Restructuring and Excess Facilities - Schedule of Restructuring Costs By Type (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	$ 8,043
Charges for current period	3,056
Adjustments to restructuring provisions	719
Reclassification of deferred rent	332
Cash payments	(6,675)
Foreign exchange effect	(140)
Restructuring Reserve	5,335	$ 8,043
Harmonic 2017 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Charges for current period		2,500
Excess Facilities [Member] \| Harmonic 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	2,426
Adjustments to restructuring provisions	132
Cash payments	(1,015)
Restructuring Reserve	1,543	2,426
Excess Facilities [Member] \| Harmonic 2017 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	296
Charges for current period		400
Adjustments to restructuring provisions	167
Cash payments	(146)
Restructuring Reserve	317	296
Excess Facilities [Member] \| Harmonic 2018 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Charges for current period	932
Adjustments to restructuring provisions	5
Reclassification of deferred rent	332
Cash payments	(203)
Restructuring Reserve	1,066
TVN Voluntary Departure Plan [Member] \| Harmonic 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	5,128
Adjustments to restructuring provisions	531
Cash payments	(3,066)
Foreign exchange effect	(184)
Restructuring Reserve	2,409	5,128
Severance and benefits [Member] \| Harmonic 2017 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	193
Charges for current period		2,100
Cash payments	(193)
Restructuring Reserve	0	$ 193
Severance and benefits [Member] \| Harmonic 2018 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Charges for current period	2,124
Adjustments to restructuring provisions	(116)
Cash payments	(2,052)
Foreign exchange effect	44
Restructuring Reserve	$ 0

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Includes, but is not limited to, one-time termination benefits, termination of an operating lease or other contract, consolidating or closing facilities, and relocating employees, and termination benefits associated with an ongoing benefit arrangement. Excludes expenses associated with special or contractual termination benefits, a discontinued operation or an asset retirement obligation.

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Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.

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Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

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Amount of expense (reversal of expense) which increases (decreases) the restructuring reserve from an adjustment to a previously accrued restructuring liability.

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Amount of increase (decrease) in the restructuring reserve related to foreign currency translation (gain) loss and other increases (decreases).

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Difference between actual rental income due and rental income recognized on a straight-line basis.

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