Document and Entity Information - shares	6 Months Ended
	Jun. 26, 2020	Jul. 27, 2020
Document Information [Line Items]
Title of 12(b) Security	Common stock, $0.001 par value
Entity Incorporation, State or Country Code	DE
Entity File Number	000-25826
Document Transition Report	false
Document Annual Report	true
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 26, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Entity Registrant Name	HARMONIC INC.
Entity Central Index Key	0000851310
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		97,429,109
Entity Tax Identification Number	77-0201147
Entity Address, Address Line One	4300 North First Street
Entity Address, City or Town	San Jose
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95134
City Area Code	408
Local Phone Number	542-2500
Trading Symbol	HLIT
Security Exchange Name	NASDAQ