Interim Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Noncontrolling Interest [Member]	Total
Balance (in shares) at Dec. 31, 2018	15,255,002
Balance at Dec. 31, 2018	$ 153	$ 219,435	$ 516,435	$ (2,745)	$ 1,179	$ 734,457
Net income attributable to National HealthCare Corporation			21,269			21,269
Net loss attributable to noncontrolling interest					(38)	(38)
Other comprehensive income (loss)				2,548		2,548
Stock–based compensation		424				424
Shares sold – options exercised (in shares)	59,384
Shares sold – options exercised		579				579
Repurchase of common shares (in shares)	(10,396)
Repurchase of common shares		(872)				(872)
Dividends declared to common stockholders			(7,652)			(7,652)
Net income/(loss) attributable to National HealthCare Corporation			21,269			21,269
Net income attributable to noncontrolling interest					(38)	(38)
Balance (in shares) at Mar. 31, 2019	15,303,990
Balance at Mar. 31, 2019	$ 153	219,566	530,052	(197)	1,141	750,715
Balance (in shares) at Dec. 31, 2018	15,255,002
Balance at Dec. 31, 2018	$ 153	219,435	516,435	(2,745)	1,179	$ 734,457
Shares sold – options exercised (in shares)						346,168
Balance (in shares) at Dec. 31, 2019	15,332,206
Balance at Dec. 31, 2019	$ 153	222,787	553,093	2,560	476	$ 779,069
Net income attributable to National HealthCare Corporation			(26,852)			(26,852)
Net loss attributable to noncontrolling interest					36	36
Other comprehensive income (loss)				(2,012)		(2,012)
Stock–based compensation		466				$ 466
Shares sold – options exercised (in shares)	15,006					7,615
Shares sold – options exercised		400				$ 400
Repurchase of common shares (in shares)	(611)
Repurchase of common shares		(53)				(53)
Dividends declared to common stockholders			(7,980)			(7,980)
Net income/(loss) attributable to National HealthCare Corporation			(26,852)			(26,852)
Net income attributable to noncontrolling interest					36	36
Equity contributed by noncontrolling interest					281	281
Balance (in shares) at Mar. 31, 2020	15,346,601
Balance at Mar. 31, 2020	$ 153	$ 223,600	$ 518,261	$ 548	$ 793	$ 743,355