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		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Basic:
Weighted average common shares outstanding (in shares)	15,462,135	15,391,535	15,450,286	15,371,150
Net income attributable to National HealthCare Corporation	$ 23,722	$ 26,844	$ 55,927	$ 53,057
Earnings per common share, basic (in dollars per share)	$ 1.53	$ 1.74	$ 3.62	$ 3.45
Diluted:
Weighted average common shares outstanding (in shares)	15,462,135	15,391,535	15,450,286	15,371,150
Effects of dilutive instruments (in shares)	137,503	164,077	137,497	159,474
Weighted average common shares outstanding (in shares)	15,599,638	15,555,612	15,587,783	15,530,624
Net income attributable to National HealthCare Corporation	$ 23,722	$ 26,844	$ 55,927	$ 53,057
Earnings per common share, diluted (in dollars per share)	$ 1.52	$ 1.73	$ 3.59	$ 3.42