LOAN LOSS ALLOWANCE - Loans by Credit Risk Rating (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Credit quality information
Total loans	$ 2,428,862	$ 1,129,064
Special mention
Credit quality information
Total loans	13,626	8,669
Non-accrual
Credit quality information
Total loans	8,568	2,733
Substandard
Credit quality information
Total loans	25,401	20,368
Total classified
Credit quality information
Total loans	33,969	23,101
Total Criticized
Credit quality information
Total loans	47,595	31,770
Business Activities Loans
Credit quality information
Total loans	1,359,516	1,129,064
Business Activities Loans | Special mention
Credit quality information
Total loans	8,864	8,669
Business Activities Loans | Non-accrual
Credit quality information
Total loans	5,116	2,733
Business Activities Loans | Substandard
Credit quality information
Total loans	15,774	20,368
Business Activities Loans | Total classified
Credit quality information
Total loans	20,890	23,101
Business Activities Loans | Total Criticized
Credit quality information
Total loans	29,754	31,770
Business Activities Loans | Commercial real estate
Credit quality information
Total loans	489,539	418,119
Business Activities Loans | Commercial real estate | Pass
Credit quality information
Total loans	466,942	391,663
Business Activities Loans | Commercial real estate | Special mention
Credit quality information
Total loans	6,867	5,868
Business Activities Loans | Commercial real estate | Substandard
Credit quality information
Total loans	15,730	20,588
Business Activities Loans | Commercial real estate | Construction and land development
Credit quality information
Total loans	33,692	14,695
Business Activities Loans | Commercial real estate | Construction and land development | Pass
Credit quality information
Total loans	33,008	14,695
Business Activities Loans | Commercial real estate | Construction and land development | Special mention
Credit quality information
Total loans	47	0
Business Activities Loans | Commercial real estate | Construction and land development | Substandard
Credit quality information
Total loans	637	0
Business Activities Loans | Commercial real estate | Other commercial real estate
Credit quality information
Total loans	455,847	403,424
Business Activities Loans | Commercial real estate | Other commercial real estate | Pass
Credit quality information
Total loans	433,934	376,968
Business Activities Loans | Commercial real estate | Other commercial real estate | Special mention
Credit quality information
Total loans	6,820	5,868
Business Activities Loans | Commercial real estate | Other commercial real estate | Substandard
Credit quality information
Total loans	15,093	20,588
Business Activities Loans | Commercial and industrial
Credit quality information
Total loans	243,445	151,240
Business Activities Loans | Commercial and industrial | Pass
Credit quality information
Total loans	239,293	145,926
Business Activities Loans | Commercial and industrial | Special mention
Credit quality information
Total loans	2,014	2,802
Business Activities Loans | Commercial and industrial | Substandard
Credit quality information
Total loans	2,138	2,512
Business Activities Loans | Commercial and industrial | Other Commercial
Credit quality information
Total loans	172,186	103,586
Business Activities Loans | Commercial and industrial | Other Commercial | Pass
Credit quality information
Total loans	168,608	98,968
Business Activities Loans | Commercial and industrial | Other Commercial | Special mention
Credit quality information
Total loans	1,757	2,384
Business Activities Loans | Commercial and industrial | Other Commercial | Substandard
Credit quality information
Total loans	1,821	2,234
Business Activities Loans | Commercial and industrial | Agricultural and other loans to farmers
Credit quality information
Total loans	30,483	31,808
Business Activities Loans | Commercial and industrial | Agricultural and other loans to farmers | Pass
Credit quality information
Total loans	30,075	31,279
Business Activities Loans | Commercial and industrial | Agricultural and other loans to farmers | Special mention
Credit quality information
Total loans	91	251
Business Activities Loans | Commercial and industrial | Agricultural and other loans to farmers | Substandard
Credit quality information
Total loans	317	278
Business Activities Loans | Commercial and industrial | Tax exempt
Credit quality information
Total loans	40,776	15,846
Business Activities Loans | Commercial and industrial | Tax exempt | Pass
Credit quality information
Total loans	40,610	15,679
Business Activities Loans | Commercial and industrial | Tax exempt | Special mention
Credit quality information
Total loans	166	167
Business Activities Loans | Commercial and industrial | Tax exempt | Substandard
Credit quality information
Total loans	0	0
Acquired Loans
Credit quality information
Total loans	1,069,346
Acquired Loans | Special mention
Credit quality information
Total loans	4,762	0
Acquired Loans | Non-accrual
Credit quality information
Total loans	3,452	0
Acquired Loans | Substandard
Credit quality information
Total loans	9,627	0
Acquired Loans | Total classified
Credit quality information
Total loans	13,079	0
Acquired Loans | Total Criticized
Credit quality information
Total loans	17,841	0
Acquired Loans | Commercial real estate
Credit quality information
Total loans	304,033	0
Acquired Loans | Commercial real estate | Pass
Credit quality information
Total loans	293,470	0
Acquired Loans | Commercial real estate | Special mention
Credit quality information
Total loans	2,708	0
Acquired Loans | Commercial real estate | Substandard
Credit quality information
Total loans	7,855	0
Acquired Loans | Commercial real estate | Construction and land development
Credit quality information
Total loans	15,593	0
Acquired Loans | Commercial real estate | Construction and land development | Pass
Credit quality information
Total loans	15,336	0
Acquired Loans | Commercial real estate | Construction and land development | Special mention
Credit quality information
Total loans	233	0
Acquired Loans | Commercial real estate | Construction and land development | Substandard
Credit quality information
Total loans	24	0
Acquired Loans | Commercial real estate | Other commercial real estate
Credit quality information
Total loans	288,440	0
Acquired Loans | Commercial real estate | Other commercial real estate | Pass
Credit quality information
Total loans	278,134	0
Acquired Loans | Commercial real estate | Other commercial real estate | Special mention
Credit quality information
Total loans	2,475	0
Acquired Loans | Commercial real estate | Other commercial real estate | Substandard
Credit quality information
Total loans	7,831	0
Acquired Loans | Commercial and industrial
Credit quality information
Total loans	113,627	0
Acquired Loans | Commercial and industrial | Pass
Credit quality information
Total loans	109,478	0
Acquired Loans | Commercial and industrial | Special mention
Credit quality information
Total loans	2,053	0
Acquired Loans | Commercial and industrial | Substandard
Credit quality information
Total loans	2,096	0
Acquired Loans | Commercial and industrial | Other Commercial
Credit quality information
Total loans	68,090	0
Acquired Loans | Commercial and industrial | Other Commercial | Pass
Credit quality information
Total loans	63,941	0
Acquired Loans | Commercial and industrial | Other Commercial | Special mention
Credit quality information
Total loans	2,053	0
Acquired Loans | Commercial and industrial | Other Commercial | Substandard
Credit quality information
Total loans	2,096	0
Acquired Loans | Commercial and industrial | Agricultural and other loans to farmers
Credit quality information
Total loans	0	0
Acquired Loans | Commercial and industrial | Agricultural and other loans to farmers | Pass
Credit quality information
Total loans	0	0
Acquired Loans | Commercial and industrial | Agricultural and other loans to farmers | Special mention
Credit quality information
Total loans	0	0
Acquired Loans | Commercial and industrial | Agricultural and other loans to farmers | Substandard
Credit quality information
Total loans	0	0
Acquired Loans | Commercial and industrial | Tax exempt
Credit quality information
Total loans	45,537	0
Acquired Loans | Commercial and industrial | Tax exempt | Pass
Credit quality information
Total loans	45,537	0
Acquired Loans | Commercial and industrial | Tax exempt | Special mention
Credit quality information
Total loans	0	0
Acquired Loans | Commercial and industrial | Tax exempt | Substandard
Credit quality information
Total loans	$ 0	$ 0