Summary of Significant Accounting Policies - Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 165,020	$ 160,577	$ 157,312
Less - Accumulated depreciation and amortization	(114,538)	(109,657)	(107,655)
Net property, plant and equipment	50,482	50,920	49,657
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment	5,738	5,738	6,372
Buildings, leasehold interests and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment	40,125	40,893	42,345
Machinery, equipment and other
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 119,157	$ 113,946	$ 108,595