Summary Of Significant Accounting Policies (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 29, 2019	Mar. 30, 2018	Mar. 29, 2019	Mar. 30, 2018	Sep. 28, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 338,258	$ 299,722	$ 640,634	$ 599,249
Gross margin	301,683	268,695	565,430	537,329
Provision for income taxes	(36,427)	(22,432)	(12,323)	(172,137)
Net income (loss) attributable to Dolby Laboratories, Inc.	$ 73,440	$ 65,216	$ 171,659	$ 11,914
Diluted (in usd per share)	$ 0.70	$ 0.61	$ 1.63	$ 0.11
Accounts receivable, net	$ 178,617		$ 178,617		$ 166,133
Contract assets	244,917		244,917		165,959
Prepaid expenses and other current assets	44,050		44,050		34,890
Deferred taxes	113,409		113,409		74,766
Accrued liabilities	230,708		230,708		243,128
Contract liabilities	20,014		20,014		17,468
Non-current contract liabilities	24,445		24,445		25,887
Retained earnings	2,361,607		2,361,607		2,313,539
Net income	$ 73,575	$ 65,350	171,933	$ 12,192
Deferred income taxes			(38,548)	36,475
Accounts receivable			(14,221)	(39,296)
Contract assets			(78,949)	(44,172)
Prepaid expenses and other assets			(15,273)	(12,647)
Accounts payable and other liabilities			(14,190)	(35,530)
Contract liabilities			1,061	1,047
Net cash provided by operating activities			$ 105,844	98,041
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		301,355		589,152
Gross margin		270,396		527,317
Provision for income taxes		18,718		185,030
Net income (loss) attributable to Dolby Laboratories, Inc.		$ 70,631		$ (10,991)
Diluted (in usd per share)		$ 0.66		$ (0.11)
Accounts receivable, net					137,151
Contract assets					0
Prepaid expenses and other current assets					35,209
Deferred taxes					101,070
Accrued liabilities					223,594
Contract liabilities					23,931
Non-current contract liabilities					40,064
Retained earnings					2,139,154
Net income				$ (10,713)
Deferred income taxes				48,332
Accounts receivable				(69,018)
Contract assets				0
Prepaid expenses and other assets				(12,732)
Accounts payable and other liabilities				(38,124)
Contract liabilities				324
Net cash provided by operating activities				98,041
Restatement Adjustment | Effect of Adopting ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues		$ (1,633)		10,097
Gross margin		(1,701)		10,012
Provision for income taxes		(3,714)		12,893
Net income (loss) attributable to Dolby Laboratories, Inc.		$ (5,415)		$ 22,905
Diluted (in usd per share)		$ (0.05)		$ 0.22
Accounts receivable, net					28,982
Contract assets					165,959
Prepaid expenses and other current assets					(319)
Deferred taxes					(26,304)
Accrued liabilities					19,534
Contract liabilities					(6,463)
Non-current contract liabilities					(14,177)
Retained earnings					$ 174,385
Net income				$ 22,905
Deferred income taxes				(11,857)
Accounts receivable				29,722
Contract assets				(44,172)
Prepaid expenses and other assets				85
Accounts payable and other liabilities				2,594
Contract liabilities				723
Net cash provided by operating activities				$ 0