Per Share Amounts (Details) - USD ($)	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income attributable to American Shared Hospital Services	$ 390,000	$ 293,000
Weighted average common shares for basic earnings per share	5,818,000	5,685,000
Diluted effect of stock options and restricted stock	37,000	199,000
Weighted average common shares for diluted earnings per share	5,855,000	5,884,000
Basic earnings per share	$ 0.07	$ 0.05
Diluted earnings per share	$ 0.07	$ 0.05

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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