Note 9 - Earning 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	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Basic:
Weighted average common shares outstanding (in shares)	15,347,129	15,306,174	15,270,154
Net income attributable to common stockholders of National Healthcare Corporation	$ 138,590	$ 41,871	$ 68,211
Earnings per common share, basic (in dollars per share)	$ 9.03	$ 2.74	$ 4.47
Diluted:
Weighted average common shares outstanding (in shares)	15,347,129	15,306,174	15,270,154
Assumed average common shares outstanding (in shares)	15,416,716	15,369,523	15,360,046
Net income attributable to common stockholders of National Healthcare Corporation	$ 138,590	$ 41,871	$ 68,211
Earnings per common share, diluted (in dollars per share)	$ 8.99	$ 2.72	$ 4.44
Share-based Payment Arrangement, Option [Member]
Diluted:
Dilutive effect of share-based awards (in shares)	69,587	63,349	89,892