Allegiance Bancshares (ABTX) 10-K 11 Mar 19 2018 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Mar. 07, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	Allegiance Bancshares, Inc.
Entity Central Index Key	0001642081
Trading Symbol	abtx
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Well-known Seasoned Issuer	No
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Public Float			$ 505.8
Entity Common Stock Shares Outstanding		21,671,955

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
ASSETS
Cash and due from banks	$ 118,771	$ 133,124
Interest-bearing deposits at other financial institutions	150,176	48,979
Total cash and cash equivalents	268,947	182,103
Available for sale securities, at fair value	337,293	309,615
Loans held for investment	3,708,306	2,270,876
Less: allowance for loan losses	(26,331)	(23,649)
Loans, net	3,681,975	2,247,227
Accrued interest receivable	17,010	12,194
Premises and equipment, net	41,717	18,477
Other real estate owned	630	365
Federal Home Loan Bank stock	10,941	12,862
Bank owned life insurance	26,480	22,422
Goodwill	223,125	39,389
Core deposit intangibles, net	26,587	3,274
Other assets	20,544	12,303
TOTAL ASSETS	4,655,249	2,860,231
Deposits:
Noninterest-bearing	1,209,300	683,110
Interest-bearing
Demand	366,905	215,499
Money market and savings	879,840	554,051
Certificates and other time	1,206,491	761,314
Total interest-bearing deposits	2,453,236	1,530,864
Total deposits	3,662,536	2,213,974
Accrued interest payable	2,812	610
Borrowed funds	225,493	282,569
Subordinated debt	48,899	48,659
Other liabilities	12,525	7,554
Total liabilities	3,952,265	2,553,366
COMMITMENTS AND CONTINGENCIES (See Note 15)	0	0
SHAREHOLDERS’ EQUITY:
Preferred stock, $1 par value; 1,000,000 shares authorized; there were no shares issued or outstanding	0	0
Common stock, $1 par value; 80,000,000 shares authorized; 21,937,740 shares outstanding at December 31, 2018 and 13,226,826 shares issued and outstanding at December 31, 2017	21,938	13,227
Capital surplus	571,803	218,408
Retained earnings	112,131	74,894
Accumulated other comprehensive (loss) income	(2,888)	336
Total shareholders’ equity	702,984	306,865
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 4,655,249	$ 2,860,231

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parentheticals) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Shares issued (in shares)	0	0
Shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	80,000,000	80,000,000
Common stock, shares issued (in shares)		13,226,826
Common stock, shares outstanding (in shares)	21,937,740	13,226,826

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
INTEREST INCOME:
Loans, including fees	$ 148,223	$ 110,331	$ 93,356
Securities:
Taxable	2,725	2,111	1,807
Tax-exempt	5,802	6,334	5,044
Deposits in other financial institutions	1,473	662	571
Total interest income	158,223	119,438	100,778
INTEREST EXPENSE:
Demand, money market and savings deposits	6,478	3,159	2,437
Certificates and other time deposits	15,478	9,060	7,044
Borrowed funds	4,788	2,922	945
Subordinated debt	2,900	629	488
Total interest expense	29,644	15,770	10,914
NET INTEREST INCOME	128,579	103,668	89,864
Provision for loan losses	4,248	13,188	5,469
Net interest income after provision for loan losses	124,331	90,480	84,395
NONINTEREST INCOME:
Gain on sale of branch assets			2,050
Gain on sale of securities		18	30
(Loss) gain on sales of other real estate and other repossessed assets	(428)	6	266
Bank owned life insurance income	579	585	626
Rebate from correspondent bank	2,609	1,327	650
Other	3,329	2,457	2,308
Total noninterest income	7,713	5,861	7,268
NONINTEREST EXPENSE:
Salaries and employee benefits	56,704	44,745	38,858
Net occupancy and equipment	5,845	5,452	4,944
Depreciation	2,132	1,637	1,627
Data processing and software amortization	5,120	4,047	2,633
Professional fees	2,009	2,926	2,234
Regulatory assessments and FDIC insurance	2,309	2,273	1,581
Core deposit intangibles amortization	1,815	781	785
Communications	1,185	983	1,055
Advertising	1,725	1,289	945
Acquisition and merger-related expenses	1,661
Other	6,282	5,829	4,596
Total noninterest expense	86,787	69,962	59,258
INCOME BEFORE INCOME TAXES	45,257	26,379	32,405
Provision for income taxes	7,948	8,747	9,554
NET INCOME	$ 37,309	$ 17,632	$ 22,851
EARNINGS PER SHARE:
Basic	$ 2.41	$ 1.34	$ 1.78
Diluted	$ 2.37	$ 1.31	$ 1.75
Deposit Account, Nonsufficient Funds Fee
NONINTEREST INCOME:
Revenue from contract with customer	$ 755	$ 685	$ 661
Deposit Account, Service Charge Fee
NONINTEREST INCOME:
Revenue from contract with customer	$ 869	$ 783	$ 677

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 37,309	$ 17,632	$ 22,851
Unrealized (loss) gain on securities:
Change in unrealized holding (loss) gain on available for sale securities during the period	(4,152)	5,213	(7,799)
Reclassification of amount realized through the sale of securities		(18)	(30)
Total other comprehensive (loss) income	(4,152)	5,195	(7,829)
Deferred tax benefit (expense) related to other comprehensive income	928	(1,807)	2,760
Other comprehensive (loss) income, net of tax	(3,224)	3,388	(5,069)
Comprehensive income	$ 34,085	$ 21,020	$ 17,782

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Capital Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balance at Dec. 31, 2015	$ 258,490	$ 12,815	$ 209,285	$ 34,411	$ 2,017	$ (38)
Balance (in shares) at Dec. 31, 2015		12,814,696
Net income	22,851			22,851
Other comprehensive income (loss)	(5,069)				(5,069)
Common stock issued in connection with the exercise of stock options, restricted stock awards and the ESPP	2,006	$ 143	1,863
Common stock issued in connection with the exercise of stock options, restricted stock awards and the ESPP (in shares)		143,645
Issuance of treasury stock	38					$ 38
Stock based compensation expense	1,501		1,501
Balance at Dec. 31, 2016	279,817	$ 12,958	212,649	57,262	(3,052)
Balance (in shares) at Dec. 31, 2016		12,958,341
Net income	17,632			17,632
Other comprehensive income (loss)	3,388				3,388
Common stock issued in connection with the exercise of stock options, restricted stock awards and the ESPP	4,248	$ 269	3,979
Common stock issued in connection with the exercise of stock options, restricted stock awards and the ESPP (in shares)		268,485
Stock based compensation expense	1,780		1,780
Balance at Dec. 31, 2017	306,865	$ 13,227	218,408	74,894	336
Balance (in shares) at Dec. 31, 2017		13,226,826
Net income	37,309			37,309
Other comprehensive income (loss)	(3,224)				(3,224)
Reclassification of amounts within AOCI to retained earnings due to tax reform	(72)			(72)
Common stock issued in connection with the exercise of stock options, restricted stock awards and the ESPP	3,750	$ 378	3,372
Common stock issued in connection with the exercise of stock options, restricted stock awards and the ESPP (in shares)		378,023
Common stock issued in connection with the acquisition of Post Oak Bancshares, Inc., net of registration expenses	358,783	$ 8,402	350,381
Common stock issued in connection with the acquisition of Post Oak Bancshares, Inc., net of registration expenses (in shares)		8,402,010
Repurchase of common stock	(2,112)	$ (69)	(2,043)
Repurchase of common stock (in shares)		(69,389)
Stock based compensation expense	1,685		1,685
Balance at Dec. 31, 2018	$ 702,984	$ 21,938	$ 571,803	$ 112,131	$ (2,888)
Balance (in shares) at Dec. 31, 2018		21,937,470

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 37,309	$ 17,632	$ 22,851
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and core deposit intangibles amortization	3,947	2,418	2,412
Provision for loan losses	4,248	13,188	5,469
Gain on the sale of securities		(18)	(30)
Deferred income tax (benefit) expense	(256)	427	(1,608)
Net amortization of premium on investments	3,533	3,427	2,785
Excess tax benefit related to the exercise of stock options	(587)	(1,149)	(371)
Bank owned life insurance	(579)	(585)	(626)
Net accretion of discount on loans	(2,702)	(632)	(1,487)
Net amortization of discount on subordinated debt	110	108	107
Net amortization of discount on certificates of deposit	(367)	(3)	(247)
Net loss (gain) on sale or write down of premises, equipment and other real estate	428	(6)	(60)
Net gain on sale of branch assets			(2,050)
Federal Home Loan Bank stock dividends	(396)	(273)	(101)
Stock based compensation expense	1,685	1,780	1,501
Increase in accrued interest receivable and other assets	(2,136)	(6,018)	(259)
Increase (decrease) in accrued interest payable and other liabilities	1,822	3,136	(851)
Net cash provided by operating activities	46,059	33,432	27,435
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities and principal paydowns of available for sale securities	2,328,864	2,007,842	2,566,082
Proceeds from sales of available for sale securities	12,701	39,125	2,500
Purchase of available for sale securities	(2,334,149)	(2,038,323)	(2,730,524)
Net change in total loans	(270,314)	(386,059)	(229,286)
Purchase of bank premises and equipment	(3,419)	(2,133)	(1,511)
Proceeds from sale of bank premises, equipment and other real estate		1,138
Net redemptions (purchases) of Federal Home Loan Bank stock	4,746	586	(10,505)
Net cash paid for the sale of branch assets			(5,250)
Net cash and cash equivalents acquired in the purchase of Post Oak Bancshares, Inc.	230,416
Net cash used in investing activities	(31,155)	(377,824)	(408,494)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase (decrease) in noninterest-bearing deposits	93,053	89,359	(20,041)
Net increase in interest-bearing deposits	64,566	254,435	157,723
Net change in short-term borrowings	(87,076)	(3,000)	235,000
Proceeds from subordinated notes issuance		39,355
Proceeds from the issuance of common stock, stock option exercises, restricted stock awards and the ESPP	3,750	4,248	2,006
Cash paid for fractional shares related to the Post Oak acquisition	(21)
Registration expenses related to common stock issued in the Post Oak acquisition	(220)
(Repurchase) issuance of treasury stock	(2,112)		38
Net cash provided by financing activities	71,940	384,397	374,726
NET CHANGE IN CASH AND CASH EQUIVALENTS	86,844	40,005	(6,333)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	182,103	142,098	148,431
CASH AND CASH EQUIVALENTS, END OF PERIOD	268,947	182,103	142,098
SUPPLEMENTAL INFORMATION:
Income taxes paid	6,650	7,850	11,400
Interest paid	$ 27,442	$ 15,442	$ 10,500

NATURE OF OPERATIONS AND SUMMAR

NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING AND REPORTING POLICIES	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING AND REPORTING POLICIES	ALLEGIANCE BANCSHARES, INC. 1. NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING AND REPORTING POLICIES Nature of Operations and Principles of Consolidation- The consolidated financial statements include Allegiance Bancshares, Inc. (“Allegiance”) and its wholly-owned subsidiary, Allegiance Bank (the “Bank”, and together with Allegiance, collectively referred to as the “Company”) provide commercial and retail loans and commercial banking services. Intercompany transactions and balances are eliminated in consolidation under U.S. generally accepted accounting principles (“GAAP”). The Company derives substantially all of its revenues and income from the operation of the Bank. Allegiance Bank is a Texas banking association which began operations in October 2007. The Company is focused on delivering a wide variety of relationship-driven commercial banking products and community-oriented services tailored to meet the needs of small to mid-sized businesses, professionals and individuals through its 28 offices, with 27 bank offices and one loan production office in the Houston metropolitan area and one office in Beaumont, just outside of the Houston metropolitan area, as of the year ended December 31, 2018. The Bank provides its customers with a variety of banking services including checking accounts, savings accounts and certificates of deposit and its primary lending products are commercial, personal, automobile, mortgage and home improvement loans. The Bank also offers safe deposit boxes, automated teller machines, drive-through services and 24-hour depository facilities. Use of Estimates— The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions based on available information. These estimates and assumptions affect the reporting of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Acquisition – On October 1, 2018, Allegiance completed the acquisition of Post Oak Bancshares, Inc. See Note 2 – Acquisitions for additional information pertaining to the Post Oak acquisition and the impact of the transaction on the Company’s consolidated financial statements. Cash and cash equivalents —Cash and cash equivalents include cash, deposits with other financial institutions with maturities not greater than one year. Net cash flows are reported for customer loan and deposit transactions. Securities —Debt securities are classified as available for sale when they might be sold before maturity. Securities available for sale are carried at fair value. Unrealized gains and losses are excluded from earnings and reported, net of tax, as a separate component of shareholders’ equity until realized. Securities within the available for sale portfolio may be used as part of the Company’s asset/liability strategy and may be sold in response to changes in interest rate risk, prepayment risk or other similar economic factors. Interest earned on these assets is included in interest income. Interest income includes amortization of purchase premium or discount. Premiums and discounts on securities are amortized on the level-yield method, except for mortgage backed securities where prepayments are anticipated. Gains and losses on sales are recorded on the trade date and determined using the specific identification method. Management evaluates debt securities for other-than-temporary impairment (“OTTI”) on at least a quarterly basis, and more frequently when economic or market conditions warrant such an evaluation. For securities in an unrealized loss position, management considers the extent and duration of the unrealized loss, and the financial condition and near-term prospects of the issuer. Management also assesses whether it intends to sell, or it is more likely than not that it will be required to sell, a security in an unrealized loss position before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the entire difference between amortized cost and fair value is recognized as impairment through earnings. For debt securities that do not meet the aforementioned criteria, the amount of impairment is split into two components as follows: (1) OTTI related to credit loss, which must be recognized in the income statement and (2) OTTI related to other factors, which is recognized in other comprehensive income, net of applicable taxes. The credit loss is defined as the difference between the present value of the cash flows expected to be collected and the amortized cost basis. The previous amortized cost bases less the OTTI recognized in earnings shall become the new amortized cost basis of the security. Loans Held for Investment —Loans held for investment are those that management has the intent and ability to hold for the foreseeable future or until maturity or payoff are reported at the principal balance outstanding, net of deferred loan fees and costs, and an allowance for loan losses. Loans are typically secured by specific items of collateral including business assets, consumer assets and commercial and residential real estate. Commercial loans are expected to be repaid from cash flow from operations of businesses. Interest income is accrued on the unpaid principal balance. Acquired Loans — A cquired loans are recorded at fair value at the date of acquisition with no initial valuation allowance based on a discounted cash flow methodology that considers various factors including the type of loan and related collateral, classification status, fixed or variable interest rate, term of loan and whether or not the loan was amortizing, and a discount rate reflecting the Company’s assessment of risk inherent in the cash flow estimates. Certain larger purchased loans are individually evaluated while certain purchased loans are grouped together according to similar risk characteristics and are treated in the aggregate when applying various valuation techniques. These cash flow evaluations are inherently subjective as they require material estimates, all of which may be susceptible to significant change. Loans acquired in a business combination that have evidence of deterioration of credit quality since origination and for which it is probable, at acquisition, that the Company will be unable to collect all contractually required payments receivable are considered purchased credit impaired (“PCI”). PCI loans are individually evaluated and recorded at fair value at the date of acquisition with no initial valuation allowance based on a discounted cash flow methodology that considers various factors including the type of loan and related collateral, classification status, fixed or variable interest rate, term of loan and whether or not the loan was amortizing, and a discount rate reflecting the Company’s assessment of risk inherent in the cash flow estimates. Increases in expected cash flows, including prepayments, subsequent to the initial investment are recognized prospectively through adjustment of the yield on the loan over its remaining life. Decreases in expected cash flows are recognized as impairment. Valuation allowances on PCI loans reflect only losses incurred after the acquisition (meaning the present value of all cash flows expected at acquisition that ultimately are not to be received). For acquired loans not deemed credit-impaired at acquisition, the differences between the initial fair value and the unpaid principal balance are recognized as interest income on a level-yield basis over the lives of the related loans. Subsequent to the acquisition date, methods utilized to estimate the required allowance for loan losses for these loans is similar to originated loans; however, a provision for credit losses will be recorded only to the extent the required allowance exceeds any remaining purchase discounts. Once an acquired loan undergoes new underwriting and meets the criteria for a new loan, such as in the case of a loan renewal, any remaining fair value adjustments are accreted into interest income and the loan establishes a new amortized cost basis that is fully subject to the Company's allowance for loan loss methodology. Nonrefundable Fees and Costs Associated with Lending Activities — Loan commitment and loan origination fees, and certain direct origination costs, are deferred and recognized in interest income as an adjustment to yield without anticipating prepayments using the interest method over the related loan life or; if the commitment expires unexercised, balances are recognized in income upon expiration of the commitment. Nonperforming and Past Due Loans —The Company has several procedures in place to assist it in maintaining the overall quality of its loan portfolio. The Company has established underwriting guidelines to be followed by its officers, and monitors its delinquency levels for any negative or adverse trends. There can be no assurance, however, that the Company’s loan portfolio will not become subject to increasing pressures from deteriorating borrower credit due to general economic conditions or other factors. Past due status is based on the contractual terms of the loan. Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. The Company generally classifies a loan as nonperforming, automatically places the loan on nonaccrual status, ceases accruing interest and reverses all unpaid accrued interest against interest income, when, in management’s opinion, the borrower may be unable to meet payment obligations, when the payment of principal or interest on a loan is delinquent for 90 days, as well as when required by regulatory provisions, unless the loan is in the process of collection and the underlying collateral fully supports the carrying value of the loan. Any payments received on nonaccrual loans are applied first to outstanding loan amounts. Interest income is subsequently recognized only to the extent cash payments are received in excess of principal due. Any excess is treated as recovery of lost interest. Loans are returned to accrual status when all of the principal and interest amounts contractually due are brought current and future payments are reasonably assured. In all cases, loans are placed on nonaccrual or charged-off at an earlier date if collection of principal or interest is considered doubtful. If the decision is made to continue accruing interest on the loan, periodic reviews are made to confirm the accruing status of the loan. Nonaccrual loans and loans past due 90 days include both smaller balance homogeneous loans that are collectively evaluated for impairment and individually classified impaired loans. When available information confirms that specific loans, or portions thereof, are uncollectible, these amounts are charged-off against the allowance. All loan types are considered delinquent after 30 days past due and are typically charged-off or charged-down no later than 120 days past due, with consideration of, but not limited to, the following criteria in determining the need and optional timing of the charge-off or charge-down: (1) the Bank is in the process of repossession or foreclosure and there appears to be a likely deficiency, (2) the collateral securing the loan has been sold and there is an actual deficiency, (3) the Bank is proceeding with lengthy legal action to collect its balance, (4) the borrower is unable to be located or (5) the borrower has filed bankruptcy. Charge-offs occur when the Company confirms a loss on a loan. Troubled debt restructurings (TDRs) —Loans on which terms have been modified resulting in a concession have been granted because of a borrower’s financial difficulty are considered troubled debt restructurings and classified as impaired. The restructuring of a loan is considered a troubled debt restructuring if both (1) the borrower is experiencing financial difficulties and (2) the creditor has granted a concession that it would not otherwise consider. Concessions may include reductions of interest rates to a below market interest rate: extension of the terms of the debt, principal forgiveness, restructuring the payment of the debt obligation; and other actions intended to minimize potential losses. Subsequent to identification as a troubled debt restructuring such loans are then evaluated for impairment on an individual basis whereby the loans are measured at the present value of estimated future cash flows using the loan’s effective rate at inception. If a troubled debt restructuring is considered to be a collateral dependent loan: the loan is reported, net, at the fair value of the collateral. Impaired Loans —On a continuous basis, loans are evaluated for impairment classification. Loans are considered impaired when based on current information and events, it is probable the Company will be unable to collect all amounts due in accordance with the original contractual terms of the loan agreement including scheduled principal and interest payments. Impairment is evaluated in total for smaller-balance loans of a similar nature and on an individual loan basis for other loans. If a loan is impaired, a specific valuation allowance is allocated, if necessary, so that the loan is reported net, at the present value of estimated future cash flows using the loan’s existing rate or at the fair value of collateral if repayment is expected solely from the collateral. Factors considered by management in determining impairment include payment status, collateral value and the probability of collecting scheduled principal and interest payments when due. Loans that experience insignificant payment delays and payment shortfalls generally are not classified as impaired. Management determines the significance of payment delays and payment shortfalls on case-by-case basis taking into consideration all of the circumstances surrounding the loan and the borrower including the length of the delay, the reasons for the delay, the borrower’s prior payment record and the amount of the shortfall in relation to the principal and interest owed. Allowance for Loan Losses —The allowance for loan losses is a valuation allowance that is established through charges to earnings in the form of a provision for loan losses. The amount of the allowance for loan losses is affected by the following: (1) charge-offs of loans that decrease the allowance, (2) subsequent recoveries on loans previously charged off that increase the allowance and (3) provisions for loan losses charged to income that increase the allowance. Throughout the year, management estimates the probable incurred losses in the loan portfolio to determine if the allowance for loan losses is adequate to absorb such losses. The allowance for loan losses consists of specific and general components. The specific component relates to loans that are individually classified as impaired. The Company follows a loan review program to evaluate the credit risk in the loan portfolio. Loans that have been identified as impaired are generally reviewed on a quarterly basis in order to determine whether a specific reserve is required. The general component covers non-impaired loans and is based on industry and Company specific historical loan loss experience, volume, growth and composition of the loan portfolio, the evaluation of the Company’s loan portfolio through its internal loan review process, general current economic conditions both internal and external to the Company that may affect the borrower’s ability to pay, value of collateral and other qualitative relevant risk factors. Based on a review of these estimates, the allowance for loan losses is adjusted to a level determined to be adequate. Estimates of loan losses are inherently subjective as it involves an exercise of judgment. It is the judgment of management that the allowance for loan losses reflected in the consolidated balance sheets is adequate to absorb probable losses that exist in the loan portfolio as of the reporting date. For troubled debt restructurings that subsequently default, the Company determines the amount of reserve in accordance with the accounting policy for the allowance for loan losses. The Company assesses the exposure for each modification, either by collateral discounting or by calculation of the present value of future cash flows, and determines if a specific allocation to the allowance for loan losses is needed. Once an obligation has been restructured because of such credit problems, it continues to be considered a troubled debt restructuring until paid in full. The Company returns troubled debt restructurings to accrual status only if (1) all contractual amounts due can reasonably be expected to be repaid within a prudent period and (2) repayment has been in accordance with the contract for a sustained period, typically at least twelve months. Loans acquired in business combinations are initially recorded at fair value, which includes an estimate of loan losses expected to be realized over the remaining lives of the loans. Therefore no corresponding allowance for loan losses is recorded for these loans at acquisition. Methods utilized to estimate any subsequently required allowance for loan losses for acquired loans not deemed credit-impaired at acquisition are similar to originated loans. However, the estimate of loss is based on the unpaid principal balance and then compared to any remaining unaccreted purchase discount. To the extent that the calculated loss is greater than the remaining unaccreted purchase discount, an allowance is recorded for such difference. Premises and Equipment —Premises and equipment are carried at cost less accumulated depreciation. Depreciation expense is calculated principally using the straight-line method over the estimated useful lives of the assets which range from 3 to 40 years. Leasehold improvements are amortized using the straight-line method over the periods of the leases or the estimated useful lives, whichever is shorter. Land is carried at cost. Other Real Estate Owned —Assets acquired through or instead of loan foreclosure are held for sale and are initially recorded at fair value less estimated selling costs when acquired, establishing a new cost basis. Costs after acquisition are generally expensed. If the fair value of the asset declines, a write-down is recorded through expense. The valuation of foreclosed assets is subjective in nature and may be adjusted in the future because of changes in economic conditions. At December 31, 2018, the $630 thousand balance of other real estate owned was a residential real estate property. Federal Home Loan Bank (“FHLB”) Stock— The Bank is a member of the FHLB system. Members are required to own a certain amount of stock based on the level of borrowings and other factors and may invest in additional amounts. FHLB stock is carried at cost, classified as a restricted security and periodically evaluated for impairment based on ultimate recovery of par value. Both cash and stock dividends are reported as income. Bank Owned Life Insurance— The Company purchased bank owned life insurance policies on certain key executives and acquired life insurance policies in conjunction with the acquisitions of F&M Bancshares and Post Oak. Bank owned life insurance is recorded at the amount that can be realized under the insurance contract at the balance sheet date, which is the cash surrender value, which is the most reasonable estimate of fair value, adjusted for other charges or other amounts due that are probable at settlement. Goodwill —Goodwill resulting from business combinations is generally determined as the excess of the fair value of the consideration transferred, plus the fair value of any noncontrolling interests in the acquiree, over the fair value of the net assets acquired and liabilities assumed as of the acquisition date. Goodwill is determined to have an indefinite useful life and is not amortized, but is tested for impairment at least annually or more frequently if events and circumstances exists that indicate that a goodwill impairment test should be performed. The Company performs its annual impairment test on October 1. Goodwill is the only intangible asset with an indefinite life on the Company’s balance sheet. Core Deposit Intangibles —Core deposit and acquired customer relationship intangibles arising from acquisitions are amortized using a straight-line amortization method over their estimated useful lives, which is seven to ten years. Borrowed Funds —The Company has a credit agreement with another financial institution. The Company pledged its shares in the Bank’s stock as collateral for the borrowing. Loan Commitments and Related Financial Instruments —Financial instruments include off-balance sheet credit instruments, such as commitments to extend credit, issued to meet customer financing needs. The face amount for these items represents the exposure to loss before considering customer collateral or ability to repay. Such financial instruments are recorded when they are funded. Stock Based Compensation —Compensation cost is recognized for stock options and restricted stock awards issued to employees, based on the fair value of these awards at the date of grant. The expense associated with stock based compensation is recognized over the required service period, generally defined as the vesting period of each individual arrangement. For awards with graded vesting, compensation cost is recognized on a straight-line basis over the requisite service period for the entire award. The fair value of stock options granted and employee stock purchase plan awards are estimated at the date of grant using the Black-Scholes option-pricing model and the market price of the Company’s common stock on the date prior to the grant date is used to value restricted stock awards. Employee Stock Purchase Plan —The cost of shares issued in the ESPP, but not allocated to participants, is shown as a reduction of shareholder’s equity. Compensation expense is based on the market price of the shares as they are committed to be released to participant accounts. Income Taxes —Income tax expense is the total of the current year income tax due and the change in deferred tax assets or liabilities. Deferred tax assets and liabilities are recognized for the estimated tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and are recorded in other assets on the Company’s consolidated balance sheets. The Company records uncertain tax positions on the basis of a two-step process whereby (1) the Company determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more likely than not recognition threshold, the Company recognizes the largest amount of tax benefit that is greater than 50 percent likely of being realized upon ultimate settlement with the related tax authority. For tax positions not meeting the more likely than not test, no tax benefit is recorded. Any interest and/or penalties related to income taxes are reported as a component of income tax expense. The Company files a consolidated federal income tax return. Comprehensive income —Comprehensive income consists of net income and other comprehensive income which includes unrealized gains and losses on securities available for sale which are also recognized as separate components of equity. Fair Value of Financial Instruments —Fair values of financial instruments are estimated using relevant market information and other assumptions, as more fully disclosed in a separate note. Fair value estimates involve uncertainties and matters of significant judgment regarding interest rates, credit risk, prepayments and other factors, especially in the absence of broad markets for particular items. Changes in assumptions or in market conditions could significantly affect these estimates. Operating Segments— While management monitors the revenue streams of the various products and services, operations are managed and financial performance is evaluated on a Company-wide basis. All of the financial service operations are considered by management to be aggregated in one reportable operating segment. Reclassifications —Some items in the prior year financial statements were reclassified to conform to the current presentation. Reclassifications had no effect on prior year net income or shareholders’ equity. Earnings per Common Share —Basic earnings per common share is calculated as net income divided by the weighted average number of common shares outstanding during the period. Diluted earnings per common share includes the dilutive effect of additional potential common shares issuable under stock options, restricted stock awards and the Employee Stock Purchase Plan. Loss Contingencies —Loss contingencies, including claims and legal actions arising in the ordinary course of business, are recorded as liabilities when the likelihood of loss is probable and an amount or range of loss can be reasonably estimated. Management does not believe there are such matters that will have a material effect on the financial statements. Dividend Restrictions —Banking regulations require maintaining certain capital levels and may limit the dividends paid by the Bank to Allegiance or by Allegiance to its shareholders. In addition, Allegiance's credit agreement with another financial institution also limits its ability to pay dividends. Revenue from Contracts with Customers -The Company records revenue from contracts with customers in accordance with Accounting Standards Codification Topic 606, “Revenue from Contracts with Customers” (“Topic 606”). Under Topic 606, the Company must identify the contract with a customer, identify the performance obligations in the contract, determine the transaction price, allocate the transaction price to the performance obligations in the contract, and recognize revenue when (or as) the Company satisfies a performance obligation. Significant revenue has not been recognized in the current reporting period that results from performance obligations satisfied in previous periods. The Company’s primary sources of revenue are derived from interest and dividends earned on loans, investment securities, and other financial instruments that are not within the scope of Topic 606. The Company has evaluated the nature of its contracts with customers and determined that further disaggregation of revenue from contracts with customers into more granular categories beyond what is presented in the Consolidated Statements of Income was not necessary. The Company generally fully satisfies its performance obligations on its contracts with customers as services are rendered and the transaction prices are typically fixed; charged either on a periodic basis or based on activity. Because performance obligations are satisfied as services are rendered and the transaction prices are fixed, the Company has made no significant judgments in applying the revenue guidance prescribed in ASC 606 that affect the determination of the amount and timing of revenue from contracts with customers New Accounting Standards Adoption of New Accounting Standards ASU 2014-09 “Revenue from Contracts with Customers (Topic 606).” ASU 2014-09 supersedes the revenue recognition requirements in Revenue Recognition (Topic 605), and most industry-specific guidance throughout the Industry Topics of the Codification. The core principle of ASU 2014-09 is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new standard was effective for the Company on January 1, 2018 and management has completed its analysis of the impact of the standard’s adoption. Adoption of the ASU did not have a significant impact on the Company’s consolidated financial statements and related disclosures. The Company’s primary sources of revenue are derived from interest and dividends earned on loans, investment securities, and other financial instruments that are not within the scope of ASU 2014-09. The Company’s revenue recognition pattern for revenue streams within the scope of ASU 2014-09, including but not limited to service charges on deposit accounts and gains/losses on the sale of OREO, did not change significantly from current practice. The standard permits the use of either the full retrospective or modified retrospective transition method. The Company elected to use the modified retrospective transition method which requires application of ASU 2014-09 to uncompleted contracts at the date of adoption; however, periods prior to the date of adoption will not be retrospectively revised as the impact of the ASU on uncompleted contracts at the date of adoption was not material. ASU No. 2016-01, “Financial Instruments - Overall (Subtopic 825-10): Recognition of Financial Assets and Financial Liabilities.” ASU 2016-01 makes targeted amendments to fair value measurement and disclosure guidance. ASU 2016-01 requires equity investments (other than equity method investments) to be measured at fair value with changes in fair value recognized in net income. This change is only applied if a readily determinable fair value can be obtained. Adoption of the standard also resulted in the use of an exit price rather than an entrance price to determine the fair value of loans not measured at fair value on a non-recurring basis in the consolidated balance sheets. See Note 7 – Fair Value disclosures for further information regarding the valuation of these loans. ASU 2016-01 became effective for the Company on January 1, 2018. ASU 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business,” (“ASU 2017-01”) to improve such definition and, as a result, assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or as business combinations. The definition of a business impacts many areas of accounting including acquisitions, disposals, goodwill and consolidation. ASU 2017-01 became effective for the Company on January 1, 2018 and is to be applied under a prospective approach. The Company expects the adoption of this new guidance to impact the determination of whether future acquisitions are considered business combinations or asset purchases. Newly Issued But Not Yet Effective Accounting Standards ASU 2016-02 “Leases (Topic 842)." ASU 2016-02 will, among other things, require lessees to recognize a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. ASU 2016-02 does not significantly change lease accounting requirements applicable to lessors; however, certain changes were made to align, where necessary, lessor accounting with the lessee accounting model and ASC Topic 606, “Revenue from Contracts with Customers.” The new standard was adopted by the Company on January 1, 2019. ASU 2016-02 provides for a modified retrospective transition approach requiring lessees to recognize and measure leases on the balance sheet at the beginning of either the earliest period presented or as of the beginning of the period of adoption. The Company has elected to apply ASU 2016-02 as of the beginning of the period of adoption (January 1, 2019) and will not restate comparative periods. The Company expects that the adoption of ASU 2016-02 will result in the recognition of lease liabilities totaling $15,000,000 to $17,000,000 and the recognition of right-of-use assets totaling $15,000,000 to $17,000,000, which results in an estimated 5 basis point decrease in the tier 1 capital to risk weighted assets ratio as of the date of adoption. The initial balance sheet gross up upon adoption is primarily related to operating leases of certain real estate properties. The Company has no material leasing arrangements for which it is the lessor of property or equipment. The Company has made an accounting policy election to not apply the recognition requirements in the new standard to short-term leases.

ACQUISITIONS

ACQUISITIONS	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
ACQUISITIONS	2. ACQUISITIONS Acquisitions are accounted for using the acquisition method of accounting. Accordingly, the assets and liabilities of an acquired entity are recorded at their fair value at the acquisition date. The excess of the purchase price over the estimated fair value of the net assets is recorded as goodwill. The results of operations for an acquisition have been included in the Company’s consolidated financial results beginning on the respective acquisition date. The measurement period for the Company to determine the fair values of acquired identifiable assets and assumed liabilities will end at the earlier of (1) twelve months from the date of the acquisition or (2) as soon as the Company receives the information it was seeking about facts and circumstances that existed as of the acquisition date or learns that more information is not obtainable. The following acquisition was completed on the date indicated below: 2018 Acquisition Acquisition of Post Oak Bancshares, Inc. —On October 1, 2018, the Company completed the acquisition of Post Oak Bancshares, Inc. (“Post Oak”) and its wholly-owned subsidiary Post Oak Bank, N.A. headquartered in Houston, Texas. Post Oak operated thirteen bank offices, twelve located throughout the greater Houston metropolitan area and one in Beaumont, just outside of the Houston metropolitan area. The Company acquired Post Oak to further expand its Houston, Texas area market. Goodwill resulted from a combination of expected operational synergies and an enhanced branching network. Goodwill is not expected to be deductible for tax purposes. Pursuant to the merger agreement, the Company issued 8,402,010 shares of Company common stock for all outstanding shares of Post Oak common stock and paid $21 thousand in cash for any fractional shares held by Post Oak shareholders. Additionally, all outstanding Post Oak options were assumed by Allegiance and converted using the 0.7017 exchange ratio to 299,352 options at a weighted average exercise price of $12.83 per option. Based on the $41.70 per share closing price of Allegiance common stock on September 28, 2018, the total transaction value was approximately $359.0 million. The acquisition was accounted for under the acquisition method of accounting in accordance with ASC Topic 805, Business Combinations. The Company recognized goodwill of $183.7 million which is calculated as the excess of both the consideration exchanged and liabilities assumed as compared to the fair value of identifiable assets acquired, none of which is expected to be deductible for tax purposes. The intangible assets recognized in the transaction will be amortized utilizing an accelerated method over their ten year estimated useful lives. The initial accounting for the acquisition has not been completed because the fair values of the assets acquired and liabilities assumed have not yet been finalized. As of October 1, 2018, the Company finalized its valuation of all assets and liabilities acquired, resulting in no changes to preliminary acquisition accounting adjustments. A summary of the final purchase price allocation is as follows (in thousands): Fair value of consideration paid: Common shares issued (8,402,010 shares) $ 350,364 Stock options issued (299,352) 8,639 Cash in lieu of fractional shares 21 Total consideration paid $ 359,024 Fair value of assets acquired: Cash and cash equivalents $ 230,416 Investment securities 42,779 Loans 1,164,279 Premises and equipment 21,988 Core deposit intangibles 25,128 Other assets 18,078 Total assets acquired $ 1,502,668 Fair value of liabilities assumed: Deposits $ 1,291,310 Other borrowed funds 30,000 Other liabilities 6,070 Total liabilities assumed 1,327,380 Fair value of net assets acquired $ 175,288 Goodwill resulting from acquisition $ 183,736 The fair value of net assets acquired includes fair value adjustments to certain acquired loans that were not considered impaired as of the acquisition date. The fair value adjustments were determined using discounted contractual cash flows. The following presents details of all loans acquired as of October 1, 2018: Contractual Balance Fair Value Discount (Dollars in thousands) Commercial and industrial $ 221,098 $ 217,204 $ (3,894 ) Real estate: Commercial real estate (including multi-family residential) 450,947 443,512 (7,435 ) Commercial real estate construction and land development 167,386 165,387 (1,999 ) 1-4 family residential (including home equity) 288,304 285,099 (3,205 ) Residential construction 23,812 23,812 — Consumer and other 29,684 29,267 (417 ) Total loans $ 1,181,231 $ 1,164,281 $ (16,950 ) In connection with the Post Oak acquisition, the Company acquired loans both with and without evidence of credit quality deterioration since origination. The acquired loans were initially recorded at fair value with no carryover of any allowance for loan losses. Acquired loans were segregated between those considered to be purchased credit impaired (“PCI”) loans and those without credit impairment at acquisition. PCI Loans. The following presents information at the acquisition date for PCI loans acquired in the transaction (dollars in thousands): Contractually required principal and interest payments $ 28,340 Contractual cash flows not expected to be collected (nonaccretable difference) 3,163 Expected cash flows at acquisition 25,177 Interest component of expected cash flows (accretable yield) 495 Fair value of loans acquired with deterioration of credit quality $ 24,682 Non-PCI Loans. The following table presents information at the acquisition date for non-PCI loans acquired in the transaction (in thousands): Contractually required principal and interest payments $ 1,153,317 Accretable discount 13,293 Fair value at acquisition $ 1,140,024 The following table presents unaudited pro forma financial information as if the acquisition had occurred at the beginning of 2017. Post Oak’s results of operations were included in the Company’s results beginning October 1, 2018. The pro forma financial information is not necessarily indicative of the results of operations that would have occurred had the transaction been effected on the assumed dates. For the Years Ended December 31, 2018 2017 (Dollars in thousands, except per share data) Net interest income $ 170,801 $ 165,612 Noninterest income 10,060 9,543 Net income 41,807 35,107 Basic earnings per common share 2.70 1.63 Diluted earnings per common share 2.65 1.61 To determine pro forma information, the Company adjusted its year ended December 31, 2018 and 2017 historical results to include the historical results for Post Oak for the year ended December 31, 2017 and the nine months ended September 30, 2018. The pro forma information includes acquisition accounting adjustments to interest on loans, certificates of deposit and subordinated debt, difference in the rate of borrowed funds, amortization of intangibles arising from the transaction and the related income tax effects. Earnings of Post Oak since the acquisition date have not been disclosed as the acquired company was merged into the Company and separate financial information is not readily available. The Company incurred approximately $1.7 million of pre-tax acquisition and merger-related expenses during the year ended December 31, 2018 related to the Post Oak acquisition. The acquisition and merger-related expenses are reflected on the Company’s income statement for 2018 but are excluded from the calculation of pro forma income above.

GOODWILL AND CORE DEPOSIT INTAN

GOODWILL AND CORE DEPOSIT INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
GOODWILL AND CORE DEPOSIT INTANGIBLE ASSETS	3. GOODWILL AND CORE DEPOSIT INTANGIBLES Changes in the carrying amount of the Company’s goodwill and core deposit intangibles were as follows: Core Deposit Goodwill Intangible Assets (Dollars in thousands) Balance as of January 1, 2016 $ 39,389 $ 5,230 Sale of branch assets — (390 ) Amortization — (785 ) Balance as of December 31, 2016 39,389 4,055 Amortization — (781 ) Balance as of December 31, 2017 39,389 3,274 Acquisition of Post Oak Bancshares, Inc. 183,736 25,128 Amortization — (1,815 ) Balance as of December 31, 2018 $ 223,125 $ 26,587 Goodwill is recorded on the acquisition date of an entity. During the measurement period, the Company may record subsequent adjustments to goodwill for provisional amounts recorded at the acquisition date. The Company performed its annual impairment test on October 1, 2018 and determined no impairment was necessary. The estimated aggregate future amortization expense for core deposit intangibles remaining as of December 31, 2018 is as follows (dollars in thousands): 2019 $ 4,712 2020 3,922 2021 3,296 2022 3,003 2023 2,323 Thereafter 9,331 Total $ 26,587

CASH AND DUE FROM BANKS

CASH AND DUE FROM BANKS	12 Months Ended
	Dec. 31, 2018
Cash And Cash Equivalents [Abstract]
CASH AND DUE FROM BANKS	4. CASH AND DUE FROM BANKS The Bank can be required by the Federal Reserve Bank of Dallas to maintain average reserve balances. “Cash and due from banks” in the consolidated balance sheets included a restricted amount of $27.7 million at December 31, 2018. The Bank was not required to maintain reserve balances at December 31, 2017 or 2016.

SECURITIES

SECURITIES	12 Months Ended
	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
SECURITIES	5. The amortized cost and fair value of investment securities were as follows: December 31, 2018 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value (Dollars in thousands) Available for Sale U.S. Government and agency securities $ 8,570 $ 161 $ (46 ) $ 8,685 Municipal securities 219,068 1,258 (3,541 ) 216,785 Agency mortgage-backed pass-through securities 66,987 237 (1,029 ) 66,195 Corporate bonds and other 46,303 15 (690 ) 45,628 Total $ 340,928 $ 1,671 $ (5,306 ) $ 337,293 December 31, 2017 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value (Dollars in thousands) Available for Sale U.S. Government and agency securities $ 8,507 $ 232 $ (24 ) $ 8,715 Municipal securities 222,330 2,470 (1,842 ) 222,958 Agency mortgage-backed pass-through securities 32,014 159 (361 ) 31,812 Corporate bonds and other 46,247 62 (179 ) 46,130 Total $ 309,098 $ 2,923 $ (2,406 ) $ 309,615 As of December 31, 2018, the Company's management did not expect to sell any securities classified as available for sale with material unrealized losses; and the Company believes that it is more likely than not it will not be required to sell any of these securities before their anticipated recovery at which time the Company will receive full value for the securities. The fair value is expected to recover as the securities approach their maturity date or repricing date or if market yields for such investments decline. Management does not believe any of the securities are impaired due to reasons of credit quality. Accordingly, as of December 31, 2018, management believes the unrealized losses in the previous table are temporary and no other than temporary impairment loss has been realized in the Company’s consolidated statements of income. The amortized cost and fair value of investment securities at December 31, 2018, by contractual maturity, are shown below. Expected maturities may differ from contractual maturities if borrowers have the right to call or prepay obligations at any time with or without call or prepayment penalties. Amortized Fair Cost Value (Dollars in thousands) Due in one year or less $ 14,877 $ 14,823 Due after one year through five years 73,675 72,790 Due after five years through ten years 87,391 86,880 Due after ten years 97,998 96,605 Subtotal 273,941 271,098 Agency mortgage-backed pass through securities 66,987 66,195 Total $ 340,928 $ 337,293 Securities with unrealized losses segregated by length of time such securities have been in a continuous loss position are as follows: December 31, 2018 Less than 12 Months More than 12 Months Total Estimated Unrealized Estimated Unrealized Estimated Unrealized Fair Value Losses Fair Value Losses Fair Value Losses (Dollars in thousands) Available for Sale U.S. Government and agency securities $ 999 $ — $ 1,417 $ (46 ) $ 2,416 $ (46 ) Municipal securities 10,140 (29 ) 136,934 (3,512 ) 147,074 (3,541 ) Agency mortgage-backed pass- through securities 17,168 (209 ) 22,819 (820 ) 39,987 (1,029 ) Corporate bonds and other 13,634 (35 ) 29,014 (655 ) 42,648 (690 ) Total $ 41,941 $ (273 ) $ 190,184 $ (5,033 ) $ 232,125 $ (5,306 ) December 31, 2017 Less than 12 Months More than 12 Months Total Estimated Unrealized Estimated Unrealized Estimated Unrealized Fair Value Losses Fair Value Losses Fair Value Losses (Dollars in thousands) Available for Sale U.S. Government and agency securities $ 3,110 $ (9 ) $ 595 $ (15 ) $ 3,705 $ (24 ) Municipal securities 42,249 (517 ) 56,483 (1,325 ) 98,732 (1,842 ) Agency mortgage-backed pass- through securities 13,238 (105 ) 8,921 (256 ) 22,159 (361 ) Corporate bonds and other 30,203 (179 ) — — 30,203 (179 ) Total $ 88,800 $ (810 ) $ 65,999 $ (1,596 ) $ 154,799 $ (2,406 ) There were no realized losses on the securities in the portfolio as the Company believes these securities are temporarily impaired due to changes in market interest rates. The majority of the securities in an unrealized loss position are related to the Company's municipal securities. During 2018, the Company acquired $42.8 million and sold $12.7 million of securities acquired in the Post Oak transaction. No gains or losses were recognized. During 2017, the Company sold $39.1 million in securities and recorded a net gain on the sales of $18 thousand. The Company sold $2.5 million in securities during 2016 and recorded a gain on the sale of $30 thousand. At December 31, 2018 and 2017, the Company did not own securities of any one issuer, other than the U.S. government and its agencies, in an amount greater than 10% of the consolidated shareholders’ equity at such respective dates. The carrying value of pledged securities $28.9 million and $5.0 million at December 31, 2018 and 2017, respectively. The increase in pledged securities during the year ended December 31, 2018 was primarily due to $25.9 million of pledged securities that were acquired from Post Oak. The majority of the securities were pledged to collateralize public fund deposits.

LOANS AND ALLOWANCE FOR LOAN LO

LOANS AND ALLOWANCE FOR LOAN LOSSES	12 Months Ended
	Dec. 31, 2018
Loans And Allowance For Loan Losses [Abstract]
LOANS AND ALLOWANCE FOR LOAN LOSSES	6. LOANS AND ALLOWANCE FOR LOAN LOSSES The loan portfolio balances, net of unearned income and fees, consist of various types of loans primarily all made to borrowers located within Texas and are classified by major type as follows: December 31, 2018 2017 (Dollars in thousands) Commercial and industrial $ 702,037 $ 457,129 Mortgage warehouse 48,274 69,456 Real estate: Commercial real estate (including multi- family residential) 1,650,912 1,080,247 Commercial real estate construction and land development 430,128 243,389 1-4 family residential (including home equity) 649,311 301,219 Residential construction 186,411 109,116 Consumer and other 41,233 10,320 Total loans 3,708,306 2,270,876 Allowance for loan losses (26,331 ) (23,649 ) Loans, net $ 3,681,975 $ 2,247,227 (1) Mortgage warehouse loans are to unaffiliated mortgage loan originators collateralized by mortgage promissory notes which are segregated in the Company’s mortgage warehouse portfolio. These promissory notes originated by the Company’s mortgage warehouse customers carry terms and conditions as would be expected in the competitive permanent mortgage market and serve as collateral under a traditional mortgage warehouse arrangement whereby such promissory notes are warehoused under a revolving credit facility to allow for the end investor (or purchaser) of the note to receive a complete loan package and remit funds to the bank. The maturity of each revolving line of credit facility is normally less than 24 months, while the promissory notes that are warehoused under such facilities may have a much shorter length of time outstanding. For mortgage promissory notes secured by residential property, the warehouse time is normally 10 to 20 days. For mortgage promissory notes secured by commercial property, the warehouse time is normally 40 to 50 days. The funded balance of the mortgage warehouse portfolio can have significant fluctuation based upon market demand for the product, level of home sales and refinancing activity, market interest rates and velocity of end investor processing times. Loan Origination/Risk Management The Company has certain lending policies and procedures in place that are designed to maximize loan income within an acceptable level of risk. The Company maintains an independent loan review department that reviews and validates the credit risk program on a periodic basis. In addition, an independent third party loan review is performed on a semi-annual basis. (i) Commercial and Industrial Loans. (ii) Commercial Real Estate. The Company’s nonowner-occupied and multi-family commercial real estate lending typically involves higher loan principal amounts and the repayment of these loans is dependent, in large part, on sufficient income from the properties securing the loans to cover operating expenses and debt service. The Company generally requires the borrower to have had an existing relationship with the Company and have a proven record of success. In addition, these loans are generally guaranteed by individual owners of the borrower and have typically lower loan to value ratios. Loans secured by owner-occupied properties generally involve less risk and represented 51.4% of the outstanding principal balance of the Company’s commercial real estate loans at December 31, 2018. The Company is dependent on the cash flows of the business occupying the property and its owners and requires these loans to be secured by property with adequate margins and to be guaranteed by the individual owners. The Company’s owner-occupied commercial real estate loans collateralized by first liens on real estate typically have fixed interest rates and amortize over a 10 to 20 year period. (iii) Construction and Land Development Loans. (iv) Residential Real Estate Loans. (v) Consumer and Other Loans. Acquired Loans PCI loans The carrying amount of PCI loans included in the consolidated balance sheet and the related outstanding balance owed at December 31, 2018 are presented in the table below (in thousands): PCI loans: Outstanding balance at December 31, 2018 $ 26,862 Less: Discount 3,599 Recorded investment at December 31, 2018 $ 23,263 Changes in the accretable yield for PCI loans for the year ended December 31, 2018 were as follows (in thousands): Balance at beginning of period $ — Additions 495 Reclassifications from nonaccretable — Accretion 59 Balance at December 31, 2018 $ 436 Non-PCI Loans. The carrying amount of Non-PCI loans included in the consolidated balance sheet and the related outstanding balance owed at December 31, 2018 are presented in the table below (in thousands). Non-PCI loans: Outstanding balance at December 31, 2018 $ 1,124,342 Less: Discount 10,650 Recorded investment at December 31, 2018 $ 1,113,692 Changes in the discount accretion for Non-PCI loans for the years ended December 31, 2018 were as follows (in thousands): Balance at beginning of period $ — Additions 13,293 Reclassifications from nonaccretable — Accretion 2,643 Balance at December 31, 2018 $ 10,650 Concentrations of Credit The vast majority of the Company’s lending activity occurs in and around the Houston, Texas area. The Company’s loans are primarily loans secured by real estate, including commercial and residential construction, owner-occupied and nonowner-occupied and multi-family commercial real estate, raw land and other real estate based loans. Related Party Loans As of December 31, 2018 and 2017, loans outstanding to directors, officers and their affiliates totaled $7.9 million and $4.4 million, respectively. An analysis of activity with respect to these related-party loans is as follows: 2018 (Dollars in thousands) Beginning balance on January 1 $ 4,368 New loans and reclassified related loans 5,003 Repayments (1,501 ) Ending balance on December 31 $ 7,870 Nonaccrual and Past Due Loans An aging analysis of the recorded investment in past due loans, segregated by class of loans, is as follows: December 31, 2018 Loans Past Due and Still Accruing 30-89 90 or More Total Past Nonaccrual Current Total Days Days Due Loans Loans Loans Loans (Dollars in thousands) Commercial and industrial $ 1,951 $ — $ 1,951 $ 10,861 $ 689,225 $ 702,037 Mortgage warehouse — — — — 48,274 48,274 Real estate: Commercial real estate (including multi-family residential) 3,502 — 3,502 17,776 1,629,634 1,650,912 Commercial real estate construction and land development 1,300 — 1,300 974 427,854 430,128 1-4 family residential (including home equity) 3,643 — 3,643 3,201 642,467 649,311 Residential construction - — - — 186,411 186,411 Consumer and other 91 — 91 141 41,001 41,233 Total loans $ 10,487 $ — $ 10,487 $ 32,953 $ 3,664,866 $ 3,708,306 December 31, 2017 Loans Past Due and Still Accruing 30-89 90 or More Total Past Nonaccrual Current Total Days Days Due Loans Loans Loans Loans (Dollars in thousands) Commercial and industrial $ 1,069 $ — $ 1,069 $ 6,437 $ 449,623 $ 457,129 Mortgage warehouse — — — — 69,456 69,456 Real estate: Commercial real estate (including multi-family residential) 4,932 — 4,932 6,110 1,069,205 1,080,247 Commercial real estate construction and land development 5,274 — 5,274 — 238,115 243,389 1-4 family residential (including home equity) 924 — 924 781 299,514 301,219 Residential construction 674 — 674 — 108,442 109,116 Consumer and other 74 — 74 — 10,246 10,320 Total loans $ 12,947 $ — $ 12,947 $ 13,328 $ 2,244,601 $ 2,270,876 If interest on nonaccrual loans had been accrued under the original loan terms, approximately $1.0 million and $733 thousand would have been recorded as income for the years ended December 31, 2018 and 2017, respectively. Impaired Loans Impaired loans by class of loans are set forth in the following tables. December 31, 2018 Unpaid Recorded Principal Related Investment Balance Allowance (Dollars in thousands) With no related allowance recorded: Commercial and industrial $ 4,354 $ 4,771 $ — Mortgage warehouse — — — Real estate: Commercial real estate (including multi-family residential) 11,322 11,322 — Commercial real estate construction and land development 1,326 1,326 — 1-4 family residential (including home equity) 2,742 2,741 — Residential construction — — — Consumer and other 3 3 — Total 19,747 20,163 — With an allowance recorded: Commercial and industrial 9,150 9,545 3,898 Mortgage warehouse — — — Real estate: Commercial real estate (including multi-family residential) 11,542 11,542 2,641 Commercial real estate construction and land development 3,114 3,114 190 1-4 family residential (including home equity) — — — Residential construction — — — Consumer and other — — — Total 23,806 24,201 6,729 Total: Commercial and industrial 13,504 14,316 3,898 Mortgage warehouse — — — Real estate: Commercial real estate (including multi-family residential) 22,864 22,864 2,641 Commercial real estate construction and land development 4,440 4,440 190 1-4 family residential (including home equity) 2,742 2,741 — Residential construction — — — Consumer and other 3 3 — $ 43,553 $ 44,364 $ 6,729 December 31, 2017 Unpaid Recorded Principal Related Investment Balance Allowance (Dollars in thousands) With no related allowance recorded: Commercial and industrial $ 5,792 $ 6,666 $ — Mortgage warehouse — — — Real estate: Commercial real estate (including multi-family residential) 12,155 12,155 — Commercial real estate construction and land development 209 209 — 1-4 family residential (including home equity) 948 948 — Residential construction — — — Consumer and other — — — Total 19,104 19,978 — With an allowance recorded: Commercial and industrial 5,600 5,652 1,640 Mortgage warehouse — — — Real estate: Commercial real estate (including multi-family residential) 8,009 8,194 716 Commercial real estate construction and land development — — — 1-4 family residential (including home equity) — — — Residential construction — — — Consumer and other — — — Total 13,609 13,846 2,356 Total: Commercial and industrial 11,392 12,318 1,640 Mortgage warehouse — — — Real estate: Commercial real estate (including multi-family residential) 20,164 20,349 716 Commercial real estate construction and land development 209 209 — 1-4 family residential (including home equity) 948 948 — Residential construction — — — Consumer and other — — — $ 32,713 $ 33,824 $ 2,356 The following table presents the average recorded investment of impaired loans and interest recognized on impaired loans. Years Ended December 31, 2018 2017 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized (Dollars in thousands) Commercial and industrial $ 14,555 $ 423 $ 11,972 $ 418 Mortgage warehouse — — — — Real estate: Commercial real estate (including multi-family residential) 23,198 756 20,606 475 Commercial real estate construction and land development 4,247 98 314 10 1-4 family residential (including home equity) 2,815 — 1,167 18 Residential construction — — — — Consumer and other 3 5 - 1 Total $ 44,818 $ 1,282 $ 34,059 $ 922 The average recorded investment of impaired loans for the year ended December 31, 2016 was $22.5 million. Interest income recognized for the year ended December 31, 2016 was $862 thousand. Credit Quality Indicators The company categorizes loans into risk categories based on relevant information about the ability of borrowers to service their debt including factors such as: current financial information, historical payment experience, credit documentation, public information and current economic trends. The Company analyzes loans individually by classifying the loans by credit risk. As part of the ongoing monitoring of the credit quality of the Company’s loan portfolio and methodology for calculating the allowance for credit losses, management assigns and tracks risk ratings to be used as credit quality indicators. The following is a general description of the risk ratings used: Watch —Loans classified as watch loans may still be of high quality, but have an element of risk added to the credit such as declining payment history, deteriorating financial position of the borrower or a decrease in collateral value. Special Mention —Loans classified as special mention have a potential weakness that deserves management’s close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the loan or of the institution’s credit position at some future date. They are characterized by the distinct possibility that the institution will sustain some loss if the deficiencies are not corrected. Substandard —Loans classified as substandard have well-defined weaknesses on a continuing basis and are inadequately protected by the current net worth and paying capacity of the borrower, impaired or declining collateral values, or a continuing downturn in their industry which is reducing their profits to below zero and having a significantly negative impact on their cash flow. These loans so classified are characterized by the distinct possibility that the institution will sustain some loss if the deficiencies are not corrected. Doubtful —Loans classified as doubtful have all the weaknesses inherent in those classified as substandard with the added characteristic that the weaknesses make collection or liquidation in full on the basis of currently existing facts, conditions and values, highly questionable and improbable. Loans not meeting the criteria above that are analyzed individually as part of the above described process are considered to be pass rated loans. Based on the most recent analysis performed, the risk category of loans by class of loan at December 31, 2018 is as follows: Pass Watch Special Mention Substandard Doubtful Total (Dollars in thousands) Commercial and industrial $ 656,783 $ 9,696 $ 13,874 $ 21,684 $ — $ 702,037 Mortgage warehouse 48,274 — — — — 48,274 Real estate: Commercial real estate (including multi-family residential) 1,570,243 29,702 7,101 43,866 — 1,650,912 Commercial real estate construction and land development 424,460 729 2,149 2,790 — 430,128 1-4 family residential (including home equity) 629,657 3,797 4,216 11,641 — 649,311 Residential construction 186,411 — — — — 186,411 Consumer and other 40,673 31 301 228 — 41,233 Total loans $ 3,556,501 $ 43,955 $ 27,641 $ 80,209 $ — $ 3,708,306 The following table presents the risk category of loans by class of loan at December 31, 2017: Pass Watch Special Mention Substandard Doubtful Total (Dollars in thousands) Commercial and industrial $ 427,336 $ 10,274 $ 2,195 $ 17,324 $ — $ 457,129 Mortgage warehouse 69,456 — — — — 69,456 Real estate: Commercial real estate (including multi-family residential) 1,016,831 23,039 4,685 35,692 — 1,080,247 Commercial real estate construction and land development 231,536 4,397 — 7,456 — 243,389 1-4 family residential (including home equity) 295,744 2,696 785 1,994 — 301,219 Residential construction 103,611 5,505 — — — 109,116 Consumer and other 10,207 111 — 2 — 10,320 Total loans $ 2,154,721 $ 46,022 $ 7,665 $ 62,468 $ — $ 2,270,876 Allowance for Loan Losses At December 31, 2018, the allowance for loan losses totaled $26.3 million, or 0.71% of total loans. At December 31, 2017, the allowance totaled $23.6 million or 1.04% of total loans. Acquired loans are carried over without an allowance for loan losses as they are recorded at fair value at the acquisition date. However, the Company recorded a discount on the acquired loans which will be prospectively accreted, increasing its basis in such loans. At December 31, 2018, the balance of the acquisition accounting discount was $14.2 million. The following table presents the activity in the allowance for loan losses by portfolio type for the years ended December 31, 2018, 2017 and 2016: Commercial real Commercial real 1-4 family Commercial estate (including estate construction residential and industrial Mortgage warehouse multi-family residential) and land development (including home equity) Residential construction Consumer and other Total (Dollars in thousands) Allowance for loan losses: Balance December 31, 2017 $ 7,694 $ — $ 10,253 $ 2,525 $ 2,140 $ 942 $ 95 $ 23,649 Provision for loan losses 2,234 — 1,588 199 127 98 2 4,248 Charge-offs (2,424 ) — (42 ) — (25 ) — (24 ) (2,515 ) Recoveries 847 — 102 — — — — 949 Net charge-offs (1,577 ) — 60 — (25 ) — (24 ) (1,566 ) Balance December 31, 2018 $ 8,351 $ — $ 11,901 $ 2,724 $ 2,242 $ 1,040 $ 73 $ 26,331 Allowance for loan losses: Balance December 31, 2016 $ 5,059 $ — $ 8,950 $ 1,217 $ 1,876 $ 748 $ 61 $ 17,911 Provision for loan losses 9,792 — 1,424 1,298 254 194 226 13,188 Charge-offs (7,673 ) — (124 ) — — — (196 ) (7,993 ) Recoveries 516 — 3 10 10 — 4 543 Net charge-offs (7,157 ) — (121 ) 10 10 — (192 ) (7,450 ) Balance December 31, 2017 $ 7,694 $ — $ 10,253 $ 2,525 $ 2,140 $ 942 $ 95 $ 23,649 Allowance for loan losses: Balance December 31, 2015 $ 3,644 $ — $ 5,914 $ 1,221 $ 1,432 $ 820 $ 67 $ 13,098 Provision for loan losses 1,951 — 3,122 (4 ) 434 (72 ) 38 5,469 Charge-offs (722 ) — (129 ) — — — (49 ) (900 ) Recoveries 186 — 43 — 10 — 5 244 Net charge-offs (536 ) — (86 ) — 10 — (44 ) (656 ) Balance December 31, 2016 $ 5,059 $ — $ 8,950 $ 1,217 $ 1,876 $ 748 $ 61 $ 17,911 The following table presents the balance in the allowance for loan losses by portfolio type based on the impairment method as of December 31, 2018 and 2017: Commercial real Commercial real 1-4 family Commercial estate (including estate construction residential and industrial Mortgage warehouse multi-family residential) and land development (including home equity) Residential construction Consumer and other Total (Dollars in thousands) Allowance for loan losses related to: December 31, 2018 Individually evaluated for impairment $ 3,898 $ — $ 2,641 $ 190 $ — $ — $ — $ 6,729 Collectively evaluated for impairment 4,453 — 9,260 2,534 2,242 1,040 73 19,602 Total allowance for loan losses $ 8,351 $ — $ 11,901 $ 2,724 $ 2,242 $ 1,040 $ 73 $ 26,331 Allowance for loan losses related to: December 31, 2017 Individually evaluated for impairment $ 1,640 $ — $ 716 $ — $ — $ — $ — $ 2,356 Collectively evaluated for impairment 6,054 — 9,537 2,525 2,140 942 95 21,293 Total allowance for loan losses $ 7,694 $ — $ 10,253 $ 2,525 $ 2,140 $ 942 $ 95 $ 23,649 The following table presents the recorded investment in loans held for investment by portfolio type based on the impairment method as of December 31, 2018 and 2017: Commercial real Commercial real 1-4 family Commercial estate (including estate construction residential and industrial Mortgage warehouse multi-family residential) and land development (including home equity) Residential construction Consumer and other Total (Dollars in thousands) Recorded investment in loans: December 31, 2018 Individually evaluated for impairment $ 13,504 $ — $ 22,864 $ 4,440 $ 2,742 $ — $ 3 $ 43,553 Collectively evaluated for impairment 688,533 48,274 1,628,048 425,688 646,569 186,411 41,230 3,664,753 Total loans evaluated for impairment $ 702,037 $ 48,274 1,650,912 $ 430,128 $ 649,311 $ 186,411 $ 41,233 $ 3,708,306 Recorded investment in loans: December 31, 2017 Individually evaluated for impairment $ 11,392 $ — $ 20,164 $ 209 $ 948 $ — $ — $ 32,713 Collectively evaluated for impairment 445,737 69,456 1,060,083 243,180 300,271 109,116 10,320 2,238,163 Total loans evaluated for impairment $ 457,129 $ 69,456 $ 1,080,247 $ 243,389 $ 301,219 $ 109,116 $ 10,320 $ 2,270,876 Troubled Debt Restructurings As of December 31, 2018 and 2017, the Company had a recorded investment in troubled debt restructurings of $33.1 million and $25.6 million, respectively. The Company allocated $3.0 million and $2.2 million of specific reserves for these loans at December 31, 2018 and 2017, respectively, and did not commit to lend additional amounts on these loans. The following table presents information regarding loans modified in a troubled debt restructuring during the years ended December 31, 2018, 2017 and 2016: As of December 31, 2018 2017 2016 Pre- Post- Pre- Post- Pre- Post- Modification of Modification of Modification of Modification of Modification of Modification of Number of Outstanding Outstanding Number of Outstanding Outstanding Number of Outstanding Outstanding Contracts Recorded Investment Recorded Investment Contracts Recorded Investment Recorded Investment Contracts Recorded Investment Recorded Investment (Dollars in thousands) Troubled Debt Restructurings Commercial and industrial 11 $ 2,770 $ 2,770 9 $ 2,399 $ 2,399 21 $ 3,939 $ 3,939 Mortgage warehouse — — — — — — — — — Real estate: Commercial real estate (including multi-family residential) 3 4,288 4,288 6 11,837 11,837 8 7,144 7,144 Commercial real estate construction and land development 1 3,114 3,114 1 210 210 — — — 1-4 family residential (including home equity) — — — 1 86 86 — — — Residential construction — — — — — — — — — Consumer and other — — — — — — 1 6 6 Total 15 $ 10,172 $ 10,172 17 $ 14,532 $ 14,532 30 $ 11,089 $ 11,089 Troubled debt restructurings resulted in charge-offs of $272 thousand, $136 thousand and $211 thousand during the years ended December 31, 2018, 2017 and 2016, respectively. As of December 31, 2018, there were four defaults totaling $200 thousand on loans that were modified as troubled debt restructurings during the preceding 12 months. Default is determined at 90 or more days past due. The modifications primarily related to extending the amortization periods of the loans. The Company did not grant principal reductions on any restructured loans. There were no commitments to lend additional amounts for the years 2018 and 2017. During the year ended December 31, 2018, the Company added $10.2 million in new troubled debt restructurings, of which $9.8 million was still outstanding on December 31, 2018.

FAIR VALUE

FAIR VALUE	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
FAIR VALUE	7. FAIR VALUE The Company uses fair value measurements to record fair value adjustments to certain assets and to determine fair value disclosures. Fair value represents the estimated exchange price that would be received from selling an asset or paid to transfer a liability, otherwise known as an “exit price” in the principal or most advantageous market available to the entity in an orderly transaction between market participants on the measurement date. Fair Value Hierarchy • Level 1—Quoted prices for identical assets or liabilities in active markets that the entity has the ability to access as of the measurement date. • Level 2—Significant other observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data. • Level 3—Significant unobservable inputs that reflect management’s judgment and assumptions that market participants would use in pricing an asset or liability that are supported by little or no market activity. The carrying amounts and estimated fair values of financial instruments that are reported on the balance sheet are as follows: As of December 31, 2018 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total (Dollars in thousands) Financial assets Cash and cash equivalents $ 268,947 $ 268,947 $ — $ — $ 268,947 Available for sale securities 337,293 — 337,293 — 337,293 Loans held for investment, net of allowance 3,681,975 — — 3,674,241 3,674,241 FHLB stock 10,941 N/A N/A N/A N/A Accrued interest receivable 17,010 65 3,498 13,447 17,010 Financial liabilities Deposits $ 3,662,536 $ — $ 3,653,244 $ — $ 3,653,244 Accrued interest payable 2,812 — 2,812 — 2,812 Borrowed funds 225,493 — 230,445 — 230,445 Subordinated debt 48,899 — 49,663 — 49,663 As of December 31, 2017 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total (Dollars in thousands) Financial assets Cash and cash equivalents $ 182,103 $ 182,103 $ — $ — $ 182,103 Available for sale securities 309,615 — 309,615 — 309,615 Loans held for investment, net of allowance 2,247,227 — — 2,238,721 2,238,721 FHLB stock 12,862 N/A N/A N/A N/A Accrued interest receivable 12,194 3 3,296 8,895 12,194 Financial liabilities Deposits $ 2,213,974 $ — $ 2,209,111 $ — $ 2,209,111 Accrued interest payable 610 — 610 — 610 Borrowed funds 282,569 — 288,887 — 288,887 Subordinated debt 48,659 — 48,659 — 48,659 The fair value estimates presented herein are based on pertinent information available to management as of the dates indicated. The following is a description of valuation methodologies used for assets and liabilities recorded at fair value, non-financial assets and non-financial liabilities and for estimating fair value for financial instruments not recorded at fair value: Cash and Cash Equivalents —For these short-term instruments, the carrying amount is a reasonable estimate of fair value. The Company classifies the estimated fair value of these instruments as Level 1. Available for Sale Securities —Fair values for investment securities are based upon quoted market prices, if available, and are considered Level 1 inputs. For all other available for sale securities, if quoted prices are not available, fair values are measured based on market prices for similar securities and are considered Level 2 inputs. For these securities, the Company generally obtains fair value measurements from an independent pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. Available for sale securities are recorded at fair value on a recurring basis. Loans Held for Investment —The estimated fair value approximates carrying value for variable-rate loans that reprice frequently and that have no significant change in credit risk resulting in a Level 3 classification. Fair values for fixed-rate loans and variable rate loans which reprice infrequently are estimated by discounting future cash flows. In accordance with ASU 2016-01, which was adopted effective January 1, 2018, the discount rates used to determine the fair value of loans at December 31, 2018 used interest rate spreads that reflect factors such as liquidity, credit and nonperformance risk of the loans. The discount rates used to determine the fair value of loans at December 31, 2017 were based on interest rates currently being offered for loans with similar terms to borrowers of similar credit quality resulting in a Level 3 classification. Federal Home Loan Bank Stock —The fair value of FHLB stock is estimated to be equal to its carrying amount as it is not practical to determine the fair value of FHLB stock due to restrictions placed on its transferability. Deposits —The fair value of demand deposits (e.g., interest and noninterest checking, savings and certain types of money market deposits) is the amount payable on demand at the reporting date (i.e., their carrying amount) resulting in a Level 2 classification. The fair value of fixed rate certificates of deposit is estimated using a discounted cash flows calculation that applies interest rates currently offered on certificates of deposit to a schedule of aggregated expected monthly maturities on time deposits resulting in a Level 2 classification. Accrued Interest —The carrying amounts of accrued interest approximate their fair values resulting in a Level 2 or 3 classification. Borrowed Funds —The fair value of the Company’s borrowed funds are estimated using discounted cash flow analyses based on the current borrowing rates for similar types of borrowing arrangements and are measured utilizing Level 2 inputs. Subordinated Debt —The fair values of subordinated debentures and notes are estimated using discounted cash flow analyses based on the Company’s current borrowing rates for similar types of borrowing arrangements and are measured utilizing Level 2 inputs. Off-balance sheet instruments —The fair values of off-balance sheet commitments to extend credit and standby letters of credit financial instruments are based on fees currently charged to enter into similar agreements, taking into account the remaining terms of the agreements and the counterparties’ credit standing. The Company has reviewed the unfunded portion of commitments to extend credit as well as standby and other letters of credit and has determined that the fair value of such financial instruments is not material. The following tables present fair values for assets measured at fair value on a recurring basis: As of December 31, 2018 Level 1 Level 2 Level 3 Total (Dollars in thousands) Available for sale securities: U.S. Government and agency securities $ — $ 8,685 $ — $ 8,685 Municipal securities — 216,785 — 216,785 Agency mortgage-backed pass-through securities — 66,195 — 66,195 Corporate bonds and other — 45,628 — 45,628 Total $ — $ 337,293 $ — $ 337,293 As of December 31, 2017 Level 1 Level 2 Level 3 Total (Dollars in thousands) Available for sale securities: U.S. Government and agency securities $ — $ 8,715 $ — $ 8,715 Municipal securities — 222,958 — 222,958 Agency mortgage-backed pass-through securities — 31,812 — 31,812 Corporate bonds and other — 46,130 — 46,130 Total $ — $ 309,615 $ — $ 309,615 There were no liabilities measured at fair value on a recurring basis as of December 31, 2018 or 2017. There were no transfers between levels during 2018 or 2017. Certain assets and liabilities are measured at fair value on a nonrecurring basis; that is the instruments are not measured at fair value on an ongoing basis, but are subject to fair value adjustments in certain circumstances such as evidence of impairment. As of December 31, 2018 Level 1 Level 2 Level 3 (Dollars in thousands) Impaired loans: Commercial and industrial $ — $ — $ 5,647 Commercial real estate (including multi-family residential) — — 8,901 Commercial real estate construction and land development — — 2,924 Other real estate owned — — 630 $ — $ — $ 18,102 As of December 31, 2017 Level 1 Level 2 Level 3 (Dollars in thousands) Impaired loans: Commercial and industrial $ — $ — $ 4,012 Commercial real estate (including multi-family residential) — — 7,478 Other real estate owned — — 365 $ — $ — $ 11,855 Historically, the Company measures fair value for certain loans and other real estate owned on a nonrecurring basis as described below. Impaired Loans with Specific Allocation of Allowance Impaired loans are those loans the Company has measured at fair value, generally based on the fair value of the loan’s collateral. A loan is considered impaired when, based on current information and events, it is probable that the Company will be unable to collect all amounts due pursuant to the contractual terms of the loan agreement. Impairment is measured by estimating the fair value of the loan based on the present value of expected cash flows, the market price of the loan, or the underlying fair value of the loan’s collateral. For real estate loans, fair value of the impaired loan’s collateral is determined by third party appraisals, which are then adjusted for the estimated selling and closing costs related to liquidation of the collateral. For this asset class, the actual valuation methods (income, sales comparable or cost) vary based on the status of the project or property. For example, land is generally based on the sales comparable method while construction is based on the income and/or sales comparable methods. The unobservable inputs may vary depending on the individual assets with no one of the three methods being the predominant approach. The Company reviews the third party appraisal for appropriateness and adjusts the value downward to consider selling and closing costs, which typically range from 5% to 10% of the appraised value. For non-real estate loans, fair value of the impaired loan’s collateral may be determined using an appraisal, net book value per the borrower’s financial statements or aging reports, adjusted or discounted based on management’s historical knowledge, changes in market conditions from the time of the valuation and management’s expertise and knowledge of the customer and the customer's business. During the years ended December 31, 2018 and 2017, certain impaired loans were reevaluated and reported at fair value through a specific allocation of the allowance for loan losses. At December 31, 2018, the total reported fair value of impaired loans of $17.5 million based on collateral valuations utilizing Level 3 valuation inputs had a carrying value of $24.2 million that was reduced by specific allowance allocations totaling $6.7 million. At December 31, 2017, the total reported fair value of impaired loans of $11.5 million based on collateral valuations utilizing Level 3 valuation inputs had a carrying value of $13.8 million that was reduced by specific allowance allocations totaling $2.4 million. Other Real Estate Owned Other real estate owned is comprised of real estate acquired in partial or full satisfaction of loans. Other real estate owned is recorded at its estimated fair value less estimated selling and closing costs at the date of transfer. Any excess of the related loan balance over the fair value less expected selling costs is charged to the allowance. Subsequent declines in fair value are reported as adjustments to the carrying amount and are recorded against earnings. The fair value of other real estate owned is determined using appraisals or other indications of value based on recent comparable sales of similar properties or assumptions generally observable in the marketplace. For this asset class, the actual valuation methods (income, sales comparable or cost) vary based on the status of the project or property. For example, land is generally based on the sales comparable method while construction is based on the income and/or sales comparable methods. The unobservable inputs may vary depending on the individual assets with no one of the three methods being the predominant approach. The Company reviews the third party appraisal for appropriateness and adjusts the value downward to consider selling and closing costs, which typically range from 5% to 10% of the appraised value. At December 31, 2018, the balance of other real estate owned consisted of a $630 thousand foreclosed commercial real estate property recorded as a result of obtaining physical possession of the property. The Company had $365 thousand of other real estate owned at December 31, 2017.

PREMISES AND EQUIPMENT

PREMISES AND EQUIPMENT	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
PREMISES AND EQUIPMENT	8. PREMISES AND EQUIPMENT Premises and equipment are summarized as follows: As of December 31, 2018 2017 (Dollars in thousands) Land $ 11,586 $ 5,376 Buildings 23,455 7,977 Leasehold improvements 5,291 5,059 Furniture, fixtures and equipment 11,858 8,967 Construction in progress 480 320 Total 52,670 27,699 Less: accumulated depreciation 10,953 9,222 Premises and equipment, net $ 41,717 $ 18,477 Depreciation expense was $2.1 million for the year ended December 31, 2018 and $1.6 million for each of the years ended December 31, 2017 and 2016.

DEPOSITS

DEPOSITS	12 Months Ended
	Dec. 31, 2018
Deposit Liabilities [Abstract]
DEPOSITS	9. DEPOSITS Time deposits that meet or exceed the Federal Deposit Insurance Corporation (the “FDIC”) insurance limit of $250 thousand at December 31, 2018 and December 31, 2017 were $509.3 million and $227.4 million, respectively. Scheduled maturities of time deposits for the next five years are as follows (dollars in thousands): Within one year $ 793,284 After one but within two years 161,877 After two but within three years 89,942 After three but within four years 92,790 After four but within five years 68,598 Total $ 1,206,491 The Company has $261.1 million and $314.8 million of brokered deposits, and there were no major concentrations of deposits with any one depositor at December 31, 2018 and 2017, respectively. Included in the December 31, 2017 amount were reciprocal deposits that the Company placed through the Certificates of Deposits Account Registry Service (CDARS) Network of $68.4 million. Related party deposits from principal officers, directors and their affiliates at December 31, 2018 and 2017 were $9.6 million and $14.8 million, respectively.

BORROWINGS AND BORROWING CAPACI

BORROWINGS AND BORROWING CAPACITY	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
BORROWINGS AND BORROWING CAPACITY	10. BORROWINGS AND BORROWING CAPACITY The Company has an available line of credit with the FHLB of Dallas, which allows the Company to borrow on a collateralized basis. FHLB advances are used to manage liquidity as needed. The advances are secured by a blanket lien on certain loans. Maturing advances are replaced by drawing on available cash, making additional borrowings or through increased customer deposits. At December 31, 2018, the Company had total borrowing capacity of $1.06 billion, of which $765.4 million was available under this agreement and $296.5 million was outstanding. FHLB advances of $225.0 million were outstanding at December 31, 2018, at a weighted average rate of 2.57%. Letters of credit were $71.5 million at December 31, 2018, of which $8.8 million expired in January 2019, $10.2 million expired in February 2019, $7.1 million will expire in April 2019, $7.1 million will expire in May 2019, $5.5 million will expire in August 2019, $25.0 million will expire in October 2019, $6.3 million will expire in December 2019 and $1.5 million will expire in January 2020. On December 28, 2018, the Company amended its revolving credit agreement to increase the maximum commitment to advance funds to $45.0 million which will reduce annually by $7.5 million beginning in December 2020 and on each December 22nd for the following years thereafter. The Company is required to repay any outstanding balance in excess of the then-current maximum commitment amount. The revised agreement will mature in December 2025 and is secured by 100% of the capital stock of the Bank. The credit agreement contains certain restrictive covenants. At December 31, 2018, the Company believes it was in compliance with all such debt covenants and had not been made aware of any noncompliance by the lender. The interest rate on the debt is the Prime Rate minus 25 basis points, or 5.00%, at December 31, 2018, and is paid quarterly. Scheduled principal maturities are as follows (dollars in thousands): 2019 $ — 2020 — 2021 — 2022 — 2023 and thereafter 569 Total $ 569

SUBORDINATED DEBT

SUBORDINATED DEBT	12 Months Ended
	Dec. 31, 2018
Subordinated Borrowings [Abstract]
SUBORDINATED DEBT	11. SUBORDINATED DEBT Junior Subordinated Debentures On January 1, 2015, the Company acquired F&M Bancshares and assumed Farmers & Merchants Capital Trust II and Farmers & Merchants Capital Trust III with an aggregate original principal amount of $11.3 million and a current fair value of $9.4 million at December 31, 2018. At acquisition, the Company recorded a discount of $2.5 million on the debentures. The difference between the carrying value and contractual balance will be recognized as a yield adjustment over the remaining term for the debentures. Each of the trusts is a capital or statutory business trust organized for the sole purpose of issuing trust securities and investing the proceeds in the Company’s junior subordinated debentures. The preferred trust securities of each trust represent preferred beneficial interests in the assets of the respective trusts and are subject to mandatory redemption upon payment of the junior subordinated debentures held by the trust. The common securities of each trust are wholly owned by the Company. Each trust’s ability to pay amounts due on the trust preferred securities is solely dependent upon the Company making payment on the related junior subordinated debentures. The debentures, which are the only assets of each trust, are subordinate and junior in right of payment to all of the Company’s present and future senior indebtedness. The Company has fully and unconditionally guaranteed each trust’s obligations under the trust securities issued by such trust to the extent not paid or made by each trust, provided such trust has funds available for such obligations. The junior subordinated debentures are included in Tier 1 capital under current regulatory guidelines and interpretations. Under the provisions of each issue of the debentures, the Company has the right to defer payment of interest on the debentures at any time, or from time to time, for periods not exceeding five years. If interest payments on either issue of the debentures are deferred, the distributions on the applicable trust preferred securities and common securities will also be deferred. A summary of pertinent information related to the Company's issuances of junior subordinated debentures outstanding at December 31, 2018 is set forth in the table below: Description Issuance Date Trust Preferred Securities Outstanding Interest Rate (1) Junior Subordinated Debt Owed to Trusts Maturity Date (2) Farmers & Merchants Capital Trust II November 13, 2003 $ 7,500 3 month LIBOR + 3.00% $ 7,732 November 8, 2033 Farmers & Merchants Capital Trust III June 30, 2005 3,500 3 month LIBOR + 1.80% 3,609 July 7, 2035 $ 11,341 (1) The 3-month LIBOR in effect as of December 31, 2018 was 2.7902%. (2) All debentures are currently callable. Subordinated Notes In December 2017, the Bank completed the issuance, through a private placement, of $40.0 million aggregate principal amount of Fixed-to-Floating Rate Subordinated Notes (the "Notes") due December 15, 2027. The Notes were issued at a price equal to 100% of the principal amount, resulting in net proceeds to the Bank of $39.4 million. The Bank used the net proceeds from the offering to support its growth and for general corporate purposes. The Notes are intended to qualify as Tier 2 capital for bank regulatory purposes. The Notes bear a fixed interest rate of 5.25% per annum until (but excluding) December 15, 2022, payable semi-annually in arrears. From December 15, 2022, the Notes will bear a floating rate of interest equal to 3-Month LIBOR + 3.03% until the Notes mature on December 15, 2027, or such earlier redemption date, payable quarterly in arrears. The Notes will be redeemable by the Bank, in whole or in part, on or after December 15, 2022 or, in whole but not in part, upon the occurrence of certain specified tax events, capital events or investment company events. Any redemption will be at a redemption price equal to 100% of the principal amount of Notes being redeemed, plus accrued and unpaid interest, and will be subject to, and require, prior regulatory approval. The Notes are not subject to redemption at the option of the holders.

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES	12. INCOME TAXES The components of the provision for federal income taxes are as follows: Years Ended December 31, 2018 2017 2016 (Dollars in thousands) Current $ 8,204 $ 8,320 $ 11,162 Deferred (256 ) 427 (1,608 ) Total $ 7,948 $ 8,747 $ 9,554 Reported income tax expense differs from the amounts computed by applying the U.S. federal statutory income tax rate to income before income taxes for the years ended December 31, 2018, 2017 and 2016 due to the following: Years Ended December 31, 2018 2017 2016 (Dollars in thousands) Taxes calculated at statutory rate $ 9,504 $ 9,233 $ 11,342 Increase (decrease) resulting from: Stock based compensation (400 ) (755 ) 67 Effect of tax exempt income (1,284 ) (2,328 ) (1,929 ) Provisional deferred tax adjustment related to reduction in U.S. federal statutory income tax rate — 2,621 — Other, net 128 (24 ) 74 Total $ 7,948 $ 8,747 $ 9,554 Income tax expense for 2018 was impacted by the reduction in the U.S. federal statutory income tax rate to 21% under the Tax Cuts and Jobs Act, which was enacted on December 22, 2017. During 2017, as a result of the new law, the Company recognized a provisional net tax expense totaling $2.6 million. During 2016, the Company adopted a new accounting standard that requires the income tax effects associated with stock-based compensation to be recognized as a component of income tax expense. The Company recognized net tax benefits related to stock-based compensation totaling $587 thousand in 2018 and $1.1 million in 2017. Year-end deferred taxes are presented in the table below. As a result of the Tax Cuts and Jobs Act enacted on December 22, 2017, deferred taxes as of December 31, 2018 and 2017 are based on the 21% and 35% federal income tax rate, respectively. Deferred tax assets and liabilities are as follows: As of December 31, 2018 2017 (Dollars in thousands) Deferred tax assets: Allowance for credit losses $ 5,898 $ 5,284 Net unrealized loss on available for sale securities 761 — Deferred compensation 366 177 Total deferred tax assets 7,025 5,461 Deferred tax liabilities: Core deposit intangible and other purchase accounting adjustments (2,718 ) (1,100 ) Net unrealized gain on available for sale securities — (65 ) Premises and equipment basis difference (2,035 ) (321 ) Total deferred tax liabilities (4,753 ) (1,486 ) Net deferred tax assets $ 2,272 $ 3,975 Interest and penalties related to tax positions are recognized in the period in which they begin accruing or when the entity claims the position that does not meet the minimum statutory thresholds. The Company does not have any uncertain tax positions and does not have any interest and penalties recorded in the income statement for the years ended December 31, 2018, 2017 and 2016. The Company is no longer subject to examination by the US Federal Tax Jurisdiction for the years prior to 2015.

STOCK BASED COMPENSATION

STOCK BASED COMPENSATION	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
STOCK BASED COMPENSATION	13. STOCK BASED COMPENSATION At December 31, 2018, the Company had two stock-based employee compensation plans with awards outstanding. In connection with the acquisition of Post Oak Bancshares, Inc., on October 1, 2018, the Company assumed the Post Oak Bancshares, Inc. Stock Option Plan, under which no additional awards will be issued. The Company accounts for stock based employee compensation plans using the fair value-based method of accounting. The Company recognized total stock based compensation expense of $1.7 million, $1.8 million and $1.5 million for the years ended December 31, 2018, 2017 and 2016, respectively. During 2015, the Company’s Board of Directors and shareholders approved the 2015 Amended and Restated Stock Awards and Incentive Plan (the “Plan”) covering certain awards of stock-based compensation to key employees and directors of the Company. The Plan was amended in 2017 as the shareholders authorized a maximum aggregate number of shares of stock to be issued of 1,900,000, any or all of which may be issued through incentive stock options and restricted stock. Stock Options Options to purchase a total of 1,309,231 shares of Company stock have been granted as of December 31, 2018. Under the Plan, options are exercisable up to 10 years from the date of the grant and, dependent on the terms of the applicable award agreement generally vest 4 years after the date of grant. The fair value of stock options granted is estimated at the date of grant using the Black-Scholes option-pricing model. As part of the Post Oak acquisition, all outstanding Post Oak options were assumed by Allegiance and converted using the 0.7017 exchange ratio to 299,352 options at a weighted average exercise price of $12.83 per option. The expected volatility was determined based on historical volatilities of Allegiance's common stock. The expected term of options granted is based on historical data and represents the period of time that options granted are expected to be outstanding and takes into account that the options are not transferable. The risk-free interest rate for the expected term of the option is based on the U.S. Treasury yield curve in effect at the time of the grant. The Black-Scholes pricing model utilizes certain assumptions noted in the table below. 2018 2017 2016 Risk-free interest rate 2.72 % 2.40 % 1.76 % Expected term 10.00 10.00 10.00 Expected stock price volatility 29.26 % 29.70 % 34.60 % Dividend yield — — — A summary of the activity in the stock option plans during the years ended December 31, 2018 and 2017 is set forth below: Weighted Weighted Average Average Aggregate Number of Exercise Remaining Intrinsic Options Price Contractual Term Value (In thousands) (In years) (In thousands) Options outstanding, January 1, 2017 935 $ 18.21 6.23 $ 16,773 Options granted 64 36.88 Options exercised (215 ) 17.50 Options forfeited (9 ) 23.35 Options outstanding, December 31, 2017 775 $ 19.94 5.72 $ 13,718 Options granted 4 40.40 Options assumed 299 12.83 Options exercised (244 ) 13.88 Options forfeited (32 ) 29.53 Options outstanding, December 31, 2018 802 $ 18.88 4.61 $ 10,830 Options vested and exercisable, December 31, 2018 677 $ 17.32 4.09 $ 10,193 The Company expects all outstanding options at December 31, 2018 to vest. Information related to the stock option plans during each year is as follows: 2018 2017 2016 (In thousands) Intrinsic value of options exercised $ 3,254 $ 3,371 $ 1,128 Cash received from option exercises 3,393 3,743 1,782 Weighted average fair value of options granted $ 18.00 $ 16.55 $ 10.51 As of December 31, 2018, there was $950 thousand of total unrecognized compensation cost related to nonvested stock options granted under the plans. The cost is expected to be recognized over a weighted-average period of 1.41 years. Restricted Stock Awards The Company has issued 226,529 restricted stock awards under the Plan as of December 31, 2018. During 2016, the Company awarded 15,401 shares of restricted stock with a weighted average grant date fair value of $17.52. During 2017, the Company awarded 28,106 shares of restricted stock with a weighted average grant date fair value of $36.17. During 2018, the Company awarded 122,127 shares of restricted stock with a weighted average grant date fair value of $39.04. The shares of restricted stock generally vest over a period of 4 years and are considered outstanding at the date of issuance. The Company accounts for shares of restricted stock by recording the fair value of the grant on the award date as compensation expense over the vesting period. A summary of the activity of the nonvested shares of restricted stock as of December 31, 2018 and 2017 including changes during the years then ended is as follows: Weighted Average Grant Number of Date Fair Shares Value (Shares in thousands) Nonvested share awards outstanding, January 1, 2017 24 $ 18.31 Share awards granted 28 36.17 Share awards vested (11 ) 18.32 Unvested share awards forfeited or cancelled — — Nonvested share awards outstanding, December 31, 2017 41 $ 30.46 Share awards granted 122 39.04 Share awards vested (20 ) 30.12 Unvested share awards forfeited or cancelled — — Nonvested share awards outstanding, December 31, 2018 143 $ 37.48 At December 31, 2018, there was $4.8 million of unrecognized compensation expense related to the restricted stock awards which is expected to be recognized over a weighted-average period of 3.59 years. The total fair value of restricted stock awards that fully vested during the years ended December 31, 2018, 2017 and 2016 was approximately $621 thousand, $203 thousand and $172 thousand, respectively.

OTHER EMPLOYEE BENEFITS

OTHER EMPLOYEE BENEFITS	12 Months Ended
	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
OTHER EMPLOYEE BENEFITS	14. OTHER EMPLOYEE BENEFITS 401(k) benefit plan The Company has a 401(k) benefit plan whereby participants may contribute a percentage of their compensation. The Company matches 50% of an employee's contributions up to 6% of the employee’s compensation, for a maximum match of 3% of compensation. Matching contribution expense as of December 31, 2018, 2017 and 2016 was $962 thousand, $789 thousand and $637 thousand, respectively. Profit sharing plan The financial statements include an accrual for $2.5 million, $1.5 million and $1.7 million for a contribution to the plan as a profit sharing contribution for the years ended December 31, 2018, 2017 and 2016, respectively. Employee Stock Purchase Plan The Company offers its employees an opportunity to purchase shares of Allegiance’s common stock, pursuant to the terms of the Allegiance Bancshares, Inc. Amended and Restated Employee Stock Purchase Plan, as amended (“ESPP”). The ESPP was adopted by the Board of Directors to provide employees with an opportunity to purchase shares of Allegiance in order to provide employees a more direct opportunity to participate in the Company’s growth. The Company allows employees to purchase shares at a 15% discount to market value and thus incurs stock based compensation expense for the fair value of the discount given. The Company recognized total stock based compensation expense of $48 thousand, $144 thousand and $90 thousand for the years ended December 31, 2018, 2017, and 2016 respectively.

OFF-BALANCE SHEET ARRANGEMENTS,

OFF-BALANCE SHEET ARRANGEMENTS, COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
OFF-BALANCE SHEET ARRANGEMENTS, COMMITMENTS AND CONTINGENCIES	15. OFF-BALANCE SHEET ARRANGEMENTS, COMMITMENTS AND CONTINGENCIES In the normal course of business, the Company enters into various transactions, which, in accordance with accounting principles generally accepted in the United States are not included in the Company’s consolidated balance sheets. The Company enters into these transactions to meet the financing needs of its customers. These transactions include commitments to extend credit and standby and commercial letters of credit, which involve to varying degrees elements of credit risk and interest rate risk in excess of the amounts recognized in the consolidated balance sheets. The Company uses the same credit policies in making commitments and conditional obligations as it does for on balance sheet instruments. Commitments to Extend Credit Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. Since many of the commitments are expected to expire without being fully drawn upon, the total commitment amounts disclosed do not necessarily represent future cash funding requirements. The Company evaluates each customer’s creditworthiness on a case-by-case basis. The Company minimizes its exposure to loss under these commitments by subjecting them to credit approval and monitoring procedures. Management assesses the credit risk associated with certain commitments to extend credit in determining the level of the allowance for credit losses. The amount and type of collateral, if deemed necessary by the Company upon extension of credit, is based on management’s credit evaluation of the customer. Standby Letters of Credit Standby letters of credit are written conditional commitments issued by the Company to guarantee the performance of a customer to a third party. In the event of nonperformance by the customer, the Company has the rights to the underlying collateral. The credit risk to the Company in issuing letters of credit is essentially the same as that involved in extending loan facilities to its customers. The Company’s policy for obtaining collateral, and the nature of such collateral, is essentially the same as that involved in making commitments to extend credit. The contractual amounts of financial instruments with off-balance sheet risk are as follows: December 31, 2018 December 31, 2017 Fixed Variable Fixed Variable Rate Rate Rate Rate (Dollars in thousands) Commitments to extend credit $ 471,440 $ 530,546 $ 369,573 $ 250,467 Standby letters of credit 14,217 9,067 15,445 1,725 Total $ 485,657 $ 539,613 $ 385,018 $ 252,192 Commitments to make loans are generally made for periods of 120 days or less. As of December 31, 2018, the fixed rate loan commitments have interest rates ranging from 1.95% to 8.70% with a weighted average maturity and rate of 2.49 years and 5.26%, respectively. Leases The following table presents a summary of non-cancelable future operating lease commitments as of December 31, 2018 (dollars in thousands): 2019 $ 2,559 2020 1,987 2021 1,731 2022 1,510 2023 1,042 Thereafter 4,083 $ 12,912 It is expected that in the normal course of business, expiring leases will be renewed or replaced by leases on other property. Rent expense under all noncancelable operating lease obligations aggregated approximately $2.9 million, $2.8 million and $2.7 million for the years ended December 31, 2018, 2017 and 2016, respectively.

REGULATORY CAPITAL MATTERS

REGULATORY CAPITAL MATTERS	12 Months Ended
	Dec. 31, 2018
Banking And Thrift [Abstract]
REGULATORY CAPITAL MATTERS	16. REGULATORY CAPITAL MATTERS The Company and the Bank are subject to various regulatory capital requirements administered by the federal banking agencies. Capital adequacy guidelines and, additionally for banks, prompt corrective action regulations involve quantitative measures of assets, liabilities and certain off balance sheet items calculated under regulatory accounting practices. Capital amounts and classifications are also subject to qualitative judgments by regulators about components, risk weightings and other factors. Failure to meet minimum capital requirements can initiate actions by regulators that, if undertaken, could have a direct material effect on the Company’s consolidated financial statements. The final rules implementing Basel Committee on Banking Supervision’s capital guideline for U.S. Banks (Basel III Rules) became effective for the Company on January 1, 2015 with full compliance with all of the requirements being phased in over a multi-year schedule, and were fully phased in on January 1, 2019. Management believes as of December 31, 2018 and 2017, the Company and the Bank met all capital adequacy requirements to which they were subject. Prompt corrective action regulations provide five classifications: well capitalized, adequately capitalized, undercapitalized, significantly undercapitalized and critically undercapitalized, although these terms are not used to represent overall financial condition. If adequately capitalized, regulatory approval is required to accept brokered deposits. If undercapitalized, capital distributions are limited as is asset growth and expansion, and capital restoration plans are required. At year-end 2018 and 2017, the most recent regulatory notifications categorized the Bank as well capitalized under the regulatory framework for prompt corrective action. There are no conditions or events since that notification that management believes have changed the institution’s category. The following is a summary of the Company’s and the Bank’s actual and required capital ratios at December 31, 2018 and 2017: To Be Categorized As Well Capitalized Under Actual For Capital Adequacy Purposes Minimum Required Plus Capital Conservation Buffer Prompt Corrective Action Provisions Amount Ratio Amount Ratio Amount Ratio Amount Ratio (Dollars in thousands) ALLEGIANCE BANCSHARES, INC. (Consolidated) As of December 31, 2018 Total Capital (to risk weighted assets) $ 531,453 13.70 % $ 310,295 8.00 % $ 383,020 9.875 % N/A N/A Common Equity Tier 1 Capital (to risk weighted assets) 456,223 11.76 % 174,541 4.50 % 247,266 6.375 % N/A N/A Tier I Capital (to risk weighted assets) 465,637 12.01 % 232,721 6.00 % 305,446 7.875 % N/A N/A Tier I Capital (to average tangible assets) 465,637 10.61 % 175,621 4.00 % 175,621 4.000 % N/A N/A As of December 31, 2017 Total Capital (to risk weighted assets) $ 336,829 13.43 % $ 200,687 8.00 % $ 232,044 9.250 % N/A N/A Common Equity Tier 1 Capital (to risk weighted assets) 264,521 10.54 % 112,886 4.50 % 144,244 5.750 % N/A N/A Tier I Capital (to risk weighted assets) 273,825 10.92 % 150,515 6.00 % 181,872 7.250 % N/A N/A Tier I Capital (to average tangible assets) 273,825 9.84 % 111,274 4.00 % 111,274 4.000 % N/A N/A ALLEGIANCE BANK As of December 31, 2018 Total Capital (to risk weighted assets) $ 524,660 13.53 % $ 310,179 8.00 % $ 382,877 9.875 % $ 387,724 10.00 % Common Equity Tier 1 Capital (to risk weighted assets) 458,844 11.83 % 174,476 4.50 % 247,174 6.375 % 252,021 6.50 % Tier I Capital (to risk weighted assets) 458,844 11.83 % 232,634 6.00 % 305,333 7.875 % 310,179 8.00 % Tier I Capital (to average tangible assets) 458,844 10.45 % 175,552 4.00 % 175,552 4.000 % 219,440 5.00 % As of December 31, 2017 Total Capital (to risk weighted assets) $ 331,872 13.24 % $ 200,596 8.00 % $ 231,939 9.250 % $ 250,745 10.00 % Common Equity Tier 1 Capital (to risk weighted assets) 268,868 10.72 % 112,835 4.50 % 144,179 5.750 % 162,985 6.50 % Tier I Capital (to risk weighted assets) 268,868 10.72 % 150,447 6.00 % 181,790 7.250 % 200,596 8.00 % Tier I Capital (to average tangible assets) 268,868 9.67 % 111,230 4.00 % 111,230 4.000 % 139,037 5.00 % Dividend Restrictions Allegiance's principal source of funds for dividend payments is dividends received from the Bank. Banking regulations limit the amount of dividends that may be paid without prior approval of regulatory agencies. In addition, Allegiance's credit agreement with another financial institution also limits its ability to pay dividends. Under applicable banking regulations, the amount of dividends that may be paid by the Bank in any calendar year is limited to the current year’s net profits combined with the retained net profits of the preceding two years, subject to the capital requirements described above.

EARNINGS PER COMMON SHARE

EARNINGS PER COMMON SHARE	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
EARNINGS PER COMMON SHARE	17. EARNINGS PER COMMON SHARE Diluted earnings per common share is computed using the weighted-average number of common shares determined for the basic earnings per common share computation plus the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock using the treasury stock method. Outstanding stock options issued by the Company represent the only dilutive effect reflected in diluted weighted average shares. Restricted shares are considered outstanding at the date of grant, accounted for as participating securities and are included in basic and diluted weighted average common shares outstanding. Year Ended December 31, 2018 2017 2016 Per Share Per Share Per Share Amount Amount Amount Amount Amount Amount (Amounts in thousands, except per share data) Net income attributable to shareholders $ 37,309 $ 17,632 $ 22,851 Basic: Weighted average shares outstanding 15,485 $ 2.41 13,125 $ 1.34 12,873 $ 1.78 Diluted: Add incremental shares for: Dilutive effect of stock option exercises 288 333 201 Total 15,773 $ 2.37 13,458 $ 1.31 13,074 $ 1.75 Stock options for 69 thousand and 28 thousand shares were not considered in computing diluted earnings per share as of December 31, 2018 and 2017, respectively, because they were antidilutive. All stock options as of December 31, 2016 were dilutive and considered in computing diluted earnings per share.

PARENT COMPANY ONLY FINANCIAL S

PARENT COMPANY ONLY FINANCIAL STATEMENTS	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
PARENT COMPANY ONLY FINANCIAL STATEMENTS	18. PARENT COMPANY ONLY FINANCIAL STATEMENTS ALLEGIANCE BANCSHARES, INC (PARENT COMPANY ONLY) CONDENSED BALANCE SHEETS December 31, 2018 2017 (Dollars in thousands) ASSETS Cash and due from banks $ 6,780 $ 4,857 Investment in subsidiary 705,947 311,553 Other assets 1,026 791 TOTAL $ 713,753 $ 317,201 LIABILITIES AND SHAREHOLDERS’ EQUITY LIABILITIES: Other borrowed funds $ 492 $ 569 Subordinated debentures 9,414 9,304 Accrued interest payable and other liabilities 862 463 Total liabilities 10,768 10,336 SHAREHOLDERS’ EQUITY: Common stock 21,938 13,227 Capital surplus 571,804 218,408 Retained earnings 112,131 74,894 Accumulated other comprehensive (loss) income (2,888 ) 336 Total shareholders’ equity 702,985 306,865 TOTAL $ 713,753 $ 317,201 ALLEGIANCE BANCSHARES, INC (PARENT COMPANY ONLY) CONDENSED STATEMENTS OF INCOME For the Years Ended December 31, 2018 2017 2016 (Dollars in thousands) OPERATING INCOME: Other income $ 16 $ 13 $ 11 Total income 16 13 11 OPERATING EXPENSE: Interest expense on borrowed funds 38 33 30 Other expenses 1,692 1,465 1,204 Total operating expense 1,730 1,498 1,234 INCOME BEFORE INCOME TAX BENEFIT AND EQUITY IN UNDISTRIBUTED EARNINGS OF SUBSIDIARIES (1,714 ) (1,485 ) (1,223 ) INCOME TAX BENEFIT 360 756 428 INCOME BEFORE EQUITY IN UNDISTRIBUTED EARNINGS OF SUBSIDIARIES (1,354 ) (729 ) (795 ) EQUITY IN UNDISTRIBUTED EARNINGS OF SUBSIDIARIES 38,663 18,361 23,646 NET INCOME $ 37,309 $ 17,632 $ 22,851 ALLEGIANCE BANCSHARES, INC (PARENT COMPANY ONLY) CONDENSED STATEMENTS OF CASH FLOWS For the Years Ended December 31, 2018 2017 2016 (Dollars in thousands) CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 37,309 $ 17,632 $ 22,851 Adjustments to reconcile net income to net cash used in operating activities: Equity in undistributed earnings of subsidiaries (38,663 ) (18,361 ) (23,646 ) Net amortization of discount on subordinated debentures 110 107 107 Increase in other assets (236 ) (378 ) (399 ) Increase (decrease) in accrued interest payable and other liabilities 279 (377 ) 186 Net cash used in operating activities (1,201 ) (1,377 ) (901 ) CASH FLOWS FROM INVESTING ACTIVITIES: Capital investment in bank subsidiary — (21,000 ) — Net cash used in investing activities — (21,000 ) — CASH FLOWS FROM FINANCING ACTIVITIES: Proceeds from issuance of common stock 3,552 4,248 2,006 Proceeds from initial public offering — — — Stock based compensation expense 1,685 1,780 1,501 (Repurchase) issuance of treasury stock (2,113 ) — 38 Net cash provided by financing activities 3,124 6,028 3,545 NET CHANGE IN CASH AND CASH EQUIVALENTS 1,923 (16,349 ) 2,644 CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD 4,857 21,206 18,562 CASH AND CASH EQUIVALENTS, END OF PERIOD $ 6,780 $ 4,857 $ 21,206

QUARTERLY FINANCIAL DATA (UNAUD

QUARTERLY FINANCIAL DATA (UNAUDITED)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
QUARTERLY FINANCIAL DATA (UNAUDITED)	19. QUARTERLY FINANCIAL DATA (UNAUDITED) Net Income Interest Net Interest Attributable to Earnings Per Share (1) Income Income Common Shareholders Basic Diluted (Dollars in thousands, except per share data) 2018 First quarter $ 32,391 $ 26,889 $ 7,711 $ 0.58 $ 0.57 Second quarter 34,193 27,816 7,556 0.57 0.55 Third quarter 35,336 28,036 8,879 0.66 0.65 Fourth quarter 56,303 45,838 13,163 0.60 0.59 2017 First quarter $ 27,512 $ 24,128 $ 6,047 $ 0.46 $ 0.45 Second quarter 28,987 25,107 5,395 0.41 0.40 Third quarter 30,901 26,997 2,986 0.23 0.22 Fourth quarter 32,038 27,436 3,204 0.24 0.24 (1) Earnings per share are computed independently for each of the quarters presented and therefore may not total earnings per share for the year

SUBSEQUENT EVENT

SUBSEQUENT EVENT	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
SUBSEQUENT EVENT	20. SUBSEQUENT EVENT On February 1, 2019, the Bank completed the previously announced acquisition of LoweryBank, the Sugar Land location of Huntington State Bank. In connection with the purchase, the Bank acquired approximately $44.0 million in loans and $15.0 million in customer deposits. The Bank consolidated its existing Sugar Land bank office into this new bank office location, which was less than one mile away. The acquisition of LoweryBank will be accounted for under the acquisition method of accounting in accordance with ASC Topic 805 – Business Combinations. Allegiance’s assessment of the fair value of assets acquired and liabilities assumed as of the acquisition date is incomplete at the time of this filing; therefore, certain disclosure have been omitted. Allegiance expects to recognize goodwill in the transaction, which is expected to be nondeductible for tax purposes.

NATURE OF OPERATIONS AND SUMM_2

NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING AND REPORTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Nature of Operations and Principles of Consolidation	Nature of Operations and Principles of Consolidation- The consolidated financial statements include Allegiance Bancshares, Inc. (“Allegiance”) and its wholly-owned subsidiary, Allegiance Bank (the “Bank”, and together with Allegiance, collectively referred to as the “Company”) provide commercial and retail loans and commercial banking services. Intercompany transactions and balances are eliminated in consolidation under U.S. generally accepted accounting principles (“GAAP”). The Company derives substantially all of its revenues and income from the operation of the Bank. Allegiance Bank is a Texas banking association which began operations in October 2007. The Company is focused on delivering a wide variety of relationship-driven commercial banking products and community-oriented services tailored to meet the needs of small to mid-sized businesses, professionals and individuals through its 28 offices, with 27 bank offices and one loan production office in the Houston metropolitan area and one office in Beaumont, just outside of the Houston metropolitan area, as of the year ended December 31, 2018. The Bank provides its customers with a variety of banking services including checking accounts, savings accounts and certificates of deposit and its primary lending products are commercial, personal, automobile, mortgage and home improvement loans. The Bank also offers safe deposit boxes, automated teller machines, drive-through services and 24-hour depository facilities.
Use of Estimates	Use of Estimates— The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions based on available information. These estimates and assumptions affect the reporting of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Acquisition	Acquisition – On October 1, 2018, Allegiance completed the acquisition of Post Oak Bancshares, Inc. See Note 2 – Acquisitions for additional information pertaining to the Post Oak acquisition and the impact of the transaction on the Company’s consolidated financial statements.
Cash and cash equivalents	Cash and cash equivalents —Cash and cash equivalents include cash, deposits with other financial institutions with maturities not greater than one year. Net cash flows are reported for customer loan and deposit transactions.
Securities	Securities —Debt securities are classified as available for sale when they might be sold before maturity. Securities available for sale are carried at fair value. Unrealized gains and losses are excluded from earnings and reported, net of tax, as a separate component of shareholders’ equity until realized. Securities within the available for sale portfolio may be used as part of the Company’s asset/liability strategy and may be sold in response to changes in interest rate risk, prepayment risk or other similar economic factors. Interest earned on these assets is included in interest income. Interest income includes amortization of purchase premium or discount. Premiums and discounts on securities are amortized on the level-yield method, except for mortgage backed securities where prepayments are anticipated. Gains and losses on sales are recorded on the trade date and determined using the specific identification method. Management evaluates debt securities for other-than-temporary impairment (“OTTI”) on at least a quarterly basis, and more frequently when economic or market conditions warrant such an evaluation. For securities in an unrealized loss position, management considers the extent and duration of the unrealized loss, and the financial condition and near-term prospects of the issuer. Management also assesses whether it intends to sell, or it is more likely than not that it will be required to sell, a security in an unrealized loss position before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the entire difference between amortized cost and fair value is recognized as impairment through earnings. For debt securities that do not meet the aforementioned criteria, the amount of impairment is split into two components as follows: (1) OTTI related to credit loss, which must be recognized in the income statement and (2) OTTI related to other factors, which is recognized in other comprehensive income, net of applicable taxes. The credit loss is defined as the difference between the present value of the cash flows expected to be collected and the amortized cost basis. The previous amortized cost bases less the OTTI recognized in earnings shall become the new amortized cost basis of the security.
Loans Held for Investment	Loans Held for Investment —Loans held for investment are those that management has the intent and ability to hold for the foreseeable future or until maturity or payoff are reported at the principal balance outstanding, net of deferred loan fees and costs, and an allowance for loan losses. Loans are typically secured by specific items of collateral including business assets, consumer assets and commercial and residential real estate. Commercial loans are expected to be repaid from cash flow from operations of businesses. Interest income is accrued on the unpaid principal balance.
Acquired Loans	Acquired Loans — A cquired loans are recorded at fair value at the date of acquisition with no initial valuation allowance based on a discounted cash flow methodology that considers various factors including the type of loan and related collateral, classification status, fixed or variable interest rate, term of loan and whether or not the loan was amortizing, and a discount rate reflecting the Company’s assessment of risk inherent in the cash flow estimates. Certain larger purchased loans are individually evaluated while certain purchased loans are grouped together according to similar risk characteristics and are treated in the aggregate when applying various valuation techniques. These cash flow evaluations are inherently subjective as they require material estimates, all of which may be susceptible to significant change. Loans acquired in a business combination that have evidence of deterioration of credit quality since origination and for which it is probable, at acquisition, that the Company will be unable to collect all contractually required payments receivable are considered purchased credit impaired (“PCI”). PCI loans are individually evaluated and recorded at fair value at the date of acquisition with no initial valuation allowance based on a discounted cash flow methodology that considers various factors including the type of loan and related collateral, classification status, fixed or variable interest rate, term of loan and whether or not the loan was amortizing, and a discount rate reflecting the Company’s assessment of risk inherent in the cash flow estimates. Increases in expected cash flows, including prepayments, subsequent to the initial investment are recognized prospectively through adjustment of the yield on the loan over its remaining life. Decreases in expected cash flows are recognized as impairment. Valuation allowances on PCI loans reflect only losses incurred after the acquisition (meaning the present value of all cash flows expected at acquisition that ultimately are not to be received). For acquired loans not deemed credit-impaired at acquisition, the differences between the initial fair value and the unpaid principal balance are recognized as interest income on a level-yield basis over the lives of the related loans. Subsequent to the acquisition date, methods utilized to estimate the required allowance for loan losses for these loans is similar to originated loans; however, a provision for credit losses will be recorded only to the extent the required allowance exceeds any remaining purchase discounts. Once an acquired loan undergoes new underwriting and meets the criteria for a new loan, such as in the case of a loan renewal, any remaining fair value adjustments are accreted into interest income and the loan establishes a new amortized cost basis that is fully subject to the Company's allowance for loan loss methodology.
Nonrefundable Fees and Costs Associated with Lending Activities	Nonrefundable Fees and Costs Associated with Lending Activities — Loan commitment and loan origination fees, and certain direct origination costs, are deferred and recognized in interest income as an adjustment to yield without anticipating prepayments using the interest method over the related loan life or; if the commitment expires unexercised, balances are recognized in income upon expiration of the commitment.
Nonperforming and Past Due Loans	Nonperforming and Past Due Loans —The Company has several procedures in place to assist it in maintaining the overall quality of its loan portfolio. The Company has established underwriting guidelines to be followed by its officers, and monitors its delinquency levels for any negative or adverse trends. There can be no assurance, however, that the Company’s loan portfolio will not become subject to increasing pressures from deteriorating borrower credit due to general economic conditions or other factors. Past due status is based on the contractual terms of the loan. Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. The Company generally classifies a loan as nonperforming, automatically places the loan on nonaccrual status, ceases accruing interest and reverses all unpaid accrued interest against interest income, when, in management’s opinion, the borrower may be unable to meet payment obligations, when the payment of principal or interest on a loan is delinquent for 90 days, as well as when required by regulatory provisions, unless the loan is in the process of collection and the underlying collateral fully supports the carrying value of the loan. Any payments received on nonaccrual loans are applied first to outstanding loan amounts. Interest income is subsequently recognized only to the extent cash payments are received in excess of principal due. Any excess is treated as recovery of lost interest. Loans are returned to accrual status when all of the principal and interest amounts contractually due are brought current and future payments are reasonably assured. In all cases, loans are placed on nonaccrual or charged-off at an earlier date if collection of principal or interest is considered doubtful. If the decision is made to continue accruing interest on the loan, periodic reviews are made to confirm the accruing status of the loan. Nonaccrual loans and loans past due 90 days include both smaller balance homogeneous loans that are collectively evaluated for impairment and individually classified impaired loans. When available information confirms that specific loans, or portions thereof, are uncollectible, these amounts are charged-off against the allowance. All loan types are considered delinquent after 30 days past due and are typically charged-off or charged-down no later than 120 days past due, with consideration of, but not limited to, the following criteria in determining the need and optional timing of the charge-off or charge-down: (1) the Bank is in the process of repossession or foreclosure and there appears to be a likely deficiency, (2) the collateral securing the loan has been sold and there is an actual deficiency, (3) the Bank is proceeding with lengthy legal action to collect its balance, (4) the borrower is unable to be located or (5) the borrower has filed bankruptcy. Charge-offs occur when the Company confirms a loss on a loan.
Troubled debt restructurings (TDRs)	Troubled debt restructurings (TDRs) —Loans on which terms have been modified resulting in a concession have been granted because of a borrower’s financial difficulty are considered troubled debt restructurings and classified as impaired. The restructuring of a loan is considered a troubled debt restructuring if both (1) the borrower is experiencing financial difficulties and (2) the creditor has granted a concession that it would not otherwise consider. Concessions may include reductions of interest rates to a below market interest rate: extension of the terms of the debt, principal forgiveness, restructuring the payment of the debt obligation; and other actions intended to minimize potential losses. Subsequent to identification as a troubled debt restructuring such loans are then evaluated for impairment on an individual basis whereby the loans are measured at the present value of estimated future cash flows using the loan’s effective rate at inception. If a troubled debt restructuring is considered to be a collateral dependent loan: the loan is reported, net, at the fair value of the collateral.
Impaired Loans	Impaired Loans —On a continuous basis, loans are evaluated for impairment classification. Loans are considered impaired when based on current information and events, it is probable the Company will be unable to collect all amounts due in accordance with the original contractual terms of the loan agreement including scheduled principal and interest payments. Impairment is evaluated in total for smaller-balance loans of a similar nature and on an individual loan basis for other loans. If a loan is impaired, a specific valuation allowance is allocated, if necessary, so that the loan is reported net, at the present value of estimated future cash flows using the loan’s existing rate or at the fair value of collateral if repayment is expected solely from the collateral. Factors considered by management in determining impairment include payment status, collateral value and the probability of collecting scheduled principal and interest payments when due. Loans that experience insignificant payment delays and payment shortfalls generally are not classified as impaired. Management determines the significance of payment delays and payment shortfalls on case-by-case basis taking into consideration all of the circumstances surrounding the loan and the borrower including the length of the delay, the reasons for the delay, the borrower’s prior payment record and the amount of the shortfall in relation to the principal and interest owed.
Allowance for Loan Losses	Allowance for Loan Losses —The allowance for loan losses is a valuation allowance that is established through charges to earnings in the form of a provision for loan losses. The amount of the allowance for loan losses is affected by the following: (1) charge-offs of loans that decrease the allowance, (2) subsequent recoveries on loans previously charged off that increase the allowance and (3) provisions for loan losses charged to income that increase the allowance. Throughout the year, management estimates the probable incurred losses in the loan portfolio to determine if the allowance for loan losses is adequate to absorb such losses. The allowance for loan losses consists of specific and general components. The specific component relates to loans that are individually classified as impaired. The Company follows a loan review program to evaluate the credit risk in the loan portfolio. Loans that have been identified as impaired are generally reviewed on a quarterly basis in order to determine whether a specific reserve is required. The general component covers non-impaired loans and is based on industry and Company specific historical loan loss experience, volume, growth and composition of the loan portfolio, the evaluation of the Company’s loan portfolio through its internal loan review process, general current economic conditions both internal and external to the Company that may affect the borrower’s ability to pay, value of collateral and other qualitative relevant risk factors. Based on a review of these estimates, the allowance for loan losses is adjusted to a level determined to be adequate. Estimates of loan losses are inherently subjective as it involves an exercise of judgment. It is the judgment of management that the allowance for loan losses reflected in the consolidated balance sheets is adequate to absorb probable losses that exist in the loan portfolio as of the reporting date. For troubled debt restructurings that subsequently default, the Company determines the amount of reserve in accordance with the accounting policy for the allowance for loan losses. The Company assesses the exposure for each modification, either by collateral discounting or by calculation of the present value of future cash flows, and determines if a specific allocation to the allowance for loan losses is needed. Once an obligation has been restructured because of such credit problems, it continues to be considered a troubled debt restructuring until paid in full. The Company returns troubled debt restructurings to accrual status only if (1) all contractual amounts due can reasonably be expected to be repaid within a prudent period and (2) repayment has been in accordance with the contract for a sustained period, typically at least twelve months. Loans acquired in business combinations are initially recorded at fair value, which includes an estimate of loan losses expected to be realized over the remaining lives of the loans. Therefore no corresponding allowance for loan losses is recorded for these loans at acquisition. Methods utilized to estimate any subsequently required allowance for loan losses for acquired loans not deemed credit-impaired at acquisition are similar to originated loans. However, the estimate of loss is based on the unpaid principal balance and then compared to any remaining unaccreted purchase discount. To the extent that the calculated loss is greater than the remaining unaccreted purchase discount, an allowance is recorded for such difference.
Premises and Equipment	Premises and Equipment —Premises and equipment are carried at cost less accumulated depreciation. Depreciation expense is calculated principally using the straight-line method over the estimated useful lives of the assets which range from 3 to 40 years. Leasehold improvements are amortized using the straight-line method over the periods of the leases or the estimated useful lives, whichever is shorter. Land is carried at cost.
Other Real Estate Owned	Other Real Estate Owned —Assets acquired through or instead of loan foreclosure are held for sale and are initially recorded at fair value less estimated selling costs when acquired, establishing a new cost basis. Costs after acquisition are generally expensed. If the fair value of the asset declines, a write-down is recorded through expense. The valuation of foreclosed assets is subjective in nature and may be adjusted in the future because of changes in economic conditions. At December 31, 2018, the $630 thousand balance of other real estate owned was a residential real estate property.
Federal Home Loan Bank (“FHLB”) Stock	Federal Home Loan Bank (“FHLB”) Stock— The Bank is a member of the FHLB system. Members are required to own a certain amount of stock based on the level of borrowings and other factors and may invest in additional amounts. FHLB stock is carried at cost, classified as a restricted security and periodically evaluated for impairment based on ultimate recovery of par value. Both cash and stock dividends are reported as income.
Bank Owned Life Insurance	Bank Owned Life Insurance— The Company purchased bank owned life insurance policies on certain key executives and acquired life insurance policies in conjunction with the acquisitions of F&M Bancshares and Post Oak. Bank owned life insurance is recorded at the amount that can be realized under the insurance contract at the balance sheet date, which is the cash surrender value, which is the most reasonable estimate of fair value, adjusted for other charges or other amounts due that are probable at settlement.
Goodwill	Goodwill —Goodwill resulting from business combinations is generally determined as the excess of the fair value of the consideration transferred, plus the fair value of any noncontrolling interests in the acquiree, over the fair value of the net assets acquired and liabilities assumed as of the acquisition date. Goodwill is determined to have an indefinite useful life and is not amortized, but is tested for impairment at least annually or more frequently if events and circumstances exists that indicate that a goodwill impairment test should be performed. The Company performs its annual impairment test on October 1. Goodwill is the only intangible asset with an indefinite life on the Company’s balance sheet.
Core Deposit Intangibles	Core Deposit Intangibles —Core deposit and acquired customer relationship intangibles arising from acquisitions are amortized using a straight-line amortization method over their estimated useful lives, which is seven to ten years.
Borrowed Funds	Borrowed Funds —The Company has a credit agreement with another financial institution. The Company pledged its shares in the Bank’s stock as collateral for the borrowing.
Loan Commitments and Related Financial Instruments	Loan Commitments and Related Financial Instruments —Financial instruments include off-balance sheet credit instruments, such as commitments to extend credit, issued to meet customer financing needs. The face amount for these items represents the exposure to loss before considering customer collateral or ability to repay. Such financial instruments are recorded when they are funded.
Stock Based Compensation	Stock Based Compensation —Compensation cost is recognized for stock options and restricted stock awards issued to employees, based on the fair value of these awards at the date of grant. The expense associated with stock based compensation is recognized over the required service period, generally defined as the vesting period of each individual arrangement. For awards with graded vesting, compensation cost is recognized on a straight-line basis over the requisite service period for the entire award. The fair value of stock options granted and employee stock purchase plan awards are estimated at the date of grant using the Black-Scholes option-pricing model and the market price of the Company’s common stock on the date prior to the grant date is used to value restricted stock awards.
Employee Stock Purchase Plan	Employee Stock Purchase Plan —The cost of shares issued in the ESPP, but not allocated to participants, is shown as a reduction of shareholder’s equity. Compensation expense is based on the market price of the shares as they are committed to be released to participant accounts.
Income Taxes	Income Taxes —Income tax expense is the total of the current year income tax due and the change in deferred tax assets or liabilities. Deferred tax assets and liabilities are recognized for the estimated tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and are recorded in other assets on the Company’s consolidated balance sheets. The Company records uncertain tax positions on the basis of a two-step process whereby (1) the Company determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more likely than not recognition threshold, the Company recognizes the largest amount of tax benefit that is greater than 50 percent likely of being realized upon ultimate settlement with the related tax authority. For tax positions not meeting the more likely than not test, no tax benefit is recorded. Any interest and/or penalties related to income taxes are reported as a component of income tax expense. The Company files a consolidated federal income tax return.
Comprehensive Income	Comprehensive income —Comprehensive income consists of net income and other comprehensive income which includes unrealized gains and losses on securities available for sale which are also recognized as separate components of equity.
Fair Value of Financial Instruments	Fair Value of Financial Instruments —Fair values of financial instruments are estimated using relevant market information and other assumptions, as more fully disclosed in a separate note. Fair value estimates involve uncertainties and matters of significant judgment regarding interest rates, credit risk, prepayments and other factors, especially in the absence of broad markets for particular items. Changes in assumptions or in market conditions could significantly affect these estimates.
Operating Segments	Operating Segments— While management monitors the revenue streams of the various products and services, operations are managed and financial performance is evaluated on a Company-wide basis. All of the financial service operations are considered by management to be aggregated in one reportable operating segment.
Reclassification	Reclassifications —Some items in the prior year financial statements were reclassified to conform to the current presentation. Reclassifications had no effect on prior year net income or shareholders’ equity.
Earnings per Common Share	Earnings per Common Share —Basic earnings per common share is calculated as net income divided by the weighted average number of common shares outstanding during the period. Diluted earnings per common share includes the dilutive effect of additional potential common shares issuable under stock options, restricted stock awards and the Employee Stock Purchase Plan.
Loss Contingencies	Loss Contingencies —Loss contingencies, including claims and legal actions arising in the ordinary course of business, are recorded as liabilities when the likelihood of loss is probable and an amount or range of loss can be reasonably estimated. Management does not believe there are such matters that will have a material effect on the financial statements.
Dividend Restrictions	Dividend Restrictions —Banking regulations require maintaining certain capital levels and may limit the dividends paid by the Bank to Allegiance or by Allegiance to its shareholders. In addition, Allegiance's credit agreement with another financial institution also limits its ability to pay dividends.
Revenue from Contracts with Customers	Revenue from Contracts with Customers -The Company records revenue from contracts with customers in accordance with Accounting Standards Codification Topic 606, “Revenue from Contracts with Customers” (“Topic 606”). Under Topic 606, the Company must identify the contract with a customer, identify the performance obligations in the contract, determine the transaction price, allocate the transaction price to the performance obligations in the contract, and recognize revenue when (or as) the Company satisfies a performance obligation. Significant revenue has not been recognized in the current reporting period that results from performance obligations satisfied in previous periods. The Company’s primary sources of revenue are derived from interest and dividends earned on loans, investment securities, and other financial instruments that are not within the scope of Topic 606. The Company has evaluated the nature of its contracts with customers and determined that further disaggregation of revenue from contracts with customers into more granular categories beyond what is presented in the Consolidated Statements of Income was not necessary. The Company generally fully satisfies its performance obligations on its contracts with customers as services are rendered and the transaction prices are typically fixed; charged either on a periodic basis or based on activity. Because performance obligations are satisfied as services are rendered and the transaction prices are fixed, the Company has made no significant judgments in applying the revenue guidance prescribed in ASC 606 that affect the determination of the amount and timing of revenue from contracts with customers
New Accounting Standards	New Accounting Standards Adoption of New Accounting Standards ASU 2014-09 “Revenue from Contracts with Customers (Topic 606).” ASU 2014-09 supersedes the revenue recognition requirements in Revenue Recognition (Topic 605), and most industry-specific guidance throughout the Industry Topics of the Codification. The core principle of ASU 2014-09 is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new standard was effective for the Company on January 1, 2018 and management has completed its analysis of the impact of the standard’s adoption. Adoption of the ASU did not have a significant impact on the Company’s consolidated financial statements and related disclosures. The Company’s primary sources of revenue are derived from interest and dividends earned on loans, investment securities, and other financial instruments that are not within the scope of ASU 2014-09. The Company’s revenue recognition pattern for revenue streams within the scope of ASU 2014-09, including but not limited to service charges on deposit accounts and gains/losses on the sale of OREO, did not change significantly from current practice. The standard permits the use of either the full retrospective or modified retrospective transition method. The Company elected to use the modified retrospective transition method which requires application of ASU 2014-09 to uncompleted contracts at the date of adoption; however, periods prior to the date of adoption will not be retrospectively revised as the impact of the ASU on uncompleted contracts at the date of adoption was not material. ASU No. 2016-01, “Financial Instruments - Overall (Subtopic 825-10): Recognition of Financial Assets and Financial Liabilities.” ASU 2016-01 makes targeted amendments to fair value measurement and disclosure guidance. ASU 2016-01 requires equity investments (other than equity method investments) to be measured at fair value with changes in fair value recognized in net income. This change is only applied if a readily determinable fair value can be obtained. Adoption of the standard also resulted in the use of an exit price rather than an entrance price to determine the fair value of loans not measured at fair value on a non-recurring basis in the consolidated balance sheets. See Note 7 – Fair Value disclosures for further information regarding the valuation of these loans. ASU 2016-01 became effective for the Company on January 1, 2018. ASU 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business,” (“ASU 2017-01”) to improve such definition and, as a result, assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or as business combinations. The definition of a business impacts many areas of accounting including acquisitions, disposals, goodwill and consolidation. ASU 2017-01 became effective for the Company on January 1, 2018 and is to be applied under a prospective approach. The Company expects the adoption of this new guidance to impact the determination of whether future acquisitions are considered business combinations or asset purchases. Newly Issued But Not Yet Effective Accounting Standards ASU 2016-02 “Leases (Topic 842)." ASU 2016-02 will, among other things, require lessees to recognize a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. ASU 2016-02 does not significantly change lease accounting requirements applicable to lessors; however, certain changes were made to align, where necessary, lessor accounting with the lessee accounting model and ASC Topic 606, “Revenue from Contracts with Customers.” The new standard was adopted by the Company on January 1, 2019. ASU 2016-02 provides for a modified retrospective transition approach requiring lessees to recognize and measure leases on the balance sheet at the beginning of either the earliest period presented or as of the beginning of the period of adoption. The Company has elected to apply ASU 2016-02 as of the beginning of the period of adoption (January 1, 2019) and will not restate comparative periods. The Company expects that the adoption of ASU 2016-02 will result in the recognition of lease liabilities totaling $15,000,000 to $17,000,000 and the recognition of right-of-use assets totaling $15,000,000 to $17,000,000, which results in an estimated 5 basis point decrease in the tier 1 capital to risk weighted assets ratio as of the date of adoption. The initial balance sheet gross up upon adoption is primarily related to operating leases of certain real estate properties. The Company has no material leasing arrangements for which it is the lessor of property or equipment. The Company has made an accounting policy election to not apply the recognition requirements in the new standard to short-term leases. The Company has elected to apply the package of practical expedients allowed by the new standard under which the Company need not reassess whether any expired or existing contracts are or contain leases, the Company need not reassess the lease classification for any expired or existing lease, and the Company need not reassess initial direct costs for any existing leases. The Company has also elected to use the practical expedient to make an accounting policy election for leases of certain underlying assets to include both lease and nonlease components as a single component and account for it as a lease. Adoption of ASU 2016-02 is not expected to materially change the Company’s recognition of lease expense in future periods. ASU 2016-13, “Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” Among other things, ASU 2016-13 requires the measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions and reasonable and supportable forecasts. Financial institutions and other organizations will now use forward-looking information to better form their credit loss estimates. Many of the loss estimation techniques applied today will still be permitted, although the inputs to those techniques will change to reflect the full amount of expected credit losses. In addition, ASU 2016-13 amends the accounting for credit losses on available for sale debt securities and purchased financial assets with credit deterioration. ASU 2016-13 is effective for the Company on January 1, 2020 and must be applied using the modified retrospective approach with limited exceptions. Early adoption is permitted for fiscal years, and interim periods within those years, beginning after December 15, 2018. While the Company is currently unable to reasonably estimate the impact of adopting ASU 2016-13, the Company expects that the impact of adoption will be significantly influenced by the composition, characteristics and quality of its loan and securities portfolios as well as the prevailing economic conditions and forecasts as of the adoption date. ASU No. 2017-04, “Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” ASU 2017-04 eliminates Step 2 from the goodwill impairment test which required entities to compute the implied fair value of goodwill. Under ASU 2017-04, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. ASU 2017-04 will be effective for the Company on January 1, 2020, with earlier adoption permitted and is not expected to have a significant impact on the Company's financial statements. ASU 2017-08,“Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20) - Premium Amortization on Purchased Callable Debt Securities.” ASU 2017-08 shortens the amortization period for certain callable debt securities held at a premium to require such premiums to be amortized to the earliest call date unless applicable guidance related to certain pools of securities is applied to consider estimated prepayments. Under prior guidance, entities were generally required to amortize premiums on individual, non-pooled callable debt securities as a yield adjustment over the contractual life of the security. ASU 2017-08 does not change the accounting for callable debt securities held at a discount. ASU 2017-08 became effective for the Company on January 1, 2019, with early adoption permitted. The Company will record a $1.7 million impact of ASU 2017-08 in its 2019 financial statements. ASU 2018-02, “Income Statement - Reporting Comprehensive Income (Topic 220) - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” ASU 2018-02 amends ASC 220, , to allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. ASU 2018-02 is effective on January 1, 2019, with early adoption permitted. The Company early adopted ASU 2018-02 and recognized a decrease to retained earnings of $72 thousand due to a reclassification on January 1, 2018.

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	12 Months Ended
	Dec. 31, 2018
Business Acquisition [Line Items]
Schedule of Purchase Price Allocation	As of October 1, 2018, the Company finalized its valuation of all assets and liabilities acquired, resulting in no changes to preliminary acquisition accounting adjustments. A summary of the final purchase price allocation is as follows (in thousands): Fair value of consideration paid: Common shares issued (8,402,010 shares) $ 350,364 Stock options issued (299,352) 8,639 Cash in lieu of fractional shares 21 Total consideration paid $ 359,024 Fair value of assets acquired: Cash and cash equivalents $ 230,416 Investment securities 42,779 Loans 1,164,279 Premises and equipment 21,988 Core deposit intangibles 25,128 Other assets 18,078 Total assets acquired $ 1,502,668 Fair value of liabilities assumed: Deposits $ 1,291,310 Other borrowed funds 30,000 Other liabilities 6,070 Total liabilities assumed 1,327,380 Fair value of net assets acquired $ 175,288 Goodwill resulting from acquisition $ 183,736
Schedule of Details of Loans Acquired	The following presents details of all loans acquired as of October 1, 2018: Contractual Balance Fair Value Discount (Dollars in thousands) Commercial and industrial $ 221,098 $ 217,204 $ (3,894 ) Real estate: Commercial real estate (including multi-family residential) 450,947 443,512 (7,435 ) Commercial real estate construction and land development 167,386 165,387 (1,999 ) 1-4 family residential (including home equity) 288,304 285,099 (3,205 ) Residential construction 23,812 23,812 — Consumer and other 29,684 29,267 (417 ) Total loans $ 1,181,231 $ 1,164,281 $ (16,950 )
Schedule of Pro Forma Information	The following table presents unaudited pro forma financial information as if the acquisition had occurred at the beginning of 2017. Post Oak’s results of operations were included in the Company’s results beginning October 1, 2018. The pro forma financial information is not necessarily indicative of the results of operations that would have occurred had the transaction been effected on the assumed dates. For the Years Ended December 31, 2018 2017 (Dollars in thousands, except per share data) Net interest income $ 170,801 $ 165,612 Noninterest income 10,060 9,543 Net income 41,807 35,107 Basic earnings per common share 2.70 1.63 Diluted earnings per common share 2.65 1.61
PCI Loans
Business Acquisition [Line Items]
Schedule of PCI Loans and Non-PCI Loans Acquired in Transactions	The following presents information at the acquisition date for PCI loans acquired in the transaction (dollars in thousands): Contractually required principal and interest payments $ 28,340 Contractual cash flows not expected to be collected (nonaccretable difference) 3,163 Expected cash flows at acquisition 25,177 Interest component of expected cash flows (accretable yield) 495 Fair value of loans acquired with deterioration of credit quality $ 24,682
Non-PCI Loans
Business Acquisition [Line Items]
Schedule of PCI Loans and Non-PCI Loans Acquired in Transactions	The following table presents information at the acquisition date for non-PCI loans acquired in the transaction (in thousands): Contractually required principal and interest payments $ 1,153,317 Accretable discount 13,293 Fair value at acquisition $ 1,140,024

GOODWILL AND CORE DEPOSIT INT_2

GOODWILL AND CORE DEPOSIT INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets and Goodwill	Changes in the carrying amount of the Company’s goodwill and core deposit intangibles were as follows: Core Deposit Goodwill Intangible Assets (Dollars in thousands) Balance as of January 1, 2016 $ 39,389 $ 5,230 Sale of branch assets — (390 ) Amortization — (785 ) Balance as of December 31, 2016 39,389 4,055 Amortization — (781 ) Balance as of December 31, 2017 39,389 3,274 Acquisition of Post Oak Bancshares, Inc. 183,736 25,128 Amortization — (1,815 ) Balance as of December 31, 2018 $ 223,125 $ 26,587
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	The estimated aggregate future amortization expense for core deposit intangibles remaining as of December 31, 2018 is as follows (dollars in thousands): 2019 $ 4,712 2020 3,922 2021 3,296 2022 3,003 2023 2,323 Thereafter 9,331 Total $ 26,587

SECURITIES (Tables)

SECURITIES (Tables)	12 Months Ended
	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Available-for-sale Securities	The amortized cost and fair value of investment securities were as follows: December 31, 2018 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value (Dollars in thousands) Available for Sale U.S. Government and agency securities $ 8,570 $ 161 $ (46 ) $ 8,685 Municipal securities 219,068 1,258 (3,541 ) 216,785 Agency mortgage-backed pass-through securities 66,987 237 (1,029 ) 66,195 Corporate bonds and other 46,303 15 (690 ) 45,628 Total $ 340,928 $ 1,671 $ (5,306 ) $ 337,293 December 31, 2017 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value (Dollars in thousands) Available for Sale U.S. Government and agency securities $ 8,507 $ 232 $ (24 ) $ 8,715 Municipal securities 222,330 2,470 (1,842 ) 222,958 Agency mortgage-backed pass-through securities 32,014 159 (361 ) 31,812 Corporate bonds and other 46,247 62 (179 ) 46,130 Total $ 309,098 $ 2,923 $ (2,406 ) $ 309,615
Investments Classified by Contractual Maturity Date	The amortized cost and fair value of investment securities at December 31, 2018, by contractual maturity, are shown below. Expected maturities may differ from contractual maturities if borrowers have the right to call or prepay obligations at any time with or without call or prepayment penalties. Amortized Fair Cost Value (Dollars in thousands) Due in one year or less $ 14,877 $ 14,823 Due after one year through five years 73,675 72,790 Due after five years through ten years 87,391 86,880 Due after ten years 97,998 96,605 Subtotal 273,941 271,098 Agency mortgage-backed pass through securities 66,987 66,195 Total $ 340,928 $ 337,293
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	Securities with unrealized losses segregated by length of time such securities have been in a continuous loss position are as follows: December 31, 2018 Less than 12 Months More than 12 Months Total Estimated Unrealized Estimated Unrealized Estimated Unrealized Fair Value Losses Fair Value Losses Fair Value Losses (Dollars in thousands) Available for Sale U.S. Government and agency securities $ 999 $ — $ 1,417 $ (46 ) $ 2,416 $ (46 ) Municipal securities 10,140 (29 ) 136,934 (3,512 ) 147,074 (3,541 ) Agency mortgage-backed pass- through securities 17,168 (209 ) 22,819 (820 ) 39,987 (1,029 ) Corporate bonds and other 13,634 (35 ) 29,014 (655 ) 42,648 (690 ) Total $ 41,941 $ (273 ) $ 190,184 $ (5,033 ) $ 232,125 $ (5,306 ) December 31, 2017 Less than 12 Months More than 12 Months Total Estimated Unrealized Estimated Unrealized Estimated Unrealized Fair Value Losses Fair Value Losses Fair Value Losses (Dollars in thousands) Available for Sale U.S. Government and agency securities $ 3,110 $ (9 ) $ 595 $ (15 ) $ 3,705 $ (24 ) Municipal securities 42,249 (517 ) 56,483 (1,325 ) 98,732 (1,842 ) Agency mortgage-backed pass- through securities 13,238 (105 ) 8,921 (256 ) 22,159 (361 ) Corporate bonds and other 30,203 (179 ) — — 30,203 (179 ) Total $ 88,800 $ (810 ) $ 65,999 $ (1,596 ) $ 154,799 $ (2,406 )

LOANS AND ALLOWANCE FOR LOAN _2

LOANS AND ALLOWANCE FOR LOAN LOSSES (Tables)	12 Months Ended
	Dec. 31, 2018
Accounts Notes And Loans Receivable [Line Items]
Schedule of Accounts, Notes, Loans and Financing Receivable	The loan portfolio balances, net of unearned income and fees, consist of various types of loans primarily all made to borrowers located within Texas and are classified by major type as follows: December 31, 2018 2017 (Dollars in thousands) Commercial and industrial $ 702,037 $ 457,129 Mortgage warehouse 48,274 69,456 Real estate: Commercial real estate (including multi- family residential) 1,650,912 1,080,247 Commercial real estate construction and land development 430,128 243,389 1-4 family residential (including home equity) 649,311 301,219 Residential construction 186,411 109,116 Consumer and other 41,233 10,320 Total loans 3,708,306 2,270,876 Allowance for loan losses (26,331 ) (23,649 ) Loans, net $ 3,681,975 $ 2,247,227 (1) Mortgage warehouse loans are to unaffiliated mortgage loan originators collateralized by mortgage promissory notes which are segregated in the Company’s mortgage warehouse portfolio. These promissory notes originated by the Company’s mortgage warehouse customers carry terms and conditions as would be expected in the competitive permanent mortgage market and serve as collateral under a traditional mortgage warehouse arrangement whereby such promissory notes are warehoused under a revolving credit facility to allow for the end investor (or purchaser) of the note to receive a complete loan package and remit funds to the bank. The maturity of each revolving line of credit facility is normally less than 24 months, while the promissory notes that are warehoused under such facilities may have a much shorter length of time outstanding. For mortgage promissory notes secured by residential property, the warehouse time is normally 10 to 20 days. For mortgage promissory notes secured by commercial property, the warehouse time is normally 40 to 50 days. The funded balance of the mortgage warehouse portfolio can have significant fluctuation based upon market demand for the product, level of home sales and refinancing activity, market interest rates and velocity of end investor processing times.
Schedule of Related Party Transactions	An analysis of activity with respect to these related-party loans is as follows: 2018 (Dollars in thousands) Beginning balance on January 1 $ 4,368 New loans and reclassified related loans 5,003 Repayments (1,501 ) Ending balance on December 31 $ 7,870
Past Due Financing Receivables	An aging analysis of the recorded investment in past due loans, segregated by class of loans, is as follows: December 31, 2018 Loans Past Due and Still Accruing 30-89 90 or More Total Past Nonaccrual Current Total Days Days Due Loans Loans Loans Loans (Dollars in thousands) Commercial and industrial $ 1,951 $ — $ 1,951 $ 10,861 $ 689,225 $ 702,037 Mortgage warehouse — — — — 48,274 48,274 Real estate: Commercial real estate (including multi-family residential) 3,502 — 3,502 17,776 1,629,634 1,650,912 Commercial real estate construction and land development 1,300 — 1,300 974 427,854 430,128 1-4 family residential (including home equity) 3,643 — 3,643 3,201 642,467 649,311 Residential construction - — - — 186,411 186,411 Consumer and other 91 — 91 141 41,001 41,233 Total loans $ 10,487 $ — $ 10,487 $ 32,953 $ 3,664,866 $ 3,708,306 December 31, 2017 Loans Past Due and Still Accruing 30-89 90 or More Total Past Nonaccrual Current Total Days Days Due Loans Loans Loans Loans (Dollars in thousands) Commercial and industrial $ 1,069 $ — $ 1,069 $ 6,437 $ 449,623 $ 457,129 Mortgage warehouse — — — — 69,456 69,456 Real estate: Commercial real estate (including multi-family residential) 4,932 — 4,932 6,110 1,069,205 1,080,247 Commercial real estate construction and land development 5,274 — 5,274 — 238,115 243,389 1-4 family residential (including home equity) 924 — 924 781 299,514 301,219 Residential construction 674 — 674 — 108,442 109,116 Consumer and other 74 — 74 — 10,246 10,320 Total loans $ 12,947 $ — $ 12,947 $ 13,328 $ 2,244,601 $ 2,270,876
Impaired Financing Receivables	Impaired loans by class of loans are set forth in the following tables. December 31, 2018 Unpaid Recorded Principal Related Investment Balance Allowance (Dollars in thousands) With no related allowance recorded: Commercial and industrial $ 4,354 $ 4,771 $ — Mortgage warehouse — — — Real estate: Commercial real estate (including multi-family residential) 11,322 11,322 — Commercial real estate construction and land development 1,326 1,326 — 1-4 family residential (including home equity) 2,742 2,741 — Residential construction — — — Consumer and other 3 3 — Total 19,747 20,163 — With an allowance recorded: Commercial and industrial 9,150 9,545 3,898 Mortgage warehouse — — — Real estate: Commercial real estate (including multi-family residential) 11,542 11,542 2,641 Commercial real estate construction and land development 3,114 3,114 190 1-4 family residential (including home equity) — — — Residential construction — — — Consumer and other — — — Total 23,806 24,201 6,729 Total: Commercial and industrial 13,504 14,316 3,898 Mortgage warehouse — — — Real estate: Commercial real estate (including multi-family residential) 22,864 22,864 2,641 Commercial real estate construction and land development 4,440 4,440 190 1-4 family residential (including home equity) 2,742 2,741 — Residential construction — — — Consumer and other 3 3 — $ 43,553 $ 44,364 $ 6,729 December 31, 2017 Unpaid Recorded Principal Related Investment Balance Allowance (Dollars in thousands) With no related allowance recorded: Commercial and industrial $ 5,792 $ 6,666 $ — Mortgage warehouse — — — Real estate: Commercial real estate (including multi-family residential) 12,155 12,155 — Commercial real estate construction and land development 209 209 — 1-4 family residential (including home equity) 948 948 — Residential construction — — — Consumer and other — — — Total 19,104 19,978 — With an allowance recorded: Commercial and industrial 5,600 5,652 1,640 Mortgage warehouse — — — Real estate: Commercial real estate (including multi-family residential) 8,009 8,194 716 Commercial real estate construction and land development — — — 1-4 family residential (including home equity) — — — Residential construction — — — Consumer and other — — — Total 13,609 13,846 2,356 Total: Commercial and industrial 11,392 12,318 1,640 Mortgage warehouse — — — Real estate: Commercial real estate (including multi-family residential) 20,164 20,349 716 Commercial real estate construction and land development 209 209 — 1-4 family residential (including home equity) 948 948 — Residential construction — — — Consumer and other — — — $ 32,713 $ 33,824 $ 2,356 The following table presents the average recorded investment of impaired loans and interest recognized on impaired loans. Years Ended December 31, 2018 2017 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized (Dollars in thousands) Commercial and industrial $ 14,555 $ 423 $ 11,972 $ 418 Mortgage warehouse — — — — Real estate: Commercial real estate (including multi-family residential) 23,198 756 20,606 475 Commercial real estate construction and land development 4,247 98 314 10 1-4 family residential (including home equity) 2,815 — 1,167 18 Residential construction — — — — Consumer and other 3 5 - 1 Total $ 44,818 $ 1,282 $ 34,059 $ 922
Financing Receivable Credit Quality Indicators	Based on the most recent analysis performed, the risk category of loans by class of loan at December 31, 2018 is as follows: Pass Watch Special Mention Substandard Doubtful Total (Dollars in thousands) Commercial and industrial $ 656,783 $ 9,696 $ 13,874 $ 21,684 $ — $ 702,037 Mortgage warehouse 48,274 — — — — 48,274 Real estate: Commercial real estate (including multi-family residential) 1,570,243 29,702 7,101 43,866 — 1,650,912 Commercial real estate construction and land development 424,460 729 2,149 2,790 — 430,128 1-4 family residential (including home equity) 629,657 3,797 4,216 11,641 — 649,311 Residential construction 186,411 — — — — 186,411 Consumer and other 40,673 31 301 228 — 41,233 Total loans $ 3,556,501 $ 43,955 $ 27,641 $ 80,209 $ — $ 3,708,306 The following table presents the risk category of loans by class of loan at December 31, 2017: Pass Watch Special Mention Substandard Doubtful Total (Dollars in thousands) Commercial and industrial $ 427,336 $ 10,274 $ 2,195 $ 17,324 $ — $ 457,129 Mortgage warehouse 69,456 — — — — 69,456 Real estate: Commercial real estate (including multi-family residential) 1,016,831 23,039 4,685 35,692 — 1,080,247 Commercial real estate construction and land development 231,536 4,397 — 7,456 — 243,389 1-4 family residential (including home equity) 295,744 2,696 785 1,994 — 301,219 Residential construction 103,611 5,505 — — — 109,116 Consumer and other 10,207 111 — 2 — 10,320 Total loans $ 2,154,721 $ 46,022 $ 7,665 $ 62,468 $ — $ 2,270,876
Allowance for Credit Losses on Financing Receivables	The following table presents the activity in the allowance for loan losses by portfolio type for the years ended December 31, 2018, 2017 and 2016: Commercial real Commercial real 1-4 family Commercial estate (including estate construction residential and industrial Mortgage warehouse multi-family residential) and land development (including home equity) Residential construction Consumer and other Total (Dollars in thousands) Allowance for loan losses: Balance December 31, 2017 $ 7,694 $ — $ 10,253 $ 2,525 $ 2,140 $ 942 $ 95 $ 23,649 Provision for loan losses 2,234 — 1,588 199 127 98 2 4,248 Charge-offs (2,424 ) — (42 ) — (25 ) — (24 ) (2,515 ) Recoveries 847 — 102 — — — — 949 Net charge-offs (1,577 ) — 60 — (25 ) — (24 ) (1,566 ) Balance December 31, 2018 $ 8,351 $ — $ 11,901 $ 2,724 $ 2,242 $ 1,040 $ 73 $ 26,331 Allowance for loan losses: Balance December 31, 2016 $ 5,059 $ — $ 8,950 $ 1,217 $ 1,876 $ 748 $ 61 $ 17,911 Provision for loan losses 9,792 — 1,424 1,298 254 194 226 13,188 Charge-offs (7,673 ) — (124 ) — — — (196 ) (7,993 ) Recoveries 516 — 3 10 10 — 4 543 Net charge-offs (7,157 ) — (121 ) 10 10 — (192 ) (7,450 ) Balance December 31, 2017 $ 7,694 $ — $ 10,253 $ 2,525 $ 2,140 $ 942 $ 95 $ 23,649 Allowance for loan losses: Balance December 31, 2015 $ 3,644 $ — $ 5,914 $ 1,221 $ 1,432 $ 820 $ 67 $ 13,098 Provision for loan losses 1,951 — 3,122 (4 ) 434 (72 ) 38 5,469 Charge-offs (722 ) — (129 ) — — — (49 ) (900 ) Recoveries 186 — 43 — 10 — 5 244 Net charge-offs (536 ) — (86 ) — 10 — (44 ) (656 ) Balance December 31, 2016 $ 5,059 $ — $ 8,950 $ 1,217 $ 1,876 $ 748 $ 61 $ 17,911 The following table presents the balance in the allowance for loan losses by portfolio type based on the impairment method as of December 31, 2018 and 2017: Commercial real Commercial real 1-4 family Commercial estate (including estate construction residential and industrial Mortgage warehouse multi-family residential) and land development (including home equity) Residential construction Consumer and other Total (Dollars in thousands) Allowance for loan losses related to: December 31, 2018 Individually evaluated for impairment $ 3,898 $ — $ 2,641 $ 190 $ — $ — $ — $ 6,729 Collectively evaluated for impairment 4,453 — 9,260 2,534 2,242 1,040 73 19,602 Total allowance for loan losses $ 8,351 $ — $ 11,901 $ 2,724 $ 2,242 $ 1,040 $ 73 $ 26,331 Allowance for loan losses related to: December 31, 2017 Individually evaluated for impairment $ 1,640 $ — $ 716 $ — $ — $ — $ — $ 2,356 Collectively evaluated for impairment 6,054 — 9,537 2,525 2,140 942 95 21,293 Total allowance for loan losses $ 7,694 $ — $ 10,253 $ 2,525 $ 2,140 $ 942 $ 95 $ 23,649 The following table presents the recorded investment in loans held for investment by portfolio type based on the impairment method as of December 31, 2018 and 2017: Commercial real Commercial real 1-4 family Commercial estate (including estate construction residential and industrial Mortgage warehouse multi-family residential) and land development (including home equity) Residential construction Consumer and other Total (Dollars in thousands) Recorded investment in loans: December 31, 2018 Individually evaluated for impairment $ 13,504 $ — $ 22,864 $ 4,440 $ 2,742 $ — $ 3 $ 43,553 Collectively evaluated for impairment 688,533 48,274 1,628,048 425,688 646,569 186,411 41,230 3,664,753 Total loans evaluated for impairment $ 702,037 $ 48,274 1,650,912 $ 430,128 $ 649,311 $ 186,411 $ 41,233 $ 3,708,306 Recorded investment in loans: December 31, 2017 Individually evaluated for impairment $ 11,392 $ — $ 20,164 $ 209 $ 948 $ — $ — $ 32,713 Collectively evaluated for impairment 445,737 69,456 1,060,083 243,180 300,271 109,116 10,320 2,238,163 Total loans evaluated for impairment $ 457,129 $ 69,456 $ 1,080,247 $ 243,389 $ 301,219 $ 109,116 $ 10,320 $ 2,270,876
Troubled Debt Restructurings on Financing Receivables	The following table presents information regarding loans modified in a troubled debt restructuring during the years ended December 31, 2018, 2017 and 2016: As of December 31, 2018 2017 2016 Pre- Post- Pre- Post- Pre- Post- Modification of Modification of Modification of Modification of Modification of Modification of Number of Outstanding Outstanding Number of Outstanding Outstanding Number of Outstanding Outstanding Contracts Recorded Investment Recorded Investment Contracts Recorded Investment Recorded Investment Contracts Recorded Investment Recorded Investment (Dollars in thousands) Troubled Debt Restructurings Commercial and industrial 11 $ 2,770 $ 2,770 9 $ 2,399 $ 2,399 21 $ 3,939 $ 3,939 Mortgage warehouse — — — — — — — — — Real estate: Commercial real estate (including multi-family residential) 3 4,288 4,288 6 11,837 11,837 8 7,144 7,144 Commercial real estate construction and land development 1 3,114 3,114 1 210 210 — — — 1-4 family residential (including home equity) — — — 1 86 86 — — — Residential construction — — — — — — — — — Consumer and other — — — — — — 1 6 6 Total 15 $ 10,172 $ 10,172 17 $ 14,532 $ 14,532 30 $ 11,089 $ 11,089
PCI Loans
Accounts Notes And Loans Receivable [Line Items]
Carrying Amount of PCI Loans and Non-PCI Loans	The carrying amount of PCI loans included in the consolidated balance sheet and the related outstanding balance owed at December 31, 2018 are presented in the table below (in thousands): PCI loans: Outstanding balance at December 31, 2018 $ 26,862 Less: Discount 3,599 Recorded investment at December 31, 2018 $ 23,263
Changes in Accretable Yield or Discount Accretion for PCI Loans and Non-PCI Loans	Changes in the accretable yield for PCI loans for the year ended December 31, 2018 were as follows (in thousands): Balance at beginning of period $ — Additions 495 Reclassifications from nonaccretable — Accretion 59 Balance at December 31, 2018 $ 436
Non-PCI Loans
Accounts Notes And Loans Receivable [Line Items]
Carrying Amount of PCI Loans and Non-PCI Loans	The carrying amount of Non-PCI loans included in the consolidated balance sheet and the related outstanding balance owed at December 31, 2018 are presented in the table below (in thousands). Non-PCI loans: Outstanding balance at December 31, 2018 $ 1,124,342 Less: Discount 10,650 Recorded investment at December 31, 2018 $ 1,113,692
Changes in Accretable Yield or Discount Accretion for PCI Loans and Non-PCI Loans	Changes in the discount accretion for Non-PCI loans for the years ended December 31, 2018 were as follows (in thousands): Balance at beginning of period $ — Additions 13,293 Reclassifications from nonaccretable — Accretion 2,643 Balance at December 31, 2018 $ 10,650

