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, 2017	15,212,133
Balance at Dec. 31, 2017	$ 152	$ 215,659	$ 419,423	$ 67,504	$ 694	$ 703,432
Reclassification due to new accounting standards at Dec. 31, 2017			68,201	(68,201)
Net income (loss) attributable to National HealthCare Corporation			(2,791)			(2,791)
Net loss attributable to noncontrolling interest					(108)	(108)
Other comprehensive income (loss)				(2,219)		(2,219)
Stock–based compensation		428				428
Shares sold – options exercised (in shares)	21,906
Shares sold – options exercised		1,067				1,067
Repurchase of common shares (in shares)	(14,506)
Repurchase of common shares		(867)				(867)
Dividends declared to common stockholders			(7,305)			(7,305)
Balance (in shares) at Mar. 31, 2018	15,219,533
Balance at Mar. 31, 2018	$ 152	216,287	477,528	(2,916)	586	691,637
Balance (in shares) at Dec. 31, 2017	15,212,133
Balance at Dec. 31, 2017	$ 152	215,659	419,423	67,504	694	703,432
Reclassification due to new accounting standards at Dec. 31, 2017			68,201	(68,201)
Shares sold – options exercised (in shares)						68,291
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 (loss) 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					318,152
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)
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