Note 6 - Per Share Amounts - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Net income attributable to American Shared Hospital Services	$ 269,000	$ 29,000
Weighted average common shares for basic earnings per share (in shares)	6,201,000	6,254,000
Diluted effect of stock options and restricted stock awards (in shares)	98,000	68,000
Weighted average common shares for diluted earnings per share (in shares)	6,299,000	6,322,000
Basic earnings per share (in dollars per share)	$ 0.04	$ 0.00
Diluted earnings per share (in dollars per share)	$ 0.04	$ 0.00