Interim Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($)	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	$ 152,000	$ 215,659,000	$ 419,423,000	$ 67,504,000	$ 694,000	$ 703,432,000
Net income attributable to National HealthCare Corporation	0	0	(2,791,000)	0	0	(2,791,000)
Net loss attributable to noncontrolling interest	0	0	0	0	(108,000)	(108,000)
Other comprehensive income (loss)	0	0	0	(2,219,000)	0	(2,219,000)
Stock–based compensation	$ 0	428,000	0	0	0	428,000
Shares sold – options exercised (in shares)	21,906
Shares sold – options exercised	$ 0	1,067,000	0	0	0	1,067,000
Repurchase of common shares (in shares)	(14,506)
Repurchase of common shares	$ 0	(867,000)	0	0	0	(867,000)
Dividends declared to common stockholders	0	0	(7,305,000)	0	0	(7,305,000)
Reclassification due to new accounting standards at Dec. 31, 2017	$ 0	0	68,201,000	(68,201,000)	0	0
Balance (in shares) at Mar. 31, 2018	15,219,533
Balance at Mar. 31, 2018	$ 152,000	216,287,000	477,528,000	(2,916,000)	586,000	691,637,000
Balance (in shares) at Dec. 31, 2017	15,212,133
Balance at Dec. 31, 2017	$ 152,000	215,659,000	419,423,000	67,504,000	694,000	703,432,000
Net income attributable to National HealthCare Corporation						19,670,000
Net loss attributable to noncontrolling interest						(194,000)
Other comprehensive income (loss)						(2,858,000)
Reclassification due to new accounting standards at Dec. 31, 2017	$ 0	0	68,201,000	(68,201,000)	0	0
Balance (in shares) at Jun. 30, 2018	15,225,654
Balance at Jun. 30, 2018	$ 152,000	217,296,000	492,377,000	(3,555,000)	500,000	706,770,000
Balance (in shares) at Dec. 31, 2017	15,212,133
Balance at Dec. 31, 2017	$ 152,000	215,659,000	419,423,000	67,504,000	694,000	$ 703,432,000
Shares sold – options exercised (in shares)						68,291
Reclassification due to new accounting standards at Dec. 31, 2017	$ 0	0	68,201,000	(68,201,000)	0	$ 0
Balance (in shares) at Dec. 31, 2018	15,255,002
Balance at Dec. 31, 2018	$ 153,000	219,435,000	516,435,000	(2,745,000)	1,179,000	734,457,000
Balance (in shares) at Mar. 31, 2018	15,219,533
Balance at Mar. 31, 2018	$ 152,000	216,287,000	477,528,000	(2,916,000)	586,000	691,637,000
Net income attributable to National HealthCare Corporation	0	0	22,461,000	0	0	22,461,000
Net loss attributable to noncontrolling interest	0	0	0	0	(86,000)	(86,000)
Other comprehensive income (loss)	0	0	0	(639,000)	0	(639,000)
Stock–based compensation	$ 0	749,000	0	0	0	749,000
Shares sold – options exercised (in shares)	6,121
Shares sold – options exercised	$ 0	260,000	0	0	0	260,000
Dividends declared to common stockholders	$ 0	0	(7,612,000)	0	0	(7,612,000)
Balance (in shares) at Jun. 30, 2018	15,225,654
Balance at Jun. 30, 2018	$ 152,000	217,296,000	492,377,000	(3,555,000)	500,000	706,770,000
Balance (in shares) at Dec. 31, 2018	15,255,002
Balance at Dec. 31, 2018	$ 153,000	219,435,000	516,435,000	(2,745,000)	1,179,000	734,457,000
Net income attributable to National HealthCare Corporation	0	0	21,269,000	0	0	21,269,000
Net loss attributable to noncontrolling interest	0	0	0	0	(38,000)	(38,000)
Other comprehensive income (loss)	0	0	0	2,548,000	0	2,548,000
Stock–based compensation	$ 0	424,000	0	0	0	424,000
Shares sold – options exercised (in shares)	59,384
Shares sold – options exercised	$ 0	579,000	0	0	0	579,000
Repurchase of common shares (in shares)	(10,396)
Repurchase of common shares	$ 0	(872,000)	0	0	0	(872,000)
Dividends declared to common stockholders	$ 0	0	(7,652,000)	0	0	(7,652,000)
Balance (in shares) at Mar. 31, 2019	15,303,990
Balance at Mar. 31, 2019	$ 153,000	219,566,000	530,052,000	(197,000)	1,141,000	750,715,000
Balance (in shares) at Dec. 31, 2018	15,255,002
Balance at Dec. 31, 2018	$ 153,000	219,435,000	516,435,000	(2,745,000)	1,179,000	734,457,000
Net income attributable to National HealthCare Corporation						34,980,000
Net loss attributable to noncontrolling interest						(67,000)
Other comprehensive income (loss)						$ 4,893,000
Shares sold – options exercised (in shares)						332,852
Balance (in shares) at Jun. 30, 2019	15,318,790
Balance at Jun. 30, 2019	$ 153,000	221,054,000	535,797,000	2,148,000	1,095,000	$ 760,247,000
Balance (in shares) at Mar. 31, 2019	15,303,990
Balance at Mar. 31, 2019	$ 153,000	219,566,000	530,052,000	(197,000)	1,141,000	750,715,000
Net income attributable to National HealthCare Corporation	0	0	13,711,000	0	0	13,711,000
Net loss attributable to noncontrolling interest	0	0	0	0	(29,000)	(29,000)
Other comprehensive income (loss)	0	0	0	2,345,000	0	2,345,000
Stock–based compensation	$ 0	684,000	0	0	0	684,000
Shares sold – options exercised (in shares)	14,800
Shares sold – options exercised	$ 0	804,000	0	0	0	804,000
Dividends declared to common stockholders	0	0	(7,966,000)	0	0	(7,966,000)
Distributions attributable to noncontrolling interest	$ 0	0	0	0	(17,000)	(17,000)
Balance (in shares) at Jun. 30, 2019	15,318,790
Balance at Jun. 30, 2019	$ 153,000	$ 221,054,000	$ 535,797,000	$ 2,148,000	$ 1,095,000	$ 760,247,000