Note 9 - Earnings Per Share - Summary of Earnings and Weighted Average Number of Common Shares Used in Calculation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Basic:
Weighted average common shares outstanding (in shares)	15,299,913	15,445,569	15,311,453	15,438,375
Net income attributable to National HealthCare Corporation	$ 10,388	$ (2,429)	$ 38,392	$ 16,092
Earnings per common share, basic (in dollars per share)	$ 0.68	$ (0.16)	$ 2.51	$ 1.04
Diluted:
Weighted average common shares outstanding (in shares)	15,299,913	15,445,569	15,311,453	15,438,375
Effects of dilutive instruments (in shares)	24,598	0	22,816	38,728
Weighted average common shares outstanding (in shares)	15,324,511	15,445,569	15,334,269	15,477,103
Net income attributable to National HealthCare Corporation	$ 10,388	$ (2,429)	$ 38,392	$ 16,092
Earnings per common share, diluted (in dollars per share)	$ 0.68	$ (0.16)	$ 2.5	$ 1.04