Cash and Available-for-Sale Securities' Adjusted Cost, Gross Unrealized Gains, Gross Unrealized Losses and Fair Value Recorded as Cash and Cash Equivalents or Short-Term or Long-Term Marketable Securities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 28, 2015		Sep. 27, 2014		Mar. 29, 2014	Sep. 28, 2013
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	$ 193,400		$ 155,332
Unrealized Gains	749		418
Unrealized Losses	(610)		(511)
Fair Value	193,539		155,239
Cash and cash equivalents	14,489		13,844		18,949	14,259
Short-term marketable securities	18,607		11,233
Long-term marketable securities	160,443		130,162
Cash
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	9,879		10,232
Unrealized Gains	0		0
Unrealized Losses	0		0
Fair Value	9,879		10,232
Cash and cash equivalents	9,879		10,232
Short-term marketable securities	0		0
Long-term marketable securities	0		0
Level 1
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	3,841	[1]	4,077	[1]
Unrealized Gains	0	[1]	1	[1]
Unrealized Losses	(126)	[1]	(132)	[1]
Fair Value	3,715	[1]	3,946	[1]
Cash and cash equivalents	1,457	[1]	1,546	[1]
Short-term marketable securities	2,258	[1]	2,400	[1]
Long-term marketable securities	0	[1]	0	[1]
Level 1 | Money market funds
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	1,457	[1]	1,546	[1]
Unrealized Gains	0	[1]	0	[1]
Unrealized Losses	0	[1]	0	[1]
Fair Value	1,457	[1]	1,546	[1]
Cash and cash equivalents	1,457	[1]	1,546	[1]
Short-term marketable securities	0	[1]	0	[1]
Long-term marketable securities	0	[1]	0	[1]
Level 1 | Mutual funds
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	2,384	[1]	2,531	[1]
Unrealized Gains	0	[1]	1	[1]
Unrealized Losses	(126)	[1]	(132)	[1]
Fair Value	2,258	[1]	2,400	[1]
Cash and cash equivalents	0	[1]	0	[1]
Short-term marketable securities	2,258	[1]	2,400	[1]
Long-term marketable securities	0	[1]	0	[1]
Level 2
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	179,680	[2]	141,023	[2]
Unrealized Gains	749	[2]	417	[2]
Unrealized Losses	(484)	[2]	(379)	[2]
Fair Value	179,945	[2]	141,061	[2]
Cash and cash equivalents	3,153	[2]	2,066	[2]
Short-term marketable securities	16,349	[2]	8,833	[2]
Long-term marketable securities	160,443	[2]	130,162	[2]
Level 2 | U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	42,854	[2]	23,140	[2]
Unrealized Gains	145	[2]	15	[2]
Unrealized Losses	(12)	[2]	(9)	[2]
Fair Value	42,987	[2]	23,146	[2]
Cash and cash equivalents	0	[2]	12	[2]
Short-term marketable securities	1,791	[2]	607	[2]
Long-term marketable securities	41,196	[2]	22,527	[2]
Level 2 | U.S. agency securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	6,901	[2]	7,373	[2]
Unrealized Gains	11	[2]	3	[2]
Unrealized Losses	(2)	[2]	(11)	[2]
Fair Value	6,910	[2]	7,365	[2]
Cash and cash equivalents	585	[2]	652	[2]
Short-term marketable securities	1,056	[2]	157	[2]
Long-term marketable securities	5,269	[2]	6,556	[2]
Level 2 | Non-U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	7,114	[2]	6,925	[2]
Unrealized Gains	86	[2]	69	[2]
Unrealized Losses	(80)	[2]	(69)	[2]
Fair Value	7,120	[2]	6,925	[2]
Cash and cash equivalents	41	[2]	0	[2]
Short-term marketable securities	271	[2]	204	[2]
Long-term marketable securities	6,808	[2]	6,721	[2]
Level 2 | Certificates of deposit and time deposits
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	3,473	[2]	3,832	[2]
Unrealized Gains	0	[2]	0	[2]
Unrealized Losses	0	[2]	0	[2]
Fair Value	3,473	[2]	3,832	[2]
Cash and cash equivalents	1,163	[2]	1,230	[2]
Short-term marketable securities	1,252	[2]	1,233	[2]
Long-term marketable securities	1,058	[2]	1,369	[2]
Level 2 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	2,956	[2]	475	[2]
Unrealized Gains	0	[2]	0	[2]
Unrealized Losses	0	[2]	0	[2]
Fair Value	2,956	[2]	475	[2]
Cash and cash equivalents	1,364	[2]	166	[2]
Short-term marketable securities	1,592	[2]	309	[2]
Long-term marketable securities	0	[2]	0	[2]
Level 2 | Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	100,658	[2]	85,431	[2]
Unrealized Gains	427	[2]	296	[2]
Unrealized Losses	(370)	[2]	(241)	[2]
Fair Value	100,715	[2]	85,486	[2]
Cash and cash equivalents	0	[2]	6	[2]
Short-term marketable securities	10,325	[2]	6,298	[2]
Long-term marketable securities	90,390	[2]	79,182	[2]
Level 2 | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	942	[2]	940	[2]
Unrealized Gains	5	[2]	8	[2]
Unrealized Losses	(1)	[2]	0	[2]
Fair Value	946	[2]	948	[2]
Cash and cash equivalents	0	[2]	0	[2]
Short-term marketable securities	24	[2]	0	[2]
Long-term marketable securities	922	[2]	948	[2]
Level 2 | Mortgage- and asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	14,782	[2]	12,907	[2]
Unrealized Gains	75	[2]	26	[2]
Unrealized Losses	(19)	[2]	(49)	[2]
Fair Value	14,838	[2]	12,884	[2]
Cash and cash equivalents	0	[2]	0	[2]
Short-term marketable securities	38	[2]	25	[2]
Long-term marketable securities	$ 14,800	[2]	$ 12,859	[2]

[1] The fair value of Level 1 securities is estimated based on quoted prices in active markets for identical assets or liabilities.

[2] The fair value of Level 2 securities is estimated based on observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.