Debt Instrument, Repurchase Amount (QTD)

No definition available.

Name:	stx_DebtInstrumentRepurchaseAmountQTD
Namespace Prefix:	stx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Debt Instrument, Repurchase Amount (YTD)

+ References

No definition available.

+ Details

Name:	stx_DebtInstrumentRepurchaseAmountYTD
Namespace Prefix:	stx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The maximum amount available for issuances of letters of credit under the revolving credit facility.

+ References

No definition available.

+ Details

Name:	stx_LineOfCreditFacilityAvailableForIssuancesOfLettersOfCreditMaximum
Namespace Prefix:	stx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line Of Credit Facility, Percentage Of Most Favored Nation Protection

+ References

No definition available.

+ Details

Name:	stx_LineOfCreditFacilityPercentageOfMostFavoredNationProtection
Namespace Prefix:	stx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility, accordion feature, increase limit, subject to certain conditions by obtaining additional commitments from existing and/or new lenders.

+ References

No definition available.

+ Details

Name:	stx_LineofCreditFacilityAccordionFeatureIncreaseLimit
Namespace Prefix:	stx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

Name:	us-gaap_DebtInstrumentRedemptionPricePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value amount of debt instrument that was repurchased.

+ References

No definition available.

+ Details

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

- Definition

Amount of gain (loss) from the difference between the repurchase price of a debt instrument initially issued by the entity and the net carrying amount of the debt at the time of its repurchase.

+ References

No definition available.

+ Details

Name:	us-gaap_GainLossOnRepurchaseOfDebtInstrument
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The maximum amount of borrowing capacity under a line of credit that is available as of the balance sheet date for a specific purpose other than for financing goods acquired for inventory or imminent delivery to a customer.

+ References

No definition available.

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

Name:	us-gaap_ProceedsFromLinesOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=stx_A2019RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_BridgeLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=stx_TermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_MediumTermNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=stx_SeniorNotes4.25PercentDueMarch2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=stx_SeniorNotes4.75PercentDueJune2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=stx_SeniorNotes4.875PercentDueMarch2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=stx_SeniorNotes4.75PercentDueJanuary2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=stx_Seniornote4.875percentdueJune2027Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=stx_Seniornote5.75percentdueDecember2034Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt (Narrative) (Details) - USD ($)			3 Months Ended	6 Months Ended	9 Months Ended
Debt (Narrative) (Details) - USD ($)	Sep. 17, 2019	Feb. 20, 2019	Apr. 03, 2020	Jan. 03, 2020	Apr. 03, 2020	Sep. 18, 2019	Feb. 03, 2017	May 14, 2015	Dec. 02, 2014	May 28, 2014	May 22, 2013
2019 Revolving Credit Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 1,500,000,000
Line of credit facility, accordion feature, increase limit		$ 100,000,000
Line of credit facility, percentage of most favored nation protection		0.50%
Amount of borrowings drawn					$ 0
2019 Revolving Credit Facility \| Line of Credit [Member]
Debt Instrument [Line Items]
Sub-limit for issuance of letters of credit under revolving credit facility		$ 75,000,000
2019 Revolving Credit Facility \| Bridge Loan [Member]
Debt Instrument [Line Items]
Line of credit facility, capacity available for specific purpose other than for trade purchases		50,000,000
Term Loan \| Revolving Credit Facility
Debt Instrument [Line Items]
Redemption price	1.25%
Term Loan \| Term Loan
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		500,000,000
Amount of borrowings drawn	$ 500,000,000
Senior Notes \| Senior Notes 4.25 Percent Due March 2022 [Member]
Debt Instrument [Line Items]
Aggregate principal amount							$ 750,000,000
Stated interest rate (as a percent)							4.25%
Debt Instrument, Repurchase Amount (3 Months)			$ 23,000,000
Debt Instrument, Repurchase Amount (9 Months)					273,000,000
Amount of debt repurchased						$ 250,000,000
Gain (loss) on repurchase of debt instrument					(10,000,000)
Senior Notes \| Senior Notes 4.75 Percent Due June 2023 [Member]
Debt Instrument [Line Items]
Aggregate principal amount											$ 1,000,000,000
Stated interest rate (as a percent)											4.75%
Debt Instrument, Repurchase Amount (3 Months)			$ 17,000,000
Debt Instrument, Repurchase Amount (9 Months)				$ 217,000,000
Amount of debt repurchased						200,000,000
Gain (loss) on repurchase of debt instrument					(10,000,000)
Senior Notes \| Senior Notes 4.875 Percent Due March 2024 [Member]
Debt Instrument [Line Items]
Aggregate principal amount							$ 500,000,000
Stated interest rate (as a percent)							4.875%
Senior Notes \| Senior Notes 4.75 Percent Due January 2025 [Member]
Debt Instrument [Line Items]
Aggregate principal amount										$ 1,000,000,000
Stated interest rate (as a percent)										4.75%
Amount of debt repurchased						$ 170,000,000
Gain (loss) on repurchase of debt instrument					$ (8,000,000)
Senior Notes \| Senior Notes 4.875 percent Due June 2027 [Member]
Debt Instrument [Line Items]
Aggregate principal amount								$ 700,000,000
Stated interest rate (as a percent)								4.875%
Senior Notes \| Senior note 5.75 percent due December 2034 [Member]
Debt Instrument [Line Items]
Aggregate principal amount									$ 500,000,000
Stated interest rate (as a percent)									5.75%
Minimum \| 2019 Revolving Credit Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, accordion feature, increase limit		$ 25,000,000