Consolidated Statements of Operations - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Net patient revenues									$ 932,774,000	$ 916,742,000	$ 877,666,000
Other revenues									47,575,000	47,153,000	45,914,000
Net operating revenues	$ 248,920,000	$ 246,326,000	$ 242,142,000	$ 242,961,000	$ 246,311,000	$ 241,196,000	$ 238,695,000	$ 238,538,000	980,349,000	963,895,000	923,580,000
Costs and Expenses:
Salaries, wages and benefits									582,721,000	572,043,000	548,007,000
Other operating									254,038,000	249,833,000	230,775,000
Facility rent									40,923,000	40,367,000	41,292,000
Depreciation and amortization									41,894,000	42,652,000	39,023,000
Interest									4,697,000	4,890,000	3,941,000
Total costs and expenses									924,273,000	909,785,000	863,038,000
Income from operations	17,194,000	10,834,000	12,165,000	15,883,000	$ 16,323,000	$ 9,785,000	$ 12,138,000	$ 15,864,000	56,076,000	54,110,000	60,542,000
Other income:
Non-operating income									17,670,000	20,439,000	19,665,000
Unrealized gains on marketable securities	$ 721,000	$ 3,486,000	$ 12,448,000	$ (15,517,000)					1,138,000
Income before income taxes									74,884,000	74,549,000	80,207,000
Income tax provision									(16,185,000)	(18,867,000)	(29,669,000)
Net income									58,699,000	55,682,000	50,538,000
Net loss attributable to noncontrolling interest									265,000	523,000
Net income attributable to common stockholders of National HealthCare Corporation									$ 58,964,000	$ 56,205,000	$ 50,538,000
Earnings per share attributable to National HealthCare Corporation stockholders:
Basic (in dollars per share)	$ 1.19	$ 1.39	$ 1.48	$ (0.18)	$ 1.41	$ 0.75	$ 0.70	$ 0.84	$ 3.87	$ 3.70	$ 3.34
Diluted (in dollars per share)	$ 1.19	$ 1.39	$ 1.47	$ (0.18)	$ 1.41	$ 0.75	$ 0.70	$ 0.84	$ 3.87	$ 3.69	$ 3.32
Weighted average common shares outstanding:
Basic (in shares)									15,224,886	15,189,920	15,134,518
Diluted (in shares)									15,236,826	15,218,962	15,206,997
Dividends declared per common share (in dollars per share)									$ 1.98	$ 1.89	$ 1.75