FINANCIAL INSTRUMENTS WITH OFF-BALANCE-SHEET RISK: (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Loss Contingencies [Line Items]
Other Commitments			$ 105,872,000	$ 81,593,000
TOTAL			551,760,000	424,458,000
Minimum
Loss Contingencies [Line Items]
Loans and Leases Receivable, Commitments, Fixed Rates	$ 0.0425	$ 0.0450
Maximum
Loss Contingencies [Line Items]
Loans and Leases Receivable, Commitments, Fixed Rates	$ 0.0725	$ 0.0775
Commercial Operating Lines
Loss Contingencies [Line Items]
TOTAL			358,561,000	285,524,000
Commercial letters of credit
Loss Contingencies [Line Items]
TOTAL			3,851,000	4,673,000
Home Equity
Loss Contingencies [Line Items]
TOTAL			$ 87,327,000	$ 57,341,000