Southside Bancshares (SBSI) 10-Q 29 Oct 21 2021 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2021	Oct. 26, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	000-12247
Entity Registrant Name	SOUTHSIDE BANCSHARES, INC.
Entity Incorporation, State or Country Code	TX
Entity Tax Identification Number	75-1848732
Entity Address, Address Line One	1201 S. Beckham Avenue,
Entity Address, City or Town	Tyler,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75701
City Area Code	903
Local Phone Number	531-7111
Title of 12(b) Security	Common Stock, $1.25 par value
Trading Symbol	SBSI
Security Exchange Name	NASDAQ
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
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		32,276,057
Entity Central Index Key	0000705432
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS (UN

CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($)		Sep. 30, 2021	Dec. 31, 2020
ASSETS
Cash and due from banks		$ 83,346,000	$ 87,357,000
Interest earning deposits		3,787,000	21,051,000
Total cash and cash equivalents		87,133,000	108,408,000
Securities AFS, at estimated fair value (amortized cost of $2,650,237 and $2,437,513, respectively)		2,753,104,000	2,587,305,000
Securities HTM (estimated fair value of $98,035 and $118,198, respectively)		92,479,000	108,998,000
FHLB stock, at cost		27,248,000	25,259,000
Equity investments		11,794,000	11,905,000
Loans held for sale		1,131,000	3,695,000
Loans:
Loans		3,647,585,000	3,657,779,000
Less: Allowance for loan losses		(38,022,000)	(49,006,000)
Net loans		3,609,563,000	3,608,773,000
Premises and equipment, net		142,736,000	144,576,000
Operating lease ROU assets		15,394,000	15,063,000
Goodwill		201,116,000	201,116,000
Other intangible assets, net		7,553,000	9,744,000
Interest receivable		29,097,000	38,708,000
BOLI		130,522,000	115,583,000
Other assets		26,821,000	29,094,000
Total assets		7,135,691,000	7,008,227,000
Deposits:
Noninterest bearing		1,596,781,000	1,354,815,000
Interest bearing		3,734,874,000	3,577,507,000
Total deposits		5,331,655,000	4,932,322,000
Other borrowings		20,724,000	23,172,000
FHLB borrowings		659,204,000	832,527,000
Subordinated notes, net of unamortized debt issuance costs	[1]	98,500,000	197,251,000
Trust preferred subordinated debentures, net of unamortized debt issuance costs		60,259,000	60,255,000
Deferred tax liability, net		12,486,000	15,549,000
Unsettled trades to purchase securities		4,433,000	0
Operating lease liabilities		16,967,000	16,734,000
Other liabilities		53,597,000	55,120,000
Total liabilities		6,257,825,000	6,132,930,000
Off-balance-sheet arrangements, commitments and contingencies (Note 12)
Shareholders’ equity:
Common stock:  ($1.25 par value, 80,000,000 shares authorized, 37,960,148 shares issued at September 30, 2021 and 37,934,819 shares issued at December 31, 2020)		47,450,000	47,419,000
Paid-in capital		778,600,000	771,511,000
Retained earnings		163,809,000	111,208,000
Treasury stock: (shares at cost, 5,687,226 at September 30, 2021 and 4,983,645 at December 31, 2020)		(155,967,000)	(123,921,000)
AOCI		43,974,000	69,080,000
Total shareholders’ equity		877,866,000	875,297,000
Total liabilities and shareholders’ equity		$ 7,135,691,000	$ 7,008,227,000
[1]	This debt consists of subordinated notes with a remaining maturity greater than one year that qualify under the risk-based capital guidelines as Tier 2 capital, subject to certain limitations.

CONSOLIDATED BALANCE SHEETS (_2

CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Available-for-sale [Abstract]
Securities available for sale, amortized cost	$ 2,650,237	$ 2,437,513
Held-to-maturity Securities, Other Disclosure Items [Abstract]
Securities held to maturity, fair value	$ 98,035	$ 118,198
Shareholders' equity:
Common stock, par value (in dollars per share)	$ 1.25	$ 1.25
Common stock, shares authorized (in shares)	80,000,000	80,000,000
Common stock, shares issued (in shares)	37,960,148	37,934,819
Treasury stock (in shares)	5,687,226	4,983,645

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Interest income:
Loans	$ 37,034	$ 38,185	$ 108,792	$ 119,195
Taxable investment securities	3,853	1,175	9,097	2,419
Tax-exempt investment securities	9,649	9,003	27,787	24,430
MBS	4,405	7,048	15,140	27,626
FHLB stock and equity investments	111	249	355	1,034
Other interest earning assets	24	17	56	220
Total interest income	55,076	55,677	161,227	174,924
Interest expense:
Deposits	2,234	4,862	7,170	21,010
FHLB borrowings	1,865	2,369	5,590	9,272
Subordinated notes	2,417	1,427	7,235	4,250
Trust preferred subordinated debentures	345	378	1,045	1,469
Other borrowings	9	55	31	365
Total interest expense	6,870	9,091	21,071	36,366
Net interest income	48,206	46,586	140,156	138,558
Provision for credit losses	(5,071)	(4,746)	(13,543)	25,746
Net interest income after provision for credit losses	53,277	51,332	153,699	112,812
Noninterest income:
Deposit services	6,779	6,129	19,513	17,940
Net gain on sale of securities AFS	1,381	78	3,399	8,281
Gain on sale of loans	299	1,071	1,285	1,924
Trust fees	1,494	1,253	4,373	3,779
BOLI	637	680	1,908	1,899
Brokerage services	846	564	2,476	1,643
Other	1,333	1,366	4,371	3,366
Total noninterest income	12,769	11,141	37,325	38,832
Noninterest expense:
Salaries and employee benefits	19,777	19,344	59,825	57,616
Net occupancy	3,532	3,595	10,698	10,574
Advertising, travel & entertainment	579	519	1,491	1,643
ATM expense	311	271	821	728
Professional fees	1,135	961	3,166	3,238
Software and data processing	1,503	1,215	4,221	3,737
Communications	552	495	1,689	1,494
FDIC insurance	454	469	1,343	668
Amortization of intangibles	695	881	2,191	2,792
Loss on redemption of subordinated notes	1,118	0	1,118	0
Other	2,107	3,866	7,133	9,502
Total noninterest expense	31,763	31,616	93,696	91,992
Income before income tax expense	34,283	30,857	97,328	59,652
Income tax expense	4,977	3,783	12,614	7,071
Net income	$ 29,306	$ 27,074	$ 84,714	$ 52,581
Earnings per common share - basic (in dollars per share)	$ 0.90	$ 0.82	$ 2.60	$ 1.58
Earnings per common share - diluted (in dollars per share)	0.90	0.82	2.59	1.58
Cash dividends paid per common share (in dollars per share)	$ 0.33	$ 0.31	$ 0.98	$ 0.93

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 29,306	$ 27,074	$ 84,714	$ 52,581
Securities AFS and transferred securities:
Change in unrealized holding (loss) gain on AFS securities during the period	(27,714)	1,601	(43,527)	88,900
Reclassification adjustment for amortization related to AFS and HTM debt securities	312	394	1,118	730
Reclassification adjustment for net gain on sale of AFS securities, included in net income	(1,381)	(78)	(3,399)	(8,281)
Derivatives:
Change in net unrealized gain (loss) on effective cash flow hedge interest rate swap derivatives	377	(197)	8,296	(25,236)
Reclassification adjustment of net loss related to derivatives designated as cash flow hedges	1,617	1,587	4,784	2,283
Pension plans:
Amortization of net actuarial loss and prior service credit, included in net periodic benefit cost	316	819	948	2,207
Prior service cost adjustment due to plan amendment	0	0	0	163
Change in net actuarial loss	0	0	0	(7,558)
Other comprehensive income (loss), before tax	(26,473)	4,126	(31,780)	53,208
Income tax benefit (expense) related to items of other comprehensive income (loss)	5,560	(866)	6,674	(11,173)
Other comprehensive (loss) income, net of tax	(20,913)	3,260	(25,106)	42,035
Comprehensive income	$ 8,393	$ 30,334	$ 59,608	$ 94,616

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock	Paid In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Cumulative effect of accounting change	Cumulative effect of accounting changeRetained Earnings	Adjusted beginning balance	Adjusted beginning balanceCommon Stock	Adjusted beginning balancePaid In Capital	Adjusted beginning balanceRetained Earnings	Adjusted beginning balanceTreasury Stock	Adjusted beginning balanceAccumulated Other Comprehensive Income (Loss)
Beginning balance, net of tax at Dec. 31, 2019	$ 804,580	$ 47,360	$ 766,718	$ 80,274	$ (94,008)	$ 4,236	$ (7,830)	$ (7,830)	$ 796,750	$ 47,360	$ 766,718	$ 72,444	$ (94,008)	$ 4,236
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,953			3,953
Other comprehensive (loss) income	29,303					29,303
Issuance of common stock for dividend reinvestment plan	347	13	334
Purchase of common stock	(25,842)				(25,842)
Stock compensation expense	695		695
Net issuance of common stock under employee stock plans	1,088		693	(40)	435
Cash dividends paid on common stock	(10,494)			(10,494)
Ending balance, net of tax at Mar. 31, 2020	795,800	47,373	768,440	65,863	(119,415)	33,539
Beginning balance, net of tax at Dec. 31, 2019	804,580	47,360	766,718	80,274	(94,008)	4,236	$ (7,830)	$ (7,830)	$ 796,750	$ 47,360	$ 766,718	$ 72,444	$ (94,008)	$ 4,236
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	52,581
Other comprehensive (loss) income	42,035
Ending balance, net of tax at Sep. 30, 2020	839,148	47,402	770,639	93,916	(119,080)	46,271
Beginning balance, net of tax at Mar. 31, 2020	795,800	47,373	768,440	65,863	(119,415)	33,539
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	21,554			21,554
Other comprehensive (loss) income	9,472					9,472
Issuance of common stock for dividend reinvestment plan	336	14	322
Stock compensation expense	772		772
Net issuance of common stock under employee stock plans	(96)		(127)	(50)	81
Cash dividends paid on common stock	(10,233)			(10,233)
Ending balance, net of tax at Jun. 30, 2020	817,605	47,387	769,407	77,134	(119,334)	43,011
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	27,074			27,074
Other comprehensive (loss) income	3,260					3,260
Issuance of common stock for dividend reinvestment plan	337	15	322
Stock compensation expense	786		786
Net issuance of common stock under employee stock plans	331		124	(47)	254
Cash dividends paid on common stock	(10,245)			(10,245)
Ending balance, net of tax at Sep. 30, 2020	839,148	47,402	770,639	93,916	(119,080)	46,271
Beginning balance, net of tax at Dec. 31, 2020	875,297	47,419	771,511	111,208	(123,921)	69,080
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	34,091			34,091
Other comprehensive (loss) income	(29,494)					(29,494)
Issuance of common stock for dividend reinvestment plan	332	11	321
Purchase of common stock	(15,213)				(15,213)
Stock compensation expense	674		674
Net issuance of common stock under employee stock plans	3,386		2,309	(41)	1,118
Cash dividends paid on common stock	(10,476)			(10,476)
Ending balance, net of tax at Mar. 31, 2021	858,597	47,430	774,815	134,782	(138,016)	39,586
Beginning balance, net of tax at Dec. 31, 2020	875,297	47,419	771,511	111,208	(123,921)	69,080
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	84,714
Other comprehensive (loss) income	(25,106)
Ending balance, net of tax at Sep. 30, 2021	877,866	47,450	778,600	163,809	(155,967)	43,974
Beginning balance, net of tax at Mar. 31, 2021	858,597	47,430	774,815	134,782	(138,016)	39,586
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	21,317			21,317
Other comprehensive (loss) income	25,301					25,301
Issuance of common stock for dividend reinvestment plan	330	9	321
Purchase of common stock	(3,497)				(3,497)
Stock compensation expense	686		686
Net issuance of common stock under employee stock plans	2,441		1,591	(47)	897
Cash dividends paid on common stock	(10,775)			(10,775)
Ending balance, net of tax at Jun. 30, 2021	894,400	47,439	777,413	145,277	(140,616)	64,887
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,306			29,306
Other comprehensive (loss) income	(20,913)					(20,913)
Issuance of common stock for dividend reinvestment plan	324	11	313
Purchase of common stock	(15,438)				(15,438)
Stock compensation expense	829		829
Net issuance of common stock under employee stock plans	64		45	(68)	87
Cash dividends paid on common stock	(10,706)			(10,706)
Ending balance, net of tax at Sep. 30, 2021	$ 877,866	$ 47,450	$ 778,600	$ 163,809	$ (155,967)	$ 43,974

CONSOLIDATED STATEMENTS OF CH_2

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) (Parenthetical) - $ / shares	3 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020
Statement of Stockholders' Equity [Abstract]
Issuance of common stock for dividend reinvestment plan (in shares)	8,631	7,780	8,918	12,201	11,532	10,607
Common stock purchased (in shares)	420,204	90,884	427,396			869,723
Net issuance of common stock under employee stock plans (in shares)	9,426	99,217	126,260	27,477	9,342	47,428
Cash dividends paid on common stock (in dollars per share)	$ 0.33	$ 0.33	$ 0.32	$ 0.31	$ 0.31	$ 0.31

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($)	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
OPERATING ACTIVITIES:
Net income	$ 84,714,000	$ 52,581,000
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and net amortization	8,634,000	9,128,000
Securities premium amortization (discount accretion), net	17,709,000	17,954,000
Loan (discount accretion) premium amortization, net	(649,000)	(847,000)
Provision for credit losses	(13,543,000)	25,746,000
Stock compensation expense	2,189,000	2,253,000
Deferred tax expense (benefit)	3,612,000	(4,305,000)
Net gain on sale of AFS securities	(3,399,000)	(8,281,000)
Net loss on premises and equipment	315,000	821,000
Gross proceeds from sales of loans held for sale	36,961,000	48,343,000
Gross originations of loans held for sale	(34,397,000)	(56,646,000)
Net (gain) loss on OREO	(180,000)	129,000
Loss due to curtailment	0	163,000
Loss on redemption of subordinated notes	1,118,000	0
Net change in:
Interest receivable	9,611,000	(1,987,000)
Other assets	(2,803,000)	(35,530,000)
Interest payable	(1,223,000)	(3,673,000)
Other liabilities	19,981,000	4,402,000
Net cash provided by operating activities	128,650,000	50,251,000
Securities AFS:
Purchases	(569,807,000)	(821,232,000)
Sales	104,728,000	291,581,000
Maturities, calls and principal repayments	243,507,000	316,072,000
Securities HTM:
Maturities, calls and principal repayments	16,602,000	19,820,000
Proceeds from redemption of FHLB stock and equity investments	19,240,000	20,000,000
Purchases of FHLB stock and equity investments	(21,113,000)	(5,483,000)
Net loan originations	9,314,000	(222,342,000)
Purchases of premises and equipment	(6,491,000)	(10,216,000)
Purchases of BOLI	(13,000,000)	(12,500,000)
Proceeds from sales of premises and equipment	1,853,000	114,000
Net proceeds from sales of OREO	797,000	277,000
Proceeds from sales of repossessed assets	247,000	158,000
Net cash used in investing activities	(214,123,000)	(423,751,000)
FINANCING ACTIVITIES:
Net change in deposits	399,303,000	420,068,000
Net change in other borrowings	(2,448,000)	13,210,000
Proceeds from FHLB borrowings	11,648,180,000	10,135,401,000
Repayment of FHLB borrowings	(11,821,503,000)	(10,155,201,000)
Net proceeds from issuance of subordinated notes	(95,000)	0
Redemption of subordinated notes	(100,011,000)	0
Proceeds from stock option exercises	6,108,000	1,502,000
Cash paid to tax authority related to tax withholding on share-based awards	(217,000)	(179,000)
Purchase of common stock	(34,148,000)	(25,842,000)
Proceeds from the issuance of common stock for dividend reinvestment plan	986,000	1,020,000
Cash dividends paid	(31,957,000)	(30,972,000)
Net cash provided by financing activities	64,198,000	359,007,000
Net (decrease) increase in cash and cash equivalents	(21,275,000)	(14,493,000)
Cash and cash equivalents at beginning of period	108,408,000	110,697,000
Cash and cash equivalents at end of period	87,133,000	96,204,000
SUPPLEMENTAL DISCLOSURES FOR CASH FLOW INFORMATION:
Interest paid	22,295,000	40,039,000
Income taxes paid	8,750,000	9,000,000
SUPPLEMENTAL DISCLOSURES OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Loans transferred to other repossessed assets and real estate through foreclosure	740,000	627,000
Unsettled trades to purchase securities	$ (4,433,000)	$ (7,294,000)

Summary of Significant Accounti

Summary of Significant Accounting and Reporting Policies	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Significant Accounting and Reporting Policies	Summary of Significant Accounting and Reporting Policies Basis of Presentation In this report, the words “the Company,” “we,” “us,” and “our” refer to the combined entities of Southside Bancshares, Inc. and its subsidiaries, including Southside Bank. The words “Southside” and “Southside Bancshares” refer to Southside Bancshares, Inc. The words “Southside Bank” and “the Bank” refer to Southside Bank. The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. GAAP for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, not all information required by GAAP for complete financial statements is included in these interim statements. In the opinion of management, all adjustments necessary for a fair presentation of such financial statements have been included. Such adjustments consisted only of normal recurring items. The preparation of these consolidated financial statements in accordance with GAAP requires the use of management’s estimates. These estimates are subjective in nature and involve matters of judgment. Actual amounts could differ from these estimates. Interim results are not necessarily indicative of results for a full year. These financial statements should be read in conjunction with the financial statements and notes thereto in our Annual Report on Form 10-K for the year ended December 31, 2020. Accounting Changes and Reclassifications Certain prior period amounts may be reclassified to conform to current year presentation. Accounting Pronouncements In March 2020, the FASB issued ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting.” ASU 2020-04 is intended to provide relief for companies preparing for discontinuation of interest rates based on LIBOR. The ASU provides optional expedients and exceptions for applying GAAP to contract modifications and hedging relationships, subject to meeting certain criteria, that reference LIBOR or other reference rates expected to be discontinued. ASU 2020-04 also provides for a one-time sale and/or transfer to AFS or trading to be made for HTM debt securities that both reference an eligible reference rate and were classified as HTM before January 1, 2020. ASU 2020-04 was effective for all entities as of March 12, 2020 and through December 31, 2022. Companies can apply the ASU as of the beginning of the interim period that includes March 12, 2020 or any date thereafter. The guidance requires companies to apply the guidance prospectively to contract modifications and hedging relationships while the one-time election to sell and/or transfer debt securities classified as HTM may be made any time after March 12, 2020. We have established an officer level committee to guide our transition from LIBOR and have begun efforts to transition to alternative rates consistent with industry timelines. We have identified products that utilize LIBOR and are implementing enhanced fallback language to facilitate the transition to alternative reference rates. We are evaluating existing systems and have begun offering new rates on a limited basis. ASU 2020-04 is not expected to have a material impact on our consolidated financial statements.

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share Earnings per share on a basic and diluted basis are calculated as follows (in thousands, except per share amounts): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Basic and Diluted Earnings: Net income $ 29,306 $ 27,074 $ 84,714 $ 52,581 Basic weighted-average shares outstanding 32,465 33,047 32,641 33,250 Add: Stock awards 91 51 118 81 Diluted weighted-average shares outstanding 32,556 33,098 32,759 33,331 Basic earnings per share: Net income $ 0.90 $ 0.82 $ 2.60 $ 1.58 Diluted earnings per share: Net income $ 0.90 $ 0.82 $ 2.59 $ 1.58 For the three and nine months ended September 30, 2021, there were approximately 462,000 and 288,000 anti-dilutive shares, respectively. For the three and nine months ended September 30, 2020, there were approximately and 835,000 and 811,000 anti-dilutive shares, respectively.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2021
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) The changes in accumulated other comprehensive income (loss) by component are as follows (in thousands): Three Months Ended September 30, 2021 Pension Plans Unrealized Gains (Losses) on Securities Unrealized Gains (Losses) on Derivatives Net Prior Service (Cost) Credit Net Gain (Loss) Total Beginning balance, net of tax $ 102,628 $ (8,334) $ 149 $ (29,556) $ 64,887 Other comprehensive income (loss): Other comprehensive (loss) income before reclassifications (27,714) 377 — — (27,337) Reclassification adjustments included in net income (1,069) 1,617 — 316 864 Income tax benefit (expense) 6,045 (418) — (67) 5,560 Net current-period other comprehensive (loss) income, net of tax (22,738) 1,576 — 249 (20,913) Ending balance, net of tax $ 79,890 $ (6,758) $ 149 $ (29,307) $ 43,974 Nine Months Ended September 30, 2021 Pension Plans Unrealized Gains (Losses) on Securities Unrealized Gains (Losses) on Derivatives Net Prior Net Gain (Loss) Total Beginning balance, net of tax $ 116,078 $ (17,091) $ 149 $ (30,056) $ 69,080 Other comprehensive income (loss): Other comprehensive (loss) income before reclassifications (43,527) 8,296 — — (35,231) Reclassification adjustments included in net income (2,281) 4,784 — 948 3,451 Income tax benefit (expense) 9,620 (2,747) — (199) 6,674 Net current-period other comprehensive (loss) income, net of tax (36,188) 10,333 — 749 (25,106) Ending balance, net of tax $ 79,890 $ (6,758) $ 149 $ (29,307) $ 43,974 Three Months Ended September 30, 2020 Pension Plans Unrealized Gains (Losses) on Securities Unrealized Gains (Losses) on Derivatives Net Prior Service (Cost) Credit Net Gain (Loss) Total Beginning balance, net of tax $ 100,790 $ (20,904) $ (20) $ (36,855) $ 43,011 Other comprehensive income (loss): Other comprehensive income (loss) before reclassifications 1,601 (197) — — 1,404 Reclassification adjustments included in net income 316 1,587 (2) 821 2,722 Income tax expense (403) (292) — (171) (866) Net current-period other comprehensive income (loss), net of tax 1,514 1,098 (2) 650 3,260 Ending balance, net of tax $ 102,304 $ (19,806) $ (22) $ (36,205) $ 46,271 Nine Months Ended September 30, 2020 Pension Plans Unrealized Gains (Losses) on Securities Unrealized Gains (Losses) on Derivatives Net Prior Service (Cost) Credit Net Gain (Loss) Total Beginning balance, net of tax $ 38,038 $ (1,672) $ (145) $ (31,985) $ 4,236 Other comprehensive income (loss): Other comprehensive income (loss) before reclassifications 88,900 (25,236) 163 (7,558) 56,269 Reclassification adjustments included in net income (7,551) 2,283 (6) 2,213 (3,061) Income tax (expense) benefit (17,083) 4,819 (34) 1,125 (11,173) Net current-period other comprehensive income (loss), net of tax 64,266 (18,134) 123 (4,220) 42,035 Ending balance, net of tax $ 102,304 $ (19,806) $ (22) $ (36,205) $ 46,271 The reclassification adjustments out of accumulated other comprehensive income (loss) included in net income are presented below (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Unrealized gains and losses on securities transferred: Amortization of unrealized gains and losses (1) $ (312) $ (394) $ (1,118) $ (730) Tax benefit 66 82 235 153 Net of tax (246) (312) (883) (577) Unrealized gains and losses on available for sale securities: Realized net gain on sale of securities (2) 1,381 78 3,399 8,281 Tax expense (290) (16) (714) (1,739) Net of tax 1,091 62 2,685 6,542 Derivatives: Realized net loss on interest rate swap derivatives (3) (1,617) (1,593) (4,784) (2,303) Tax benefit 340 335 1,005 484 Net of tax (1,277) (1,258) (3,779) (1,819) Amortization of unrealized gains on terminated interest rate swap derivatives (3) — 6 — 20 Tax expense — (1) — (4) Net of tax — 5 — 16 Amortization of pension plan: Net actuarial loss (4) (316) (821) (948) (2,213) Prior service credit (4) — 2 — 6 Total before tax (316) (819) (948) (2,207) Tax benefit 67 172 199 463 Net of tax (249) (647) (749) (1,744) Total reclassifications for the period, net of tax $ (681) $ (2,150) $ (2,726) $ 2,418 (1) Included in interest income on the consolidated statements of income. (2) Listed as net gain on sale of securities AFS on the consolidated statements of income. (3) Included in interest expense for FHLB borrowings on the consolidated statements of income. (4) These AOCI components are included in the computation of net periodic pension cost (income) presented in “Note 8 – Employee Benefit Plans.”

