Cover Page - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Mar. 22, 2021	Jun. 30, 2020
Document and Entity Information [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-08789
Entity Registrant Name	American Shared Hospital Services
Entity Incorporation, State or Country Code	CA
Entity Tax Identification Number	94-2918118
Entity Address, Address Line One	Two Embarcadero Center
Entity Address, Address Line Two	Suite 410,
Entity Address, City or Town	San Francisco,
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94111-4107
City Area Code	415
Local Phone Number	788-5300
Title of 12(b) Security	Common Stock No Par Value
Trading Symbol	AMS
Security Exchange Name	NYSEAMER
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
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 8,188
Entity Common Stock, Shares Outstanding		5,801
Documents Incorporated by Reference	Portions of the registrant’s definitive Proxy Statement for the 2021 Annual Meeting of Shareholders are incorporated by reference into Part III of this report.
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0000744825