Note 8 - 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, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Basic:
Weighted average common shares outstanding (in shares)	15,484,464	15,411,680	15,461,804	15,384,758
Net income attributable to National HealthCare Corporation	$ 39,239	$ 42,789	$ 95,166	$ 95,846
Earnings per common share, basic (in dollars per share)	$ 2.53	$ 2.78	$ 6.15	$ 6.23
Diluted:
Weighted average common shares outstanding (in shares)	15,484,464	15,411,680	15,461,804	15,384,758
Effects of dilutive instruments (in shares)	180,066	255,641	151,701	191,536
Weighted average common shares outstanding (in shares)	15,664,530	15,667,321	15,613,505	15,576,294
Net income attributable to National HealthCare Corporation	$ 39,239	$ 42,789	$ 95,166	$ 95,846
Earnings per common share, diluted (in dollars per share)	$ 2.5	$ 2.73	$ 6.1	$ 6.15