Consolidated Statements of Equity - 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, 2015	15,000,616
Balance at Dec. 31, 2015	$ 150	$ 209,469	$ 368,013	$ 53,364		$ 630,996
Net income attributable to National HealthCare Corporation			50,538			50,538
Other comprehensive income (loss)				12,704		12,704
Stock–based compensation		509				509
Tax expense from exercise of stock options		(1,096)				$ (1,096)
Shares sold – options exercised (in shares)	292,322					499,066
Shares sold – options exercised	$ 3	10,769				$ 10,772
Repurchase of common shares (in shares)	(130,000)
Repurchase of common shares	$ (1)	(8,194)				(8,195)
Dividends declared to common stockholders			(26,617)			(26,617)
Net loss attributable to noncontrolling interest
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			56,205			56,205
Other comprehensive income (loss)				1,436		1,436
Stock–based compensation		1,678				$ 1,678
Shares sold – options exercised (in shares)	49,195					48,995
Shares sold – options exercised		2,524				$ 2,524
Dividends declared to common stockholders			(28,716)			(28,716)
Net loss attributable to noncontrolling interest					(523)	(523)
Equity contributed by noncontrolling interest					1,217	1,217
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			58,964			58,964
Other comprehensive income (loss)				(2,048)		(2,048)
Stock–based compensation		1,778				$ 1,778
Shares sold – options exercised (in shares)	57,375					68,291
Shares sold – options exercised	$ 1	2,865				$ 2,866
Repurchase of common shares (in shares)	(14,506)
Repurchase of common shares		(867)				(867)
Dividends declared to common stockholders			(30,153)			(30,153)
Net loss attributable to noncontrolling interest					(265)	(265)
Equity contributed by noncontrolling interest					750	750
Reclassification due to new accounting standards at Dec. 31, 2017			68,201	(68,201)
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