Investment in Unconsolidated Entities, Boca Oncology Partners (Details)	1 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011 USD ($)	Dec. 31, 2018 USD ($) ft²	Dec. 31, 2017 USD ($)
Boca Oncology Partners [Abstract]
Recorded investments			$ 168,000	$ 164,000
Condensed Income Statement Information [Abstract]
USNC's equity in (loss) earnings			$ (743,000)	(101,000)
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
Outstanding balance on mortgage			$ 2,303,000	$ 2,417,000
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%	21.05%
Recorded investments			$ 168,000	$ 164,000
Condensed Income Statement Information [Abstract]
Rental income			0	0
Net loss			(4,000)	(7,000)
USNC's equity in (loss) earnings			(1,000)	(1,000)
Condensed Balance Sheet Information [Abstract]
Current assets			18,000	17,000
Noncurrent assets			935,000	920,000
Total assets			953,000	937,000
Current liabilities			0	0
Noncurrent liabilities			0	0
Equity			953,000	937,000
Total liabilities and equity (deficit)			$ 953,000	$ 937,000
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%
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%