Segment Information - Schedule of Selected Information for Each Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 89,346	$ 85,776	$ 85,705	$ 86,510	$ 86,271	$ 88,900	$ 85,573	$ 82,630	$ 347,337	$ 343,374	$ 331,378
Operating income
Operating income									51,661	64,488	51,853
Interest expense									13,617	17,405	18,410
Loss on extinguishment of debt									3,196	0	2,442
Other expense (income)									(6,221)	2,465	8,638
Income before income taxes									28,627	49,548	39,639
Total depreciation and amortization									12,087	12,769	18,189
Total long-lived assets	116,497				107,888				116,497	107,888
U.S.
Operating income
Total long-lived assets	115,560				106,755				115,560	106,755
International
Operating income
Total long-lived assets	$ 937				$ 1,133				937	1,133
U.S.
Segment Reporting Information [Line Items]
Total revenues									303,989	288,580	290,002
Operating income
Operating income									44,275	56,327	49,239
Total depreciation and amortization									11,673	12,278	17,672
U.S. | DEFINITY
Segment Reporting Information [Line Items]
Total revenues									211,777	178,440	153,581
U.S. | TechneLite
Segment Reporting Information [Line Items]
Total revenues									72,534	74,042	90,489
U.S. | Other nuclear
Segment Reporting Information [Line Items]
Total revenues									36,231	48,935	54,822
U.S. | Rebates and allowances
Segment Reporting Information [Line Items]
Total revenues									(16,553)	(12,837)	(8,890)
International
Segment Reporting Information [Line Items]
Total revenues									43,348	54,794	41,376
Operating income
Operating income									7,386	8,161	2,614
Total depreciation and amortization									414	491	517
International | DEFINITY
Segment Reporting Information [Line Items]
Total revenues									5,731	4,633	3,687
International | TechneLite
Segment Reporting Information [Line Items]
Total revenues									14,058	24,816	14,155
International | Other nuclear
Segment Reporting Information [Line Items]
Total revenues									23,574	25,349	23,558
International | Rebates and allowances
Segment Reporting Information [Line Items]
Total revenues									(15)	(4)	(24)
Worldwide
Segment Reporting Information [Line Items]
Total revenues									347,337	343,374	331,378
Worldwide | DEFINITY
Segment Reporting Information [Line Items]
Total revenues									217,508	183,073	157,268
Worldwide | TechneLite
Segment Reporting Information [Line Items]
Total revenues									86,592	98,858	104,644
Worldwide | Other nuclear
Segment Reporting Information [Line Items]
Total revenues									59,805	74,284	78,380
Worldwide | Rebates and allowances
Segment Reporting Information [Line Items]
Total revenues									$ (16,568)	$ (12,841)	$ (8,914)