Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 26, 2020		Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	$ 158,697		$ 136,131
Less: accumulated depreciation and amortization	(117,356)		(113,203)
Property and Equipment, Net	41,341		22,928
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	73,508		75,229
Capitalized Software [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	35,027		34,190
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	25,549	[1]	5,506
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	15,674		15,170
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	8,939		$ 6,036
Harmonic Headquarter Lease Commencing May 2019 [Member] | Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	$ 22,900

[1] During fiscal 2019, the Company entered into a lease for a new facility which will become the Company’s new headquarters in 2020. The new lease commenced in May 2019, as the facility was made available to the Company for constructing leasehold improvements. Construction in progress includes $22.9 million for constructing leasehold improvements in the new headquarters facility.