The Southern California Regional Gamma Knife Center (Details) - USD ($)	1 Months Ended	3 Months Ended
	Feb. 29, 2016	Mar. 31, 2016	Mar. 31, 2015	Apr. 01, 2016	Dec. 31, 2015	Nov. 01, 2014
Schedule of Equity Method Investments [Line Items]
Renovation installation and operation agreement period		14 years
First payment due						$ 12,000
Neuro Partners, LLC and CGK Condensed Income Statement Information [Abstract]
Patient revenue		$ 832,000	$ 809,000
USNC's equity in earnings (loss) of Neuro Partners, LLC and CGK		$ 155,000	(36,000)
CGK [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage		39.00%
Neuro Partners LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage		20.00%
Share of guarantee in lease obligations	20.00%	20.00%
Lease term	5 years	7 years
Debt maturity period	60 months
Prior year lease obligations	$ 668,000
Operating lease payable	$ 1,663,000
Subsequent Event [Member] | Neuro Partners LLC [Member]
Schedule of Equity Method Investments [Line Items]
First payment due				$ 31,000
Neuro Partners LLC and CGK [Member]
Schedule of Equity Method Investments [Line Items]
Losses against outstanding receivables		$ 1,000
Neuro Partners, LLC and CGK Condensed Income Statement Information [Abstract]
Patient revenue		305,000	203,000
Net income (loss)		123,000	(70,000)
USNC's equity in earnings (loss) of Neuro Partners, LLC and CGK		18,000	$ (33,000)
Neuro Partners, LLC and CGK Condensed Balance Sheet Information [Abstract]
Current assets		68,000			$ 66,000
Noncurrent assets		1,028,000			394,000
Total assets		1,096,000			460,000
Current liabilities		209,000			1,359,000
Noncurrent liabilities		1,663,000			0
Equity		(776,000)			(899,000)
Total liabilities and equity		$ 1,096,000			$ 460,000