| Inventories (Details) - USD ($) $ in Thousands | Dec. 31, 2018 | Mar. 31, 2018 | 
|---|---|---|
| Components of inventories | ||
| Raw materials | $ 3,440 | $ 2,969 | 
| Finished goods | 6,723 | 6,253 | 
| Total inventories | $ 10,163 | $ 9,222 | 
| X | ||||||||||
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- Definition Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of merchandise or goods held by the company that are readily available for sale. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- References No definition available. 
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- Definition Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of unprocessed items to be consumed in the manufacturing or production process. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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