Per Share Amounts - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net (loss) income attributable to American Shared Hospital Services	$ (483)	$ 31	$ (618)	$ 301
Weighted average common shares for basic earnings per share (in shares)	6,008	5,876	6,066	5,862
Diluted effect of stock options and restricted stock (in shares)	69	30	69	33
Weighted average common shares for diluted earnings per share (in shares)	6,077	5,906	6,135	5,895
Basic (loss) earnings per share (in USD per share)	$ (0.08)	$ 0.01	$ (0.10)	$ 0.05
Diluted (loss) earnings per share (in USD per share)	$ (0.08)	$ 0.01	$ (0.10)	$ 0.05