Note 4 - Acquisition of Caris HealthCare, L.P. - Pro Forma Financial Information (Details) - Acquisition of Caris [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net patient revenues	$ 254,817	$ 243,357	$ 736,619	$ 744,762
Total costs and expenses	263,975	256,385	770,295	770,338
Income from operations	12,762	10,215	48,544	45,667
Non-operating income	3,399	3,500	10,374	10,670
Income (loss) before income taxes	(7,636)	14,406	35,691	17,465
Net income (loss) attributable to NHC	$ (3,348)	$ 13,698	$ 29,002	$ 15,589