LOANS: (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	$ 1,903,609	$ 1,835,974
Deferred costs, net	3,152	3,206
Allowance for loan losses	(19,909)	(18,773)	$ (19,946)	$ (18,839)
TOTAL	1,886,852	1,820,407
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	1,139,490	1,106,182
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	436,143	423,911
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	$ 327,976	$ 305,881