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Employee Benefit Plans - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] |  |  |
Compensation to the plans | 60.00% |  |
Minimum age for IRS catch up provision limit | 50 years |  |
Vesting percentage | 100.00% |  |
Matching contribution, Amount | $ 349 | $ 335 | $ 334
Severance indemnities paid to the pension fund | 1/13.5 of the gross salary |  |
Minimum [Member] |  |  |
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] |  |  |
Compensation to the plans | 1.00% |  |
Award for employees | 25 years |  |
Maximum [Member] |  |  |
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] |  |  |
Award for employees | 40 years |  |

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- Definition Defined contribution plan annual contribution per employee percent. + References No definition available. + Details
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Namespace Prefix: | nnbr_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Minimum age for IRS catch up provision limit. + References No definition available. + Details
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Balance Type: | na
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- Definition Post employment benefit period of service for award grant. + References No definition available. + Details
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Namespace Prefix: | nnbr_
Data Type: | xbrli:durationItemType
Balance Type: | na
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- Definition Severance indemnities accrual rate. + References No definition available. + Details
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Namespace Prefix: | nnbr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
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Data Type: | xbrli:stringItemType
Balance Type: | na
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- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Percentage of employer's matching contributions to a defined contribution plan that vests in a given year. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration