Financial Instruments - Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Millions	Sep. 26, 2020	Sep. 28, 2019
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	$ 189,431	$ 204,977
Unrealized Gains	2,784	1,202
Unrealized Losses	(385)	(281)
Fair Value	191,830	205,898
Cash and Cash Equivalents	38,016	48,844
Current Marketable Securities	52,927	51,713
Non-Current Marketable Securities	100,887	105,341
Total marketable securities that were restricted from general use	18,600	18,900
Level 1
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	2,171	15,897
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	2,171	15,897
Cash and Cash Equivalents	2,171	15,897
Current Marketable Securities	0	0
Non-Current Marketable Securities	0	0
Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	169,487	176,876
Unrealized Gains	2,784	1,202
Unrealized Losses	(385)	(281)
Fair Value	171,886	177,797
Cash and Cash Equivalents	18,072	20,743
Current Marketable Securities	52,927	51,713
Non-Current Marketable Securities	100,887	105,341
Cash
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	17,773	12,204
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	17,773	12,204
Cash and Cash Equivalents	17,773	12,204
Current Marketable Securities	0	0
Non-Current Marketable Securities	0	0
Money market funds \| Level 1
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	2,171	15,897
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	2,171	15,897
Cash and Cash Equivalents	2,171	15,897
Current Marketable Securities	0	0
Non-Current Marketable Securities	0	0
U.S. Treasury securities \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	28,439	30,293
Unrealized Gains	331	33
Unrealized Losses	0	(62)
Fair Value	28,770	30,264
Cash and Cash Equivalents	8,580	6,165
Current Marketable Securities	11,972	9,817
Non-Current Marketable Securities	8,218	14,282
U.S. agency securities \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	8,604	9,767
Unrealized Gains	8	1
Unrealized Losses	0	(3)
Fair Value	8,612	9,765
Cash and Cash Equivalents	2,009	6,489
Current Marketable Securities	3,078	2,249
Non-Current Marketable Securities	3,525	1,027
Non-U.S. government securities \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	19,361	19,821
Unrealized Gains	275	337
Unrealized Losses	(186)	(50)
Fair Value	19,450	20,108
Cash and Cash Equivalents	255	749
Current Marketable Securities	3,329	3,168
Non-Current Marketable Securities	15,866	16,191
Certificates of deposit and time deposits \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	10,399	4,041
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	10,399	4,041
Cash and Cash Equivalents	4,043	2,024
Current Marketable Securities	6,246	1,922
Non-Current Marketable Securities	110	95
Commercial paper \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	11,226	12,433
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	11,226	12,433
Cash and Cash Equivalents	3,185	5,193
Current Marketable Securities	8,041	7,240
Non-Current Marketable Securities	0	0
Corporate debt securities \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	76,937	85,383
Unrealized Gains	1,834	756
Unrealized Losses	(175)	(92)
Fair Value	78,596	86,047
Cash and Cash Equivalents	0	123
Current Marketable Securities	19,687	26,127
Non-Current Marketable Securities	58,909	59,797
Municipal securities \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	1,001	958
Unrealized Gains	22	8
Unrealized Losses	0	(1)
Fair Value	1,023	965
Cash and Cash Equivalents	0	0
Current Marketable Securities	139	68
Non-Current Marketable Securities	884	897
Mortgage- and asset-backed securities \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	13,520	14,180
Unrealized Gains	314	67
Unrealized Losses	(24)	(73)
Fair Value	13,810	14,174
Cash and Cash Equivalents	0	0
Current Marketable Securities	435	1,122
Non-Current Marketable Securities	$ 13,375	$ 13,052

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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