Employee Benefit Plans and Stock-based Compensation - Summary of Restricted Stock Units Outstanding (Detail) - Restricted Stock Units Outstanding [Member] shares in Thousands, $ in Thousands	3 Months Ended
Apr. 01, 2016 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Underlying Restricted Stock Units \| shares	1,971
Weighted Average Remaining Vesting Period (Years)	1 year 1 month
Aggregate Fair Value \| $	$ 6,484

Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period And Expected To Vest Total Fair Value

No definition available.

+ Details

Name:	hlit_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodAndExpectedToVestTotalFairValue
Namespace Prefix:	hlit_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Share Based Compensation Arrangement By Share Based Payment Award Other Than Options Vested And Expected To Vest Outstanding Number

+ References

No definition available.

+ Details

Name:	hlit_ShareBasedCompensationArrangementByShareBasedPaymentAwardOtherThanOptionsVestedAndExpectedToVestOutstandingNumber
Namespace Prefix:	hlit_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: