DISCLOSURES ABOUT FAIR VALUE OF FINANCIAL INSTRUMENTS - Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financial Assets:
Available-for-sale securities, at fair value	$ 705,539	$ 274,619
Held-to-maturity securities	13,146	34,844
Loans held for sale	7,156	23,989
Loans held for investment	3,190,485	3,098,220
Real estate acquired by foreclosure	802	5,220
Level 1
Financial Assets:
Cash and short term investments	140,681	389,007
Available-for-sale securities, at fair value		112,881
Other securities	26,617	17,983
Loans held for sale		24,144
Total	167,298	544,015
Level 2
Financial Assets:
Available-for-sale securities, at fair value	705,539	161,738
Held-to-maturity securities	13,146	34,845
Loans held for sale	7,156
Total	725,841	196,583
Financial Liabilities:
Deposits	3,392,144	3,375,047
Securities sold under agreements to repurchase	5,173	3,493
Other borrowed funds	324,873	148,921
Subordinated debentures	45,356	47,492
Total	3,767,546	3,574,953
Level 3
Financial Assets:
Loans held for investment	3,206,145	3,128,966
Real estate acquired by foreclosure	802	5,220
Total	3,206,947	3,134,186
Carrying Value
Financial Assets:
Cash and short term investments	140,681	389,007
Available-for-sale securities, at fair value	705,539	274,619
Held-to-maturity securities	13,275	35,505
Other securities	26,617	17,983
Loans held for sale	7,156	23,989
Loans held for investment	3,190,485	3,098,220
Real estate acquired by foreclosure	802	5,220
Total	4,084,555	3,844,543
Financial Liabilities:
Deposits	3,397,143	3,374,700
Securities sold under agreements to repurchase	5,173	3,493
Other borrowed funds	325,000	150,000
Subordinated debentures	47,737	47,492
Total	3,775,053	3,575,685
Fair Value
Financial Assets:
Cash and short term investments	140,681	389,007
Available-for-sale securities, at fair value	705,539	274,619
Held-to-maturity securities	13,146	34,845
Other securities	26,617	17,983
Loans held for sale	7,156	24,144
Loans held for investment	3,206,145	3,128,966
Real estate acquired by foreclosure	802	5,220
Total	4,100,086	3,874,784
Financial Liabilities:
Deposits	3,392,144	3,375,047
Securities sold under agreements to repurchase	5,173	3,493
Other borrowed funds	324,873	148,921
Subordinated debentures	45,356	47,492
Total	$ 3,767,546	$ 3,574,953

Fair value portion of subordinated debentures.

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value portion of investments accounted under the cost method.

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

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Fair value of investments in debt securities classified as held-to-maturity.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

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Fair value portion of securities that an entity sells and agrees to repurchase at a specified date for a specified price.

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