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, 2016	15,162,938
Balance at Dec. 31, 2016	$ 152	$ 211,457	$ 391,934	$ 66,068	$ 0	$ 669,611
Net income attributable to National HealthCare Corporation	0	0	56,205	0	0	56,205
Net loss attributable to noncontrolling interest	0	0	0	0	(523)	(523)
Equity contributed by noncontrolling interest	0	0	0	0	1,217	1,217
Other comprehensive income (loss)	0	0	0	1,436	0	1,436
Stock–based compensation	$ 0	1,678	0	0	0	$ 1,678
Shares sold – options exercised (in shares)	49,195					48,995
Shares sold – options exercised	$ 0	2,524	0	0	0	$ 2,524
Dividends declared to common stockholders	$ 0	0	(28,716)	0	0	(28,716)
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	0	0	58,964	0	0	58,964
Net loss attributable to noncontrolling interest	0	0	0	0	(265)	(265)
Equity contributed by noncontrolling interest	0	0	0	0	750	750
Other comprehensive income (loss)	0	0	0	(2,048)	0	(2,048)
Stock–based compensation	$ 0	1,778	0	0	0	$ 1,778
Shares sold – options exercised (in shares)	57,375					68,291
Shares sold – options exercised	$ 1	2,865	0	0	0	$ 2,866
Dividends declared to common stockholders	0	0	(30,153)	0	0	(30,153)
Reclassification due to new accounting standards at Dec. 31, 2017	$ 0	0	68,201	(68,201)	0	0
Repurchase of common shares (in shares)	(14,506)
Repurchase of common shares	$ 0	(867)	0	0	0	(867)
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	0	0	68,211	0	0	68,211
Net loss attributable to noncontrolling interest	0	0	0	0	(235)	(235)
Other comprehensive income (loss)	0	0	0	5,305	0	5,305
Stock–based compensation	$ 0	1,878	0	0	0	$ 1,878
Shares sold – options exercised (in shares)	87,600					346,168
Shares sold – options exercised	$ 0	2,346	0	0	0	$ 2,346
Dividends declared to common stockholders	$ 0	0	(31,553)	0	0	(31,553)
Repurchase of common shares (in shares)	(10,396)
Repurchase of common shares	$ 0	(872)	0	0	0	(872)
Distributions attributable to noncontrolling interest	$ 0	0	0	0	(468)	(468)
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