Revenue Recognition (Schedule of Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
Dec. 28, 2018	Dec. 29, 2017	Sep. 28, 2018
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 302,376	$ 299,527
Revenue from contract with customer, percent	100.00%	100.00%
Accounts receivable, net	$ 181,614		$ 200,933
Increase (decrease) in accounts receivable	$ (19,319)
Increase (decrease) in accounts receivable, percent	(10.00%)
Contract assets	$ 199,480		165,959
Contract asset, increase (decrease)	$ 33,521
Contract asset, increase (decrease), percent	20.00%
Contract liabilities - current	$ 19,562		20,502
Contract liabilities - current, increase (decrease)	$ (940)
Contract liabilities - current, increase (decrease), percent	(5.00%)
Contract liabilities - non-current	$ 23,115		$ 22,853
Contract liabilities - noncurrent, increase (decrease)	$ 262
Contract liabilities - noncurrent, increase (decrease), percent	1.00%
United States
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 119,799	$ 78,746
Revenue from contract with customer, percent	40.00%	26.00%
International
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 182,577	$ 220,781
Revenue from contract with customer, percent	60.00%	74.00%
Licensing
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 260,279	$ 270,172
Revenue from contract with customer, percent	86.00%	90.00%
Revenue from contract with customer, licensing percent	100.00%	100.00%
Products and Services
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 42,097	$ 29,355
Revenue from contract with customer, percent	14.00%	10.00%
Broadcast
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 100,138	$ 110,484
Revenue from contract with customer, licensing percent	38.00%	41.00%
PC
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 23,157	$ 20,351
Revenue from contract with customer, licensing percent	9.00%	8.00%
Mobile
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 34,173	$ 58,645
Revenue from contract with customer, licensing percent	13.00%	22.00%
CE
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 43,750	$ 37,730
Revenue from contract with customer, licensing percent	17.00%	14.00%
Other
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 59,061	$ 42,962
Revenue from contract with customer, licensing percent	23.00%	15.00%

Accounts Receivable, Net, Percent, Increase (Decrease)

No definition available.

Name:	dlb_AccountsReceivableNetPercentIncreaseDecrease
Namespace Prefix:	dlb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Contract With Customer, Asset, Increase (Decrease)

+ References

No definition available.

+ Details

Name:	dlb_ContractWithCustomerAssetIncreaseDecrease
Namespace Prefix:	dlb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Contract With Customer, Asset, Percent, Increase (Decrease)

+ References

No definition available.

+ Details

Name:	dlb_ContractWithCustomerAssetPercentIncreaseDecrease
Namespace Prefix:	dlb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Contract With Customer, Liability, Increase (Decrease), Current

+ References

No definition available.

+ Details

Name:	dlb_ContractWithCustomerLiabilityIncreaseDecreaseCurrent
Namespace Prefix:	dlb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Contract With Customer, Liability, Increase (Decrease), Noncurrent

+ References

No definition available.

+ Details

Name:	dlb_ContractWithCustomerLiabilityIncreaseDecreaseNoncurrent
Namespace Prefix:	dlb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Contract With Customer, Liability, Percent, Increase (Decrease), Current

+ References

No definition available.

+ Details

Name:	dlb_ContractWithCustomerLiabilityPercentIncreaseDecreaseCurrent
Namespace Prefix:	dlb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Contract With Customer, Liability, Percent, Increase (Decrease), Noncurrent

+ References

No definition available.

+ Details

Name:	dlb_ContractWithCustomerLiabilityPercentIncreaseDecreaseNoncurrent
Namespace Prefix:	dlb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Increase (Decrease) In Accounts Receivable, Net

+ References

No definition available.

+ Details

Name:	dlb_IncreaseDecreaseInAccountsReceivableNet
Namespace Prefix:	dlb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Revenue From Contract With Customer, Excluding Assessed Tax, Percentage

+ References

No definition available.

+ Details

Name:	dlb_RevenueFromContractWithCustomerExcludingAssessedTaxPercentage
Namespace Prefix:	dlb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Revenue From Contract With Customer, Excluding Assessed Tax, Percentage Of Licensing Revenues

+ References

No definition available.

+ Details

Name:	dlb_RevenueFromContractWithCustomerExcludingAssessedTaxPercentageOfLicensingRevenues
Namespace Prefix:	dlb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(4))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130533-203044

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173487&loc=SL51747714-108306

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130549-203045

+ Details

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

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130549-203045

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130532-203044

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

+ Details

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

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as noncurrent.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130549-203045

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130532-203044

+ Details

Name:	us-gaap_ContractWithCustomerLiabilityNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_EntityWideInformationRevenueFromExternalCustomerLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 32
-Paragraph 2A
-URI http://asc.fasb.org/extlink&oid=82859839&loc=SL82860478-203043

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130543-203045

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130539-203045

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130545-203045

+ Details

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

- Details

Name:	us-gaap_StatementGeographicalAxis=country_US
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=us-gaap_NonUsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=dlb_TotalLicensingRevenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=dlb_ProductsAndServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=dlb_LicensingBrodcastRevenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=dlb_LicensingPCRevenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=dlb_LicensingMobileRevenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=dlb_LicensingCERevenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=dlb_LicensingOtherRevenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: