Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	May 31, 2020	Feb. 29, 2020	Nov. 30, 2019	Aug. 31, 2019	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2020	May 31, 2019	May 31, 2018
Disaggregation of Revenue [Line Items]
Net sales	$ 58,332	$ 69,780	$ 70,003	$ 66,042	$ 71,182	$ 65,524	$ 69,985	$ 63,943	$ 264,157	$ 270,634	$ 261,655
United States
Disaggregation of Revenue [Line Items]
Net sales									207,980	216,957	$ 213,727
International
Disaggregation of Revenue [Line Items]
Net sales									56,177	53,677
Vascular Interventions & Therapies
Disaggregation of Revenue [Line Items]
Net sales									112,706	119,901
Vascular Interventions & Therapies | United States
Disaggregation of Revenue [Line Items]
Net sales									98,965	106,767
Vascular Interventions & Therapies | International
Disaggregation of Revenue [Line Items]
Net sales									13,741	13,134
Vascular Access
Disaggregation of Revenue [Line Items]
Net sales									94,299	94,730
Vascular Access | United States
Disaggregation of Revenue [Line Items]
Net sales									76,768	79,611
Vascular Access | International
Disaggregation of Revenue [Line Items]
Net sales									17,531	15,119
Oncology
Disaggregation of Revenue [Line Items]
Net sales									57,152	56,003
Oncology | United States
Disaggregation of Revenue [Line Items]
Net sales									32,247	30,579
Oncology | International
Disaggregation of Revenue [Line Items]
Net sales									$ 24,905	$ 25,424