Financial Instruments - Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Millions	Jun. 27, 2020	Sep. 28, 2019
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	$ 191,519	$ 204,977
Unrealized Gains	2,672	1,202
Unrealized Losses	(574)	(281)
Fair Value	193,617	205,898
Cash and Cash Equivalents	33,383	48,844
Current Marketable Securities	59,642	51,713
Non-Current Marketable Securities	100,592	105,341
Total cash, cash equivalents and marketable securities that were restricted from general use	18,300	18,900
Marketable securities pledged as collateral under repurchase agreements	5,300
Level 1
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	7,013	15,897
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	7,013	15,897
Cash and Cash Equivalents	7,013	15,897
Current Marketable Securities	0	0
Non-Current Marketable Securities	0	0
Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	164,253	176,876
Unrealized Gains	2,672	1,202
Unrealized Losses	(574)	(281)
Fair Value	166,351	177,797
Cash and Cash Equivalents	6,117	20,743
Current Marketable Securities	59,642	51,713
Non-Current Marketable Securities	100,592	105,341
Cash
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	20,253	12,204
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	20,253	12,204
Cash and Cash Equivalents	20,253	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	7,013	15,897
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	7,013	15,897
Cash and Cash Equivalents	7,013	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	23,207	30,293
Unrealized Gains	394	33
Unrealized Losses	0	(62)
Fair Value	23,601	30,264
Cash and Cash Equivalents	1,767	6,165
Current Marketable Securities	11,346	9,817
Non-Current Marketable Securities	10,488	14,282
U.S. agency securities \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	7,129	9,767
Unrealized Gains	9	1
Unrealized Losses	(2)	(3)
Fair Value	7,136	9,765
Cash and Cash Equivalents	59	6,489
Current Marketable Securities	2,737	2,249
Non-Current Marketable Securities	4,340	1,027
Non-U.S. government securities \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	19,324	19,821
Unrealized Gains	255	337
Unrealized Losses	(272)	(50)
Fair Value	19,307	20,108
Cash and Cash Equivalents	1	749
Current Marketable Securities	4,062	3,168
Non-Current Marketable Securities	15,244	16,191
Certificates of deposit and time deposits \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	10,247	4,041
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	10,247	4,041
Cash and Cash Equivalents	3,324	2,024
Current Marketable Securities	6,787	1,922
Non-Current Marketable Securities	136	95
Commercial paper \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	12,105	12,433
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	12,105	12,433
Cash and Cash Equivalents	936	5,193
Current Marketable Securities	11,169	7,240
Non-Current Marketable Securities	0	0
Corporate debt securities \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	78,747	85,383
Unrealized Gains	1,672	756
Unrealized Losses	(280)	(92)
Fair Value	80,139	86,047
Cash and Cash Equivalents	30	123
Current Marketable Securities	22,581	26,127
Non-Current Marketable Securities	57,528	59,797
Municipal securities \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	964	958
Unrealized Gains	20	8
Unrealized Losses	0	(1)
Fair Value	984	965
Cash and Cash Equivalents	0	0
Current Marketable Securities	43	68
Non-Current Marketable Securities	941	897
Mortgage- and asset-backed securities \| Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	12,530	14,180
Unrealized Gains	322	67
Unrealized Losses	(20)	(73)
Fair Value	12,832	14,174
Cash and Cash Equivalents	0	0
Current Marketable Securities	917	1,122
Non-Current Marketable Securities	$ 11,915	$ 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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