Supplemental Balance Sheets and Statements of Operations - Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Mar. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 1,469,491	$ 1,375,731
Accumulated depreciation	(916,855)	(880,451)
Property, plant and equipment	552,636	495,280
Land and land improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	56,340	62,232
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	210,192	199,319
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	977,806	916,737
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	109,770	82,306
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	104,842	105,857
Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 10,541	$ 9,280