Securities

Securities	9 Months Ended
	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Securities	Securities Debt securities The amortized cost, gross unrealized gains and losses and estimated fair value of investment and mortgage-backed AFS and HTM securities as of September 30, 2021 and December 31, 2020 are reflected in the tables below (in thousands): September 30, 2021 Amortized Gross Unrealized Gross Unrealized Estimated AVAILABLE FOR SALE Cost Gains Losses Fair Value Investment securities: U.S. Treasury $ 42,806 $ 741 $ — $ 43,547 State and political subdivisions 1,890,814 83,140 6,477 1,967,477 Corporate bonds and other 117,332 2,563 196 119,699 MBS: (1) Residential 493,505 20,943 370 514,078 Commercial 105,780 2,800 277 108,303 Total $ 2,650,237 $ 110,187 $ 7,320 $ 2,753,104 HELD TO MATURITY Investment securities: State and political subdivisions $ 788 $ 3 $ — $ 791 MBS: (1) Residential 40,128 2,616 — 42,744 Commercial 51,563 2,937 — 54,500 Total $ 92,479 $ 5,556 $ — $ 98,035 December 31, 2020 Amortized Gross Unrealized Gross Unrealized Estimated AVAILABLE FOR SALE Cost Gains Losses Fair Value Investment securities: State and political subdivisions $ 1,475,030 $ 105,601 $ 37 $ 1,580,594 Corporate bonds and other 77,224 1,053 22 78,255 MBS: (1) Residential 771,409 38,674 73 810,010 Commercial 113,850 4,746 150 118,446 Total $ 2,437,513 $ 150,074 $ 282 $ 2,587,305 HELD TO MATURITY Investment securities: State and political subdivisions $ 907 $ 13 $ — $ 920 MBS: (1) Residential 47,948 4,187 — 52,135 Commercial 60,143 5,000 — 65,143 Total $ 108,998 $ 9,200 $ — $ 118,198 (1) All MBS are issued and/or guaranteed by U.S. government agencies or U.S. GSEs. Investment securities and MBS with carrying values of $1.48 billion and $1.56 billion were pledged as of September 30, 2021 and December 31, 2020, respectively, to collateralize FHLB borrowings, borrowings from the FRDW, repurchase agreements and public fund deposits, for potential liquidity needs or other purposes as required by law. The following tables represent the fair value and unrealized losses on AFS investment securities and MBS for which an allowance for credit losses has not been recorded as of September 30, 2021 and December 31, 2020, segregated by major security type and length of time in a continuous loss position (in thousands): September 30, 2021 Less Than 12 Months More Than 12 Months Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss AVAILABLE FOR SALE Investment securities: State and political subdivisions $ 396,345 $ 6,477 $ — $ — $ 396,345 $ 6,477 Corporate bonds and other 21,352 196 — — 21,352 196 MBS: Residential 15,790 370 — — 15,790 370 Commercial — — 4,602 277 4,602 277 Total $ 433,487 $ 7,043 $ 4,602 $ 277 $ 438,089 $ 7,320 December 31, 2020 Less Than 12 Months More Than 12 Months Total Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized AVAILABLE FOR SALE Investment securities: State and political subdivisions $ 17,305 $ 37 $ — $ — $ 17,305 $ 37 Corporate bonds and other 11,562 22 — — 11,562 22 MBS: Residential 6,287 73 — — 6,287 73 Commercial 4,744 150 — — 4,744 150 Total $ 39,898 $ 282 $ — $ — $ 39,898 $ 282 For those AFS debt securities in an unrealized loss position where management (i) has the intent to sell or (ii) where it will more-likely-than-not be required to sell the security before the recovery of its amortized cost basis, we write the security down to fair value with an adjustment to earnings. For those AFS debt securities in an unrealized loss position that do not meet either of these criteria, management assesses whether the decline in fair value has resulted from credit-related factors, using both qualitative and quantitative criteria. Determining the allowance under the credit loss method requires the use of a discounted cash flow method to assess the credit losses. Any credit-related impairment will be recognized in allowance for credit losses on the balance sheet with a corresponding adjustment to earnings. Noncredit-related impairment, the portion of the impairment relating to factors other than credit (such as changes in market interest rates), is recognized in other comprehensive income, net of tax. Based on our consideration of the qualitative factors associated with each security type in our AFS portfolio, we did not recognize any unrealized losses in income on our AFS securities during the three and nine months ended September 30, 2021 or 2020. Our state and political subdivisions are highly rated municipal securities with a long history of no credit losses. Our AFS MBS are highly rated securities which are either explicitly or implicitly backed by the U.S. Government through its agencies which are highly rated by major ratings agencies and also have a long history of no credit losses. Our corporate bonds and other investment securities as of September 30, 2021 consist of highly rated investment grade bonds. Management does not intend to sell and it is likely we will not be required to sell those securities in an unrealized loss position prior to the anticipated recovery of the amortized cost basis. These unrealized losses on our investment and MBS are due to changes in interest rates and spreads and other market conditions impacted by COVID-19. As of September 30, 2021 and December 31, 2020, we did not have an allowance for credit losses on our AFS securities. We assess the likelihood of default and the potential amount of default when assessing our HTM securities for credit losses. We utilize term structures and, due to no prior loss exposure on our state and political subdivision securities, we currently apply a third-party average loss given default rate to model our securities. Due to a small number of HTM municipal securities in our portfolio as of September 30, 2021 and 2020, we elected to use the specific identification method to model these securities which aligns with our third-party fair value measurement process. The model determined any expected credit loss over the life of these securities to be remote. Management further evaluated the remote expectation of loss along with the qualitative factors associated with these securities and concluded that, due to the securities being highly rated municipals with a long history of no credit losses, no credit loss should be recognized for these securities for the three and nine months ended September 30, 2021 or 2020. From time to time, we have transferred securities from AFS to HTM due to overall balance sheet strategies. The remaining net unamortized, unrealized loss on the transferred securities included in AOCI in the accompanying balance sheets totaled $1.7 million ($1.4 million, net of tax) at September 30, 2021 and $2.9 million ($2.3 million, net of tax) at December 31, 2020. Any net unrealized gain or loss on the transferred securities included in AOCI at the time of transfer will be amortized over the remaining life of the underlying security as an adjustment to the yield on those securities. Securities transferred with losses included in AOCI continue to be included in management’s assessment for impairment for each individual security. There were no securities transferred from AFS to HTM during the nine months ended September 30, 2021 or the year ended December 31, 2020. The accrued interest receivable on our debt securities is excluded from the credit loss estimate and is included in interest receivable on our consolidated balance sheets. As of September 30, 2021, accrued interest receivable on AFS and HTM debt securities totaled $15.5 million and $240,000, respectively. As of December 31, 2020, accrued interest receivable on AFS and HTM debt securities totaled $22.0 million and $298,000, respectively. No HTM debt securities were past-due or on nonaccrual status as of September 30, 2021 or December 31, 2020. The following table reflects interest income recognized on securities for the periods presented (in thousands): Three Months Ended 2021 2020 U.S. Treasury $ 182 $ — State and political subdivisions 12,223 9,787 Corporate bonds and other 1,097 391 MBS 4,405 7,048 Total interest income on securities $ 17,907 $ 17,226 Nine Months Ended 2021 2020 U.S. Treasury $ 388 $ — State and political subdivisions 33,568 26,281 Corporate bonds and other 2,928 568 MBS 15,140 27,626 Total interest income on securities $ 52,024 $ 54,475 There was a $3.4 million net realized gain from the AFS securities portfolio for the nine months ended September 30, 2021, which consisted of $3.5 million in realized gains and $71,000 in realized losses. There was a $8.3 million net realized gain from the AFS securities portfolio for the nine months ended September 30, 2020, which consisted of $8.4 million in realized gains and $89,000 in realized losses. There were no sales from the HTM portfolio during the nine months ended September 30, 2021 or 2020. We calculate realized gains and losses on sales of securities under the specific identification method. Expected maturities on our securities may differ from contractual maturities because issuers may have the right to call or prepay obligations. MBS are presented in total by category since MBS are typically issued with stated principal amounts and are backed by pools of mortgages that have loans with varying maturities. The characteristics of the underlying pool of mortgages, such as fixed-rate or adjustable-rate, as well as prepayment risk, are passed on to the security holder. The term of a mortgage-backed pass-through security thus approximates the term of the underlying mortgages and can vary significantly due to prepayments. The amortized cost and estimated fair value of AFS and HTM securities at September 30, 2021, are presented below by contractual maturity (in thousands): September 30, 2021 Amortized Cost Fair Value AVAILABLE FOR SALE Investment securities: Due in one year or less $ 4,495 $ 4,532 Due after one year through five years 26,705 27,841 Due after five years through ten years 175,953 180,006 Due after ten years 1,843,799 1,918,344 2,050,952 2,130,723 MBS: 599,285 622,381 Total $ 2,650,237 $ 2,753,104 September 30, 2021 Amortized Cost Fair Value HELD TO MATURITY Investment securities: Due in one year or less $ 120 $ 120 Due after one year through five years 529 531 Due after five years through ten years 139 140 Due after ten years — — 788 791 MBS: 91,691 97,244 Total $ 92,479 $ 98,035 Equity Investments Equity investments on our consolidated balance sheets include Community Reinvestment Act funds with a readily determinable fair value as well as equity investments without readily determinable fair values. At September 30, 2021 and December 31, 2020, we had equity investments recorded in our consolidated balance sheets of $11.8 million and $11.9 million, respectively. Any realized and unrealized gains and losses on equity investments are reported in income. Equity investments without readily determinable fair values are recorded at cost less impairment, if any. The following is a summary of unrealized and realized gains and losses on equity investments recognized in other noninterest income in the consolidated statements of income during the periods presented (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Net (losses) gains recognized during the period on equity investments $ (28) $ (232) $ (118) $ (178) Less: Net gains recognized during the period on equity investments sold during the period — — — — Unrealized (losses) gains recognized during the reporting period on equity investments held at the reporting date $ (28) $ (232) $ (118) $ (178) Equity investments are assessed quarterly for other-than-temporary impairment. Based upon that evaluation, management does not consider any of our equity investments to be other-than-temporarily impaired at September 30, 2021. FHLB Stock Our FHLB stock, which has limited marketability, is carried at cost and is assessed quarterly for other-than-temporary impairment. Based upon evaluation by management at September 30, 2021, our FHLB stock was not impaired and thus was not considered to be other-than-temporarily impaired.

Loans and Allowance for Loan Lo

Loans and Allowance for Loan Losses	9 Months Ended
	Sep. 30, 2021
Receivables [Abstract]
Loans and Allowance for Loan Losses	Loans and Allowance for Loan Losses Loans in the accompanying consolidated balance sheets are classified as follows (in thousands): September 30, 2021 December 31, 2020 Real estate loans: Construction $ 422,095 $ 581,941 1-4 family residential 660,689 719,952 Commercial 1,605,132 1,295,746 Commercial loans 443,708 557,122 Municipal loans 427,259 409,028 Loans to individuals 88,702 93,990 Total loans 3,647,585 3,657,779 Less: Allowance for loan losses 38,022 49,006 Net loans $ 3,609,563 $ 3,608,773 Paycheck Protection Program Loans In April 2020, we began originating loans to qualified small businesses under the PPP administered by the SBA under the provisions of the CARES Act. Loans covered by the PPP may be eligible for loan forgiveness for certain costs incurred related to payroll, group health care benefit costs and qualifying mortgage, rent and utility payments. The remaining loan balance after forgiveness of any amount is still fully guaranteed by the SBA. On December 27, 2020, the Economic Aid Act was signed into law. This second coronavirus relief package granted additional funds for a new round of PPP loans. Additionally, it expanded the eligibility for loans and allowed certain businesses to request a second loan. In return for processing and booking a PPP loan, the SBA paid lenders a processing fee tiered by the size of the loan. These loans are included in commercial loans with an amortized cost basis at September 30, 2021 and December 31, 2020 of $67.5 million and $214.8 million, respectively. Construction Real Estate Loans Our construction loans are collateralized by property located primarily in or near the market areas we serve. A number of our construction loans will be owner occupied upon completion. Construction loans for non-owner occupied projects are financed, but these typically have cash flows from leases with tenants, secondary sources of repayment, and in some cases, additional collateral. Our construction loans have both adjustable and fixed interest rates during the construction period. Construction loans to individuals are typically priced and made with the intention of granting the permanent loan on the completed property. Speculative and commercial construction loans are subject to underwriting standards similar to that of the commercial portfolio. Owner occupied 1-4 family residential construction loans are subject to the underwriting standards of the permanent loan. 1-4 Family Residential Real Estate Loans Residential loan originations are generated by our loan officers, in-house origination staff, marketing efforts, present customers, walk-in customers and referrals from real estate agents and builders. We focus our lending efforts primarily on the origination of loans secured by first mortgages on owner occupied 1-4 family residences. Substantially all of our 1-4 family residential originations are secured by properties located in or near our market areas. Our 1-4 family residential loans generally have maturities ranging from five Underwriting for 1-4 family residential loans includes debt-to-income analysis, credit history analysis, appraised value and down payment considerations. Changes in the market value of real estate can affect the potential losses in the residential portfolio. Commercial Real Estate Loans Commercial real estate loans as of September 30, 2021 consisted of $1.32 billion of owner and non-owner occupied real estate, $260.1 million of loans secured by multi-family properties and $22.0 million of loans secured by farmland. Commercial real estate loans primarily include loans collateralized by retail, commercial office buildings, multi-family residential buildings, medical facilities and offices, senior living, assisted living and skilled nursing facilities, warehouse facilities, hotels and churches. In determining whether to originate commercial real estate loans, we generally consider such factors as the financial condition of the borrower and the debt service coverage of the property. Commercial real estate loans are made at both fixed and adjustable interest rates for terms generally up to 20 years. Commercial Loans Our commercial loans are diversified loan types including short-term working capital loans for inventory and accounts receivable and short- and medium-term loans for equipment or other business capital expansion. In our commercial loan underwriting, we assess the creditworthiness, ability to repay and the value and liquidity of the collateral being offered. Terms of commercial loans are generally commensurate with the useful life of the collateral offered. Municipal Loans We make loans to municipalities and school districts primarily throughout the state of Texas, with a small percentage originating outside of the state. The majority of the loans to municipalities and school districts have tax or revenue pledges and in some cases are additionally supported by collateral. Municipal loans made without a direct pledge of taxes or revenues are usually made based on some type of collateral that represents an essential service. Lending money directly to these municipalities allows us to earn a higher yield than we could if we purchased municipal securities for similar durations. Loans to Individuals Substantially all originations of our loans to individuals are made to consumers in our market areas. The majority of loans to individuals are collateralized by titled equipment, which are primarily automobiles. Loan terms vary according to the type and value of collateral, length of contract and creditworthiness of the borrower. The underwriting standards we employ for consumer loans include an application, a determination of the applicant’s payment history on other debts, with the greatest weight being given to payment history with us and an assessment of the borrower’s ability to meet existing obligations and payments on the proposed loan. Although creditworthiness of the applicant is a primary consideration, the underwriting process also includes a comparison of the value of the collateral, if any, in relation to the proposed loan amount. Most of our loans to individuals are collateralized, which management believes assists in limiting our exposure. Credit Quality Indicators We categorize loans into risk categories on an ongoing basis based on relevant information about the ability of borrowers to service their debt such as: current financial information, historical payment experience, credit documentation, public information and current economic trends, among other factors. We use the following definitions for risk ratings: • Pass (Rating 1 – 4) – This rating is assigned to all satisfactory loans. This category, by definition, consists of acceptable credit. Credit and collateral exceptions should not be present, although their presence would not necessarily prohibit a loan from being rated Pass, if deficiencies are in the process of correction. These loans are not included in the Watch List. • Pass Watch (Rating 5) – These loans require some degree of special treatment, but not due to credit quality. This category does not include loans specially mentioned or adversely classified; however, particular attention is warranted to characteristics such as: ▪ A lack of, or abnormally extended payment program; ▪ A heavy degree of concentration of collateral without sufficient margin; ▪ A vulnerability to competition through lesser or extensive financial leverage; and ▪ A dependence on a single or few customers or sources of supply and materials without suitable substitutes or alternatives. • Special Mention (Rating 6) – A Special Mention loan has potential weaknesses that deserve management’s close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the loan or in our credit position at some future date. Special Mention loans are not adversely classified and do not expose us to sufficient risk to warrant adverse classification. • Substandard (Rating 7) – Substandard loans are inadequately protected by the current sound worth and paying capacity of the obligor or of the collateral pledged, if any. Loans so classified must have a well-defined weakness or weaknesses that jeopardize the liquidation of the debt. They are characterized by the distinct possibility that the Bank will sustain some loss if the deficiencies are not corrected. • Doubtful (Rating 8) – Loans classified as Doubtful have all the weaknesses inherent in those classified Substandard with the added characteristic that the weaknesses make collection or liquidation, in full, on the basis of currently known facts, conditions and values, highly questionable and improbable. The following tables set forth the amortized cost basis by class of financing receivable and credit quality indicator for the periods presented (in thousands): September 30, 2021 Term Loans Amortized Cost Basis by Origination Year Revolving Loans Amortized Cost Basis Total 2021 2020 2019 2018 2017 Prior Construction real estate: Pass $ 117,946 $ 107,623 $ 56,826 $ 6,343 $ 2,209 $ 6,755 $ 124,101 $ 421,803 Pass watch — — — — — 21 — 21 Special mention — — — — — — — — Substandard — — — — — 217 — 217 Doubtful — — — 54 — — — 54 Total construction real estate $ 117,946 $ 107,623 $ 56,826 $ 6,397 $ 2,209 $ 6,993 $ 124,101 $ 422,095 1-4 family residential real estate: Pass $ 111,806 $ 134,208 $ 89,450 $ 52,699 $ 38,027 $ 226,835 $ 2,239 $ 655,264 Pass watch — — — — — 803 — 803 Special mention — — — — — 62 — 62 Substandard 9 483 54 — 430 3,227 89 4,292 Doubtful — 9 — — — 259 — 268 Total 1-4 family residential real estate $ 111,815 $ 134,700 $ 89,504 $ 52,699 $ 38,457 $ 231,186 $ 2,328 $ 660,689 Commercial real estate: Pass $ 448,184 $ 237,377 $ 317,768 $ 127,342 $ 154,680 $ 230,388 $ 6,281 $ 1,522,020 Pass watch — — 4,163 23,242 22,159 1,645 — 51,209 Special mention — 197 — — 168 1,919 — 2,284 Substandard 3,449 609 8,882 8,563 — 7,991 — 29,494 Doubtful — — — — — 125 — 125 Total commercial real estate $ 451,633 $ 238,183 $ 330,813 $ 159,147 $ 177,007 $ 242,068 $ 6,281 $ 1,605,132 Commercial loans: Pass $ 131,981 $ 78,247 $ 28,930 $ 15,234 $ 4,147 $ 6,166 $ 174,372 $ 439,077 Pass watch 39 55 504 25 — — — 623 Special mention — — 124 381 — 183 373 1,061 Substandard 91 194 379 165 20 1 1,457 2,307 Doubtful 8 25 141 386 — 80 — 640 Total commercial loans $ 132,119 $ 78,521 $ 30,078 $ 16,191 $ 4,167 $ 6,430 $ 176,202 $ 443,708 Municipal loans: Pass $ 56,206 $ 65,884 $ 63,328 $ 30,504 $ 57,665 $ 153,672 $ — $ 427,259 Pass watch — — — — — — — — Special mention — — — — — — — — Substandard — — — — — — — — Doubtful — — — — — — — — Total municipal loans $ 56,206 $ 65,884 $ 63,328 $ 30,504 $ 57,665 $ 153,672 $ — $ 427,259 Loans to individuals: Pass $ 34,329 $ 28,335 $ 14,196 $ 5,195 $ 2,188 $ 1,068 $ 3,236 $ 88,547 Pass watch — — — — — — — — Special mention — — — 40 — — — 40 Substandard — 1 27 14 22 10 1 75 Doubtful — — 1 11 10 18 — 40 Total loans to individuals $ 34,329 $ 28,336 $ 14,224 $ 5,260 $ 2,220 $ 1,096 $ 3,237 $ 88,702 Total loans $ 904,048 $ 653,247 $ 584,773 $ 270,198 $ 281,725 $ 641,445 $ 312,149 $ 3,647,585 December 31, 2020 Term Loans Amortized Cost Basis by Origination Year Revolving Loans Amortized Cost Basis Total 2020 2019 2018 2017 2016 Prior Construction real estate: Pass $ 155,693 $ 180,536 $ 76,090 $ 55,636 $ 3,191 $ 8,297 $ 101,793 $ 581,236 Pass watch — — — — 23 — — 23 Special mention — — — — — — — — Substandard — 382 62 — — 58 — 502 Doubtful — — — — — 180 — 180 Total construction real estate $ 155,693 $ 180,918 $ 76,152 $ 55,636 $ 3,214 $ 8,535 $ 101,793 $ 581,941 1-4 family residential real estate: Pass $ 154,003 $ 114,063 $ 70,621 $ 55,557 $ 57,680 $ 255,003 $ 2,833 $ 709,760 Pass watch — — — — 267 564 — 831 Special mention — — — — — 10 — 10 Substandard 1,473 — 135 427 1,588 5,134 96 8,853 Doubtful — — — 36 103 359 — 498 Total 1-4 family residential real estate $ 155,476 $ 114,063 $ 70,756 $ 56,020 $ 59,638 $ 261,070 $ 2,929 $ 719,952 Commercial real estate: Pass $ 270,087 $ 307,161 $ 143,177 $ 162,180 $ 98,828 $ 179,919 $ 6,957 $ 1,168,309 Pass watch — — 3,153 40,125 1,696 2,582 — 47,556 Special mention 4,555 33,020 7,041 140 4,531 7,850 — 57,137 Substandard 7,542 — 2,097 65 704 12,282 — 22,690 Doubtful — — — — — 54 — 54 Total commercial real estate $ 282,184 $ 340,181 $ 155,468 $ 202,510 $ 105,759 $ 202,687 $ 6,957 $ 1,295,746 Commercial loans: Pass $ 313,688 $ 47,446 $ 20,386 $ 7,505 $ 3,392 $ 6,142 $ 140,018 $ 538,577 Pass watch 2,599 1,318 2,410 1,981 — — 370 8,678 Special mention 304 809 433 39 286 265 455 2,591 Substandard 405 1,081 473 7 — — 4,417 6,383 Doubtful 310 53 475 54 1 — — 893 Total commercial loans $ 317,306 $ 50,707 $ 24,177 $ 9,586 $ 3,679 $ 6,407 $ 145,260 $ 557,122 Municipal loans: Pass $ 72,542 $ 68,132 $ 33,735 $ 61,170 $ 25,387 $ 148,062 $ — $ 409,028 Pass watch — — — — — — — — Special mention — — — — — — — — Substandard — — — — — — — — Doubtful — — — — — — — — Total municipal loans $ 72,542 $ 68,132 $ 33,735 $ 61,170 $ 25,387 $ 148,062 $ — $ 409,028 Loans to individuals: Pass $ 46,722 $ 25,302 $ 10,132 $ 4,716 $ 1,867 $ 917 $ 3,900 $ 93,556 Pass watch — — — — — — — — Special mention — — 51 — — — 4 55 Substandard 6 35 28 30 9 11 1 120 Doubtful 73 20 6 55 81 24 — 259 Total loans to individuals $ 46,801 $ 25,357 $ 10,217 $ 4,801 $ 1,957 $ 952 $ 3,905 $ 93,990 Total loans $ 1,030,002 $ 779,358 $ 370,505 $ 389,723 $ 199,634 $ 627,713 $ 260,844 $ 3,657,779 The following tables present the aging of the amortized cost basis in past due loans by class of loans (in thousands): September 30, 2021 30-59 Days Past Due 60-89 Days Past Due Greater than 90 Days Past Due Total Past Due Current Total Real estate loans: Construction $ 72 $ 41 $ — $ 113 $ 421,982 $ 422,095 1-4 family residential 652 691 580 1,923 658,766 660,689 Commercial 885 — — 885 1,604,247 1,605,132 Commercial loans 1,402 233 31 1,666 442,042 443,708 Municipal loans 96 — — 96 427,163 427,259 Loans to individuals 265 14 12 291 88,411 88,702 Total $ 3,372 $ 979 $ 623 $ 4,974 $ 3,642,611 $ 3,647,585 December 31, 2020 30-59 Days Past Due 60-89 Days Past Due Greater than 90 Days Total Past Due Current Total Real estate loans: Construction $ 95 $ 14 $ 444 $ 553 $ 581,388 $ 581,941 1-4 family residential 7,872 2,469 2,830 13,171 706,781 719,952 Commercial 467 315 86 868 1,294,878 1,295,746 Commercial loans 1,423 4,516 323 6,262 550,860 557,122 Municipal loans 64 — — 64 408,964 409,028 Loans to individuals 519 123 27 669 93,321 93,990 Total $ 10,440 $ 7,437 $ 3,710 $ 21,587 $ 3,636,192 $ 3,657,779 The following table sets forth the amortized cost basis of nonperforming assets for the periods presented (in thousands): September 30, 2021 December 31, 2020 Nonaccrual loans: Real estate loans: Construction $ 63 $ 640 1-4 family residential 1,432 3,922 Commercial 796 1,269 Commercial loans 674 1,592 Loans to individuals 48 291 Total nonaccrual loans (1) 3,013 7,714 Accruing loans past due more than 90 days — — TDR loans 9,371 9,646 OREO 25 106 Repossessed assets 15 14 Total nonperforming assets $ 12,424 $ 17,480 (1) Includes $1.1 million and $976,000 of restructured loans as of September 30, 2021 and December 31, 2020, respectively. We reversed $5,000 and $13,000 of interest income on nonaccrual loans during the three and nine months ended September 30, 2021, respectively, and $147,000 for the nine months ended September 30, 2020. There was no interest income reversed on nonaccrual loans during the three months ended September 30, 2020. We had $1.1 million and $2.2 million of loans on nonaccrual for which there was no related allowance for credit losses as of September 30, 2021 and December 31, 2020, respectively. Collateral-dependent loans are loans that we expect the repayment to be provided substantially through the operation or sale of the collateral of the loan and we have determined that the borrower is experiencing financial difficulty. In such cases, expected credit losses are based on the fair value of the collateral at the measurement date, adjusted for selling costs. As of September 30, 2021 and December 31, 2020, we had $9.1 million and $11.5 million, respectively, of collateral-dependent loans, secured mainly by real estate and equipment. There have been no significant changes to the collateral that secures the collateral-dependent assets. Foreclosed assets include OREO and repossessed assets. For 1-4 family residential real estate properties, a loan is recognized as a foreclosed property once legal title to the real estate property has been received upon completion of foreclosure or the borrower has conveyed all interest in the residential property through a deed in lieu of foreclosure. There were no loans secured by 1-4 family residential properties for which formal foreclosure proceedings were in process as of September 30, 2021. As of December 31, 2020, there were $1.2 million in loans secured by 1-4 family residential properties for which formal foreclosure proceedings were in process. Troubled Debt Restructurings The restructuring of a loan is considered a TDR if both (i) the borrower is experiencing financial difficulties and (ii) the creditor has granted a concession. Concessions may include interest rate reductions or below market interest rates, restructuring amortization schedules and other actions intended to minimize potential losses. We may provide a combination of concessions which may include an extension of the amortization period, interest rate reduction and/or converting the loan to interest-only for a limited period of time. In response to the impact of the COVID-19 pandemic on the economy, the CARES Act was signed into law. Under the CARES Act, banks may elect to deem that loan modifications do not result in TDRs if they are: (1) related to COVID-19; (2) executed on a loan that was not more than 30 days past due as of December 31, 2019; and (3) executed between March 1, 2020, and the earlier of (A) 60 days after the date of termination of the national emergency declaration or (B) December 31, 2020. The Economic Aid Act extended this relief to the earlier of 60 days after the national emergency termination date or January 1, 2022. Additionally, in accordance with the Interagency Statement on Loan Modifications and Reporting for Financial Institutions Working with Customers Affected by the Coronavirus (Revised), other short-term modifications made on a good faith basis in response to COVID-19 to borrowers who were current prior to any relief are not TDRs under ASC Subtopic 310-40. This includes short-term (e.g., up to six months) modifications such as payment deferrals, fee waivers, extensions of repayment terms, or delays in payment that are insignificant. Borrowers considered current are those that are less than 30 days past due on their contractual payments at the time a modification program is implemented. Loans modified under this guidance are not considered TDRs and as such are not identified in the table below. At September 30, 2021 there were no loans with outstanding payment deferrals. As of December 31, 2020, we had outstanding loans with payment deferrals totaling $47.2 million. The following tables set forth the recorded balance of loans considered to be TDRs that were restructured and the type of concession by class of loans during the periods presented (dollars in thousands): Three Months Ended September 30, 2021 Extend Amortization Period Interest Rate Reductions Combination Total Modifications Number of Loans Real estate loans: 1-4 family residential $ — $ — $ 219 $ 219 3 Commercial — — 453 453 1 Total $ — $ — $ 672 $ 672 4 Nine Months Ended September 30, 2021 Extend Amortization Period Interest Rate Reductions Combination Total Modifications Number of Loans Real estate loans: 1-4 family residential $ — $ — $ 344 $ 344 5 Commercial — — 453 453 1 Commercial loans — 16 94 110 3 Total $ — $ 16 $ 891 $ 907 9 Nine Months Ended September 30, 2020 Extend Amortization Period Interest Rate Reductions Combination Total Modifications Number of Loans Real estate loans: Commercial $ — $ — $ 58 $ 58 1 Commercial loans — — 117 117 3 Total $ — $ — $ 175 $ 175 4 There were no TDRs restructured during the three months ended September 30, 2020. Interest continues to be charged on principal balances outstanding during the extended term. Therefore, the financial effects of the recorded investment of loans restructured as TDRs during the nine months ended September 30, 2021 and 2020 were not significant. On an ongoing basis, the performance of the TDRs is monitored for subsequent payment default. Payment default for TDRs is recognized when the borrower is 90 days or more past due. For the three and nine months ended September 30, 2021 and 2020 the amount of TDRs in default was not significant. Payment defaults for TDRs did not significantly impact the determination of the allowance for loan losses in the periods presented. At September 30, 2021 and 2020, there were no commitments to lend additional funds to borrowers whose terms had been modified in TDRs. Allowance for Loan Losses In accordance with ASC 326, the allowance for credit losses on loans is estimated and recognized upon origination of the loan based on expected credit losses. The CECL model uses historical experience and current conditions for homogeneous pools of loans, and reasonable and supportable forecasts about future events. The impact of varying economic conditions and portfolio stress factors are a component of the credit loss models applied to each portfolio. Reserve factors are specific to the loan segments that share similar risk characteristics based on the probability of default assumptions and loss given default assumptions, over the contractual term. The forecasted periods gradually mean-revert the economic inputs to their long-run historical trends. Management evaluates the economic data points used in the Moody’s forecasting scenarios on a quarterly basis to determine the most appropriate impact to the various portfolio characteristics based on management’s view and applies weighting to various forecasting scenarios as deemed appropriate based on known and expected economic activities. Management also considers and may apply relevant qualitative factors, not previously considered, to determine the appropriate allowance level. The use of the CECL model includes significant judgment by management and may differ from those of our peers due to different historical loss patterns, economic forecasts, and the length of time of the reasonable and supportable forecast period and reversion period. We utilize Moody’s Analytics economic forecast scenarios and assign probability weighting to those scenarios which best reflect management’s views on the economic forecast. The probability weighting and scenarios utilized for the estimate of the allowance were generally reflective of an improved economic forecast based on known and knowable information as of September 30, 2021. When determining the appropriate allowance for credit losses on our loan portfolio, our commercial construction and real estate loans, commercial loans and municipal loans utilize the probability of default/loss given default discounted cash flow approach. Reserves on these loans are based upon risk factors including the loan type and structure, collateral type, leverage ratio, refinancing risk and origination quality, among others. Our consumer construction real estate loans, 1-4 family residential loans and our loans to individuals use a loss rate based upon risk factors including loan types, origination year and credit scores. Loans covered by the PPP may be eligible for loan forgiveness. The remaining loan balance after forgiveness of any amount is still fully guaranteed by the SBA and therefore does not have an associated allowance. Loans evaluated collectively in a pool are monitored to ensure they continue to exhibit similar risk characteristics with other loans in the pool. If a loan does not share similar risk characteristics with other loans, expected credit losses for that loan are evaluated individually. The following tables detail activity in the allowance for loan losses by portfolio segment for the periods presented (in thousands): Three Months Ended September 30, 2021 Real Estate Construction 1-4 Family Residential Commercial Commercial Loans Municipal Loans Loans to Individuals Total Balance at beginning of period $ 8,018 $ 2,520 $ 28,930 $ 3,097 $ 47 $ 301 $ 42,913 Loans charged-off — (35) — (508) — (397) (940) Recoveries of loans charged-off 1 4 12 74 — 346 437 Net loans (charged-off) recovered 1 (31) 12 (434) — (51) (503) Provision for (reversal of) loan losses (3,036) (543) (684) (103) (1) (21) (4,388) Balance at end of period $ 4,983 $ 1,946 $ 28,258 $ 2,560 $ 46 $ 229 $ 38,022 Nine Months Ended September 30, 2021 Real Estate Construction 1-4 Family Residential Commercial Commercial Loans Municipal Loans Loans to Individuals Total Balance at beginning of period $ 6,490 $ 2,270 $ 35,709 $ 4,107 $ 46 $ 384 $ 49,006 Loans charged-off — (136) — (943) — (1,183) (2,262) Recoveries of loans charged-off 2 71 13 535 — 904 1,525 Net loans (charged-off) recovered 2 (65) 13 (408) — (279) (737) Provision for (reversal of) loan losses (1,509) (259) (7,464) (1,139) — 124 (10,247) Balance at end of period $ 4,983 $ 1,946 $ 28,258 $ 2,560 $ 46 $ 229 $ 38,022 Three Months Ended September 30, 2020 Real Estate Construction 1-4 Family Residential Commercial Commercial Loans Municipal Loans Loans to Individuals Total Balance at beginning of period $ 8,500 $ 2,702 $ 43,785 $ 4,221 $ 47 $ 613 $ 59,868 Loans charged-off (6) (18) (12) (279) — (403) (718) Recoveries of loans charged-off — 9 13 61 — 278 361 Net loans (charged-off) recovered (6) (9) 1 (218) — (125) (357) Provision for (reversal of) loan losses (2,868) (58) (2,001) 489 (1) 38 (4,401) Balance at end of period $ 5,626 $ 2,635 $ 41,785 $ 4,492 $ 46 $ 526 $ 55,110 Nine Months Ended September 30, 2020 Real Estate Construction 1-4 Family Residential Commercial Commercial Loans Municipal Loans Loans to Individuals Total Balance at beginning of period $ 3,539 $ 3,833 $ 9,572 $ 6,351 $ 570 $ 932 $ 24,797 Impact of CECL adoption - cumulative effect adjustment 2,968 (1,447) 7,730 (3,532) (522) (125) 5,072 Impact of CECL adoption - purchased loans with credit deterioration (15) (6) 333 (22) — (59) 231 Loans charged-off (39) (74) (33) (800) — (1,313) (2,259) Recoveries of loans charged-off 11 29 94 191 — 923 1,248 Net loans (charged-off) recovered (28) (45) 61 (609) — (390) (1,011) Provision for (reversal of) loan losses (1) (838) 300 24,089 2,304 (2) 168 26,021 Balance at end of period $ 5,626 $ 2,635 $ 41,785 $ 4,492 $ 46 $ 526 $ 55,110 (1) The increase in the provision for credit losses during the nine months ended September 30, 2020 was primarily due to the economic impact of COVID-19 on macroeconomic factors used in the CECL model. The accrued interest receivable on our loan receivables is excluded from the allowance for credit loss estimate and is included in interest receivable on our consolidated balance sheets. As of September 30, 2021 and December 31, 2020, the accrued interest on our loan portfolio was $13.3 million and $16.4 million, respectively.

Borrowing Arrangements

Borrowing Arrangements	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Borrowing Arrangements	Borrowing Arrangements Information related to borrowings is provided in the table below (dollars in thousands): September 30, 2021 December 31, 2020 Other borrowings: Balance at end of period $ 20,724 $ 23,172 Average amount outstanding during the period (1) 22,387 91,940 Maximum amount outstanding during the period (2) 24,549 219,259 Weighted average interest rate during the period (3) 0.2 % 0.4 % Interest rate at end of period (4) 0.2 % 0.1 % FHLB borrowings: Balance at end of period $ 659,204 $ 832,527 Average amount outstanding during the period (1) 684,280 1,032,269 Maximum amount outstanding during the period (2) 723,584 1,274,370 Weighted average interest rate during the period (3) 1.1 % 1.1 % Interest rate at end of period (5) 1.1 % 1.0 % (1) The average amount outstanding during the period was computed by dividing the total daily outstanding principal balances by the number of days in the period. (2) The maximum amount outstanding at any month-end during the period. (3) The weighted average interest rate during the period was computed by dividing the actual interest expense (annualized for interim periods) by the average amount outstanding during the period. The weighted average interest rate on the FHLB borrowings includes the effect of interest rate swaps. (4) Stated rate. (5) The interest rate on the FHLB borrowings includes the effect of interest rate swaps. Maturities of the obligations associated with our borrowing arrangements based on scheduled repayments at September 30, 2021 are as follows (in thousands): Payments Due by Period Less than 1-2 Years 2-3 Years 3-4 Years 4-5 Years Thereafter Total Other borrowings $ 20,724 $ — $ — $ — $ — $ — $ 20,724 FHLB borrowings 655,673 702 733 764 582 750 659,204 Total obligations $ 676,397 $ 702 $ 733 $ 764 $ 582 $ 750 $ 679,928 Other borrowings include federal funds purchased, repurchase agreements and borrowings from the FRDW. Southside Bank has three unsecured lines of credit for the purchase of overnight federal funds at prevailing rates with Frost Bank, TIB – The Independent Bankers Bank and Comerica Bank for $40.0 million, $15.0 million and $7.5 million, respectively. There were no federal funds purchased at September 30, 2021 or December 31, 2020. To provide more liquidity in response to the economic impact of the COVID-19 pandemic, the Federal Reserve took steps to encourage broader use of the discount window. At September 30, 2021, the amount of additional funding the Bank could obtain from the FRDW, collateralized by securities, was approximately $476.1 million. There were no borrowings from the FRDW at September 30, 2021 or December 31, 2020. Southside Bank has a $5.0 million line of credit with Frost Bank to be used to issue letters of credit, and at September 30, 2021, the line had one outstanding letter of credit for $91,000. Southside Bank currently has no outstanding letters of credit from FHLB held as collateral for its public fund deposits. Southside Bank enters into sales of securities under repurchase agreements. These repurchase agreements totaled $20.7 million at September 30, 2021 and $23.2 million at December 31, 2020, and had maturities of less than one year. Repurchase agreements are secured by investment and MBS securities and are stated at the amount of cash received in connection with the transaction. FHLB borrowings represent borrowings with fixed interest rates ranging from 0.13% to 4.799% and with remaining maturities of four days to 6.8 years at September 30, 2021. FHLB borrowings may be collateralized by FHLB stock, nonspecified loans and/or securities. At September 30, 2021, the amount of additional funding Southside Bank could obtain from FHLB, collateralized by securities, FHLB stock and nonspecified loans and securities, was approximately $1.22 billion, net of FHLB stock purchases required. Southside Bank has entered into various variable rate agreements and fixed rate short-term pay agreements with third-party financial institutions with rates tied to LIBOR. These agreements totaled $605.0 million at September 30, 2021 and $670.0 million at December 31, 2020. Six of the agreements have an interest rate tied to three-month LIBOR, and the remaining agreements have interest rates tied to one-month LIBOR. In connection with all of these agreements, Southside Bank also entered into various interest rate swap contracts that are treated as cash flow hedges under ASC Topic 815, “Derivatives and Hedging” that are expected to be effective in hedging the variability in future cash flows attributable to fluctuations in the underlying LIBOR interest rate. The interest rate swap contracts had a weighted average rate of 1.18% with a weighted average maturity of 3.4 years at September 30, 2021. Refer to “Note 9 – Derivative Financial Instruments and Hedging Activities” in our consolidated financial statements included in this report for a detailed description of our hedging policy and methodology related to derivative instruments.

Long-term Debt

Long-term Debt	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Long-term Debt	Long-term Debt Information related to our long-term debt is summarized as follows for the periods presented (in thousands): September 30, 2021 December 31, 2020 Subordinated notes: (1) 3.875% Subordinated notes, net of unamortized debt issuance costs (2) $ 98,500 $ 98,497 5.50% Subordinated notes, net of unamortized debt issuance costs (3) — 98,754 Total Subordinated notes 98,500 197,251 Trust preferred subordinated debentures: (4) Southside Statutory Trust III, net of unamortized debt issuance costs (5) 20,567 20,563 Southside Statutory Trust IV 23,196 23,196 Southside Statutory Trust V 12,887 12,887 Magnolia Trust Company I 3,609 3,609 Total Trust preferred subordinated debentures 60,259 60,255 Total Long-term debt $ 158,759 $ 257,506 (1) This debt consists of subordinated notes with a remaining maturity greater than one year that qualify under the risk-based capital guidelines as Tier 2 capital, subject to certain limitations. (2) The unamortized discount and debt issuance costs reflected in the carrying amount of the subordinated notes totaled approximately $1.5 million at September 30, 2021 and December 31, 2020. (3) The unamortized discount and debt issuance costs reflected in the carrying amount of the subordinated notes totaled approximately $1.2 million at December 31, 2020. (4) This debt consists of trust preferred securities that qualify under the risk-based capital guidelines as Tier 1 capital, subject to certain limitations. (5) The unamortized debt issuance costs reflected in the carrying amount of the Southside Statutory Trust III junior subordinated debentures totaled $52,000 at September 30, 2021 and $56,000 at December 31, 2020. As of September 30, 2021, the details of the subordinated notes and the trust preferred subordinated debentures are summarized below (dollars in thousands): Date Issued Amount Issued Fixed or Floating Rate Interest Rate Maturity Date 3.875% Subordinated Notes November 6, 2020 $ 100,000 Fixed-to-Floating 3.875% November 15, 2030 Southside Statutory Trust III September 4, 2003 $ 20,619 Floating 3 month LIBOR + 2.94% September 4, 2033 Southside Statutory Trust IV August 8, 2007 $ 23,196 Floating 3 month LIBOR + 1.30% October 30, 2037 Southside Statutory Trust V August 10, 2007 $ 12,887 Floating 3 month LIBOR + 2.25% September 15, 2037 Magnolia Trust Company I (1) May 20, 2005 $ 3,609 Floating 3 month LIBOR + 1.80% November 23, 2035 (1) On October 10, 2007, as part of an acquisition we assumed $3.6 million of floating rate junior subordinated debentures issued in 2005 to Magnolia Trust Company I. On September 19, 2016, the Company issued $100.0 million in aggregate principal amount of fixed-to-floating rate subordinated notes that mature on September 30, 2026. This debt initially bore interest at a fixed rate of 5.50% through September 29, 2021 and thereafter, was to adjust quarterly at a floating rate equal to three-month LIBOR plus 429.7 basis points. On September 30, 2021, the Company completed the redemption of these subordinated notes. The redemption price for

Employee Benefit Plans

Employee Benefit Plans	9 Months Ended
	Sep. 30, 2021
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Employee Benefit Plans	Employee Benefit Plans The components of net periodic benefit cost (income) related to our employee benefit plans are as follows (in thousands): Three Months Ended September 30, Defined Benefit Defined Benefit Restoration 2021 2020 2021 2020 2021 2020 Service cost $ — $ 483 $ — $ — $ — $ 149 Interest cost 642 672 23 41 130 126 Expected return on assets (1,355) (1,344) (53) (75) — — Net loss amortization 251 694 1 2 64 125 Prior service (credit) cost amortization — (4) — — — 2 Net periodic benefit (income) cost $ (462) $ 501 $ (29) $ (32) $ 194 $ 402 Nine Months Ended September 30, Defined Benefit Defined Benefit Restoration 2021 2020 2021 2020 2021 2020 Service cost $ — $ 1,311 $ — $ — $ — $ 280 Interest cost 1,927 2,359 69 122 390 442 Expected return on assets (4,065) (4,332) (158) (226) — — Net loss amortization 752 1,780 4 7 192 426 Prior service (credit) cost amortization — (11) — — — 5 Loss due to curtailment — 151 — — — 12 Net periodic benefit (income) cost $ (1,386) $ 1,258 $ (85) $ (97) $ 582 $ 1,165 Prior to the freeze of all future benefit accruals and accrual of benefit service as of December 31, 2020, the service cost component was recorded on our consolidated income statements as salaries and employee benefits in noninterest expense. All other components other than service costs are recorded in other noninterest expense. During the three months ended June 30, 2021, we updated our expected long-term rate of return on plan assets for the Retirement Plan and the Acquired Retirement Plan from 6.50% to 6.125%. The noncash adjustment to the employee benefit plan liabilities, consisting of changes in prior service cost and net loss, was $948,000 and $5.2 million for the nine months ended September 30, 2021 and 2020, respectively.

Derivative Financial Instrument

Derivative Financial Instruments and Hedging Activities	9 Months Ended
	Sep. 30, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments and Hedging Activities	Derivative Financial Instruments and Hedging Activities Our hedging policy allows the use of interest rate derivative instruments to manage our exposure to interest rate risk or hedge specified assets and liabilities. These instruments may include interest rate swaps and interest rate caps and floors. All derivative instruments are carried on the balance sheet at their estimated fair value and are recorded in other assets or other liabilities, as appropriate. Derivative instruments may be designated as cash flow hedges of variable rate assets or liabilities, cash flow hedges of forecasted transactions, fair value hedges of a recognized asset or liability or as non-hedging instruments. Gains and losses on derivative instruments designated as cash flow hedges are recorded in AOCI to the extent they are effective. If the hedge is effective, the amount recorded in other comprehensive income is reclassified to earnings in the same periods that the hedged cash flows impact earnings. The ineffective portion of changes in fair value is reported in current earnings. Gains and losses on derivative instruments designated as fair value hedges, as well as the change in fair value on the hedged item, are recorded in interest income in the consolidated statements of income. Gains and losses due to changes in fair value of the interest rate swap agreements completely offset changes in the fair value of the hedged portion of the hedged item. For derivative instruments not designated as hedging instruments, the gain or loss is recognized in current earnings during the period of change. We have entered into certain interest rate swap contracts on specific variable rate agreements and fixed rate short-term pay agreements with third-party financial institutions. These interest rate swap contracts were designated as hedging instruments in cash flow hedges under ASC Topic 815. The objective of the interest rate swap contracts is to manage the expected future cash flows on $605.0 million of debt. The cash flows from the swap contracts are expected to be effective in hedging the variability in future cash flows attributable to fluctuations in the underlying LIBOR interest rate. In accordance with ASC Topic 815, if a hedging item is terminated prior to maturity for a cash settlement, the existing gain or loss within AOCI will continue to be reclassified into earnings during the period or periods in which the hedged forecasted transaction affects earnings unless it is probable the forecasted transaction will not occur by the end of the originally specified time period. These transactions are reevaluated on a monthly basis to determine if the hedged forecasted transactions are still probable of occurring. If at a subsequent evaluation, it is determined that the transactions will not occur, any related gains or losses recorded in AOCI are immediately recognized in earnings. From time to time, we may enter into certain interest rate swaps, cap and floor contracts that are not designated as hedging instruments. These interest rate derivative contracts relate to transactions in which we enter into an interest rate swap, cap or floor with a customer while concurrently entering into an offsetting interest rate swap, cap or floor with a third party financial institution. We agree to pay interest to the customer on a notional amount at a variable rate and receive interest from the customer on a similar notional amount at a fixed interest rate. At the same time, we agree to pay a third party financial institution the same fixed interest rate on the same notional amount and receive the same variable interest rate on the same notional amount. These interest rate derivative contracts allow our customers to effectively convert a variable rate loan to a fixed rate loan. The changes in the fair value of the underlying derivative contracts primarily offset each other and do not significantly impact our results of operations. We recognized swap fee income associated with these derivative contracts immediately based upon the difference in the bid/ask spread of the underlying transactions with the customer and the third party financial institution. The swap fee income is included in other noninterest income in our consolidated statements of income. At September 30, 2021 and December 31, 2020, net derivative liabilities included $21.4 million and $39.3 million, respectively, of cash collateral held by counterparties subject to master netting agreements. The notional amounts of the derivative instruments represent the contractual cash flows pertaining to the underlying agreements. These amounts are not exchanged and are not reflected in the consolidated balance sheets. The fair value of the interest rate swaps are presented at net in other assets and other liabilities when a right of offset exists, based on transactions with a single counterparty that are subject to a legally enforceable master netting agreement. The following tables present the notional and estimated fair value amount of derivative positions outstanding (in thousands): September 30, 2021 December 31, 2020 Estimated Fair Value Estimated Fair Value Notional (1) Asset Derivative Liability Derivative Notional (1) Asset Derivative Liability Derivative Derivatives designated as hedging instruments Interest rate contracts: Swaps-Cash Flow Hedge-Financial institution counterparties $ 605,000 $ 1,543 $ 10,098 $ 670,000 $ — $ 21,635 Derivatives designated as non-hedging instruments Interest rate contracts: Swaps-Financial institution counterparties 215,502 462 14,345 152,280 — 18,537 Swaps-Customer counterparties 215,502 14,345 462 152,280 18,537 — Gross derivatives 16,350 24,905 18,537 40,172 Offsetting derivative assets/liabilities (2,005) (2,005) — — Cash collateral received/posted — (21,380) — (39,270) Net derivatives included in the consolidated balance sheets (2) $ 14,345 $ 1,520 $ 18,537 $ 902 (1) Notional amounts, which represent the extent of involvement in the derivatives market, are used to determine the contractual cash flows required in accordance with the terms of the agreement. These amounts are typically not exchanged, significantly exceed amounts subject to credit or market risk and are not reflected in the consolidated balance sheets. (2) Net derivative assets are included in other assets and net derivative liabilities are included in other liabilities on the consolidated balance sheets. Included in the fair value of net derivative assets and net derivative liabilities are credit valuation adjustments reflecting counterparty credit risk and our credit risk. We had no credit exposure related to interest rate swaps with financial institutions and $14.3 million related to interest rate swaps with customers at September 30, 2021. We had no credit exposure related to interest rate swaps with financial institutions and $18.5 million related to interest rate swaps with customers at December 31, 2020. The credit risk associated with customer transactions is partially mitigated as these are generally secured by the non-cash collateral securing the underlying transaction being hedged. The summarized expected weighted average remaining maturity of the notional amount of interest rate swaps and the weighted average interest rates associated with the amounts expected to be received or paid on interest rate swap agreements are presented below (dollars in thousands). Variable rates received on fixed pay swaps are based on one-month or three-month LIBOR rates in effect at September 30, 2021 and December 31, 2020: September 30, 2021 December 31, 2020 Weighted Average Weighted Average Notional Amount Remaining Maturity Receive Rate Pay Rate Notional Amount Remaining Maturity Receive Rate Pay Swaps-Cash Flow hedge Financial institution counterparties $ 605,000 3.4 0.10 % 1.18 % $ 670,000 3.8 0.17 % 1.12 % Swaps-Non-hedging Financial institution counterparties 215,502 10.5 0.45 % 2.43 % 152,280 9.8 0.50 % 2.57 % Customer counterparties 215,502 10.5 2.43 % 0.45 % 152,280 9.8 2.57 % 0.50 %

Fair Value Measurement

Fair Value Measurement	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurement	Fair Value Measurement Fair value is the price that would be received upon the sale of an asset or paid to transfer a liability (exit price) in an orderly transaction between market participants. A fair value measurement assumes the transaction to sell the asset or transfer the liability occurs in the principal market for the asset or liability or, in the absence of a principal market, the most advantageous market for the asset or liability. The price in the principal (or most advantageous) market used to measure the fair value of the asset or liability is not adjusted for transaction costs. An orderly transaction is a transaction that assumes exposure to the market for a period prior to the measurement date to allow for marketing activities that are usual and customary for transactions involving such assets and liabilities; it is not a forced transaction. Market participants are buyers and sellers in the principal market that are (i) independent, (ii) knowledgeable, (iii) able to transact and (iv) willing to transact. Valuation techniques including the market approach, the income approach and/or the cost approach are utilized to determine fair value. Inputs to valuation techniques refer to the assumptions market participants would use in pricing the asset or liability. Valuation policies and procedures are determined by our investment department and reported to our ALCO for review. An entity must consider all aspects of nonperforming risk, including the entity’s own credit standing, when measuring fair value of a liability. Inputs may be observable, meaning those that reflect the assumptions market participants would use in pricing the asset or liability developed based on market data obtained from independent sources, or unobservable, meaning those that reflect the reporting entity’s own assumptions about the assumptions market participants would use in pricing the asset or liability developed based on the best information available in the circumstances. A fair value hierarchy for valuation inputs 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. Certain financial assets are measured at fair value in accordance with GAAP. Adjustments to the fair value of these assets usually result from the application of fair value accounting or write-downs of individual assets. A description of the valuation methodologies used for assets and liabilities measured at fair value, as well as the general classification of such instruments pursuant to the valuation hierarchy, is set forth below. Securities AFS and Equity Investments with readily determinable fair values – U.S. Treasury securities and equity investments with readily determinable fair values are reported at fair value utilizing Level 1 inputs. Other securities classified as AFS are reported at fair value utilizing Level 2 inputs. For these securities, we obtain fair value measurements from independent pricing services and obtain an understanding of the pricing methodologies used by these independent pricing services. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things, as stated in the pricing methodologies of the independent pricing services. We review and validate the prices supplied by the independent pricing services for reasonableness by comparison to prices obtained from, in some cases, two additional third-party sources. For securities where prices are outside a reasonable range, we further review those securities, based on internal ALCO approved procedures, to determine what a reasonable fair value measurement is for those securities, given available data. Derivatives – Derivatives are reported at fair value utilizing Level 2 inputs. We obtain fair value measurements from two sources including an independent pricing service and the counterparty to the derivatives designated as hedges. The fair value measurements consider observable data that may include dealer quotes, market spreads, the U.S. Treasury yield curve, live trading levels, trade execution data, credit information and the derivatives’ terms and conditions, among other things. We review the prices supplied by the sources for reasonableness. In addition, we obtain a basic understanding of their underlying pricing methodology. We validate prices supplied by the sources by comparison to one another. Certain nonfinancial assets and nonfinancial liabilities measured at fair value on a recurring basis include reporting units measured at fair value and tested for goodwill impairment. Certain financial assets and financial liabilities are measured at fair value on a nonrecurring basis, which means that the instruments are not measured at fair value on an ongoing basis but are subject to fair value adjustments in certain circumstances (for example, when there is evidence of impairment). Financial assets and financial liabilities measured at fair value on a nonrecurring basis included foreclosed assets and collateral-dependent loans at September 30, 2021 and December 31, 2020. Foreclosed Assets – Foreclosed assets are initially recorded at fair value less costs to sell. The fair value measurements of foreclosed assets can include Level 2 measurement inputs such as real estate appraisals and comparable real estate sales information, in conjunction with Level 3 measurement inputs such as cash flow projections, qualitative adjustments and sales cost estimates. As a result, the categorization of foreclosed assets is Level 3 of the fair value hierarchy. In connection with the measurement and initial recognition of certain foreclosed assets, we may recognize charge-offs through the allowance for credit losses. Collateral-Dependent Loans (Impaired loans prior to the adoption of ASU 2016-13) – Certain loans may be reported at the fair value of the underlying collateral if repayment is expected substantially from the operation or sale of the collateral. Collateral values are estimated using Level 3 inputs based on customized discounting criteria or appraisals. At September 30, 2021 and December 31, 2020, the impact of the fair value of collateral-dependent loans was reflected in our allowance for loan losses. The fair value estimate of financial instruments for which quoted market prices are unavailable is dependent upon the assumptions used. Consequently, those estimates cannot be substantiated by comparison to independent markets and, in many cases, could not be realized in immediate settlement of the instruments. Accordingly, the aggregate fair value amounts presented in the fair value tables do not necessarily represent their underlying value. The following tables summarize assets measured at fair value on a recurring and nonrecurring basis segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value (in thousands): Fair Value Measurements at the End of the Reporting Period Using September 30, 2021 Carrying Amount Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Recurring fair value measurements Investment securities: U.S. Treasury $ 43,547 $ 43,547 $ — $ — State and political subdivisions 1,967,477 — 1,967,477 — Corporate bonds and other 119,699 — 119,699 — MBS: (1) Residential 514,078 — 514,078 — Commercial 108,303 — 108,303 — Equity investments: Equity investments 5,976 5,976 — — Derivative assets: Interest rate swaps 16,350 — 16,350 — Total asset recurring fair value measurements $ 2,775,430 $ 49,523 $ 2,725,907 $ — Derivative liabilities: Interest rate swaps $ 24,905 $ — $ 24,905 $ — Total liability recurring fair value measurements $ 24,905 $ — $ 24,905 $ — Nonrecurring fair value measurements Foreclosed assets $ 40 $ — $ — $ 40 Collateral-dependent loans (2) 8,579 — — 8,579 Total asset nonrecurring fair value measurements $ 8,619 $ — $ — $ 8,619 Fair Value Measurements at the End of the Reporting Period Using December 31, 2020 Carrying Amount Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Recurring fair value measurements Investment securities: State and political subdivisions $ 1,580,594 $ — $ 1,580,594 $ — Corporate bonds and other 78,255 — 78,255 — MBS: (1) Residential 810,010 — 810,010 — Commercial 118,446 — 118,446 — Equity investments: Equity investments 6,094 6,094 — — Derivative assets: Interest rate swaps 18,537 — 18,537 — Total asset recurring fair value measurements $ 2,611,936 $ 6,094 $ 2,605,842 $ — Derivative liabilities: Interest rate swaps $ 40,172 $ — $ 40,172 $ — Total liability recurring fair value measurements $ 40,172 $ — $ 40,172 $ — Nonrecurring fair value measurements Foreclosed assets $ 120 $ — $ — $ 120 Collateral-dependent loans (2) 10,653 — — 10,653 Total asset nonrecurring fair value measurements $ 10,773 $ — $ — $ 10,773 (1) All MBS are issued and/or guaranteed by U.S. government agencies or U.S. GSEs. (2) Consists of individually evaluated loans. Loans for which the fair value of the collateral and commercial real estate fair value of the properties is less than cost basis are presented net of allowance. Losses on these loans represent charge-offs which are netted against the allowance for loan losses. Disclosure of fair value information about financial instruments, whether or not recognized in the balance sheet, is required when it is practicable to estimate that value. In cases where quoted market prices are not available, fair values are based on estimates using present value or other estimation techniques. Those techniques are significantly affected by the assumptions used, including the discount rate and estimates of future cash flows. Such techniques and assumptions, as they apply to individual categories of our financial instruments, are as follows: Cash and cash equivalents – The carrying amount for cash and cash equivalents is a reasonable estimate of those assets’ fair value. Investment and MBS HTM – Fair values for these securities are based on quoted market prices, where available. If quoted market prices are not available, fair values are based on quoted market prices for similar securities or estimates from independent pricing services. FHLB stock – The carrying amount of FHLB stock is a reasonable estimate of the fair value of those assets. Equity investments – The carrying value of equity investments without readily determinable fair values are measured at cost less impairment, if any, adjusted for observable price changes for an identical or similar investment of the same issuer. This carrying value is a reasonable estimate of the fair value of those assets. Loans receivable – We estimate the fair value of our loan portfolio to an exit price notion with adjustments for liquidity, credit and prepayment factors. Nonperforming loans continue to be estimated using discounted cash flow analyses or the underlying value of the collateral where applicable. Loans held for sale – The fair value of loans held for sale is determined based on expected proceeds, which are based on sales contracts and commitments. Deposit liabilities – The fair value of demand deposits, savings accounts and certain money market deposits is the amount on demand at the reporting date, which is the carrying value. Fair values for fixed rate CDs are estimated using a discounted cash flow calculation that applies interest rates currently being offered for deposits of similar remaining maturities. Other borrowings – Federal funds purchased generally have original terms to maturity of one day and repurchase agreements generally have terms of less than one year, and therefore both are considered short-term borrowings. Consequently, their carrying value is a reasonable estimate of fair value. FHLB borrowings – The fair value of these borrowings is estimated by discounting the future cash flows using rates at which borrowings would be made to borrowers with similar credit ratings and for the same remaining maturities. Subordinated notes – The fair value of the subordinated notes is estimated by discounting future cash flows using estimated rates at which long-term debt would be made to borrowers with similar credit ratings and for the remaining maturities. Trust preferred subordinated debentures – The fair value of the long-term debt is estimated by discounting future cash flows using estimated rates at which long-term debt would be made to borrowers with similar credit ratings and for the remaining maturities. The following tables present our financial assets and financial liabilities measured on a nonrecurring basis at both their respective carrying amounts and estimated fair value (in thousands): Estimated Fair Value September 30, 2021 Carrying Total Level 1 Level 2 Level 3 Financial assets: Cash and cash equivalents $ 87,133 $ 87,133 $ 87,133 $ — $ — Investment securities: HTM, at carrying value 788 791 — 791 — MBS: HTM, at carrying value 91,691 97,244 — 97,244 — FHLB stock, at cost 27,248 27,248 — 27,248 — Equity investments 5,818 5,818 — 5,818 — Loans, net of allowance for loan losses 3,609,563 3,755,534 — — 3,755,534 Loans held for sale 1,131 1,131 — 1,131 — Financial liabilities: Deposits $ 5,331,655 $ 5,333,064 $ — $ 5,333,064 $ — Other borrowings 20,724 20,724 — 20,724 — FHLB borrowings 659,204 668,232 — 668,232 — Subordinated notes, net of unamortized debt issuance costs 98,500 98,722 — 98,722 — Trust preferred subordinated debentures, net of unamortized debt issuance costs 60,259 48,436 — 48,436 — Estimated Fair Value December 31, 2020 Carrying Total Level 1 Level 2 Level 3 Financial assets: Cash and cash equivalents $ 108,408 $ 108,408 $ 108,408 $ — $ — Investment securities: HTM, at carrying value 907 920 — 920 — Mortgage-backed securities: HTM, at carrying value 108,091 117,278 — 117,278 — FHLB stock, at cost 25,259 25,259 — 25,259 — Equity investments 5,811 5,811 — 5,811 — Loans, net of allowance for loan losses 3,608,773 3,784,291 — — 3,784,291 Loans held for sale 3,695 3,695 — 3,695 — Financial liabilities: Deposits $ 4,932,322 $ 4,936,188 $ — $ 4,936,188 $ — Other borrowings 23,172 23,172 — 23,172 — FHLB borrowings 832,527 854,865 — 854,865 — Subordinated notes, net of unamortized debt issuance costs 197,251 198,391 — 198,391 — Trust preferred subordinated debentures, net of unamortized debt issuance costs 60,255 51,993 — 51,993 —

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The income tax expense included in the accompanying consolidated statements of income consists of the following (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Current income tax expense $ 3,387 $ 3,133 $ 9,002 $ 11,376 Deferred income tax expense (benefit) 1,590 650 3,612 (4,305) Income tax expense $ 4,977 $ 3,783 $ 12,614 $ 7,071 The net deferred tax liability totaled $12.5 million at September 30, 2021 and $15.5 million at December 31, 2020. No valuation allowance was recorded at September 30, 2021 or December 31, 2020, as management believes it is more likely than not that all of the deferred tax asset items will be realized in future years. Unrecognized tax benefits were not material at September 30, 2021 or December 31, 2020.

Off-Balance-Sheet Arrangements,

Off-Balance-Sheet Arrangements, Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Off-Balance-Sheet Arrangements, Commitments and Contingencies	Off-Balance-Sheet Arrangements, Commitments and Contingencies Financial Instruments with Off-Balance-Sheet Risk . In the normal course of business, we are a party to certain financial instruments with off-balance-sheet risk to meet the financing needs of our customers. These off-balance-sheet instruments include commitments to extend credit and standby letters of credit. These instruments involve, to varying degrees, elements of credit and interest rate risk in excess of the amount reflected in the financial statements. The contract or notional amounts of these instruments reflect the extent of involvement and exposure to credit loss that we have in these particular classes of financial instruments. The allowance for credit losses on these off-balance-sheet credit exposures is calculated using the same methodology as loans including a conversion or usage factor to anticipate ultimate exposure and expected losses and is included in other liabilities on our consolidated balance sheets. Allowance for off-balance-sheet credit exposures were as follows (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Balance at beginning of period $ 3,773 $ 6,365 $ 6,386 $ 1,455 Impact of CECL adoption — — — 4,840 Provision for (reversal of) off-balance-sheet credit exposures (683) (345) (3,296) (275) Balance at end of period $ 3,090 $ 6,020 $ 3,090 $ 6,020 Contractual commitments to extend credit are agreements to lend to a customer provided the terms established in the contract are met. Commitments to extend credit generally have fixed expiration dates and may require the payment of fees. Since some commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. Standby letters of credit are conditional commitments issued to guarantee the performance of a customer to a third party. These guarantees are primarily issued to support public and private borrowing arrangements. The credit risk involved in issuing letters of credit is essentially the same as that involved in commitments to extend credit and similarly do not necessarily represent future cash obligations. Financial instruments with off-balance-sheet risk were as follows (in thousands): September 30, 2021 December 31, 2020 Commitments to extend credit $ 954,258 $ 793,138 Standby letters of credit 10,812 13,658 Total $ 965,070 $ 806,796 We apply the same credit policies in making commitments to extend credit and standby letters of credit as we do for on-balance-sheet instruments. We evaluate each customer’s creditworthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary, upon extension of credit is based on management’s credit evaluation of the borrower. Collateral held varies but may include cash or cash equivalents, negotiable instruments, real estate, accounts receivable, inventory, oil, gas and mineral interests, property, plant and equipment. Leases . During the three and nine months ended September 30, 2021, there were $240,000 and $1.3 million, respectively, of operating lease ROU assets obtained in exchange for new operating lease liabilities, primarily due to one lease that commenced in January 2021 with an initial ROU asset of $1.1 million. During the three months ended September 30, 2020, there was a reduction to operating lease ROU assets obtained in exchange for operating lease liabilities of $89,000 due to a lease amendment that granted additional lease incentives. During the nine months ended September 30, 2020, there were $7.9 million of operating lease ROU assets obtained in exchange for new operating lease liabilities, primarily due to one lease that commenced in May 2020 with an initial ROU asset of $6.6 million. Securities . In the normal course of business we buy and sell securities. At September 30, 2021, there were $4.4 million of unsettled trades to purchase securities and no unsettled trades to sell securities. At December 31, 2020, there were no unsettled trades to purchase securities and no unsettled trades to sell securities. Deposits . There were no unsettled issuances of brokered CDs at September 30, 2021 or December 31, 2020. Litigation . We are involved with various litigation in the normal course of business. Management, after consulting with our legal counsel, believes that any liability resulting from litigation will not have a material effect on our financial position, results of operations or liquidity.

Summary of Significant Accoun_2

Summary of Significant Accounting and Reporting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation In this report, the words “the Company,” “we,” “us,” and “our” refer to the combined entities of Southside Bancshares, Inc. and its subsidiaries, including Southside Bank. The words “Southside” and “Southside Bancshares” refer to Southside Bancshares, Inc. The words “Southside Bank” and “the Bank” refer to Southside Bank. The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. GAAP for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, not all information required by GAAP for complete financial statements is included in these interim statements. In the opinion of management, all adjustments necessary for a fair presentation of such financial statements have been included. Such adjustments consisted only of normal recurring items. The preparation of these consolidated financial statements in accordance with GAAP requires the use of management’s estimates. These estimates are subjective in nature and involve matters of judgment. Actual amounts could differ from these estimates.
Accounting Changes and Reclassifications and Accounting Pronouncements	Accounting Changes and Reclassifications Certain prior period amounts may be reclassified to conform to current year presentation. Accounting Pronouncements In March 2020, the FASB issued ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting.” ASU 2020-04 is intended to provide relief for companies preparing for discontinuation of interest rates based on LIBOR. The ASU provides optional expedients and exceptions for applying GAAP to contract modifications and hedging relationships, subject to meeting certain criteria, that reference LIBOR or other reference rates expected to be discontinued. ASU 2020-04 also provides for a one-time sale and/or transfer to AFS or trading to be made for HTM debt securities that both reference an eligible reference rate and were classified as HTM before January 1, 2020. ASU 2020-04 was effective for all entities as of March 12, 2020 and through December 31, 2022. Companies can apply the ASU as of the beginning of the interim period that includes March 12, 2020 or any date thereafter. The guidance requires companies to apply the guidance prospectively to contract modifications and hedging relationships while the one-time election to sell and/or transfer debt securities classified as HTM may be made any time after March 12, 2020. We have established an officer level committee to guide our transition from LIBOR and have begun efforts to transition to alternative rates consistent with industry timelines. We have identified products that utilize LIBOR and are implementing enhanced fallback language to facilitate the transition to alternative reference rates. We are evaluating existing systems and have begun offering new rates on a limited basis. ASU 2020-04 is not expected to have a material impact on our consolidated financial statements.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Earnings per share on a basic and diluted basis	Earnings per share on a basic and diluted basis are calculated as follows (in thousands, except per share amounts): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Basic and Diluted Earnings: Net income $ 29,306 $ 27,074 $ 84,714 $ 52,581 Basic weighted-average shares outstanding 32,465 33,047 32,641 33,250 Add: Stock awards 91 51 118 81 Diluted weighted-average shares outstanding 32,556 33,098 32,759 33,331 Basic earnings per share: Net income $ 0.90 $ 0.82 $ 2.60 $ 1.58 Diluted earnings per share: Net income $ 0.90 $ 0.82 $ 2.59 $ 1.58

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2021
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of accumulated other comprehensive income (loss) by component	The changes in accumulated other comprehensive income (loss) by component are as follows (in thousands): Three Months Ended September 30, 2021 Pension Plans Unrealized Gains (Losses) on Securities Unrealized Gains (Losses) on Derivatives Net Prior Service (Cost) Credit Net Gain (Loss) Total Beginning balance, net of tax $ 102,628 $ (8,334) $ 149 $ (29,556) $ 64,887 Other comprehensive income (loss): Other comprehensive (loss) income before reclassifications (27,714) 377 — — (27,337) Reclassification adjustments included in net income (1,069) 1,617 — 316 864 Income tax benefit (expense) 6,045 (418) — (67) 5,560 Net current-period other comprehensive (loss) income, net of tax (22,738) 1,576 — 249 (20,913) Ending balance, net of tax $ 79,890 $ (6,758) $ 149 $ (29,307) $ 43,974 Nine Months Ended September 30, 2021 Pension Plans Unrealized Gains (Losses) on Securities Unrealized Gains (Losses) on Derivatives Net Prior Net Gain (Loss) Total Beginning balance, net of tax $ 116,078 $ (17,091) $ 149 $ (30,056) $ 69,080 Other comprehensive income (loss): Other comprehensive (loss) income before reclassifications (43,527) 8,296 — — (35,231) Reclassification adjustments included in net income (2,281) 4,784 — 948 3,451 Income tax benefit (expense) 9,620 (2,747) — (199) 6,674 Net current-period other comprehensive (loss) income, net of tax (36,188) 10,333 — 749 (25,106) Ending balance, net of tax $ 79,890 $ (6,758) $ 149 $ (29,307) $ 43,974 Three Months Ended September 30, 2020 Pension Plans Unrealized Gains (Losses) on Securities Unrealized Gains (Losses) on Derivatives Net Prior Service (Cost) Credit Net Gain (Loss) Total Beginning balance, net of tax $ 100,790 $ (20,904) $ (20) $ (36,855) $ 43,011 Other comprehensive income (loss): Other comprehensive income (loss) before reclassifications 1,601 (197) — — 1,404 Reclassification adjustments included in net income 316 1,587 (2) 821 2,722 Income tax expense (403) (292) — (171) (866) Net current-period other comprehensive income (loss), net of tax 1,514 1,098 (2) 650 3,260 Ending balance, net of tax $ 102,304 $ (19,806) $ (22) $ (36,205) $ 46,271 Nine Months Ended September 30, 2020 Pension Plans Unrealized Gains (Losses) on Securities Unrealized Gains (Losses) on Derivatives Net Prior Service (Cost) Credit Net Gain (Loss) Total Beginning balance, net of tax $ 38,038 $ (1,672) $ (145) $ (31,985) $ 4,236 Other comprehensive income (loss): Other comprehensive income (loss) before reclassifications 88,900 (25,236) 163 (7,558) 56,269 Reclassification adjustments included in net income (7,551) 2,283 (6) 2,213 (3,061) Income tax (expense) benefit (17,083) 4,819 (34) 1,125 (11,173) Net current-period other comprehensive income (loss), net of tax 64,266 (18,134) 123 (4,220) 42,035 Ending balance, net of tax $ 102,304 $ (19,806) $ (22) $ (36,205) $ 46,271
Reclassifications out of accumulated other comprehensive income	The reclassification adjustments out of accumulated other comprehensive income (loss) included in net income are presented below (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Unrealized gains and losses on securities transferred: Amortization of unrealized gains and losses (1) $ (312) $ (394) $ (1,118) $ (730) Tax benefit 66 82 235 153 Net of tax (246) (312) (883) (577) Unrealized gains and losses on available for sale securities: Realized net gain on sale of securities (2) 1,381 78 3,399 8,281 Tax expense (290) (16) (714) (1,739) Net of tax 1,091 62 2,685 6,542 Derivatives: Realized net loss on interest rate swap derivatives (3) (1,617) (1,593) (4,784) (2,303) Tax benefit 340 335 1,005 484 Net of tax (1,277) (1,258) (3,779) (1,819) Amortization of unrealized gains on terminated interest rate swap derivatives (3) — 6 — 20 Tax expense — (1) — (4) Net of tax — 5 — 16 Amortization of pension plan: Net actuarial loss (4) (316) (821) (948) (2,213) Prior service credit (4) — 2 — 6 Total before tax (316) (819) (948) (2,207) Tax benefit 67 172 199 463 Net of tax (249) (647) (749) (1,744) Total reclassifications for the period, net of tax $ (681) $ (2,150) $ (2,726) $ 2,418 (1) Included in interest income on the consolidated statements of income. (2) Listed as net gain on sale of securities AFS on the consolidated statements of income. (3) Included in interest expense for FHLB borrowings on the consolidated statements of income. (4) These AOCI components are included in the computation of net periodic pension cost (income) presented in “Note 8 – Employee Benefit Plans.”

