Per Share Amounts (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income attributable to American Shared Hospital Services	$ 168,000	$ 99,000	$ 845,000	$ 505,000
Weighted average common shares for basic earnings per share	5,841,000	5,947,000	5,831,000	5,745,000
Diluted effect of stock options and restricted stock	50,000	94,000	24,000	167,000
Weighted average common shares for diluted earnings per share	5,891,000	6,041,000	5,855,000	5,912,000
Basic earnings per share	$ 0.03	$ 0.02	$ 0.14	$ 0.09
Diluted earnings per share	$ 0.03	$ 0.02	$ 0.14	$ 0.09