Financial Instruments - Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Millions	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016	Sep. 26, 2015
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	$ 241,180	$ 268,399
Unrealized Gains	209	1,278
Unrealized Losses	(4,289)	(782)
Fair Value	237,100	268,895
Cash and Cash Equivalents	25,913	20,289	$ 20,484	$ 21,120
Short-Term Marketable Securities	40,388	53,892
Long-Term Marketable Securities	170,799	194,714
Total cash, cash equivalents and marketable securities that were restricted from general use	20,300
Cash
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	11,575	7,982
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	11,575	7,982
Cash and Cash Equivalents	11,575	7,982
Short-Term Marketable Securities	0	0
Long-Term Marketable Securities	0	0
Level 1
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	8,882	7,333
Unrealized Gains	0	0
Unrealized Losses	(116)	(88)
Fair Value	8,766	7,245
Cash and Cash Equivalents	8,083	6,534
Short-Term Marketable Securities	683	711
Long-Term Marketable Securities	0	0
Level 1 \| Money market funds
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	8,083	6,534
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	8,083	6,534
Cash and Cash Equivalents	8,083	6,534
Short-Term Marketable Securities	0	0
Long-Term Marketable Securities	0	0
Level 1 \| Mutual funds
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	799	799
Unrealized Gains	0	0
Unrealized Losses	(116)	(88)
Fair Value	683	711
Cash and Cash Equivalents	0	0
Short-Term Marketable Securities	683	711
Long-Term Marketable Securities	0	0
Level 2
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	220,723	253,084
Unrealized Gains	209	1,278
Unrealized Losses	(4,173)	(694)
Fair Value	216,759	253,668
Cash and Cash Equivalents	6,255	5,773
Short-Term Marketable Securities	39,705	53,181
Long-Term Marketable Securities	170,799	194,714
Level 2 \| U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	47,296	55,254
Unrealized Gains	0	58
Unrealized Losses	(1,202)	(230)
Fair Value	46,094	55,082
Cash and Cash Equivalents	1,613	865
Short-Term Marketable Securities	7,606	17,228
Long-Term Marketable Securities	36,875	36,989
Level 2 \| U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	4,127	5,162
Unrealized Gains	0	2
Unrealized Losses	(48)	(9)
Fair Value	4,079	5,155
Cash and Cash Equivalents	1,732	1,439
Short-Term Marketable Securities	360	2,057
Long-Term Marketable Securities	1,987	1,659
Level 2 \| Non-U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	21,601	7,827
Unrealized Gains	49	210
Unrealized Losses	(250)	(37)
Fair Value	21,400	8,000
Cash and Cash Equivalents	0	9
Short-Term Marketable Securities	3,355	123
Long-Term Marketable Securities	18,045	7,868
Level 2 \| Certificates of deposit and time deposits
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	3,074	5,832
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	3,074	5,832
Cash and Cash Equivalents	1,247	1,142
Short-Term Marketable Securities	1,330	3,918
Long-Term Marketable Securities	497	772
Level 2 \| Commercial paper
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	2,573	3,640
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	2,573	3,640
Cash and Cash Equivalents	1,663	2,146
Short-Term Marketable Securities	910	1,494
Long-Term Marketable Securities	0	0
Level 2 \| Corporate securities
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	123,001	152,724
Unrealized Gains	152	969
Unrealized Losses	(2,038)	(242)
Fair Value	121,115	153,451
Cash and Cash Equivalents	0	172
Short-Term Marketable Securities	25,162	27,591
Long-Term Marketable Securities	95,953	125,688
Level 2 \| Municipal securities
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	946	961
Unrealized Gains	0	4
Unrealized Losses	(12)	(1)
Fair Value	934	964
Cash and Cash Equivalents	0	0
Short-Term Marketable Securities	178	114
Long-Term Marketable Securities	756	850
Level 2 \| Mortgage- and asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	18,105	21,684
Unrealized Gains	8	35
Unrealized Losses	(623)	(175)
Fair Value	17,490	21,544
Cash and Cash Equivalents	0	0
Short-Term Marketable Securities	804	656
Long-Term Marketable Securities	$ 16,686	$ 20,888

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

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Investments in debt and equity securities which are categorized neither as held-to-maturity nor trading and which are intended to be sold or mature more than one year from the balance sheet date or operating cycle, if longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Investments which are not defined as or included in marketable (debt, equity, or other) securities whose use is restricted in whole or in part, generally by contractual agreements or regulatory requirements. For use in an unclassified balance sheet.

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