BUSINESS SEGMENTS (Details) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2017 USD ($) segments	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Number of Operating Segments | segments													2
Net interest income	$ 28,586	$ 29,992	$ 26,972	$ 25,591	$ 24,580	$ 24,269	$ 24,176	$ 23,410	$ 22,819	$ 21,706	$ 20,344	$ 19,583	$ 111,141	$ 96,435	$ 84,452
Noninterest income													34,627	28,918	23,714
Total income													145,768	125,353	108,166
Provision for loan losses	1,650	400	2,200	1,600	1,500	2,100	2,200	1,700	1,950	1,600	2,200	1,350	5,850	7,500	7,100
Compensation and benefits													53,956	45,003	40,278
Premises and equipment													11,988	11,245	11,569
FDIC expense													2,366	4,758	2,154
Other noninterest expense													17,301	14,106	14,925
Total noninterest expense													91,461	82,612	76,026
Income before income tax expense	13,291	16,462	12,848	11,706	11,787	11,538	10,649	8,767	6,599	8,817	8,377	8,347	54,307	42,741	32,140
Income tax expense	2,922	6,256	4,908	3,724	4,479	4,422	4,085	3,278	2,256	3,434	3,139	3,339	17,810	16,264	12,168
Net income	10,369	$ 10,206	$ 7,940	$ 7,982	7,308	$ 7,116	$ 6,564	$ 5,489	4,343	$ 5,383	$ 5,238	$ 5,008	36,497	26,477	19,972
Total assets at period end	4,260,547				3,878,633				3,364,659				4,260,547	3,878,633	3,364,659
Banking [Member]
Net interest income													105,353	91,334	80,190
Noninterest income													10,943	10,217	6,434
Total income													116,296	101,551	86,624
Provision for loan losses													5,850	7,500	7,100
Compensation and benefits													42,917	36,028	31,889
Premises and equipment													10,682	10,213	10,534
FDIC expense													2,366	4,758	2,154
Other noninterest expense													9,466	8,565	9,562
Total noninterest expense													71,281	67,064	61,239
Income before income tax expense													45,015	34,487	25,385
Income tax expense													14,763	13,123	9,611
Net income													30,252	21,364	15,774
Total assets at period end	4,202,957				3,832,765				3,326,219				4,202,957	3,832,765	3,326,219
Wealth Management Division [Member]
Net interest income													5,788	5,101	4,262
Noninterest income													23,684	18,701	17,280
Total income													29,472	23,802	21,542
Provision for loan losses
Compensation and benefits													11,039	8,975	8,389
Premises and equipment													1,306	1,032	1,035
FDIC expense
Other noninterest expense													7,835	5,541	5,363
Total noninterest expense													20,180	15,548	14,787
Income before income tax expense													9,292	8,254	6,755
Income tax expense													3,047	3,141	2,557
Net income													6,245	5,113	4,198
Total assets at period end	$ 57,590				$ 45,868				$ 38,440				$ 57,590	$ 45,868	$ 38,440