SHORT-TERM BORROWINGS: (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	$ 31,007	$ 32,981
Average amount outstanding	37,949	32,617
Maximum amount outstanding at a month end	$ 80,989	$ 84,819
Average interest rate during year (percent)	0.35%	0.21%
Interest rate at year-end (percent)	0.64%	0.23%
Maturity over 90 days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	$ 758	$ 718
Maturity 30 to 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	9,516	10,794
Maturity up to 30 days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	9,495	11,049
Maturity Overnight [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase-agreements	$ 11,238	$ 10,420