to pay interest to the customer on a notional amount at a variable interest rate and receive interest from the customer on a similar notional amount at a fixed interest rate. At the same time, the Company agrees to pay another financial institution the same fixed interest rate on the same notional amount and receive the same variable interest rate on the same notional amount. The following table provides the outstanding notional balances and fair values of outstanding derivative positions at December 31, 2020 and 2019: Outstanding Notional Balance Asset Derivative Liability Derivative December 31, 2020 Interest rate lock commitments $ 116,795 $ 3,515 $ — Forward mortgage-backed securities trades 104,000 — 568 Commercial loan interest rate swaps: Loan customer counterparty 335,370 20,159 — Financial institution counterparty 335,370 — 21,306 December 31, 2019 Interest rate lock commitments $ 28,434 $ 847 $ — Forward mortgage-backed securities trades 42,500 6 69 Commercial loan interest rate swaps: Loan customer counterparty 280,751 6,104 — Financial institution counterparty 280,751 — 6,566 The commercial loan customer counterparty weighted average received and paid interest rates for interest rate swaps outstanding were as follows: Weighted Average Interest Rate December 31, 2020 December 31, 2019 Received Paid Received Paid Loan customer counterparty 4.08 % 2.32 % 4.23 % 3.77 % The credit exposure related to interest rate swaps is limited to the net favorable value of all swaps by each counterparty, which was approximately $20,159 at December 31, 2020. In some cases collateral may be required from the counterparties involved if the net value of the derivative instruments exceeds a nominal amount. Collateral levels are monitored and adjusted on a regular basis for changes in interest rate swap values. At December 31, 2020, cash of $23,829 and securities of $6,494 were pledged as collateral for these derivatives. The Company has entered into credit risk participation agreements with financial institution counterparties for interest rate swaps related to loans in which the Company is either a participant or a lead bank. Risk participation agreements entered into as a participant bank provide credit protection to the financial institution counterparty should the borrower fail to perform on its interest rate derivative contract with that financial institution. The Company is party to one risk participation agreement as a participant bank having a notional amount of $5,597 at December 31, 2020. Risk participation agreements entered into as the lead bank provide credit protection to the Company should the borrower fail to perform on its interest rate derivative contract. The Company is party to one risk participation agreement as the lead bank having a notional amount of $9,604 at December 31, 2020. The changes in the fair value of interest rate lock commitments and the forward sales of mortgage-back securities are recorded in mortgage banking revenue. These gains and losses were not attributable to instrument-specific credit risk. For interest rate swaps, because the Company acts as an intermediary for our customer, changes in the fair value of the underlying derivative contracts substantially offset each other and do not have a material impact on the results of operations. Income (loss) for the years ended December 31, 2020 and 2019 was as follows: Years Ended December 31, 2020 2019 Derivatives not designated as hedging instruments Interest rate lock commitments $ 2,668 $ 25 Forward mortgage-backed securities trades (505) 163

Stock Awards

Stock Awards	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock Awards	Stock AwardsThe Company grants common stock awards to certain employees of the Company. In connection with the Company's initial public offering in April 2013, the Board of Directors adopted the 2013 Equity Incentive Plan (2013 Plan). All stock awards issued under expired plans prior to 2013 are fully vested. Under the 2013 Plan, the Compensation Committee may grant awards to certain employees of the Company in the form of restricted stock, restricted stock rights, restricted stock units, qualified and nonqualified stock options, performance share awards and other equity-based awards. The 2013 Plan, as amended, has 2,300,000 reserved shares of common stock to be awarded by the Company's compensation committee. As of December 31, 2020, there were 1,150,617 shares remaining available for grant for future awards. The shares currently issued under the 2013 Plan are restricted stock awards and performance stock units. Restricted stock awarded to employees vest evenly over the required employment period, generally ranging from one three In connection with the acquisition of Guaranty, as further described in Note 22, Business Combinations , unvested awards of restricted Guaranty common stock granted under Guaranty’s 2015 Long-Term Incentive Plan (Guaranty 2015 RSA), as amended, that were outstanding as of January 1, 2019, the acquisition date, were converted into awards of restricted shares of IBG common stock (Replacement RSA) with the same terms and conditions as were applicable under such Guaranty 2015 RSA, except with respect to any performance-vesting Guaranty 2015 RSA, which became a service-vesting RSA only. The Replacement RSA will vest over the remaining service period, through May 2021, and do not receive dividends. Restricted Stock Awards The following table summarizes the activity in nonvested restricted stock awards for the years ended December 31, 2020 and 2019: Restricted Stock Awards Number of Weighted Average Nonvested shares, December 31, 2019 284,861 $ 58.63 Granted during the period 310,290 43.54 Vested during the period (115,436) 58.08 Forfeited during the period (10,915) 48.37 Nonvested shares, December 31, 2020 468,800 $ 49.01 Nonvested shares, December 31, 2018 252,903 $ 62.81 Acquired awards replaced during the period 70,248 45.77 Granted during the period 138,608 51.14 Vested during the period (161,032) 54.76 Forfeited during the period (15,866) 46.95 Nonvested shares, December 31, 2019 284,861 $ 58.63 Compensation expense related to these awards is recorded based on the fair value of the award at the date of grant and totaled $8,450, $7,808 and $6,062 for the years ended December 31, 2020, 2019 and 2018, respectively. Compensation expense is recorded in salaries and employee benefits in the accompanying consolidated statements of income. At December 31, 2020, future compensation expense is estimated to be $15,823 and will be recognized over a remaining weighted average period of 2.57 years. The fair value of common stock awards that vested during the years ended December 31, 2020, 2019 and 2018 was $5,602, $8,725 and $8,206, respectively. The Company has recorded $243, $21 and $(646) in excess tax expense (benefit) on vested restricted stock to income tax expense for the years ended December 31, 2020, 2019 and 2018, respectively. There were no modifications of stock agreements during 2020, 2019 and 2018 that resulted in significant additional incremental compensation costs. At December 31, 2020, the future vesting schedule of the nonvested restricted stock awards is as follows: First year 177,431 Second year 139,009 Third year 99,604 Fourth year 52,356 Fifth year 400 Total nonvested shares 468,800 Performance Stock Units Performance stock units represent shares potentially issuable in the future. The number of shares issued is based upon the measure of the Company's achievement of its relative adjusted return on average tangible common equity, as defined by the Company, over the award's performance period as compared to an identified peer group's achievement over the same performance period. The number of shares issuable under each performance award is the product of the award target and the award payout percentage for the given level of achievement which ranges from 0% to 150% of the target. The following table summarizes the activity in nonvested performance stock units at target award level for the year ended December 31, 2020: Performance-based Restricted Stock Units Number of Weighted Average Nonvested shares, December 31, 2019 — $ — Granted during the period 89,300 38.29 Vested during the period — — Forfeited during the period — — Nonvested shares, December 31, 2020 89,300 $ 38.29 Compensation expense related to performance stock units is estimated each period based on the fair value of the target stock unit at the grant date and the most probable level of achievement of the performance condition, adjusted for the passage of time within the vesting periods of the awards. As of December 31, 2020, the unrecognized compensation expense assuming the attainment of the maximum payout rate was $5,129 and the remaining performance period over which the expense could be recognized was 3.5 years. No compensation expense was recorded during the year ended December 31, 2020.

Regulatory Matters

Regulatory Matters	12 Months Ended
	Dec. 31, 2020
Regulated Operations [Abstract]
Regulatory Matters	Regulatory Matters Under banking law, there are legal restrictions limiting the amount of dividends the Bank can declare. Approval of the regulatory authorities is required if the effect of dividends declared would cause the regulatory capital of the Bank to fall below specified minimum levels. For state banks, subject to regulatory capital requirements, payment of dividends is generally allowed to the extent of net profits. The Company (on a consolidated basis) and the Bank are subject to various regulatory capital requirements administered by federal and state banking agencies. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Company’s consolidated financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Company and the Bank must meet specific capital guidelines that involve quantitative measures of assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. The capital amounts and classification are also subject to qualitative judgments by the regulators about components, risk weightings and other factors. Tier 2 capital for the Company includes permissible portions of the Company's subordinated notes. The permissible portion of qualified subordinated notes decreases 20% per year during the final five years of the term of the notes. The Company is subject to the Basel III regulatory capital framework (the Basel III Capital Rules). The Basel III Capital Rules require that the Company maintain a 2.5% capital conservation buffer above the minimum risk-based capital adequacy requirements. The capital conservation buffer is designed to absorb losses during periods of economic stress and requires increased capital levels for the purpose of capital distributions and other payments. Failure to meet the full amount of the buffer will result in restrictions on the Company's ability to make capital distributions, including dividend payments and stock repurchases and to pay discretionary bonuses to executive officers. Quantitative measures established by regulation to ensure capital adequacy require the Company and the Bank to maintain minimum amounts and ratios (set forth in the table below) of total, Common Equity Tier 1 (CET1) and Tier 1 capital (as defined in the regulations) to risk weighted assets (as defined), and of Tier 1 capital (as defined) to average assets (as defined). Management believes, as of December 31, 2020 and 2019, the Company and the Bank meet all capital adequacy requirements to which they are subject, including the capital buffer requirement. As of December 31, 2020 and 2019, the Bank’s capital ratios exceeded those levels necessary to be categorized as “well capitalized” under the regulatory framework for prompt corrective action. To be categorized as “well capitalized,” the Bank must maintain minimum total risk based, CET1, Tier 1 risk based and Tier 1 leverage ratios as set forth in the table. There are no conditions or events that management believes have changed the Bank’s category. The following table presents actual capital amounts and required ratios under Basel III Capital Rules for the Company and Bank as of December 31, 2020 and December 31, 2019. Actual Minimum Capital To Be Well Amount Ratio Amount Ratio Amount Ratio December 31, 2020 Total capital to risk weighted assets: Consolidated $ 1,825,661 13.32 % $ 1,438,939 10.50 % N/A N/A Bank 1,864,240 13.61 1,438,385 10.50 $ 1,369,891 10.00 % Tier 1 capital to risk weighted assets: Consolidated 1,471,841 10.74 1,164,855 8.50 N/A N/A Bank 1,776,420 12.97 1,164,407 8.50 1,095,913 8.00 Common equity tier 1 to risk weighted assets: Consolidated 1,416,241 10.33 959,293 7.00 N/A N/A Bank 1,776,420 12.97 958,924 7.00 890,429 6.50 Tier 1 capital to average assets: Consolidated 1,471,841 9.12 645,730 4.00 N/A N/A Bank 1,776,420 11.01 645,539 4.00 806,924 5.00 December 31, 2019 Total capital to risk weighted assets: Consolidated $ 1,513,209 11.83 % $ 1,343,114 10.50 % N/A N/A Bank 1,548,103 12.11 1,342,595 10.50 $ 1,278,662 10.00 % Tier 1 capital to risk weighted assets: Consolidated 1,303,748 10.19 1,087,282 8.50 N/A N/A Bank 1,496,642 11.70 1,086,863 8.50 1,022,930 8.00 Common equity tier 1 to risk weighted assets: Consolidated 1,248,148 9.76 895,409 7.00 N/A N/A Bank 1,496,642 11.70 895,064 7.00 831,130 6.50 Tier 1 capital to average assets: Consolidated 1,303,748 9.32 559,758 4.00 N/A N/A Bank 1,496,642 10.70 559,584 4.00 699,480 5.00 Stock repurchase program: From time to time, the Company's board of directors has authorized stock repurchase programs which allow the Company to purchase its common stock generally over a one-year period at various prices in the open market or in privately negotiated transactions. On October 22, 2020, the Company's board of directors authorized a $150,000 stock repurchase program allowing the Company to purchase shares of its common stock through October 31, 2021. Under this program, the Company repurchased 109,548 shares at a total cost of $5,660 as of December 31, 2020. Under prior stock repurchase programs, the Company repurchased 897,738 at a total cost of $49,048 during 2019 and none during 2018. In July 2019, the federal bank regulators adopted final rules that, among other things, eliminated the standalone prior approval requirement for any repurchase of common stock. However, the Company remains subject to a Federal Reserve Board guideline that requires consultation with the Federal Reserve regarding plans for share repurchases on a quarterly basis. The Company’s repurchases of its common stock may be subject to a prior approval or notice requirement under other regulations, policies or supervisory expectations of the Federal Reserve Board. Any redemption or repurchase of preferred stock or subordinated debt remains subject to the prior approval of the Federal Reserve Board.

Business Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
Business Combinations	Business Combinations Termination of proposed merger with Texas Capital Bancshares, Inc.: The Company and Texas Capital Bancshares, Inc. (TCBI) and its subsidiary, Texas Capital Bank, entered into an Agreement and Plan of Merger (Merger Agreement), as of December 9, 2019, providing for the merger of TCBI with and into the Company (the Merger), with the Company as the surviving entity in the Merger. On May 22, 2020, the Company and TCBI entered into a mutual agreement (Agreement) to terminate the Merger Agreement. All costs and expenses incurred in connection with the Agreement were paid by the party incurring such expense. The Agreement provided that the Company make a payment to TCBI, in an amount agreed between the parties, such that the costs and expenses incurred by the parties related to integration planning, including consulting fees and related expenses, would be borne equally by the parties. Neither party paid a termination fee in connection with the termination of the merger agreement. The Company incurred TCBI costs of approximately $15,605 and $5,022 for the years ended December 31, 2020 and 2019, respectively, which is included in acquisition expense in the consolidated statements of income. Guaranty Bancorp On January 1, 2019, the Company acquired 100% of the outstanding stock of Guaranty Bancorp (Guaranty) and its subsidiary, Guaranty Bank and Trust Company (Guaranty Bank), Denver, Colorado. As a result of the acquisition, the Company added 32 full service branch locations along the Colorado Front Range, including locations throughout the Denver metropolitan area and along I-25 to Fort Collins expanding the Company's footprint in Colorado. The Company issued 13,179,748 shares of Company stock for the outstanding shares of Guaranty common stock, including restricted stock replacement awards. The Company has recognized total goodwill of $272,224 which is calculated as the excess of both the consideration exchanged and liabilities assumed compared to the estimated fair market value of identifiable assets acquired. The goodwill in this acquisition resulted from a combination of expected synergies and expansion into desirable Colorado markets. None of the goodwill recognized is expected to be deductible for income tax purposes. The Company has incurred expenses related to the acquisition of approximately $33,622 for the year ended December 31, 2019, of which $5,328 is included in salaries and benefits and $28,294 is included in acquisition expense in the consolidated statements of income. The Company incurred expense of $1,560 during the year ended December 31, 2018. In addition, for the year ended December 31, 2019, the Company paid offering costs totaling $804 which were recorded as a reduction to stock issuance proceeds through additional paid in capital. The following table summarizes the final fair values of the assets acquired and liabilities assumed in this transaction: Final Value as Reported at December 31, 2019 Assets of acquired bank: Cash and cash equivalents $ 39,913 Certificates of deposit held in other banks 262 Securities available for sale 561,052 Restricted stock 27,794 Loans 2,789,868 Premises and equipment 65,786 Other real estate owned 1,829 Goodwill 272,224 Other intangible assets 71,518 Bank owned life insurance 80,837 Other assets 31,987 Total assets acquired $ 3,943,070 Liabilities of acquired bank: Deposits $ 3,108,810 Repurchase agreements 8,475 FHLB advances 142,653 Other borrowings 40,000 Junior subordinated debentures 25,774 Other liabilities 15,477 Total liabilities assumed $ 3,341,189 Common stock of 13,109,500 issued at $45.77 per share $ 600,022 Consideration attributable to 70,248 shares of restricted stock replacement awards $ 1,850 Cash paid $ 9 Non-credit impaired loans had a fair value of $2,478,144 at acquisition date and contractual balance of $2,573,355. As of acquisition date, the Company expects that an insignificant amount of the contractual balance of these loans will be uncollectible. The difference of $95,211 is recognized into interest income as an adjustment to yield over the life of the loans.

Parent Company Only Financial S

Parent Company Only Financial Statements	12 Months Ended
	Dec. 31, 2020
Condensed Financial Information Disclosure [Abstract]
Parent Company Only Financial Statements	Parent Company Only Financial Statements The following balance sheets, statements of income and statements of cash flows for Independent Bank Group, Inc. should be read in conjunction with the consolidated financial statements and the notes thereto. Balance Sheets December 31, Assets 2020 2019 Cash and cash equivalents $ 5,482 $ 8,277 Investment in subsidiaries 2,876,171 2,588,857 Investment in trusts 1,724 1,724 Other assets 3,849 3,355 Total assets $ 2,887,226 $ 2,602,213 Liabilities and Stockholders' Equity Other borrowings $ 312,175 $ 202,251 Junior subordinated debentures 54,023 53,824 Other liabilities 5,657 6,365 Total liabilities 371,855 262,440 Stockholders' equity: Preferred stock — — Common stock 431 430 Additional paid-in capital 1,934,807 1,926,359 Retained earnings 543,800 393,674 Accumulated other comprehensive income 36,333 19,310 Total stockholders' equity 2,515,371 2,339,773 Total liabilities and stockholders' equity $ 2,887,226 $ 2,602,213 Statements of Income Years Ended December 31, 2020 2019 2018 Interest expense: Interest on other borrowings $ 12,446 $ 11,561 $ 8,390 Interest on junior subordinated debentures 2,162 3,028 1,609 Total interest expense 14,608 14,589 9,999 Noninterest income: Dividends from subsidiaries 83,314 105,877 39,841 Other — 1 14 Total noninterest income 83,314 105,878 39,855 Noninterest expense: Salaries and employee benefits 8,346 7,653 6,318 Professional fees 202 264 332 Acquisition expense, including legal 16,225 33,445 6,157 Other 2,424 2,562 1,611 Total noninterest expense 27,197 43,924 14,418 Income before income tax benefit and equity in undistributed income of subsidiaries 41,509 47,365 15,438 Income tax benefit 9,410 11,066 5,541 Income before equity in undistributed income of subsidiaries 50,919 58,431 20,979 Equity in undistributed income of subsidiaries 150,290 134,305 107,280 Net income $ 201,209 $ 192,736 $ 128,259 Statements of Cash Flows Years Ended December 31, 2020 2019 2018 Cash flows from operating activities: Net income $ 201,209 $ 192,736 $ 128,259 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed net income of subsidiaries (150,290) (134,305) (107,280) Amortization of discount and origination costs on borrowings 720 633 633 Stock based compensation expense 8,450 7,808 6,062 Excess tax expense on restricted stock vested 243 21 (646) Deferred tax expense 96 2,165 1,054 Net change in other assets (590) 1,863 6,918 Net change in other liabilities (952) (64) 1,130 Net cash provided by operating activities 58,886 70,857 36,130 Cash flows from investing activities: Capital investment in subsidiaries (120,000) — — Cash acquired in connection with acquisition — 339 7,425 Cash paid in connection with acquisition — (9) (31,016) Net cash provided by (used in) financing activities (120,000) 330 (23,591) Cash flows from financing activities: Proceeds from other borrowings 148,653 65,000 — Repayments of other borrowings (39,250) (40,500) — Proceeds from exercise of common stock warrants — — 2,533 Offering costs paid in connection with acquired bank — (804) (209) Repurchase of common stock (5,819) (51,659) — Dividends paid (45,265) (43,302) (15,908) Net cash provided by (used in) financing activities 58,319 (71,265) (13,584) Net change in cash and cash equivalents (2,795) (78) (1,045) Cash and cash equivalents at beginning of year 8,277 8,355 9,400 Cash and cash equivalents at end of year $ 5,482 $ 8,277 $ 8,355

