Composition Of Certain Financial Statement Captions (Schedule Of Accounts Receivable) (Details) - USD ($) $ in Thousands	Dec. 25, 2020	Sep. 25, 2020
Composition Of Certain Financial Statement Captions [Abstract]
Trade accounts receivable	$ 172,952	$ 147,618
Accounts receivable related to patent administration program	133,620	48,630
Contract assets	187,754	161,357
Accounts receivable, gross	494,326	357,605
Less: allowance for doubtful accounts	(12,839)	(15,908)
Accounts receivable, net	481,487	341,697
Unbilled Receivables, Current	$ 126,800	$ 62,100

Accounts Receivable And Contract With Customer, Asset, After Allowance For Credit Loss, Current

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- Definition

Accounts Receivable And Contract With Customer, Asset, Allowance For Credit Loss, Current

+ References

No definition available.

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- Definition

Accounts Receivable Related To Patent Administration Program

+ References

No definition available.

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- Definition

Composition Of Certain Financial Statement Captions [Abstract]

+ References

No definition available.

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- Definition

Trade Accounts Receivable

+ References

No definition available.

+ Details

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Namespace Prefix:	dlb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, before allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4531-111522

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Balance Type:	debit
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- Definition

Amount, before 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/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130531-203044

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130533-203044

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- 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

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