Other Financial Statements Details Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Mar. 31, 2017
Accounts Receivable, Net [Abstract]
Inventory, Raw Materials, Net of Reserves	$ 19,746	$ 14,430
Inventory, Work in Process, Net of Reserves	296,941	268,281
Inventory, Finished Goods, Net of Reserves	140,252	134,491
Total inventories	$ 456,939	$ 417,202