Per Share Amounts - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net (loss) income attributable to American Shared Hospital Services	$ (135)	$ 270
Weighted average common shares for basic earnings per share (in shares)	6,126	5,853
Diluted effect of stock options and restricted stock (in shares)	27	33
Weighted average common shares for diluted earnings per share (in shares)	6,153	5,886
Basic (loss) earnings per share (in USD per share)	$ (0.02)	$ 0.05
Diluted (loss) earnings per share (in USD per share)	$ (0.02)	$ 0.05