LOANS AND ALLOWANCE FOR LOAN LOSSES - Activity in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Allowance for loan losses:
Beginning Balance	$ 9,769	$ 7,817	$ 7,043
Charge-offs	(7,192)	(5,623)	(3,141)
Recoveries	771	1,330	502
Provision for loan losses	10,642	6,245	3,413
Ending balance	13,990	9,769	7,817
Ending balance:
Individually evaluated for impairment				$ 768	$ 487
Collectively evaluated for impairment				12,144	7,960
Purchased credit-impaired				1,078	1,322
Total	9,769	7,817	7,043	13,990	9,769
Ending balance:
Individually evaluated for impairment				27,261	15,553
Collectively evaluated for impairment				4,961,345	2,920,061
Purchased credit-impaired				172,191	142,042
Financing Receivable, Gross				5,160,797	3,077,656
Commercial real estate
Allowance for loan losses:
Beginning Balance	3,682	2,796	2,419
Charge-offs	(416)	(1,096)	(366)
Recoveries	108	58	46
Provision for loan losses	2,316	1,924	697
Ending balance	5,690	3,682	2,796
Ending balance:
Individually evaluated for impairment				651	314
Collectively evaluated for impairment				4,264	2,976
Purchased credit-impaired				775	392
Total	3,682	2,796	2,419	5,690	3,682
Ending balance:
Individually evaluated for impairment					8,449
Collectively evaluated for impairment				2,379,162	1,354,977
Purchased credit-impaired				77,761	87,750
Financing Receivable, Gross				2,475,144	1,451,176
Commercial and industrial
Allowance for loan losses:
Beginning Balance	2,431	1,274	805
Charge-offs	(4,313)	(2,337)	(1,034)
Recoveries	245	746	88
Provision for loan losses	5,598	2,748	1,415
Ending balance	3,961	2,431	1,274
Ending balance:
Individually evaluated for impairment				65	106
Collectively evaluated for impairment				3,685	2,309
Purchased credit-impaired				211	16
Total	2,431	1,274	805	3,961	2,431
Ending balance:
Individually evaluated for impairment					2,623
Collectively evaluated for impairment				708,373	540,685
Purchased credit-impaired				6,902	9,813
Financing Receivable, Gross				723,257	553,121
Commercial construction
Allowance for loan losses:
Beginning Balance	866	1,691	1,400
Charge-offs	(178)	(331)	(367)
Recoveries	42	0	69
Provision for loan losses	840	(494)	589
Ending balance	1,570	866	1,691
Ending balance:
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				1,568	704
Purchased credit-impaired				2	162
Total	866	1,691	1,400	1,570	866
Ending balance:
Individually evaluated for impairment					177
Collectively evaluated for impairment				449,264	330,714
Purchased credit-impaired				14,156	14,413
Financing Receivable, Gross				463,594	345,304
Residential real estate
Allowance for loan losses:
Beginning Balance	1,257	1,237	1,673
Charge-offs	(517)	(509)	(591)
Recoveries	280	161	131
Provision for loan losses	28	368	24
Ending balance	1,048	1,257	1,237
Ending balance:
Individually evaluated for impairment				52	0
Collectively evaluated for impairment				930	837
Purchased credit-impaired				66	420
Total	1,257	1,237	1,673	1,048	1,257
Ending balance:
Individually evaluated for impairment					3,550
Collectively evaluated for impairment				587,163	315,030
Purchased credit-impaired				54,614	25,068
Financing Receivable, Gross				642,661	343,648
Consumer construction and development
Allowance for loan losses:
Beginning Balance	237	194	187
Charge-offs	0	0	0
Recoveries	1	27	0
Provision for loan losses	102	16	7
Ending balance	340	237	194
Ending balance:
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				340	233
Purchased credit-impaired				0	4
Total	237	194	187	340	237
Ending balance:
Individually evaluated for impairment					417
Collectively evaluated for impairment				269,330	44,630
Purchased credit-impaired				1,846	1,216
Financing Receivable, Gross				271,176	46,263
Home equity
Allowance for loan losses:
Beginning Balance	883	546	476
Charge-offs	(894)	(943)	(429)
Recoveries	33	187	123
Provision for loan losses	961	1,093	376
Ending balance	983	883	546
Ending balance:
Individually evaluated for impairment				0	67
Collectively evaluated for impairment				959	542
Purchased credit-impaired				24	274
Total	883	546	476	983	883
Ending balance:
Individually evaluated for impairment					337
Collectively evaluated for impairment				507,025	274,042
Purchased credit-impaired				16,476	3,521
Financing Receivable, Gross				523,501	277,900
Other consumer
Allowance for loan losses:
Beginning Balance	413	79	83
Charge-offs	(874)	(407)	(354)
Recoveries	62	151	45
Provision for loan losses	797	590	305
Ending balance	398	413	79
Ending balance:
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				398	359
Purchased credit-impaired				0	54
Total	$ 413	$ 79	$ 83	398	413
Ending balance:
Individually evaluated for impairment					0
Collectively evaluated for impairment				61,028	59,983
Purchased credit-impaired				436	261
Financing Receivable, Gross				$ 61,464	$ 60,244