Composition Of Certain Financial Statement Captions [Line Items].

No definition available.

Name:	dlb_CompositionOfCertainFinancialStatementCaptionsLineItems
Namespace Prefix:	dlb_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of asset acquired in business combination and recognized at acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479907/805-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479907/805-20-50-1

+ Details

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

- Definition

Amount before valuation and LIFO reserves of raw materials expected to be sold, or consumed within one year or operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480657/210-10-S50-3

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(6)(a)(4))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

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

- Definition

Amount received for services rendered and products shipped, but not yet billed, for non-contractual agreements due within one year or the normal operating cycle, if longer.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_BusinessAcquisitionAxis=dlb_GELicensingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementOfFinancialPositionLocationBalanceAxis=us-gaap_OtherAssetsNoncurrent
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Composition Of Certain Financial Statement Captions (Narrative) (Details) - USD ($) $ in Thousands	Jun. 26, 2026	Sep. 26, 2025	Sep. 27, 2024	Aug. 19, 2024
Composition Of Certain Financial Statement Captions [Line Items]
Unbilled Receivables, Current	$ 120,500	$ 173,500
Raw materials	5,908	4,254
GE Licensing
Composition Of Certain Financial Statement Captions [Line Items]
Assets acquired		8,700	$ 24,500	$ 18,200
Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherAssetsNoncurrent
Composition Of Certain Financial Statement Captions [Line Items]
Raw materials	$ 3,900	$ 7,500