Note 1 - Description of Business (Details Textual)	Mar. 31, 2020
Number of Skilled Nursing Centers	75
Number of Beds	9,513
Number of Assisted Living Facilities	25
Number of Independent Living Facilities	5
Number of Geriatric Psychiatric Hospitals	1
Number of Homecare Programs	35
Number of States in which Entity Operates	10

Number of assisted living facilities in which company operates as of the Balance Sheet date.

No definition available.

Name:	nhc_NumberOfAssistedLivingFacilities
Namespace Prefix:	nhc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Number of licensed skilled nursing beds that are operated or managed as of the balance sheet date.

No definition available.

The number of geriatric psychiatric hospitals.

No definition available.

Name:	nhc_NumberOfGeriatricPsychiatricHospitals
Namespace Prefix:	nhc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Number of homecare Programs in which the company operates as of the Balance Sheet date.

No definition available.

Name:	nhc_NumberOfHomecarePrograms
Namespace Prefix:	nhc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Number of independent living facilities in which the company operates as of the Balance Sheet date.

No definition available.

Name:	nhc_NumberOfIndependentLivingFacilities
Namespace Prefix:	nhc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Number of skilled nursing centers operated or managed as of the balance sheet date.

No definition available.

Name:	nhc_NumberOfSkilledNursingCenters
Namespace Prefix:	nhc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of states the entity operates in as of the balance sheet date.

No definition available.

Name:	us-gaap_NumberOfStatesInWhichEntityOperates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant