Inventory (Details) - USD ($)	Dec. 31, 2020	Mar. 31, 2020
Inventory [Abstract]
Raw materials	$ 123,423,000	$ 99,360,000
Work-in-process	9,391,000	3,906,000
Finished goods	164,020,000	135,601,000
Inventory, gross	296,834,000	238,867,000
Less allowance for excess and obsolete inventory	(13,303,000)	(13,208,000)
Inventory - net	283,531,000	225,659,000
Inventory unreturned	12,750,000	9,021,000
Total inventory	$ 296,281,000	$ 234,680,000