Segment Information - Schedule of Selected Information for Each Business Segment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 343,374	$ 331,378	$ 301,853
Operating income
Operating income	64,488	51,853	56,588
Interest expense	17,405	18,410	26,618
Debt retirement costs	0	0	1,896
Loss on extinguishment of debt	0	2,442	0
Other income	2,465	8,638	220
Income before income taxes	49,548	39,639	28,294
Depreciation and amortization	12,769	18,189	17,330
Long-lived assets	107,888	92,999
DEFINITY
Segment Reporting Information [Line Items]
Revenues	183,073	157,268	131,612
TechneLite
Segment Reporting Information [Line Items]
Revenues	98,858	104,644	99,217
Other
Segment Reporting Information [Line Items]
Revenues	61,443	69,466	71,024
U.S.
Segment Reporting Information [Line Items]
Revenues	288,580	290,002	257,420
All other
Segment Reporting Information [Line Items]
Revenues	54,794	41,376	44,433
U.S.
Segment Reporting Information [Line Items]
Revenues	288,580	290,002	257,420
Operating income
Operating income	56,327	49,239	46,909
Depreciation and amortization	12,278	17,672	15,995
Long-lived assets	106,755	91,537
International
Segment Reporting Information [Line Items]
Revenues	54,794	41,376	44,433
Operating income
Operating income	8,161	2,614	9,679
Depreciation and amortization	491	517	$ 1,335
Long-lived assets	$ 1,133	$ 1,462