Boca Oncology Partners (Details)	1 Months Ended		3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011 USD ($)	Mar. 31, 2021 USD ($) ft²	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Boca Oncology Partners [Abstract]
Recorded investments			$ 161,000		$ 160,000
Condensed Income Statement Information [Abstract]
Rental Income				$ 2,000
USNC's equity in (loss) earnings			(139,000)	(146,000)
Condensed Balance Sheet Information [Abstract]
Current assets			3,451,000		3,007,000
TOTAL ASSETS			4,614,000		4,173,000
Current liabilities			322,000		410,000
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY			$ 4,614,000		$ 4,173,000
USNC [Member] | Boca West IMP [Member]
Boca Oncology Partners [Abstract]
Share of guarantee in mortgage			10.00%
Share of guarantee in outstanding mortgage			50.00%
Mortgage term of guarantee			10 years
Original balance of mortgage			$ 3,000,000
Boca Oncology Partners, LLC [Member]
Boca Oncology Partners [Abstract]
Area of real estate property (in square foot) | ft²			6,000
Boca Oncology Partners RE, LLC ("BOPRE") [Member]
Boca Oncology Partners [Abstract]
Ownership percentage			21.22%		21.22%
Recorded investments			$ 137,000		$ 134,000
Boca Oncology Partners RE, LLC ("BOPRE") [Member] | Boca West IMP [Member]
Boca Oncology Partners [Abstract]
Percentage of interest in medical office building		20.00%
Ownership percentage	23.75%
Additional investor purchased ownership percentage	3.75%
Boca Oncology Partners RE, LLC ("BOPRE") [Member] | Investment in Unconsolidated Entity [Member]
Condensed Income Statement Information [Abstract]
Rental Income			0	0
Net income			18,000	7,000
USNC's equity in (loss) earnings			3,000	$ 1,000
Condensed Balance Sheet Information [Abstract]
Current assets			45,000		27,000
Noncurrent assets			757,000		757,000
TOTAL ASSETS			802,000		784,000
Current liabilities			0		0
Noncurrent liabilities			0		0
Equity			802,000		784,000
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY			$ 802,000		$ 784,000
BOP and BOPRE [Member]
Boca Oncology Partners [Abstract]
Area of real estate property (in square foot) | ft²			32,000
Investments in unconsolidated entities		$ 225,000
Ownership percentage		22.50%