Credit Facilities - Additional Information (Detail) (USD $)	9 Months Ended	8 Months Ended				9 Months Ended			4 Months Ended
	Sep. 26, 2014	Aug. 21, 2014 LIBOR [Member]	Sep. 26, 2014 LIBOR [Member]	Sep. 26, 2014 Standby letters of credit [Member]	Sep. 26, 2014 Line of credit facility [Member]	Sep. 26, 2014 Minimum [Member]	Sep. 26, 2014 Minimum [Member] LIBOR [Member]	Sep. 26, 2014 Maximum [Member] LIBOR [Member]	Dec. 31, 2014 Subsequent Event [Member] LIBOR [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Covenant, Certain Assets to Certain Liabilities Less Deferred Revenue Ratio	3.26					1.75
Maximum borrowing capacity under bank line of credit facility	$ 10,000,000			$ 200,000
Line of Credit Facility, Remaining Borrowing Capacity					9,800,000
Line of Credit Facility, Covenant Terms	3.26 to 1
Bank line of credit facility, maturity date	Dec. 31, 2014
Unrestricted Cash Cash Equivalents And Short Term Investments To Current Liabilities Ratio	Harmonic to maintain a ratio of unrestricted cash, accounts receivable and short term investments to current liabilities (less deferred revenue) of at least 1.75 to 1.00.
Line of Credit LIBOR margin		1.75%					1.50%	1.65%	1.50%
Borrowings under bank line of credit facility	$ 0
Bank's Prime Rate	3.25%
Annualized rate of LIBOR			0.15%
LIBOR rate duration	one month borrowing period at September 26, 2014
Credit facility collateral	Borrowings are not collateralized
Covenants under the line of credit facility	As of September 26, 2014, Harmonic was in compliance with the covenants under the line of credit facility