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INCOME TAXES (Details 1) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
INCOME TAXES (Details 1) - USD ($) $ in Thousands	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
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Computed statutory federal income tax provision									$ 32,744	$ 47,091	$ 39,226
State taxes, net of federal tax benefit									9,633	6,817	5,643
Merger and other related costs (non-deductible)									130	213	210
Change in valuation allowance									49	31	28
Effective Income Tax Rate Reconciliation, Revaluation of Net Deferred Tax Assets									0	1,895	0
New Markets Tax Credits									(3,960)	(3,960)	(6,360)
Increase in cash surrender value of life insurance									(1,160)	(1,445)	(1,431)
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount									(1,030)	(1,253)	(1,641)
Stock-based compensation									(885)	(1,258)	0
Nontaxable interest, net									(566)	(987)	(996)
Other, net									(651)	197	748
Total expense	$ 8,258	$ 9,969	$ 9,249	$ 6,828	$ 14,915	$ 12,681	$ 10,731	$ 9,014	$ 34,304	$ 47,341	$ 35,427
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Computed statutory federal income tax provision									21.00%	35.00%	35.00%
State taxes, net of federal tax benefit									6.18%	5.07%	5.03%
Merger and other related costs (non-deductible)									0.08%	0.16%	0.19%
Change in valuation allowance									0.03%	0.02%	0.02%
Effective Income Tax Rate Reconciliation, Revaluation of Net Deferred Tax Asset, Percent									0.00%	1.41%	0.00%
New Markets Tax Credits									(2.54%)	(2.94%)	(5.67%)
Increase in cash surrender value of life insurance									(0.74%)	(1.07%)	(1.28%)
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Percent									(0.66%)	(0.93%)	(1.46%)
Stock-based compensation									(0.57%)	(0.94%)	0.00%
Nontaxable interest, net									(0.36%)	(0.73%)	(0.89%)
Other, net									(0.42%)	0.15%	0.67%
Total expense									22.00%	35.20%	31.61%