Segment Information - Narratives (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2014 segment	Dec. 31, 2018 USD ($) Customer segment country	Dec. 31, 2017 USD ($) Customer country	Dec. 31, 2016 USD ($) Customer country		Feb. 29, 2016
Segment Reporting Information [Line Items]
Number of reportable segments | segment	2	2
Restructuring and Related Cost		$ 2,918	$ 5,307	$ 14,602	[1]
Sales Revenue, Net [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage		10.00%	10.00%
Number Of Customers Accounting For More Than Ten Percent Of Revenue Other Than Comcast | Customer				0
Customer concentration risk ten percent or more of net revenue [Member]
Segment Reporting Information [Line Items]
Number Of Customers Accounting For More Than Ten Percent of Revenue | Customer			0	0
Non-US [Member] | Sales Revenue, Net [Member]
Segment Reporting Information [Line Items]
Number Of Countries Accounting For More Than Ten Percent of Non United States Revenue | country		0	0	0
Concentration Risk, Percentage		10.00%
Harmonic Two Thousand And Sixteen Restructuring [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Restructuring and Related Cost			$ 7,900	$ 32,200
Avid Technology Inc. [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Litigation Settlement, Expense			8,000
TVN [Member]
Segment Reporting Information [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired						100.00%
Operating expense [Member] | Change in Accounting Method Accounted for as Change in Estimate [Member]
Segment Reporting Information [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification			$ 5,900
Comcast [Member] | Customer Concentration Risk [Member] | Sales Revenue, Net [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage		15.00%
Number Of Customers Accounting For More Than Ten Percent of Revenue | Customer		1	0

[1] The restructuring and related charges for the fiscal year ended December 31, 2016 is net of $0.6 million and $1.4 million, in Cost of revenue and Operating expenses - Restructuring and related charges, respectively, of gain from TVN pension curtailment. See “Harmonic 2016 Restructuring Plan” below for additional information.