Share-based Compensation Arrangement by Share-based Payment Award, Award Performance Period

No definition available.

Name:	nnbr_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardPerformancePeriod
Namespace Prefix:	nnbr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Share based compensation arrangement by share based payment award percentage of shares issuable based on threshold performance.

+ References

No definition available.

+ Details

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

- Definition

Share based compensation arrangement by share-based payment award percentage of shares issuable based on maximum performance.

+ References

No definition available.

+ Details

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

- Definition

Share based compensation arrangement by share-based payment award, percentage of shares Issuable based on target performance.

+ References

No definition available.

+ Details

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

- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_StatementOperatingActivitiesSegmentAxis=us-gaap_SegmentDiscontinuedOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=nnbr_PerformanceSharesTsrAwardsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=nnbr_PerformanceSharesReturnOnInvestedCapitalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_ChangeInAccountingMethodAccountedForAsChangeInEstimateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_TitleOfIndividualAxis=nnbr_EmployeesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_TitleOfIndividualAxis=nnbr_NonExecutiveDirectorsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Shared-Based Compensation - Additional Information (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 763	$ 1,411	$ 1,649	$ 2,707
Discontinued Operations
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation		200		400
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	591	936	$ 1,139	1,828
Stock units issued (in shares)			459
Total grant-date fair value of restricted stock, vested			$ 2,800
TSR Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units issued (in shares)			142
Award performance period			36 months
Percentage of shares issuable based on threshold performance			50.00%
Percentage of shares issuable based on target performance			100.00%
Percentage of shares issuable based on maximum performance			150.00%
ROIC Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units issued (in shares)			172
Percentage of shares issuable based on target performance			100.00%
Change in estimate of share-based award vesting (1)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ (337)	$ 0	$ (337)	$ 0
Employees \| Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards granted vesting period			3 years
Non-executive Directors \| Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards granted vesting period			1 year