Segment Information - Schedule of Selected Information for Each Business Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 339,410	$ 347,337	$ 343,374
Operating income
Total operating (loss) income	(4,198)	51,661	64,488
Interest expense	9,479	13,617	17,405
Loss on extinguishment of debt	0	3,196	0
Other (income) loss	(2,198)	6,221	(2,465)
(Loss) income before income taxes	(11,479)	28,627	49,548
Depreciation and amortization
Depreciation and amortization	23,251	12,087	12,769
Long-lived assets	120,171	116,497
DEFINITY
Segment Reporting Information [Line Items]
Revenues	213,316	217,508	183,073
TechneLite
Segment Reporting Information [Line Items]
Revenues	86,241	86,592	98,858
Other nuclear
Segment Reporting Information [Line Items]
Revenues	58,924	59,805	74,284
Rebates and allowances
Segment Reporting Information [Line Items]
Revenues	(19,071)	(16,568)	(12,841)
U.S.
Segment Reporting Information [Line Items]
Revenues	294,796	303,989	288,580
Operating income
Total operating (loss) income	(10,363)	44,275	56,327
Depreciation and amortization
Depreciation and amortization	23,007	11,673	12,278
Long-lived assets	120,147	115,560
U.S. | DEFINITY
Segment Reporting Information [Line Items]
Revenues	207,270	211,777	178,440
U.S. | TechneLite
Segment Reporting Information [Line Items]
Revenues	69,729	72,534	74,042
U.S. | Other nuclear
Segment Reporting Information [Line Items]
Revenues	36,864	36,231	48,935
U.S. | Rebates and allowances
Segment Reporting Information [Line Items]
Revenues	(19,067)	(16,553)	(12,837)
International
Segment Reporting Information [Line Items]
Revenues	44,614	43,348	54,794
Operating income
Total operating (loss) income	6,165	7,386	8,161
Depreciation and amortization
Depreciation and amortization	244	414	491
Long-lived assets	24	937
International | DEFINITY
Segment Reporting Information [Line Items]
Revenues	6,046	5,731	4,633
International | TechneLite
Segment Reporting Information [Line Items]
Revenues	16,512	14,058	24,816
International | Other nuclear
Segment Reporting Information [Line Items]
Revenues	22,060	23,574	25,349
International | Rebates and allowances
Segment Reporting Information [Line Items]
Revenues	$ (4)	$ (15)	$ (4)