Securities (Tables)

Securities (Tables)	9 Months Ended
	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Amortized cost and estimated fair value of investment and mortgage-backed securities	The amortized cost, gross unrealized gains and losses and estimated fair value of investment and mortgage-backed AFS and HTM securities as of September 30, 2021 and December 31, 2020 are reflected in the tables below (in thousands): September 30, 2021 Amortized Gross Unrealized Gross Unrealized Estimated AVAILABLE FOR SALE Cost Gains Losses Fair Value Investment securities: U.S. Treasury $ 42,806 $ 741 $ — $ 43,547 State and political subdivisions 1,890,814 83,140 6,477 1,967,477 Corporate bonds and other 117,332 2,563 196 119,699 MBS: (1) Residential 493,505 20,943 370 514,078 Commercial 105,780 2,800 277 108,303 Total $ 2,650,237 $ 110,187 $ 7,320 $ 2,753,104 HELD TO MATURITY Investment securities: State and political subdivisions $ 788 $ 3 $ — $ 791 MBS: (1) Residential 40,128 2,616 — 42,744 Commercial 51,563 2,937 — 54,500 Total $ 92,479 $ 5,556 $ — $ 98,035 December 31, 2020 Amortized Gross Unrealized Gross Unrealized Estimated AVAILABLE FOR SALE Cost Gains Losses Fair Value Investment securities: State and political subdivisions $ 1,475,030 $ 105,601 $ 37 $ 1,580,594 Corporate bonds and other 77,224 1,053 22 78,255 MBS: (1) Residential 771,409 38,674 73 810,010 Commercial 113,850 4,746 150 118,446 Total $ 2,437,513 $ 150,074 $ 282 $ 2,587,305 HELD TO MATURITY Investment securities: State and political subdivisions $ 907 $ 13 $ — $ 920 MBS: (1) Residential 47,948 4,187 — 52,135 Commercial 60,143 5,000 — 65,143 Total $ 108,998 $ 9,200 $ — $ 118,198 (1) All MBS are issued and/or guaranteed by U.S. government agencies or U.S. GSEs.
Unrealized loss on securities	The following tables represent the fair value and unrealized losses on AFS investment securities and MBS for which an allowance for credit losses has not been recorded as of September 30, 2021 and December 31, 2020, segregated by major security type and length of time in a continuous loss position (in thousands): September 30, 2021 Less Than 12 Months More Than 12 Months Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss AVAILABLE FOR SALE Investment securities: State and political subdivisions $ 396,345 $ 6,477 $ — $ — $ 396,345 $ 6,477 Corporate bonds and other 21,352 196 — — 21,352 196 MBS: Residential 15,790 370 — — 15,790 370 Commercial — — 4,602 277 4,602 277 Total $ 433,487 $ 7,043 $ 4,602 $ 277 $ 438,089 $ 7,320 December 31, 2020 Less Than 12 Months More Than 12 Months Total Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized AVAILABLE FOR SALE Investment securities: State and political subdivisions $ 17,305 $ 37 $ — $ — $ 17,305 $ 37 Corporate bonds and other 11,562 22 — — 11,562 22 MBS: Residential 6,287 73 — — 6,287 73 Commercial 4,744 150 — — 4,744 150 Total $ 39,898 $ 282 $ — $ — $ 39,898 $ 282
Interest income recognized on securities	The following table reflects interest income recognized on securities for the periods presented (in thousands): Three Months Ended 2021 2020 U.S. Treasury $ 182 $ — State and political subdivisions 12,223 9,787 Corporate bonds and other 1,097 391 MBS 4,405 7,048 Total interest income on securities $ 17,907 $ 17,226 Nine Months Ended 2021 2020 U.S. Treasury $ 388 $ — State and political subdivisions 33,568 26,281 Corporate bonds and other 2,928 568 MBS 15,140 27,626 Total interest income on securities $ 52,024 $ 54,475
Amortized cost, carrying value and fair value of securities presented by contractual maturity	The amortized cost and estimated fair value of AFS and HTM securities at September 30, 2021, are presented below by contractual maturity (in thousands): September 30, 2021 Amortized Cost Fair Value AVAILABLE FOR SALE Investment securities: Due in one year or less $ 4,495 $ 4,532 Due after one year through five years 26,705 27,841 Due after five years through ten years 175,953 180,006 Due after ten years 1,843,799 1,918,344 2,050,952 2,130,723 MBS: 599,285 622,381 Total $ 2,650,237 $ 2,753,104 September 30, 2021 Amortized Cost Fair Value HELD TO MATURITY Investment securities: Due in one year or less $ 120 $ 120 Due after one year through five years 529 531 Due after five years through ten years 139 140 Due after ten years — — 788 791 MBS: 91,691 97,244 Total $ 92,479 $ 98,035
Unrealized and realized gains (losses) recognized in net income on equity investments	The following is a summary of unrealized and realized gains and losses on equity investments recognized in other noninterest income in the consolidated statements of income during the periods presented (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Net (losses) gains recognized during the period on equity investments $ (28) $ (232) $ (118) $ (178) Less: Net gains recognized during the period on equity investments sold during the period — — — — Unrealized (losses) gains recognized during the reporting period on equity investments held at the reporting date $ (28) $ (232) $ (118) $ (178)

Loans and Allowance for Loan _2

Loans and Allowance for Loan Losses (Tables)	9 Months Ended
	Sep. 30, 2021
Receivables [Abstract]
Loans by Portfolio Segment	Loans in the accompanying consolidated balance sheets are classified as follows (in thousands): September 30, 2021 December 31, 2020 Real estate loans: Construction $ 422,095 $ 581,941 1-4 family residential 660,689 719,952 Commercial 1,605,132 1,295,746 Commercial loans 443,708 557,122 Municipal loans 427,259 409,028 Loans to individuals 88,702 93,990 Total loans 3,647,585 3,657,779 Less: Allowance for loan losses 38,022 49,006 Net loans $ 3,609,563 $ 3,608,773
Summary of loans by credit quality indicators and origination year	The following tables set forth the amortized cost basis by class of financing receivable and credit quality indicator for the periods presented (in thousands): September 30, 2021 Term Loans Amortized Cost Basis by Origination Year Revolving Loans Amortized Cost Basis Total 2021 2020 2019 2018 2017 Prior Construction real estate: Pass $ 117,946 $ 107,623 $ 56,826 $ 6,343 $ 2,209 $ 6,755 $ 124,101 $ 421,803 Pass watch — — — — — 21 — 21 Special mention — — — — — — — — Substandard — — — — — 217 — 217 Doubtful — — — 54 — — — 54 Total construction real estate $ 117,946 $ 107,623 $ 56,826 $ 6,397 $ 2,209 $ 6,993 $ 124,101 $ 422,095 1-4 family residential real estate: Pass $ 111,806 $ 134,208 $ 89,450 $ 52,699 $ 38,027 $ 226,835 $ 2,239 $ 655,264 Pass watch — — — — — 803 — 803 Special mention — — — — — 62 — 62 Substandard 9 483 54 — 430 3,227 89 4,292 Doubtful — 9 — — — 259 — 268 Total 1-4 family residential real estate $ 111,815 $ 134,700 $ 89,504 $ 52,699 $ 38,457 $ 231,186 $ 2,328 $ 660,689 Commercial real estate: Pass $ 448,184 $ 237,377 $ 317,768 $ 127,342 $ 154,680 $ 230,388 $ 6,281 $ 1,522,020 Pass watch — — 4,163 23,242 22,159 1,645 — 51,209 Special mention — 197 — — 168 1,919 — 2,284 Substandard 3,449 609 8,882 8,563 — 7,991 — 29,494 Doubtful — — — — — 125 — 125 Total commercial real estate $ 451,633 $ 238,183 $ 330,813 $ 159,147 $ 177,007 $ 242,068 $ 6,281 $ 1,605,132 Commercial loans: Pass $ 131,981 $ 78,247 $ 28,930 $ 15,234 $ 4,147 $ 6,166 $ 174,372 $ 439,077 Pass watch 39 55 504 25 — — — 623 Special mention — — 124 381 — 183 373 1,061 Substandard 91 194 379 165 20 1 1,457 2,307 Doubtful 8 25 141 386 — 80 — 640 Total commercial loans $ 132,119 $ 78,521 $ 30,078 $ 16,191 $ 4,167 $ 6,430 $ 176,202 $ 443,708 Municipal loans: Pass $ 56,206 $ 65,884 $ 63,328 $ 30,504 $ 57,665 $ 153,672 $ — $ 427,259 Pass watch — — — — — — — — Special mention — — — — — — — — Substandard — — — — — — — — Doubtful — — — — — — — — Total municipal loans $ 56,206 $ 65,884 $ 63,328 $ 30,504 $ 57,665 $ 153,672 $ — $ 427,259 Loans to individuals: Pass $ 34,329 $ 28,335 $ 14,196 $ 5,195 $ 2,188 $ 1,068 $ 3,236 $ 88,547 Pass watch — — — — — — — — Special mention — — — 40 — — — 40 Substandard — 1 27 14 22 10 1 75 Doubtful — — 1 11 10 18 — 40 Total loans to individuals $ 34,329 $ 28,336 $ 14,224 $ 5,260 $ 2,220 $ 1,096 $ 3,237 $ 88,702 Total loans $ 904,048 $ 653,247 $ 584,773 $ 270,198 $ 281,725 $ 641,445 $ 312,149 $ 3,647,585 December 31, 2020 Term Loans Amortized Cost Basis by Origination Year Revolving Loans Amortized Cost Basis Total 2020 2019 2018 2017 2016 Prior Construction real estate: Pass $ 155,693 $ 180,536 $ 76,090 $ 55,636 $ 3,191 $ 8,297 $ 101,793 $ 581,236 Pass watch — — — — 23 — — 23 Special mention — — — — — — — — Substandard — 382 62 — — 58 — 502 Doubtful — — — — — 180 — 180 Total construction real estate $ 155,693 $ 180,918 $ 76,152 $ 55,636 $ 3,214 $ 8,535 $ 101,793 $ 581,941 1-4 family residential real estate: Pass $ 154,003 $ 114,063 $ 70,621 $ 55,557 $ 57,680 $ 255,003 $ 2,833 $ 709,760 Pass watch — — — — 267 564 — 831 Special mention — — — — — 10 — 10 Substandard 1,473 — 135 427 1,588 5,134 96 8,853 Doubtful — — — 36 103 359 — 498 Total 1-4 family residential real estate $ 155,476 $ 114,063 $ 70,756 $ 56,020 $ 59,638 $ 261,070 $ 2,929 $ 719,952 Commercial real estate: Pass $ 270,087 $ 307,161 $ 143,177 $ 162,180 $ 98,828 $ 179,919 $ 6,957 $ 1,168,309 Pass watch — — 3,153 40,125 1,696 2,582 — 47,556 Special mention 4,555 33,020 7,041 140 4,531 7,850 — 57,137 Substandard 7,542 — 2,097 65 704 12,282 — 22,690 Doubtful — — — — — 54 — 54 Total commercial real estate $ 282,184 $ 340,181 $ 155,468 $ 202,510 $ 105,759 $ 202,687 $ 6,957 $ 1,295,746 Commercial loans: Pass $ 313,688 $ 47,446 $ 20,386 $ 7,505 $ 3,392 $ 6,142 $ 140,018 $ 538,577 Pass watch 2,599 1,318 2,410 1,981 — — 370 8,678 Special mention 304 809 433 39 286 265 455 2,591 Substandard 405 1,081 473 7 — — 4,417 6,383 Doubtful 310 53 475 54 1 — — 893 Total commercial loans $ 317,306 $ 50,707 $ 24,177 $ 9,586 $ 3,679 $ 6,407 $ 145,260 $ 557,122 Municipal loans: Pass $ 72,542 $ 68,132 $ 33,735 $ 61,170 $ 25,387 $ 148,062 $ — $ 409,028 Pass watch — — — — — — — — Special mention — — — — — — — — Substandard — — — — — — — — Doubtful — — — — — — — — Total municipal loans $ 72,542 $ 68,132 $ 33,735 $ 61,170 $ 25,387 $ 148,062 $ — $ 409,028 Loans to individuals: Pass $ 46,722 $ 25,302 $ 10,132 $ 4,716 $ 1,867 $ 917 $ 3,900 $ 93,556 Pass watch — — — — — — — — Special mention — — 51 — — — 4 55 Substandard 6 35 28 30 9 11 1 120 Doubtful 73 20 6 55 81 24 — 259 Total loans to individuals $ 46,801 $ 25,357 $ 10,217 $ 4,801 $ 1,957 $ 952 $ 3,905 $ 93,990 Total loans $ 1,030,002 $ 779,358 $ 370,505 $ 389,723 $ 199,634 $ 627,713 $ 260,844 $ 3,657,779
Aging of past due loans by class of loan	The following tables present the aging of the amortized cost basis in past due loans by class of loans (in thousands): September 30, 2021 30-59 Days Past Due 60-89 Days Past Due Greater than 90 Days Past Due Total Past Due Current Total Real estate loans: Construction $ 72 $ 41 $ — $ 113 $ 421,982 $ 422,095 1-4 family residential 652 691 580 1,923 658,766 660,689 Commercial 885 — — 885 1,604,247 1,605,132 Commercial loans 1,402 233 31 1,666 442,042 443,708 Municipal loans 96 — — 96 427,163 427,259 Loans to individuals 265 14 12 291 88,411 88,702 Total $ 3,372 $ 979 $ 623 $ 4,974 $ 3,642,611 $ 3,647,585 December 31, 2020 30-59 Days Past Due 60-89 Days Past Due Greater than 90 Days Total Past Due Current Total Real estate loans: Construction $ 95 $ 14 $ 444 $ 553 $ 581,388 $ 581,941 1-4 family residential 7,872 2,469 2,830 13,171 706,781 719,952 Commercial 467 315 86 868 1,294,878 1,295,746 Commercial loans 1,423 4,516 323 6,262 550,860 557,122 Municipal loans 64 — — 64 408,964 409,028 Loans to individuals 519 123 27 669 93,321 93,990 Total $ 10,440 $ 7,437 $ 3,710 $ 21,587 $ 3,636,192 $ 3,657,779
Nonperforming assets by asset class	The following table sets forth the amortized cost basis of nonperforming assets for the periods presented (in thousands): September 30, 2021 December 31, 2020 Nonaccrual loans: Real estate loans: Construction $ 63 $ 640 1-4 family residential 1,432 3,922 Commercial 796 1,269 Commercial loans 674 1,592 Loans to individuals 48 291 Total nonaccrual loans (1) 3,013 7,714 Accruing loans past due more than 90 days — — TDR loans 9,371 9,646 OREO 25 106 Repossessed assets 15 14 Total nonperforming assets $ 12,424 $ 17,480 (1) Includes $1.1 million and $976,000 of restructured loans as of September 30, 2021 and December 31, 2020, respectively.
Troubled debt restructurings	The following tables set forth the recorded balance of loans considered to be TDRs that were restructured and the type of concession by class of loans during the periods presented (dollars in thousands): Three Months Ended September 30, 2021 Extend Amortization Period Interest Rate Reductions Combination Total Modifications Number of Loans Real estate loans: 1-4 family residential $ — $ — $ 219 $ 219 3 Commercial — — 453 453 1 Total $ — $ — $ 672 $ 672 4 Nine Months Ended September 30, 2021 Extend Amortization Period Interest Rate Reductions Combination Total Modifications Number of Loans Real estate loans: 1-4 family residential $ — $ — $ 344 $ 344 5 Commercial — — 453 453 1 Commercial loans — 16 94 110 3 Total $ — $ 16 $ 891 $ 907 9 Nine Months Ended September 30, 2020 Extend Amortization Period Interest Rate Reductions Combination Total Modifications Number of Loans Real estate loans: Commercial $ — $ — $ 58 $ 58 1 Commercial loans — — 117 117 3 Total $ — $ — $ 175 $ 175 4
Allowance for loan losses activity by portfolio segment	The following tables detail activity in the allowance for loan losses by portfolio segment for the periods presented (in thousands): Three Months Ended September 30, 2021 Real Estate Construction 1-4 Family Residential Commercial Commercial Loans Municipal Loans Loans to Individuals Total Balance at beginning of period $ 8,018 $ 2,520 $ 28,930 $ 3,097 $ 47 $ 301 $ 42,913 Loans charged-off — (35) — (508) — (397) (940) Recoveries of loans charged-off 1 4 12 74 — 346 437 Net loans (charged-off) recovered 1 (31) 12 (434) — (51) (503) Provision for (reversal of) loan losses (3,036) (543) (684) (103) (1) (21) (4,388) Balance at end of period $ 4,983 $ 1,946 $ 28,258 $ 2,560 $ 46 $ 229 $ 38,022 Nine Months Ended September 30, 2021 Real Estate Construction 1-4 Family Residential Commercial Commercial Loans Municipal Loans Loans to Individuals Total Balance at beginning of period $ 6,490 $ 2,270 $ 35,709 $ 4,107 $ 46 $ 384 $ 49,006 Loans charged-off — (136) — (943) — (1,183) (2,262) Recoveries of loans charged-off 2 71 13 535 — 904 1,525 Net loans (charged-off) recovered 2 (65) 13 (408) — (279) (737) Provision for (reversal of) loan losses (1,509) (259) (7,464) (1,139) — 124 (10,247) Balance at end of period $ 4,983 $ 1,946 $ 28,258 $ 2,560 $ 46 $ 229 $ 38,022 Three Months Ended September 30, 2020 Real Estate Construction 1-4 Family Residential Commercial Commercial Loans Municipal Loans Loans to Individuals Total Balance at beginning of period $ 8,500 $ 2,702 $ 43,785 $ 4,221 $ 47 $ 613 $ 59,868 Loans charged-off (6) (18) (12) (279) — (403) (718) Recoveries of loans charged-off — 9 13 61 — 278 361 Net loans (charged-off) recovered (6) (9) 1 (218) — (125) (357) Provision for (reversal of) loan losses (2,868) (58) (2,001) 489 (1) 38 (4,401) Balance at end of period $ 5,626 $ 2,635 $ 41,785 $ 4,492 $ 46 $ 526 $ 55,110 Nine Months Ended September 30, 2020 Real Estate Construction 1-4 Family Residential Commercial Commercial Loans Municipal Loans Loans to Individuals Total Balance at beginning of period $ 3,539 $ 3,833 $ 9,572 $ 6,351 $ 570 $ 932 $ 24,797 Impact of CECL adoption - cumulative effect adjustment 2,968 (1,447) 7,730 (3,532) (522) (125) 5,072 Impact of CECL adoption - purchased loans with credit deterioration (15) (6) 333 (22) — (59) 231 Loans charged-off (39) (74) (33) (800) — (1,313) (2,259) Recoveries of loans charged-off 11 29 94 191 — 923 1,248 Net loans (charged-off) recovered (28) (45) 61 (609) — (390) (1,011) Provision for (reversal of) loan losses (1) (838) 300 24,089 2,304 (2) 168 26,021 Balance at end of period $ 5,626 $ 2,635 $ 41,785 $ 4,492 $ 46 $ 526 $ 55,110 (1) The increase in the provision for credit losses during the nine months ended September 30, 2020 was primarily due to the economic impact of COVID-19 on macroeconomic factors used in the CECL model.

