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	Dec. 27, 2014		Sep. 27, 2014		Dec. 28, 2013	Sep. 28, 2013
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	$ 178,788		$ 155,332
Unrealized Gains	271		418
Unrealized Losses	(1,104)		(511)
Fair Value	177,955		155,239
Cash and cash equivalents	19,478		13,844		14,077	14,259
Short-term marketable securities	12,985		11,233
Long-term marketable securities	145,492		130,162
Cash
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	13,757		10,232
Unrealized Gains	0		0
Unrealized Losses	0		0
Fair Value	13,757		10,232
Cash and cash equivalents	13,757		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	5,890	[1]	4,077	[1]
Unrealized Gains	0	[1]	1	[1]
Unrealized Losses	(159)	[1]	(132)	[1]
Fair Value	5,731	[1]	3,946	[1]
Cash and cash equivalents	3,346	[1]	1,546	[1]
Short-term marketable securities	2,385	[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	3,346	[1]	1,546	[1]
Unrealized Gains	0	[1]	0	[1]
Unrealized Losses	0	[1]	0	[1]
Fair Value	3,346	[1]	1,546	[1]
Cash and cash equivalents	3,346	[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	2,544	[1]	2,531	[1]
Unrealized Gains	0	[1]	1	[1]
Unrealized Losses	(159)	[1]	(132)	[1]
Fair Value	2,385	[1]	2,400	[1]
Cash and cash equivalents	0	[1]	0	[1]
Short-term marketable securities	2,385	[1]	2,400	[1]
Long-term marketable securities	0	[1]	0	[1]
Level 2
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	159,141	[2]	141,023	[2]
Unrealized Gains	271	[2]	417	[2]
Unrealized Losses	(945)	[2]	(379)	[2]
Fair Value	158,467	[2]	141,061	[2]
Cash and cash equivalents	2,375	[2]	2,066	[2]
Short-term marketable securities	10,600	[2]	8,833	[2]
Long-term marketable securities	145,492	[2]	130,162	[2]
Level 2 | U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	35,107	[2]	23,140	[2]
Unrealized Gains	16	[2]	15	[2]
Unrealized Losses	(58)	[2]	(9)	[2]
Fair Value	35,065	[2]	23,146	[2]
Cash and cash equivalents	545	[2]	12	[2]
Short-term marketable securities	692	[2]	607	[2]
Long-term marketable securities	33,828	[2]	22,527	[2]
Level 2 | U.S. agency securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	6,788	[2]	7,373	[2]
Unrealized Gains	2	[2]	3	[2]
Unrealized Losses	(11)	[2]	(11)	[2]
Fair Value	6,779	[2]	7,365	[2]
Cash and cash equivalents	582	[2]	652	[2]
Short-term marketable securities	291	[2]	157	[2]
Long-term marketable securities	5,906	[2]	6,556	[2]
Level 2 | Non-U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	6,498	[2]	6,925	[2]
Unrealized Gains	58	[2]	69	[2]
Unrealized Losses	(105)	[2]	(69)	[2]
Fair Value	6,451	[2]	6,925	[2]
Cash and cash equivalents	0	[2]	0	[2]
Short-term marketable securities	177	[2]	204	[2]
Long-term marketable securities	6,274	[2]	6,721	[2]
Level 2 | Certificates of deposit and time deposits
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	2,778	[2]	3,832	[2]
Unrealized Gains	0	[2]	0	[2]
Unrealized Losses	0	[2]	0	[2]
Fair Value	2,778	[2]	3,832	[2]
Cash and cash equivalents	272	[2]	1,230	[2]
Short-term marketable securities	1,168	[2]	1,233	[2]
Long-term marketable securities	1,338	[2]	1,369	[2]
Level 2 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	1,159	[2]	475	[2]
Unrealized Gains	0	[2]	0	[2]
Unrealized Losses	0	[2]	0	[2]
Fair Value	1,159	[2]	475	[2]
Cash and cash equivalents	879	[2]	166	[2]
Short-term marketable securities	280	[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	92,371	[2]	85,431	[2]
Unrealized Gains	159	[2]	296	[2]
Unrealized Losses	(720)	[2]	(241)	[2]
Fair Value	91,810	[2]	85,486	[2]
Cash and cash equivalents	97	[2]	6	[2]
Short-term marketable securities	7,932	[2]	6,298	[2]
Long-term marketable securities	83,781	[2]	79,182	[2]
Level 2 | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	939	[2]	940	[2]
Unrealized Gains	4	[2]	8	[2]
Unrealized Losses	(1)	[2]	0	[2]
Fair Value	942	[2]	948	[2]
Cash and cash equivalents	0	[2]	0	[2]
Short-term marketable securities	0	[2]	0	[2]
Long-term marketable securities	942	[2]	948	[2]
Level 2 | Mortgage- and asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	13,501	[2]	12,907	[2]
Unrealized Gains	32	[2]	26	[2]
Unrealized Losses	(50)	[2]	(49)	[2]
Fair Value	13,483	[2]	12,884	[2]
Cash and cash equivalents	0	[2]	0	[2]
Short-term marketable securities	60	[2]	25	[2]
Long-term marketable securities	$ 13,423	[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.