Interim Financial Statements (Policies)	9 Months Ended
Interim Financial Statements (Policies)	Sep. 30, 2017
Quarterly Financial Information Disclosure [Abstract]
Prior Periods Financial Statement Revision	Prior Periods’ Financial Statement Revision In connection with the preparation of condensed consolidated financial statements as of and for the three-month and six-month periods ended June 30, 2017, we identified misstatements in our previously issued financial statements related to the foreign currency translation of our investment in a China joint venture. We acquired a 49% investment in the joint venture as part of the acquisition of Autocam Corporation (“Autocam”) on August 29, 2014. We remeasured the investment in the joint venture to fair value at the time of the acquisition, and we have accounted for the investment under the equity method of accounting. Following the completion of the Autocam acquisition, we accounted for the investment in the joint venture in U.S. dollars whereas it should have been accounted for in the joint venture’s functional currency of the Chinese Renminbi in accordance with Accounting Standards Codification (“ASC”) Topic 830, Foreign Currency Matters. As a result, we did not correctly account for the investment in the joint venture and the related currency translation adjustment impacts. We previously corrected as out-of-period adjustments certain immaterial misstatements and reflected them in the prior period financial statements, where applicable. These immaterial previously recorded out-of-period adjustments were primarily due to misstatements related to the initial recording of deferred tax assets and liabilities and corresponding adjustments to goodwill as part of the purchase price allocations of the Autocam and PEP acquisitions in 2014 and 2015, the accounting for the goodwill balances from those acquisitions for multi-currency reporting through other comprehensive income, and the mark-to-market adjustments on our interest rate hedge, net of tax, through other comprehensive income. We assessed the materiality of the misstatements on prior periods’ financial statements in accordance with SEC Staff Accounting Bulletin (“SAB”) Topic 1.M, Materiality, codified in ASC Topic 250, Accounting Changes and Error Corrections, (“ASC 250”) and concluded that the misstatements were not material to any prior annual or interim periods. In accordance with ASC 250 (SAB Topic 1.N, Considering the Effects of Prior Year Misstatements when Quantifying Misstatements in Current Year Financial Statements), we have corrected these misstatements for all prior periods presented by revising the condensed consolidated financial statements and other consolidated financial information included herein. We have revised, and will revise for annual and interim periods in future filings, certain amounts in the consolidated financial statements to correct these misstatements. See Note 15 for additional information on the revision.
Recently Issued Accounting Standards	Issuance of New Accounting Standards Revenue Recognition. In May 2014, the FASB issued a new standard that provides a single, comprehensive revenue recognition model for all contracts with customers and supersedes most of the existing revenue recognition requirements. Under the new guidance, revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration the entity expects to receive in exchange for those goods or services. The standard also requires disclosure of the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Factors that will affect pre-and post-implementation include, but are not limited to, identifying all the contracts that exist and whether incidental obligations or marketing incentives included in some of those contracts are performance obligations. Additionally, we are evaluating the transfer of control of certain consignment contracts which may impact the timing of revenue recognition under the new standard. The standard will be effective for us beginning January 1, 2018. We intend to adopt the standard utilizing the modified retrospective transition method. Under this transition method, we will recognize the cumulative effect of initially applying the new standard as an adjustment to the opening balance of retained earnings as of January 1, 2018, and will apply the new standard beginning with the most current period presented to contracts that are not completed at the date of initial application. We continue to evaluate the adoption method throughout each phase of implementation. While our ability to adopt the standard using the modified retrospective method depends on system readiness and completing our analysis of information necessary to present required footnote disclosures in the consolidated financial statements, the implementation project remains on schedule. We have completed a diagnostic accounting assessment, including an analysis of a representative sample of contracts, to identify areas that will be most significantly impacted by implementation of the new standard. We have also completed initial training to educate contract managers of the technical aspects of the new standard. We are in the process of concluding on and documenting our assessments related to the standard as well as potential system and procedural changes. We are evaluating the impact the new standard will have on our financial condition, results of operations and cash flows. We expect to complete our final evaluation of the impact of adopting the new standard during 2017. Leases. In February 2016, the FASB issued ASU 2016-02, Leases. ASU 2016-02 creates Topic 842, Leases, in the ASC and supersedes ASC 840, Leases. Entities that hold numerous equipment and real estate leases, in particular those with numerous operating leases, will be most affected by the new guidance. The lease accounting standard is effective for NN beginning January 1, 2019, with modified retrospective adoption required and early adoption permitted. The amendments in ASU 2016-02 are expected to impact balance sheets at many companies by adding lease-related assets and liabilities. This may affect compliance with contractual agreements and loan covenants. We have performed inquiries within segment locations and compiled information on operating and capital leases. We are currently evaluating the impacts of the lease accounting standard on our financial position, results of operations, and related disclosures. Statement of Cash Flows. In August 2016, the FASB issued ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments. This standard provides clarification on how certain cash receipts and cash payments are presented and classified on the statement of cash flows. The standard is effective for NN beginning January 1, 2018, and is required to be adopted using a retrospective approach if practicable, with early adoption permitted. We are in the process of assessing the effects of the standard on prior periods. We expect to complete our final evaluation of the impact of adopting the new standard during 2017. Although our analysis of the effects on prior periods is not yet complete, we have identified $31.6 million of cash paid for debt prepayment in April 2017 that is currently classified as an operating cash outflow. Under the new guidance, this $31.6 million will be classified as a financing cash outflow. Goodwill. In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, that eliminates the requirement to calculate the implied fair value of goodwill (i.e., Step 2 of the current goodwill impairment test) to measure a goodwill impairment charge. Instead, entities will record an impairment charge based on the excess of a reporting unit’s carrying amount over its fair value (i.e., measure the charge based on the current Step 1 test). The standard is effective for NN beginning with impairment tests performed on or after January 1, 2020, with early adoption permitted. We are currently evaluating the impact this new guidance is expected to have on our financial position or results of operations and related disclosures.