Investments in Unconsolidated Entities, Boca Oncology Partners (Details)	1 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011 USD ($)	Dec. 31, 2021 USD ($) ft²	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Boca Oncology Partners [Abstract]
Investments in unconsolidated entities			$ 141,000	$ 160,000
Condensed Income Statement Information [Abstract]
Rental income				7,000
Net (loss) income			(674,000)	533,000
USNC's equity in (loss) income			(470,000)	(809,000)
Condensed Balance Sheet Information [Abstract]
Current assets			2,243,000	3,007,000
Total assets			3,688,000	4,173,000
Current liabilities			327,000	410,000
Equity			3,327,000	3,686,000	$ 3,153,000
Total liabilities and equity			$ 3,688,000	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			22.50%
Investments in unconsolidated entities			$ 151,000	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 (loss) income			85,000	63,000
USNC's equity in (loss) income			17,000	13,000
Condensed Balance Sheet Information [Abstract]
Current assets			112,000	27,000
Noncurrent assets			757,000	757,000
Total assets			869,000	784,000
Current liabilities			0	0
Noncurrent liabilities			0	0
Equity			869,000	784,000
Total liabilities and equity			$ 869,000	$ 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%