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Line of credit agreement On January 17, 2021, the Company's $100,000 unsecured revolving line of credit was renewed and matures on January 17, 2022. As of March 1, 2021, the Company has no borrowings against its revolving line of credit. Declaration of dividends On January 28, 2021, the Company declared a quarterly cash dividend in the amount of $0.30 per share of common stock to the stockholders of record on February 11, 2021. The dividend totaling $12,954 was paid on February 25, 2021.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of presentation: The accompanying consolidated financial statements include the accounts of IBG and all other entities in which IBG has controlling financial interest. All material intercompany transactions and balances have been eliminated in consolidation. In addition, the Company wholly-owns nine statutory business trusts that were formed for the purpose of issuing trust preferred securities and do not meet the criteria for consolidation (See Note 12, Junior Subordinated Debentures ). Accounting standards codification: The Financial Accounting Standards Board's (FASB) Accounting Standards Codification (ASC) is the officially recognized source of authoritative U.S. generally accepted accounting principles (GAAP) applicable to all public and non-public non-governmental entities. Rules and interpretive releases of the SEC under the authority of federal securities laws are also sources of authoritative GAAP for SEC registrants. All other accounting literature is considered non-authoritative. Citing particular content in the ASC involves specifying the unique numeric path to the content through the Topic, Subtopic, Section and Paragraph structure.
Segment Reporting	Segment reporting: The Company has one reportable segment. The Company’s chief operating decision-maker uses consolidated results to make operating and strategic decisions.
Reclassifications	Reclassifications: Certain prior period financial statement and disclosure amounts have been reclassified to conform to current period presentation. The reclassifications have no effect on net income or stockholders' equity as previously reported.
Use of estimates	Use of estimates: The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect certain reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Accordingly, actual results could differ from those estimates. The material estimates included in the financial statements relate to the allowance for loan losses, the valuation of goodwill and valuation of assets and liabilities acquired in business combinations.
Cash and cash equivalents	Cash and cash equivalents: For the purposes of reporting cash flows, cash and cash equivalents include cash on hand, amounts due from banks and federal funds sold. All highly liquid investments with an initial maturity of less than ninety days are considered to be cash equivalents. The Company maintains deposits with other financial institutions in amounts that exceed FDIC insurance coverage. The Company's management monitors the balance in these accounts and periodically assesses the financial condition of the other financial institutions. The Company has not experienced any losses in such accounts and believes it is not exposed to any significant credit risks on cash or cash equivalents.
Certificates of deposit	Certificates of deposit: Certificates of deposit are FDIC insured deposits in other financial institutions that mature within 18 months and are carried at cost.
Securities	Securities: Securities classified as available for sale are those debt securities that the Company intends to hold for an indefinite period of time, but not necessarily to maturity. Any decision to sell a security classified as available for sale would be based on various factors, including significant movements in interest rates, changes in the maturity mix of the Company's assets and liabilities, liquidity needs, regulatory capital considerations and other similar factors. Securities available for sale are reported at fair value with unrealized gains or losses reported as a separate component of other comprehensive income, net of tax. The amortization of premiums and accretion of discounts, computed by the interest method generally over their contractual lives, are recognized in interest income. Premiums on callable securities are amortized to their earliest call date. Prior to the adoption of a new accounting standard in 2019, as further discussed in Note 2, Recent Accounting Pronouncements , premiums on callable securities were amortized to their respective maturity dates unless such securities were included in pools for the purposes of assessing prepayment expectations. Realized gains or losses, determined on the basis of the cost of specific securities sold, are included in earnings on the trade date. In estimating other than temporary impairment losses, management considers (1) the length of time and the extent to which the fair value has been less than cost, (2) the financial condition and near-term prospects of the issuer, and (3) the intent of the Company to retain its investment and whether it is more likely than not the Company will be required to sell its investment before its anticipated recovery in fair value. When the Company does not intend to sell the security, and it is more likely than not that it will not have to sell the security before recovery of its cost basis, it will recognize the credit component of an other than temporary impairment of a debt security in earnings and the remaining portion in other comprehensive income.
Loans held for sale	Loans held for sale: The Company originates residential mortgage loans that may subsequently be sold to unaffiliated third parties. The Company elected the fair value option for certain residential mortgage loans held for sale originated after July 1, 2018 in accordance with ASC 825, Financial Instruments. This election allows for a more effective offset of the changes in fair values of the loans and the derivative instruments used to economically hedge them without the burden of complying with the requirements for hedge accounting under ASC 815, Derivatives and Hedging . The Company has not elected the fair value option for other residential mortgage loans held for sale primarily because they are not economically hedged using derivative instruments. Mortgage loans originated and intended for sale not recorded under the fair value option are carried at the lower of aggregate cost or fair value, as determined by aggregate outstanding commitments from investors. Net unrealized losses, if any, are recognized through a valuation allowance by charges to income. All mortgage loans held for sale are sold without servicing rights retained. Gains and losses on sales of loans are recognized in noninterest income at settlement dates and are determined by the difference between the sales proceeds and the carrying value of the loans.
Acquired loans	Acquired loans: Acquired loans from the transactions accounted for as a business combination include both nonperforming loans with evidence of credit deterioration since their origination date and performing loans. The Company is accounting for the nonperforming loans acquired in accordance with ASC 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality . The performing loans are being accounted for under ASC 310-20, Nonrefundable Fees and Other Costs , with the related difference in the initial fair value and unpaid principal balance (the discount) recognized as interest income on a level yield basis over the life of the loan. At the date of the acquisition, the acquired loans are recorded at their fair value with no valuation allowance. Purchased credit impaired loans are accounted for individually or aggregated into pools of loans based on common risk. The Company estimates the amount and timing of undiscounted expected cash flows for each loan, and the expected cash flows in excess of fair value is recorded as interest income over the remaining life of the loan (accretable yield). The excess of the loan's contractual principal and interest over expected cash flows is not recorded (nonaccretable difference). Over the life of the loan, expected cash flows continue to be estimated. If the expected cash flows decrease, an impairment loss is recorded. If the expected cash flows increase, it is recognized as part of future interest income.
Loans, net	Loans, net: Loans that management has the intent and ability to hold for the foreseeable future or until maturity or pay-off are reported at their outstanding principal balance, net of unearned interest, purchase premiums and discounts, deferred loan fees or costs and an allowance for loan losses. Loan origination fees, net of direct origination costs, are deferred and recognized as an adjustment to the related loan yield using the effective interest method without anticipating prepayments. Prior to the year ended December 31, 2019, fees and costs associated with originating loans were generally recognized in the period they were incurred. Management believes that not deferring such fees and costs did not materially affect the financial position or results of operations of the Company.
Allowance for loan losses	Allowance for loan losses: The allowance for loan losses is maintained at a level considered adequate by management to provide for probable loan losses. The allowance is increased by provisions charged to expense. Loans are charged against the allowance for loan losses when management believes that collectability of the principal is unlikely. Subsequent recoveries, if any, are credited to the allowance. The provision for loan losses is the amount, which, in the judgment of management, is necessary to establish the allowance for loan losses at a level that is adequate to absorb known and inherent risks in the loan portfolio. The allowance is derived from the following two components: 1) allowances established on individual impaired loans, which are based on a review of the individual characteristics of each loan, including the customer’s ability to repay the loan, the underlying collateral values and the industry the customer operates and 2) allowances based on actual historical loss experience for the last three years for similar types of loans in the Company’s loan portfolio adjusted for primarily changes in the lending policies and procedures; collection, charge-off and recovery practices; nature and volume of the loan portfolio; change in value of underlying collateral; volume and severity of nonperforming loans; existence and effect of any concentrations of credit and the level of such concentrations and current, national and local economic and business conditions. This second component also includes an unallocated allowance to cover uncertainties that could affect management’s estimate of probable losses. The unallocated allowance reflects the imprecision inherent in the underlying assumptions used in the methodologies for estimating this component. The Company’s management continually evaluates the allowance for loan losses determined from the allowances established on individual loans and the amounts determined from historical loss percentages adjusted for the qualitative factors above. Should any of the factors considered by management change, the Company’s estimate of loan losses could also change and would affect the level of future provision expense. While the calculation of the allowance for loan losses utilizes management’s best judgment and all the information available, the adequacy of the allowance for loan losses is dependent on a variety of factors beyond the Company’s control, including, among other things, the performance of the entire loan portfolio, the economy, changes in interest rates and the view of regulatory authorities towards loan classifications.
Premises and equipment, net	Premises and equipment, net: Land is carried at cost. Bank premises, furniture and equipment and aircraft are carried at cost, less accumulated depreciation computed principally by the straight-line method over the estimated useful lives of the assets, which range from three Leasehold improvements are carried at cost and are depreciated over the shorter of the estimated useful life or the lease period.
Software	Software: Costs incurred in connection with development or purchase of internal use software and cloud computing arrangements, including in-substance software licenses, are capitalized. Amortization is computed on a straight-line basis over the estimated useful life of the asset, which generally ranges from one
Leases	Leases: On January 1, 2019, the Company adopted ASU 2016-02, Leases (Topic 842), as further explained below and in Note 2, Recent Accounting Pronouncements . For operating leases with a term greater than one year, the Company recognizes operating right-of-use (ROU) lease assets and operating lease liabilities, which are recorded in other assets and other liabilities, respectively, in the consolidated balance sheets. The Company determines if an arrangement is a lease at inception. Operating ROU lease assets and related liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As the Company's leases do not provide an implicit rate, the Company uses its incremental borrowing rate referenced to the Federal Home Loan Bank Secure Connect advance rates for borrowings of similar terms in determining the present value of lease payments. The operating ROU lease asset also includes any lease pre-payments made and excludes lease incentives. The Company's lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company has lease agreements with lease and non-lease components, which the Company has elected to account for separately as the non-lease component amounts are readily determinable under most leases.
Long-term assets	Long-term assets: Premises and equipment and other long-term assets are reviewed for impairment when events indicate that their carrying amount may not be recoverable from future undiscounted cash flows. If impaired, the assets are recorded at fair value.
Other real estate owned	Other real estate owned: Real estate properties acquired through, or in lieu of, loan foreclosure are initially recorded at fair value less estimated selling costs at the date of foreclosure, establishing a new cost basis. After foreclosure, valuations are periodically performed by management and the real estate is carried at the lower of carrying amount or fair value less cost to sell.
Goodwill and other intangible assets, net	Goodwill and other intangible assets, net: Goodwill represents the excess of costs over fair value of net assets of businesses acquired. Goodwill is tested for impairment annually on December 31 or on an interim basis if an event triggering impairment may have occurred. On January 1, 2020, ASU 2017-04, Intangibles - Goodwill and Other (Topic 350) - Simplifying the Test for Goodwill Impairment became effective for the Company as further explained in Note 2, Recent Accounting Pronouncements . Under the new guidance, if a reporting unit’s carrying amount exceeds its fair value, an entity will record an impairment charge based on that difference. During the period ended March 31, 2020, the economic turmoil and market volatility resulting from the COVID-19 crisis resulted in a substantial decrease in the Company's stock price and market capitalization. Management believed such decrease was a triggering indicator requiring an interim goodwill impairment quantitative analysis. Under the new simplified guidance, the Company's estimated fair value to a market participant as of March 31, 2020, exceeded its carrying amount resulting in no impairment charge for the period. Over subsequent periods, the Company's stock price and market capitalization has continued to increase and management's future projections have not materially changed. As of December 31, 2020, the fair value of the Company’s stock price and calculated market capitalization exceeds its carrying value. Core deposit intangibles and other acquired customer relationship intangibles arising from bank acquisitions are amortized on a straight-line basis over their estimated useful lives of ten years and thirteen years, respectively. Other intangible assets are tested for impairment whenever events or changes in circumstances indicate the carrying amount of the assets may not be recoverable from future undiscounted cash flows.
Restricted stock	Restricted stock : The Bank is a member of the FHLB system. Members are required to own a certain amount of stock based on the level of borrowings and other factors, and may invest in additional amounts. FHLB of Dallas and other restricted stock do not have readily determinable fair values as ownership is restricted and they lack a ready market. As a result, these stocks are carried at cost and evaluated periodically by management for impairment. Both cash and stock dividends are reported as income.
Bank-owned life insurance	Bank-owned life insurance: Bank-owned life insurance is recorded at the amount that can be realized under the insurance contracts at the balance sheet date, which is the cash surrender value adjusted for other charges or other amounts due that are probable at settlement. Changes in the net cash surrender value of the policies, as well as insurance proceeds received are reflected in noninterest income.
Income taxes	Income taxes: Income tax expense is the total of the current year income tax due or refundable and the change in deferred tax assets and liabilities (excluding deferred tax assets and liabilities related to business combinations or components of other comprehensive income). Deferred tax assets and liabilities are the expected future tax amounts for the temporary differences between carrying amounts and tax bases of assets and liabilities, computed using enacted tax rates. The effect of a change in tax rates on deferred assets and liabilities is recognized in income taxes during the period that includes the enactment date. A valuation allowance, if needed, reduces deferred tax assets to the expected amount more likely than not to be realized. Realization of deferred tax assets is dependent upon the level of historical income, prudent and feasible tax planning strategies, reversals of deferred tax liabilities and estimates of future taxable income.
Loan commitments and related financial instruments	Loan commitments and related financial instruments: In the ordinary course of business, the Company has entered into certain off-balance-sheet financial instruments consisting of commitments to extend credit, commercial letters of credit, and standby letters of credit. Such financial instruments are recorded in the financial statements when they are funded or related fees are incurred or received.
Stock based compensation	Stock based compensation: Compensation cost is recognized for restricted stock awards/stock units issued to employees based on the market price of the Company's common stock on the grant date. Stock-based compensation expense is generally recognized using the straight-line method over the requisite service period for time-based awards. Compensation expense for performance stock units is recognized over the service period of the award based upon the probable number of units expected to vest. The impact of forfeitures of stock-based payment awards on compensation expense is recognized as forfeitures occur.
Transfers of financial assets	Transfers of financial assets: Transfers of financial assets are accounted for as sales, when control over the assets has been relinquished. Control over transferred assets is deemed to be surrendered when the assets have been isolated from the Company, the transferee obtains the right (free of conditions that constrain it from taking advantage of that right) to pledge or exchange the transferred assets, and the Company does not maintain effective control over the transferred assets through an agreement to repurchase them before their maturity.
Advertising costs	Advertising costs: Advertising costs are expensed as incurred.
Business combinations	Business combinations: The Company applies the acquisition method of accounting for business combinations. Under the acquisition method, the acquiring entity in a business combination recognizes 100% of the assets acquired and liabilities assumed at their acquisition date fair values. Management utilizes valuation techniques appropriate for the asset or liability being measured in determining these fair values. Any excess of the purchase price over amounts allocated to assets acquired, including identifiable intangible assets, and liabilities assumed is recorded as goodwill. Where amounts allocated to assets acquired and liabilities assumed is greater than the purchase price, a bargain purchase gain is recognized. Adjustments identified during the measurement period are recognized in the reporting period in which the adjustment amounts are determined. Acquisition-related costs are expensed as incurred.
Comprehensive income	Comprehensive income: Accounting principles generally require that recognized revenue, expenses, gains and losses be included in net income. Although certain changes in assets and liabilities, such as unrealized gains and losses on available for sale securities, are reported as a separate component of the equity section of the balance sheet, such items, along with net income, are components of comprehensive income. Gains and losses on available for sale securities are reclassified to net income as the gains or losses are realized upon sale of the securities. The credit component of other than temporary impairment charges are reclassified to net income at the time of the charge.
Fair values of financial instruments	Fair values of financial instruments: Accounting standards define fair value, establish a framework for measuring fair value in U.S. generally accepted accounting principles, and require certain disclosures about fair value measurements (see Note 18, Fair Value Measurements ). In general, fair values of financial instruments are based upon quoted market prices, where available. If such quoted market prices are not available, fair value is based upon 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. These adjustments may include amounts to reflect counterparty credit quality and the Company's creditworthiness, among other things, as well as unobservable parameters. Any such valuation adjustments are applied consistently over time. The fair value of an asset or liability is the price that would be received to sell that asset or paid to transfer that liability in an orderly transaction occurring in the principal market (or most advantageous market in the absence of a principal market) for such asset or liability. In estimating fair value, the Company utilizes valuation techniques that are consistent with the market approach, the income approach and/or the cost approach. Such valuation techniques are consistently applied. Inputs to valuation techniques include the assumptions that market participants would use in pricing an asset or liability. ASC Topic 820, Fair Value Measurements and Disclosures , 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 might 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 (such as interest rates, volatilities, prepayment speeds, credit risks, etc.) or inputs that are derived principally from or corroborated by market data by correlation or other means. Level 3 Inputs – Unobservable inputs for determining the fair values of assets or liabilities that reflect an entity’s own assumptions about the assumptions that market participants would use in pricing the assets or liabilities. The Company elected the fair value option for certain residential mortgage loans held for sale in accordance with ASC 825, Financial Instruments. This election allows for a more effective offset of the changes in fair values of the loans and the derivative instruments used to economically hedge them without the burden of complying with the requirements for hedge accounting under ASC 815, Derivatives and Hedging . The Company has not elected the fair value option for other residential mortgage loans held for sale primarily because they are not economically hedged using derivative instruments. See below and Note 19, Derivative Financial Instruments , for additional information. Investment securities Securities classified as available for sale are reported at fair value utilizing Level 1 and Level 2 inputs. Securities are classified within Level 1 when quoted market prices are available in an active market. Inputs include securities that have quoted prices in active markets for identical assets. For securities utilizing Level 2 inputs, the Company obtains fair value measurements from an independent pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury and other yield curves, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the security’s terms and conditions, among other things. Loans held for sale Certain mortgage loans held for sale are measured at fair value on a recurring basis due to the Company's election to adopt fair value accounting treatment for those loans originated for which the Company has entered into certain derivative financial instruments as part of its mortgage banking and related risk management activities. These instruments include interest rate lock commitments and mandatory forward commitments to sell these loans to investors known as forward mortgage-backed securities trades. This election allows for a more effective offset of the changes in fair values of the assets and the mortgage related derivative instruments used to economically hedge them without the burden of complying with the requirements for hedge accounting under ASC 815, Derivatives and Hedging. Mortgage loans held for sale, for which the fair value option was elected, which are sold on a servicing released basis, are valued using a market approach by utilizing either: (i) the fair value of 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 to 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. For mortgage loans held for sale for which the fair value option was elected, the earned current contractual interest payment is recognized in interest income, loan origination costs and fees on fair value option loans are recognized in earnings as incurred and not deferred. The Company has no continuing involvement in any residential mortgage loans sold. Derivatives The estimated fair values of interest rate lock commitments utilize current secondary market prices for underlying loans and estimated servicing value with similar coupons, maturity and credit quality, subject to the anticipated loan funding probability (pull-through rate). The fair value of interest rate lock commitments 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, as the valuations are based on observable market inputs. Forward mortgage-backed securities trades are exchange-traded or traded within highly active dealer markets. In order to determine the fair value of these instruments, the Company utilized the exchange price or dealer market price for the particular derivative contract; therefore these contracts are classified as Level 2. The estimated fair values are subject to change primarily due to changes in interest rates. The Company also enters into certain interest rate derivative positions that are not designated as hedging instruments. The estimated fair value of these commercial loan interest rate swaps are obtained from a pricing service that provides the swaps' unwind value (Level 2 inputs). See Note 19, Derivative Financial Instruments , for more information. Impaired loans (loans which are not expected to repay all principal and interest amounts due in accordance with the original contractual terms) are measured at an observable market price (if available) or at the fair value of the loan’s collateral (if collateral dependent). Fair value of the loan’s collateral is determined by appraisals or independent valuation, which is then adjusted for the estimated costs related to liquidation of the collateral. Management’s ongoing review of appraisal information may result in additional discounts or adjustments to valuation based upon more recent market sales activity or more current appraisal information derived from properties of similar type and/or locale. Therefore, the Company has categorized its impaired loans as Level 3. Other real estate is measured at fair value on a nonrecurring basis (upon initial recognition or subsequent impairment). Other real estate is classified within Level 3 of the valuation hierarchy. When transferred from the loan portfolio, other real estate is adjusted to fair value less estimated selling costs and is subsequently carried at the lower of carrying value or fair value less estimated selling costs. The fair value is determined using an external appraisal process, discounted based on internal criteria. Therefore, the Company has categorized its other real estate as Level 3. The methods and assumptions used by the Company in estimating fair values of financial instruments as disclosed herein in accordance with ASC Topic 825, Financial Instruments, other than for those measured at fair value on a recurring and nonrecurring basis discussed above, are as follows: Cash and cash equivalents: The carrying amounts of cash and cash equivalents approximate their fair value. Certificates of deposit held in other banks: The fair value of certificates of deposit held in other banks is based upon current market rates. Loans held for sale, at cost: The fair value of loans held for sale is determined based upon commitments on hand from investors. Loans: A discounted cash flow model is used to estimate the fair value of the loans. The discounted cash flow approach models the credit losses directly in the projected cash flows, applying various assumptions regarding credit, interest and prepayment risks for the loans based on loan types, payment types and fixed or variable classifications. Federal Home Loan Bank of Dallas and other restricted stock: The carrying value of restricted securities such as stock in the Federal Home Loan Bank of Dallas and Independent Bankers Financial Corporation approximates fair value. Deposits: The fair values disclosed for demand deposits are, by definition, equal to the amount payable on demand at the reporting date (that is their carrying amounts). The carrying amounts of variable-rate certificates of deposit (CDs) approximate their fair values at the reporting date. Fair values for fixed-rate CDs are estimated using a discounted cash flow calculation that applies interest rates currently being offered on certificates to a schedule of aggregated expected monthly maturities on time deposits. Federal Home Loan Bank advances, line of credit and federal funds purchased: The fair value of advances maturing within 90 days approximates carrying value. Fair value of other advances is based on the Company’s current borrowing rate for similar arrangements. Other borrowings: The estimated fair value approximates carrying value for short-term borrowings. The fair value of private subordinated debentures are based upon prevailing rates on similar debt in the market place. The subordinated debentures that are publicly traded are valued based on indicative bid prices based upon market pricing observations in the current market. Junior subordinated debentures: The fair value of junior subordinated debentures is estimated using discounted cash flow analyses based on the published Bloomberg US Financials BB rated corporate bond index yield. Accrued interest: The carrying amounts of accrued interest approximate their fair values. Off-balance sheet instruments: Fair values for off-balance sheet, credit-related financial instruments are based on fees currently charged to enter into similar agreements, taking into account the remaining terms of the agreements and the counterparties' credit standing. The fair value of commitments is not material.
Derivative financial instruments	Derivative financial instruments: The Company enters into certain derivative financial instruments: interest rate lock commitments, forward mortgage-backed securities trades and interest rate swaps. These financial instruments are not designated as hedging instruments and are used for asset and liability management related to the Company's mortgage banking activities and commercial customers' financing needs. All derivatives are carried at fair value in either other assets or other liabilities (see Note 19, Derivative Financial Instruments ) . Through the normal course of business, the Company enters into interest rate lock commitments with consumers to originate mortgage loans at a specified interest rate. 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 manages the changes in fair value associated with changes in interest rates related to interest rate lock commitments by using forward sold commitments known as forward mortgage-backed securities trades. These instruments are typically entered into at the time the interest rate lock commitment is made. The Company also offers certain derivatives products, primarily interest rate swaps, directly to qualified commercial banking customers to facilitate their risk management strategies. The interest rate swap derivative positions relate to transactions in which the Company enters into an interest rate swap with a customer, while at the same time entering into an offsetting interest rate swap with another financial institution. An interest rate swap transaction allows customers to effectively convert a variable rate loan to a fixed rate. In connection with each swap, the Company agrees to pay interest to the customer on a notional amount at a variable interest rate and receive interest from the customer on a similar notional amount at a fixed interest rate. At the same time, the Company agrees to pay another financial institution the same fixed interest rate on the same notional amount and receive the same variable interest rate on the same notional amount.
Mortgage banking	Mortgage banking: This revenue category reflects the Company's mortgage production revenue, including fees and income derived from mortgages originated with the intent to sell, gains on sales of mortgage loans and the initial and subsequent changes in the fair value of the mortgage derivatives. Interest earned on mortgage loans is recorded in interest income.The Company has a mortgage warehouse purchase program providing mortgage inventory financing for residential mortgage loans originated by mortgage banker clients across a broad geographic scale. Proceeds from the sale of mortgages is the primary source of repayment for warehouse inventory financing via approved investor takeout commitments. These loans typically have a very short duration ranging between a few days to 15 days. In some cases, loans to larger mortgage originators may be financed for up to 60 days. These loans are reported as commercial loans since the loans are secured by notes receivable, not real estate.
Revenue recognition	Revenue recognition: ASC Topic 606, R evenue from Contracts with Customers (ASC 606) , establishes principles for reporting information about the nature, amount, timing and uncertainty of revenue and cash flows arising from the entity's contracts to provide goods or services to customers. The core principle requires an entity to recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration that it expects to be entitled to receive in exchange for those goods or services recognized as performance obligations are satisfied. The majority of the Company's revenue-generating transactions are not subject to ASC 606, including revenue generated from financial instruments, such as loans, letters of credit, and investment securities, as well as revenue related to mortgage banking activities, and BOLI, as these activities are subject to other accounting guidance. Descriptions of revenue-generating activities that are within the scope of ASC 606, and are presented in the accompanying Consolidated Statements of Income as components of noninterest income, are as follows: • Service charges on deposit accounts - these represent general service fees for monthly account maintenance and activity or transaction-based fees and consist of transaction-based revenue, time-based revenue (service period), item-based revenue or some other individual attribute-based revenue. Revenue is recognized when the performance obligation is completed which is generally monthly for account maintenance services or when a transaction has been completed (such as a wire transfer). Payment for such performance obligations are generally received at the time the performance obligations are satisfied. • Investment management and trust - includes income related to providing investment management and trust services to customers under investment management and trust contracts. Also included are fees received from a third party broker-dealer as part of a revenue-sharing agreement for fees earned from customers that are referred to a third party. The investment management fees and referral fees are billed and paid on a quarterly basis and recognized ratably throughout the quarter as performance obligations are satisfied. • Gains/losses on the sale of other real estate owned - generally recognized when the performance obligation is complete which is typically at delivery of control over the property to the buyer at time of each real estate closing. • Other noninterest income - includes the Company's correspondent bank earnings credit, mortgage warehouse purchase program fees, acquired loan recoveries, other deposit fees, and merchant interchange income. The majority of these fees in other noninterest income are not subject to the requirements of ASC 606. The other deposit fees and merchant interchange income are in the scope of ASC 606, and payment for such performance obligations are generally received at the time the performance obligations are satisfied. The Company has made no significant judgments in applying the revenue guidance prescribed in ASC 606 that affect the determination of the amount and timing of revenue from the above-described contracts with customers.
Subsequent events	Subsequent events: Companies are required to evaluate events and transactions that occur after the balance sheet date but before the date the financial statements are issued. They must recognize in the financial statements the effect of all events or transactions that provide additional evidence of conditions that existed at the balance sheet date, including the estimates inherent in the financial statement preparation process. Entities shall not recognize the impact of events or transactions that provide evidence about conditions that did not exist at the balance sheet date but arose after that date. The Company has evaluated subsequent events through the date of filing these financial statements with the Securities and Exchange Commission (SEC) and noted no subsequent events requiring financial statement recognition or disclosure, except as disclosed in Note 24.
Earnings per share	Earnings per share: Basic earnings per common share is calculated as net income available to common shareholders divided by the weighted average number of common shares outstanding during the period. The unvested share-based payment awards that contain rights to nonforfeitable dividends are considered participating securities for this calculation. The participating nonvested common stock was not included in dilutive shares as it was anti-dilutive for the years ended December 31, 2020, 2019 and 2018.
Recent accounting pronouncements	Recent Accounting Pronouncements Adoption of new accounting standards Delayed implementation of new accounting standard: ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments and subsequent updates . ASU 2016-13 requires a new credit loss methodology, the current expected credit loss (CECL) model, which requires the recognition of an allowance for lifetime expected credit losses on loans, held-to-maturity debt securities and other receivables measured at amortized cost at the time the financial asset is originated or acquired. Credit losses will be immediately recognized through net income; the amount recognized will be based on the current estimate of contractual cash flows not expected to be collected over the financial asset’s contractual term. ASU 2016-13 became effective for the Company on January 1, 2020. 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 financial institutions to delay the implementation of ASU 2016-13 until the earlier of the termination date of the national emergency declaration by the President or December 31, 2020. Due to the uncertainty of the economic forecast resulting from the coronavirus (COVID-19) pandemic and the potential impact of the government economic stimulus measures, the Company delayed its implementation of ASU 2016-13. On December 27, 2020, the Consolidated Appropriations Act, 2021 (Act 2021), was signed into law which further extended the implementation date of CECL to the earlier of the first day of the entity’s fiscal year that begins after the date on which the COVID-19 national emergency terminates or January 1, 2022. With regard to Act 2021 amendments, the SEC staff indicated it would not object to a registrant early adopting on December 31, 2020, retrospective to January 1, 2020, or January 1, 2021, effective as of January 1, 2021. Under this guidance, the Company is electing to adopt ASU 2016-13 with an effective implementation date of January 1, 2021. As a result, for 2020, the Company has calculated and recorded its provision for loan losses under the incurred loss model that existed prior to ASU 2016-13. Upon adoption, the Company expects to increase its combined allowance for loan losses and reserves for unfunded commitments by approximately $68,000 to $84,000, of which approximately $13,000 is attributable to purchase credit deteriorated loans. The Company will apply the standard's provisions as a cumulative-effect adjustment to retained earnings. The expected increase in the allowance for loan losses is a result of changing from an incurred loss model, which encompasses allowances for current known and inherent losses within the portfolio, to a CECL model, which encompasses allowances for losses expected to be incurred over the life of the portfolio. The majority of the increase is attributable to applying the CECL model to the Company's acquired loans, which, under prior guidance, were recorded at fair value without an allowance at acquisition date. Furthermore, ASU 2016-13 necessitates that the Company establish an allowance for expected credit losses for certain debt securities and other financial assets; however, such allowances, if any, are not expected to be significant. ASU 2017-04, Intangibles - Goodwill and Other (Topic 350) - Simplifying the Test for Goodwill Impairment. This ASU simplifies the accounting for goodwill impairment for all entities by requiring impairment charges to be based on the first step in today’s two-step impairment test. Under the new guidance, if a reporting unit’s carrying amount exceeds its fair value, an entity will record an impairment charge based on that difference. The impairment charge will be limited to the amount of goodwill allocated to that reporting unit. The standard eliminates today’s requirement to calculate a goodwill impairment charge using Step 2, which requires an entity to calculate any impairment charge by comparing the implied fair value of goodwill with its carrying amount. ASU 2017-04 became effective for the Company on January 1, 2020, and did not have a significant impact on its financial statements. ASU 2018-13, Fair Value Measurement (Topic 820) - Changes to the Disclosure Requirements for Fair Value Measurement. This ASU modifies the disclosure requirements on fair value measurements by requiring that Level 3 fair value disclosures include the range and weighted average of significant unobservable inputs used to develop those fair value measurements. For certain unobservable inputs, an entity may disclose other quantitative information in lieu of the weighted average if the entity determines that other quantitative information would be a more reasonable and rational method to reflect the distribution of unobservable inputs used to develop Level 3 fair value measurements. ASU 2018-13 became effective for the Company on January 1, 2020 and did not have a significant impact on its financial statements and disclosures. ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40) - Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. This ASU aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal use software license). The accounting for the service element of a hosting arrangement that is a service contract is not affected by these amendments. This ASU became effective for the Company on January 1, 2020 and did not have a significant impact on its financial statements and disclosures. ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting and subsequent updates . This ASU provides temporary optional guidance to ease the potential burden in accounting for reference rate reform. The new guidance provides optional expedients and exceptions for applying generally accepted accounting principles to contract modifications and hedging relationships, subject to meeting certain criteria, that reference LIBOR or another reference rate expected to be discontinued. The ASU is intended to help stakeholders during the global market-wide reference rate transition period. This ASU became effective upon issuance and generally can be applied through December 31, 2022. The Company anticipates this ASU will simplify any modifications it executes and is not expected to have a significant impact on its financial statements and disclosures. ASU 2016-02, Leases (Topic 842) and subsequent updates . This ASU, among other things, requires lessees to recognize a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. Under this guidance, lessor accounting is largely unchanged. This ASU became effective for annual and interim periods for the Company on January 1, 2019. The Company adopted the standard by applying the alternative transition method whereby comparative periods were not restated, and an immaterial cumulative effect adjustment to the opening balance of retained earnings was recognized as of January 1, 2019. The Company also elected the ASU’s package of three practical expedients, which allowed the Company to forego a reassessment of (i) whether any expired or existing contracts are or contain leases, (ii) the lease classification for any expired or existing leases and (iii) the initial direct costs for any existing leases. The Company also elected not to apply the recognition requirements of the ASU to any short-term leases (as defined by related accounting guidance) and will account for lease and non-lease components separately. The adoption of this standard resulted in the Company recognizing lease right-of-use assets and related lease liabilities totaling $38,812 and $33,953, respectively, as of January 1, 2019. The difference between the lease assets and the lease liabilities was $4,949 of prepaid rent, which was reclassified to lease assets, and the remainder, net of the deferred tax impact, was recorded as an adjustment reducing retained earnings in the amount of $70. The adoption of this ASU did not have a significant impact on the Company’s consolidated statement of income. See Note 1, Summary of Significant Accounting Policies , and Note 13, Leases , for required disclosures. ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20), Premium Amortization on Purchased Callable Debt Securities . This ASU requires certain premiums on callable debt securities to be amortized to the earliest call date. The amortization period for callable debt securities purchased at a discount is not impacted. Under current GAAP, premiums on callable debt securities are generally amortized over the contractual life of the security. ASU 2017-08 became effective for the Company on January 1, 2019 and, upon adoption, the Company recognized a cumulative effect adjustment reducing retained earnings by $856, net of the deferred tax impact, but otherwise did not have a significant impact to the Company's consolidated financial statements and disclosures. ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. The amendments in this update allow reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act (TCJA) which was signed into law on December 22, 2017. The Company elected to early adopt ASU 2018-02 in the first quarter of 2018 and apply the guidance to the beginning of the period, effective January 1, 2018 . The impact of adopting the amendment resulted in a cumulative effect adjustment to the consolidated balance sheet as of January 1, 2018 to reclassify approximately $233 of tax expense from accumulated other comprehensive loss to retained earnings as reflected in the accompanying Consolidated Statements of Changes in Stockholders' Equity. Newly issued but not yet effective accounting standards ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. The guidance issued in this update simplifies the accounting for income taxes by eliminating certain exceptions to the guidance in ASC 740 related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition for 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 will be effective for the Company on January 1, 2021, with early adoption permitted, and is not expected to have a significant impact on our financial statements.
Nonaccrual loan and lease status	The accrual of interest is discontinued on a loan when management believes that, after considering collection efforts and other factors, the borrower's financial condition is such that collection of interest is doubtful. All interest accrued but not collected for loans that are placed on nonaccrual status or charged-off is reversed against interest income. Cash collections on nonaccrual loans are generally credited to the loan receivable balance, and no interest income is recognized on those loans until the principal balance has been collected. Loans are returned to accrual status when all the principal and interest amounts contractually due are brought current and future payments are reasonably assured.
Impaired loan and lease receivable	Impaired loans are those loans where it is probable that all amounts due according to contractual terms of the loan agreement will not be collected. The Company has identified these loans through its normal loan review procedures. Impaired loans are measured based on 1) the present value of expected future cash flows discounted at the loan's effective interest rate; 2) the loan's observable market price; or 3) the fair value of collateral if the loan is collateral dependent. Substantially all of the Company’s impaired loans are measured at the fair value of the collateral. In limited cases, the Company may use other methods to determine the level of impairment of a loan if such loan is not collateral dependent.
Loan charge off amounts	The Company will charge-off that portion of any loan which management considers a loss. Commercial and real estate loans are generally considered for charge-off when exposure beyond collateral coverage is apparent and when no further collection of the loss portion is anticipated based on the borrower’s financial condition.
Trouble debt restructuring	The restructuring of a loan is considered a “troubled debt restructuring” (TDR) if both 1) the borrower is experiencing financial difficulties and 2) the creditor has granted a concession. Concessions may include interest rate reductions or below market interest rates, principal forgiveness, extending amortization and other actions intended to minimize potential losses. A TDR loan is identified as impaired and measured for credit impairment as of each reporting period in accordance with the guidance in Accounting Standards Codification ASC 310-10-35.
Loans past due	Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due.
Share repurchase plan	Stock repurchase program: From time to time, the Company's board of directors has authorized stock repurchase programs which allow the Company to purchase its common stock generally over a one-year period at various prices in the open market or in privately negotiated transactions. On October 22, 2020, the Company's board of directors authorized a $150,000 stock repurchase program allowing the Company to purchase shares of its common stock through October 31, 2021. Under this program, the Company repurchased 109,548 shares at a total cost of $5,660 as of December 31, 2020. Under prior stock repurchase programs, the Company repurchased 897,738 at a total cost of $49,048 during 2019 and none during 2018. In July 2019, the federal bank regulators adopted final rules that, among other things, eliminated the standalone prior approval requirement for any repurchase of common stock. However, the Company remains subject to a Federal Reserve Board guideline that requires consultation with the Federal Reserve regarding plans for share repurchases on a quarterly basis. The Company’s repurchases of its common stock may be subject to a prior approval or notice requirement under other regulations, policies or supervisory expectations of the Federal Reserve Board. Any redemption or repurchase of preferred stock or subordinated debt remains subject to the prior approval of the Federal Reserve Board.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Earnings Per Share	The following table presents a reconciliation of net income available to common shareholders and the number of shares used in the calculation of basic and diluted earnings per common share. Years Ended December 31, 2020 2019 2018 Basic earnings per share: Net income $ 201,209 $ 192,736 $ 128,259 Less: Undistributed earnings allocated to participating securities 1,311 971 976 Dividends paid on participating securities 380 281 139 Net income available to common shareholders $ 199,518 $ 191,484 $ 127,144 Weighted average basic shares outstanding 42,754,606 42,964,393 29,341,843 Basic earnings per share $ 4.67 $ 4.46 $ 4.33 Diluted earnings per share: Net income available to common shareholders $ 199,518 $ 191,484 $ 127,144 Total weighted average basic shares outstanding 42,754,606 42,964,393 29,341,843 Total weighted average diluted shares outstanding 42,754,606 42,964,393 29,341,843 Diluted earnings per share $ 4.67 $ 4.46 $ 4.33 Anti-dilutive participating securities 58,359 73,546 114,087

Statement of Cash Flows (Tables

Statement of Cash Flows (Tables)	12 Months Ended
	Dec. 31, 2020
Supplemental Cash Flow Elements [Abstract]
Other Supplemental Cash Flow Information	Other supplemental cash flow information is presented below: Years Ended December 31, 2020 2019 2018 Cash transactions: Interest expense paid $ 97,246 $ 144,775 $ 79,509 Income taxes paid $ 54,842 $ 40,504 $ 25,109 Noncash transactions: Transfers of loans to other real estate owned $ 5,239 $ 544 $ 410 Loans to facilitate the sale of other real estate owned $ 2,039 $ 517 $ — Securities purchased, not yet settled $ — $ 9,975 $ — Transfers of loans held for investment to loans held for sale $ — $ 83,526 $ — Right-of-use assets obtained in exchange for lease liabilities $ 105 $ 35,553 $ — Loans purchased, not yet settled $ 9,442 $ — $ — Transfer of bank premises to other real estate $ — $ 7,896 $ — Transfer of repurchase agreements to deposits $ — $ 8,475 $ — Supplemental schedule of noncash investing activities from a branch sale during 2019 is as follows: Year ended December 31, 2019 Noncash assets transferred: Loans, including accrued interest $ 796 Premises and equipment 94 Other assets 2 Total assets $ 892 Noncash liabilities transferred: Deposits, including interest $ 27,721 Other liabilities 27 Total liabilities $ 27,748 Cash and cash equivalents transferred in branch sales $ 206 Deposit premium received $ 1,386 Cash paid to buyer, net of deposit premium $ 24,957 Supplemental schedule of noncash investing activities from sale of trust business during 2019 is as follows: Year ended December 31, 2019 Noncash assets transferred: Customer relationship intangible assets, net $ 2,939 Other assets 11 Total assets $ 2,950 Net cash received from sale $ 4,269 Supplemental schedule of noncash investing activities from acquisitions is as follows: Years ended December 31, 2020 2019 2018 Noncash assets acquired Certificates of deposit held in other banks $ — $ 262 $ — Securities available for sale — 561,052 24,721 Restricted stock — 27,794 3,357 Loans — 2,789,868 651,769 Premises and equipment — 65,786 4,863 Other real estate owned — 1,829 — Goodwill — 272,224 100,339 Other intangible assets — 71,518 7,537 Bank owned life insurance — 80,837 8,181 Other assets — 31,987 6,385 Total assets acquired $ — $ 3,903,157 $ 807,152 Noncash liabilities assumed: Deposits $ — $ 3,108,810 $ 593,078 Repurchase agreements — 8,475 — FHLB advances — 142,653 60,000 Other borrowings — 40,000 — Junior subordinated debentures — 25,774 — Other liabilities — 15,477 10,518 Total liabilities assumed $ — $ 3,341,189 $ 663,596 Cash and cash equivalents acquired from acquisitions $ — $ 39,913 $ 44,723 Cash paid to shareholders of acquired banks $ — $ 9 $ 31,016 Fair value of common stock issued to shareholders of acquired banks $ — $ 601,872 $ 157,263

Securities Available for Sale (

Securities Available for Sale (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Securities, Available-for-sale [Abstract]
Amortized Cost of Securities and Approximate Fair Values	The amortized cost of securities and their approximate fair values at December 31, 2020 and 2019, are as follows: Amortized Gross Gross Fair Securities Available for Sale December 31, 2020 U.S. treasuries $ 43,060 $ 1,648 $ — $ 44,708 Government agency securities 247,764 3,169 (1,916) 249,017 Obligations of state and municipal subdivisions 373,017 20,168 (20) 393,165 Corporate bonds 21,496 608 (2) 22,102 Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 421,916 21,678 (93) 443,501 Other securities 1,200 — — 1,200 $ 1,108,453 $ 47,271 $ (2,031) $ 1,153,693 December 31, 2019 U.S. treasuries $ 48,060 $ 743 $ (7) $ 48,796 Government agency securities 178,953 926 (583) 179,296 Obligations of state and municipal subdivisions 332,715 11,150 (6) 343,859 Corporate bonds 7,011 207 — 7,218 Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 493,915 11,981 (329) 505,567 Other securities 1,200 — — 1,200 $ 1,061,854 $ 25,007 $ (925) $ 1,085,936
Proceeds from Sale, Gross Gains and Losses of Securities Available for Sale	Proceeds from sale of securities available for sale and gross gains and gross losses for the years ended December 31, 2020, 2019 and 2018 were as follows: Years Ended December 31, 2020 2019 2018 Proceeds from sale $ 13,862 $ 192,417 $ 102,647 Gross gains $ 385 $ 306 $ 268 Gross losses $ 3 $ 31 $ 849
Amortized Cost and Estimated Fair Value of Securities Available for Sale by Contractual Maturity	The amortized cost and estimated fair value of securities available for sale at December 31, 2020, by contractual maturity, are shown below. Maturities of mortgage-backed securities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. December 31, 2020 Securities Available for Sale Amortized Fair Due in one year or less $ 39,579 $ 39,943 Due from one year to five years 128,804 135,272 Due from five to ten years 203,387 209,396 Thereafter 314,767 325,581 686,537 710,192 Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 421,916 443,501 $ 1,108,453 $ 1,153,693
Summary of Unrealized Losses and Fair Value Securities in Continuous Unrealized Loss Position	The number of securities, unrealized losses and fair value, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, as of December 31, 2020 and 2019, are summarized as follows: Less Than 12 Months Greater Than 12 Months Total Description of Securities Number of Securities Estimated Unrealized Number of Securities Estimated Unrealized Estimated Unrealized Securities Available for Sale December 31, 2020 Government agency securities 20 $ 112,897 $ (1,916) — $ — $ — $ 112,897 $ (1,916) Obligations of state and municipal subdivisions 2 3,786 (20) — — — 3,786 (20) Corporate bonds 1 998 (2) — — — 998 (2) Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 10 41,344 (93) — — — 41,344 (93) 33 $ 159,025 $ (2,031) — $ — $ — $ 159,025 $ (2,031) December 31, 2019 U.S. treasuries — $ — $ — 2 $ 8,097 $ (7) $ 8,097 $ (7) Government agency securities 13 52,790 (495) 6 15,911 (88) 68,701 (583) Obligations of state and municipal subdivisions 5 2,793 (1) 1 423 (5) 3,216 (6) Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 13 46,512 (317) 1 1,193 (12) 47,705 (329) 31 $ 102,095 $ (813) 10 $ 25,624 $ (112) $ 127,719 $ (925)

Loans, Net and Allowance for _2

Loans, Net and Allowance for Loan Losses (Tables)	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Compositions of Loans	Loans, net at December 31, 2020 and 2019, consisted of the following: December 31, 2020 2019 Commercial $ 3,902,266 $ 2,482,356 Real estate: Commercial 6,096,676 5,872,653 Commercial construction, land and land development 1,245,801 1,236,623 Residential 1,352,465 1,515,227 Single-family interim construction 326,575 378,120 Agricultural 85,014 97,767 Consumer 66,952 32,603 Other 346 621 Total loans 13,076,095 11,615,970 Deferred loan fees, net (10,037) (1,695) Allowance for loan losses (87,820) (51,461) Total loans, net $ 12,978,238 $ 11,562,814
Summary of Activity in Allowance for Loan Losses by Loan Class	The following is a summary of the activity in the allowance for loan losses by loan class for the years ended December 31, 2020, 2019 and 2018: Commercial Commercial Residential Single-Family Agricultural Consumer Other Unallocated Total Year ended December 31, 2020 Balance at beginning of year $ 12,844 $ 33,085 $ 3,678 $ 1,606 $ 332 $ 226 $ 5 $ (315) $ 51,461 Provision for loan losses 20,025 17,769 3,108 632 5 223 493 738 42,993 Charge-offs (5,670) (735) — (82) — (44) (342) — (6,873) Recoveries 112 4 — — — 37 86 — 239 Balance at end of year $ 27,311 $ 50,123 $ 6,786 $ 2,156 $ 337 $ 442 $ 242 $ 423 $ 87,820 Year ended December 31, 2019 Balance at beginning of year $ 11,793 $ 27,795 $ 3,320 $ 1,402 $ 241 $ 186 $ 3 $ 62 $ 44,802 Provision for loan losses 8,670 5,289 498 207 91 71 356 (377) 14,805 Charge-offs (7,709) (3) (140) (3) — (79) (430) — (8,364) Recoveries 90 4 — — — 48 76 — 218 Balance at end of year $ 12,844 $ 33,085 $ 3,678 $ 1,606 $ 332 $ 226 $ 5 $ (315) $ 51,461 Year ended December 31, 2018 Balance at beginning of year $ 10,599 $ 23,301 $ 3,447 $ 1,583 $ 250 $ 205 $ (32) $ 49 $ 39,402 Provision for loan losses 4,973 4,909 (124) (181) (9) 69 210 13 9,860 Charge-offs (3,863) (435) (6) — — (93) (228) — (4,625) Recoveries 84 20 3 — — 5 53 — 165 Balance at end of year $ 11,793 $ 27,795 $ 3,320 $ 1,402 $ 241 $ 186 $ 3 $ 62 $ 44,802 The following table details the amount of the allowance for loan losses and recorded investment in loans by class as of December 31, 2020 and 2019: Commercial Commercial Residential Single-Family Agricultural Consumer Other Unallocated Total December 31, 2020 Allowance for losses: Individually evaluated for impairment $ 8,281 $ 243 $ — $ — $ — $ — $ — $ — $ 8,524 Collectively evaluated for impairment 18,836 49,880 6,786 2,156 337 442 242 423 79,102 Loans acquired with deteriorated credit quality 194 — — — — — — — 194 Ending balance $ 27,311 $ 50,123 $ 6,786 $ 2,156 $ 337 $ 442 $ 242 $ 423 $ 87,820 Loans: Individually evaluated for impairment $ 39,298 $ 21,880 $ 2,550 $ — $ 613 $ 42 $ — $ — $ 64,383 Collectively evaluated for impairment 3,823,982 7,149,610 1,345,234 326,575 84,284 66,895 346 — 12,796,926 Acquired with deteriorated credit quality 38,986 170,987 4,681 — 117 15 — — 214,786 Ending balance $ 3,902,266 $ 7,342,477 $ 1,352,465 $ 326,575 $ 85,014 $ 66,952 $ 346 $ — $ 13,076,095 December 31, 2019 Allowance for losses: Individually evaluated for impairment $ 357 $ — $ — $ — $ — $ 1 $ — $ — $ 358 Collectively evaluated for impairment 12,108 32,615 3,678 1,606 332 225 5 (315) 50,254 Loans acquired with deteriorated credit quality 379 470 — — — — — — 849 Ending balance $ 12,844 $ 33,085 $ 3,678 $ 1,606 $ 332 $ 226 $ 5 $ (315) $ 51,461 Loans: Individually evaluated for impairment $ 3,130 $ 6,813 $ 2,008 $ — $ 114 $ 22 $ — $ — $ 12,087 Collectively evaluated for impairment 2,416,569 6,883,639 1,505,896 378,120 93,837 32,556 621 — 11,311,238 Acquired with deteriorated credit quality 62,657 218,824 7,323 — 3,816 25 — — 292,645 Ending balance $ 2,482,356 $ 7,109,276 $ 1,515,227 $ 378,120 $ 97,767 $ 32,603 $ 621 $ — $ 11,615,970
Summary of Nonperforming Loans by Loan Class	Nonperforming loans by loan class (excluding loans acquired with deteriorated credit quality) at December 31, 2020 and 2019, are summarized as follows: Commercial Commercial Residential Real Estate Single-Family Agricultural Consumer Other Total December 31, 2020 Nonaccrual loans $ 25,898 $ 20,072 $ 2,372 $ — $ 613 $ 42 $ — $ 48,997 Loans past due 90 days and still accruing 433 — — — — — — 433 Troubled debt restructurings (not included in nonaccrual or loans past due and still accruing) — 1,808 178 — — — — 1,986 $ 26,331 $ 21,880 $ 2,550 $ — $ 613 $ 42 $ — $ 51,416 December 31, 2019 Nonaccrual loans $ 3,130 $ 6,461 $ 1,820 $ — $ 114 $ 22 $ — $ 11,547 Loans past due 90 days and still accruing 14,529 — — — — — — 14,529 Troubled debt restructurings (not included in nonaccrual or loans past due and still accruing) — 352 188 — — — — 540 $ 17,659 $ 6,813 $ 2,008 $ — $ 114 $ 22 $ — $ 26,616
Impaired Loans by Loan Class	Impaired loans by loan class (excluding loans acquired with deteriorated credit quality) at December 31, 2020 and 2019 and for the years ended December 31, 2020, 2019 and 2018, are summarized as follows: Commercial Commercial Residential Single-Family Agricultural Consumer Other Total December 31, 2020 Recorded investment in impaired loans: Impaired loans with an allowance for loan losses $ 24,540 $ 475 $ — $ — $ — $ — $ — $ 25,015 Impaired loans with no allowance for loan losses 14,758 21,405 2,550 — 613 42 — 39,368 Total $ 39,298 $ 21,880 $ 2,550 $ — $ 613 $ 42 $ — $ 64,383 Unpaid principal balance of impaired loans $ 63,817 $ 22,543 $ 2,742 $ — $ 650 $ 44 $ — $ 89,796 Allowance for loan losses on impaired loans $ 8,281 $ 243 $ — $ — $ — $ — $ — $ 8,524 December 31, 2019 Recorded investment in impaired loans: Impaired loans with an allowance for loan losses $ 1,580 $ — $ — $ — $ — $ 1 $ — $ 1,581 Impaired loans with no allowance for loan losses 1,550 6,813 2,008 — 114 21 — 10,506 Total $ 3,130 $ 6,813 $ 2,008 $ — $ 114 $ 22 $ — $ 12,087 Unpaid principal balance of impaired loans $ 8,580 $ 6,967 $ 2,197 $ — $ 123 $ 24 $ — $ 17,891 Allowance for loan losses on impaired loans $ 357 $ — $ — $ — $ — $ 1 $ — $ 358 For the year ended December 31, 2020 Average recorded investment in impaired loans $ 21,559 $ 9,497 $ 2,362 $ — $ 442 $ 30 $ — $ 33,890 Interest income recognized on impaired loans $ 168 $ 139 $ 208 $ — $ — $ — $ — $ 515 For the year ended December 31, 2019 Average recorded investment in impaired loans $ 6,266 $ 3,979 $ 1,746 $ 716 $ 57 $ 30 $ — $ 12,794 Interest income recognized on impaired loans $ 30 $ 39 $ 39 $ 119 $ — $ 6 $ — $ 233 For the year ended December 31, 2018 Average recorded investment in impaired loans $ 8,919 $ 2,667 $ 2,033 $ 716 $ — $ 46 $ — $ 14,381 Interest income recognized on impaired loans $ 119 $ 65 $ 81 $ 1 $ — $ 2 $ — $ 268
Summary of Troubled Debt Restructurings	Following is a summary of loans modified under troubled debt restructurings during the years ended December 31, 2020 and 2019: Commercial Commercial Residential Single-Family Agricultural Consumer Other Total Troubled debt restructurings during the year ended December 31, 2020 Number of contracts — 1 — — — — — 1 Pre-restructuring outstanding recorded investment $ — $ 1,517 $ — $ — $ — $ — $ — $ 1,517 Post-restructuring outstanding recorded investment $ — $ 1,517 $ — $ — $ — $ — $ — $ 1,517 Troubled debt restructurings during the year ended December 31, 2019 Number of contracts — — 1 — — — — 1 Pre-restructuring outstanding recorded investment $ — $ — $ 29 $ — $ — $ — $ — $ 29 Post-restructuring outstanding recorded investment $ — $ — $ 29 $ — $ — $ — $ — $ 29
Aging of Past Due Loans by Loan Class	The following table presents information regarding the aging of past due loans by loan class as of December 31, 2020 and 2019: Loans Loans Total Past Current Total December 31, 2020 Commercial $ 3,243 $ 13,227 $ 16,470 $ 3,846,810 $ 3,863,280 Commercial real estate, construction, land and land development 2,453 16,790 19,243 7,152,247 7,171,490 Residential real estate 5,169 1,028 6,197 1,341,587 1,347,784 Single-family interim construction — — — 326,575 326,575 Agricultural — 1 1 84,896 84,897 Consumer 86 41 127 66,810 66,937 Other — — — 346 346 10,951 31,087 42,038 12,819,271 12,861,309 Acquired with deteriorated credit quality 624 3,219 3,843 210,943 214,786 $ 11,575 $ 34,306 $ 45,881 $ 13,030,214 $ 13,076,095 December 31, 2019 Commercial $ 4,512 $ 17,656 $ 22,168 $ 2,397,531 $ 2,419,699 Commercial real estate, construction, land and land development 9,153 2,905 12,058 6,878,394 6,890,452 Residential real estate 3,242 642 3,884 1,504,020 1,507,904 Single-family interim construction 2,836 — 2,836 375,284 378,120 Agricultural 22 114 136 93,815 93,951 Consumer 167 22 189 32,389 32,578 Other — — — 621 621 19,932 21,339 41,271 11,282,054 11,323,325 Acquired with deteriorated credit quality 2,556 6,766 9,322 283,323 292,645 $ 22,488 $ 28,105 $ 50,593 $ 11,565,377 $ 11,615,970
Summary of Loans by Credit Quality Indicator by Class	A summary of loans by credit quality indicator by class as of December 31, 2020 and 2019, is as follows: Pass Pass/ Special Mention Substandard Doubtful Total December 31, 2020 Commercial $ 3,700,626 $ 55,960 $ 38,186 $ 97,403 $ 10,091 $ 3,902,266 Commercial real estate, construction, land and land development 6,504,933 352,910 360,963 123,671 — 7,342,477 Residential real estate 1,332,757 6,296 5,726 7,686 — 1,352,465 Single-family interim construction 323,800 2,775 — — — 326,575 Agricultural 76,951 6,194 1,205 664 — 85,014 Consumer 66,854 8 — 90 — 66,952 Other 346 — — — — 346 $ 12,006,267 $ 424,143 $ 406,080 $ 229,514 $ 10,091 $ 13,076,095 December 31, 2019 Commercial $ 2,332,611 $ 71,642 $ 37,739 $ 40,364 $ — $ 2,482,356 Commercial real estate, construction, land and land development 6,814,780 184,720 46,889 62,887 — 7,109,276 Residential real estate 1,501,019 4,850 994 8,364 — 1,515,227 Single-family interim construction 376,887 1,233 — — — 378,120 Agricultural 88,044 5,287 1,864 2,572 — 97,767 Consumer 32,459 33 2 109 — 32,603 Other 621 — — — — 621 $ 11,146,421 $ 267,765 $ 87,488 $ 114,296 $ — $ 11,615,970 The Company has included PCI loans in the above grading tables. The following provides additional detail on the grades applied to those loans at December 31, 2020 and 2019: Pass Pass/ Special Mention Substandard Doubtful Total December 31, 2020 $ 117,896 $ 45,672 $ 32,557 $ 18,661 $ — $ 214,786 December 31, 2019 232,095 21,284 4,502 34,764 — 292,645
Outstanding balance and related carrying amount of purchased credit impaired loans	The following table summarizes the outstanding balance and related carrying amount of PCI loans by acquired bank as of the acquisition date for the acquisition occurring in 2019. Acquisition Date January 1, 2019 Guaranty Bancorp Outstanding balance $ 341,645 Nonaccretable difference (16,622) Accretable yield (13,299) Carrying amount $ 311,724 The carrying amount of all acquired PCI loans included in the consolidated balance sheet and the related outstanding balance at December 31, 2020 and 2019, were as follows: December 31, 2020 2019 Outstanding balance $ 237,786 $ 326,077 Carrying amount 214,786 292,645
Accretable yield rollforward	The changes in accretable yield during the years ended December 31, 2020 and 2019 in regard to loans transferred at acquisition for which it was probable that all contractually required payments would not be collected are presented in the table below. 2020 2019 Balance at January 1 $ 8,905 $ 1,436 Additions — 13,299 Accretion (3,287) (5,830) Transfers from nonaccretable — — Balance at December 31 $ 5,618 $ 8,905

Premises and Equipment, Net (Ta

Premises and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Components of Premises and Equipment, Net	Premises and equipment, net at December 31, 2020 and 2019 consisted of the following: December 31, 2020 2019 Land $ 65,103 $ 58,643 Building 191,940 184,589 Furniture, fixtures and equipment 39,282 39,855 Aircraft 8,947 8,947 Leasehold and tenant improvements 5,798 5,466 Construction in progress 915 834 311,985 298,334 Less accumulated depreciation (62,518) (55,460) $ 249,467 $ 242,874

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets, Net (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Other Intangible Assets Activity	The following is a summary of other intangible assets activity: December 31, 2020 2019 Core deposit intangible: Balance at beginning of the year $ 125,884 $ 63,891 Additions: Guaranty acquisition — 61,993 Balance at end of the year 125,884 125,884 Less accumulated amortization (43,235) (31,057) Total core deposit intangible, net $ 82,649 $ 94,827 Customer relationship intangible: Balance at beginning of the year $ 6,407 $ — Additions: Guaranty acquisition — 9,525 Deletions: sale of trust business — (3,118) Balance at end of the year 6,407 6,407 Less accumulated amortization (986) (493) Total customer relationship intangible, net $ 5,421 $ 5,914 Total other intangible assets, net $ 88,070 $ 100,741
Future Amortization Expense Related to Other Intangible Assets	The future amortization expense related to other intangible assets remaining at December 31, 2020 is as follows: First year $ 12,580 Second year 12,491 Third year 12,439 Fourth year 11,752 Fifth year 11,238 Thereafter 27,570 $ 88,070

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2020
Deposits [Abstract]
Components of Deposits	Deposits at December 31, 2020 and 2019 consisted of the following: December 31, 2020 2019 Amount Percent Amount Percent Noninterest-bearing demand accounts $ 4,164,800 28.9 % $ 3,240,185 27.1 % Interest-bearing checking accounts 5,420,548 37.6 4,198,772 35.2 Savings accounts 654,733 4.6 552,585 4.6 Limited access money market accounts 2,743,208 19.1 2,119,878 17.8 Certificates of deposit and individual retirement accounts (IRA), less than $250,000 675,329 4.7 892,639 7.5 Certificates of deposit and individual retirement accounts (IRA), $250,000 and greater 740,309 5.1 937,277 7.8 $ 14,398,927 100.0 % $ 11,941,336 100.0 %
Maturities of Certificates of Deposit	At December 31, 2020, the scheduled maturities of certificates of deposit, including IRAs, were as follows: First year $ 1,263,633 Second year 117,521 Third year 19,362 Fourth year 5,058 Fifth year 10,059 Thereafter 5 $ 1,415,638

Federal Home Loan Bank Advanc_2

Federal Home Loan Bank Advances (Tables)	12 Months Ended
	Dec. 31, 2020
Advances from Federal Home Loan Banks [Abstract]
Contractual Maturities of FHLB Advances	Contractual maturities of FHLB advances at December 31, 2020 were as follows: First year $ 25,000 Second year — Third year 200,000 Fourth year — Fifth year — Thereafter 150,000 $ 375,000

Other Borrowings (Tables)

Other Borrowings (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Other borrowings	Other borrowings at December 31, 2020 and 2019 consisted of the following: December 31, 2020 2019 Unsecured fixed rate subordinated debentures in the amount of $110,000. The balance of borrowings at December 31, 2020 and 2019 is net of discount and origination costs of $1,271 and $1,628, respectively. Interest payments of 5.875% are made semiannually on February 1 and August 1. The maturity date is August 1, 2024. The notes may not be redeemed prior to maturity and meet the criteria to be recognized as Tier 2 capital for regulatory purposes. (1)(2) $ 108,729 $ 108,372 Unsecured fixed-to-floating subordinated debentures in the original amount of $40,000. Interest payments initially of 5.75% are made semiannually on January 20 and July 20 through July 20, 2021. Thereafter, floating rate payments of 3 month LIBOR plus 4.73% are made quarterly in arrears beginning on October 20, 2021. The maturity date is July 20, 2026 with an optional redemption at July 20, 2021. The notes meet the criteria to be recognized as Tier 2 capital for regulatory purposes. (2)(3) 40,000 40,000 Unsecured fixed-to-floating subordinated debentures in the amount of $30,000. The balance of borrowings at December 31, 2020 and 2019 is net of origination costs of $543 and $621, respectively. Interest payments initially of 5.00% fixed rate are made semiannually on June 30 and December 31 through December 31, 2022. Thereafter, floating rate payments of 3 month LIBOR plus 2.83% are made quarterly in arrears beginning on March 31, 2023. The maturity date is December 31, 2027 with an optional redemption at December 31, 2022. The notes meet the criteria to be recognized as Tier 2 capital for regulatory purposes. (2) 29,457 29,379 Unsecured fixed-to-floating subordinated debentures in the amount of $130,000. The balance of borrowings at December 31, 2020 is net of origination costs of $2,511. Interest payments initially of 4.00% fixed rate are made semiannually on March 15 and September 15 through September 15, 2025. Thereafter, floating rate payments equal to a benchmark rate (which is expected to be 3 month Secured Overnight Financing Rate (SOFR)) plus 3.885% payable quarterly in arrears beginning on December 15, 2025. The maturity date is September 15, 2030 with an optional redemption at September 15, 2025. The notes meet the criteria to be recognized as Tier 2 capital for regulatory purposes. (2) 127,489 — Unsecured revolving line of credit with an unrelated commercial bank in the amount of $100,000. The line bears interest at LIBOR plus 1.75% and matures January 17, 2021. The Company is required to meet certain financial covenants on a quarterly basis, which includes certain restrictions on cash at IBG and meeting minimum capital ratios. (4) 6,500 24,500 $ 312,175 $ 202,251 ____________ (1) At December 31, 2020 and 2019, other borrowings included amounts owed to related parties of $50. (2) The permissible portion of qualified subordinated notes decreases 20% per year during the final five years of the term of the notes. (3) Assumed on January 1, 2019 with the Guaranty acquisition (see Note 22, Business Combinations ). (4) Subsequent to December 31, 2020, the Company renewed the line (see Note 24, Subsequent Events ).

Junior Subordinated Debentures

Junior Subordinated Debentures (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Subordinated Borrowing	Information regarding the Debentures as of December 31, 2020 are summarized in the table below: Trust Preferred Securities Issued Debentures Carrying Value Repricing Frequency Interest Rate Interest Rate Index Maturity Date IB Trust I $ 5,155 $ 5,155 Quarterly 3.46% LIBOR + 3.25% March 2033 Guaranty Trust III (1) 10,310 10,310 Quarterly 3.34 LIBOR + 3.10 July 2033 IB Trust II 3,093 3,093 Quarterly 3.09 LIBOR + 2.85 March 2034 Cenbank Trust III (1) 15,464 15,464 Quarterly 2.89 LIBOR + 2.65 April 2034 IB Trust III 3,712 3,712 Quarterly 2.61 LIBOR +2.40 December 2035 IB Centex Trust I 2,578 2,578 Quarterly 3.46 LIBOR + 3.25 February 2035 Community Group Statutory Trust I 3,609 3,609 Quarterly 1.82 LIBOR + 1.60 June 2037 Northstar Trust II (2) 5,155 3,892 Quarterly 1.89 LIBOR + 1.67 June 2037 Northstar Trust III (2) 8,248 6,210 Quarterly 1.89 LIBOR + 1.67 September 2037 $ 57,324 $ 54,023 ____________ (1) Assumed on January 1, 2019 with the Guaranty acquisition (see Note 22, Business Combinations ).

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Schedule of Net Lease Cost and Other Information Related to Operating Leases	The table below summarizes net lease cost: Year Ended December 31, 2020 2019 Operating lease cost $ 6,937 $ 7,025 Short term lease cost 124 103 Variable lease cost 1,631 1,829 Sublease income (221) (228) Net lease cost $ 8,471 $ 8,729 Rent expense for the year ended December 31, 2018, prior to the adoption of ASU 2016-2, was $3,758. The table below summarizes other information related to operating leases: Year Ended December 31, 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 6,091 $ 6,965 Weighted average remaining lease term - operating leases, in years 7.23 7.58 Weighted average discount rate - operating leases 3.47 % 3.35 %
Summary of Lease Payment Obligations	The following table outlines lease payment obligations as outlined in the Company’s lease agreements for each of the next five years and thereafter in addition to a reconcilement to the Company’s current lease liability as of December 31, 2020. 2021 $ 5,615 2022 4,876 2023 4,054 2024 3,438 2025 2,754 Thereafter 5,700 Total lease payments 26,437 Less imputed interest (3,024) $ 23,413

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of Income Tax Expense	Income tax expense for the years ended December 31, 2020, 2019 and 2018 was as follows: Years Ended December 31, 2020 2019 2018 Current income tax expense $ 52,806 $ 39,426 $ 29,801 Deferred income tax (benefit) expense (1,633) 14,102 2,000 Deferred income tax benefit related to remeasurement of deferred taxes — — (63) Income tax expense, as reported $ 51,173 $ 53,528 $ 31,738
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation between reported income tax expense and the amounts computed by applying the U.S. federal statutory income tax rate of 21% for the years ended December 31, 2020, 2019 and 2018 to income before income taxes is presented below: Years Ended December 31, 2020 2019 2018 Income tax expense computed at the statutory rate $ 53,000 $ 51,715 $ 33,599 Tax-exempt interest income from municipal securities (1,779) (1,781) (962) Tax-exempt loan income (1,245) (1,174) (490) Bank owned life insurance income (1,123) (1,288) (666) Non-deductible acquisition expenses — 281 142 State taxes, net of federal benefit 2,660 3,455 375 Non-deductible compensation — 2,017 — Net tax expense (benefit) from stock based compensation 243 21 (646) Deferred tax adjustment related to reduction in U.S. Federal statutory income tax rate — — (63) Other (583) 282 449 $ 51,173 $ 53,528 $ 31,738
Schedule of Deferred Tax Assets and Liabilities	Components of deferred tax assets and liabilities are presented in the table below. Deferred taxes as of December 31, 2020 and 2019 are based on the U.S. statutory federal income tax rate of 21%. December 31, 2020 2019 Deferred tax assets: Allowance for loan losses $ 19,238 $ 11,466 Lease liabilities under operating leases 5,129 6,457 NOL and tax credit carryforwards from acquisitions 3,718 4,209 Acquired loan fair market value adjustments 12,986 21,645 Stock-based compensation 1,567 1,218 Reserve for bonuses and other accrued expenses 3,409 2,773 Acquisition costs — 416 Acquired securities 2,095 2,529 Acquired intangibles 1,369 1,546 Start up costs 171 230 Other real estate owned — 362 Unearned income 715 774 Deferred compensation 857 1,101 Noncompete agreements 597 663 Nonaccrual loans 550 390 Other 727 785 53,128 56,564 Deferred tax liabilities: Premises and equipment (12,392) (13,170) Right-of-use assets under operating leases (4,911) (6,233) Net unrealized gain on available for sale securities (9,501) (5,367) Intangible assets (19,293) (22,447) Acquired junior subordinated debentures fair value adjustment (723) (780) PPP deferred loan costs (952) — FHLB and other restricted stocks (308) (673) Acquired tax goodwill (572) (413) Other (543) (538) (49,195) (49,621) Net deferred tax asset $ 3,933 $ 6,943

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	At December 31, 2020 and 2019, the approximate amounts of these financial instruments were as follows: December 31, 2020 2019 Commitments to extend credit $ 2,268,216 $ 2,337,385 Standby letters of credit 25,917 23,406 $ 2,294,133 $ 2,360,791

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Loan Activity for Officers, Directors and Affiliates	Loan activity for officers, directors and their affiliates for the year ended December 31, 2020 is as follows: Balance at beginning of year $ 38,796 New loans 30,912 Repayments (38,570) Changes in affiliated persons 1,333 Balance at end of year $ 32,471

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Assets and Liabilities at Fair Value on Recurring Basis	The following table represents assets and liabilities reported on the consolidated balance sheets at their fair value on a recurring basis as of December 31, 2020 and 2019 by level within the ASC Topic 820 fair value measurement hierarchy: Fair Value Measurements at Reporting Date Using Assets/ Quoted Prices Significant Significant December 31, 2020 Assets: Investment securities available for sale: U.S. treasuries $ 44,708 $ — $ 44,708 $ — Government agency securities 249,017 — 249,017 — Obligations of state and municipal subdivisions 393,165 — 393,165 — Corporate bonds 22,102 — 22,102 — Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 443,501 — 443,501 — Other securities 1,200 — 1,200 — Loans held for sale, fair value option elected (1) 71,769 — 71,769 — Derivative financial instruments: Interest rate lock commitments 3,515 — 3,515 — Loan customer counterparty 20,159 — 20,159 — Liabilities: Derivative financial instruments: Forward mortgage-backed securities trades 568 — 568 — Financial institution counterparty 21,306 — 21,306 — December 31, 2019 Assets: Investment securities available for sale: U.S. treasuries $ 48,796 $ — $ 48,796 $ — Government agency securities 179,296 — 179,296 — Obligations of state and municipal subdivisions 343,859 — 343,859 — Corporate bonds 7,218 — 7,218 — Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA 505,567 — 505,567 — Other securities 1,200 — 1,200 — Loans held for sale, fair value option elected (1) 29,204 — 29,204 — Derivative financial instruments: Interest rate lock commitments 847 — 847 — Forward mortgage-backed securities trades 6 — 6 — Loan customer counterparty 6,104 — 6,104 — Liabilities: Derivative financial instruments: Forward mortgage-backed securities trades 69 — 69 — Financial institution counterparty 6,566 — 6,566 — ____________ (1) At December 31, 2020 and 2019, loans held for sale for which the fair value option was elected had an aggregate outstanding principal balance of $68,670 and $28,166, respectively. There were no mortgage loans held for sale under the fair value option that were 90 days or greater past due or on nonaccrual at December 31, 2020.
Assets and Liabilities at Fair Value on Nonrecurring Basis	The following table presents the assets carried on the consolidated balance sheet by caption and by level in the fair value hierarchy at December 31, 2020 and 2019, for which a nonrecurring change in fair value has been recorded: Fair Value Measurements at Reporting Date Using Assets Quoted Prices Significant Significant Period Ended December 31, 2020 Assets: Impaired loans $ 16,903 $ — $ — $ 16,903 $ 13,041 December 31, 2019 Assets: Impaired loans $ 2,276 $ — $ — $ 2,276 $ 1,806 Other real estate owned 4,618 — — 4,618 749
Carrying Amount and Estimated Fair Value of Financial Instruments	The carrying amount, estimated fair value and the level of the fair value hierarchy of the Company’s financial instruments that are reported at amortized cost on the Company's consolidated balance sheets were as follows at December 31, 2020 and 2019: Fair Value Measurements at Reporting Date Using Carrying Estimated Quoted Prices Significant Significant December 31, 2020 Financial assets: Cash and cash equivalents $ 1,813,987 $ 1,813,987 $ 1,813,987 $ — $ — Certificates of deposit held in other banks 4,482 4,595 — 4,595 — Loans held for sale, at cost 10,878 11,138 — 11,138 — Loans, net 12,978,238 13,093,698 — — 13,093,698 FHLB of Dallas stock and other restricted stock 20,305 20,305 — 20,305 — Accrued interest receivable 60,581 60,581 — 60,581 — Financial liabilities: Deposits 14,398,927 14,407,596 — 14,407,596 — Accrued interest payable 7,397 7,397 — 7,397 — FHLB advances 375,000 371,175 — 371,175 — Other borrowings 312,175 327,150 — 327,150 — Junior subordinated debentures 54,023 42,624 — 42,624 — Off-balance sheet assets (liabilities): Commitments to extend credit — — — — — Standby letters of credit — — — — — December 31, 2019 Financial assets: Cash and cash equivalents $ 565,170 $ 565,170 $ 565,170 $ — $ — Certificates of deposit held in other banks 5,719 5,951 — 5,951 — Loans held for sale, at cost 6,441 6,554 — 6,554 — Loans, net 11,562,814 11,689,672 — — 11,689,672 FHLB of Dallas stock and other restricted stock 30,052 30,052 — 30,052 — Accrued interest receivable 35,860 35,860 — 35,860 — Financial liabilities: Deposits 11,941,336 11,958,939 — 11,958,939 — Accrued interest payable 9,583 9,583 — 9,583 — FHLB advances 325,000 325,210 — 325,210 — Other borrowings 202,251 209,050 — 209,050 — Junior subordinated debentures 53,824 48,879 — 48,879 — Off-balance sheet assets (liabilities): Commitments to extend credit — — — — — Standby letters of credit — — — — —

Derivative Financial Instrume_2

Derivative Financial Instruments - (Tables)	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional Balances and Fair Values of Outstanding Positions	The following table provides the outstanding notional balances and fair values of outstanding derivative positions at December 31, 2020 and 2019: Outstanding Notional Balance Asset Derivative Liability Derivative December 31, 2020 Interest rate lock commitments $ 116,795 $ 3,515 $ — Forward mortgage-backed securities trades 104,000 — 568 Commercial loan interest rate swaps: Loan customer counterparty 335,370 20,159 — Financial institution counterparty 335,370 — 21,306 December 31, 2019 Interest rate lock commitments $ 28,434 $ 847 $ — Forward mortgage-backed securities trades 42,500 6 69 Commercial loan interest rate swaps: Loan customer counterparty 280,751 6,104 — Financial institution counterparty 280,751 — 6,566
Schedule of Weighted Average Interest Rate Received and Paid	The commercial loan customer counterparty weighted average received and paid interest rates for interest rate swaps outstanding were as follows: Weighted Average Interest Rate December 31, 2020 December 31, 2019 Received Paid Received Paid Loan customer counterparty 4.08 % 2.32 % 4.23 % 3.77 %
Income (Loss) on Derivatives Not Designated as Hedging Instruments	Income (loss) for the years ended December 31, 2020 and 2019 was as follows: Years Ended December 31, 2020 2019 Derivatives not designated as hedging instruments Interest rate lock commitments $ 2,668 $ 25 Forward mortgage-backed securities trades (505) 163

Stock Awards (Tables)

Stock Awards (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Nonvested Shares Activity	The following table summarizes the activity in nonvested restricted stock awards for the years ended December 31, 2020 and 2019: Restricted Stock Awards Number of Weighted Average Nonvested shares, December 31, 2019 284,861 $ 58.63 Granted during the period 310,290 43.54 Vested during the period (115,436) 58.08 Forfeited during the period (10,915) 48.37 Nonvested shares, December 31, 2020 468,800 $ 49.01 Nonvested shares, December 31, 2018 252,903 $ 62.81 Acquired awards replaced during the period 70,248 45.77 Granted during the period 138,608 51.14 Vested during the period (161,032) 54.76 Forfeited during the period (15,866) 46.95 Nonvested shares, December 31, 2019 284,861 $ 58.63
Future Vesting Schedule of Nonvested Shares Activity	At December 31, 2020, the future vesting schedule of the nonvested restricted stock awards is as follows: First year 177,431 Second year 139,009 Third year 99,604 Fourth year 52,356 Fifth year 400 Total nonvested shares 468,800
Nonvested performance stock units	The following table summarizes the activity in nonvested performance stock units at target award level for the year ended December 31, 2020: Performance-based Restricted Stock Units Number of Weighted Average Nonvested shares, December 31, 2019 — $ — Granted during the period 89,300 38.29 Vested during the period — — Forfeited during the period — — Nonvested shares, December 31, 2020 89,300 $ 38.29

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2020
Regulated Operations [Abstract]
Schedule of Compliance with Regulatory Capital Requirements	The following table presents actual capital amounts and required ratios under Basel III Capital Rules for the Company and Bank as of December 31, 2020 and December 31, 2019. Actual Minimum Capital To Be Well Amount Ratio Amount Ratio Amount Ratio December 31, 2020 Total capital to risk weighted assets: Consolidated $ 1,825,661 13.32 % $ 1,438,939 10.50 % N/A N/A Bank 1,864,240 13.61 1,438,385 10.50 $ 1,369,891 10.00 % Tier 1 capital to risk weighted assets: Consolidated 1,471,841 10.74 1,164,855 8.50 N/A N/A Bank 1,776,420 12.97 1,164,407 8.50 1,095,913 8.00 Common equity tier 1 to risk weighted assets: Consolidated 1,416,241 10.33 959,293 7.00 N/A N/A Bank 1,776,420 12.97 958,924 7.00 890,429 6.50 Tier 1 capital to average assets: Consolidated 1,471,841 9.12 645,730 4.00 N/A N/A Bank 1,776,420 11.01 645,539 4.00 806,924 5.00 December 31, 2019 Total capital to risk weighted assets: Consolidated $ 1,513,209 11.83 % $ 1,343,114 10.50 % N/A N/A Bank 1,548,103 12.11 1,342,595 10.50 $ 1,278,662 10.00 % Tier 1 capital to risk weighted assets: Consolidated 1,303,748 10.19 1,087,282 8.50 N/A N/A Bank 1,496,642 11.70 1,086,863 8.50 1,022,930 8.00 Common equity tier 1 to risk weighted assets: Consolidated 1,248,148 9.76 895,409 7.00 N/A N/A Bank 1,496,642 11.70 895,064 7.00 831,130 6.50 Tier 1 capital to average assets: Consolidated 1,303,748 9.32 559,758 4.00 N/A N/A Bank 1,496,642 10.70 559,584 4.00 699,480 5.00

Business Combinations (Tables)

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
Estimated Fair Values of Assets Acquired and Liabilities Assumed	The following table summarizes the final fair values of the assets acquired and liabilities assumed in this transaction: Final Value as Reported at December 31, 2019 Assets of acquired bank: Cash and cash equivalents $ 39,913 Certificates of deposit held in other banks 262 Securities available for sale 561,052 Restricted stock 27,794 Loans 2,789,868 Premises and equipment 65,786 Other real estate owned 1,829 Goodwill 272,224 Other intangible assets 71,518 Bank owned life insurance 80,837 Other assets 31,987 Total assets acquired $ 3,943,070 Liabilities of acquired bank: Deposits $ 3,108,810 Repurchase agreements 8,475 FHLB advances 142,653 Other borrowings 40,000 Junior subordinated debentures 25,774 Other liabilities 15,477 Total liabilities assumed $ 3,341,189 Common stock of 13,109,500 issued at $45.77 per share $ 600,022 Consideration attributable to 70,248 shares of restricted stock replacement awards $ 1,850 Cash paid $ 9

Parent Company Only Financial_2

Parent Company Only Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2020
Condensed Financial Information Disclosure [Abstract]
Balance Sheet for the Parent Company	The following balance sheets, statements of income and statements of cash flows for Independent Bank Group, Inc. should be read in conjunction with the consolidated financial statements and the notes thereto. Balance Sheets December 31, Assets 2020 2019 Cash and cash equivalents $ 5,482 $ 8,277 Investment in subsidiaries 2,876,171 2,588,857 Investment in trusts 1,724 1,724 Other assets 3,849 3,355 Total assets $ 2,887,226 $ 2,602,213 Liabilities and Stockholders' Equity Other borrowings $ 312,175 $ 202,251 Junior subordinated debentures 54,023 53,824 Other liabilities 5,657 6,365 Total liabilities 371,855 262,440 Stockholders' equity: Preferred stock — — Common stock 431 430 Additional paid-in capital 1,934,807 1,926,359 Retained earnings 543,800 393,674 Accumulated other comprehensive income 36,333 19,310 Total stockholders' equity 2,515,371 2,339,773 Total liabilities and stockholders' equity $ 2,887,226 $ 2,602,213
Statement of Income for the Parent Company	Statements of Income Years Ended December 31, 2020 2019 2018 Interest expense: Interest on other borrowings $ 12,446 $ 11,561 $ 8,390 Interest on junior subordinated debentures 2,162 3,028 1,609 Total interest expense 14,608 14,589 9,999 Noninterest income: Dividends from subsidiaries 83,314 105,877 39,841 Other — 1 14 Total noninterest income 83,314 105,878 39,855 Noninterest expense: Salaries and employee benefits 8,346 7,653 6,318 Professional fees 202 264 332 Acquisition expense, including legal 16,225 33,445 6,157 Other 2,424 2,562 1,611 Total noninterest expense 27,197 43,924 14,418 Income before income tax benefit and equity in undistributed income of subsidiaries 41,509 47,365 15,438 Income tax benefit 9,410 11,066 5,541 Income before equity in undistributed income of subsidiaries 50,919 58,431 20,979 Equity in undistributed income of subsidiaries 150,290 134,305 107,280 Net income $ 201,209 $ 192,736 $ 128,259
Statement of Cash Flows for the Parent Company	Statements of Cash Flows Years Ended December 31, 2020 2019 2018 Cash flows from operating activities: Net income $ 201,209 $ 192,736 $ 128,259 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed net income of subsidiaries (150,290) (134,305) (107,280) Amortization of discount and origination costs on borrowings 720 633 633 Stock based compensation expense 8,450 7,808 6,062 Excess tax expense on restricted stock vested 243 21 (646) Deferred tax expense 96 2,165 1,054 Net change in other assets (590) 1,863 6,918 Net change in other liabilities (952) (64) 1,130 Net cash provided by operating activities 58,886 70,857 36,130 Cash flows from investing activities: Capital investment in subsidiaries (120,000) — — Cash acquired in connection with acquisition — 339 7,425 Cash paid in connection with acquisition — (9) (31,016) Net cash provided by (used in) financing activities (120,000) 330 (23,591) Cash flows from financing activities: Proceeds from other borrowings 148,653 65,000 — Repayments of other borrowings (39,250) (40,500) — Proceeds from exercise of common stock warrants — — 2,533 Offering costs paid in connection with acquired bank — (804) (209) Repurchase of common stock (5,819) (51,659) — Dividends paid (45,265) (43,302) (15,908) Net cash provided by (used in) financing activities 58,319 (71,265) (13,584) Net change in cash and cash equivalents (2,795) (78) (1,045) Cash and cash equivalents at beginning of year 8,277 8,355 9,400 Cash and cash equivalents at end of year $ 5,482 $ 8,277 $ 8,355

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details)	Jan. 01, 2019business_trust	Dec. 31, 2020business_trustsegment
Summary Of Significant Accounting Policies [Line Items]
Number of wholly owned statutory business trusts		9
Number of reportable segments | segment		1
Guaranty Bancorp
Summary Of Significant Accounting Policies [Line Items]
Number Of Wholly Owned Statutory Business Trusts	2
Core deposit intangibles
Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangible assets, useful life		10 years
Customer relationship intangibles
Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangible assets, useful life		13 years
Minimum
Summary Of Significant Accounting Policies [Line Items]
Premises and equipment, useful life		3 years
Minimum | Computer Software, Intangible Asset
Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangible assets, useful life		1 year
Maximum
Summary Of Significant Accounting Policies [Line Items]
Premises and equipment, useful life		30 years
Maximum | Computer Software, Intangible Asset
Summary Of Significant Accounting Policies [Line Items]
Finite-lived intangible assets, useful life		5 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Basic earnings per share:
Net income	$ 201,209	$ 192,736	$ 128,259
Undistributed earnings allocated to participating securities	1,311	971	976
Dividends paid on participating securities	380	281	139
Net income available to common shareholders	$ 199,518	$ 191,484	$ 127,144
Weighted-average basic shares outstanding (shares)	42,754,606	42,964,393	29,341,843
Basic earnings per share (usd per share)	$ 4.67	$ 4.46	$ 4.33
Diluted earnings per share:
Net income available to common shareholders	$ 199,518	$ 191,484	$ 127,144
Weighted-average basic shares outstanding (shares)	42,754,606	42,964,393	29,341,843
Total weighted-average diluted shares outstanding (shares)	42,754,606	42,964,393	29,341,843
Diluted earnings per share (usd per share)	$ 4.67	$ 4.46	$ 4.33
Anti-dilutive participating securities (shares)	58,359	73,546	114,087

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	Jan. 01, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets		$ 24,841	$ 38,813
Operating Lease, Liability		23,413	28,978
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets				$ 38,812
Operating Lease, Liability				33,953
Prepaid Rent				4,949
Accumulated other comprehensive loss | Accounting Standards Update 2018-02 | Cumulative effect of change in accounting principles
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement Or Change In Accounting Principle Cumulative Effect Of Change On Equity Net Of Tax					$ 233
Retained Earnings | Accounting Standards Update 2016-02 | Cumulative effect of change in accounting principles
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement Or Change In Accounting Principle Cumulative Effect Of Change On Equity Net Of Tax				70
Retained Earnings | Accounting Standards Update 2017-10 [Member] | Cumulative effect of change in accounting principles
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement Or Change In Accounting Principle Cumulative Effect Of Change On Equity Net Of Tax				$ 856
Forecast | Accounting Standards Update 2016-13 | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans acquired with deteriorated credit quality	$ 68
Forecast | Accounting Standards Update 2016-13 | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans acquired with deteriorated credit quality	84,000
Receivables Acquired with Deteriorated Credit Quality
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans acquired with deteriorated credit quality		$ 194	$ 849
Receivables Acquired with Deteriorated Credit Quality | Forecast | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans acquired with deteriorated credit quality	$ 13,000

Restrictions on Cash and Due _2

Restrictions on Cash and Due from Banks (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Deposit reserve requirement		$ 63,739
Cash collateral pledged for derivatives	$ 23,829	$ 4,350

Statement of Cash Flows - Other

Statement of Cash Flows - Other Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash transactions:
Interest expense paid	$ 97,246	$ 144,775	$ 79,509
Income taxes paid	54,842	40,504	25,109
Noncash transactions:
Transfers of loans to other real estate owned	5,239	544	410
Loans to facilitate the sale of other real estate owned	2,039	517	0
Securities purchased, not yet settled	0	9,975	0
Transfers of loans held for investment to loans held for sale	0	83,526	0
Right-of-use assets obtained in exchange for lease liabilities	105	35,553	0
Loans purchased, not yet settled	9,442	0	0
Transfer of bank premises to other real estate	0	7,896	0
Transfer of repurchase agreements to deposits	$ 0	$ 8,475	$ 0

Statement of Cash Flows - Nonca

Statement of Cash Flows - Noncash Investing from Branch Sale (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Noncash liabilities transferred:
Deposit premium received	$ 1,386
Cash paid to buyer, net of deposit premium	24,957
Sale of Branch
Noncash assets transferred:
Loans, including accrued interest	796
Premises and equipment	94
Other assets	2
Total assets	892
Noncash liabilities transferred:
Deposits, including interest	27,721
Other liabilities	27
Total liabilities	27,748
Sale of Branch | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Noncash liabilities transferred:
Cash and cash equivalents transferred in branch sales	$ 206

Statement of Cash Flows - Non_2

Statement of Cash Flows - Noncash Investing from Sale of Trust Business (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Noncash assets transferred:
Net cash received from sale	$ 0	$ 4,269	$ 0
Trust Business Sale
Noncash assets transferred:
Customer relationship intangible assets, net		2,939
Other assets		11
Total assets		2,950
Trust Business Sale | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Noncash assets transferred:
Net cash received from sale		$ 4,269

Statement of Cash Flows - Non_3

Statement of Cash Flows - Noncash Investing Activities from Acquisitions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Noncash assets acquired
Certificates of deposit held in other banks	$ 0	$ 262	$ 0
Securities available for sale	0	561,052	24,721
Restricted stock	0	27,794	3,357
Loans	0	2,789,868	651,769
Premises and equipment	0	65,786	4,863
Other real estate owned	0	1,829	0
Goodwill	0	272,224	100,339
Other intangible assets	0	71,518	7,537
Bank owned life insurance	0	80,837	8,181
Other assets	0	31,987	6,385
Total assets acquired	0	3,903,157	807,152
Noncash liabilities assumed:
Deposits	0	3,108,810	593,078
Repurchase agreements	0	8,475	0
FHLB advances	0	142,653	60,000
Other borrowings	0	40,000	0
Junior subordinated debentures	0	25,774	0
Other liabilities	0	15,477	10,518
Total liabilities assumed	0	3,341,189	663,596
Cash and cash equivalents acquired from acquisitions	0	39,913	44,723
Cash paid to shareholders of acquired banks	0	9	31,016
Fair value of common stock issued to shareholders of acquired banks	$ 0	$ 601,872	$ 157,263

Securities Available for Sale -

Securities Available for Sale - Amortized Cost of Securities and Approximate Fair Values (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,108,453	$ 1,061,854
Gross Unrealized Gains	47,271	25,007
Gross Unrealized Losses	(2,031)	(925)
Fair Value	1,153,693	1,085,936
U.S. treasuries
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	43,060	48,060
Gross Unrealized Gains	1,648	743
Gross Unrealized Losses	0	(7)
Fair Value	44,708	48,796
Government agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	247,764	178,953
Gross Unrealized Gains	3,169	926
Gross Unrealized Losses	(1,916)	(583)
Fair Value	249,017	179,296
Obligations of state and municipal subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	373,017	332,715
Gross Unrealized Gains	20,168	11,150
Gross Unrealized Losses	(20)	(6)
Fair Value	393,165	343,859
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	21,496	7,011
Gross Unrealized Gains	608	207
Gross Unrealized Losses	(2)	0
Fair Value	22,102	7,218
Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	421,916	493,915
Gross Unrealized Gains	21,678	11,981
Gross Unrealized Losses	(93)	(329)
Fair Value	443,501	505,567
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,200	1,200
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 1,200	$ 1,200

Securities Available for Sale_2

Securities Available for Sale - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Abstract]
Carrying value of securities pledged	$ 738,519	$ 571,843

Securities Available for Sale_3

Securities Available for Sale - Proceeds from Sale, Gross Gains and Losses of Securities Available for Sale (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Abstract]
Proceeds from sale	$ 13,862	$ 192,417	$ 102,647
Gross gains	385	306	268
Gross losses	$ 3	$ 31	$ 849

Securities Available for Sale_4

Securities Available for Sale - Amortized Cost and Estimated Fair Value of Securities Available for Sale by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Amortized Cost
Due in one year or less	$ 39,579
Due from one year to five years	128,804
Due from five to ten years	203,387
Thereafter	314,767
Single maturity dates, amortized cost basis	686,537
Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA	421,916
Amortized Cost	1,108,453	$ 1,061,854
Fair Value
Due in one year or less	39,943
Due from one year to five years	135,272
Due from five to ten years	209,396
Thereafter	325,581
Single maturity dates, fair value	710,192
Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA	443,501
Fair value, total	$ 1,153,693	$ 1,085,936

Securities Available for Sale_5

Securities Available for Sale - Summary of Unrealized Losses and Fair Value of Securities in Continuous Unrealized Loss Positions (Details) $ in Thousands	Dec. 31, 2020USD ($)security	Dec. 31, 2019USD ($)security
Debt Securities, Available-for-sale [Line Items]
Less than 12 months: number of securities | security	33	31
Less than 12 months: estimated fair value	$ 159,025	$ 102,095
Less than 12 months: unrealized losses	$ (2,031)	$ (813)
Greater than 12 months: number of securities | security	0	10
Greater than 12 months: estimated fair value	$ 0	$ 25,624
Greater than 12 months: unrealized losses	0	(112)
Total: estimated fair value	159,025	127,719
Total: unrealized losses	$ (2,031)	$ (925)
U.S. treasuries
Debt Securities, Available-for-sale [Line Items]
Less than 12 months: number of securities | security		0
Less than 12 months: estimated fair value		$ 0
Less than 12 months: unrealized losses		$ 0
Greater than 12 months: number of securities | security		2
Greater than 12 months: estimated fair value		$ 8,097
Greater than 12 months: unrealized losses		(7)
Total: estimated fair value		8,097
Total: unrealized losses		$ (7)
Government agency securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months: number of securities | security	20	13
Less than 12 months: estimated fair value	$ 112,897	$ 52,790
Less than 12 months: unrealized losses	$ (1,916)	$ (495)
Greater than 12 months: number of securities | security	0	6
Greater than 12 months: estimated fair value	$ 0	$ 15,911
Greater than 12 months: unrealized losses	0	(88)
Total: estimated fair value	112,897	68,701
Total: unrealized losses	$ (1,916)	$ (583)
Obligations of state and municipal subdivisions
Debt Securities, Available-for-sale [Line Items]
Less than 12 months: number of securities | security	2	5
Less than 12 months: estimated fair value	$ 3,786	$ 2,793
Less than 12 months: unrealized losses	$ (20)	$ (1)
Greater than 12 months: number of securities | security	0	1
Greater than 12 months: estimated fair value	$ 0	$ 423
Greater than 12 months: unrealized losses	0	(5)
Total: estimated fair value	3,786	3,216
Total: unrealized losses	$ (20)	$ (6)
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Less than 12 months: number of securities | security	1
Less than 12 months: estimated fair value	$ 998
Less than 12 months: unrealized losses	$ (2)
Greater than 12 months: number of securities | security	0
Greater than 12 months: estimated fair value	$ 0
Greater than 12 months: unrealized losses	0
Total: estimated fair value	998
Total: unrealized losses	$ (2)
Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA
Debt Securities, Available-for-sale [Line Items]
Less than 12 months: number of securities | security	10	13
Less than 12 months: estimated fair value	$ 41,344	$ 46,512
Less than 12 months: unrealized losses	$ (93)	$ (317)
Greater than 12 months: number of securities | security	0	1
Greater than 12 months: estimated fair value	$ 0	$ 1,193
Greater than 12 months: unrealized losses	0	(12)
Total: estimated fair value	41,344	47,705
Total: unrealized losses	$ (93)	$ (329)

