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, 2016	15,162,938
Balance at Dec. 31, 2016	$ 152	$ 211,457	$ 391,934	$ 66,068		$ 669,611
Net income attributable to National HealthCare Corporation			23,383			23,383
Net loss attributable to noncontrolling interest					(181)	(181)
Equity contributed by noncontrolling interest					970	970
Other comprehensive income (loss)				7,472		7,472
Stock–based compensation		832				832
Shares sold – options exercised (in shares)	32,092
Shares sold – options exercised		1,496				1,496
Dividends declared to common stockholders			(14,125)			(14,125)
Balance (in shares) at Jun. 30, 2017	15,195,030
Balance at Jun. 30, 2017	$ 152	213,785	401,192	73,540	789	689,458
Balance (in shares) at Dec. 31, 2016	15,162,938
Balance at Dec. 31, 2016	$ 152	211,457	391,934	66,068		$ 669,611
Shares sold – options exercised (in shares)						48,995
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
Net income attributable to National HealthCare Corporation			19,670			19,670
Net loss attributable to noncontrolling interest					(194)	(194)
Other comprehensive income (loss)				(2,858)		(2,858)
Stock–based compensation		1,177				$ 1,177
Shares sold – options exercised (in shares)	28,027					33,526
Shares sold – options exercised		1,327				$ 1,327
Dividends declared to common stockholders			(14,917)			(14,917)
Repurchase of common shares (in shares)	(14,506)
Repurchase of common shares		(867)				(867)
Balance (in shares) at Jun. 30, 2018	15,225,654
Balance at Jun. 30, 2018	$ 152	217,296	492,377	(3,555)	500	706,770
Reclassification due to new accounting standards			$ 68,201	$ (68,201)