Calculation of Net Income Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Feb. 28, 2015	Feb. 28, 2014	Feb. 28, 2015	Feb. 28, 2014
Earnings Per Share [Line Items]
Net Income attributable to Neogen shareholders	$ 7,454us-gaap_NetIncomeLoss	$ 6,575us-gaap_NetIncomeLoss	$ 24,142us-gaap_NetIncomeLoss	$ 20,621us-gaap_NetIncomeLoss
Weighted average shares	37,006	36,613	36,907	36,471
Effect of dilutive stock options and warrants	530	620	492	678
Denominator for diluted net income per share	37,536	37,233	37,399	37,149
Net income attributable to Neogen Corporation per share:
Basic	$ 0.20us-gaap_EarningsPerShareBasic	$ 0.18us-gaap_EarningsPerShareBasic	$ 0.65us-gaap_EarningsPerShareBasic	$ 0.57us-gaap_EarningsPerShareBasic
Diluted	$ 0.20us-gaap_EarningsPerShareDiluted	$ 0.18us-gaap_EarningsPerShareDiluted	$ 0.65us-gaap_EarningsPerShareDiluted	$ 0.56us-gaap_EarningsPerShareDiluted

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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- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of call options and warrants using the treasury stock method.

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- Definition

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

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