SHORT-TERM BORROWINGS: (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	$ 79,219	$ 26,406
Average amount outstanding	60,915	41,557
Maximum amount outstanding at a month end	$ 91,750	$ 69,656
Average interest rate during year (percent)	1.84%	1.24%
Interest rate at year-end (percent)	0.31%	1.86%
Maturity over 90 days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	$ 1,031	$ 546
Maturity 30 to 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	6,552	8,683
Maturity up to 30 days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	1,927	6,307
Maturity Overnight [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	$ 69,709	$ 10,870