Investment in Unconsolidated Entities, Florida Oncology Partners (Details)	1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) Term	Dec. 31, 2017 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2011 USD ($)	Nov. 30, 2017 USD ($)	Sep. 22, 2017 USD ($)
Florida Oncology Partners [Abstract]
Outstanding lease obligation	$ 200,000		$ 200,000
Investments in unconsolidated entities	168,000	$ 164,000	168,000	$ 164,000
Recorded distribution			60,000	274,000
Due from related parties	$ 1,141,000	169,000	1,141,000	169,000
Condensed Income Statement Information [Abstract]
Patient revenue			3,424,000	3,414,000
USNC's equity in (loss) income			$ (743,000)	(101,000)
FOP [Member]
Florida Oncology Partners [Abstract]
Lease term			7 years
Capital lease obligation						$ 5,800,000
Percentage of guarantee obligations						25.00%
Outstanding lease obligation		468,000		468,000
Down payment of capital leases					$ 1,000,000
Monthly payments for capital leases					$ 172,000
Common stock awarded as a part of bankruptcy proceedings (in shares) | shares	10,820
Investments in unconsolidated entities	$ 0	132,000	$ 0	132,000
Recorded distribution		950,000	0
Due from related parties	$ 223,000	169,000	$ 223,000	169,000
Note bearing interest	6.00%		6.00%
Outstanding amount	$ 735,000	299,000	$ 735,000	299,000
Accrued interest			30,000	2,000
Allowance for note receivable	218,000		218,000
Reduced carrying value of note	517,000		517,000
Condensed Income Statement Information [Abstract]
Patient revenue			2,953,000	678,000
Rental income			1,252,000	2,517,000
Net (loss) income			(1,918,000)	525,000
USNC's equity in (loss) income			(465,000)	132,000
Condensed Balance Sheet Information [Abstract]
Current assets	401,000	664,000	401,000	664,000
Noncurrent assets	16,570,000	18,961,000	16,570,000	18,961,000
Total assets	16,971,000	19,625,000	16,971,000	19,625,000
Current liabilities	3,974,000	3,228,000	3,974,000	3,228,000
Noncurrent liabilities	15,360,000	16,842,000	15,360,000	16,842,000
Equity	(2,363,000)	(445,000)	(2,363,000)	(445,000)
Total liabilities and equity (deficit)	16,971,000	19,625,000	$ 16,971,000	19,625,000
FOP [Member] | Maximum [Member]
Florida Oncology Partners [Abstract]
Amount of guarantee obligation						$ 1,433,000
FOP [Member] | Office Space [Member]
Florida Oncology Partners [Abstract]
Lease term			10 years
Loan amount							$ 4,106,000
Outstanding Loan	3,660,000	4,100,000	$ 3,660,000	4,100,000
Debt maturity period			7 years
FOP [Member] | Radiation Therapy Center [Member]
Florida Oncology Partners [Abstract]
Lease term			10 years
Capital lease obligation								$ 14,321,000
Loan amount	436,000		$ 436,000
Monthly payments for capital leases	163,200	$ 160,000	$ 163,200	$ 160,000
Maximum number of additional terms extended | Term			3
Extension of agreement			5 years
Percentage of increase of monthly payments each year			2.00%
FOP [Member] | Letter of Credit [Member] | Office Space [Member]
Florida Oncology Partners [Abstract]
Letter of credit, amount	$ 88,000		$ 88,000
FOP [Member] | USNC [Member]
Florida Oncology Partners [Abstract]
Ownership percentage	24.00%		24.00%