Debt - Summary of Long-Term Debt (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2013
Debt Instrument [Line Items]
Borrowings	$ 100,000
Line of credit LIBOR rate	0.1875%
Applicable margin added to the interest rate post amendment	1.25%
April 26, 2014 [Member]
Debt Instrument [Line Items]
Percentage of fixed interest rate bearing	4.89%
December 20, 2018 [Member]
Debt Instrument [Line Items]
Percentage of fixed interest rate bearing	4.64%
Fixed Rate Notes [Member] \| April 26, 2014 [Member]
Debt Instrument [Line Items]
Fixed rate notes payable	40,000
Annual principal payment of fixed rate notes	5,714
Fixed Rate Notes [Member] \| December 20, 2018 [Member]
Debt Instrument [Line Items]
Fixed rate notes payable	20,000
Annual principal payment of fixed rate notes	$ 4,000

Line of credit facility basis spread on variable rate post amendment.

No definition available.

Name:	nnbr_LineOfCreditFacilityBasisSpreadOnVariableRatePostAmendment
Namespace Prefix:	nnbr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line of credit LIBOR rate.

+ References

No definition available.

+ Details

Name:	nnbr_LineOfCreditLiborRate
Namespace Prefix:	nnbr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the total principal payments made during the annual reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

+ Details

Name:	us-gaap_DebtInstrumentAnnualPrincipalPayment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant