Inventory (Details) - USD ($)	Jun. 30, 2015	Mar. 31, 2015
Non-core inventory [Abstract]
Raw materials	$ 18,781,000	$ 18,836,000
Work-in-process	392,000	255,000
Finished goods	41,342,000	39,828,000
Non-core inventory, gross	60,515,000	58,919,000
Less allowance for excess and obsolete inventory	(2,330,000)	(2,090,000)
Total	58,185,000	56,829,000
Inventory unreturned	8,442,000	7,833,000
Long-term core inventory [Abstract]
Used cores held at the Company's facilities	34,712,000	27,417,000
Used cores expected to be returned by customers	7,887,000	9,799,000
Remanufactured cores held in finished goods	23,949,000	21,557,000
Remanufactured cores held at customers' locations	136,205,000	130,762,000
Long-term core inventory - gross	202,753,000	189,535,000
Less allowance for excess and obsolete inventory	(751,000)	(585,000)
Total	202,002,000	188,950,000
Long-term core inventory deposits	$ 32,567,000	$ 31,571,000