Cover - USD ($)	12 Months Ended
	Dec. 31, 2020	Mar. 17, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2020
Current Fiscal Year End Date	--12-31
Entity File Number	0-31525
Entity Registrant Name	AMERICAN RIVER BANKSHARES
Entity Central Index Key	0001108236
Entity Tax Identification Number	68-0352144
Entity Incorporation, State or Country Code	CA
Entity Address, Address Line One	3100 Zinfandel Drive
Entity Address, City or Town	Rancho Cordova
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95670
City Area Code	(916)
Local Phone Number	851-0123
Title of 12(b) Security	Common Stock, no par value
Trading Symbol	AMRB
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 57,305,000
Entity Common Stock, Shares Outstanding		5,962,466