Basis of Financial Statement Presentation - Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Raw materials and supplies	$ 95,023	$ 88,408
Work in process	68,464	65,417
Finished goods	86,556	66,907
Subtotal	250,043	220,732
Inventory reserves	(16,706)	(16,346)
Inventories, net	$ 233,337	$ 204,386