GOODWILL AND INTANGIBLE ASSETS: (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 21,205	$ 21,205
Accumulated Amortization	12,233	10,562
Core deposit intangible
Finite-Lived Intangible Assets [Line Items]
Gross Amount	21,205	21,205
Accumulated Amortization	$ 12,233	$ 10,562