Composition of Certain Financial Statement Items Investment and Other Income, Net (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 25, 2018	Mar. 26, 2017	Mar. 25, 2018	Mar. 26, 2017
Investment Income, Net [Abstract]
Interest and dividend income	$ 154	$ 153	$ 280	$ 320
Net realized gains on marketable securities	3	67	13	206
Net realized gains on other investments	47	21	60	30
Impairment losses on marketable securities	0	(3)	(1)	(125)
Impairment losses on other investments	(11)	(2)	(19)	(23)
Net gains on derivative investments	10	13	9	20
Equity in net losses of investees	(17)	(14)	(38)	(11)
Net losses on foreign currency transactions	(90)	0	(93)	0
Investment and other income, net	$ 96	$ 235	$ 211	$ 417

This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the cost method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 325
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=75025870&loc=d3e40691-111596

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

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Amount of gain (loss) included in earnings for investments classified as other.

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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Amount before accretion (amortization) of purchase discount (premium) of interest income and dividend income on nonoperating securities.

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The aggregate amount of income from investments (for example, dividends) not considered a component of the entity's core operations.

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This item represents the total realized gain (loss) included in earnings for the period as a result of selling marketable securities categorized as trading, available-for-sale, or held-to-maturity.

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This element represents the amount of loss recognized for other than temporary impairments (OTTI) of investments in debt and equity securities.

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