BUSINESS SEGMENTS - Schedule of Income and Total Assets for Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net interest income	$ 30,914	$ 30,085	$ 29,268	$ 30,007	$ 29,385	$ 28,142	$ 29,243	$ 28,393	$ 120,274	$ 115,163	$ 111,141
Noninterest income									54,696	44,193	34,627
Total income									174,970	159,356	145,768
Provision for loan losses	1,950	800	1,150	100	1,500	500	300	1,250	4,000	3,550	5,850
Compensation and benefits									70,129	62,802	53,956
Premises and equipment expense									14,735	13,497	11,988
FDIC expense									277	2,443	2,366
Other noninterest expense									19,707	19,344	17,301
Total noninterest expense									108,848	101,636	91,461
Income before income tax expense	17,788	17,442	14,971	15,921	13,616	14,341	15,742	14,021	66,122	57,720	54,307
Income tax expense	5,555	5,216	3,421	4,496	2,887	3,617	3,832	3,214	18,688	13,550	17,810
Net income	12,233	$ 12,226	$ 11,550	$ 11,425	10,729	$ 10,724	$ 11,910	$ 10,807	47,434	44,170	36,497
Total assets at period end	5,182,879				4,617,858				5,182,879	4,617,858	4,260,547
Banking [Member]
Net interest income									114,983	110,001	105,353
Noninterest income									14,999	10,013	10,943
Total income									129,982	120,014	116,296
Provision for loan losses									4,000	3,550	5,850
Compensation and benefits									48,925	44,875	42,917
Premises and equipment expense									12,533	11,747	10,682
FDIC expense									277	2,443	2,366
Other noninterest expense									10,932	11,313	9,683
Total noninterest expense									76,667	73,928	71,498
Income before income tax expense									53,315	46,086	44,798
Income tax expense									15,069	10,819	14,691
Net income									38,246	35,267	30,107
Total assets at period end	5,095,744				4,547,179				5,095,744	4,547,179	4,202,957
Wealth Management [Member]
Net interest income									5,291	5,162	5,788
Noninterest income									39,697	34,180	23,684
Total income									44,988	39,342	29,472
Provision for loan losses									0	0	0
Compensation and benefits									21,204	17,927	11,039
Premises and equipment expense									2,202	1,750	1,306
FDIC expense									0	0	0
Other noninterest expense									8,775	8,031	7,618
Total noninterest expense									32,181	27,708	19,963
Income before income tax expense									12,807	11,634	9,509
Income tax expense									3,619	2,731	3,119
Net income									9,188	8,903	6,390
Total assets at period end	$ 87,135				$ 70,679				$ 87,135	$ 70,679	$ 57,590