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Business Segment And Geographic Information (Narrative) (Details) (USD $) | 12 Months Ended
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Mar. 31, 2012 | Mar. 31, 2011 | Mar. 31, 2010
Segment Reporting Information [Line Items] |  |  |
Number of reportable business segments | 2 |  |
Stock-based compensation expense | $ 9,864,000 | $ 13,412,000 | $ 13,494,000
Write-off of Advanced Payment to The Switch | 20,551,000 |  |
Restructuring and impairment charges | 9,200,000 |  |
Patent costs | $ 4,917,000 |  |
Customer One [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Percentage of total revenue | 18.00% |  |
Cutomer Two [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Percentage of total revenue | 11.00% |  |
Sinovel [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Percentage of total revenue |  | 68.00% | 70.00%
Foreign Countries [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Percentage of total revenue | 72.00% | 93.00% | 87.00%

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