FINANCIAL INSTRUMENTS WITH OFF-BALANCE-SHEET RISK: (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Other Commitments			$ 119,108,000	$ 105,872,000
TOTAL			716,382,000	551,760,000
Minimum
Loss Contingencies [Line Items]
Loans and Leases Receivable, Commitments, Fixed Rates	$ 0.0325	$ 0.0425
Maximum
Loss Contingencies [Line Items]
Loans and Leases Receivable, Commitments, Fixed Rates	$ 0.0600	$ 0.0725
Home Equity
Loss Contingencies [Line Items]
TOTAL			88,672,000	87,327,000
Commercial Operating Lines
Loss Contingencies [Line Items]
TOTAL			508,602,000	358,561,000
Commercial letters of credit
Loss Contingencies [Line Items]
TOTAL			$ 3,601,000	$ 3,851,000