Components of Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Mar. 31, 2018
Property Plant And Equipment [Abstract]
Land	$ 7,408	$ 7,680
Building and building improvements	83,404	63,700
Leasehold improvements	2,180	2,905
Machinery and equipment	50,123	42,787
Furniture and fixtures	9,804	8,104
Construction in progress	14,026	19,850
Total cost	166,945	145,026
Less accumulated depreciation	(32,880)	(27,859)
Property and equipment, net	$ 134,065	$ 117,167