Cover - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Feb. 22, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-38462
Entity Registrant Name	NLIGHT, INC.
Entity Incorporation, Date of Incorporation	DE
Entity Tax Identification Number	91-2066376
Entity Address, Address Line One	5408 NE 88th Street, Building E
Entity Address, City or Town	Vancouver
Entity Address, State or Province	WA
Entity Address, Postal Zip Code	98665
City Area Code	360
Local Phone Number	566-4460
Title of 12(b) Security	Common Stock, par value$0.0001 per share
Trading Symbol	LASR
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Smaller Reporting Company	false
Emerging Growth	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 845.5
Entity Common Stock, Shares Outstanding		40,134,273
Documents Incorporated by Reference	Portions of the registrant's definitive Proxy Statement for the 2021 Annual Meeting of Stockholders are incorporated herein by reference in Part III of this Annual Report on Form 10-K to the extent stated herein. Such Proxy Statement will be filed with the Securities and Exchange Commission within 120 days of the registrant's fiscal year ended December 31, 2020.
Entity Central Index Key	0001124796
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false