Loans, Net and Allowance for _3

Loans, Net and Allowance for Loan Losses - Composition of Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Loans, gross	$ 13,076,095	$ 11,615,970
Deferred loan fees, net	(10,037)	(1,695)
Allowance for loan losses	(87,820)	(51,461)	$ (44,802)	$ (39,402)
Loans, net	12,978,238	11,562,814
Commercial
Accounts Notes And Loans Receivable [Line Items]
Loans, gross	3,902,266	2,482,356
Allowance for loan losses	(27,311)	(12,844)	(11,793)	(10,599)
Real estate | Commercial
Accounts Notes And Loans Receivable [Line Items]
Loans, gross	6,096,676	5,872,653
Real estate | Commercial construction, land and land development
Accounts Notes And Loans Receivable [Line Items]
Loans, gross	1,245,801	1,236,623
Real estate | Residential Real Estate
Accounts Notes And Loans Receivable [Line Items]
Loans, gross	1,352,465	1,515,227
Allowance for loan losses	(6,786)	(3,678)	(3,320)	(3,447)
Real estate | Single-family interim construction
Accounts Notes And Loans Receivable [Line Items]
Loans, gross	326,575	378,120
Allowance for loan losses	(2,156)	(1,606)	(1,402)	(1,583)
Agricultural
Accounts Notes And Loans Receivable [Line Items]
Loans, gross	85,014	97,767
Allowance for loan losses	(337)	(332)	(241)	(250)
Consumer
Accounts Notes And Loans Receivable [Line Items]
Loans, gross	66,952	32,603
Allowance for loan losses	(442)	(226)	(186)	(205)
Other
Accounts Notes And Loans Receivable [Line Items]
Loans, gross	346	621
Allowance for loan losses	$ (242)	$ (5)	$ (3)	$ 32

Loans, Net and Allowance for _4

Loans, Net and Allowance for Loan Losses - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)modified_loancontractcomponent	Dec. 31, 2019USD ($)modified_loan
Accounts Notes And Loans Receivable [Line Items]
Loans, net amount	$ 12,978,238,000	$ 11,562,814,000
Number of components the allowance is derived from | component	2
Troubled debt restructuring modification recorded investment	$ 2,564,000	$ 1,208,000
Number of loans modified under troubled debt restructuring | modified_loan	0	0
Commitments to lend additional funds	$ 0	$ 0
Payment Deferral [Member] | Temporary Modification
Accounts Notes And Loans Receivable [Line Items]
COVID-19 deferrals, number of loans | contract	1,298
COVID-19 deferrals, deferred accrued interest	$ 22,128,000
COVID-19 deferrals, outstanding balance	1,651,376,000
Receivables Acquired with Deteriorated Credit Quality
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	6,699,000	10,850,000
Allowance for loan losses on PCI loans	$ 194,000	849,000
Loans and Leases, Net | COLORADO | Geographic Concentration Risk
Accounts Notes And Loans Receivable [Line Items]
Percentage of portfolio	24.00%
Owner Occupied | Loans and Leases, Net
Accounts Notes And Loans Receivable [Line Items]
Percentage of portfolio	29.00%
Commercial | Paycheck Protection Program
Accounts Notes And Loans Receivable [Line Items]
PPP interest rate	1.00%
PPP loans outstanding	$ 804,397,000
PPP deferred loan fees	(9,770,000)
Commercial | Receivables Acquired with Deteriorated Credit Quality
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses on PCI loans	194,000	379,000
Commercial | Energy Related Loans
Accounts Notes And Loans Receivable [Line Items]
Loans, net amount	205,496,000	189,781,000
Commercial | Warehouse Loans
Accounts Notes And Loans Receivable [Line Items]
Loans, net amount	$ 1,453,797,000	687,317,000
Duration of the loans to larger mortgage originators	60 days
Agricultural | Receivables Acquired with Deteriorated Credit Quality
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses on PCI loans	$ 0	0
Agricultural | Agricultural
Accounts Notes And Loans Receivable [Line Items]
Loan to value ratio (percent)	80.00%
Loan, amortization period	20 years
Agricultural | Non-Real Estate Loan
Accounts Notes And Loans Receivable [Line Items]
Period of operating lines	1 year
Consumer
Accounts Notes And Loans Receivable [Line Items]
Percentage of portfolio	1.00%
Consumer | Receivables Acquired with Deteriorated Credit Quality
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses on PCI loans	$ 0	$ 0
Maximum | Commercial | Paycheck Protection Program
Accounts Notes And Loans Receivable [Line Items]
PPP term	5 years
Maximum | Commercial | Warehouse Loans
Accounts Notes And Loans Receivable [Line Items]
Duration of the loans to mortgage bankers	15 days
Minimum
Accounts Notes And Loans Receivable [Line Items]
Loans requiring external review	$ 3,500,000
Minimum | Commercial | Paycheck Protection Program
Accounts Notes And Loans Receivable [Line Items]
PPP term	2 years

Loans, Net and Allowance for _5

Loans, Net and Allowance for Loan Losses - Rollforward of Activity in Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	$ 51,461	$ 44,802	$ 39,402
Provision for loan losses	42,993	14,805	9,860
Charge-offs	(6,873)	(8,364)	(4,625)
Recoveries	239	218	165
Balance at end of year	87,820	51,461	44,802
Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	12,844	11,793	10,599
Provision for loan losses	20,025	8,670	4,973
Charge-offs	(5,670)	(7,709)	(3,863)
Recoveries	112	90	84
Balance at end of year	27,311	12,844	11,793
Real estate | Commercial real estate, construction, land and land development
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	33,085	27,795	23,301
Provision for loan losses	17,769	5,289	4,909
Charge-offs	(735)	(3)	(435)
Recoveries	4	4	20
Balance at end of year	50,123	33,085	27,795
Real estate | Residential Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	3,678	3,320	3,447
Provision for loan losses	3,108	498	(124)
Charge-offs	0	(140)	(6)
Recoveries	0	0	3
Balance at end of year	6,786	3,678	3,320
Real estate | Single-family interim construction
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	1,606	1,402	1,583
Provision for loan losses	632	207	(181)
Charge-offs	(82)	(3)	0
Recoveries	0	0	0
Balance at end of year	2,156	1,606	1,402
Agricultural
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	332	241	250
Provision for loan losses	5	91	(9)
Charge-offs	0	0	0
Recoveries	0	0	0
Balance at end of year	337	332	241
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	226	186	205
Provision for loan losses	223	71	69
Charge-offs	(44)	(79)	(93)
Recoveries	37	48	5
Balance at end of year	442	226	186
Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	5	3	(32)
Provision for loan losses	493	356	210
Charge-offs	(342)	(430)	(228)
Recoveries	86	76	53
Balance at end of year	242	5	3
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	(315)	62	49
Provision for loan losses	738	(377)	13
Charge-offs	0	0	0
Recoveries	0	0	0
Balance at end of year	$ 423	$ (315)	$ 62

Loans, Net and Allowance for _6

Loans, Net and Allowance for Loan Losses - Summary of Activity in Allowance for Loan Losses by Loan Class (Details) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for loan losses:
Individually evaluated for impairment	$ 8,524	$ 358
Collectively evaluated for impairment	79,102	50,254
Ending balance	87,820	51,461	$ 44,802	$ 39,402
Loans:
Individually evaluated for impairment	64,383	12,087
Collectively evaluated for impairment	12,796,926	11,311,238
Ending balance	13,076,095	11,615,970
Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Loans acquired with deteriorated credit quality	194	849
Loans:
Acquired with deteriorated credit quality	214,786	292,645
Ending balance	214,786	292,645
Commercial
Allowance for loan losses:
Individually evaluated for impairment	8,281	357
Collectively evaluated for impairment	18,836	12,108
Ending balance	27,311	12,844	11,793	10,599
Loans:
Individually evaluated for impairment	39,298	3,130
Collectively evaluated for impairment	3,823,982	2,416,569
Ending balance	3,902,266	2,482,356
Commercial | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Loans acquired with deteriorated credit quality	194	379
Loans:
Acquired with deteriorated credit quality	38,986	62,657
Real estate | Commercial real estate, construction, land and land development
Allowance for loan losses:
Individually evaluated for impairment	243	0
Collectively evaluated for impairment	49,880	32,615
Ending balance	50,123	33,085	27,795	23,301
Loans:
Individually evaluated for impairment	21,880	6,813
Collectively evaluated for impairment	7,149,610	6,883,639
Ending balance	7,342,477	7,109,276
Real estate | Commercial real estate, construction, land and land development | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Loans acquired with deteriorated credit quality	0	470
Loans:
Acquired with deteriorated credit quality	170,987	218,824
Real estate | Residential Real Estate
Allowance for loan losses:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	6,786	3,678
Ending balance	6,786	3,678	3,320	3,447
Loans:
Individually evaluated for impairment	2,550	2,008
Collectively evaluated for impairment	1,345,234	1,505,896
Ending balance	1,352,465	1,515,227
Real estate | Residential Real Estate | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Loans acquired with deteriorated credit quality	0	0
Loans:
Acquired with deteriorated credit quality	4,681	7,323
Real estate | Single-family interim construction
Allowance for loan losses:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	2,156	1,606
Ending balance	2,156	1,606	1,402	1,583
Loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	326,575	378,120
Ending balance	326,575	378,120
Real estate | Single-family interim construction | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Loans acquired with deteriorated credit quality	0	0
Loans:
Acquired with deteriorated credit quality	0	0
Agricultural
Allowance for loan losses:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	337	332
Ending balance	337	332	241	250
Loans:
Individually evaluated for impairment	613	114
Collectively evaluated for impairment	84,284	93,837
Ending balance	85,014	97,767
Agricultural | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Loans acquired with deteriorated credit quality	0	0
Loans:
Acquired with deteriorated credit quality	117	3,816
Consumer
Allowance for loan losses:
Individually evaluated for impairment	0	1
Collectively evaluated for impairment	442	225
Ending balance	442	226	186	205
Loans:
Individually evaluated for impairment	42	22
Collectively evaluated for impairment	66,895	32,556
Ending balance	66,952	32,603
Consumer | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Loans acquired with deteriorated credit quality	0	0
Loans:
Acquired with deteriorated credit quality	15	25
Other
Allowance for loan losses:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	242	5
Ending balance	242	5	3	(32)
Loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	346	621
Ending balance	346	621
Other | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Loans acquired with deteriorated credit quality	0	0
Loans:
Acquired with deteriorated credit quality	0	0
Unallocated
Allowance for loan losses:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	423	(315)
Ending balance	423	(315)	$ 62	$ 49
Loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	0	0
Ending balance	0	0
Unallocated | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses:
Loans acquired with deteriorated credit quality	0	0
Loans:
Acquired with deteriorated credit quality	$ 0	$ 0

Loans, Net and Allowance for _7

Loans, Net and Allowance for Loan Losses - Summary of Non Performing Loans by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Troubled debt restructurings (not included in nonaccrual or loans past due and still accruing)	$ 2,564	$ 1,208
Nonperforming Loans
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	48,997	11,547
Loans past due 90 days and still accruing	433	14,529
Troubled debt restructurings (not included in nonaccrual or loans past due and still accruing)	1,986	540
Total nonperforming loans	51,416	26,616
Nonperforming Loans | Commercial
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	25,898	3,130
Loans past due 90 days and still accruing	433	14,529
Troubled debt restructurings (not included in nonaccrual or loans past due and still accruing)	0	0
Total nonperforming loans	26,331	17,659
Nonperforming Loans | Real estate | Commercial real estate, construction, land and land development
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	20,072	6,461
Loans past due 90 days and still accruing	0	0
Troubled debt restructurings (not included in nonaccrual or loans past due and still accruing)	1,808	352
Total nonperforming loans	21,880	6,813
Nonperforming Loans | Real estate | Residential Real Estate
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	2,372	1,820
Loans past due 90 days and still accruing	0	0
Troubled debt restructurings (not included in nonaccrual or loans past due and still accruing)	178	188
Total nonperforming loans	2,550	2,008
Nonperforming Loans | Real estate | Single-family interim construction
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	0	0
Loans past due 90 days and still accruing	0	0
Troubled debt restructurings (not included in nonaccrual or loans past due and still accruing)	0	0
Total nonperforming loans	0	0
Nonperforming Loans | Agricultural
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	613	114
Loans past due 90 days and still accruing	0	0
Troubled debt restructurings (not included in nonaccrual or loans past due and still accruing)	0	0
Total nonperforming loans	613	114
Nonperforming Loans | Consumer
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	42	22
Loans past due 90 days and still accruing	0	0
Troubled debt restructurings (not included in nonaccrual or loans past due and still accruing)	0	0
Total nonperforming loans	42	22
Nonperforming Loans | Other
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	0	0
Loans past due 90 days and still accruing	0	0
Troubled debt restructurings (not included in nonaccrual or loans past due and still accruing)	0	0
Total nonperforming loans	$ 0	$ 0

Loans, Net and Allowance for _8

Loans, Net and Allowance for Loan Losses - Impaired Loans by Loan Class (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Recorded investment in impaired loans:
Impaired loans with an allowance for loan losses	$ 25,015	$ 1,581
Impaired loans with no allowance for loan losses	39,368	10,506
Total	64,383	12,087
Unpaid principal balance of impaired loans	89,796	17,891
Allowance for loan losses on impaired loans	8,524	358
Average recorded investment in impaired loans	33,890	12,794	$ 14,381
Interest income recognized on impaired loans	515	233	268
Commercial
Recorded investment in impaired loans:
Impaired loans with an allowance for loan losses	24,540	1,580
Impaired loans with no allowance for loan losses	14,758	1,550
Total	39,298	3,130
Unpaid principal balance of impaired loans	63,817	8,580
Allowance for loan losses on impaired loans	8,281	357
Average recorded investment in impaired loans	21,559	6,266	8,919
Interest income recognized on impaired loans	168	30	119
Real estate | Commercial real estate, construction, land and land development
Recorded investment in impaired loans:
Impaired loans with an allowance for loan losses	475	0
Impaired loans with no allowance for loan losses	21,405	6,813
Total	21,880	6,813
Unpaid principal balance of impaired loans	22,543	6,967
Allowance for loan losses on impaired loans	243	0
Average recorded investment in impaired loans	9,497	3,979	2,667
Interest income recognized on impaired loans	139	39	65
Real estate | Residential Real Estate
Recorded investment in impaired loans:
Impaired loans with an allowance for loan losses	0	0
Impaired loans with no allowance for loan losses	2,550	2,008
Total	2,550	2,008
Unpaid principal balance of impaired loans	2,742	2,197
Allowance for loan losses on impaired loans	0	0
Average recorded investment in impaired loans	2,362	1,746	2,033
Interest income recognized on impaired loans	208	39	81
Real estate | Single-family interim construction
Recorded investment in impaired loans:
Impaired loans with an allowance for loan losses	0	0
Impaired loans with no allowance for loan losses	0	0
Total	0	0
Unpaid principal balance of impaired loans	0	0
Allowance for loan losses on impaired loans	0	0
Average recorded investment in impaired loans	0	716	716
Interest income recognized on impaired loans	0	119	1
Agricultural
Recorded investment in impaired loans:
Impaired loans with an allowance for loan losses	0	0
Impaired loans with no allowance for loan losses	613	114
Total	613	114
Unpaid principal balance of impaired loans	650	123
Allowance for loan losses on impaired loans	0	0
Average recorded investment in impaired loans	442	57	0
Interest income recognized on impaired loans	0	0	0
Consumer
Recorded investment in impaired loans:
Impaired loans with an allowance for loan losses	0	1
Impaired loans with no allowance for loan losses	42	21
Total	42	22
Unpaid principal balance of impaired loans	44	24
Allowance for loan losses on impaired loans	0	1
Average recorded investment in impaired loans	30	30	46
Interest income recognized on impaired loans	0	6	2
Other
Recorded investment in impaired loans:
Impaired loans with an allowance for loan losses	0	0
Impaired loans with no allowance for loan losses	0	0
Total	0	0
Unpaid principal balance of impaired loans	0	0
Allowance for loan losses on impaired loans	0	0
Average recorded investment in impaired loans	0	0	0
Interest income recognized on impaired loans	$ 0	$ 0	$ 0

Loans, Net and Allowance for _9

Loans, Net and Allowance for Loan Losses - Summary of Troubled Debt Restructurings (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)contract	Dec. 31, 2019USD ($)contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	1	1
Pre-restructuring outstanding recorded investment	$ 1,517	$ 29
Post-restructuring outstanding recorded investment	$ 1,517	$ 29
Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	0	0
Pre-restructuring outstanding recorded investment	$ 0	$ 0
Post-restructuring outstanding recorded investment	$ 0	$ 0
Real estate | Commercial real estate, construction, land and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	1	0
Pre-restructuring outstanding recorded investment	$ 1,517	$ 0
Post-restructuring outstanding recorded investment	$ 1,517	$ 0
Real estate | Residential Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	0	1
Pre-restructuring outstanding recorded investment	$ 0	$ 29
Post-restructuring outstanding recorded investment	$ 0	$ 29
Real estate | Single-family interim construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	0	0
Pre-restructuring outstanding recorded investment	$ 0	$ 0
Post-restructuring outstanding recorded investment	$ 0	$ 0
Agricultural
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	0	0
Pre-restructuring outstanding recorded investment	$ 0	$ 0
Post-restructuring outstanding recorded investment	$ 0	$ 0
Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	0	0
Pre-restructuring outstanding recorded investment	$ 0	$ 0
Post-restructuring outstanding recorded investment	$ 0	$ 0
Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	0	0
Pre-restructuring outstanding recorded investment	$ 0	$ 0
Post-restructuring outstanding recorded investment	$ 0	$ 0

Loans, Net and Allowance for_10

Loans, Net and Allowance for Loan Losses - Aging of Past Due Loans by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	$ 45,881	$ 50,593
Current Loans	13,030,214	11,565,377
Ending balance	13,076,095	11,615,970
Loans 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	11,575	22,488
Loans 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	34,306	28,105
Commercial
Financing Receivable, Past Due [Line Items]
Ending balance	3,902,266	2,482,356
Real estate | Commercial real estate, construction, land and land development
Financing Receivable, Past Due [Line Items]
Ending balance	7,342,477	7,109,276
Real estate | Residential Real Estate
Financing Receivable, Past Due [Line Items]
Ending balance	1,352,465	1,515,227
Real estate | Single-family interim construction
Financing Receivable, Past Due [Line Items]
Ending balance	326,575	378,120
Agricultural
Financing Receivable, Past Due [Line Items]
Ending balance	85,014	97,767
Consumer
Financing Receivable, Past Due [Line Items]
Ending balance	66,952	32,603
Other
Financing Receivable, Past Due [Line Items]
Ending balance	346	621
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	3,843	9,322
Current Loans	210,943	283,323
Ending balance	214,786	292,645
Receivables Acquired with Deteriorated Credit Quality | Loans 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	624	2,556
Receivables Acquired with Deteriorated Credit Quality | Loans 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	3,219	6,766
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	42,038	41,271
Current Loans	12,819,271	11,282,054
Ending balance	12,861,309	11,323,325
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Loans 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	10,951	19,932
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Loans 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	31,087	21,339
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	16,470	22,168
Current Loans	3,846,810	2,397,531
Ending balance	3,863,280	2,419,699
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial | Loans 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	3,243	4,512
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial | Loans 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	13,227	17,656
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Real estate | Commercial real estate, construction, land and land development
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	19,243	12,058
Current Loans	7,152,247	6,878,394
Ending balance	7,171,490	6,890,452
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Real estate | Commercial real estate, construction, land and land development | Loans 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	2,453	9,153
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Real estate | Commercial real estate, construction, land and land development | Loans 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	16,790	2,905
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Real estate | Residential Real Estate
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	6,197	3,884
Current Loans	1,341,587	1,504,020
Ending balance	1,347,784	1,507,904
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Real estate | Residential Real Estate | Loans 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	5,169	3,242
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Real estate | Residential Real Estate | Loans 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	1,028	642
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Real estate | Single-family interim construction
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	0	2,836
Current Loans	326,575	375,284
Ending balance	326,575	378,120
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Real estate | Single-family interim construction | Loans 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	0	2,836
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Real estate | Single-family interim construction | Loans 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	0	0
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Agricultural
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	1	136
Current Loans	84,896	93,815
Ending balance	84,897	93,951
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Agricultural | Loans 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	0	22
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Agricultural | Loans 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	1	114
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	127	189
Current Loans	66,810	32,389
Ending balance	66,937	32,578
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer | Loans 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	86	167
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer | Loans 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	41	22
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Other
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	0	0
Current Loans	346	621
Ending balance	346	621
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Other | Loans 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	0	0
Financing Receivables, Excluding Receivables Acquired with Deteriorated Credit Quality [Member] | Other | Loans 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due Loans	$ 0	$ 0

Loans, Net and Allowance for_11

Loans, Net and Allowance for Loan Losses - Summary of Loans by Credit Quality Indicator (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	$ 13,076,095	$ 11,615,970
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	214,786	292,645
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	12,006,267	11,146,421
Pass | Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	117,896	232,095
Pass/ Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	424,143	267,765
Pass/ Watch | Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	45,672	21,284
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	406,080	87,488
Special Mention | Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	32,557	4,502
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	229,514	114,296
Substandard | Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	18,661	34,764
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	10,091	0
Doubtful | Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	0	0
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	3,902,266	2,482,356
Commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	3,700,626	2,332,611
Commercial | Pass/ Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	55,960	71,642
Commercial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	38,186	37,739
Commercial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	97,403	40,364
Commercial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	10,091	0
Real estate | Commercial real estate, construction, land and land development
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	7,342,477	7,109,276
Real estate | Commercial real estate, construction, land and land development | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	6,504,933	6,814,780
Real estate | Commercial real estate, construction, land and land development | Pass/ Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	352,910	184,720
Real estate | Commercial real estate, construction, land and land development | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	360,963	46,889
Real estate | Commercial real estate, construction, land and land development | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	123,671	62,887
Real estate | Commercial real estate, construction, land and land development | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	0	0
Real estate | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	1,352,465	1,515,227
Real estate | Residential Real Estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	1,332,757	1,501,019
Real estate | Residential Real Estate | Pass/ Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	6,296	4,850
Real estate | Residential Real Estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	5,726	994
Real estate | Residential Real Estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	7,686	8,364
Real estate | Residential Real Estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	0	0
Real estate | Single-family interim construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	326,575	378,120
Real estate | Single-family interim construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	323,800	376,887
Real estate | Single-family interim construction | Pass/ Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	2,775	1,233
Real estate | Single-family interim construction | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	0	0
Real estate | Single-family interim construction | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	0	0
Real estate | Single-family interim construction | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	0	0
Agricultural
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	85,014	97,767
Agricultural | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	76,951	88,044
Agricultural | Pass/ Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	6,194	5,287
Agricultural | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	1,205	1,864
Agricultural | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	664	2,572
Agricultural | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	0	0
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	66,952	32,603
Consumer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	66,854	32,459
Consumer | Pass/ Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	8	33
Consumer | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	0	2
Consumer | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	90	109
Consumer | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	0	0
Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	346	621
Other | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	346	621
Other | Pass/ Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	0	0
Other | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	0	0
Other | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	0	0
Other | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross	$ 0	$ 0

