Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands		Sep. 25, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross		$ 150,304	$ 136,131
Less: accumulated depreciation and amortization		(108,389)	(113,203)
Property and Equipment, Net		41,915	22,928
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross		71,874	75,229
Capitalized Software [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross		36,345	34,190
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	[1]	1,870	5,506
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross		37,436	15,170
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross		2,779	$ 6,036
Harmonic Headquarter Lease Commencing May 2019 [Member] | Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross		$ 22,900

[1] During the third quarter of 2020, the Company completed construction of its leasehold improvements for the new headquarters facility and transferred $22.9 million of assets from Construction in progress to Leasehold improvements.