FAIR VALUE (Tables)

FAIR VALUE (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value, by Balance Sheet Grouping	The carrying amounts and estimated fair values of financial instruments that are reported on the balance sheet are as follows: As of December 31, 2018 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total (Dollars in thousands) Financial assets Cash and cash equivalents $ 268,947 $ 268,947 $ — $ — $ 268,947 Available for sale securities 337,293 — 337,293 — 337,293 Loans held for investment, net of allowance 3,681,975 — — 3,674,241 3,674,241 FHLB stock 10,941 N/A N/A N/A N/A Accrued interest receivable 17,010 65 3,498 13,447 17,010 Financial liabilities Deposits $ 3,662,536 $ — $ 3,653,244 $ — $ 3,653,244 Accrued interest payable 2,812 — 2,812 — 2,812 Borrowed funds 225,493 — 230,445 — 230,445 Subordinated debt 48,899 — 49,663 — 49,663 As of December 31, 2017 Carrying Estimated Fair Value Amount Level 1 Level 2 Level 3 Total (Dollars in thousands) Financial assets Cash and cash equivalents $ 182,103 $ 182,103 $ — $ — $ 182,103 Available for sale securities 309,615 — 309,615 — 309,615 Loans held for investment, net of allowance 2,247,227 — — 2,238,721 2,238,721 FHLB stock 12,862 N/A N/A N/A N/A Accrued interest receivable 12,194 3 3,296 8,895 12,194 Financial liabilities Deposits $ 2,213,974 $ — $ 2,209,111 $ — $ 2,209,111 Accrued interest payable 610 — 610 — 610 Borrowed funds 282,569 — 288,887 — 288,887 Subordinated debt 48,659 — 48,659 — 48,659
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following tables present fair values for assets measured at fair value on a recurring basis: As of December 31, 2018 Level 1 Level 2 Level 3 Total (Dollars in thousands) Available for sale securities: U.S. Government and agency securities $ — $ 8,685 $ — $ 8,685 Municipal securities — 216,785 — 216,785 Agency mortgage-backed pass-through securities — 66,195 — 66,195 Corporate bonds and other — 45,628 — 45,628 Total $ — $ 337,293 $ — $ 337,293 As of December 31, 2017 Level 1 Level 2 Level 3 Total (Dollars in thousands) Available for sale securities: U.S. Government and agency securities $ — $ 8,715 $ — $ 8,715 Municipal securities — 222,958 — 222,958 Agency mortgage-backed pass-through securities — 31,812 — 31,812 Corporate bonds and other — 46,130 — 46,130 Total $ — $ 309,615 $ — $ 309,615
Fair Value Measurements, Nonrecurring	Certain assets and liabilities are measured at fair value on a nonrecurring basis; that is the instruments are not measured at fair value on an ongoing basis, but are subject to fair value adjustments in certain circumstances such as evidence of impairment. As of December 31, 2018 Level 1 Level 2 Level 3 (Dollars in thousands) Impaired loans: Commercial and industrial $ — $ — $ 5,647 Commercial real estate (including multi-family residential) — — 8,901 Commercial real estate construction and land development — — 2,924 Other real estate owned — — 630 $ — $ — $ 18,102 As of December 31, 2017 Level 1 Level 2 Level 3 (Dollars in thousands) Impaired loans: Commercial and industrial $ — $ — $ 4,012 Commercial real estate (including multi-family residential) — — 7,478 Other real estate owned — — 365 $ — $ — $ 11,855

PREMISES AND EQUIPMENT (Tables)

PREMISES AND EQUIPMENT (Tables)	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Schedule of Premises and Equipment	Premises and equipment are summarized as follows: As of December 31, 2018 2017 (Dollars in thousands) Land $ 11,586 $ 5,376 Buildings 23,455 7,977 Leasehold improvements 5,291 5,059 Furniture, fixtures and equipment 11,858 8,967 Construction in progress 480 320 Total 52,670 27,699 Less: accumulated depreciation 10,953 9,222 Premises and equipment, net $ 41,717 $ 18,477

DEPOSITS (Tables)

DEPOSITS (Tables)	12 Months Ended
	Dec. 31, 2018
Deposit Liabilities [Abstract]
Schedule of Maturities of Time Deposits	Scheduled maturities of time deposits for the next five years are as follows (dollars in thousands): Within one year $ 793,284 After one but within two years 161,877 After two but within three years 89,942 After three but within four years 92,790 After four but within five years 68,598 Total $ 1,206,491

BORROWINGS AND BORROWING CAPA_2

BORROWINGS AND BORROWING CAPACITY (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of Maturities of Long-term Debt	Scheduled principal maturities are as follows (dollars in thousands): 2019 $ — 2020 — 2021 — 2022 — 2023 and thereafter 569 Total $ 569

SUBORDINATED DEBT (Tables)

SUBORDINATED DEBT (Tables)	12 Months Ended
	Dec. 31, 2018
Subordinated Borrowings [Abstract]
Schedule of Subordinated Borrowing	A summary of pertinent information related to the Company's issuances of junior subordinated debentures outstanding at December 31, 2018 is set forth in the table below: Description Issuance Date Trust Preferred Securities Outstanding Interest Rate (1) Junior Subordinated Debt Owed to Trusts Maturity Date (2) Farmers & Merchants Capital Trust II November 13, 2003 $ 7,500 3 month LIBOR + 3.00% $ 7,732 November 8, 2033 Farmers & Merchants Capital Trust III June 30, 2005 3,500 3 month LIBOR + 1.80% 3,609 July 7, 2035 $ 11,341 (1) The 3-month LIBOR in effect as of December 31, 2018 was 2.7902%. (2) All debentures are currently callable.

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Components of Provision for Federal Income Taxes	The components of the provision for federal income taxes are as follows: Years Ended December 31, 2018 2017 2016 (Dollars in thousands) Current $ 8,204 $ 8,320 $ 11,162 Deferred (256 ) 427 (1,608 ) Total $ 7,948 $ 8,747 $ 9,554
Schedule of Effective Income Tax Rate Reconciliation	Reported income tax expense differs from the amounts computed by applying the U.S. federal statutory income tax rate to income before income taxes for the years ended December 31, 2018, 2017 and 2016 due to the following: Years Ended December 31, 2018 2017 2016 (Dollars in thousands) Taxes calculated at statutory rate $ 9,504 $ 9,233 $ 11,342 Increase (decrease) resulting from: Stock based compensation (400 ) (755 ) 67 Effect of tax exempt income (1,284 ) (2,328 ) (1,929 ) Provisional deferred tax adjustment related to reduction in U.S. federal statutory income tax rate — 2,621 — Other, net 128 (24 ) 74 Total $ 7,948 $ 8,747 $ 9,554
Schedule of Deferred Tax Assets and Liabilities	Deferred tax assets and liabilities are as follows: As of December 31, 2018 2017 (Dollars in thousands) Deferred tax assets: Allowance for credit losses $ 5,898 $ 5,284 Net unrealized loss on available for sale securities 761 — Deferred compensation 366 177 Total deferred tax assets 7,025 5,461 Deferred tax liabilities: Core deposit intangible and other purchase accounting adjustments (2,718 ) (1,100 ) Net unrealized gain on available for sale securities — (65 ) Premises and equipment basis difference (2,035 ) (321 ) Total deferred tax liabilities (4,753 ) (1,486 ) Net deferred tax assets $ 2,272 $ 3,975

STOCK BASED COMPENSATION (Table

STOCK BASED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The Black-Scholes pricing model utilizes certain assumptions noted in the table below. 2018 2017 2016 Risk-free interest rate 2.72 % 2.40 % 1.76 % Expected term 10.00 10.00 10.00 Expected stock price volatility 29.26 % 29.70 % 34.60 % Dividend yield — — —
Schedule of Share-based Compensation, Stock Options, Activity	A summary of the activity in the stock option plans during the years ended December 31, 2018 and 2017 is set forth below: Weighted Weighted Average Average Aggregate Number of Exercise Remaining Intrinsic Options Price Contractual Term Value (In thousands) (In years) (In thousands) Options outstanding, January 1, 2017 935 $ 18.21 6.23 $ 16,773 Options granted 64 36.88 Options exercised (215 ) 17.50 Options forfeited (9 ) 23.35 Options outstanding, December 31, 2017 775 $ 19.94 5.72 $ 13,718 Options granted 4 40.40 Options assumed 299 12.83 Options exercised (244 ) 13.88 Options forfeited (32 ) 29.53 Options outstanding, December 31, 2018 802 $ 18.88 4.61 $ 10,830 Options vested and exercisable, December 31, 2018 677 $ 17.32 4.09 $ 10,193
Schedule of Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Grant Date Intrinsic Value	Information related to the stock option plans during each year is as follows: 2018 2017 2016 (In thousands) Intrinsic value of options exercised $ 3,254 $ 3,371 $ 1,128 Cash received from option exercises 3,393 3,743 1,782 Weighted average fair value of options granted $ 18.00 $ 16.55 $ 10.51
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	A summary of the activity of the nonvested shares of restricted stock as of December 31, 2018 and 2017 including changes during the years then ended is as follows: Weighted Average Grant Number of Date Fair Shares Value (Shares in thousands) Nonvested share awards outstanding, January 1, 2017 24 $ 18.31 Share awards granted 28 36.17 Share awards vested (11 ) 18.32 Unvested share awards forfeited or cancelled — — Nonvested share awards outstanding, December 31, 2017 41 $ 30.46 Share awards granted 122 39.04 Share awards vested (20 ) 30.12 Unvested share awards forfeited or cancelled — — Nonvested share awards outstanding, December 31, 2018 143 $ 37.48

OFF-BALANCE SHEET ARRANGEMENT_2

OFF-BALANCE SHEET ARRANGEMENTS, COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Schedule of Fair Value, Off-balance Sheet Risks	The contractual amounts of financial instruments with off-balance sheet risk are as follows: December 31, 2018 December 31, 2017 Fixed Variable Fixed Variable Rate Rate Rate Rate (Dollars in thousands) Commitments to extend credit $ 471,440 $ 530,546 $ 369,573 $ 250,467 Standby letters of credit 14,217 9,067 15,445 1,725 Total $ 485,657 $ 539,613 $ 385,018 $ 252,192
Schedule of Future Minimum Rental Payments for Operating Leases	The following table presents a summary of non-cancelable future operating lease commitments as of December 31, 2018 (dollars in thousands): 2019 $ 2,559 2020 1,987 2021 1,731 2022 1,510 2023 1,042 Thereafter 4,083 $ 12,912

REGULATORY CAPITAL MATTERS (Tab

REGULATORY CAPITAL MATTERS (Tables)	12 Months Ended
	Dec. 31, 2018
Banking And Thrift [Abstract]
Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations	The following is a summary of the Company’s and the Bank’s actual and required capital ratios at December 31, 2018 and 2017: To Be Categorized As Well Capitalized Under Actual For Capital Adequacy Purposes Minimum Required Plus Capital Conservation Buffer Prompt Corrective Action Provisions Amount Ratio Amount Ratio Amount Ratio Amount Ratio (Dollars in thousands) ALLEGIANCE BANCSHARES, INC. (Consolidated) As of December 31, 2018 Total Capital (to risk weighted assets) $ 531,453 13.70 % $ 310,295 8.00 % $ 383,020 9.875 % N/A N/A Common Equity Tier 1 Capital (to risk weighted assets) 456,223 11.76 % 174,541 4.50 % 247,266 6.375 % N/A N/A Tier I Capital (to risk weighted assets) 465,637 12.01 % 232,721 6.00 % 305,446 7.875 % N/A N/A Tier I Capital (to average tangible assets) 465,637 10.61 % 175,621 4.00 % 175,621 4.000 % N/A N/A As of December 31, 2017 Total Capital (to risk weighted assets) $ 336,829 13.43 % $ 200,687 8.00 % $ 232,044 9.250 % N/A N/A Common Equity Tier 1 Capital (to risk weighted assets) 264,521 10.54 % 112,886 4.50 % 144,244 5.750 % N/A N/A Tier I Capital (to risk weighted assets) 273,825 10.92 % 150,515 6.00 % 181,872 7.250 % N/A N/A Tier I Capital (to average tangible assets) 273,825 9.84 % 111,274 4.00 % 111,274 4.000 % N/A N/A ALLEGIANCE BANK As of December 31, 2018 Total Capital (to risk weighted assets) $ 524,660 13.53 % $ 310,179 8.00 % $ 382,877 9.875 % $ 387,724 10.00 % Common Equity Tier 1 Capital (to risk weighted assets) 458,844 11.83 % 174,476 4.50 % 247,174 6.375 % 252,021 6.50 % Tier I Capital (to risk weighted assets) 458,844 11.83 % 232,634 6.00 % 305,333 7.875 % 310,179 8.00 % Tier I Capital (to average tangible assets) 458,844 10.45 % 175,552 4.00 % 175,552 4.000 % 219,440 5.00 % As of December 31, 2017 Total Capital (to risk weighted assets) $ 331,872 13.24 % $ 200,596 8.00 % $ 231,939 9.250 % $ 250,745 10.00 % Common Equity Tier 1 Capital (to risk weighted assets) 268,868 10.72 % 112,835 4.50 % 144,179 5.750 % 162,985 6.50 % Tier I Capital (to risk weighted assets) 268,868 10.72 % 150,447 6.00 % 181,790 7.250 % 200,596 8.00 % Tier I Capital (to average tangible assets) 268,868 9.67 % 111,230 4.00 % 111,230 4.000 % 139,037 5.00 %

EARNINGS PER COMMON SHARE (Tabl

EARNINGS PER COMMON SHARE (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	Restricted shares are considered outstanding at the date of grant, accounted for as participating securities and are included in basic and diluted weighted average common shares outstanding Year Ended December 31, 2018 2017 2016 Per Share Per Share Per Share Amount Amount Amount Amount Amount Amount (Amounts in thousands, except per share data) Net income attributable to shareholders $ 37,309 $ 17,632 $ 22,851 Basic: Weighted average shares outstanding 15,485 $ 2.41 13,125 $ 1.34 12,873 $ 1.78 Diluted: Add incremental shares for: Dilutive effect of stock option exercises 288 333 201 Total 15,773 $ 2.37 13,458 $ 1.31 13,074 $ 1.75

PARENT COMPANY ONLY FINANCIAL_2

PARENT COMPANY ONLY FINANCIAL STATEMENTS (Tables)	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
Schedule of Condensed Balance Sheet	ALLEGIANCE BANCSHARES, INC (PARENT COMPANY ONLY) CONDENSED BALANCE SHEETS December 31, 2018 2017 (Dollars in thousands) ASSETS Cash and due from banks $ 6,780 $ 4,857 Investment in subsidiary 705,947 311,553 Other assets 1,026 791 TOTAL $ 713,753 $ 317,201 LIABILITIES AND SHAREHOLDERS’ EQUITY LIABILITIES: Other borrowed funds $ 492 $ 569 Subordinated debentures 9,414 9,304 Accrued interest payable and other liabilities 862 463 Total liabilities 10,768 10,336 SHAREHOLDERS’ EQUITY: Common stock 21,938 13,227 Capital surplus 571,804 218,408 Retained earnings 112,131 74,894 Accumulated other comprehensive (loss) income (2,888 ) 336 Total shareholders’ equity 702,985 306,865 TOTAL $ 713,753 $ 317,201
Schedule of Condensed Income Statement	ALLEGIANCE BANCSHARES, INC (PARENT COMPANY ONLY) CONDENSED STATEMENTS OF INCOME For the Years Ended December 31, 2018 2017 2016 (Dollars in thousands) OPERATING INCOME: Other income $ 16 $ 13 $ 11 Total income 16 13 11 OPERATING EXPENSE: Interest expense on borrowed funds 38 33 30 Other expenses 1,692 1,465 1,204 Total operating expense 1,730 1,498 1,234 INCOME BEFORE INCOME TAX BENEFIT AND EQUITY IN UNDISTRIBUTED EARNINGS OF SUBSIDIARIES (1,714 ) (1,485 ) (1,223 ) INCOME TAX BENEFIT 360 756 428 INCOME BEFORE EQUITY IN UNDISTRIBUTED EARNINGS OF SUBSIDIARIES (1,354 ) (729 ) (795 ) EQUITY IN UNDISTRIBUTED EARNINGS OF SUBSIDIARIES 38,663 18,361 23,646 NET INCOME $ 37,309 $ 17,632 $ 22,851
Schedule of Condensed Cash Flow Statement	ALLEGIANCE BANCSHARES, INC (PARENT COMPANY ONLY) CONDENSED STATEMENTS OF CASH FLOWS For the Years Ended December 31, 2018 2017 2016 (Dollars in thousands) CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 37,309 $ 17,632 $ 22,851 Adjustments to reconcile net income to net cash used in operating activities: Equity in undistributed earnings of subsidiaries (38,663 ) (18,361 ) (23,646 ) Net amortization of discount on subordinated debentures 110 107 107 Increase in other assets (236 ) (378 ) (399 ) Increase (decrease) in accrued interest payable and other liabilities 279 (377 ) 186 Net cash used in operating activities (1,201 ) (1,377 ) (901 ) CASH FLOWS FROM INVESTING ACTIVITIES: Capital investment in bank subsidiary — (21,000 ) — Net cash used in investing activities — (21,000 ) — CASH FLOWS FROM FINANCING ACTIVITIES: Proceeds from issuance of common stock 3,552 4,248 2,006 Proceeds from initial public offering — — — Stock based compensation expense 1,685 1,780 1,501 (Repurchase) issuance of treasury stock (2,113 ) — 38 Net cash provided by financing activities 3,124 6,028 3,545 NET CHANGE IN CASH AND CASH EQUIVALENTS 1,923 (16,349 ) 2,644 CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD 4,857 21,206 18,562 CASH AND CASH EQUIVALENTS, END OF PERIOD $ 6,780 $ 4,857 $ 21,206

QUARTERLY FINANCIAL DATA (UNA_2

QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	Net Income Interest Net Interest Attributable to Earnings Per Share (1) Income Income Common Shareholders Basic Diluted (Dollars in thousands, except per share data) 2018 First quarter $ 32,391 $ 26,889 $ 7,711 $ 0.58 $ 0.57 Second quarter 34,193 27,816 7,556 0.57 0.55 Third quarter 35,336 28,036 8,879 0.66 0.65 Fourth quarter 56,303 45,838 13,163 0.60 0.59 2017 First quarter $ 27,512 $ 24,128 $ 6,047 $ 0.46 $ 0.45 Second quarter 28,987 25,107 5,395 0.41 0.40 Third quarter 30,901 26,997 2,986 0.23 0.22 Fourth quarter 32,038 27,436 3,204 0.24 0.24 (1) Earnings per share are computed independently for each of the quarters presented and therefore may not total earnings per share for the year

NATURE OF OPERATIONS AND SUMM_3

NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING AND REPORTING POLICIES (Details) $ in Thousands	Jan. 01, 2019USD ($)	Oct. 01, 2018	Dec. 31, 2018USD ($)officeBankSegment
New Accounting Pronouncement Early Adoption [Line Items]
Number of offices in which entity operates | office			28
Number of banks in which entity operates | Bank			27
Other real estate owned			$ 630
Percentage of recognition threshold for which the largest amount of tax benefit is relized upon ultimate settlement with the related tax authority			50.00%
Number of reportable segments | Segment			1
Cumulative effect of new accounting principle in period of adoption			$ 72
Retained Earnings
New Accounting Pronouncement Early Adoption [Line Items]
Cumulative effect of new accounting principle in period of adoption			$ 72
ASU 2016-02 | Subsequent Event
New Accounting Pronouncement Early Adoption [Line Items]
Decrease in tier 1 capital to risk weighted assets ratio	0.05%
ASU 2017-08 | Subsequent Event
New Accounting Pronouncement Early Adoption [Line Items]
Cumulative effect of adopting new accounting principle in period of adoption	$ 1,700
Minimum
New Accounting Pronouncement Early Adoption [Line Items]
Premises and equipment, useful life			3 years
Minimum | ASU 2016-02
New Accounting Pronouncement Early Adoption [Line Items]
Recognition of lease liabilities			$ 15,000,000
Recognition of right-of-use assets			$ 15,000,000
Minimum | Core Deposits
New Accounting Pronouncement Early Adoption [Line Items]
Intangibles, useful life			7 years
Maximum
New Accounting Pronouncement Early Adoption [Line Items]
Premises and equipment, useful life			40 years
Maximum | ASU 2016-02
New Accounting Pronouncement Early Adoption [Line Items]
Recognition of lease liabilities			$ 17,000,000
Recognition of right-of-use assets			$ 17,000,000
Maximum | Core Deposits
New Accounting Pronouncement Early Adoption [Line Items]
Intangibles, useful life			10 years
Post Oak Bancshares, Inc.
New Accounting Pronouncement Early Adoption [Line Items]
Effective date of acqusition		Oct. 1, 2018	Oct. 1, 2018
Post Oak Bancshares, Inc. | Minimum
New Accounting Pronouncement Early Adoption [Line Items]
Intangibles, useful life		10 years
Houston
New Accounting Pronouncement Early Adoption [Line Items]
Number of loan production offices in which entity operates | office			1
Beaumont
New Accounting Pronouncement Early Adoption [Line Items]
Number of loan production offices in which entity operates | office			1

ACQUISITIONS - Narrative (Detai

ACQUISITIONS - Narrative (Details) $ / shares in Units, $ in Thousands	Oct. 01, 2018USD ($)branch$ / sharesshares	Dec. 31, 2018USD ($)$ / shares	Dec. 31, 2017$ / shares	Sep. 28, 2018USD ($)$ / shares
Business Acquisition [Line Items]
Options exercised | $ / shares		$ 13.88	$ 17.50
Goodwill, acquired during period		$ 183,736
Post Oak Bancshares, Inc.
Business Acquisition [Line Items]
Effective date of acqusition	Oct. 1, 2018	Oct. 1, 2018
Number of branches | branch	13
Numbner of shares issued in acquisition | shares	8,402,010
Cash paid for acquisition	$ 21
Number of shares per common share or option to purchase common shares	0.7017
Option issued in acquisition to purchase common shares | shares	299,352
Options exercised | $ / shares	$ 12.83
Business acquisition, share price | $ / shares				$ 41.70
Business acquisition, equity transaction value				$ 359,000
Goodwill, acquired during period	$ 183,700
Pre-tax acquisition and merger-related expenses		$ 1,700
Post Oak Bancshares, Inc. | Minimum
Business Acquisition [Line Items]
Intangibles, useful life	10 years
Post Oak Bancshares, Inc. | Houston, Texas
Business Acquisition [Line Items]
Number of branches | branch	12
Post Oak Bancshares, Inc. | Beaumont, TX
Business Acquisition [Line Items]
Number of branches | branch	1

ACQUISITIONS - Allocation of th

ACQUISITIONS - Allocation of the Purchase Price to Assets and Liabilities (Details) - USD ($) $ in Thousands	Oct. 01, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill		$ 223,125	$ 39,389	$ 39,389	$ 39,389
Post Oak Bancshares, Inc.
Business Acquisition [Line Items]
Stock options issued (299,352)	$ 8,639
Cash in lieu of fractional shares	21
Total consideration paid	359,024
Cash and cash equivalents	230,416
Investment securities	42,779
Loans	1,164,279
Premises and equipment	21,988
Core deposit intangibles	25,128
Other assets	18,078
Total assets acquired	1,502,668
Deposits	1,291,310
Other borrowed funds	30,000
Other liabilities	6,070
Total liabilities assumed	1,327,380
Fair value of net assets acquired	175,288
Goodwill	183,736
Post Oak Bancshares, Inc. | Common Stock
Business Acquisition [Line Items]
Common shares issued (8,402,010 shares)	$ 350,364

ACQUISITIONS - Allocation of _2

ACQUISITIONS - Allocation of the Purchase Price to Assets and Liabilities - Narrative (Details) - Post Oak Bancshares, Inc.	Oct. 01, 2018shares
Business Acquisition [Line Items]
Numbner of shares issued in acquisition	8,402,010
Option issued in acquisition to purchase common shares	299,352

ACQUISITIONS - Details of Loans

ACQUISITIONS - Details of Loans Acquired (Details) $ in Thousands	Oct. 01, 2018USD ($)
Business Acquisition [Line Items]
Discount	$ (16,950)
Contractual Balance
Business Acquisition [Line Items]
Acquired loans receivable	1,181,231
Fair Value
Business Acquisition [Line Items]
Acquired loans receivable	1,164,281
Commercial and industrial
Business Acquisition [Line Items]
Discount	(3,894)
Commercial and industrial | Contractual Balance
Business Acquisition [Line Items]
Acquired loans receivable	221,098
Commercial and industrial | Fair Value
Business Acquisition [Line Items]
Acquired loans receivable	217,204
Real estate | Commercial real estate (including multi-family residential)
Business Acquisition [Line Items]
Discount	(7,435)
Real estate | Commercial real estate (including multi-family residential) | Contractual Balance
Business Acquisition [Line Items]
Acquired loans receivable	450,947
Real estate | Commercial real estate (including multi-family residential) | Fair Value
Business Acquisition [Line Items]
Acquired loans receivable	443,512
Real estate | Commercial real estate construction and land development
Business Acquisition [Line Items]
Discount	(1,999)
Real estate | Commercial real estate construction and land development | Contractual Balance
Business Acquisition [Line Items]
Acquired loans receivable	167,386
Real estate | Commercial real estate construction and land development | Fair Value
Business Acquisition [Line Items]
Acquired loans receivable	165,387
Real estate | 1-4 family residential (including home equity)
Business Acquisition [Line Items]
Discount	(3,205)
Real estate | 1-4 family residential (including home equity) | Contractual Balance
Business Acquisition [Line Items]
Acquired loans receivable	288,304
Real estate | 1-4 family residential (including home equity) | Fair Value
Business Acquisition [Line Items]
Acquired loans receivable	285,099
Real estate | Residential construction | Contractual Balance
Business Acquisition [Line Items]
Acquired loans receivable	23,812
Real estate | Residential construction | Fair Value
Business Acquisition [Line Items]
Acquired loans receivable	23,812
Consumer and other
Business Acquisition [Line Items]
Discount	(417)
Consumer and other | Contractual Balance
Business Acquisition [Line Items]
Acquired loans receivable	29,684
Consumer and other | Fair Value
Business Acquisition [Line Items]
Acquired loans receivable	$ 29,267

ACQUISITIONS - Schedule of PCI

ACQUISITIONS - Schedule of PCI Loans and Non-PCI Loans Acquired in Transaction (Details) $ in Thousands	Oct. 01, 2018USD ($)
PCI Loans
Business Acquisition [Line Items]
Contractually required principal and interest payments	$ 28,340
Contractual cash flows not expected to be collected (nonaccretable difference)	3,163
Expected cash flows at acquisition	25,177
Interest component of expected cash flows (accretable yield)	495
Fair value of loans acquired with deterioration of credit quality	24,682
Non-PCI Loans
Business Acquisition [Line Items]
Contractually required principal and interest payments	1,153,317
Accretable discount	13,293
Fair value at acquisition	$ 1,140,024

ACQUISITIONS - Business Acquisi

ACQUISITIONS - Business Acquisition, Pro Forma Information (Details) - Post Oak Bancshares, Inc. - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Net interest income	$ 170,801	$ 165,612
Noninterest income	10,060	9,543
Net income	$ 41,807	$ 35,107
Basic earnings per common share	$ 2.70	$ 1.63
Diluted earnings per common share	$ 2.65	$ 1.61