Loans, Net and Allowance for_12

Loans, Net and Allowance for Loan Losses - Outstanding Balance and Related Carrying Amount of Purchased Impaired Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Business Acquisition [Line Items]
Outstanding balance	$ 237,786	$ 326,077
Carrying amount	$ 214,786	$ 292,645
Guaranty Bancorp
Business Acquisition [Line Items]
Outstanding balance			$ 341,645
Nonaccretable difference			(16,622)
Accretable yield			(13,299)
Carrying amount			$ 311,724

Loans, Net and Allowance for_13

Loans, Net and Allowance for Loan Losses - Purchased Credit Impaired Loans in Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Receivables [Abstract]
Outstanding balance	$ 237,786	$ 326,077
Carrying amount	$ 214,786	$ 292,645

Loans, Net and Allowance for_14

Loans, Net and Allowance for Loan Losses - Accretable Yield Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at January 1	$ 8,905	$ 1,436
Additions	0	13,299
Accretion	(3,287)	(5,830)
Transfers from nonaccretable	0	0
Balance at December 31	$ 5,618	$ 8,905

Premises and Equipment, Net - C

Premises and Equipment, Net - Components of Premises and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Land	$ 65,103	$ 58,643
Building	191,940	184,589
Furniture, fixtures and equipment	39,282	39,855
Aircraft	8,947	8,947
Leasehold and tenant improvements	5,798	5,466
Construction in progress	915	834
Premises and equipment, gross	311,985	298,334
Less accumulated depreciation	(62,518)	(55,460)
Premises and equipment, net	$ 249,467	$ 242,874

Premises and Equipment, Net - A

Premises and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 12,728	$ 11,783	$ 8,391

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill And Other Intangible Assets [Line Items]
Goodwill	$ 994,021	$ 994,021
Amortization of other intangible assets	$ 12,671	12,880	$ 5,739
Remaining weighted averaged amortization period	7 years 4 months 24 days
Guaranty Bancorp
Goodwill And Other Intangible Assets [Line Items]
Goodwill		272,224
Goodwill, acquired during period		$ 272,224

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets, Net - Gross Carrying Value and Accumulated Amortization of Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Total other intangible assets, net	$ 88,070	$ 100,741
Core deposit intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Balance at beginning of the year	125,884	63,891
Additions: Guaranty acquisition	0	61,993
Balance at end of the year	125,884	125,884
Less accumulated amortization	(43,235)	(31,057)
Total other intangible assets, net	82,649	94,827
Customer relationship intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Balance at beginning of the year	6,407	0
Additions: Guaranty acquisition	0	9,525
Deletions: sale of trust business	0	(3,118)
Balance at end of the year	6,407	6,407
Less accumulated amortization	(986)	(493)
Total other intangible assets, net	$ 5,421	$ 5,914

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets, Net - Future Amortization Expense Related to Core Deposit Intangible (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
First year	$ 12,580
Second year	12,491
Third year	12,439
Fourth year	11,752
Fifth year	11,238
Thereafter	27,570
Future amortization expense	$ 88,070

Deposits - Components of Deposi

Deposits - Components of Deposits (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Amount
Noninterest-bearing demand accounts	$ 4,164,800	$ 3,240,185
Interest-bearing checking accounts	5,420,548	4,198,772
Savings accounts	654,733	552,585
Limited access money market accounts	2,743,208	2,119,878
Certificates of deposit and individual retirement accounts (IRA), less than $250,000	675,329	892,639
Certificates of deposit and individual retirement accounts (IRA), $250,000 and greater	740,309	937,277
Total deposits	$ 14,398,927	$ 11,941,336
Percent
Noninterest-bearing demand accounts (percent)	28.90%	27.10%
Interest-bearing checking accounts (percent)	37.60%	35.20%
Savings accounts (percent)	4.60%	4.60%
Limited access money market accounts (percent)	19.10%	17.80%
Certificates of deposit and individual retirement accounts (IRA), less than $250,000 (percent)	4.70%	7.50%
Certificates of deposit and individual retirement account (IRA), $250,000 and greater (percent)	5.10%	7.80%
Total deposits (percent)	100.00%	100.00%

Deposits - Maturities of Certif

Deposits - Maturities of Certificates of Deposit (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Time Deposits, Fiscal Year Maturity [Abstract]
First year	$ 1,263,633
Second year	117,521
Third year	19,362
Fourth year	5,058
Fifth year	10,059
Thereafter	5
Total	$ 1,415,638

Deposits - Additional Informati

Deposits - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deposits [Abstract]
Brokered deposit	$ 1,521,129	$ 894,131

Federal Home Loan Bank Advanc_3

Federal Home Loan Bank Advances - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Weighted average interest rate on advances (percent)	0.57%	2.17%
Outstanding balances of advances	$ 375,000	$ 325,000
Federal Home Loan Bank Stock	17,156
Carrying value of loans with blanket lien	5,708,883
Remaining credit facility under FHLB advances	4,091,643
Federal Home Loan Bank Advances
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Undisbursed advance commitments (letter of credit)	$ 1,240,851

Federal Home Loan Bank Advanc_4

Federal Home Loan Bank Advances - Schedule of Outstanding Balances on Advances (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Federal Home Loan Bank, Advances, Fiscal Year Maturity [Abstract]
First year	$ 25,000
Second year	0
Third year	200,000
Fourth year	0
Fifth year	0
Thereafter	150,000
FHLB advances	$ 375,000	$ 325,000

Other Borrowings - Other Borrow

Other Borrowings - Other Borrowings (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Other borrowings	$ 312,175,000	$ 202,251,000
Other borrowings, related parties	50,000	50,000
5.875% Subordinated Notes Due August 1, 2024
Debt Instrument [Line Items]
Subordinated debt	108,729,000	108,372,000
Debt original amount	$ 110,000,000	110,000,000
Stated interest rate (percent)	5.875%
Discount and origination costs	$ 1,271,000	1,628,000
5.75% Subordinated Debenture Notes Due July 20, 2026
Debt Instrument [Line Items]
Subordinated debt	40,000,000	40,000,000
Debt original amount	$ 40,000,000	40,000,000
Stated interest rate (percent)	5.75%
5.00% Subordinated Debenture Notes Due December 31, 2027
Debt Instrument [Line Items]
Subordinated debt	$ 29,457,000	29,379,000
Debt original amount	$ 30,000,000	30,000,000
Stated interest rate (percent)	5.00%
Origination costs	$ 543,000	621,000
Unsecured Subordinated Debenture Notes Due September 15, 2030
Debt Instrument [Line Items]
Subordinated debt	127,489,000	0
Debt original amount	$ 130,000,000
Stated interest rate (percent)	4.00%
Origination costs	$ 2,511,000
London Interbank Offered Rate (LIBOR) | 5.75% Subordinated Debenture Notes Due July 20, 2026
Debt Instrument [Line Items]
Basis spread on variable rate	4.73%
London Interbank Offered Rate (LIBOR) | 5.00% Subordinated Debenture Notes Due December 31, 2027
Debt Instrument [Line Items]
Basis spread on variable rate	2.83%
Secured Overnight Financing Rate (SOFR) | Unsecured Subordinated Debenture Notes Due September 15, 2030
Debt Instrument [Line Items]
Basis spread on variable rate	3.885%
Line of Credit | Line of Credit | Revolving line of credit
Debt Instrument [Line Items]
Line of Credit Facility, Outstanding Balance	$ 6,500,000	$ 24,500,000
Line of credit, maximum capacity	$ 100,000,000
Line of Credit | Line of Credit | London Interbank Offered Rate (LIBOR) | Revolving line of credit
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%

Other Borrowings - Additional I

Other Borrowings - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)unaffiliated_bankNumber_of_Lines	Dec. 31, 2019USD ($)unaffiliated_bank
Federal Funds Line of Credit | Line of Credit
Line of Credit Facility [Line Items]
Line of credit, maximum capacity	$ 365,000,000	$ 375,000,000
Outstanding borrowings on line of credit	$ 0	$ 0
Number of unaffiliated banks | unaffiliated_bank	9	10
Secured Debt | Line of Credit
Line of Credit Facility [Line Items]
Line of credit, maximum capacity	$ 716,700,000	$ 895,110,000
Outstanding borrowings on line of credit	0	0
Line of credit, collateral	1,034,467,000	1,196,491,000
Direct Overnight Borrowings | Unsecured Debt | Line of Credit
Line of Credit Facility [Line Items]
Line of credit, maximum capacity	694,000,000	484,000,000
Outstanding borrowings on line of credit	0	$ 0
Line of Credit | Federal Funds Line of Credit
Line of Credit Facility [Line Items]
Line of credit, maximum capacity	$ 30,000,000
Number of lines | Number_of_Lines	2

Junior Subordinated Debenture_2

Junior Subordinated Debentures - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)business_trust	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
Number of wholly owned statutory business trusts | business_trust	9
Trust Preferred Securities Issued	$ 57,324
Junior subordinated debentures, carrying value	54,023	$ 53,824
Junior subordinated debentures, unamortized discount	3,301
IB Trust I
Debt Instrument [Line Items]
Trust Preferred Securities Issued	5,155
Junior subordinated debentures, carrying value	$ 5,155
Interest Rate	3.46%
Guaranty Trust III
Debt Instrument [Line Items]
Trust Preferred Securities Issued	$ 10,310
Junior subordinated debentures, carrying value	$ 10,310
Interest Rate	3.34%
IB Trust II
Debt Instrument [Line Items]
Trust Preferred Securities Issued	$ 3,093
Junior subordinated debentures, carrying value	$ 3,093
Interest Rate	3.09%
Cenbank Trust III
Debt Instrument [Line Items]
Trust Preferred Securities Issued	$ 15,464
Junior subordinated debentures, carrying value	$ 15,464
Interest Rate	2.89%
IB Trust III
Debt Instrument [Line Items]
Trust Preferred Securities Issued	$ 3,712
Junior subordinated debentures, carrying value	$ 3,712
Interest Rate	2.61%
IB Centex Trust I
Debt Instrument [Line Items]
Trust Preferred Securities Issued	$ 2,578
Junior subordinated debentures, carrying value	$ 2,578
Interest Rate	3.46%
Community Group Statutory Trust I
Debt Instrument [Line Items]
Trust Preferred Securities Issued	$ 3,609
Junior subordinated debentures, carrying value	$ 3,609
Interest Rate	1.82%
Northstar Trust II
Debt Instrument [Line Items]
Trust Preferred Securities Issued	$ 5,155
Junior subordinated debentures, carrying value	$ 3,892
Interest Rate	1.89%
Northstar Trust III
Debt Instrument [Line Items]
Trust Preferred Securities Issued	$ 8,248
Junior subordinated debentures, carrying value	$ 6,210
Interest Rate	1.89%
London Interbank Offered Rate (LIBOR) | IB Trust I
Debt Instrument [Line Items]
Description of variable rate basis	LIBOR
Interest Rate Index	3.25%
London Interbank Offered Rate (LIBOR) | Guaranty Trust III
Debt Instrument [Line Items]
Description of variable rate basis	LIBOR
Interest Rate Index	3.10%
London Interbank Offered Rate (LIBOR) | IB Trust II
Debt Instrument [Line Items]
Description of variable rate basis	LIBOR
Interest Rate Index	2.85%
London Interbank Offered Rate (LIBOR) | Cenbank Trust III
Debt Instrument [Line Items]
Description of variable rate basis	LIBOR
Interest Rate Index	2.65%
London Interbank Offered Rate (LIBOR) | IB Trust III
Debt Instrument [Line Items]
Description of variable rate basis	LIBOR
Interest Rate Index	2.40%
London Interbank Offered Rate (LIBOR) | IB Centex Trust I
Debt Instrument [Line Items]
Description of variable rate basis	LIBOR
Interest Rate Index	3.25%
London Interbank Offered Rate (LIBOR) | Community Group Statutory Trust I
Debt Instrument [Line Items]
Description of variable rate basis	LIBOR
Interest Rate Index	1.60%
London Interbank Offered Rate (LIBOR) | Northstar Trust II
Debt Instrument [Line Items]
Description of variable rate basis	LIBOR
Interest Rate Index	1.67%
London Interbank Offered Rate (LIBOR) | Northstar Trust III
Debt Instrument [Line Items]
Description of variable rate basis	LIBOR
Interest Rate Index	1.67%

Leases - Additional Information

Leases - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)branch	Dec. 31, 2018USD ($)	Dec. 31, 2019USD ($)
Lessee, Lease, Description [Line Items]
Number of branches leased | branch	21
Number of branches operated | branch	93
Right-of-use assets	$ 24,841		$ 38,813
Lease liability	$ 23,413		$ 28,978
Operating lease expense		$ 3,758
Minimum
Lessee, Lease, Description [Line Items]
Operating leases, remaining term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Operating leases, remaining term	30 years

Leases - Schedule of Net Lease

Leases - Schedule of Net Lease Cost and Other Information Related to Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 6,937	$ 7,025
Short term lease cost	124	103
Variable lease cost	1,631	1,829
Sublease income	(221)	(228)
Net lease cost	8,471	8,729
Operating cash flows from operating leases	$ 6,091	$ 6,965
Weighted average remaining lease term - operating leases, in years	7 years 2 months 23 days	7 years 6 months 29 days
Weighted average discount rate - operating leases	3.47%	3.35%

Leases - Summary of Lease Liabi

Leases - Summary of Lease Liability Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
2021	$ 5,615
2022	4,876
2023	4,054
2024	3,438
2025	2,754
Thereafter	5,700
Total lease payments	26,437
Less imputed interest	(3,024)
Lease liability	$ 23,413	$ 28,978

Income Taxes - Tax Expense (Det

Income Taxes - Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Current income tax expense	$ 52,806	$ 39,426	$ 29,801
Deferred income tax (benefit) expense	(1,633)	14,102	2,000
Deferred income tax benefit related to remeasurement of deferred taxes	0	0	(63)
Income tax expense, as reported	$ 51,173	$ 53,528	$ 31,738

Income Taxes - Tax Reconciliati

Income Taxes - Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax expense computed at the statutory rate	$ 53,000	$ 51,715	$ 33,599
Tax-exempt interest income from municipal securities	(1,779)	(1,781)	(962)
Tax-exempt loan income	(1,245)	(1,174)	(490)
Bank owned life insurance income	(1,123)	(1,288)	(666)
Non-deductible acquisition expenses	0	281	142
State taxes, net of federal benefit	2,660	3,455	375
Non-deductible compensation	0	2,017	0
Net tax expense (benefit) from stock based compensation	243	21	(646)
Deferred tax adjustment related to reduction in U.S. Federal statutory income tax rate	0	0	(63)
Other	(583)	282	449
Income tax expense, as reported	$ 51,173	$ 53,528	$ 31,738

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Allowance for loan losses	$ 19,238	$ 11,466
Lease liabilities under operating leases	5,129	6,457
NOL and tax credit carryforwards from acquisitions	3,718	4,209
Acquired loan fair market value adjustments	12,986	21,645
Stock-based compensation	1,567	1,218
Reserve for bonuses and other accrued expenses	3,409	2,773
Acquisition costs	0	416
Acquired securities	2,095	2,529
Acquired intangibles	1,369	1,546
Start up costs	171	230
Other real estate owned	0	362
Unearned income	715	774
Deferred compensation	857	1,101
Noncompete agreements	597	663
Nonaccrual loans	550	390
Other	727	785
Deferred tax assets, gross	53,128	56,564
Deferred tax liabilities:
Premises and equipment	(12,392)	(13,170)
Right-of-use assets under operating leases	(4,911)	(6,233)
Deferred Tax Liabilities, Unrealized Gains on Available-for-sale Securities	(9,501)	(5,367)
Intangible assets	(19,293)	(22,447)
Acquired junior subordinated debentures fair value adjustment	(723)	(780)
PPP deferred loan costs	(952)	0
FHLB and other restricted stocks	(308)	(673)
Acquired tax goodwill	(572)	(413)
Other	(543)	(538)
Deferred tax liabilities, gross	(49,195)	(49,621)
Net deferred tax asset	$ 3,933	$ 6,943

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 0	$ 0
Federal Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	15,765,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 11,150,000

Commitments and Contingencies_2

Commitments and Contingencies (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off-balance sheet risk	$ 2,294,133	$ 2,360,791
Commitments to extend credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off-balance sheet risk	2,268,216	2,337,385
Standby letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off-balance sheet risk	$ 25,917	$ 23,406

Related Party Transactions - Lo

Related Party Transactions - Loan Activity for Officers, Directors and Affiliates (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Loans and Leases Receivable, Related Parties [Roll Forward]
Balance at beginning of year	$ 38,796
New loans	30,912
Repayments	(38,570)
Changes in affiliated persons	1,333
Balance at end of year	$ 32,471

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($)	6 Months Ended		12 Months Ended
	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan Disclosure [Line Items]
Minimum age			18 years
Credited service period			90 days
Salary reduction set by law			$ 19,500
Employer contribution, matching percentage (percent)	100.00%		100.00%	100.00%
Employer contribution as percentage of participant's eligible salary (percent)	6.00%	6.00%	6.00%	6.00%
Employer contribution, amount			$ 6,534,000	$ 6,343,000	$ 3,280,000
Minimum
Defined Contribution Plan Disclosure [Line Items]
Employer contribution, matching percentage (percent)		50.00%
Maximum
Defined Contribution Plan Disclosure [Line Items]
Employer contribution, matching percentage (percent)		100.00%

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities at Fair Value on Recurring Basis (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	$ 1,153,693,000	$ 1,085,936,000
Loans held for sale, fair value option elected	71,769,000	29,204,000
Aggregate principal balance of loans held for sale	68,670,000	28,166,000
Loans held for sale, 90 days or greater past due	0
Loans held for sale, non-accrual	0
Not designated as hedging | Interest rate lock commitments
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value	3,515,000	847,000
Liability Derivative Fair Value	0	0
Not designated as hedging | Forward mortgage-backed securities trades
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value	0	6,000
Liability Derivative Fair Value	568,000	69,000
Fair Value, Measurements, Recurring | Not designated as hedging
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Loans held for sale, fair value option elected	71,769,000	29,204,000
Fair Value, Measurements, Recurring | Not designated as hedging | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Loans held for sale, fair value option elected	0	0
Fair Value, Measurements, Recurring | Not designated as hedging | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Loans held for sale, fair value option elected	71,769,000	29,204,000
Fair Value, Measurements, Recurring | Not designated as hedging | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Loans held for sale, fair value option elected	0	0
Fair Value, Measurements, Recurring | Not designated as hedging | Interest rate lock commitments
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value	3,515,000	847,000
Fair Value, Measurements, Recurring | Not designated as hedging | Interest rate lock commitments | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value	0	0
Fair Value, Measurements, Recurring | Not designated as hedging | Interest rate lock commitments | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value	3,515,000	847,000
Fair Value, Measurements, Recurring | Not designated as hedging | Interest rate lock commitments | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value	0	0
Fair Value, Measurements, Recurring | Not designated as hedging | Forward mortgage-backed securities trades
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value		6,000
Liability Derivative Fair Value	568,000	69,000
Fair Value, Measurements, Recurring | Not designated as hedging | Forward mortgage-backed securities trades | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value		0
Liability Derivative Fair Value	0	0
Fair Value, Measurements, Recurring | Not designated as hedging | Forward mortgage-backed securities trades | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value		6,000
Liability Derivative Fair Value	568,000	69,000
Fair Value, Measurements, Recurring | Not designated as hedging | Forward mortgage-backed securities trades | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value		0
Liability Derivative Fair Value	0	0
Fair Value, Measurements, Recurring | Not designated as hedging | Interest rate swap | Loan customer counterparty
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value	20,159,000	6,104,000
Fair Value, Measurements, Recurring | Not designated as hedging | Interest rate swap | Loan customer counterparty | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value	0	0
Fair Value, Measurements, Recurring | Not designated as hedging | Interest rate swap | Loan customer counterparty | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value	20,159,000	6,104,000
Fair Value, Measurements, Recurring | Not designated as hedging | Interest rate swap | Loan customer counterparty | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Asset Derivative Fair Value	0	0
Fair Value, Measurements, Recurring | Not designated as hedging | Interest rate swap | Financial institution counterparty
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liability Derivative Fair Value	21,306,000	6,566,000
Fair Value, Measurements, Recurring | Not designated as hedging | Interest rate swap | Financial institution counterparty | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liability Derivative Fair Value	0	0
Fair Value, Measurements, Recurring | Not designated as hedging | Interest rate swap | Financial institution counterparty | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liability Derivative Fair Value	21,306,000	6,566,000
Fair Value, Measurements, Recurring | Not designated as hedging | Interest rate swap | Financial institution counterparty | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liability Derivative Fair Value	0	0
U.S. treasuries
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	44,708,000	48,796,000
U.S. treasuries | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	44,708,000	48,796,000
U.S. treasuries | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	0	0
U.S. treasuries | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	44,708,000	48,796,000
U.S. treasuries | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	0	0
Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	249,017,000	179,296,000
Government agency securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	249,017,000	179,296,000
Government agency securities | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	0	0
Government agency securities | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	249,017,000	179,296,000
Government agency securities | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	0	0
Obligations of state and municipal subdivisions
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	393,165,000	343,859,000
Obligations of state and municipal subdivisions | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	393,165,000	343,859,000
Obligations of state and municipal subdivisions | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	0	0
Obligations of state and municipal subdivisions | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	393,165,000	343,859,000
Obligations of state and municipal subdivisions | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	0	0
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	22,102,000	7,218,000
Corporate bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	22,102,000	7,218,000
Corporate bonds | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	0	0
Corporate bonds | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	22,102,000	7,218,000
Corporate bonds | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	0	0
Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	443,501,000	505,567,000
Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	443,501,000	505,567,000
Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	0	0
Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	443,501,000	505,567,000
Mortgage-backed securities guaranteed by FHLMC, FNMA and GNMA | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	0	0
Other securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	1,200,000	1,200,000
Other securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	1,200,000	1,200,000
Other securities | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	0	0
Other securities | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	1,200,000	1,200,000
Other securities | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available for sale	$ 0	$ 0

Fair Value Measurements - Ass_2

Fair Value Measurements - Assets and Liabilities at Fair Value on Nonrecurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Impaired loans	$ 64,383	$ 12,087
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Impaired loans	16,903	2,276
Other real estate owned		4,618
Fair Value, Measurements, Nonrecurring | Impaired loans
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Period Ended Total Losses	13,041	1,806
Fair Value, Measurements, Nonrecurring | Other real estate owned
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Period Ended Total Losses		749
Fair Value, Measurements, Nonrecurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Impaired loans	0	0
Other real estate owned		0
Fair Value, Measurements, Nonrecurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Impaired loans	0	0
Other real estate owned		0
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Impaired loans	$ 16,903	2,276
Other real estate owned		$ 4,618

