Inventory (Details) - USD ($)	Jun. 30, 2016	Mar. 31, 2016
Non-core inventory [Abstract]
Raw materials	$ 21,192,000	$ 17,394,000
Work-in-process	595,000	135,000
Finished goods	54,140,000	42,982,000
Non-core inventory, gross	75,927,000	60,511,000
Less allowance for excess and obsolete inventory	(2,586,000)	(2,451,000)
Total	73,341,000	58,060,000
Inventory unreturned	10,399,000	10,520,000
Long-term core inventory [Abstract]
Used cores held at the Company's facilities	32,000,000	34,405,000
Used cores expected to be returned by customers	11,435,000	10,781,000
Remanufactured cores held in finished goods	31,295,000	24,489,000
Remanufactured cores held at customers' locations	170,287,000	172,600,000
Long-term core inventory - gross	245,017,000	242,275,000
Less allowance for excess and obsolete inventory	(1,195,000)	(1,175,000)
Total	243,822,000	241,100,000
Long-term core inventory deposits	$ 5,569,000	$ 5,569,000