SHORT-TERM BORROWINGS: (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	$ 109,561	$ 79,219
Average amount outstanding	90,561	60,915
Maximum amount outstanding at a month end	$ 116,061	$ 91,750
Average interest rate during year (percent)	0.63%	1.84%
Interest rate at year-end (percent)	0.11%	0.31%
Maturity over 90 days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	$ 798	$ 1,031
Maturity 30 to 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	21,342	6,552
Maturity up to 30 days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	1,086	1,927
Maturity Overnight [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	$ 86,335	$ 69,709