Segment Information (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) segment	Sep. 30, 2019 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment			2
Geographical revenues
Revenues	$ 88,544	$ 85,776	$ 245,258	$ 257,991
Operating (loss) income	(5,250)	8,517	(3,670)	39,223
Interest expense	2,808	2,356	6,668	11,491
Loss on extinguishment of debt	0	0	0	3,196
Other (income) loss	(596)	804	(1,702)	(1,695)
(Loss) income before income taxes	(7,462)	5,357	(8,636)	26,231
DEFINITY
Geographical revenues
Revenues	55,429	52,395	152,585	158,135
TechneLite
Geographical revenues
Revenues	21,489	21,747	63,496	65,998
Other nuclear
Geographical revenues
Revenues	17,167	15,541	42,944	45,907
Rebates and allowances
Geographical revenues
Revenues	(5,541)	(3,907)	(13,767)	(12,049)
U.S.
Geographical revenues
Revenues	77,475	74,650	213,619	225,274
Operating (loss) income	(6,621)	6,389	(7,634)	33,662
U.S. | DEFINITY
Geographical revenues
Revenues	53,792	50,917	148,346	154,099
U.S. | TechneLite
Geographical revenues
Revenues	17,652	18,281	52,599	55,204
U.S. | Other nuclear
Geographical revenues
Revenues	11,571	9,355	26,437	28,006
U.S. | Rebates and allowances
Geographical revenues
Revenues	(5,540)	(3,903)	(13,763)	(12,035)
International
Geographical revenues
Revenues	11,069	11,126	31,639	32,717
Operating (loss) income	1,371	2,128	3,964	5,561
International | DEFINITY
Geographical revenues
Revenues	1,637	1,478	4,239	4,036
International | TechneLite
Geographical revenues
Revenues	3,837	3,466	10,897	10,794
International | Other nuclear
Geographical revenues
Revenues	5,596	6,186	16,507	17,901
International | Rebates and allowances
Geographical revenues
Revenues	$ (1)	$ (4)	$ (4)	$ (14)