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, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Basic:
Weighted average common shares outstanding (in shares)	15,411,680	15,299,913	15,384,758	15,311,453
Net income attributable to National HealthCare Corporation	$ 42,789	$ 10,388	$ 95,846	$ 38,392
Earnings per common share, basic (in dollars per share)	$ 2.78	$ 0.68	$ 6.23	$ 2.51
Diluted:
Weighted average common shares outstanding (in shares)	15,411,680	15,299,913	15,384,758	15,311,453
Effects of dilutive instruments (in shares)	255,641	24,598	191,536	22,816
Weighted average common shares outstanding (in shares)	15,667,321	15,324,511	15,576,294	15,334,269
Net income attributable to National HealthCare Corporation	$ 42,789	$ 10,388	$ 95,846	$ 38,392
Earnings per common share, diluted (in dollars per share)	$ 2.73	$ 0.68	$ 6.15	$ 2.5