GOODWILL AND OTHER INTANGIBLE ASSETS (Gross Carrying Amouns and Accumulated Amortization of Intangible Assets and Goodwill) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 12,156	$ 12,156
Accumulated Amortization	(2,859)	(2,368)
Net Carrying Amount	9,297	9,788
Goodwill	347,149	347,149
Core deposits [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	10,678	10,678
Accumulated Amortization	(2,378)	(1,941)
Net Carrying Amount	$ 8,300	$ 8,737
Core deposits [Member] | Weighted average [Member]
Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	8 years 9 months 18 days	9 years
Other Identifiable Intangible Assets
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,478	$ 1,478
Accumulated Amortization	(481)	(427)
Net Carrying Amount	$ 997	$ 1,051
Other Identifiable Intangible Assets | Weighted average [Member]
Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	10 years 4 months 24 days	10 years 7 months 6 days