Borrowing Arrangements (Tables)

Borrowing Arrangements (Tables)	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Schedule of Debt	Information related to borrowings is provided in the table below (dollars in thousands): September 30, 2021 December 31, 2020 Other borrowings: Balance at end of period $ 20,724 $ 23,172 Average amount outstanding during the period (1) 22,387 91,940 Maximum amount outstanding during the period (2) 24,549 219,259 Weighted average interest rate during the period (3) 0.2 % 0.4 % Interest rate at end of period (4) 0.2 % 0.1 % FHLB borrowings: Balance at end of period $ 659,204 $ 832,527 Average amount outstanding during the period (1) 684,280 1,032,269 Maximum amount outstanding during the period (2) 723,584 1,274,370 Weighted average interest rate during the period (3) 1.1 % 1.1 % Interest rate at end of period (5) 1.1 % 1.0 % (1) The average amount outstanding during the period was computed by dividing the total daily outstanding principal balances by the number of days in the period. (2) The maximum amount outstanding at any month-end during the period. (3) The weighted average interest rate during the period was computed by dividing the actual interest expense (annualized for interim periods) by the average amount outstanding during the period. The weighted average interest rate on the FHLB borrowings includes the effect of interest rate swaps. (4) Stated rate. (5) The interest rate on the FHLB borrowings includes the effect of interest rate swaps.
Schedule of Maturities of Borrowings	Maturities of the obligations associated with our borrowing arrangements based on scheduled repayments at September 30, 2021 are as follows (in thousands): Payments Due by Period Less than 1-2 Years 2-3 Years 3-4 Years 4-5 Years Thereafter Total Other borrowings $ 20,724 $ — $ — $ — $ — $ — $ 20,724 FHLB borrowings 655,673 702 733 764 582 750 659,204 Total obligations $ 676,397 $ 702 $ 733 $ 764 $ 582 $ 750 $ 679,928

Long-term Debt (Tables)

Long-term Debt (Tables)	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	Information related to our long-term debt is summarized as follows for the periods presented (in thousands): September 30, 2021 December 31, 2020 Subordinated notes: (1) 3.875% Subordinated notes, net of unamortized debt issuance costs (2) $ 98,500 $ 98,497 5.50% Subordinated notes, net of unamortized debt issuance costs (3) — 98,754 Total Subordinated notes 98,500 197,251 Trust preferred subordinated debentures: (4) Southside Statutory Trust III, net of unamortized debt issuance costs (5) 20,567 20,563 Southside Statutory Trust IV 23,196 23,196 Southside Statutory Trust V 12,887 12,887 Magnolia Trust Company I 3,609 3,609 Total Trust preferred subordinated debentures 60,259 60,255 Total Long-term debt $ 158,759 $ 257,506 (1) This debt consists of subordinated notes with a remaining maturity greater than one year that qualify under the risk-based capital guidelines as Tier 2 capital, subject to certain limitations. (2) The unamortized discount and debt issuance costs reflected in the carrying amount of the subordinated notes totaled approximately $1.5 million at September 30, 2021 and December 31, 2020. (3) The unamortized discount and debt issuance costs reflected in the carrying amount of the subordinated notes totaled approximately $1.2 million at December 31, 2020. (4) This debt consists of trust preferred securities that qualify under the risk-based capital guidelines as Tier 1 capital, subject to certain limitations.
Schedule of Subordinated Borrowing	As of September 30, 2021, the details of the subordinated notes and the trust preferred subordinated debentures are summarized below (dollars in thousands): Date Issued Amount Issued Fixed or Floating Rate Interest Rate Maturity Date 3.875% Subordinated Notes November 6, 2020 $ 100,000 Fixed-to-Floating 3.875% November 15, 2030 Southside Statutory Trust III September 4, 2003 $ 20,619 Floating 3 month LIBOR + 2.94% September 4, 2033 Southside Statutory Trust IV August 8, 2007 $ 23,196 Floating 3 month LIBOR + 1.30% October 30, 2037 Southside Statutory Trust V August 10, 2007 $ 12,887 Floating 3 month LIBOR + 2.25% September 15, 2037 Magnolia Trust Company I (1) May 20, 2005 $ 3,609 Floating 3 month LIBOR + 1.80% November 23, 2035

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2021
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
The components of net periodic benefit cost	The components of net periodic benefit cost (income) related to our employee benefit plans are as follows (in thousands): Three Months Ended September 30, Defined Benefit Defined Benefit Restoration 2021 2020 2021 2020 2021 2020 Service cost $ — $ 483 $ — $ — $ — $ 149 Interest cost 642 672 23 41 130 126 Expected return on assets (1,355) (1,344) (53) (75) — — Net loss amortization 251 694 1 2 64 125 Prior service (credit) cost amortization — (4) — — — 2 Net periodic benefit (income) cost $ (462) $ 501 $ (29) $ (32) $ 194 $ 402 Nine Months Ended September 30, Defined Benefit Defined Benefit Restoration 2021 2020 2021 2020 2021 2020 Service cost $ — $ 1,311 $ — $ — $ — $ 280 Interest cost 1,927 2,359 69 122 390 442 Expected return on assets (4,065) (4,332) (158) (226) — — Net loss amortization 752 1,780 4 7 192 426 Prior service (credit) cost amortization — (11) — — — 5 Loss due to curtailment — 151 — — — 12 Net periodic benefit (income) cost $ (1,386) $ 1,258 $ (85) $ (97) $ 582 $ 1,165

Derivative Financial Instrume_2

Derivative Financial Instruments and Hedging Activities (Tables)	9 Months Ended
	Sep. 30, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	The following tables present the notional and estimated fair value amount of derivative positions outstanding (in thousands): September 30, 2021 December 31, 2020 Estimated Fair Value Estimated Fair Value Notional (1) Asset Derivative Liability Derivative Notional (1) Asset Derivative Liability Derivative Derivatives designated as hedging instruments Interest rate contracts: Swaps-Cash Flow Hedge-Financial institution counterparties $ 605,000 $ 1,543 $ 10,098 $ 670,000 $ — $ 21,635 Derivatives designated as non-hedging instruments Interest rate contracts: Swaps-Financial institution counterparties 215,502 462 14,345 152,280 — 18,537 Swaps-Customer counterparties 215,502 14,345 462 152,280 18,537 — Gross derivatives 16,350 24,905 18,537 40,172 Offsetting derivative assets/liabilities (2,005) (2,005) — — Cash collateral received/posted — (21,380) — (39,270) Net derivatives included in the consolidated balance sheets (2) $ 14,345 $ 1,520 $ 18,537 $ 902 (1) Notional amounts, which represent the extent of involvement in the derivatives market, are used to determine the contractual cash flows required in accordance with the terms of the agreement. These amounts are typically not exchanged, significantly exceed amounts subject to credit or market risk and are not reflected in the consolidated balance sheets.
Weighted Average Maturity And Interest Rates On Risk Management Interest Rate Swaps	The summarized expected weighted average remaining maturity of the notional amount of interest rate swaps and the weighted average interest rates associated with the amounts expected to be received or paid on interest rate swap agreements are presented below (dollars in thousands). Variable rates received on fixed pay swaps are based on one-month or three-month LIBOR rates in effect at September 30, 2021 and December 31, 2020: September 30, 2021 December 31, 2020 Weighted Average Weighted Average Notional Amount Remaining Maturity Receive Rate Pay Rate Notional Amount Remaining Maturity Receive Rate Pay Swaps-Cash Flow hedge Financial institution counterparties $ 605,000 3.4 0.10 % 1.18 % $ 670,000 3.8 0.17 % 1.12 % Swaps-Non-hedging Financial institution counterparties 215,502 10.5 0.45 % 2.43 % 152,280 9.8 0.50 % 2.57 % Customer counterparties 215,502 10.5 2.43 % 0.45 % 152,280 9.8 2.57 % 0.50 %

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Summary of fair value measurement on recurring and nonrecurring basis segregated by level of valuation inputs within fair value hierarchy utilized to measure fair value	The following tables summarize assets measured at fair value on a recurring and nonrecurring basis segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value (in thousands): Fair Value Measurements at the End of the Reporting Period Using September 30, 2021 Carrying Amount Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Recurring fair value measurements Investment securities: U.S. Treasury $ 43,547 $ 43,547 $ — $ — State and political subdivisions 1,967,477 — 1,967,477 — Corporate bonds and other 119,699 — 119,699 — MBS: (1) Residential 514,078 — 514,078 — Commercial 108,303 — 108,303 — Equity investments: Equity investments 5,976 5,976 — — Derivative assets: Interest rate swaps 16,350 — 16,350 — Total asset recurring fair value measurements $ 2,775,430 $ 49,523 $ 2,725,907 $ — Derivative liabilities: Interest rate swaps $ 24,905 $ — $ 24,905 $ — Total liability recurring fair value measurements $ 24,905 $ — $ 24,905 $ — Nonrecurring fair value measurements Foreclosed assets $ 40 $ — $ — $ 40 Collateral-dependent loans (2) 8,579 — — 8,579 Total asset nonrecurring fair value measurements $ 8,619 $ — $ — $ 8,619 Fair Value Measurements at the End of the Reporting Period Using December 31, 2020 Carrying Amount Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Recurring fair value measurements Investment securities: State and political subdivisions $ 1,580,594 $ — $ 1,580,594 $ — Corporate bonds and other 78,255 — 78,255 — MBS: (1) Residential 810,010 — 810,010 — Commercial 118,446 — 118,446 — Equity investments: Equity investments 6,094 6,094 — — Derivative assets: Interest rate swaps 18,537 — 18,537 — Total asset recurring fair value measurements $ 2,611,936 $ 6,094 $ 2,605,842 $ — Derivative liabilities: Interest rate swaps $ 40,172 $ — $ 40,172 $ — Total liability recurring fair value measurements $ 40,172 $ — $ 40,172 $ — Nonrecurring fair value measurements Foreclosed assets $ 120 $ — $ — $ 120 Collateral-dependent loans (2) 10,653 — — 10,653 Total asset nonrecurring fair value measurements $ 10,773 $ — $ — $ 10,773 (1) All MBS are issued and/or guaranteed by U.S. government agencies or U.S. GSEs. (2) Consists of individually evaluated loans. Loans for which the fair value of the collateral and commercial real estate fair value of the properties is less than cost basis are presented net of allowance. Losses on these loans represent charge-offs which are netted against the allowance for loan losses.
Financial assets, financial liabilities, and unrecognized financial instruments at carrying amount and fair value	The following tables present our financial assets and financial liabilities measured on a nonrecurring basis at both their respective carrying amounts and estimated fair value (in thousands): Estimated Fair Value September 30, 2021 Carrying Total Level 1 Level 2 Level 3 Financial assets: Cash and cash equivalents $ 87,133 $ 87,133 $ 87,133 $ — $ — Investment securities: HTM, at carrying value 788 791 — 791 — MBS: HTM, at carrying value 91,691 97,244 — 97,244 — FHLB stock, at cost 27,248 27,248 — 27,248 — Equity investments 5,818 5,818 — 5,818 — Loans, net of allowance for loan losses 3,609,563 3,755,534 — — 3,755,534 Loans held for sale 1,131 1,131 — 1,131 — Financial liabilities: Deposits $ 5,331,655 $ 5,333,064 $ — $ 5,333,064 $ — Other borrowings 20,724 20,724 — 20,724 — FHLB borrowings 659,204 668,232 — 668,232 — Subordinated notes, net of unamortized debt issuance costs 98,500 98,722 — 98,722 — Trust preferred subordinated debentures, net of unamortized debt issuance costs 60,259 48,436 — 48,436 — Estimated Fair Value December 31, 2020 Carrying Total Level 1 Level 2 Level 3 Financial assets: Cash and cash equivalents $ 108,408 $ 108,408 $ 108,408 $ — $ — Investment securities: HTM, at carrying value 907 920 — 920 — Mortgage-backed securities: HTM, at carrying value 108,091 117,278 — 117,278 — FHLB stock, at cost 25,259 25,259 — 25,259 — Equity investments 5,811 5,811 — 5,811 — Loans, net of allowance for loan losses 3,608,773 3,784,291 — — 3,784,291 Loans held for sale 3,695 3,695 — 3,695 — Financial liabilities: Deposits $ 4,932,322 $ 4,936,188 $ — $ 4,936,188 $ — Other borrowings 23,172 23,172 — 23,172 — FHLB borrowings 832,527 854,865 — 854,865 — Subordinated notes, net of unamortized debt issuance costs 197,251 198,391 — 198,391 — Trust preferred subordinated debentures, net of unamortized debt issuance costs 60,255 51,993 — 51,993 —

Income Taxes Income Taxes (Tabl

Income Taxes Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	The income tax expense included in the accompanying consolidated statements of income consists of the following (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Current income tax expense $ 3,387 $ 3,133 $ 9,002 $ 11,376 Deferred income tax expense (benefit) 1,590 650 3,612 (4,305) Income tax expense $ 4,977 $ 3,783 $ 12,614 $ 7,071

Off-Balance-Sheet Arrangement_2

Off-Balance-Sheet Arrangements, Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Off-balance-sheet, Allowance for off-balance-sheet credit exposures	Allowance for off-balance-sheet credit exposures were as follows (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Balance at beginning of period $ 3,773 $ 6,365 $ 6,386 $ 1,455 Impact of CECL adoption — — — 4,840 Provision for (reversal of) off-balance-sheet credit exposures (683) (345) (3,296) (275) Balance at end of period $ 3,090 $ 6,020 $ 3,090 $ 6,020
Schedule of unused commitments	Financial instruments with off-balance-sheet risk were as follows (in thousands): September 30, 2021 December 31, 2020 Commitments to extend credit $ 954,258 $ 793,138 Standby letters of credit 10,812 13,658 Total $ 965,070 $ 806,796

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Basic and Diluted Earnings:
Net income	$ 29,306	$ 21,317	$ 34,091	$ 27,074	$ 21,554	$ 3,953	$ 84,714	$ 52,581
Basic weighted-average shares outstanding (in shares)	32,465			33,047			32,641	33,250
Add: Stock awards (in shares)	91			51			118	81
Diluted weighted-average shares outstanding (in shares)	32,556			33,098			32,759	33,331
Basic earnings per share:
Earnings per common share - basic (in dollars per share)	$ 0.90			$ 0.82			$ 2.60	$ 1.58
Diluted earnings per share:
Earnings per common share - diluted (in dollars per share)	$ 0.90			$ 0.82			$ 2.59	$ 1.58
Antidilutive securities excluded from calculating earnings
Number of antidilutive options (in shares)	462			835			288	811

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) - Accumulated Other Comprehensive Income, Changes In (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
AOCI Attributable to Parent, Net of Tax
Beginning balance, net of tax		$ 894,400	$ 817,605	$ 875,297	$ 804,580
Income tax benefit (expense)		5,560	(866)	6,674	(11,173)
Ending balance, net of tax		877,866	839,148	877,866	839,148
Unrealized Gains (Losses) on Securities
AOCI Attributable to Parent, Net of Tax
Beginning balance, net of tax		102,628	100,790	116,078	38,038
Other comprehensive (loss) income before reclassifications		(27,714)	1,601	(43,527)	88,900
Reclassification adjustments included in net income		(1,069)	316	(2,281)	(7,551)
Income tax benefit (expense)		6,045	(403)	9,620	(17,083)
Net current-period other comprehensive (loss) income, net of tax		(22,738)	1,514	(36,188)	64,266
Ending balance, net of tax		79,890	102,304	79,890	102,304
Unrealized Gains (Losses) on Derivatives
AOCI Attributable to Parent, Net of Tax
Beginning balance, net of tax		(8,334)	(20,904)	(17,091)	(1,672)
Other comprehensive (loss) income before reclassifications		377	(197)	8,296	(25,236)
Reclassification adjustments included in net income		1,617	1,587	4,784	2,283
Income tax benefit (expense)		(418)	(292)	(2,747)	4,819
Net current-period other comprehensive (loss) income, net of tax		1,576	1,098	10,333	(18,134)
Ending balance, net of tax		(6,758)	(19,806)	(6,758)	(19,806)
Net Prior Service (Cost) Credit
AOCI Attributable to Parent, Net of Tax
Reclassification adjustments included in net income	[1]	0	(2)	0	(6)
Net Gain (Loss)
AOCI Attributable to Parent, Net of Tax
Reclassification adjustments included in net income	[1]	316	821	948	2,213
Total
AOCI Attributable to Parent, Net of Tax
Beginning balance, net of tax		64,887	43,011	69,080	4,236
Other comprehensive (loss) income before reclassifications		(27,337)	1,404	(35,231)	56,269
Reclassification adjustments included in net income		864	2,722	3,451	(3,061)
Income tax benefit (expense)		5,560	(866)	6,674	(11,173)
Net current-period other comprehensive (loss) income, net of tax		(20,913)	3,260	(25,106)	42,035
Ending balance, net of tax		43,974	46,271	43,974	46,271
Pension Plans | Net Prior Service (Cost) Credit
AOCI Attributable to Parent, Net of Tax
Beginning balance, net of tax		149	(20)	149	(145)
Other comprehensive (loss) income before reclassifications		0	0	0	163
Reclassification adjustments included in net income		0	(2)	0	(6)
Income tax benefit (expense)		0	0	0	(34)
Net current-period other comprehensive (loss) income, net of tax		0	(2)	0	123
Ending balance, net of tax		149	(22)	149	(22)
Pension Plans | Net Gain (Loss)
AOCI Attributable to Parent, Net of Tax
Beginning balance, net of tax		(29,556)	(36,855)	(30,056)	(31,985)
Other comprehensive (loss) income before reclassifications		0	0	0	(7,558)
Reclassification adjustments included in net income		316	821	948	2,213
Income tax benefit (expense)		(67)	(171)	(199)	1,125
Net current-period other comprehensive (loss) income, net of tax		249	650	749	(4,220)
Ending balance, net of tax		$ (29,307)	$ (36,205)	$ (29,307)	$ (36,205)
[1]	These AOCI components are included in the computation of net periodic pension cost (income) presented in “Note 8 – Employee Benefit Plans.”

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income (Loss) - Reclassifications out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of unrealized gains and losses		$ 312	$ 394	$ 1,118	$ 730
Tax benefit (expense)		(4,977)	(3,783)	(12,614)	(7,071)
Realized net gain on sale of securities		1,381	78	3,399	8,281
Total reclassifications for the period, net of tax		(681)	(2,150)	(2,726)	2,418
Unrealized gains (losses)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassified from accumulated other comprehensive income		1,069	(316)	2,281	7,551
Realized net gain (loss) on interest rate swap derivatives
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassified from accumulated other comprehensive income		(1,617)	(1,587)	(4,784)	(2,283)
Net actuarial loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassified from accumulated other comprehensive income	[1]	(316)	(821)	(948)	(2,213)
Prior service credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassified from accumulated other comprehensive income	[1]	0	2	0	6
Amortization of pension plan
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassified from accumulated other comprehensive income		(316)	(819)	(948)	(2,207)
Tax benefit		67	172	199	463
Total reclassifications for the period, net of tax		(249)	(647)	(749)	(1,744)
Unrealized gains and losses on securities transferred | Reclassification out of accumulated other comprehensive income | Unrealized gains (losses)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of unrealized gains and losses	[2]	(312)	(394)	(1,118)	(730)
Tax benefit (expense)		66	82	235	153
Net of tax		(246)	(312)	(883)	(577)
Unrealized gains and losses on available for sale securities | Reclassification out of accumulated other comprehensive income | Unrealized gains (losses)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax benefit (expense)		(290)	(16)	(714)	(1,739)
Net of tax		1,091	62	2,685	6,542
Realized net gain on sale of securities	[3]	1,381	78	3,399	8,281
Interest rate swap derivatives | Reclassification out of accumulated other comprehensive income | Realized net gain (loss) on interest rate swap derivatives
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax benefit (expense)		340	335	1,005	484
Net of tax		(1,277)	(1,258)	(3,779)	(1,819)
Realized net (loss) gain on interest rate swap derivatives	[4]	(1,617)	(1,593)	(4,784)	(2,303)
Interest rate swap derivatives | Reclassification out of accumulated other comprehensive income | Amortization of unrealized gains on terminated interest rate swap derivatives
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax benefit (expense)		0	(1)	0	(4)
Net of tax		0	5	0	16
Realized net (loss) gain on interest rate swap derivatives	[4]	$ 0	$ 6	$ 0	$ 20
[1]	These AOCI components are included in the computation of net periodic pension cost (income) presented in “Note 8 – Employee Benefit Plans.”
[2]	Included in interest income on the consolidated statements of income.
[3]	Listed as net gain on sale of securities AFS on the consolidated statements of income.
[4]	Included in interest expense for FHLB borrowings on the consolidated statements of income.

Securities - Schedule of Debt S

Securities - Schedule of Debt Securities Components (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Dec. 31, 2020
Available-for-sale [Abstract]
Amortized Cost		$ 2,650,237	$ 2,437,513
Gross unrealized gains		110,187	150,074
Gross unrealized losses		7,320	282
Securities available for sale, at estimated fair value		2,753,104	2,587,305
HELD TO MATURITY
Amortized cost		92,479	108,998
Gross unrealized gains		5,556	9,200
Gross unrealized losses		0	0
Estimated Fair Value		98,035	118,198
US Treasury Securities
Available-for-sale [Abstract]
Amortized Cost		42,806
Gross unrealized gains		741
Gross unrealized losses		0
Securities available for sale, at estimated fair value		43,547
State and political subdivisions
Available-for-sale [Abstract]
Amortized Cost		1,890,814	1,475,030
Gross unrealized gains		83,140	105,601
Gross unrealized losses		6,477	37
Securities available for sale, at estimated fair value		1,967,477	1,580,594
HELD TO MATURITY
Amortized cost		788	907
Gross unrealized gains		3	13
Gross unrealized losses		0	0
Estimated Fair Value		791	920
Corporate bonds and other
Available-for-sale [Abstract]
Amortized Cost		117,332	77,224
Gross unrealized gains		2,563	1,053
Gross unrealized losses		196	22
Securities available for sale, at estimated fair value		119,699	78,255
Residential
Available-for-sale [Abstract]
Amortized Cost	[1]	493,505	771,409
Gross unrealized gains	[1]	20,943	38,674
Gross unrealized losses	[1]	370	73
Securities available for sale, at estimated fair value	[1]	514,078	810,010
HELD TO MATURITY
Amortized cost	[1]	40,128	47,948
Gross unrealized gains	[1]	2,616	4,187
Gross unrealized losses	[1]	0	0
Estimated Fair Value	[1]	42,744	52,135
Commercial
Available-for-sale [Abstract]
Amortized Cost	[1]	105,780	113,850
Gross unrealized gains	[1]	2,800	4,746
Gross unrealized losses	[1]	277	150
Securities available for sale, at estimated fair value	[1]	108,303	118,446
HELD TO MATURITY
Amortized cost	[1]	51,563	60,143
Gross unrealized gains	[1]	2,937	5,000
Gross unrealized losses	[1]	0	0
Estimated Fair Value	[1]	$ 54,500	$ 65,143
[1]	All MBS are issued and/or guaranteed by U.S. government agencies or U.S. GSEs.

Securities - Unrealized Loss on

Securities - Unrealized Loss on Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Available-for-sale, Unrealized Loss Position [Abstract]
Less than 12 Months, fair value	$ 433,487	$ 39,898
More than 12 Months, fair value	4,602	0
Total fair value	438,089	39,898
Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 Months, unrealized loss	7,043	282
More than 12 Months, unrealized Loss	277	0
Total unrealized loss	7,320	282
State and political subdivisions
Available-for-sale, Unrealized Loss Position [Abstract]
Less than 12 Months, fair value	396,345	17,305
More than 12 Months, fair value	0	0
Total fair value	396,345	17,305
Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 Months, unrealized loss	6,477	37
More than 12 Months, unrealized Loss	0	0
Total unrealized loss	6,477	37
Corporate bonds and other
Available-for-sale, Unrealized Loss Position [Abstract]
Less than 12 Months, fair value	21,352	11,562
More than 12 Months, fair value	0	0
Total fair value	21,352	11,562
Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 Months, unrealized loss	196	22
More than 12 Months, unrealized Loss	0	0
Total unrealized loss	196	22
Residential
Available-for-sale, Unrealized Loss Position [Abstract]
Less than 12 Months, fair value	15,790	6,287
More than 12 Months, fair value	0	0
Total fair value	15,790	6,287
Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 Months, unrealized loss	370	73
More than 12 Months, unrealized Loss	0	0
Total unrealized loss	370	73
Commercial
Available-for-sale, Unrealized Loss Position [Abstract]
Less than 12 Months, fair value	0	4,744
More than 12 Months, fair value	4,602	0
Total fair value	4,602	4,744
Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 Months, unrealized loss	0	150
More than 12 Months, unrealized Loss	277	0
Total unrealized loss	$ 277	$ 150

Securities - Interest Income on

Securities - Interest Income on Securities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Investments, Debt Securities [Abstract]
US Treasury	$ 182	$ 0	$ 388	$ 0
State and political subdivisions	12,223	9,787	33,568	26,281
Corporate bonds and other	1,097	391	2,928	568
MBS	4,405	7,048	15,140	27,626
Total interest income on securities	$ 17,907	$ 17,226	$ 52,024	$ 54,475

Securities - Amortized Cost and

Securities - Amortized Cost and Estimated Fair Value of Investments in Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Available for sale, Amortized Cost
Due in one year or less	$ 4,495
Due after one year through five years	26,705
Due after five years through ten years	175,953
Due after ten years	1,843,799
Total available-for-sale investment securities	2,050,952
MBS:	599,285
Amortized Cost	2,650,237	$ 2,437,513
Available for sale, Fair Value
Due in one year or less	4,532
Due after one year through five years	27,841
Due after five years through ten years	180,006
Due after ten years	1,918,344
Total available-for-sale investment securities	2,130,723
MBS:	622,381
Total	2,753,104	2,587,305
Held to maturity, Amortized Cost
Due in one year or less	120
Due after one year through five years	529
Due after five years through ten years	139
Due after ten years	0
Total held-to-maturity investment securities	788
Mortgage-backed securities	91,691
Amortized cost	92,479
Held to maturity, Fair Value
Due in one year or less	120
Due after one year through five years	531
Due after five years through ten years	140
Due after ten years	0
Total held-to-maturity investment securities	791
Mortgage-backed securities	97,244
Total	$ 98,035	$ 118,198

Securities - Unrealized and Rea

Securities - Unrealized and Realized Gain (Loss) Recognized in Net Income on Equity Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Investments, All Other Investments [Abstract]
Net (losses) gains recognized during the period on equity investments	$ (28)	$ (232)	$ (118)	$ (178)
Less: Net gains recognized during the period on equity investments sold during the period	0	0	0	0
Unrealized (losses) gains recognized during the reporting period on equity investments held at the reporting date	$ (28)	$ (232)	$ (118)	$ (178)

Securities - Narrative (Details

Securities - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Period Increase (Decrease)	$ 0	$ 0	$ 0	$ 0
Debt Securities, Available-for-sale, Allowance for Credit Loss	0		0		$ 0
Debt Securities, Held-to-maturity, Credit Loss Expense (Reversal)	0	0	0	0
Transferred Securities, Unrealized Loss, Before Tax	1,700,000		1,700,000		2,900,000
Securities transferred, Unrealized Loss, Net of Tax	1,400,000		1,400,000		2,300,000
Fair value of securities transferred from AFS to HTM			0		0
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Net gain on sale of securities AFS	1,381,000	$ 78,000	3,399,000	8,281,000
Gross realized gains on AFS securities			3,500,000	8,400,000
Gross realized losses on AFS securities			71,000	89,000
Carrying value of investment securities pledged as collateral	1,480,000,000		1,480,000,000		1,560,000,000
Equity investments	11,794,000		11,794,000		11,905,000
Debt Securities, Held-to-maturity, Sale or Transfer of Investment [Abstract]
Sale of HTM portfolio			0	$ 0
Interest receivable	29,097,000		29,097,000		38,708,000
Debt Securities, Held-to-maturity, Nonaccrual	0		0		0
FHLB stock with other-than-temporary impairment	0		0
Other-than-temporarily impaired equity investments	0		0
Financial Asset, Past Due
Debt Securities, Held-to-maturity, Sale or Transfer of Investment [Abstract]
Securities held to maturity (estimated fair value of $138,879)	0		0		0
Available-for-sale Securities
Debt Securities, Held-to-maturity, Sale or Transfer of Investment [Abstract]
Interest receivable	15,500,000		15,500,000		22,000,000
Held-to-maturity Securities
Debt Securities, Held-to-maturity, Sale or Transfer of Investment [Abstract]
Interest receivable	$ 240,000		$ 240,000		$ 298,000

Loans and Allowance for Loan _3

Loans and Allowance for Loan Losses - Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Loans and Leases Receivable Disclosure [Abstract]
Loans	$ 3,647,585		$ 3,657,779
Less: Allowance for loan losses	38,022	$ 42,913	49,006	$ 55,110	$ 59,868	$ 24,797
Total loans	3,609,563		3,608,773
Construction Real Estate Loans
Loans and Leases Receivable Disclosure [Abstract]
Loans	422,095		581,941
Less: Allowance for loan losses	4,983	8,018	6,490	5,626	8,500	3,539
1-4 Family Residential Real Estate Loans
Loans and Leases Receivable Disclosure [Abstract]
Loans	660,689		719,952
Less: Allowance for loan losses	1,946	2,520	2,270	2,635	2,702	3,833
Commercial Real Estate Loans
Loans and Leases Receivable Disclosure [Abstract]
Loans	1,605,132		1,295,746
Less: Allowance for loan losses	28,258	28,930	35,709	41,785	43,785	9,572
Commercial loans
Loans and Leases Receivable Disclosure [Abstract]
Loans	443,708		557,122
Less: Allowance for loan losses	2,560	3,097	4,107	4,492	4,221	6,351
Municipal loans
Loans and Leases Receivable Disclosure [Abstract]
Loans	427,259		409,028
Less: Allowance for loan losses	46	47	46	46	47	570
Loans to individuals
Loans and Leases Receivable Disclosure [Abstract]
Loans	88,702		93,990
Less: Allowance for loan losses	$ 229	$ 301	$ 384	$ 526	$ 613	$ 932

Loans and Allowance for Loan _4

Loans and Allowance for Loan Losses - Loans by Credit Quality Indicator and Origination Year (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	$ 904,048	$ 1,030,002
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	653,247	779,358
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	584,773	370,505
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	270,198	389,723
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	281,725	199,634
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	641,445	627,713
Financing Receivable, Excluding Accrued Interest, Revolving	312,149	260,844
Loans	3,647,585	3,657,779
Construction Real Estate Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	117,946	155,693
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	107,623	180,918
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	56,826	76,152
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	6,397	55,636
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	2,209	3,214
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	6,993	8,535
Financing Receivable, Excluding Accrued Interest, Revolving	124,101	101,793
Loans	422,095	581,941
Construction Real Estate Loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	117,946	155,693
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	107,623	180,536
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	56,826	76,090
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	6,343	55,636
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	2,209	3,191
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	6,755	8,297
Financing Receivable, Excluding Accrued Interest, Revolving	124,101	101,793
Loans	421,803	581,236
Construction Real Estate Loans | Pass Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	23
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	21	0
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	21	23
Construction Real Estate Loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	0	0
Construction Real Estate Loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	382
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	62
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	217	58
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	217	502
Construction Real Estate Loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	54	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0	180
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	54	180
1-4 Family Residential Real Estate Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	111,815	155,476
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	134,700	114,063
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	89,504	70,756
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	52,699	56,020
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	38,457	59,638
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	231,186	261,070
Financing Receivable, Excluding Accrued Interest, Revolving	2,328	2,929
Loans	660,689	719,952
1-4 Family Residential Real Estate Loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	111,806	154,003
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	134,208	114,063
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	89,450	70,621
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	52,699	55,557
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	38,027	57,680
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	226,835	255,003
Financing Receivable, Excluding Accrued Interest, Revolving	2,239	2,833
Loans	655,264	709,760
1-4 Family Residential Real Estate Loans | Pass Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	267
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	803	564
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	803	831
1-4 Family Residential Real Estate Loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	62	10
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	62	10
1-4 Family Residential Real Estate Loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	9	1,473
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	483	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	54	135
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	427
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	430	1,588
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	3,227	5,134
Financing Receivable, Excluding Accrued Interest, Revolving	89	96
Loans	4,292	8,853
1-4 Family Residential Real Estate Loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	9	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	36
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	103
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	259	359
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	268	498
Commercial Real Estate Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	451,633	282,184
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	238,183	340,181
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	330,813	155,468
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	159,147	202,510
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	177,007	105,759
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	242,068	202,687
Financing Receivable, Excluding Accrued Interest, Revolving	6,281	6,957
Loans	1,605,132	1,295,746
Commercial Real Estate Loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	448,184	270,087
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	237,377	307,161
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	317,768	143,177
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	127,342	162,180
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	154,680	98,828
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	230,388	179,919
Financing Receivable, Excluding Accrued Interest, Revolving	6,281	6,957
Loans	1,522,020	1,168,309
Commercial Real Estate Loans | Pass Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	4,163	3,153
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	23,242	40,125
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	22,159	1,696
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	1,645	2,582
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	51,209	47,556
Commercial Real Estate Loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	4,555
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	197	33,020
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	7,041
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	140
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	168	4,531
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	1,919	7,850
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	2,284	57,137
Commercial Real Estate Loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	3,449	7,542
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	609	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	8,882	2,097
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	8,563	65
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	704
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	7,991	12,282
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	29,494	22,690
Commercial Real Estate Loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	125	54
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	125	54
Commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	132,119	317,306
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	78,521	50,707
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	30,078	24,177
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	16,191	9,586
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	4,167	3,679
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	6,430	6,407
Financing Receivable, Excluding Accrued Interest, Revolving	176,202	145,260
Loans	443,708	557,122
Commercial loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	131,981	313,688
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	78,247	47,446
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	28,930	20,386
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	15,234	7,505
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	4,147	3,392
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	6,166	6,142
Financing Receivable, Excluding Accrued Interest, Revolving	174,372	140,018
Loans	439,077	538,577
Commercial loans | Pass Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	39	2,599
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	55	1,318
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	504	2,410
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	25	1,981
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Revolving	0	370
Loans	623	8,678
Commercial loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	304
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	809
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	124	433
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	381	39
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	286
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	183	265
Financing Receivable, Excluding Accrued Interest, Revolving	373	455
Loans	1,061	2,591
Commercial loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	91	405
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	194	1,081
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	379	473
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	165	7
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	20	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	1	0
Financing Receivable, Excluding Accrued Interest, Revolving	1,457	4,417
Loans	2,307	6,383
Commercial loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	8	310
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	25	53
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	141	475
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	386	54
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	1
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	80	0
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	640	893
Municipal loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	56,206	72,542
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	65,884	68,132
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	63,328	33,735
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	30,504	61,170
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	57,665	25,387
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	153,672	148,062
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	427,259	409,028
Municipal loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	56,206	72,542
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	65,884	68,132
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	63,328	33,735
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	30,504	61,170
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	57,665	25,387
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	153,672	148,062
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	427,259	409,028
Municipal loans | Pass Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	0	0
Municipal loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	0	0
Municipal loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	0	0
Municipal loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	0	0
Loans to individuals
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	34,329	46,801
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	28,336	25,357
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	14,224	10,217
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	5,260	4,801
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	2,220	1,957
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	1,096	952
Financing Receivable, Excluding Accrued Interest, Revolving	3,237	3,905
Loans	88,702	93,990
Loans to individuals | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	34,329	46,722
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	28,335	25,302
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	14,196	10,132
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	5,195	4,716
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	2,188	1,867
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	1,068	917
Financing Receivable, Excluding Accrued Interest, Revolving	3,236	3,900
Loans	88,547	93,556
Loans to individuals | Pass Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	0	0
Loans to individuals | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	0	51
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	40	0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	0	0
Financing Receivable, Excluding Accrued Interest, Revolving	0	4
Loans	40	55
Loans to individuals | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	6
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	1	35
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	27	28
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	14	30
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	22	9
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	10	11
Financing Receivable, Excluding Accrued Interest, Revolving	1	1
Loans	75	120
Loans to individuals | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year	0	73
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year	0	20
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year	1	6
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year	11	55
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year	10	81
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year	18	24
Financing Receivable, Excluding Accrued Interest, Revolving	0	0
Loans	$ 40	$ 259

Loans and Allowance for Loan _5

Loans and Allowance for Loan Losses - Aging of Past Due Loans by Class of Loan (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Loans	$ 3,647,585	$ 3,657,779
Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	3,642,611	3,636,192
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	3,372	10,440
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	979	7,437
Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	623	3,710
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	4,974	21,587
Construction Real Estate Loans
Financing Receivable, Past Due [Line Items]
Loans	422,095	581,941
Construction Real Estate Loans | Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	421,982	581,388
Construction Real Estate Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	72	95
Construction Real Estate Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	41	14
Construction Real Estate Loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	444
Construction Real Estate Loans | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	113	553
1-4 Family Residential Real Estate Loans
Financing Receivable, Past Due [Line Items]
Loans	660,689	719,952
1-4 Family Residential Real Estate Loans | Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	658,766	706,781
1-4 Family Residential Real Estate Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	652	7,872
1-4 Family Residential Real Estate Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	691	2,469
1-4 Family Residential Real Estate Loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	580	2,830
1-4 Family Residential Real Estate Loans | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	1,923	13,171
Commercial Real Estate Loans
Financing Receivable, Past Due [Line Items]
Loans	1,605,132	1,295,746
Commercial Real Estate Loans | Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	1,604,247	1,294,878
Commercial Real Estate Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	885	467
Commercial Real Estate Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	315
Commercial Real Estate Loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	86
Commercial Real Estate Loans | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	885	868
Commercial loans
Financing Receivable, Past Due [Line Items]
Loans	443,708	557,122
Commercial loans | Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	442,042	550,860
Commercial loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	1,402	1,423
Commercial loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	233	4,516
Commercial loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	31	323
Commercial loans | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	1,666	6,262
Municipal loans
Financing Receivable, Past Due [Line Items]
Loans	427,259	409,028
Municipal loans | Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	427,163	408,964
Municipal loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	96	64
Municipal loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	0
Municipal loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	0
Municipal loans | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	96	64
Loans to individuals
Financing Receivable, Past Due [Line Items]
Loans	88,702	93,990
Loans to individuals | Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	88,411	93,321
Loans to individuals | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	265	519
Loans to individuals | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	14	123
Loans to individuals | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	12	27
Loans to individuals | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	$ 291	$ 669

Loans and Allowance for Loan _6

Loans and Allowance for Loan Losses - Nonperforming Assets by Asset Class (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Dec. 31, 2020
Nonperforming Assets [Line Items]
Restructured nonaccrual loans		$ 1,100	$ 976
Nonperforming Assets
Nonperforming Assets [Line Items]
Nonaccrual loans	[1]	3,013	7,714
Accruing loans past due more than 90 days		0	0
TDR loans		9,371	9,646
OREO		25	106
Repossessed assets		15	14
Total nonperforming assets		12,424	17,480
Nonperforming Assets | Construction Real Estate Loans
Nonperforming Assets [Line Items]
Nonaccrual loans		63	640
Nonperforming Assets | 1-4 Family Residential Real Estate Loans
Nonperforming Assets [Line Items]
Nonaccrual loans		1,432	3,922
Nonperforming Assets | Commercial Real Estate Loans
Nonperforming Assets [Line Items]
Nonaccrual loans		796	1,269
Nonperforming Assets | Commercial loans
Nonperforming Assets [Line Items]
Nonaccrual loans		674	1,592
Nonperforming Assets | Loans to individuals
Nonperforming Assets [Line Items]
Nonaccrual loans		$ 48	$ 291
[1]	Includes $1.1 million and $976,000 of restructured loans as of September 30, 2021 and December 31, 2020, respectively.

Loans and Allowance for Loan _7

Loans and Allowance for Loan Losses - Troubled Debt Restructurings (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)contract	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)contract	Sep. 30, 2020USD ($)contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract	4		9	4
Total Modifications	$ 672	$ 0	$ 907	$ 175
1-4 Family Residential Real Estate Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract	3		5
Total Modifications	$ 219		$ 344
Commercial Real Estate Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract	1		1	1
Total Modifications	$ 453		$ 453	$ 58
Commercial loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract			3	3
Total Modifications			$ 110	$ 117
Extended Amortization Period
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Modifications	0		0	0
Extended Amortization Period | 1-4 Family Residential Real Estate Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Modifications	0		0
Extended Amortization Period | Commercial Real Estate Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Modifications	0		0	0
Extended Amortization Period | Commercial loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Modifications			0	0
Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Modifications	0		16	0
Interest Rate Reduction | 1-4 Family Residential Real Estate Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Modifications	0		0
Interest Rate Reduction | Commercial Real Estate Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Modifications	0		0	0
Interest Rate Reduction | Commercial loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Modifications			16	0
Combination
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Modifications	672		891	175
Combination | 1-4 Family Residential Real Estate Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Modifications	219		344
Combination | Commercial Real Estate Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Modifications	$ 453		453	58
Combination | Commercial loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Modifications			$ 94	$ 117

Loans and Allowance for Loan _8

Loans and Allowance for Loan Losses - Allowance for Loan Losses Activity by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Allowances for Loan Losses [Roll Forward]
Balance at beginning of period	$ 42,913	$ 59,868	$ 49,006	$ 24,797
Loans charged-off	(940)	(718)	(2,262)	(2,259)
Recoveries of loans charged-off	437	361	1,525	1,248
Net loans (charged-off) recovered	(503)	(357)	(737)	(1,011)
Provision for (reversal of) loan losses(1)	(4,388)	(4,401)	(10,247)	26,021	[1]
Balance at end of period	38,022	55,110	38,022	55,110
Construction Real Estate Loans
Allowances for Loan Losses [Roll Forward]
Balance at beginning of period	8,018	8,500	6,490	3,539
Loans charged-off	0	(6)	0	(39)
Recoveries of loans charged-off	1	0	2	11
Net loans (charged-off) recovered	1	(6)	2	(28)
Provision for (reversal of) loan losses(1)	(3,036)	(2,868)	(1,509)	(838)	[1]
Balance at end of period	4,983	5,626	4,983	5,626
1-4 Family Residential Real Estate Loans
Allowances for Loan Losses [Roll Forward]
Balance at beginning of period	2,520	2,702	2,270	3,833
Loans charged-off	(35)	(18)	(136)	(74)
Recoveries of loans charged-off	4	9	71	29
Net loans (charged-off) recovered	(31)	(9)	(65)	(45)
Provision for (reversal of) loan losses(1)	(543)	(58)	(259)	300	[1]
Balance at end of period	1,946	2,635	1,946	2,635
Commercial Real Estate Loans
Allowances for Loan Losses [Roll Forward]
Balance at beginning of period	28,930	43,785	35,709	9,572
Loans charged-off	0	(12)	0	(33)
Recoveries of loans charged-off	12	13	13	94
Net loans (charged-off) recovered	12	1	13	61
Provision for (reversal of) loan losses(1)	(684)	(2,001)	(7,464)	24,089	[1]
Balance at end of period	28,258	41,785	28,258	41,785
Commercial loans
Allowances for Loan Losses [Roll Forward]
Balance at beginning of period	3,097	4,221	4,107	6,351
Loans charged-off	(508)	(279)	(943)	(800)
Recoveries of loans charged-off	74	61	535	191
Net loans (charged-off) recovered	(434)	(218)	(408)	(609)
Provision for (reversal of) loan losses(1)	(103)	489	(1,139)	2,304	[1]
Balance at end of period	2,560	4,492	2,560	4,492
Municipal loans
Allowances for Loan Losses [Roll Forward]
Balance at beginning of period	47	47	46	570
Loans charged-off	0	0	0	0
Recoveries of loans charged-off	0	0	0	0
Net loans (charged-off) recovered	0	0	0	0
Provision for (reversal of) loan losses(1)	(1)	(1)	0	(2)	[1]
Balance at end of period	46	46	46	46
Loans to individuals
Allowances for Loan Losses [Roll Forward]
Balance at beginning of period	301	613	384	932
Loans charged-off	(397)	(403)	(1,183)	(1,313)
Recoveries of loans charged-off	346	278	904	923
Net loans (charged-off) recovered	(51)	(125)	(279)	(390)
Provision for (reversal of) loan losses(1)	(21)	38	124	168	[1]
Balance at end of period	$ 229	$ 526	$ 229	526
Impact of CECL adoption
Allowances for Loan Losses [Roll Forward]
Impact of CECL adoption - cumulative effect adjustment				5,072
Impact of CECL adoption - purchased loans with credit deterioration				231
Impact of CECL adoption | Construction Real Estate Loans
Allowances for Loan Losses [Roll Forward]
Impact of CECL adoption - cumulative effect adjustment				2,968
Impact of CECL adoption - purchased loans with credit deterioration				(15)
Impact of CECL adoption | 1-4 Family Residential Real Estate Loans
Allowances for Loan Losses [Roll Forward]
Impact of CECL adoption - cumulative effect adjustment				(1,447)
Impact of CECL adoption - purchased loans with credit deterioration				(6)
Impact of CECL adoption | Commercial Real Estate Loans
Allowances for Loan Losses [Roll Forward]
Impact of CECL adoption - cumulative effect adjustment				7,730
Impact of CECL adoption - purchased loans with credit deterioration				333
Impact of CECL adoption | Commercial loans
Allowances for Loan Losses [Roll Forward]
Impact of CECL adoption - cumulative effect adjustment				(3,532)
Impact of CECL adoption - purchased loans with credit deterioration				(22)
Impact of CECL adoption | Municipal loans
Allowances for Loan Losses [Roll Forward]
Impact of CECL adoption - cumulative effect adjustment				(522)
Impact of CECL adoption - purchased loans with credit deterioration				0
Impact of CECL adoption | Loans to individuals
Allowances for Loan Losses [Roll Forward]
Impact of CECL adoption - cumulative effect adjustment				(125)
Impact of CECL adoption - purchased loans with credit deterioration				$ (59)
[1]	The increase in the provision for credit losses during the nine months ended September 30, 2020 was primarily due to the economic impact of COVID-19 on macroeconomic factors used in the CECL model.

Loans and Allowance for Loan _9

Loans and Allowance for Loan Losses - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Interest receivable	$ 29,097,000		$ 29,097,000			$ 38,708,000
Reversal of interest income on nonaccrual loans	5,000	$ 0	13,000	$ 147,000
Nonaccrual loans, no allowance	1,100,000		1,100,000			2,200,000
Collateral-dependent loans	9,100,000		9,100,000			11,500,000
Commitments to lend additional funds on Troubled Debt Restructurings (TDR)	0	0	0	0
Mortgage Loans in Process of Foreclosure, Amount	0		0			1,200,000
Accrued interest receivable on our loan portfolio	13,300,000		13,300,000			16,400,000
Allowance for Credit Loss	38,022,000	55,110,000	38,022,000	55,110,000	$ 42,913,000	49,006,000	$ 59,868,000	$ 24,797,000
COVID-19 Payment Deferral
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0		0			47,200,000
Commercial Real Estate Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Owner and nonowner-occupied real estate	1,320,000,000		1,320,000,000
Loans secured by multi-family properties	260,100,000		260,100,000
Loans secured by farmland	22,000,000		$ 22,000,000
General Loan Term			20 years
Allowance for Credit Loss	28,258,000	41,785,000	$ 28,258,000	41,785,000	28,930,000	35,709,000	43,785,000	9,572,000
1-4 Family Residential Real Estate Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Credit Loss	1,946,000	2,635,000	$ 1,946,000	2,635,000	2,520,000	2,270,000	2,702,000	3,833,000
1-4 Family Residential Real Estate Loans | Minimum
Financing Receivable, Allowance for Credit Loss [Line Items]
General Loan Term			5 years
1-4 Family Residential Real Estate Loans | Maximum
Financing Receivable, Allowance for Credit Loss [Line Items]
General Loan Term			30 years
Paycheck Protection Program
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	67,500,000		$ 67,500,000			214,800,000
Allowance for Credit Loss	0		0
Commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for Credit Loss	$ 2,560,000	$ 4,492,000	$ 2,560,000	$ 4,492,000	$ 3,097,000	$ 4,107,000	$ 4,221,000	$ 6,351,000

Borrowing Arrangements (Details

Borrowing Arrangements (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Other borrowings		$ 20,724	$ 23,172
FHLB borrowings		659,204	832,527
Other borrowings:
Debt Instrument [Line Items]
Other borrowings		20,724	23,172
Average amount outstanding during the period	[1]	22,387	91,940
Maximum amount outstanding during the period	[2]	$ 24,549	$ 219,259
Weighted average interest rate during the period	[3]	0.20%	0.40%
Interest rate at end of the period	[4]	0.20%	0.10%
FHLB borrowings:
Debt Instrument [Line Items]
FHLB borrowings		$ 659,204	$ 832,527
Average amount outstanding during the period	[1]	684,280	1,032,269
Maximum amount outstanding during the period	[2]	$ 723,584	$ 1,274,370
Weighted average interest rate during the period	[3]	1.10%	1.10%
Interest rate at end of the period	[5]	1.10%	1.00%
[1]	The average amount outstanding during the period was computed by dividing the total daily outstanding principal balances by the number of days in the period.
[2]	The maximum amount outstanding at any month-end during the period.
[3]	The weighted average interest rate during the period was computed by dividing the actual interest expense (annualized for interim periods) by the average amount outstanding during the period. The weighted average interest rate on the FHLB borrowings includes the effect of interest rate swaps.
[4]	Stated rate.
[5]	The interest rate on the FHLB borrowings includes the effect of interest rate swaps.

