Inventories (Details) - USD ($)	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Inventory Disclosure [Abstract]
Inventory Write-down	$ 0	$ 0
Raw materials	84,492,000	74,716,000
Work-in-process	43,140,000	39,117,000
Finished goods	40,321,000	33,666,000
Inventory, Gross	167,953,000	147,499,000
LIFO cost less than FIFO cost	(15,067,000)	(16,856,000)
Net inventories	$ 152,886,000	$ 130,643,000