Investments, Forward Contracts and Fair Value Measurements - Measured at Fair Value (Details) - USD ($) $ in Millions	Mar. 30, 2019	Jun. 30, 2018
Debt available-for-sale securities
Total debt available-for-sale securities	$ 26.2	$ 189.6
Money market funds	247.2	354.9
Trading securities	1.5	1.6
Foreign currency forward contract	4.1	2.7
Total assets	279.0	548.8
Liability:
Foreign currency forward contract	2.4	11.7
Contingent consideration	38.8	0.0
Total liabilities	41.2	11.7
Prepayments and other current assets
Debt available-for-sale securities
Total assets	4.1
Other current assets
Debt available-for-sale securities
Total assets		2.7
Cash and cash equivalents
Debt available-for-sale securities
Total assets	235.6	364.8
Short-term investments
Debt available-for-sale securities
Total assets	27.1	169.3
Restricted cash
Debt available-for-sale securities
Total assets	7.7	7.3
Other non-current assets
Debt available-for-sale securities
Total assets	4.5	4.7
Other current liabilities
Liability:
Total liabilities	2.4	11.7
U.S. treasuries
Debt available-for-sale securities
Total debt available-for-sale securities	1.5	35.9
U.S. agencies
Debt available-for-sale securities
Total debt available-for-sale securities	3.5	13.2
Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	1.7	2.7
Asset-backed securities
Debt available-for-sale securities
Total debt available-for-sale securities	3.5	23.5
Corporate securities
Debt available-for-sale securities
Total debt available-for-sale securities	16.0	114.3
Level 1
Debt available-for-sale securities
Total debt available-for-sale securities	1.5	35.9
Money market funds	247.2	354.9
Trading securities	1.5	1.6
Foreign currency forward contract	0.0	0.0
Total assets	250.2	392.4
Liability:
Foreign currency forward contract	0.0	0.0
Contingent consideration	0.0	0.0
Total liabilities	0.0	0.0
Level 1 \| U.S. treasuries
Debt available-for-sale securities
Total debt available-for-sale securities	1.5	35.9
Level 1 \| U.S. agencies
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Level 1 \| Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Level 1 \| Asset-backed securities
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Level 1 \| Corporate securities
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Level 2
Debt available-for-sale securities
Total debt available-for-sale securities	24.7	153.7
Money market funds	0.0	0.0
Trading securities	0.0	0.0
Foreign currency forward contract	4.1	2.7
Total assets	28.8	156.4
Liability:
Foreign currency forward contract	2.4	11.7
Contingent consideration	0.0	0.0
Total liabilities	2.4	11.7
Level 2 \| U.S. treasuries
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Level 2 \| U.S. agencies
Debt available-for-sale securities
Total debt available-for-sale securities	3.5	13.2
Level 2 \| Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	1.7	2.7
Level 2 \| Asset-backed securities
Debt available-for-sale securities
Total debt available-for-sale securities	3.5	23.5
Level 2 \| Corporate securities
Debt available-for-sale securities
Total debt available-for-sale securities	16.0	114.3
Level 3
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Money market funds	0.0	0.0
Trading securities	0.0	0.0
Foreign currency forward contract	0.0	0.0
Total assets	0.0	0.0
Liability:
Foreign currency forward contract	0.0	0.0
Contingent consideration	38.8	0.0
Total liabilities	38.8	0.0
Level 3 \| U.S. treasuries
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Level 3 \| U.S. agencies
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Level 3 \| Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Level 3 \| Asset-backed securities
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Level 3 \| Corporate securities
Debt available-for-sale securities
Total debt available-for-sale securities	$ 0.0	$ 0.0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of liability recognized arising from contingent consideration in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6911338&loc=d3e6819-128478

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of asset contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward contracts, and swaps.

+ References

No definition available.

+ Details

Name:	us-gaap_ForeignCurrencyContractAssetFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of liability contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward (delivery or nondelivery) contracts, and swaps entered into.

+ References

No definition available.

+ Details

Name:	us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value of financial and nonfinancial obligations.

+ References

+ Details

Name:	us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

+ References

No definition available.

+ Details

Name:	us-gaap_MoneyMarketFundsAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_TradingSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherCurrentAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_CashAndCashEquivalentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=viav_RestrictedCashMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherNoncurrentAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherCurrentLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=viav_MunicipalBondsAndSovereignDebtInstrumentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: