Florida Oncology Partners (Details)	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2018 USD ($) shares	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) Term	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2017 USD ($)	Nov. 30, 2017 USD ($)	Sep. 22, 2017 USD ($)
Florida Oncology Partners [Abstract]
Due from related parties	$ 1,141,000	$ 0		$ 0		$ 1,141,000
Lease obligations		179,000		179,000
Condensed Income Statement Information [Abstract]
Patient revenue		825,000	$ 1,121,000	1,666,000	$ 1,986,000
USNC's equity in (loss) earnings of FOP		(513,000)	(160,000)	$ (746,000)	(190,000)
FOP and FOPRE [Member]
Florida Oncology Partners [Abstract]
Down payment of capital leases							$ 1,000,000
Monthly payments for capital leases							$ 172,000
FOP [Member]
Florida Oncology Partners [Abstract]
Lease term				7 years
Capital lease obligation								$ 5,800,000
Percentage of guarantee obligations								25.00%
Common stock awarded as a part of bankruptcy proceedings (in shares) | shares	10,820
Due from related parties	$ 223,000	120,000		$ 120,000		223,000
Lease obligations		17,600,000		17,600,000
Outstanding amount	735,000	$ 600,000		600,000		735,000
Accrued interest				$ 53,000		30,000
Note bearing interest		6.00%		6.00%
Allowance for note receivable	218,000	$ 523,000		$ 523,000		218,000
Reduced carrying value of note	517,000	77,000		77,000		517,000
Increase in allowance				305,000
Condensed Income Statement Information [Abstract]
Patient revenue		891,000	1,706,000	1,922,000	2,306,000
Rental income		181,000	408,000	362,000	890,000
Net (loss) income		(409,000)	577,000	(591,000)	109,000
USNC's equity in (loss) earnings of FOP		(99,000)	139,000	(143,000)	26,000
Condensed Balance Sheet Information [Abstract]
Current assets	401,000	586,000		586,000		401,000
Noncurrent assets	16,570,000	3,835,000		3,835,000		16,570,000
Total assets	16,971,000	4,421,000		4,421,000		16,971,000
Current liabilities	3,974,000	4,530,000		4,530,000		3,974,000
Noncurrent liabilities	15,360,000	2,840,000		2,840,000		15,360,000
Deficit	(2,363,000)	(2,949,000)		(2,949,000)		(2,363,000)
Total liabilities and equity (deficit)	$ 16,971,000	4,421,000		$ 4,421,000		$ 16,971,000
FOP [Member] | Maximum [Member]
Florida Oncology Partners [Abstract]
Amount of guarantee obligations								$ 1,433,000
FOP [Member] | Office Space [Member]
Florida Oncology Partners [Abstract]
Lease term				10 years
Loan amount										$ 4,106,000
Outstanding Loan		3,394,000	$ 3,919,000	$ 3,394,000	$ 3,919,000
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
Monthly payments for capital leases		163,200		$ 163,200					$ 160,000
Percentage of increase of monthly payments each year				2.00%
Maximum number of additional terms extended | Term				3
Extension of agreement				5 years
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%