CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Income Statement [Abstract]
Net sales	$ 89,782us-gaap_SalesRevenueNet	$ 85,933us-gaap_SalesRevenueNet	$ 79,956us-gaap_SalesRevenueNet
Cost of sales	54,918us-gaap_CostOfGoodsAndServicesSold	54,802us-gaap_CostOfGoodsAndServicesSold	47,143us-gaap_CostOfGoodsAndServicesSold
Gross profit	34,864us-gaap_GrossProfit	31,131us-gaap_GrossProfit	32,813us-gaap_GrossProfit
Selling, general and administrative expenses	15,352	13,880	15,246
Engineering expense	6,607bzc_EngineeringExpense	8,162bzc_EngineeringExpense	9,377bzc_EngineeringExpense
Operating income	12,905us-gaap_OperatingIncomeLoss	9,089us-gaap_OperatingIncomeLoss	8,190us-gaap_OperatingIncomeLoss
Interest expense	32us-gaap_InterestExpense	49us-gaap_InterestExpense	227us-gaap_InterestExpense
Other (income) expense – net	(1,611)us-gaap_OtherNonoperatingIncomeExpense	89us-gaap_OtherNonoperatingIncomeExpense	93us-gaap_OtherNonoperatingIncomeExpense
Income before income taxes	14,484	8,951	7,870
Income tax (benefit) provision	(423)us-gaap_IncomeTaxExpenseBenefit	3,310us-gaap_IncomeTaxExpenseBenefit	3,794us-gaap_IncomeTaxExpenseBenefit
Net income	$ 14,907us-gaap_NetIncomeLoss	$ 5,641us-gaap_NetIncomeLoss	$ 4,076us-gaap_NetIncomeLoss
Earnings per common share:
Basic net income per share:	$ 1.52us-gaap_EarningsPerShareBasic	$ 0.58us-gaap_EarningsPerShareBasic	$ 0.43us-gaap_EarningsPerShareBasic
Diluted net income per share:	$ 1.50us-gaap_EarningsPerShareDiluted	$ 0.58us-gaap_EarningsPerShareDiluted	$ 0.43us-gaap_EarningsPerShareDiluted
Weighted-average basic shares outstanding	9,778,000	9,643,000	9,511,000
Weighted-average diluted shares outstanding	9,946,000	9,757,000	9,573,000

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The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the cost of borrowed funds accounted for as interest expense.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The net result for the period of deducting operating expenses from operating revenues.

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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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