Borrowings Maturities Table (De

Borrowings Maturities Table (Details) $ in Thousands	Sep. 30, 2021USD ($)
Debt Instrument [Line Items]
Less than 1 Year	$ 676,397
1-2 Years	702
2-3 Years	733
3-4 Years	764
4-5 Years	582
Thereafter	750
Total	679,928
Other borrowings:
Debt Instrument [Line Items]
Less than 1 Year	20,724
1-2 Years	0
2-3 Years	0
3-4 Years	0
4-5 Years	0
Thereafter	0
Total	20,724
FHLB borrowings:
Debt Instrument [Line Items]
Less than 1 Year	655,673
1-2 Years	702
2-3 Years	733
3-4 Years	764
4-5 Years	582
Thereafter	750
Total	$ 659,204

Borrowing Arrangements Narrativ

Borrowing Arrangements Narrative (Details)	9 Months Ended
	Sep. 30, 2021USD ($)oustanding_letters_of_creditcredit_lineagreementRate	Dec. 31, 2020USD ($)
Line of Credit Facility [Line Items]
Number of credit lines maintained by the Company | credit_line	3
Carrying value of investment securities pledged as collateral	$ 1,480,000,000	$ 1,560,000,000
Federal funds purchased	0	0
Letters of Credit, Federal Home Loan Bank, as collateral	$ 0
Maturity of repurchase agreements (less than)	1 year
Securities sold under repurchase agreements	$ 20,700,000	23,200,000
Federal Home Loan Bank borrowings, additional funding available	1,220,000,000
Borrowings with variable interest rate, face amount	605,000,000
Frost Bank
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	40,000,000
Line of credit, capacity available for issuance of letters of credit	$ 5,000,000
Number of outstanding letters of credit | oustanding_letters_of_credit	1
Letters of Credit Outstanding, Amount	$ 91,000
TIB - The Independent Bankers Bank
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	15,000,000
Comerica Bank
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	7,500,000
Federal Reserve Discount Window
Line of Credit Facility [Line Items]
Additional funding available	$ 476,100,000
Minimum
Line of Credit Facility [Line Items]
Federal Home Loan Bank borrowings interest rates	0.13%
Federal Home Loan Bank borrowings maturities	4 days
Maximum
Line of Credit Facility [Line Items]
Federal Home Loan Bank borrowings interest rates	4.799%
Federal Home Loan Bank borrowings maturities	6 years 9 months 18 days
Variable Rate Agreements and Fixed Short-term Pay Agreements
Line of Credit Facility [Line Items]
Borrowings with variable interest rate, face amount	$ 605,000,000	670,000,000
Three-Month London Interbank Offered Rate (LIBOR) | Variable Rate Agreements and Fixed Short-term Pay Agreements
Line of Credit Facility [Line Items]
Description of variable and fixed rate basis	three-month LIBOR
Three-Month London Interbank Offered Rate (LIBOR) | Variable Rate Agreements and Fixed Short-term Pay Agreements | Maximum
Line of Credit Facility [Line Items]
Debt Instrument, Number Of Variable Rate Advance Agreements | agreement	6
One-Month London Interbank Offered Rate (LIBOR) | Variable Rate Agreements and Fixed Short-term Pay Agreements
Line of Credit Facility [Line Items]
Description of variable and fixed rate basis	one-month LIBOR
Cash flow hedging | Variable Rate Agreements and Fixed Short-term Pay Agreements
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate During Period | Rate	1.18%
Derivative, Average Remaining Maturity	3 years 4 months 24 days
Federal Reserve Discount Window
Line of Credit Facility [Line Items]
Other borrowings	$ 0	$ 0

Long-term Debt Other Long-term

Long-term Debt Other Long-term Debt (Details) - USD ($) $ in Thousands

Sep. 30, 2021

Sep. 30, 2021

Dec. 31, 2020

Nov. 06, 2020

Sep. 19, 2016

Oct. 10, 2007

Aug. 10, 2007

Aug. 08, 2007

May 20, 2005

[5]

Sep. 04, 2003

Debt Instruments [Abstract]

Subordinated notes, net of unamortized debt issuance costs:

[1]

$ 98,500

$ 98,500

$ 197,251

Trust preferred subordinated debentures

[2]

60,259

60,259

60,255

Total long-term debt

158,759

158,759

257,506

5.50% Subordinated Notes

Debt Instruments [Abstract]

Subordinated notes, net of unamortized debt issuance costs:

[1],[3]

$ 0

0

98,754

Unamortized Debt Issuance Expense

$ 1,200

Stated interest rate

5.50%

5.50%

5.50% Subordinated Notes | London Interbank Offered Rate (LIBOR)

Debt Instruments [Abstract]

Basis on variable rate

4.297%

Southside Statutory Trust III, net of unamortized debt issuance costs

Debt Instruments [Abstract]

Trust preferred subordinated debentures

$ 20,567

[2],[4]

20,567

[2],[4]

$ 20,563

[2],[4]

$ 20,619

Unamortized Debt Issuance Expense

52

52

56

Southside Statutory Trust IV

Debt Instruments [Abstract]

Trust preferred subordinated debentures

23,196

[2]

23,196

[2]

23,196

[2]

$ 23,196

Southside Statutory Trust V

Debt Instruments [Abstract]

Trust preferred subordinated debentures

12,887

[2]

12,887

[2]

12,887

[2]

$ 12,887

Magnolia Trust Company I

Debt Instruments [Abstract]

Trust preferred subordinated debentures

3,609

[2]

3,609

[2]

3,609

[2]

$ 3,600

$ 3,609

3.875% Subordinated Notes

Debt Instruments [Abstract]

Subordinated notes, net of unamortized debt issuance costs:

[1],[6]

98,500

98,500

98,497

Unamortized Debt Issuance Expense

$ 1,500

$ 1,500

$ 1,500

Stated interest rate

3.875%

3.875%

3.875%

Minimum

Debt Instruments [Abstract]

Subordinated notes, remaining maturity, greater than

1 year

[1]

This debt consists of subordinated notes with a remaining maturity greater than one year that qualify under the risk-based capital guidelines as Tier 2 capital, subject to certain limitations.

[2]

This debt consists of trust preferred securities that qualify under the risk-based capital guidelines as Tier 1 capital, subject to certain limitations.

[3]

The unamortized discount and debt issuance costs reflected in the carrying amount of the subordinated notes totaled approximately $1.2 million at December 31, 2020.

[4]

The unamortized debt issuance costs reflected in the carrying amount of the Southside Statutory Trust III junior subordinated debentures totaled $52,000 at September 30, 2021 and $56,000 at December 31, 2020.

[5]

On October 10, 2007, as part of an acquisition we assumed $3.6 million of floating rate junior subordinated debentures issued in 2005 to Magnolia Trust Company I.

[6]

The unamortized discount and debt issuance costs reflected in the carrying amount of the subordinated notes totaled approximately $1.5 million at September 30, 2021 and December 31, 2020.

Long-term Debt LT Debt Interest

Long-term Debt LT Debt Interest Rates (Details) - USD ($)

Nov. 14, 2025

Sep. 30, 2021

Aug. 10, 2007

Aug. 08, 2007

May 20, 2005

Sep. 04, 2003

Sep. 30, 2021

Dec. 31, 2020

Nov. 06, 2020

Sep. 19, 2016

Oct. 10, 2007

Debt Instrument [Line Items]

Debt face amount

$ 605,000,000

$ 605,000,000

Other long-term debt

[1]

$ 60,259,000

$ 60,259,000

$ 60,255,000

5.50% Subordinated Notes

Debt Instrument [Line Items]

Debt face amount

$ 100,000,000

Stated interest rate

5.50%

5.50%

Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed

100.00%

5.50% Subordinated Notes | London Interbank Offered Rate (LIBOR)

Debt Instrument [Line Items]

Basis on variable rate

4.297%

Southside Statutory Trust III

Debt Instrument [Line Items]

Other long-term debt

$ 20,567,000

[1],[2]

$ 20,619,000

$ 20,567,000

[1],[2]

$ 20,563,000

[1],[2]

Southside Statutory Trust III | Three-Month London Interbank Offered Rate (LIBOR)

Debt Instrument [Line Items]

Basis on variable rate

2.94%

Southside Statutory Trust IV

Debt Instrument [Line Items]

Other long-term debt

23,196,000

[1]

$ 23,196,000

23,196,000

[1]

23,196,000

[1]

Southside Statutory Trust IV | Three-Month London Interbank Offered Rate (LIBOR)

Debt Instrument [Line Items]

Basis on variable rate

1.30%

Southside Statutory Trust V

Debt Instrument [Line Items]

Other long-term debt

12,887,000

[1]

$ 12,887,000

12,887,000

[1]

12,887,000

[1]

Southside Statutory Trust V | Three-Month London Interbank Offered Rate (LIBOR)

Debt Instrument [Line Items]

Basis on variable rate

2.25%

Magnolia Trust Company I

Debt Instrument [Line Items]

Other long-term debt

$ 3,609,000

[1]

$ 3,609,000

[3]

$ 3,609,000

[1]

$ 3,609,000

[1]

$ 3,600,000

Magnolia Trust Company I | Three-Month London Interbank Offered Rate (LIBOR)

Debt Instrument [Line Items]

Basis on variable rate

1.80%

3.875% Subordinated Notes

Debt Instrument [Line Items]

Debt face amount

$ 100,000,000

Stated interest rate

3.875%

3.875%

3.875%

Forecast | 3.875% Subordinated Notes | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate

Debt Instrument [Line Items]

Basis on variable rate

3.66%

[1]

This debt consists of trust preferred securities that qualify under the risk-based capital guidelines as Tier 1 capital, subject to certain limitations.

[2]

The unamortized debt issuance costs reflected in the carrying amount of the Southside Statutory Trust III junior subordinated debentures totaled $52,000 at September 30, 2021 and $56,000 at December 31, 2020.

[3]

On October 10, 2007, as part of an acquisition we assumed $3.6 million of floating rate junior subordinated debentures issued in 2005 to Magnolia Trust Company I.

Employee Benefit Plans (Details

Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Loss due to curtailment			$ 0	$ 163
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 483	0	1,311
Interest cost	642	672	1,927	2,359
Expected return on assets	(1,355)	(1,344)	(4,065)	(4,332)
Net loss amortization	251	694	752	1,780
Prior service (credit) cost amortization	0	(4)	0	(11)
Loss due to curtailment			0	151
Net periodic benefit (income) cost	(462)	501	(1,386)	1,258
Defined Benefit Pension Plan Acquired
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	0
Interest cost	23	41	69	122
Expected return on assets	(53)	(75)	(158)	(226)
Net loss amortization	1	2	4	7
Prior service (credit) cost amortization	0	0	0	0
Loss due to curtailment			0	0
Net periodic benefit (income) cost	(29)	(32)	(85)	(97)
Restoration Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	149	0	280
Interest cost	130	126	390	442
Expected return on assets	0	0	0	0
Net loss amortization	64	125	192	426
Prior service (credit) cost amortization	0	2	0	5
Loss due to curtailment			0	12
Net periodic benefit (income) cost	$ 194	$ 402	$ 582	$ 1,165

Employee Benefit Plans Narrativ

Employee Benefit Plans Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Noncash adjustment to employee benefit plan liabilities, consisting of changes in prior service cost and net loss			$ 948	$ (5,200)
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	6.125%	6.50%
Defined Benefit Pension Plan Acquired
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	6.125%	6.50%

Derivative Financial Instrume_3

Derivative Financial Instruments and Hedging Activities - Schedule Of Derivative Instruments (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Dec. 31, 2020
Asset Derivative
Gross derivatives		$ 16,350	$ 18,537
Offsetting derivative assets		(2,005)	0
Cash collateral received/posted		0	0
Net derivatives included in the consolidated balance sheets	[1]	14,345	18,537
Liability Derivative
Gross derivatives		24,905	40,172
Offsetting derivative liabilities		(2,005)	0
Cash collateral received/posted		(21,380)	(39,270)
Net derivatives included in the consolidated balance sheets	[1]	1,520	902
Financial Institution Counterparties
Derivatives, Fair Value [Line Items]
Credit exposure related to interest rate swaps		0	0
Financial Institution Counterparties | Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	[2]	605,000	670,000
Asset Derivative
Gross derivatives		1,543	0
Liability Derivative
Gross derivatives		10,098	21,635
Financial Institution Counterparties | Not Designated as Hedging Instrument | Interest Rate Swap
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	[2]	215,502	152,280
Asset Derivative
Gross derivatives		462	0
Liability Derivative
Gross derivatives		14,345	18,537
Customer Counterparties
Derivatives, Fair Value [Line Items]
Credit exposure related to interest rate swaps		14,300	18,500
Customer Counterparties | Not Designated as Hedging Instrument | Interest Rate Swap
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	[2]	215,502	152,280
Asset Derivative
Gross derivatives		14,345	18,537
Liability Derivative
Gross derivatives		$ 462	$ 0
[1]	Net derivative assets are included in other assets and net derivative liabilities are included in other liabilities on the consolidated balance sheets. Included in the fair value of net derivative assets and net derivative liabilities are credit valuation adjustments reflecting counterparty credit risk and our credit risk. We had no credit exposure related to interest rate swaps with financial institutions and $14.3 million related to interest rate swaps with customers at September 30, 2021. We had no credit exposure related to interest rate swaps with financial institutions and $18.5 million related to interest rate swaps with customers at December 31, 2020. The credit risk associated with customer transactions is partially mitigated as these are generally secured by the non-cash collateral securing the underlying transaction being hedged.
[2]	Notional amounts, which represent the extent of involvement in the derivatives market, are used to determine the contractual cash flows required in accordance with the terms of the agreement. These amounts are typically not exchanged, significantly exceed amounts subject to credit or market risk and are not reflected in the consolidated balance sheets.

Derivative Financial Instrume_4

Derivative Financial Instruments and Hedging Activities - Weighted Average Remaining Maturity, Lives, and Rates of Interest Rate Swaps (Details) - Interest Rate Swap - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2021	Dec. 31, 2020
Financial Institution Counterparties | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Notional Amount	[1]	$ 215,502	$ 152,280
Remaining Maturity		10 years 6 months	9 years 9 months 18 days
Weighted Average Receive Rate		0.45%	0.50%
Weighted Average Pay Rate		2.43%	2.57%
Financial Institution Counterparties | Cash Flow Hedging | Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Notional Amount	[1]	$ 605,000	$ 670,000
Remaining Maturity		3 years 4 months 24 days	3 years 9 months 18 days
Weighted Average Receive Rate		0.10%	0.17%
Weighted Average Pay Rate		1.18%	1.12%
Customer Counterparties | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Notional Amount	[1]	$ 215,502	$ 152,280
Remaining Maturity		10 years 6 months	9 years 9 months 18 days
Weighted Average Receive Rate		2.43%	2.57%
Weighted Average Pay Rate		0.45%	0.50%
[1]	Notional amounts, which represent the extent of involvement in the derivatives market, are used to determine the contractual cash flows required in accordance with the terms of the agreement. These amounts are typically not exchanged, significantly exceed amounts subject to credit or market risk and are not reflected in the consolidated balance sheets.

Derivative Financial Instrume_5

Derivative Financial Instruments and Hedging Activities - Narrative (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Debt face amount	$ 605,000,000
Cash collateral held by counterparties subject to master netting agreements	$ 21,400,000	$ 39,300,000

Fair Value Measurement - Recurr

Fair Value Measurement - Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		$ 2,753,104	$ 2,587,305
Derivative assets	[1]	14,345	18,537
Derivative liabilities	[1]	1,520	902
US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		43,547
State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		1,967,477	1,580,594
Corporate bonds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		119,699	78,255
Residential MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	[2]	514,078	810,010
Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	[2]	108,303	118,446
Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments		5,976	6,094
Total asset fair value measurements		2,775,430	2,611,936
Total liability fair value measurements		24,905	40,172
Fair Value, Recurring | US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		43,547
Fair Value, Recurring | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		1,967,477	1,580,594
Fair Value, Recurring | Corporate bonds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		119,699	78,255
Fair Value, Recurring | Residential MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	[3]	514,078	810,010
Fair Value, Recurring | Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	[3]	108,303	118,446
Fair Value, Recurring | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		16,350	18,537
Derivative liabilities		24,905	40,172
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments		5,976	6,094
Total asset fair value measurements		49,523	6,094
Total liability fair value measurements		0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		43,547
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Residential MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	[3]	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	[3]	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Derivative liabilities		0	0
Fair Value, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments		0	0
Total asset fair value measurements		2,725,907	2,605,842
Total liability fair value measurements		24,905	40,172
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		0
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		1,967,477	1,580,594
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		119,699	78,255
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Residential MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	[3]	514,078	810,010
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	[3]	108,303	118,446
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		16,350	18,537
Derivative liabilities		24,905	40,172
Fair Value, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments		0	0
Total asset fair value measurements		0	0
Total liability fair value measurements		0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value		0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Residential MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	[3]	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	[3]	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Derivative liabilities		0	0
Fair Value, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreclosed assets		40	120
Total asset fair value measurements		8,619	10,773
Fair Value, Nonrecurring | Collateral-dependent loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral-dependent loans	[4]	8,579	10,653
Fair Value, Nonrecurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreclosed assets		0	0
Total asset fair value measurements		0	0
Fair Value, Nonrecurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Collateral-dependent loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral-dependent loans	[4]	0	0
Fair Value, Nonrecurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreclosed assets		0	0
Total asset fair value measurements		0	0
Fair Value, Nonrecurring | Significant Other Observable Inputs (Level 2) | Collateral-dependent loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral-dependent loans	[4]	0	0
Fair Value, Nonrecurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreclosed assets		40	120
Total asset fair value measurements		8,619	10,773
Fair Value, Nonrecurring | Significant Unobservable Inputs (Level 3) | Collateral-dependent loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral-dependent loans	[4]	$ 8,579	$ 10,653
[1]	Net derivative assets are included in other assets and net derivative liabilities are included in other liabilities on the consolidated balance sheets. Included in the fair value of net derivative assets and net derivative liabilities are credit valuation adjustments reflecting counterparty credit risk and our credit risk. We had no credit exposure related to interest rate swaps with financial institutions and $14.3 million related to interest rate swaps with customers at September 30, 2021. We had no credit exposure related to interest rate swaps with financial institutions and $18.5 million related to interest rate swaps with customers at December 31, 2020. The credit risk associated with customer transactions is partially mitigated as these are generally secured by the non-cash collateral securing the underlying transaction being hedged.
[2]	All MBS are issued and/or guaranteed by U.S. government agencies or U.S. GSEs.
[3]	All MBS are issued and/or guaranteed by U.S. government agencies or U.S. GSEs.
[4]	Consists of individually evaluated loans. Loans for which the fair value of the collateral and commercial real estate fair value of the properties is less than cost basis are presented net of allowance. Losses on these loans represent charge-offs which are netted against the allowance for loan losses.

Fair Value Measurement - Balanc

Fair Value Measurement - Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Carrying Amount
Financial assets:
Cash and cash equivalents	$ 87,133	$ 108,408
Investment securities:
HTM, at carrying value	788	907
Mortgage-backed securities:
HTM, at carrying value	91,691	108,091
FHLB stock, at cost	27,248	25,259
Equity investments	5,818	5,811
Loans, net of allowance for loan losses	3,609,563	3,608,773
Loans held for sale	1,131	3,695
Financial liabilities:
Deposits	5,331,655	4,932,322
Other borrowings	20,724	23,172
FHLB borrowings	659,204	832,527
Subordinated notes, net of unamortized debt issuance costs	98,500	197,251
Trust preferred subordinated debentures, net of unamortized debt issuance costs	60,259	60,255
Estimated Fair Value
Financial assets:
Cash and cash equivalents	87,133	108,408
Investment securities:
HTM, at carrying value	791	920
Mortgage-backed securities:
HTM, at carrying value	97,244	117,278
FHLB stock, at cost	27,248	25,259
Equity investments	5,818	5,811
Loans, net of allowance for loan losses	3,755,534	3,784,291
Loans held for sale	1,131	3,695
Financial liabilities:
Deposits	5,333,064	4,936,188
Other borrowings	20,724	23,172
FHLB borrowings	668,232	854,865
Subordinated notes, net of unamortized debt issuance costs	98,722	198,391
Trust preferred subordinated debentures, net of unamortized debt issuance costs	48,436	51,993
Estimated Fair Value | Level 1
Financial assets:
Cash and cash equivalents	87,133	108,408
Investment securities:
HTM, at carrying value	0	0
Mortgage-backed securities:
HTM, at carrying value	0	0
FHLB stock, at cost	0	0
Equity investments	0	0
Loans, net of allowance for loan losses	0	0
Loans held for sale	0	0
Financial liabilities:
Deposits	0	0
Other borrowings	0	0
FHLB borrowings	0	0
Subordinated notes, net of unamortized debt issuance costs	0	0
Trust preferred subordinated debentures, net of unamortized debt issuance costs	0	0
Estimated Fair Value | Level 2
Financial assets:
Cash and cash equivalents	0	0
Investment securities:
HTM, at carrying value	791	920
Mortgage-backed securities:
HTM, at carrying value	97,244	117,278
FHLB stock, at cost	27,248	25,259
Equity investments	5,818	5,811
Loans, net of allowance for loan losses	0	0
Loans held for sale	1,131	3,695
Financial liabilities:
Deposits	5,333,064	4,936,188
Other borrowings	20,724	23,172
FHLB borrowings	668,232	854,865
Subordinated notes, net of unamortized debt issuance costs	98,722	198,391
Trust preferred subordinated debentures, net of unamortized debt issuance costs	48,436	51,993
Estimated Fair Value | Level 3
Financial assets:
Cash and cash equivalents	0	0
Investment securities:
HTM, at carrying value	0	0
Mortgage-backed securities:
HTM, at carrying value	0	0
FHLB stock, at cost	0	0
Equity investments	0	0
Loans, net of allowance for loan losses	3,755,534	3,784,291
Loans held for sale	0	0
Financial liabilities:
Deposits	0	0
Other borrowings	0	0
FHLB borrowings	0	0
Subordinated notes, net of unamortized debt issuance costs	0	0
Trust preferred subordinated debentures, net of unamortized debt issuance costs	$ 0	$ 0

Fair Value Measurement Narrativ

Fair Value Measurement Narrative (Details)	9 Months Ended
	Sep. 30, 2021source
Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of third party sources used to validate prices, in some cases	2
Derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of third party sources used to validate prices, in some cases	2

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Current income tax expense	$ 3,387	$ 3,133	$ 9,002	$ 11,376
Deferred income tax expense (benefit)	1,590	650	3,612	(4,305)
Income tax expense	$ 4,977	$ 3,783	$ 12,614	$ 7,071

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Deferred tax liability, net	$ 12,500,000		$ 12,500,000		$ 15,500,000
Deferred tax assets, valuation allowance	0		0		$ 0
Income tax expense	$ 4,977,000	$ 3,783,000	$ 12,614,000	$ 7,071,000
Effective income tax rate, percent	14.50%	12.30%	13.00%	11.90%

Off-Balance-Sheet Arrangement_3

Off-Balance-Sheet Arrangements, Allowance for off-balance-sheet credit exposures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Balance at beginning of period	$ 3,773	$ 6,365	$ 6,386	$ 1,455
Provision for (reversal of) off-balance-sheet credit exposures	(683)	(345)	(3,296)	(275)
Balance at end of period	3,090	6,020	3,090	6,020
Impact of CECL adoption
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Balance at beginning of period	$ 0	$ 0	$ 0	$ 4,840

Off-Balance-Sheet Arrangement_4

Off-Balance-Sheet Arrangements, Commitments and Contingencies (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk, at fair value	$ 965,070	$ 806,796
Commitments to extend credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk, at fair value	954,258	793,138
Standby letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off-balance-sheet risk, at fair value	$ 10,812	$ 13,658

Off-Balance-Sheet Arrangement_5

Off-Balance-Sheet Arrangements, Commitments and Contingencies Narrative (Details)	1 Months Ended		3 Months Ended		9 Months Ended
	Jan. 31, 2021USD ($)contract	May 31, 2020USD ($)contract	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets obtained in exchange for new operating lease liabilities			$ 240,000		$ 1,300,000	$ 7,900,000
Reduction of Right-of-Use Asset Obtained in Exchange for Operating Lease Liability				$ 89,000
Lessee, Operating Lease, Number of Contracts | contract	1	1
Operating lease ROU assets			15,394,000		15,394,000		$ 15,063,000
Unsettled trades to purchase securities			4,433,000	$ 7,294,000	4,433,000	$ 7,294,000	0
Unsettled trades to sell securities			0		0		0
Unsettled Issuances of Brokered CDs			$ 0		$ 0		$ 0
Operating lease
Lessee, Lease, Description [Line Items]
Operating lease ROU assets	$ 1,100,000	$ 6,600,000