GOODWILL AND CORE DEPOSIT INT_3

GOODWILL AND CORE DEPOSIT INTANGIBLE ASSETS - Changes in Carrying Amount of Goodwill and Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill
Balance, beginning	$ 39,389	$ 39,389	$ 39,389
Goodwill, acquired during period	183,736
Core deposit intangibles amortization	1,815	781	785
Balance, ending	223,125	39,389	39,389
Core Deposit Intangible Assets
Balance, beginning	3,274
Amortization	(1,815)	(781)	(785)
Balance, ending	26,587	3,274
Core Deposits
Goodwill
Core deposit intangibles amortization	1,815	781	785
Core Deposit Intangible Assets
Balance, beginning	3,274	4,055	5,230
Sale of branch assets			(390)
Acquisition of Post Oak Bancshares, Inc.	25,128
Amortization	(1,815)	(781)	(785)
Balance, ending	$ 26,587	$ 3,274	$ 4,055

GOODWILL AND CORE DEPOSIT INT_4

GOODWILL AND CORE DEPOSIT INTANGIBLE ASSETS - Narrative (Details)	Oct. 01, 2018USD ($)
Acquisition of F&M
Business Acquisition [Line Items]
Goodwill impairment	$ 0

GOODWILL AND CORE DEPOSIT INT_5

GOODWILL AND CORE DEPOSIT INTANGIBLE ASSETS - Estimated Aggregate Future Amortization Expense for Core Deposit Intangibles (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
2019	$ 4,712
2020	3,922
2021	3,296
2022	3,003
2023	2,323
Thereafter	9,331
Total	$ 26,587	$ 3,274

CASH AND DUE FROM BANKS - Narra

CASH AND DUE FROM BANKS - Narrative (Details) $ in Millions	Dec. 31, 2018USD ($)
Cash And Cash Equivalents [Abstract]
Restricted cash	$ 27.7

SECURITIES - Amortized Cost and

SECURITIES - Amortized Cost and Fair Value of Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 340,928	$ 309,098
Gross Unrealized Gains	1,671	2,923
Gross Unrealized Losses	(5,306)	(2,406)
Fair Value	337,293	309,615
U.S. Government and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,570	8,507
Gross Unrealized Gains	161	232
Gross Unrealized Losses	(46)	(24)
Fair Value	8,685	8,715
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	219,068	222,330
Gross Unrealized Gains	1,258	2,470
Gross Unrealized Losses	(3,541)	(1,842)
Fair Value	216,785	222,958
Agency mortgage-backed pass-through securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	66,987	32,014
Gross Unrealized Gains	237	159
Gross Unrealized Losses	(1,029)	(361)
Fair Value	66,195	31,812
Corporate bonds and other
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	46,303	46,247
Gross Unrealized Gains	15	62
Gross Unrealized Losses	(690)	(179)
Fair Value	$ 45,628	$ 46,130

SECURITIES - Amortized Cost a_2

SECURITIES - Amortized Cost and Fair Value of Investment Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Amortized Cost
Due in one year or less	$ 14,877
Due after one year through five years	73,675
Due after five years through ten years	87,391
Due after ten years	97,998
Subtotal	273,941
Agency mortgage-backed pass through securities	66,987
Amortized Cost	340,928	$ 309,098
Fair Value
Due in one year or less	14,823
Due after one year through five years	72,790
Due after five years through ten years	86,880
Due after ten years	96,605
Subtotal	271,098
Agency mortgage-backed pass through securities	66,195
Total	$ 337,293	$ 309,615

SECURITIES - Securities in a Co

SECURITIES - Securities in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 28, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Securities in a Continuous Unrealized Loss Position, Less than 12 months, Estimated Fair Value	$ 41,941	$ 88,800
Securities in a Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(273)	(810)
Securities in a Continuous Unrealized Loss Position, More than 12 Months, Estimated Fair Value	190,184	65,999
Securities in a Continuous Unrealized Loss Position, More than 12 Months Unrealized Losses	(5,033)	(1,596)
Securities in a Continuous Unrealized Loss Position, Total Estimated Fair Value	232,125	154,799
Securities in a Continuous Unrealized Loss Position, Total Unrealized Losses	(5,306)	(2,406)
U.S. Government and agency securities
Debt Securities, Available-for-sale [Line Items]
Securities in a Continuous Unrealized Loss Position, Less than 12 months, Estimated Fair Value	999	3,110
Securities in a Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses		(9)
Securities in a Continuous Unrealized Loss Position, More than 12 Months, Estimated Fair Value	1,417	595
Securities in a Continuous Unrealized Loss Position, More than 12 Months Unrealized Losses	(46)	(15)
Securities in a Continuous Unrealized Loss Position, Total Estimated Fair Value	2,416	3,705
Securities in a Continuous Unrealized Loss Position, Total Unrealized Losses	(46)	(24)
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Securities in a Continuous Unrealized Loss Position, Less than 12 months, Estimated Fair Value	10,140	42,249
Securities in a Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(29)	(517)
Securities in a Continuous Unrealized Loss Position, More than 12 Months, Estimated Fair Value	136,934	56,483
Securities in a Continuous Unrealized Loss Position, More than 12 Months Unrealized Losses	(3,512)	(1,325)
Securities in a Continuous Unrealized Loss Position, Total Estimated Fair Value	147,074	98,732
Securities in a Continuous Unrealized Loss Position, Total Unrealized Losses	(3,541)	(1,842)
Agency mortgage-backed pass-through securities
Debt Securities, Available-for-sale [Line Items]
Securities in a Continuous Unrealized Loss Position, Less than 12 months, Estimated Fair Value	17,168	13,238
Securities in a Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(209)	(105)
Securities in a Continuous Unrealized Loss Position, More than 12 Months, Estimated Fair Value	22,819	8,921
Securities in a Continuous Unrealized Loss Position, More than 12 Months Unrealized Losses	(820)	(256)
Securities in a Continuous Unrealized Loss Position, Total Estimated Fair Value	39,987	22,159
Securities in a Continuous Unrealized Loss Position, Total Unrealized Losses	(1,029)	(361)
Corporate bonds and other
Debt Securities, Available-for-sale [Line Items]
Securities in a Continuous Unrealized Loss Position, Less than 12 months, Estimated Fair Value	13,634	30,203
Securities in a Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(35)	(179)
Securities in a Continuous Unrealized Loss Position, More than 12 Months, Estimated Fair Value	29,014
Securities in a Continuous Unrealized Loss Position, More than 12 Months Unrealized Losses	(655)
Securities in a Continuous Unrealized Loss Position, Total Estimated Fair Value	42,648	30,203
Securities in a Continuous Unrealized Loss Position, Total Unrealized Losses	$ (690)	$ (179)

SECURITIES - Narrative (Details

SECURITIES - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Securities, Available-for-sale [Line Items]
Payment to acquire securities	$ 2,334,149,000	$ 2,038,323,000	$ 2,730,524,000
Proceeds from sales of available for sale securities	12,701,000	39,125,000	2,500,000
Gross realized gains		18,000	$ 30,000
Security owned and pledged as collateral	28,900,000	$ 5,000,000
Post Oak Bancshares, Inc.
Debt Securities, Available-for-sale [Line Items]
Payment to acquire securities	42,800,000
Proceeds from sales of available for sale securities	12,700,000
Gross realized gain (loss)	0
Security owned and pledged as collateral	$ 25,900,000

LOANS AND ALLOWANCE FOR LOAN _3

LOANS AND ALLOWANCE FOR LOAN LOSSES - Loan Portfolio (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	$ 3,708,306	$ 2,270,876
Allowance for loan losses	(26,331)	(23,649)	$ (17,911)	$ (13,098)
Loans, net	3,681,975	2,247,227
Commercial and industrial
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	702,037	457,129
Allowance for loan losses	(8,351)	(7,694)	(5,059)	(3,644)
Mortgage warehouse
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	48,274	69,456
Allowance for loan losses	0	0	0	0
Real estate | Commercial real estate (including multi-family residential)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	1,650,912	1,080,247
Real estate | Commercial real estate construction and land development
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	430,128	243,389
Real estate | 1-4 family residential (including home equity)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	649,311	301,219
Real estate | Residential construction
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	186,411	109,116
Consumer and other
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	41,233	10,320
Allowance for loan losses	$ (73)	$ (95)	$ (61)	$ (67)

LOANS AND ALLOWANCE FOR LOAN _4

LOANS AND ALLOWANCE FOR LOAN LOSSES - Loan Portfolio, Narrative (Details) - Mortgage warehouse	12 Months Ended
	Dec. 31, 2018
Revolving line of credit facility
Accounts Notes And Loans Receivable [Line Items]
Debt instrument, term	24 months
Mortgage promissory notes secured by residential property | Minimum
Accounts Notes And Loans Receivable [Line Items]
Debt instrument, term	10 days
Mortgage promissory notes secured by residential property | Maximum
Accounts Notes And Loans Receivable [Line Items]
Debt instrument, term	20 days
Mortgage promissory notes secured by commercial property | Minimum
Accounts Notes And Loans Receivable [Line Items]
Debt instrument, term	40 days
Mortgage promissory notes secured by commercial property | Maximum
Accounts Notes And Loans Receivable [Line Items]
Debt instrument, term	50 days

LOANS AND ALLOWANCE FOR LOAN _5

LOANS AND ALLOWANCE FOR LOAN LOSSES - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts Notes And Loans Receivable [Line Items]
Owner-occupied loans to commercial real estate loans	51.40%
Maximum loans amount to appraised value	90.00%
Loans outstanding	$ 7,870	$ 4,368
Impaired, interest lost on nonaccrual loans	1,000	733,000
Average recorded investment	44,818	34,059	$ 22,500
Interest income, accrual method	1,282	922	862
Loans and leases receivable, allowance	$ 26,331	$ 23,649	17,911	$ 13,098
Loans and leases receivable, allowance, percentage	0.71%	1.04%
Acquired loans, remaining acquisition accounting discount	$ 14,200
Recorded investment	33,100	$ 25,600
Change in method of calculating impairment	3,000	2,200
Troubled debt restructuring, write-down	272	136	$ 211
Troubled debt restructuring, addition	200
Troubled debt restructuring, addition, outstanding	$ 10,200	$ 9,800
Minimum
Accounts Notes And Loans Receivable [Line Items]
Owner-occupied commercial real estate loans, amortization period	10 years
Mortgage loan, term	5 years
Mortgage loan, amortization period	10 years
Consumer and other loans, term	12 months
Maximum
Accounts Notes And Loans Receivable [Line Items]
Owner-occupied commercial real estate loans, amortization period	20 years
Mortgage loan, term	7 years
Mortgage loan, amortization period	20 years
Consumer and other loans, term	60 months

LOANS AND ALLOWANCE FOR LOAN _6

LOANS AND ALLOWANCE FOR LOAN LOSSES - Carrying Amount of PCI Loans and Non-PCI Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Outstanding balance at December 31, 2018	$ 44,364	$ 33,824
Recorded investment at December 31, 2018	43,553	$ 32,713
PCI Loans
Accounts Notes And Loans Receivable [Line Items]
Outstanding balance at December 31, 2018	26,862
Less: Discount	3,599
Recorded investment at December 31, 2018	23,263
Non-PCI Loans
Accounts Notes And Loans Receivable [Line Items]
Outstanding balance at December 31, 2018	1,124,342
Less: Discount	10,650
Recorded investment at December 31, 2018	$ 1,113,692

LOANS AND ALLOWANCE FOR LOAN _7

LOANS AND ALLOWANCE FOR LOAN LOSSES - Changes in Accretable Yield or Discount Accretion for PCI Loans and Non-PCI Loans (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
PCI Loans
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	$ 0
Additions	495
Reclassifications from nonaccretable	0
Accretion	59
Balance at December 31, 2018	436
Non-PCI Loans
Accounts Notes And Loans Receivable [Line Items]
Balance at beginning of period	0
Additions	13,293
Reclassifications from nonaccretable	0
Accretion	2,643
Balance at December 31, 2018	$ 10,650

LOANS AND ALLOWANCE FOR LOAN _8

LOANS AND ALLOWANCE FOR LOAN LOSSES - Analysis Of Activity with Related-party Loans (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Loans and Leases Receivable, Related Parties [Roll Forward]
Beginning balance on January 1	$ 4,368
New loans and reclassified related loans	5,003
Repayments	(1,501)
Ending balance on December 31	$ 7,870

LOANS AND ALLOWANCE FOR LOAN _9

LOANS AND ALLOWANCE FOR LOAN LOSSES - Aging Analysis of the Recorded Investment in Past Due Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing	$ 10,487	$ 12,947
Nonaccrual Loans	32,953	13,328
Current Loans	3,664,866	2,244,601
Total loans evaluated for impairment	3,708,306	2,270,876
Financing Receivables, 30 to 89 Days Past Due
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing	10,487	12,947
Commercial and industrial
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing	1,951	1,069
Nonaccrual Loans	10,861	6,437
Current Loans	689,225	449,623
Total loans evaluated for impairment	702,037	457,129
Commercial and industrial | Financing Receivables, 30 to 89 Days Past Due
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing	1,951	1,069
Mortgage warehouse
Accounts Notes And Loans Receivable [Line Items]
Current Loans	48,274	69,456
Total loans evaluated for impairment	48,274	69,456
Real estate | Commercial real estate (including multi-family residential)
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing	3,502	4,932
Nonaccrual Loans	17,776	6,110
Current Loans	1,629,634	1,069,205
Total loans evaluated for impairment	1,650,912	1,080,247
Real estate | Commercial real estate (including multi-family residential) | Financing Receivables, 30 to 89 Days Past Due
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing	3,502	4,932
Real estate | Commercial real estate construction and land development
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing	1,300	5,274
Nonaccrual Loans	974
Current Loans	427,854	238,115
Total loans evaluated for impairment	430,128	243,389
Real estate | Commercial real estate construction and land development | Financing Receivables, 30 to 89 Days Past Due
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing	1,300	5,274
Real estate | 1-4 family residential (including home equity)
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing	3,643	924
Nonaccrual Loans	3,201	781
Current Loans	642,467	299,514
Total loans evaluated for impairment	649,311	301,219
Real estate | 1-4 family residential (including home equity) | Financing Receivables, 30 to 89 Days Past Due
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing	3,643	924
Real estate | Residential construction
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing		674
Current Loans	186,411	108,442
Total loans evaluated for impairment	186,411	109,116
Real estate | Residential construction | Financing Receivables, 30 to 89 Days Past Due
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing		674
Consumer and other
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing	91	74
Nonaccrual Loans	141
Current Loans	41,001	10,246
Total loans evaluated for impairment	41,233	10,320
Consumer and other | Financing Receivables, 30 to 89 Days Past Due
Accounts Notes And Loans Receivable [Line Items]
Loans Past Due and Still Accruing	$ 91	$ 74

LOANS AND ALLOWANCE FOR LOAN_10

LOANS AND ALLOWANCE FOR LOAN LOSSES - Impaired Loans by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
With no related allowance recorded:
Recorded investment with no related allowance recorded	$ 19,747	$ 19,104
Unpaid principal balance with no related allowance recorded	20,163	19,978
With an allowance recorded:
Impaired financing receivable, with related allowance, recorded investment	23,806	13,609
Impaired financing receivable, with related allowance, unpaid principal balance	24,201	13,846
Related Allowance	6,729	2,356
Total:
Recorded Investment	43,553	32,713
Unpaid Principal Balance	44,364	33,824
Related Allowance	6,729	2,356
Commercial and industrial
With no related allowance recorded:
Recorded investment with no related allowance recorded	4,354	5,792
Unpaid principal balance with no related allowance recorded	4,771	6,666
With an allowance recorded:
Impaired financing receivable, with related allowance, recorded investment	9,150	5,600
Impaired financing receivable, with related allowance, unpaid principal balance	9,545	5,652
Related Allowance	3,898	1,640
Total:
Recorded Investment	13,504	11,392
Unpaid Principal Balance	14,316	12,318
Related Allowance	3,898	1,640
Mortgage warehouse
With no related allowance recorded:
Recorded investment with no related allowance recorded	0	0
Unpaid principal balance with no related allowance recorded	0	0
With an allowance recorded:
Impaired financing receivable, with related allowance, recorded investment	0	0
Impaired financing receivable, with related allowance, unpaid principal balance	0	0
Related Allowance	0	0
Total:
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Real estate | Commercial real estate (including multi-family residential)
With no related allowance recorded:
Recorded investment with no related allowance recorded	11,322	12,155
Unpaid principal balance with no related allowance recorded	11,322	12,155
With an allowance recorded:
Impaired financing receivable, with related allowance, recorded investment	11,542	8,009
Impaired financing receivable, with related allowance, unpaid principal balance	11,542	8,194
Related Allowance	2,641	716
Total:
Recorded Investment	22,864	20,164
Unpaid Principal Balance	22,864	20,349
Related Allowance	2,641	716
Real estate | Commercial real estate construction and land development
With no related allowance recorded:
Recorded investment with no related allowance recorded	1,326	209
Unpaid principal balance with no related allowance recorded	1,326	209
With an allowance recorded:
Impaired financing receivable, with related allowance, recorded investment	3,114	0
Impaired financing receivable, with related allowance, unpaid principal balance	3,114	0
Related Allowance	190	0
Total:
Recorded Investment	4,440	209
Unpaid Principal Balance	4,440	209
Related Allowance	190	0
Real estate | 1-4 family residential (including home equity)
With no related allowance recorded:
Recorded investment with no related allowance recorded	2,742	948
Unpaid principal balance with no related allowance recorded	2,741	948
With an allowance recorded:
Impaired financing receivable, with related allowance, recorded investment	0	0
Impaired financing receivable, with related allowance, unpaid principal balance	0	0
Related Allowance	0	0
Total:
Recorded Investment	2,742	948
Unpaid Principal Balance	2,741	948
Related Allowance	0	0
Real estate | Residential construction
With no related allowance recorded:
Recorded investment with no related allowance recorded	0	0
Unpaid principal balance with no related allowance recorded	0	0
With an allowance recorded:
Impaired financing receivable, with related allowance, recorded investment	0	0
Impaired financing receivable, with related allowance, unpaid principal balance	0	0
Related Allowance	0	0
Total:
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Consumer and other
With no related allowance recorded:
Recorded investment with no related allowance recorded	3	0
Unpaid principal balance with no related allowance recorded	3	0
With an allowance recorded:
Impaired financing receivable, with related allowance, recorded investment	0	0
Impaired financing receivable, with related allowance, unpaid principal balance	0	0
Related Allowance	0	0
Total:
Recorded Investment	3	0
Unpaid Principal Balance	3	0
Related Allowance	$ 0	$ 0

LOANS AND ALLOWANCE FOR LOAN_11

LOANS AND ALLOWANCE FOR LOAN LOSSES - Average Impaired Loans and Interest Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts Notes And Loans Receivable [Line Items]
Average Recorded Investment	$ 44,818	$ 34,059	$ 22,500
Interest Income Recognized	1,282	922	$ 862
Commercial and industrial
Accounts Notes And Loans Receivable [Line Items]
Average Recorded Investment	14,555	11,972
Interest Income Recognized	423	418
Mortgage warehouse
Accounts Notes And Loans Receivable [Line Items]
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Real estate | Commercial real estate (including multi-family residential)
Accounts Notes And Loans Receivable [Line Items]
Average Recorded Investment	23,198	20,606
Interest Income Recognized	756	475
Real estate | Commercial real estate construction and land development
Accounts Notes And Loans Receivable [Line Items]
Average Recorded Investment	4,247	314
Interest Income Recognized	98	10
Real estate | 1-4 family residential (including home equity)
Accounts Notes And Loans Receivable [Line Items]
Average Recorded Investment	2,815	1,167
Interest Income Recognized	0	18
Real estate | Residential construction
Accounts Notes And Loans Receivable [Line Items]
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Consumer and other
Accounts Notes And Loans Receivable [Line Items]
Average Recorded Investment	3	0
Interest Income Recognized	$ 5	$ 1

LOANS AND ALLOWANCE FOR LOAN_12

LOANS AND ALLOWANCE FOR LOAN LOSSES - Risk Category of Loans by Class (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	$ 3,708,306	$ 2,270,876
Pass
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	3,556,501	2,154,721
Watch
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	43,955	46,022
Special Mention
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	27,641	7,665
Substandard
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	80,209	62,468
Doubtful
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	0	0
Commercial and industrial
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	702,037	457,129
Commercial and industrial | Pass
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	656,783	427,336
Commercial and industrial | Watch
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	9,696	10,274
Commercial and industrial | Special Mention
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	13,874	2,195
Commercial and industrial | Substandard
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	21,684	17,324
Commercial and industrial | Doubtful
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	0	0
Mortgage warehouse
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	48,274	69,456
Mortgage warehouse | Pass
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	48,274	69,456
Mortgage warehouse | Watch
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	0	0
Mortgage warehouse | Special Mention
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	0	0
Mortgage warehouse | Substandard
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	0	0
Mortgage warehouse | Doubtful
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	0	0
Real estate | Commercial real estate (including multi-family residential)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	1,650,912	1,080,247
Real estate | Commercial real estate construction and land development
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	430,128	243,389
Real estate | 1-4 family residential (including home equity)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	649,311	301,219
Real estate | Residential construction
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	186,411	109,116
Real estate | Pass | Commercial real estate (including multi-family residential)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	1,570,243	1,016,831
Real estate | Pass | Commercial real estate construction and land development
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	424,460	231,536
Real estate | Pass | 1-4 family residential (including home equity)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	629,657	295,744
Real estate | Pass | Residential construction
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	186,411	103,611
Real estate | Watch | Commercial real estate (including multi-family residential)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	29,702	23,039
Real estate | Watch | Commercial real estate construction and land development
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	729	4,397
Real estate | Watch | 1-4 family residential (including home equity)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	3,797	2,696
Real estate | Watch | Residential construction
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	0	5,505
Real estate | Special Mention | Commercial real estate (including multi-family residential)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	7,101	4,685
Real estate | Special Mention | Commercial real estate construction and land development
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	2,149	0
Real estate | Special Mention | 1-4 family residential (including home equity)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	4,216	785
Real estate | Special Mention | Residential construction
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	0	0
Real estate | Substandard | Commercial real estate (including multi-family residential)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	43,866	35,692
Real estate | Substandard | Commercial real estate construction and land development
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	2,790	7,456
Real estate | Substandard | 1-4 family residential (including home equity)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	11,641	1,994
Real estate | Substandard | Residential construction
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	0	0
Real estate | Doubtful | Commercial real estate (including multi-family residential)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	0	0
Real estate | Doubtful | Commercial real estate construction and land development
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	0	0
Real estate | Doubtful | 1-4 family residential (including home equity)
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	0	0
Real estate | Doubtful | Residential construction
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	0	0
Consumer and other
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	41,233	10,320
Consumer and other | Pass
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	40,673	10,207
Consumer and other | Watch
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	31	111
Consumer and other | Special Mention
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	301	0
Consumer and other | Substandard
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	228	2
Consumer and other | Doubtful
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	$ 0	$ 0

LOANS AND ALLOWANCE FOR LOAN_13

LOANS AND ALLOWANCE FOR LOAN LOSSES - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017
Allowance for loan losses:
Balance, beginning of period	$ 23,649	$ 17,911	$ 13,098
Provision for loan losses	4,248	13,188	5,469
Charge-offs	(2,515)	(7,993)	(900)
Recoveries	949	543	244
Net charge-offs	(1,566)	(7,450)	(656)
Balance, end of period	26,331	23,649	17,911
Allowance for loan losses related to:
Individually evaluated for impairment				$ 6,729	$ 2,356
Collectively evaluated for impairment				19,602	21,293
Total allowance for loan losses	26,331	23,649	17,911	26,331	23,649
Recorded investment in loans:
Individually evaluated for impairment				43,553	32,713
Collectively evaluated for impairment				3,664,753	2,238,163
Total loans evaluated for impairment				3,708,306	2,270,876
Commercial and industrial
Allowance for loan losses:
Balance, beginning of period	7,694	5,059	3,644
Provision for loan losses	2,234	9,792	1,951
Charge-offs	(2,424)	(7,673)	(722)
Recoveries	847	516	186
Net charge-offs	(1,577)	(7,157)	(536)
Balance, end of period	8,351	7,694	5,059
Allowance for loan losses related to:
Individually evaluated for impairment				3,898	1,640
Collectively evaluated for impairment				4,453	6,054
Total allowance for loan losses	7,694	7,694	5,059	8,351	7,694
Recorded investment in loans:
Individually evaluated for impairment				13,504	11,392
Collectively evaluated for impairment				688,533	445,737
Total loans evaluated for impairment				702,037	457,129
Mortgage warehouse
Allowance for loan losses:
Balance, beginning of period	0	0	0
Provision for loan losses	0	0	0
Charge-offs	0	0	0
Recoveries	0	0	0
Net charge-offs	0	0	0
Balance, end of period	0	0	0
Allowance for loan losses related to:
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				0	0
Total allowance for loan losses	0	0	0	0	0
Recorded investment in loans:
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				48,274	69,456
Total loans evaluated for impairment				48,274	69,456
Commercial Real Estate Portfolio Segment | Commercial real estate (including multi-family residential)
Allowance for loan losses:
Balance, beginning of period	10,253	8,950	5,914
Provision for loan losses	1,588	1,424	3,122
Charge-offs	(42)	(124)	(129)
Recoveries	102	3	43
Net charge-offs	60	(121)	(86)
Balance, end of period	11,901	10,253	8,950
Allowance for loan losses related to:
Individually evaluated for impairment				2,641	716
Collectively evaluated for impairment				9,260	9,537
Total allowance for loan losses	10,253	10,253	8,950	11,901	10,253
Recorded investment in loans:
Individually evaluated for impairment				22,864	20,164
Collectively evaluated for impairment				1,628,048	1,060,083
Total loans evaluated for impairment				1,650,912	1,080,247
Commercial Real Estate Portfolio Segment | Commercial real estate construction and land development
Allowance for loan losses:
Balance, beginning of period	2,525	1,217	1,221
Provision for loan losses	199	1,298	(4)
Charge-offs	0	0	0
Recoveries	0	10	0
Net charge-offs	0	10	0
Balance, end of period	2,724	2,525	1,217
Allowance for loan losses related to:
Individually evaluated for impairment				190	0
Collectively evaluated for impairment				2,534	2,525
Total allowance for loan losses	2,525	2,525	1,217	2,724	2,525
Recorded investment in loans:
Individually evaluated for impairment				4,440	209
Collectively evaluated for impairment				425,688	243,180
Total loans evaluated for impairment				430,128	243,389
Commercial Real Estate Portfolio Segment | 1-4 family residential (including home equity)
Allowance for loan losses:
Balance, beginning of period	2,140	1,876	1,432
Provision for loan losses	127	254	434
Charge-offs	(25)	0	0
Recoveries	0	10	10
Net charge-offs	(25)	10	10
Balance, end of period	2,242	2,140	1,876
Allowance for loan losses related to:
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				2,242	2,140
Total allowance for loan losses	2,140	2,140	1,876	2,242	2,140
Recorded investment in loans:
Individually evaluated for impairment				2,742	948
Collectively evaluated for impairment				646,569	300,271
Total loans evaluated for impairment				649,311	301,219
Commercial Real Estate Portfolio Segment | Residential construction
Allowance for loan losses:
Balance, beginning of period	942	748	820
Provision for loan losses	98	194	(72)
Charge-offs	0	0	0
Recoveries	0	0	0
Net charge-offs	0	0	0
Balance, end of period	1,040	942	748
Allowance for loan losses related to:
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				1,040	942
Total allowance for loan losses	942	942	748	1,040	942
Recorded investment in loans:
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				186,411	109,116
Total loans evaluated for impairment				186,411	109,116
Consumer and other
Allowance for loan losses:
Balance, beginning of period	95	61	67
Provision for loan losses	2	226	38
Charge-offs	(24)	(196)	(49)
Recoveries	0	4	5
Net charge-offs	(24)	(192)	(44)
Balance, end of period	73	95	61
Allowance for loan losses related to:
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				73	95
Total allowance for loan losses	$ 95	$ 95	$ 61	73	95
Recorded investment in loans:
Individually evaluated for impairment				3	0
Collectively evaluated for impairment				41,230	10,320
Total loans evaluated for impairment				$ 41,233	$ 10,320

LOANS AND ALLOWANCE FOR LOAN_14

LOANS AND ALLOWANCE FOR LOAN LOSSES - Loans Modified in a Troubled Debt Restructuring (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)contract	Dec. 31, 2017USD ($)contract	Dec. 31, 2016USD ($)contract
Accounts Notes And Loans Receivable [Line Items]
Number of Contracts | contract	15	17	30
Pre- Modification of Outstanding Recorded Investment	$ 10,172	$ 14,532	$ 11,089
Post- Modification of Outstanding Recorded Investment	$ 10,172	$ 14,532	$ 11,089
Commercial and industrial
Accounts Notes And Loans Receivable [Line Items]
Number of Contracts | contract	11	9	21
Pre- Modification of Outstanding Recorded Investment	$ 2,770	$ 2,399	$ 3,939
Post- Modification of Outstanding Recorded Investment	$ 2,770	$ 2,399	$ 3,939
Mortgage warehouse
Accounts Notes And Loans Receivable [Line Items]
Number of Contracts | contract	0	0	0
Pre- Modification of Outstanding Recorded Investment	$ 0	$ 0	$ 0
Post- Modification of Outstanding Recorded Investment	$ 0	$ 0	$ 0
Real estate | Commercial real estate (including multi-family residential)
Accounts Notes And Loans Receivable [Line Items]
Number of Contracts | contract	3	6	8
Pre- Modification of Outstanding Recorded Investment	$ 4,288	$ 11,837	$ 7,144
Post- Modification of Outstanding Recorded Investment	$ 4,288	$ 11,837	$ 7,144
Real estate | Commercial real estate construction and land development
Accounts Notes And Loans Receivable [Line Items]
Number of Contracts | contract	1	1	0
Pre- Modification of Outstanding Recorded Investment	$ 3,114	$ 210	$ 0
Post- Modification of Outstanding Recorded Investment	$ 3,114	$ 210	$ 0
Real estate | 1-4 family residential (including home equity)
Accounts Notes And Loans Receivable [Line Items]
Number of Contracts | contract	0	1	0
Pre- Modification of Outstanding Recorded Investment	$ 0	$ 86	$ 0
Post- Modification of Outstanding Recorded Investment	$ 0	$ 86	$ 0
Real estate | Residential construction
Accounts Notes And Loans Receivable [Line Items]
Number of Contracts | contract	0	0	0
Pre- Modification of Outstanding Recorded Investment	$ 0	$ 0	$ 0
Post- Modification of Outstanding Recorded Investment	$ 0	$ 0	$ 0
Consumer and other
Accounts Notes And Loans Receivable [Line Items]
Number of Contracts | contract	0	0	1
Pre- Modification of Outstanding Recorded Investment	$ 0	$ 0	$ 6
Post- Modification of Outstanding Recorded Investment	$ 0	$ 0	$ 6

FAIR VALUE - Carrying Amounts a

FAIR VALUE - Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	$ 337,293	$ 309,615
FHLB stock	10,941	12,862
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	268,947	182,103
Available for sale securities	337,293	309,615
Loans held for investment, net of allowance	3,681,975	2,247,227
FHLB stock	10,941	12,862
Accrued interest receivable	17,010	12,194
Deposits	3,662,536	2,213,974
Accrued interest payable	2,812	610
Borrowed funds	225,493	282,569
Subordinated debt	48,899	48,659
Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	268,947	182,103
Available for sale securities	337,293	309,615
Loans held for investment, net of allowance	3,674,241	2,238,721
Accrued interest receivable	17,010	12,194
Deposits	3,653,244	2,209,111
Accrued interest payable	2,812	610
Borrowed funds	230,445	288,887
Subordinated debt	49,663	48,659
Estimated Fair Value | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	268,947	182,103
Available for sale securities	0	0
Loans held for investment, net of allowance	0	0
Accrued interest receivable	65	3
Deposits	0	0
Accrued interest payable	0	0
Borrowed funds	0	0
Subordinated debt	0	0
Estimated Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Available for sale securities	337,293	309,615
Loans held for investment, net of allowance	0	0
Accrued interest receivable	3,498	3,296
Deposits	3,653,244	2,209,111
Accrued interest payable	2,812	610
Borrowed funds	230,445	288,887
Subordinated debt	49,663	48,659
Estimated Fair Value | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Available for sale securities	0	0
Loans held for investment, net of allowance	3,674,241	2,238,721
Accrued interest receivable	13,447	8,895
Deposits	0	0
Accrued interest payable	0	0
Borrowed funds	0	0
Subordinated debt	$ 0	$ 0

FAIR VALUE - Fair Values for As

FAIR VALUE - Fair Values for Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	$ 337,293	$ 309,615
U.S. Government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	8,685	8,715
Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	216,785	222,958
Agency mortgage-backed pass-through securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	66,195	31,812
Corporate bonds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	45,628	46,130
Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	337,293	309,615
Recurring Basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring Basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	337,293	309,615
Recurring Basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring Basis | U.S. Government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	8,685	8,715
Recurring Basis | U.S. Government and agency securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring Basis | U.S. Government and agency securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	8,685	8,715
Recurring Basis | U.S. Government and agency securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring Basis | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	216,785	222,958
Recurring Basis | Municipal securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring Basis | Municipal securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	216,785	222,958
Recurring Basis | Municipal securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring Basis | Agency mortgage-backed pass-through securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	66,195	31,812
Recurring Basis | Agency mortgage-backed pass-through securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring Basis | Agency mortgage-backed pass-through securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	66,195	31,812
Recurring Basis | Agency mortgage-backed pass-through securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring Basis | Corporate bonds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	45,628	46,130
Recurring Basis | Corporate bonds and other | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	0	0
Recurring Basis | Corporate bonds and other | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	45,628	46,130
Recurring Basis | Corporate bonds and other | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	$ 0	$ 0

FAIR VALUE - Narrative (Details

FAIR VALUE - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired financing receivable, with related allowance, recorded investment	$ 23,806,000	$ 13,609,000
Impaired financing receivable, with related allowance, unpaid principal balance	24,201,000	13,846,000
Related allowance	6,729,000	2,356,000
Real estate acquired through foreclosure	630,000	365,000
Loans receivable, real estate		365,000
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired financing receivable, with related allowance, recorded investment	17,500,000	11,500,000
Impaired financing receivable, with related allowance, unpaid principal balance	24,200,000	13,800,000
Related allowance	6,700,000	2,400,000
Real estate acquired through foreclosure	$ 630,000
Impaired Loans with Specific Allocation of Allowance | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of estimated selling and closing costs of collateral	5.00%
Impaired Loans with Specific Allocation of Allowance | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of estimated selling and closing costs of collateral	10.00%
Other Real Estate Owned | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of estimated selling and closing costs of collateral	5.00%
Other Real Estate Owned | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of estimated selling and closing costs of collateral	10.00%
Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, fair value disclosure, recurring	$ 0	$ 0

FAIR VALUE - Assets and Liabili

FAIR VALUE - Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details) - Nonrecurring Basis - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	$ 0	$ 0
Assets and liabilities are measured at fair value, nonrecurring basis	0	0
Level 1 | Commercial real estate construction and land development
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans:	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	0	0
Assets and liabilities are measured at fair value, nonrecurring basis	0	0
Level 2 | Commercial real estate construction and land development
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans:	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	630	365
Assets and liabilities are measured at fair value, nonrecurring basis	18,102	11,855
Level 3 | Commercial real estate construction and land development
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans:	2,924
Commercial and industrial | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans:	0	0
Commercial and industrial | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans:	0	0
Commercial and industrial | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans:	5,647	4,012
Commercial real estate (including multi-family residential) | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans:	0	0
Commercial real estate (including multi-family residential) | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans:	0	0
Commercial real estate (including multi-family residential) | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans:	$ 8,901	$ 7,478

PREMISES AND EQUIPMENT - Premis

PREMISES AND EQUIPMENT - Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 52,670	$ 27,699
Less: accumulated depreciation	10,953	9,222
Premises and equipment, net	41,717	18,477
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	11,586	5,376
Buildings
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	23,455	7,977
Leasehold improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	5,291	5,059
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	11,858	8,967
Construction in progress
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 480	$ 320

PREMISES AND EQUIPMENT - Narrat

PREMISES AND EQUIPMENT - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Depreciation	$ 2.1	$ 1.6	$ 1.6

DEPOSITS - Narrative (Details)

DEPOSITS - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deposit Liabilities [Abstract]
Time deposits, at or above FDIC insurance limit	$ 250
Time deposits 250,000 or more	509,300	$ 227,400
Brokered deposits	261,100	314,800
Reciprocal deposits		68,400
Related party deposit liabilities	$ 9,600	$ 14,800

DEPOSITS - Time Deposits by Mat

DEPOSITS - Time Deposits by Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deposit Liabilities [Abstract]
Within one year	$ 793,284
After one but within two years	161,877
After two but within three years	89,942
After three but within four years	92,790
After four but within five years	68,598
Total	$ 1,206,491	$ 761,314

BORROWINGS AND BORROWING CAPA_3

BORROWINGS AND BORROWING CAPACITY - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 28, 2018
Amended Revolving Credit Agreement
Debt Instrument [Line Items]
Debt instrument maturity, month and year	2025-12
Percentage of debt secured by capital stock	100.00%
Borrowing Agreement | Prime Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.25%
Interest rate, effective percentage	5.00%
Credit Facility With Another Financial Institution | Amended Revolving Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 45,000,000
Annual reduction in borrowing capacity		$ 7,500,000
Federal Home Loan Bank of Dallas
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 1,060,000,000
Remaining borrowing capacity	765,400,000
Outstanding amount	296,500,000
Letters of credit, outstanding amount	71,500,000
Federal Home Loan Bank of Dallas | Expire in January 2019
Debt Instrument [Line Items]
Letters of credit, outstanding amount	8,800,000
Federal Home Loan Bank of Dallas | Expire in February 2019
Debt Instrument [Line Items]
Letters of credit, outstanding amount	10,200,000
Federal Home Loan Bank of Dallas | Expire in April 2019
Debt Instrument [Line Items]
Letters of credit, outstanding amount	7,100,000
Federal Home Loan Bank of Dallas | Expire in May 2019
Debt Instrument [Line Items]
Letters of credit, outstanding amount	7,100,000
Federal Home Loan Bank of Dallas | Expire in August 2019
Debt Instrument [Line Items]
Letters of credit, outstanding amount	5,500,000
Federal Home Loan Bank of Dallas | Expire in October 2019
Debt Instrument [Line Items]
Letters of credit, outstanding amount	25,000,000
Federal Home Loan Bank of Dallas | Expire in December 2019
Debt Instrument [Line Items]
Letters of credit, outstanding amount	6,300,000
Federal Home Loan Bank of Dallas | Expire in January 2020
Debt Instrument [Line Items]
Letters of credit, outstanding amount	1,500,000
Federal Home Loan Bank of Dallas | Short-term Debt
Debt Instrument [Line Items]
Federal Home Loan Bank, advances	$ 225,000,000
Federal Home Loan Bank of Dallas | Short-term Debt | Weighted Average
Debt Instrument [Line Items]
Federal Home Loan Bank, advances, interest rate	2.57%

BORROWINGS AND BORROWING CAPA_4

BORROWINGS AND BORROWING CAPACITY - Scheduled Principal Maturities (Details) $ in Thousands	Dec. 31, 2018USD ($)
Debt Disclosure [Abstract]
2019	$ 0
2020	0
2021	0
2022	0
2023 and thereafter	569
Total	$ 569

SUBORDINATED DEBT - Narrative (

SUBORDINATED DEBT - Narrative (Details) - USD ($)	1 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Jan. 01, 2015
Subordinated Borrowing [Line Items]
Debentures, period over which company may defer interest payments		5 years
Junior Subordinated Debt | Subordinated Notes Issued 2017
Subordinated Borrowing [Line Items]
Debt instrument, face amount	$ 40,000,000
Issuance price, percentage	100.00%
Proceeds from issuance of debt	$ 39,400,000
Stated percentage	5.25%
Redemption price, percentage	100.00%
Junior Subordinated Debt | Subordinated Notes Issued 2017 | 3 month LIBOR
Subordinated Borrowing [Line Items]
Basis spread on variable rate	3.03%
F&M Bancshares. Inc. | Junior Subordinated Debt
Subordinated Borrowing [Line Items]
Debt instrument, face amount		$ 11,300,000
Borrowed funds		$ 9,400,000
Debt instrument, unamortized discount			$ 2,500,000

SUBORDINATED DEBT - Summary of

SUBORDINATED DEBT - Summary of Pertinent Information Related to Junior Subordinated Debentures (Details)	12 Months Ended
	Dec. 31, 2018USD ($)
Subordinated Borrowing [Line Items]
Junior Subordinated Debt Owed to Trusts	$ 11,341,000
Junior Subordinated Debt | 3 month LIBOR
Subordinated Borrowing [Line Items]
Interest rate, period end	2.7902%
Junior Subordinated Debt | Farmers & Merchants Capital Trust II
Subordinated Borrowing [Line Items]
Issuance Date	Nov. 13, 2003
Trust Preferred Securities Outstanding	$ 7,500,000
Junior Subordinated Debt Owed to Trusts	$ 7,732,000
Maturity Date	Nov. 8, 2033
Junior Subordinated Debt | Farmers & Merchants Capital Trust II | 3 month LIBOR
Subordinated Borrowing [Line Items]
Basis spread on variable rate	3.00%
Junior Subordinated Debt | Farmers & Merchants Capital Trust III
Subordinated Borrowing [Line Items]
Issuance Date	Jun. 30, 2005
Trust Preferred Securities Outstanding	$ 3,500,000
Junior Subordinated Debt Owed to Trusts	$ 3,609,000
Maturity Date	Jul. 7, 2035
Junior Subordinated Debt | Farmers & Merchants Capital Trust III | 3 month LIBOR
Subordinated Borrowing [Line Items]
Basis spread on variable rate	1.80%

INCOME TAXES - Components of th

INCOME TAXES - Components of the Provision for Federal Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Current	$ 8,204	$ 8,320	$ 11,162
Deferred	(256)	427	(1,608)
Total	$ 7,948	$ 8,747	$ 9,554

INCOME TAXES - Effective Income

INCOME TAXES - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Taxes calculated at statutory rate	$ 9,504	$ 9,233	$ 11,342
Increase (decrease) resulting from:
Stock based compensation	(400)	(755)	67
Effect of tax exempt income	(1,284)	(2,328)	(1,929)
Provisional deferred tax adjustment related to reduction in U.S. federal statutory income tax rate		2,621
Other, net	128	(24)	74
Total	$ 7,948	$ 8,747	$ 9,554

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
U.S. federal statutory income tax rate	21.00%	35.00%
Tax Cuts and Jobs Act of 2017, income tax expense		$ 2,600,000
Net benefit, share-based compensation	$ 587,000	1,100,000
Unrecognized tax benefits, income tax penalties and interest expense	$ 0	$ 0	$ 0

INCOME TAXES - Deferred Tax Ass

INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Allowance for credit losses	$ 5,898	$ 5,284
Net unrealized loss on available for sale securities	761
Deferred compensation	366	177
Total deferred tax assets	7,025	5,461
Deferred tax liabilities:
Core deposit intangible and other purchase accounting adjustments	(2,718)	(1,100)
Net unrealized gain on available for sale securities		(65)
Premises and equipment basis difference	(2,035)	(321)
Total deferred tax liabilities	(4,753)	(1,486)
Net deferred tax assets	$ 2,272	$ 3,975

STOCK BASED COMPENSATION - Narr

STOCK BASED COMPENSATION - Narrative (Details) $ / shares in Units, $ in Thousands	Oct. 01, 2018$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)			1,900,000
Share-based compensation expense | $		$ 1,700	$ 1,800	$ 1,500
Options exercised (in dollars per share) | $ / shares		$ 13.88	$ 17.50
Post Oak Bancshares, Inc.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares per common share or option to purchase common shares	0.7017
Options exercised (in dollars per share) | $ / shares	$ 12.83
Option issued in acquisition to purchase common shares	299,352
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option, cumulative options granted since inception (in shares)		1,309,231
Expiration period		10 years
Award vesting period		4 years
Unrecognized compensation cost | $		$ 950
Weighted average period over which unrecognized compensation		1 year 4 months 28 days
Employee Stock Option | Post Oak Bancshares, Inc.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares per common share or option to purchase common shares	0.7017
Options exercised (in dollars per share) | $ / shares	$ 12.83
Option issued in acquisition to purchase common shares	299,352
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost | $		$ 4,800
Weighted average period over which unrecognized compensation		3 years 7 months 2 days
Share awards granted (in shares)		122,000	28,000
Share awards granted (in dollars per share) | $ / shares		$ 39.04	$ 36.17
Restricted Stock | Share Award Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option, cumulative options granted since inception (in shares)		226,529
Award vesting period		4 years
Share awards granted (in shares)		122,127	28,106	15,401
Share awards granted (in dollars per share) | $ / shares		$ 39.04	$ 36.17	$ 17.52
Award vested in period, fair value | $		$ 621	$ 203	$ 172

STOCK BASED COMPENSATION - Summ

STOCK BASED COMPENSATION - Summary of Stock Option Valuation Assumptions (Details) - Stock Option Plan	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.72%	2.40%	1.76%
Expected term	10 years	10 years	10 years
Expected stock price volatility	29.26%	29.70%	34.60%
Dividend yield	0.00%	0.00%	0.00%

STOCK BASED COMPENSATION - Stoc

STOCK BASED COMPENSATION - Stock Option Plans Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Options
Options outstanding, beginning balance (in shares)	775	935
Options granted (in shares)	4	64
Options assumed (in shares)	299
Options exercised (in shares)	(244)	(215)
Options forfeited (in shares)	(32)	(9)
Options outstanding, ending balance (in shares)	802	775	935
Number of options vested and exercisable (in shares)	677
Weighted Average Exercise Price
Options outstanding, beginning balance (in dollars per share)	$ 19.94	$ 18.21
Options granted (in dollars per share)	40.40	36.88
Options assumed (in dollars per share)	12.83
Options exercised (in dollars per share)	13.88	17.50
Options forfeited (in dollars per share)	29.53	23.35
Options outstanding, ending balance (in dollars per share)	18.88	$ 19.94	$ 18.21
Weighted Average Exercise Price, Options vested and exercisable (in dollars per share)	$ 17.32
Weighted Average Remaining Contractual Term, Options outstanding	4 years 7 months 9 days	5 years 8 months 19 days	6 years 2 months 23 days
Weighted Average Remaining Contractual Term, Options vested and exercisable	4 years 1 month 2 days
Aggregate Intrinsic Value, Options outstanding	$ 10,830	$ 13,718	$ 16,773
Aggregate Intrinsic Value, Options vested and exercisable	$ 10,193

STOCK BASED COMPENSATION - Info

STOCK BASED COMPENSATION - Information Related To The Stock Option Plan (Details) - Stock Option Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised	$ 3,254	$ 3,371	$ 1,128
Cash received from option exercises	$ 3,393	$ 3,743	$ 1,782
Weighted average fair value of options granted	$ 18	$ 16.55	$ 10.51

STOCK BASED COMPENSATION - Su_2

STOCK BASED COMPENSATION - Summary of Restricted Stock Activity (Details) - Restricted Stock - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Nonvested share awards outstanding, beginning balance (in shares)	41	24
Share awards granted (in shares)	122	28
Share awards vested (in shares)	(20)	(11)
Unvested share awards forfeited or cancelled (in shares)	0	0
Nonvested share awards outstanding, ending balance (in shares)	143	41
Weighted Average Grant Date Fair Value
Nonvested share awards outstanding, beginning balance (in dollars per share)	$ 30.46	$ 18.31
Share awards granted (in dollars per share)	39.04	36.17
Share awards vested (in dollars per share)	30.12	18.32
Unvested share awards forfeited or cancelled (in dollars per share)	0	0
Nonvested share awards outstanding, ending balance	$ 37.48	$ 30.46

OTHER EMPLOYEE BENEFITS (Detail

OTHER EMPLOYEE BENEFITS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Plan Disclosure [Line Items]
Share-based compensation expense	$ 1,700	$ 1,800	$ 1,500
401 (k) Benefit Plan
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percent of match	50.00%
Employer matching contribution, percent of employee's gross pay	6.00%
Maximum annual contributions per employee, percent	3.00%
Employer contribution amount	$ 962	789	637
Profit Sharing Plan
Defined Contribution Plan Disclosure [Line Items]
Employer contribution amount	$ 2,500	1,500	1,700
Employee Stock Purchase Plan
Defined Contribution Plan Disclosure [Line Items]
Employee purchase price for share as percent of discount to market value	15.00%
Share-based compensation expense	$ 48	$ 144	$ 90

OFF-BALANCE SHEET ARRANGEMENT_3

OFF-BALANCE SHEET ARRANGEMENTS, COMMITMENTS AND CONTINGENCIES - Contractual Amounts of Financial Instruments With Off-balance Sheet Risk (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed Rate	$ 485,657	$ 385,018
Variable Rate	539,613	252,192
Commitments to extend credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed Rate	471,440	369,573
Variable Rate	530,546	250,467
Standby letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed Rate	14,217	15,445
Variable Rate	$ 9,067	$ 1,725

OFF-BALANCE SHEET ARRANGEMENT_4

OFF-BALANCE SHEET ARRANGEMENTS, COMMITMENTS AND CONTINGENCIES - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Commitments to make loans, period	120 days
Off-balance-sheet fixed rate loan commitments, weighted average maturity	2 years 5 months 26 days
Rent Expense	$ 2.9	$ 2.8	$ 2.7
Minimum
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance-sheet fixed rate loan commitments, interest rate	1.95%
Maximum
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance-sheet fixed rate loan commitments, interest rate	8.70%
Weighted Average
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance-sheet fixed rate loan commitments, interest rate	5.26%

OFF-BALANCE SHEET ARRANGEMENT_5

OFF-BALANCE SHEET ARRANGEMENTS, COMMITMENTS AND CONTINGENCIES - Summary of Non-cancelable Future Operating Lease Commitments (Details) $ in Thousands	Dec. 31, 2018USD ($)
Off Balance Sheet Arrangements Commitments And Contingencies Disclosure [Abstract]
2019	$ 2,559
2020	1,987
2021	1,731
2022	1,510
2023	1,042
Thereafter	4,083
Operating Leases, Future Minimum Payments Due	$ 12,912

REGULATORY CAPITAL MATTERS - Ac

REGULATORY CAPITAL MATTERS - Actual and Required Capital (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Total Capital
Capital	$ 531,453	$ 336,829
Capital to Risk Weighted Assets	13.70%	13.43%
Capital Required for Capital Adequacy	$ 310,295	$ 200,687
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	8.00%
Plus Capital Conservation Buffer	$ 383,020	$ 232,044
Plus Capital Conservation Buffer to Risk Weighted Assets	9.875%	9.25%
Common Equity Tier 1 Capital
Common Equity Tier 1 Risk Based Capital	$ 456,223	$ 264,521
Common Equity Tier 1 Risk Based Capital to Risk Weighted Assets	11.76%	10.54%
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy	$ 174,541	$ 112,886
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Plus Common Equity Tier 1 Risk Based Capital	$ 247,266	$ 144,244
Plus Common Equity Tier 1 Risk Based Capital to Risk Weighted Assets	6.375%	5.75%
Tier 1 Capital
Tier 1 Risk Based Capital	$ 465,637	$ 273,825
Tier 1 Risk Based Capital to Risk Weighted Assets	12.01%	10.92%
Tier 1 Risk Based Capital Required for Capital Adequacy	$ 232,721	$ 150,515
Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	6.00%	6.00%
Plus Tier 1 Risk Based Capital	$ 305,446	$ 181,872
Plus Tier 1 Risk Based Capital to Risk Weighted Assets	7.875%	7.25%
Tier 1 Capital
Tier 1 Leverage Capital	$ 465,637	$ 273,825
Tier 1 Leverage Capital to Average Assets	10.61%	9.84%
Tier 1 Leverage Capital Required for Capital Adequacy	$ 175,621	$ 111,274
Tier 1 Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Plus Tier 1 Leverage Capital	$ 175,621	$ 111,274
Plus Tier 1 Leverage Capital to Average Assets	4.00%	4.00%
Allegiance Bank
Total Capital
Capital	$ 524,660	$ 331,872
Capital to Risk Weighted Assets	13.53%	13.24%
Capital Required for Capital Adequacy	$ 310,179	$ 200,596
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	8.00%
Plus Capital Conservation Buffer	$ 382,877	$ 231,939
Plus Capital Conservation Buffer to Risk Weighted Assets	9.875%	9.25%
Capital Required to be Well Capitalized	$ 387,724	$ 250,745
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%	10.00%
Common Equity Tier 1 Capital
Common Equity Tier 1 Risk Based Capital	$ 458,844	$ 268,868
Common Equity Tier 1 Risk Based Capital to Risk Weighted Assets	11.83%	10.72%
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy	$ 174,476	$ 112,835
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Plus Common Equity Tier 1 Risk Based Capital	$ 247,174	$ 144,179
Plus Common Equity Tier 1 Risk Based Capital to Risk Weighted Assets	6.375%	5.75%
Common Equity Tier 1 Risk Based Capital Required to be Well Capitalized	$ 252,021	$ 162,985
Common Equity Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Tier 1 Capital
Tier 1 Risk Based Capital	$ 458,844	$ 268,868
Tier 1 Risk Based Capital to Risk Weighted Assets	11.83%	10.72%
Tier 1 Risk Based Capital Required for Capital Adequacy	$ 232,634	$ 150,447
Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	6.00%	6.00%
Plus Tier 1 Risk Based Capital	$ 305,333	$ 181,790
Plus Tier 1 Risk Based Capital to Risk Weighted Assets	7.875%	7.25%
Tier 1 Risk Based Capital Required to be Well Capitalized	$ 310,179	$ 200,596
Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	8.00%
Tier 1 Capital
Tier 1 Leverage Capital	$ 458,844	$ 268,868
Tier 1 Leverage Capital to Average Assets	10.45%	9.67%
Tier 1 Leverage Capital Required for Capital Adequacy	$ 175,552	$ 111,230
Tier 1 Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Plus Tier 1 Leverage Capital	$ 175,552	$ 111,230
Plus Tier 1 Leverage Capital to Average Assets	4.00%	4.00%
Tier 1 Leverage Capital Required to be Well Capitalized	$ 219,440	$ 139,037
Tier 1 Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%

EARNINGS PER COMMON SHARE - Sum

EARNINGS PER COMMON SHARE - Summary of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Net income attributable to shareholders									$ 37,309	$ 17,632	$ 22,851
Basic:
Weighted average shares outstanding (in shares)									15,485	13,125	12,873
Weighted average common shares outstanding (in dollars per share)	$ 0.60	$ 0.66	$ 0.57	$ 0.58	$ 0.24	$ 0.23	$ 0.41	$ 0.46	$ 2.41	$ 1.34	$ 1.78
Add incremental shares for:
Dilutive effect of stock option exercises (in shares)									288	333	201
Total (in shares)									15,773	13,458	13,074
Total (in dollars per share)	$ 0.59	$ 0.65	$ 0.55	$ 0.57	$ 0.24	$ 0.22	$ 0.40	$ 0.45	$ 2.37	$ 1.31	$ 1.75

EARNINGS PER COMMON SHARE - Nar

EARNINGS PER COMMON SHARE - Narrative (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Employee Stock Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	69	28

PARENT COMPANY ONLY FINANCIAL_3

PARENT COMPANY ONLY FINANCIAL STATEMENTS - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
ASSETS
Cash and due from banks	$ 118,771	$ 133,124
Other assets	20,544	12,303
TOTAL ASSETS	4,655,249	2,860,231
LIABILITIES:
Borrowed funds	225,493	282,569
Subordinated debt	48,899	48,659
Total liabilities	3,952,265	2,553,366
SHAREHOLDERS’ EQUITY:
Common stock	21,938	13,227
Capital surplus	571,803	218,408
Retained earnings	112,131	74,894
Accumulated other comprehensive (loss) income	(2,888)	336
Total shareholders’ equity	702,984	306,865	$ 279,817	$ 258,490
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	4,655,249	2,860,231
Parent Company
ASSETS
Cash and due from banks	6,780	4,857
Investment in subsidiary	705,947	311,553
Other assets	1,026	791
TOTAL ASSETS	713,753	317,201
LIABILITIES:
Borrowed funds	492	569
Subordinated debt	9,414	9,304
Accrued interest payable and other liabilities	862	463
Total liabilities	10,768	10,336
SHAREHOLDERS’ EQUITY:
Common stock	21,938	13,227
Capital surplus	571,804	218,408
Retained earnings	112,131	74,894
Accumulated other comprehensive (loss) income	(2,888)	336
Total shareholders’ equity	702,985	306,865
TOTAL LIABILITIES AND SHAREHOLDERS’ EQUITY	$ 713,753	$ 317,201

PARENT COMPANY ONLY FINANCIAL_4

PARENT COMPANY ONLY FINANCIAL STATEMENTS - Condensed Statements of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
OPERATING EXPENSE:
Interest expense on borrowed funds	$ 29,644	$ 15,770	$ 10,914
INCOME TAX BENEFIT	(7,948)	(8,747)	(9,554)
INCOME BEFORE EQUITY IN UNDISTRIBUTED
NET INCOME	37,309	17,632	22,851
Parent Company
OPERATING INCOME:
Other income	16	13	11
Total income	16	13	11
OPERATING EXPENSE:
Interest expense on borrowed funds	38	33	30
Other expenses	1,692	1,465	1,204
Total operating expense	1,730	1,498	1,234
INCOME BEFORE INCOME TAX BENEFIT AND EQUITY IN UNDISTRIBUTED EARNINGS OF SUBSIDIARIES	(1,714)	(1,485)	(1,223)
INCOME TAX BENEFIT	360	756	428
INCOME BEFORE EQUITY IN UNDISTRIBUTED
EARNINGS OF SUBSIDIARIES	(1,354)	(729)	(795)
EQUITY IN UNDISTRIBUTED EARNINGS OF SUBSIDIARIES	38,663	18,361	23,646
NET INCOME	$ 37,309	$ 17,632	$ 22,851

PARENT COMPANY ONLY FINANCIAL_5

PARENT COMPANY ONLY FINANCIAL STATEMENTS - Condensed Cash Flow Statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 37,309	$ 17,632	$ 22,851
Adjustments to reconcile net income to net cash provided by operating activities:
Net amortization of discount on subordinated debt	110	108	107
Increase (decrease) in accrued interest payable and other liabilities	1,822	3,136	(851)
Net cash provided by operating activities	46,059	33,432	27,435
CASH FLOWS FROM INVESTING ACTIVITIES:
Net cash used in investing activities	(31,155)	(377,824)	(408,494)
CASH FLOWS FROM FINANCING ACTIVITIES:
Stock based compensation expense	3,750	4,248	2,006
(Repurchase) issuance of treasury stock	(2,112)		38
Net cash provided by financing activities	71,940	384,397	374,726
NET CHANGE IN CASH AND CASH EQUIVALENTS	86,844	40,005	(6,333)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	182,103	142,098	148,431
CASH AND CASH EQUIVALENTS, END OF PERIOD	268,947	182,103	142,098
Parent Company
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	37,309	17,632	22,851
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of subsidiaries	(38,663)	(18,361)	(23,646)
Net amortization of discount on subordinated debt	110	107	107
Increase in other assets	(236)	(378)	(399)
Increase (decrease) in accrued interest payable and other liabilities	279	(377)	186
Net cash provided by operating activities	(1,201)	(1,377)	(901)
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital investment in bank subsidiary		(21,000)
Net cash used in investing activities		(21,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock	3,552	4,248	2,006
Stock based compensation expense	1,685	1,780	1,501
(Repurchase) issuance of treasury stock	(2,113)		38
Net cash provided by financing activities	3,124	6,028	3,545
NET CHANGE IN CASH AND CASH EQUIVALENTS	1,923	(16,349)	2,644
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	4,857	21,206	18,562
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 6,780	$ 4,857	$ 21,206

QUARTERLY FINANCIAL DATA (UNA_3

QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Interest Income	$ 56,303	$ 35,336	$ 34,193	$ 32,391	$ 32,038	$ 30,901	$ 28,987	$ 27,512	$ 158,223	$ 119,438	$ 100,778
Net Interest Income	45,838	28,036	27,816	26,889	27,436	26,997	25,107	24,128	128,579	103,668	89,864
Net Income Attributable to Common Shareholders	$ 13,163	$ 8,879	$ 7,556	$ 7,711	$ 3,204	$ 2,986	$ 5,395	$ 6,047	$ 37,309	$ 17,632	$ 22,851
Earnings Per Share, Basic (in dollars per share)	$ 0.60	$ 0.66	$ 0.57	$ 0.58	$ 0.24	$ 0.23	$ 0.41	$ 0.46	$ 2.41	$ 1.34	$ 1.78
Earnings Per Share, Diluted (in dollars per share)	$ 0.59	$ 0.65	$ 0.55	$ 0.57	$ 0.24	$ 0.22	$ 0.40	$ 0.45	$ 2.37	$ 1.31	$ 1.75

SUBSEQUENT EVENT - Narrative (D

SUBSEQUENT EVENT - Narrative (Details) - Lowery Bank - Subsequent Event $ in Millions	Feb. 01, 2019USD ($)
Subsequent Event [Line Items]
Effective date of acqusition	Feb. 1, 2019
Business acquisition, customer deposits balances	$ 15
Business acquisition, loans	$ 44