Restructuring and Related Charges - Activities in Restructuring Accrual (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 02, 2015	Sep. 26, 2014	Oct. 02, 2015	Sep. 26, 2014	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Product cost of revenue	$ 113,000	$ 15,000	$ 113,000	$ 94,000
Operating expenses - Restructuring and related charges	397,000	388,000	626,000	821,000
Total Restructuring and Related Charges	510,000	$ 403,000	739,000	$ 915,000
Harmonic Two Thousand And Fifteen Restructuring [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance			322,000
Restructuring charges			759,000		$ 2,200,000
Adjustments to restructuring provisions			(20,000)
Cash payments			(554,000)
Ending Balance	507,000		507,000		322,000
Harmonic Two Thousand And Fifteen Restructuring [Member] | Employee Severance And Benefit Arrangements [Member]
Restructuring Cost and Reserve [Line Items]
Total Restructuring and Related Charges	510,000		739,000
Restructuring Reserve [Roll Forward]
Beginning Balance			305,000
Restructuring charges			759,000		600,000
Adjustments to restructuring provisions			(14,000)
Cash payments			(543,000)
Ending Balance	507,000		507,000		305,000
Harmonic Two Thousand And Fifteen Restructuring [Member] | Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance			17,000
Restructuring charges			0		100,000
Adjustments to restructuring provisions			(6,000)
Cash payments			(11,000)
Ending Balance	$ 0		$ 0		$ 17,000