Segment Information - Narratives (Details) $ in Thousands	3 Months Ended					12 Months Ended
	Dec. 31, 2016 USD ($) Customer	Sep. 30, 2016 USD ($)	Jul. 01, 2016 USD ($)	Apr. 01, 2016 USD ($)	Dec. 31, 2014 Customer segment	Dec. 31, 2016 USD ($) Customer segment		Dec. 31, 2015 USD ($) Customer	Dec. 31, 2014 USD ($) Customer	Feb. 29, 2016
Concentration Risk [Line Items]
Number of reportable segments | segment					2	2
Business Acquisition, Percentage of Voting Interests Acquired										100.00%
Restructuring and Related Cost						$ 18,002	[1]	$ 1,485	$ 3,076
Provision for excess and obsolete inventories						$ 6,871		$ 1,585	$ 2,569
Number Of Customers Accounting For More Than Ten Percent of Revenue | Customer	0					0
TVN Voluntary Departure Plan [Member]
Concentration Risk [Line Items]
Restructuring and Related Cost						$ 13,100
Customer concentration risk ten percent or more of net revenue [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage						0.00%
Number Of Customers Accounting For More Than Ten Percent Of Revenue Other Than Comcast					0			0	0
Net Revenue [Member]
Concentration Risk [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				0	0		0	0
Net Revenue [Member] | Comcast [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage								12.00%	16.00%
Cable Edge [Member] | Operating Segments [Member]
Concentration Risk [Line Items]
Provision for excess and obsolete inventories			$ 4,500			$ 4,000
Harmonic Two Thousand And Sixteen Restructuring [Member] | TVN Voluntary Departure Plan [Member]
Concentration Risk [Line Items]
Restructuring and Related Cost						$ 13,100
UNITED STATES | Net Revenue [Member]
Concentration Risk [Line Items]
Number Of Countries Accounting For More Than Ten Percent of Non United States Revenue	0					0
Concentration Risk, Percentage						10.00%
TVN [Member]
Concentration Risk [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired										100.00%
Business Combination, Acquisition and Integration Related Expenses	$ 5,200	$ 5,300	$ 3,400	$ 3,000		$ 16,900

[1] The restructuring and related charges for the year ended December 31, 2016 is net of $0.6 million and $1.4 million, in product cost of revenue and operating expenses-restructuring and related charges, respectively, of gain from TVN pension curtailment. See Note 13, “Employee Benefit Plans and Stock-based Compensation-TVN Retirement Benefit Plan,” for additional information on gain from TVN pension curtailment.