NATURE OF OPERATIONS - Narrative (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020 USD ($) office branch	Sep. 30, 2020 USD ($) office branch
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Qualified Affordable Housing Project Investments, Commitment	$ 4,800	$ 4,800
Amortization Method Qualified Affordable Housing Project Investments	1,600	1,600
Qualified Affordable Housing Project Investments, Unfunded Commitment	3,300	3,300
Amortization Method Qualified Affordable Housing Project Investments, Amortization	21	21
Affordable Housing Tax Credits and Other Tax Benefits, Amount	$ (28)	$ (28)
Sonoma, Marin, Santa Clara, and Los Angeles Counties
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of full service branches | branch	10	10
King County, Washington
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of full service branches | branch	1	1
California
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of loan production offices | office	7	7