Summary Of Significant Accounting Policies (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 26, 2021	Mar. 27, 2020	Mar. 26, 2021	Mar. 27, 2020	Sep. 25, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 71,976		$ 71,976		$ 76,515
Total lease liabilities	76,478		76,478
Revenues	319,558	$ 351,815	709,432	$ 643,692
Gross margin	287,180	314,985	641,750	569,547
Provision for income taxes	(9,022)	(22,105)	(33,294)	(27,968)
Net income (loss) attributable to Dolby Laboratories, Inc.	$ 76,217	$ 88,496	$ 211,415	$ 137,249
Diluted (in usd per share)	$ 0.73	$ 0.86	$ 2.02	$ 1.33
Accounts receivable, net	$ 283,505		$ 283,505		180,340
Contract assets, net of allowance for credit losses of $189 and $0	233,379		233,379		161,357
Prepaid expenses and other current assets	47,305		47,305		53,022
Other non-current assets	87,546		87,546		91,245
Accrued liabilities	254,163		254,163		219,974
Contract liabilities	20,029		20,029		15,436
Non-current contract liabilities	23,369		23,369		24,342
Other non-current liabilities	118,559		118,559		122,154
Retained earnings	2,591,870		2,591,870		$ 2,443,138
Net income	$ 76,345	$ 88,674	219,035	$ 137,265
Deferred income taxes			(16,992)	(15,141)
Accounts receivable, net			(102,791)	(60,870)
Contract assets			(72,197)	(28,086)
Prepaid expenses and other assets			10,552	(16,068)
Accounts payable and other liabilities			26,926	(21,431)
Contract liabilities			3,589	452
Net cash provided by operating activities			$ 165,628	$ 96,899