Leases - Narratives (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Lease, Practical Expedients, Package [true false]	true
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 12,032
Operating lease liability (short-term)	8,881
Operating Lease, Liability, Noncurrent	$ 25,766
Lease, Practical Expedient, Lessor Single Lease Component [true false]	true
Minimum [Member] | Leaseholds and Leasehold Improvements [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	1 year
Maximum [Member] | Leaseholds and Leasehold Improvements [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	11 years
Initial Lease Term Threshold Not Capitalized as Operating Lease	12 months
Harmonic Headquarter Lease Commencing May 2019 [Member] | Prepaid Expenses and Other Current Assets [Member] | Leaseholds and Leasehold Improvements [Member]
Lessee, Lease, Description [Line Items]
Lease Incentive Receivable, Current	$ 4,000
Harmonic Headquarter Lease Commencing May 2019 [Member] | Other Noncurrent Liabilities [Member] | Leaseholds and Leasehold Improvements [Member]
Lessee, Lease, Description [Line Items]
Operating lease liability (short-term)	600
Harmonic Headquarter Lease Commencing May 2019 [Member] | Accrued Liabilities [Member] | Leaseholds and Leasehold Improvements [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Liability, Noncurrent	$ 15,500