LOANS AND ALLOWANCE FOR LOAN LOSSES - ACTIVITY IN THE ALLOWANCE FOR LOANS LOSSES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Dec. 31, 2015
Allowance for loan losses
Beginning balance	$ 11,633	$ 8,358	$ 9,769	$ 7,817
Charge-offs	(2,747)	(1,531)	(5,392)	(3,521)
Recoveries	259	597	595	1,173
Provision for loan losses	2,997	1,576	7,170	3,531
Ending balance	12,142	9,000	12,142	9,000
Ending balance:
Individually evaluated for impairment					$ 234	$ 487
Collectively evaluated for impairment					11,276	7,960
Total	11,633	8,358	9,769	7,817	12,142	9,769
Ending balance:
Individually evaluated for impairment					12,317	15,553
Collectively evaluated for impairment					5,059,203	2,920,061
Purchased credit-impaired					183,260	142,042
Total					5,254,780	3,077,656
Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses
Beginning balance			1,322
Ending balance	632		632
Ending balance:
Total	632		1,322		632	1,322
Commercial real estate
Allowance for loan losses
Beginning balance	4,525	3,137	3,682	2,796
Charge-offs	(171)	(103)	(262)	(359)
Recoveries	33	44	39	56
Provision for loan losses	152	319	1,080	904
Ending balance	4,539	3,397	4,539	3,397
Ending balance:
Individually evaluated for impairment					154	314
Collectively evaluated for impairment					4,127	2,976
Total	4,525	3,137	3,682	2,796	4,539	3,682
Ending balance:
Individually evaluated for impairment					7,461	8,449
Collectively evaluated for impairment					2,416,454	1,354,977
Purchased credit-impaired					80,541	87,750
Total					2,504,456	1,451,176
Commercial real estate | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses
Beginning balance			392
Ending balance	258		258
Ending balance:
Total	258		392		258	392
Commercial and industrial
Allowance for loan losses
Beginning balance	3,057	1,960	2,431	1,274
Charge-offs	(1,661)	(406)	(3,096)	(1,377)
Recoveries	81	429	158	679
Provision for loan losses	1,974	185	3,958	1,592
Ending balance	3,451	2,168	3,451	2,168
Ending balance:
Individually evaluated for impairment					41	106
Collectively evaluated for impairment					3,216	2,309
Total	3,057	1,960	2,431	1,274	3,451	2,431
Ending balance:
Individually evaluated for impairment					3,015	2,623
Collectively evaluated for impairment					753,235	540,685
Purchased credit-impaired					8,070	9,813
Total					764,320	553,121
Commercial and industrial | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses
Beginning balance			16
Ending balance	194		194
Ending balance:
Total	194		16		194	16
Construction and development
Allowance for loan losses
Beginning balance	1,282	665	866	1,691
Charge-offs	(32)	(134)	(147)	(201)
Recoveries	12	10	40	20
Provision for loan losses	134	201	637	(768)
Ending balance	1,396	742	1,396	742
Ending balance:
Individually evaluated for impairment					5	0
Collectively evaluated for impairment					1,391	704
Total	1,282	665	866	1,691	1,396	866
Ending balance:
Individually evaluated for impairment					370	177
Collectively evaluated for impairment					422,112	330,714
Purchased credit-impaired					16,608	14,413
Total					439,090	345,304
Construction and development | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses
Beginning balance			162
Ending balance	0		0
Ending balance:
Total	0		162		0	162
Residential real estate
Allowance for loan losses
Beginning balance	985	1,327	1,257	1,237
Charge-offs	(292)	(312)	(509)	(442)
Recoveries	74	57	267	109
Provision for loan losses	296	232	48	400
Ending balance	1,063	1,304	1,063	1,304
Ending balance:
Individually evaluated for impairment					34	0
Collectively evaluated for impairment					903	837
Total	985	1,327	1,257	1,237	1,063	1,257
Ending balance:
Individually evaluated for impairment					888	3,550
Collectively evaluated for impairment					605,924	315,030
Purchased credit-impaired					58,273	25,068
Total					665,085	343,648
Residential real estate | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses
Beginning balance			420
Ending balance	126		126
Ending balance:
Total	126		420		126	420
Construction and development
Allowance for loan losses
Beginning balance	289	269	237	194
Charge-offs	0	0	0	0
Recoveries	1	0	1	27
Provision for loan losses	32	(15)	84	33
Ending balance	322	254	322	254
Ending balance:
Individually evaluated for impairment					0	0
Collectively evaluated for impairment					322	233
Total	289	269	237	194	322	237
Ending balance:
Individually evaluated for impairment					0	417
Collectively evaluated for impairment					287,561	44,630
Purchased credit-impaired					1,954	1,216
Total					289,515	46,263
Construction and development | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses
Beginning balance			4
Ending balance	0		0
Ending balance:
Total	0		4		0	4
Home equity
Allowance for loan losses
Beginning balance	1,119	775	883	546
Charge-offs	(325)	(475)	(667)	(793)
Recoveries	29	9	31	163
Provision for loan losses	174	593	750	986
Ending balance	997	902	997	902
Ending balance:
Individually evaluated for impairment					0	67
Collectively evaluated for impairment					954	542
Total	1,119	775	883	546	997	883
Ending balance:
Individually evaluated for impairment					583	337
Collectively evaluated for impairment					508,888	274,042
Purchased credit-impaired					17,311	3,521
Total					526,782	277,900
Home equity | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses
Beginning balance			274
Ending balance	43		43
Ending balance:
Total	43		274		43	274
Other consumer
Allowance for loan losses
Beginning balance	376	225	413	79
Charge-offs	(266)	(101)	(711)	(349)
Recoveries	29	48	59	119
Provision for loan losses	235	61	613	384
Ending balance	374	233	374	233
Ending balance:
Individually evaluated for impairment					0	0
Collectively evaluated for impairment					363	359
Total	376	$ 225	413	$ 79	374	413
Ending balance:
Individually evaluated for impairment					0	0
Collectively evaluated for impairment					65,029	59,983
Purchased credit-impaired					503	261
Total					65,532	60,244
Other consumer | Receivables Acquired with Deteriorated Credit Quality
Allowance for loan losses
Beginning balance			54
Ending balance	11		11
Ending balance:
Total	$ 11		$ 54		$ 11	$ 54