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Amount and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Off-balance sheet assets (liabilities):
Financial instruments with off-balance sheet risk	$ 2,294,133	$ 2,360,791
Commitments to extend credit
Off-balance sheet assets (liabilities):
Financial instruments with off-balance sheet risk	2,268,216	2,337,385
Standby letters of credit
Off-balance sheet assets (liabilities):
Financial instruments with off-balance sheet risk	25,917	23,406
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	1,813,987	565,170
Certificates of deposit held in other banks	0	0
Loans held for sale, at cost	0	0
Loans, net	0	0
FHLB of Dallas stock and other restricted stock	0	0
Accrued interest receivable	0	0
Financial liabilities:
Deposits	0	0
Accrued interest payable	0	0
FHLB advances	0	0
Other borrowings	0	0
Junior subordinated debentures	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commitments to extend credit
Off-balance sheet assets (liabilities):
Financial instruments with off-balance sheet risk	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Standby letters of credit
Off-balance sheet assets (liabilities):
Financial instruments with off-balance sheet risk	0	0
Significant Other Observable Inputs (Level 2)
Financial assets:
Cash and cash equivalents	0	0
Certificates of deposit held in other banks	4,595	5,951
Loans held for sale, at cost	11,138	6,554
Loans, net	0	0
FHLB of Dallas stock and other restricted stock	20,305	30,052
Accrued interest receivable	60,581	35,860
Financial liabilities:
Deposits	14,407,596	11,958,939
Accrued interest payable	7,397	9,583
FHLB advances	371,175	325,210
Other borrowings	327,150	209,050
Junior subordinated debentures	42,624	48,879
Significant Other Observable Inputs (Level 2) | Commitments to extend credit
Off-balance sheet assets (liabilities):
Financial instruments with off-balance sheet risk	0	0
Significant Other Observable Inputs (Level 2) | Standby letters of credit
Off-balance sheet assets (liabilities):
Financial instruments with off-balance sheet risk	0	0
Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	0	0
Certificates of deposit held in other banks	0	0
Loans held for sale, at cost	0	0
Loans, net	13,093,698	11,689,672
FHLB of Dallas stock and other restricted stock	0	0
Accrued interest receivable	0	0
Financial liabilities:
Deposits	0	0
Accrued interest payable	0	0
FHLB advances	0	0
Other borrowings	0	0
Junior subordinated debentures	0	0
Significant Unobservable Inputs (Level 3) | Commitments to extend credit
Off-balance sheet assets (liabilities):
Financial instruments with off-balance sheet risk	0	0
Significant Unobservable Inputs (Level 3) | Standby letters of credit
Off-balance sheet assets (liabilities):
Financial instruments with off-balance sheet risk	0	0
Carrying Amount
Financial assets:
Cash and cash equivalents	1,813,987	565,170
Certificates of deposit held in other banks	4,482	5,719
Loans held for sale, at cost	10,878	6,441
Loans, net	12,978,238	11,562,814
FHLB of Dallas stock and other restricted stock	20,305	30,052
Accrued interest receivable	60,581	35,860
Financial liabilities:
Deposits	14,398,927	11,941,336
Accrued interest payable	7,397	9,583
FHLB advances	375,000	325,000
Other borrowings	312,175	202,251
Junior subordinated debentures	54,023	53,824
Carrying Amount | Commitments to extend credit
Off-balance sheet assets (liabilities):
Financial instruments with off-balance sheet risk	0	0
Carrying Amount | Standby letters of credit
Off-balance sheet assets (liabilities):
Financial instruments with off-balance sheet risk	0	0
Estimated Fair Value
Financial assets:
Cash and cash equivalents	1,813,987	565,170
Certificates of deposit held in other banks	4,595	5,951
Loans held for sale, at cost	11,138	6,554
Loans, net	13,093,698	11,689,672
FHLB of Dallas stock and other restricted stock	20,305	30,052
Accrued interest receivable	60,581	35,860
Financial liabilities:
Deposits	14,407,596	11,958,939
Accrued interest payable	7,397	9,583
FHLB advances	371,175	325,210
Other borrowings	327,150	209,050
Junior subordinated debentures	42,624	48,879
Estimated Fair Value | Commitments to extend credit
Off-balance sheet assets (liabilities):
Financial instruments with off-balance sheet risk	0	0
Estimated Fair Value | Standby letters of credit
Off-balance sheet assets (liabilities):
Financial instruments with off-balance sheet risk	$ 0	$ 0

Derivative Financial Instrume_3

Derivative Financial Instruments - Notional Balances and Fair Values of Outstanding Positions (Details) - Not designated as hedging - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Interest rate lock commitments
Derivative [Line Items]
Outstanding Notional Balance	$ 116,795	$ 28,434
Asset Derivative Fair Value	3,515	847
Liability Derivative Fair Value	0	0
Forward mortgage-backed securities trades
Derivative [Line Items]
Outstanding Notional Balance	104,000	42,500
Asset Derivative Fair Value	0	6
Liability Derivative Fair Value	568	69
Commercial loan interest rate swaps | Commercial Loan | Loan customer counterparty
Derivative [Line Items]
Outstanding Notional Balance	335,370	280,751
Asset Derivative Fair Value	20,159	6,104
Liability Derivative Fair Value	0	0
Commercial loan interest rate swaps | Commercial Loan | Financial institution counterparty
Derivative [Line Items]
Outstanding Notional Balance	335,370	280,751
Asset Derivative Fair Value	0	0
Liability Derivative Fair Value	$ 21,306	$ 6,566

Derivative Financial Instrume_4

Derivative Financial Instruments Derivative Financial Instruments - Schedule of Weighted Average Interest Rate Received and Paid (Details) - Not designated as hedging - Commercial Loan - Loan customer counterparty - Interest rate swap	Dec. 31, 2020	Dec. 31, 2019
Interest Rate Received
Derivative [Line Items]
Derivative Weighted Average Fixed Interest Rate (Received)	4.08%	4.23%
Interest Rate Paid
Derivative [Line Items]
Derivative Weighted Average Variable Interest Rate (Paid)	2.32%	3.77%

Derivative Financial Instrume_5

Derivative Financial Instruments - Narrative (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Cash collateral pledged for derivatives	$ 23,829,000	$ 4,350,000
Securities collateral pledged for derivatives	$ 6,494,000
Risk Participation Agreements Participant Bank
Derivative [Line Items]
Number of risk participation agreements	1
Credit risk participation	$ 5,597,000
Risk Participation Agreements Lead Bank
Derivative [Line Items]
Number of risk participation agreements	1
Credit risk participation	$ 9,604,000
Loan customer counterparty | Interest rate swap
Derivative [Line Items]
Credit exposure	$ 20,159,000

Derivative Financial Instrume_6

Derivative Financial Instruments - Income (Loss) on Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Interest rate lock commitments
Derivative [Line Items]
Derivatives not designated as hedging instruments	$ 2,668	$ 25
Forward mortgage-backed securities trades
Derivative [Line Items]
Derivatives not designated as hedging instruments	$ (505)	$ 163

Stock Awards - Additional Infor

Stock Awards - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 8,450,000	$ 7,808,000	$ 6,062,000
Estimated future compensation expense	$ 15,823,000
Period for recognition	2 years 6 months 25 days
Fair value of common stock awards vested	$ 5,602,000	8,725,000	8,206,000
Stock based compensation expense	8,450,000	7,808,000	6,062,000
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Excess tax expense (benefit) on vested restricted stock	$ 243,000	$ 21,000	$ (646,000)
Performance stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period for recognition	3 years 6 months
Unrecognized compensation expense	$ 5,129,000
Stock based compensation expense	$ 0
2013 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (shares)				2,300,000
Remaining available for grant for future awards (shares)	1,150,617
2013 Equity Incentive Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock vesting period	1 year
2013 Equity Incentive Plan | Minimum | Performance stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock vesting period	3 years
Stock based compensation, award vesting percentage	0.00%
2013 Equity Incentive Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock vesting period	5 years
2013 Equity Incentive Plan | Maximum | Performance stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock vesting period	4 years
Stock based compensation, award vesting percentage	150.00%

Stock Awards - Schedule of Nonv

Stock Awards - Schedule of Nonvested Shares Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Restricted stock
Number of Shares
Nonvested shares, beginning balance (shares)	284,861	252,903
Acquired awards replaced during the period (shares)		70,248
Granted during the period (shares)	310,290	138,608
Vested during the period (shares)	(115,436)	(161,032)
Forfeited during the period (shares)	(10,915)	(15,866)
Nonvested shares, ending balance (shares)	468,800	284,861
Weighted Average Grant Date Fair Value
Nonvested shares, beginning balance (usd per share)	$ 58.63	$ 62.81
Acquired awards replaced during the period (usd per share)		45.77
Granted during the period (usd per share)	43.54	51.14
Vested during the period (usd per share)	58.08	54.76
Forfeited during the period (use per share)	48.37	46.95
Nonvested shares, ending balance (usd per share)	$ 49.01	$ 58.63
Performance stock units
Number of Shares
Nonvested shares, beginning balance (shares)	0
Granted during the period (shares)	89,300
Vested during the period (shares)	0
Forfeited during the period (shares)	0
Nonvested shares, ending balance (shares)	89,300	0
Weighted Average Grant Date Fair Value
Nonvested shares, beginning balance (usd per share)	$ 0
Granted during the period (usd per share)	38.29
Vested during the period (usd per share)	0
Forfeited during the period (use per share)	0
Nonvested shares, ending balance (usd per share)	$ 38.29	$ 0

Stock Awards - Future Vesting S

Stock Awards - Future Vesting Schedule of Nonvested Shares (Detail)	Dec. 31, 2020shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares	468,800
First year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares	177,431
Second year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares	139,009
Third year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares	99,604
Fourth year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares	52,356
Fifth year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares	400

Compensation Related Costs, Sha

Compensation Related Costs, Share Based Payments (Details) - Performance stock units	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Number of Shares
Nonvested shares, beginning balance (shares) | shares	0
Granted during the period (shares) | shares	89,300
Vested during the period (shares) | shares	0
Forfeited during the period (shares) | shares	0
Nonvested shares, ending balance (shares) | shares	89,300
Weighted Average Grant Date Fair Value
Nonvested shares, beginning balance (usd per share) | $ / shares	$ 0
Granted during the period (usd per share) | $ / shares	38.29
Vested during the period (usd per share) | $ / shares	0
Forfeited during the period (use per share) | $ / shares	0
Nonvested shares, ending balance (usd per share) | $ / shares	$ 38.29

Regulatory Matters - Actual Cap

Regulatory Matters - Actual Capital Amounts and Ratios (Details) $ in Thousands	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Consolidated
Total capital to risk weighted assets:
Actual Amount	$ 1,825,661	$ 1,513,209
Actual Ratio (percent)	0.1332	0.1183
Minimum Required for Capital Adequacy Purposes Amount	$ 1,438,939	$ 1,343,114
Minimum Required for Capital Adequacy Purposes Ratio (percent)	0.1050	0.1050
Tier 1 capital to risk weighted assets:
Tier One Risk Based Capital	$ 1,471,841	$ 1,303,748
Actual Ratio (percent)	0.1074	0.1019
Minimum Required for Capital Adequacy Purposes Amount	$ 1,164,855	$ 1,087,282
Minimum Required for Capital Adequacy Purposes Ratio (percent)	0.0850	0.0850
Common equity tier 1 to risk weighted assets:
Actual amount	$ 1,416,241	$ 1,248,148
Actual ratio (percent)	0.1033	0.0976
Minimum Required for Capital Adequacy Purposes Amount	$ 959,293	$ 895,409
Minimum Required for Capital Adequacy Purposes Ratio (percent)	0.0700	0.0700
Tier 1 capital to average assets:
Actual Amount	$ 1,471,841	$ 1,303,748
Actual Ratio (percent)	0.0912	0.0932
Minimum Required for Capital Adequacy Purposes Amount	$ 645,730	$ 559,758
Minimum Required for Capital Adequacy Purposes Ratio (percent)	0.0400	0.0400
Bank
Total capital to risk weighted assets:
Actual Amount	$ 1,864,240	$ 1,548,103
Actual Ratio (percent)	0.1361	0.1211
Minimum Required for Capital Adequacy Purposes Amount	$ 1,438,385	$ 1,342,595
Minimum Required for Capital Adequacy Purposes Ratio (percent)	0.1050	0.1050
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 1,369,891	$ 1,278,662
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (percent)	0.1000	0.1000
Tier 1 capital to risk weighted assets:
Tier One Risk Based Capital	$ 1,776,420	$ 1,496,642
Actual Ratio (percent)	0.1297	0.1170
Minimum Required for Capital Adequacy Purposes Amount	$ 1,164,407	$ 1,086,863
Minimum Required for Capital Adequacy Purposes Ratio (percent)	0.0850	0.0850
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 1,095,913	$ 1,022,930
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (percent)	0.0800	0.0800
Common equity tier 1 to risk weighted assets:
Actual amount	$ 1,776,420	$ 1,496,642
Actual ratio (percent)	0.1297	0.1170
Minimum Required for Capital Adequacy Purposes Amount	$ 958,924	$ 895,064
Minimum Required for Capital Adequacy Purposes Ratio (percent)	0.0700	0.0700
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 890,429	$ 831,130
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (percent)	0.0650	0.0650
Tier 1 capital to average assets:
Actual Amount	$ 1,776,420	$ 1,496,642
Actual Ratio (percent)	0.1101	0.1070
Minimum Required for Capital Adequacy Purposes Amount	$ 645,539	$ 559,584
Minimum Required for Capital Adequacy Purposes Ratio (percent)	0.0400	0.0400
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 806,924	$ 699,480
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (percent)	0.0500	0.0500

Regulatory Matters - Additional

Regulatory Matters - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Oct. 22, 2020
Regulatory Assets [Line Items]
Common stock repurchased	$ 5,819,000	$ 51,659,000
October 2018 Share Repurchase Program
Regulatory Assets [Line Items]
Common stock repurchased (shares)		897,738
Common stock purchased to settle employee tax withholding related to vesting of stock awards		$ 2,611,000
Common stock repurchased		$ 49,048,000
Common stock purchased to settle employee tax withholding related to vesting of stock awards (shares)		55,106
October 2020 Share Repurchase Program
Regulatory Assets [Line Items]
Stock repurchase authorized amount			$ 150,000,000
Common stock repurchased (shares)	109,548
Common stock purchased to settle employee tax withholding related to vesting of stock awards	$ 159,000
Common stock repurchased	$ 5,660,000
Common stock purchased to settle employee tax withholding related to vesting of stock awards (shares)	2,951

Business Combinations - Additio

Business Combinations - Additional Information (Detail) $ in Thousands	Jan. 01, 2019USD ($)branchshares	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Business Acquisition [Line Items]
Acquisition related expenses		$ 16,225	$ 33,445	$ 6,157
Goodwill acquired		994,021	994,021
Offering costs paid in connection with acquired banks		0	804	209
Texas Capital Bancshares, Inc.
Business Acquisition [Line Items]
Acquisition related expenses		$ 15,605	5,022
Guaranty Bancorp
Business Acquisition [Line Items]
Acquisition related expenses			33,622	$ 1,560
Percentage of outstanding stock acquired (percent)	100.00%
Number of branches acquired | branch	32
Stock issued for acquisition of bank (in shares) | shares	13,179,748
Goodwill acquired			272,224
Offering costs paid in connection with acquired banks			804
Estimated fair value of non-credit impaired loans	$ 2,478,144
Contractual balance of non-credit impaired loans	2,573,355
Interest income adjustment for non-credit impaired loans	$ 95,211
Guaranty Bancorp | Salaries and employee benefits
Business Acquisition [Line Items]
Acquisition related expenses			5,328
Guaranty Bancorp | Acquisition expense
Business Acquisition [Line Items]
Acquisition related expenses			$ 28,294

Business Combinations - Estimat

Business Combinations - Estimated Fair Values Of Assets Acquired And Liabilities Assumed (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jan. 01, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Assets of acquired bank:
Goodwill		$ 994,021	$ 994,021
Liabilities of acquired bank:
Common and restricted stock issued at $45.77 per share		0	601,872	$ 157,263
Cash paid to shareholders of acquired banks		$ 0	9	$ 31,016
Guaranty Bancorp
Assets of acquired bank:
Cash and cash equivalents			39,913
Certificates of deposit held in other banks			262
Securities available for sale			561,052
Restricted stock			27,794
Loans			2,789,868
Premises and equipment			65,786
Other real estate owned			1,829
Goodwill			272,224
Other intangible assets			71,518
Bank owned life insurance			80,837
Other assets			31,987
Total assets acquired			3,943,070
Liabilities of acquired bank:
Deposits			3,108,810
Repurchase agreements			8,475
FHLB advances			142,653
Other borrowings			40,000
Junior subordinated debentures			25,774
Other liabilities			15,477
Total liabilities assumed			3,341,189
Common and restricted stock issued at $45.77 per share			600,022
Cash paid to shareholders of acquired banks			9
Stock issued for acquisition of bank (in shares)	13,179,748
Share price (in USD per share)	$ 45.77
Common Stock | Guaranty Bancorp
Liabilities of acquired bank:
Stock issued for acquisition of bank (in shares)	13,109,500
Restricted Stock Replacement Awards | Guaranty Bancorp
Liabilities of acquired bank:
Common and restricted stock issued at $45.77 per share			$ 1,850
Stock issued for acquisition of bank (in shares)	70,248

Parent Company Only Financial_3

Parent Company Only Financial Statements - Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 1,813,987	$ 565,170
Other assets	143,730	108,392
Total assets	17,753,476	14,958,207
Liabilities and Stockholders’ Equity
Other borrowings	312,175	202,251
Junior subordinated debentures	54,023	53,824
Other liabilities	97,980	96,023
Total liabilities	15,238,105	12,618,434
Stockholders’ equity:
Preferred stock	0	0
Common stock	431	430
Additional paid-in capital	1,934,807	1,926,359
Retained earnings	543,800	393,674
Accumulated other comprehensive income	36,333	19,310
Total stockholders’ equity	2,515,371	2,339,773	$ 1,606,433	$ 1,336,018
Total liabilities and stockholders’ equity	17,753,476	14,958,207
Parent
Assets
Cash and cash equivalents	5,482	8,277	$ 8,355	$ 9,400
Investment in subsidiaries	2,876,171	2,588,857
Investment in trusts	1,724	1,724
Other assets	3,849	3,355
Total assets	2,887,226	2,602,213
Liabilities and Stockholders’ Equity
Other borrowings	312,175	202,251
Junior subordinated debentures	54,023	53,824
Other liabilities	5,657	6,365
Total liabilities	371,855	262,440
Stockholders’ equity:
Preferred stock	0	0
Common stock	431	430
Additional paid-in capital	1,934,807	1,926,359
Retained earnings	543,800	393,674
Accumulated other comprehensive income	36,333	19,310
Total stockholders’ equity	2,515,371	2,339,773
Total liabilities and stockholders’ equity	$ 2,887,226	$ 2,602,213

Parent Company Only Financial_4

Parent Company Only Financial Statements - Statement of Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest expense:
Interest on other borrowings	$ 12,462	$ 11,590	$ 8,398
Interest on junior subordinated debentures	2,162	3,028	1,609
Total interest expense	95,060	148,175	81,038
Noninterest income:
Other	25,304	25,503	16,692
Total noninterest income	85,063	78,176	42,224
Noninterest expense:
Salaries and employee benefits	157,540	162,683	111,697
Professional fees	12,630	7,936	4,556
Acquisition expense, including legal	16,225	33,445	6,157
Other	34,146	39,207	25,961
Total noninterest expense	306,134	321,864	198,619
Income tax benefit	(51,173)	(53,528)	(31,738)
Net income	201,209	192,736	128,259
Parent
Interest expense:
Interest on other borrowings	12,446	11,561	8,390
Interest on junior subordinated debentures	2,162	3,028	1,609
Total interest expense	14,608	14,589	9,999
Noninterest income:
Dividends from subsidiaries	83,314	105,877	39,841
Other	0	1	14
Total noninterest income	83,314	105,878	39,855
Noninterest expense:
Salaries and employee benefits	8,346	7,653	6,318
Professional fees	202	264	332
Acquisition expense, including legal	16,225	33,445	6,157
Other	2,424	2,562	1,611
Total noninterest expense	27,197	43,924	14,418
Income before income tax benefit and equity in undistributed income of subsidiaries	41,509	47,365	15,438
Income tax benefit	9,410	11,066	5,541
Income before equity in undistributed income of subsidiaries	50,919	58,431	20,979
Equity in undistributed income of subsidiaries	150,290	134,305	107,280
Net income	$ 201,209	$ 192,736	$ 128,259

Parent Company Only Financial_5

Parent Company Only Financial Statements - Statement of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 201,209	$ 192,736	$ 128,259
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of discount and origination costs on borrowings	720	633	633
Stock based compensation expense	8,450	7,808	6,062
Excess tax expense (benefit) on restricted stock vested	243	21	(646)
Deferred tax (benefit) expense	(1,633)	14,102	1,937
Net change in other assets	(35,025)	(5,878)	(14,352)
Net change in other liabilities	(7,833)	(15,636)	20,277
Net cash provided by operating activities	154,295	173,319	158,741
Cash flows from investing activities:
Cash acquired in connection with acquisition	0	39,913	44,723
Cash paid in connection with acquisition	0	(9)	(31,016)
Net cash used in investing activities	(1,471,388)	(673,988)	(656,707)
Cash flows from financing activities:
Proceeds from other borrowings	156,489	65,000	0
Repayments of other borrowings	(47,086)	(40,500)	0
Proceeds from exercise of common stock warrants	0	0	2,533
Offering costs paid in connection with acquired bank	0	(804)	(209)
Repurchase of common stock	(5,819)	(51,659)	0
Dividends paid	(45,265)	(43,302)	(15,908)
Net cash provided by (used in) financing activities	2,565,910	935,060	197,643
Cash and cash equivalents at beginning of year	565,170
Cash and cash equivalents at end of year	1,813,987	565,170
Parent
Cash flows from operating activities:
Net income	201,209	192,736	128,259
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed net income of subsidiaries	(150,290)	(134,305)	(107,280)
Amortization of discount and origination costs on borrowings	720	633	633
Stock based compensation expense	8,450	7,808	6,062
Excess tax expense (benefit) on restricted stock vested	243	21	(646)
Deferred tax (benefit) expense	96	2,165	1,054
Net change in other assets	(590)	1,863	6,918
Net change in other liabilities	(952)	(64)	1,130
Net cash provided by operating activities	58,886	70,857	36,130
Cash flows from investing activities:
Capital investment in subsidiaries	(120,000)	0	0
Cash acquired in connection with acquisition	0	339	7,425
Cash paid in connection with acquisition	0	(9)	(31,016)
Net cash used in investing activities	(120,000)	330	(23,591)
Cash flows from financing activities:
Proceeds from other borrowings	148,653	65,000	0
Repayments of other borrowings	(39,250)	(40,500)	0
Proceeds from exercise of common stock warrants	0	0	2,533
Offering costs paid in connection with acquired bank	0	(804)	(209)
Repurchase of common stock	(5,819)	(51,659)	0
Dividends paid	(45,265)	(43,302)	(15,908)
Net cash provided by (used in) financing activities	58,319	(71,265)	(13,584)
Net change in cash and cash equivalents	(2,795)	(78)	(1,045)
Cash and cash equivalents at beginning of year	8,277	8,355	9,400
Cash and cash equivalents at end of year	$ 5,482	$ 8,277	$ 8,355

Subsequent Events - Narrative (

Subsequent Events - Narrative (Details) - Subsequent event - USD ($)	Mar. 01, 2021	Feb. 25, 2021	Jan. 28, 2021	Jan. 17, 2021
Subsequent Event [Line Items]
Dividends declared (in usd per share)			$ 0.30
Dividends paid		$ 12,954,000
Revolving line of credit | Line of Credit
Subsequent Event [Line Items]
Line of credit, maximum capacity				$ 100,000,000
Borrowings against line of credit	$ 0