Consolidated Statements of Operations - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Net patient revenues									$ 947,872,000	$ 932,774,000	$ 916,742,000
Other revenues									48,511,000	47,575,000	47,153,000
Net operating revenues	$ 253,880,000	$ 247,067,000	$ 247,151,000	$ 248,285,000	$ 248,920,000	$ 246,326,000	$ 242,142,000	$ 242,961,000	996,383,000	980,349,000	963,895,000
Costs and Expenses:
Salaries, wages and benefits									592,831,000	582,721,000	572,043,000
Other operating									268,442,000	254,038,000	249,833,000
Facility rent									40,518,000	40,923,000	40,367,000
Depreciation and amortization									42,419,000	41,894,000	42,652,000
Interest									3,135,000	4,697,000	4,890,000
Total costs and expenses									947,345,000	924,273,000	909,785,000
Income from operations	16,497,000	6,568,000	10,189,000	15,784,000	17,194,000	10,834,000	12,165,000	15,883,000	49,038,000	56,076,000	54,110,000
Other income:
Non-operating income									26,747,000	17,670,000	20,439,000
Unrealized gains on marketable equity securities	$ (3,866,000)	$ 9,312,000	$ (54,000)	$ 6,838,000	$ 721,000	$ 3,486,000	$ 12,448,000	$ (15,517,000)	12,230,000	1,138,000	0
Income before income taxes									88,015,000	74,884,000	74,549,000
Income tax provision									(20,039,000)	(16,185,000)	(18,867,000)
Net income									67,976,000	58,699,000	55,682,000
Net loss attributable to noncontrolling interest									235,000	265,000	523,000
Net income attributable to National HealthCare Corporation									$ 68,211,000	$ 58,964,000	$ 56,205,000
Earnings per share attributable to National HealthCare Corporation stockholders:
Basic (in dollars per share)	$ 0.91	$ 1.27	$ 90	$ 1.39	$ 1.19	$ 1.39	$ 1.47	$ (0.18)	$ 4.47	$ 3.87	$ 3.70
Diluted (in dollars per share)	$ 0.89	$ 1.27	$ 89	$ 1.39	$ 1.19	$ 1.39	$ 1.47	$ (0.18)	$ 4.44	$ 3.87	$ 3.69
Weighted average common shares outstanding:
Basic (in shares)									15,270,154	15,224,886	15,189,920
Diluted (in shares)									15,360,046	15,236,826	15,218,962
Dividends declared per common share (in dollars per share)									$ 2.06	$ 1.98	$ 1.89