Inventory (Details) (USD $)	Mar. 31, 2013	Mar. 31, 2012
Non-core inventory [Abstract]
Raw materials	$ 29,246,000	$ 31,560,000
Work-in-process	626,000	153,000
Finished goods	47,676,000	72,171,000
Non-core inventory, gross	77,548,000	103,884,000
Less allowance for excess and obsolete inventory	(24,993,000)	(11,308,000)
Total	61,090,000	95,071,000
Inventory unreturned	12,150,000	9,819,000
Long-term core inventory [Abstract]
Used cores held at the Company's facilities	40,778,000	47,206,000
Used cores expected to be returned by customers	5,147,000	5,542,000
Remanufactured cores held in finished goods	22,170,000	25,751,000
Remanufactured cores held at customers' locations	98,916,000	118,402,000
Long-term core inventory - gross	167,011,000	196,901,000
Less allowance for excess and obsolete inventory	(8,535,000)	(2,495,000)
Total	158,476,000	194,406,000
Long-term core inventory deposit	$ 27,610,000	$ 26,939,000