Basis of Presentation and New Accounting Pronouncements (Policies)	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements of nLIGHT, Inc. and our wholly-owned subsidiaries have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) and pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). The unaudited financial information reflects, in the opinion of management, all adjustments necessary for a fair presentation of financial position, results of operations, stockholders’ equity, and cash flows for the interim periods presented. The results reported for the interim period presented are not necessarily indicative of results that may be expected for the full year. These consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2023.
New Accounting Pronouncements	New Accounting Pronouncements ASU 2023-07 In November 2023, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2023-07, Improvements to Reportable Segment Disclosures. The amendments in this ASU are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. We will adopt ASU 2023-07 in the fourth quarter of 2024 using a retrospective transition method. We are currently evaluating the impact of this guidance on our consolidated financial statements. ASU 2023-09 In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures. This ASU requires enhanced jurisdictional and other disaggregated disclosures for the effective tax rate reconciliation and income taxes paid and is effective for fiscal years beginning after December 15, 2024. This ASU requires additional disclosures and, accordingly, we do not expect the adoption of ASU 2023-09 to have a material effect on our financial position, results of operations or cash flows.
Inventory	Inventory is stated at the lower of average cost (principally standard cost, which approximates actual cost on a first-in, first-out basis) and net realizable value. Inventory includes raw materials and components that may be specialized in nature and subject to obsolescence. On a quarterly basis, we review inventory quantities on hand in comparison to our past consumption, recent purchases, and other factors to determine what inventory quantities, if any, may not be sellable. Based on this analysis, we write down the affected inventory value for estimated excess and obsolescence charges. At the point of loss recognition, a new, lower-cost basis for that inventory is established, and subsequent changes in facts and circumstances do not result in the restoration or increase in that newly established cost basis.
Product Warranties	We provide warranties on certain products and record a liability for the estimated future costs associated with warranty claims at the time revenue is recognized. The warranty liability is based on historical experience, any specifically identified failures, and our estimate of future costs. The current portion of our product warranty liability is included in the accrued liabilities and the long-term portion is included in Other long-term liabilities in our Consolidated Balance Sheets.

Disclosure of inventory accounting policy for inventory classes, including, but not limited to, basis for determining inventory amounts, methods by which amounts are added and removed from inventory classes, loss recognition on impairment of inventories, and situations in which inventories are stated above cost.