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Net Income Per Share - Additional Information (Detail) (USD $)
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Earnings Per Share [Abstract]    
Anti-dilutive options 0us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount 96,000us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Anti-dilutive securities excluded from computation of earnings per share exercise price   $ 19.63nnbr_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareExercisePrice