The Southern California Regional Gamma Knife Center (Details)		3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 01, 2016 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) Payment	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Feb. 29, 2016 USD ($)
The Southern California Regional Gamma Knife Center [Abstract]
Renovation installation and operation agreement period				14 years
Lease obligation		$ 176,000		$ 176,000
Lease payment				814,000	$ 1,034,000
Distributed earnings				63,000	0
Condensed Income Statement Information [Abstract]
Patient revenue		662,000	$ 658,000	2,005,000	2,324,000
USNC's equity in earnings (loss)		(56,000)	(135,000)	(292,000)	(799,000)
Condensed Balance Sheet Information [Abstract]
Current assets		2,699,000		2,699,000		$ 2,681,000
Total assets		4,415,000		4,415,000		4,997,000
Current liabilities		790,000		790,000		1,638,000
Total liabilities and equity		4,415,000		4,415,000		4,997,000
Neuro Partners LLC and CGK [Member]
The Southern California Regional Gamma Knife Center [Abstract]
Recorded amount of equity method income				134,000		0
Neuro Partners LLC and CGK [Member] | Investment in Unconsolidated Entity [Member]
Condensed Income Statement Information [Abstract]
Patient revenue		274,000	278,000	944,000	767,000
Net income (loss)		70,000	107,000	402,000	254,000
USNC's equity in earnings (loss)		23,000	$ 35,000	134,000	$ 80,000
Condensed Balance Sheet Information [Abstract]
Current assets		534,000		534,000		163,000
Noncurrent assets		615,000		615,000		807,000
Total assets		1,149,000		1,149,000		970,000
Current liabilities		750,000		750,000		380,000
Noncurrent liabilities		0		0		593,000
Equity (deficit)		399,000		399,000		(3,000)
Total liabilities and equity		$ 1,149,000		$ 1,149,000		970,000
Neuro Partners LLC [Member]
The Southern California Regional Gamma Knife Center [Abstract]
Ownership percentage		20.00%		20.00%
Neuro Partners LLC [Member] | Lease One [Member]
The Southern California Regional Gamma Knife Center [Abstract]
Share of guarantee in lease obligations				20.00%
Lease term		7 years		7 years
Lease obligation							$ 668,000
Neuro Partners LLC [Member] | Lease Two [Member]
The Southern California Regional Gamma Knife Center [Abstract]
Lease term		5 years		5 years
Lease obligation							$ 1,663,000
Number of lease payments | Payment				60
Lease payment	$ 31,000
CGK [Member]
The Southern California Regional Gamma Knife Center [Abstract]
Ownership percentage		39.00%		39.00%
Due from related parties		$ 8,000		$ 8,000		23,000
Distributions receivable						$ 20,000
Distributed earnings				$ 20,000