BASIS OF PRESENTATION, NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING AND REPORTING POLICIES (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017 USD ($) location segment item $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Number of locations | location		33
Number of reportable segment | segment		1
Reserve required at federal reserve bank		$ 15,800,000	$ 16,100,000
Cash deposits in excess of the amount insured by the FDIC		91,800,000	79,200,000
FHLB stock		$ 1,200,000	1,200,000
FRB stock, par value | $ / shares		$ 100
FRB stock, par value - Member's Bank | $ / shares		$ 50
Federal Reserve Bank stock		$ 9,300,000	9,300,000
The Independent Bankers Financial Corporation stock		$ 141,000	141,000
Number of private investment funds under the Small Business Investment Company (SBIC) program | item		2
Private investment funds		$ 1,600,000	1,500,000
Unfunded commitments		$ 3,800,000	$ 4,000,000
Treasury stock repurchased (in shares) | shares		0	635,100	246,708
Treasury stock repurchased (in dollars per share) | $ / shares			$ 17.56	$ 17.60
Statutory rate (as a percent)		35.00%	35.00%	35.00%
Contractual maturities		10 years
Cash flow information:
Cash paid for taxes		$ 13,752,000	$ 11,390,000	$ 11,050,000
Dividends accrued for restricted stock		11,000
Real estate acquired through foreclosure		$ 881,000	2,671,000	823,000
Forecast
Statutory rate (as a percent)	21.00%
Customer relationships
Amortization period		15 years
Minimum
Amortization period		7 years
Minimum | Core deposits
Amortization period		7 years
Maximum
Amortization period		20 years
Maximum | Core deposits
Amortization period		10 years
Buildings
Useful life (in years)		32 years
Furniture and equipment | Minimum
Useful life (in years)		3 years
Furniture and equipment | Maximum
Useful life (in years)		10 years
Vehicles
Useful life (in years)		3 years
Notes payable
Cash flow information:
Cash paid for interest		$ 1,078,000	1,063,000	758,000
Junior subordinated debt
Cash flow information:
Cash paid for interest		315,000	258,000	220,000
Deposits and repurchase agreements
Cash flow information:
Cash paid for interest		$ 7,701,000	$ 7,051,000	$ 6,452,000