Restructuring and Excess Facilities - 2015 Activities in Restructuring Accrual (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Adjustments to restructuring provisions	$ 14,602	$ 1,372	$ 2,761
Harmonic 2015 Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	264	322
Business Exit Costs		1,617	2,169
Adjustments to restructuring provisions	(70)	(132)
Cash payments	(194)	(1,341)	(601)
Non-cash write-offs		(202)	(1,246)
Ending Balance	0	264	322
Harmonic 2015 Restructuring [Member] | Termination of an information technology (IT) project
Restructuring Cost and Reserve [Line Items]
Beginning Balance	0	0
Business Exit Costs		0	1,138
Adjustments to restructuring provisions	0	0
Cash payments	0	0	0
Non-cash write-offs		0	(1,138)
Ending Balance	0	0	0
Harmonic 2015 Restructuring [Member] | Severance and benefits
Restructuring Cost and Reserve [Line Items]
Beginning Balance	264	305
Business Exit Costs		1,413	599
Adjustments to restructuring provisions	(70)	(126)
Cash payments	(194)	(1,328)	(294)
Non-cash write-offs		0	0
Ending Balance	0	264	305
Harmonic 2015 Restructuring [Member] | Termination of a research and development project
Restructuring Cost and Reserve [Line Items]
Beginning Balance	0	0
Business Exit Costs		0	307
Adjustments to restructuring provisions	0	0
Cash payments	0	0	(307)
Non-cash write-offs		0	0
Ending Balance	0	0	0
Harmonic 2015 Restructuring [Member] | Other charges
Restructuring Cost and Reserve [Line Items]
Beginning Balance	0	17
Business Exit Costs		204	125
Adjustments to restructuring provisions		(6)
Cash payments		(13)	0
Non-cash write-offs		(202)	(108)
Ending Balance	$ 0	$ 0	$ 17