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		Dec. 26, 2015	Sep. 26, 2015	Dec. 27, 2014	Sep. 27, 2014
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost		$ 217,820	$ 206,420
Unrealized Gains		234	574
Unrealized Losses		(2,315)	(1,328)
Fair Value		215,739	205,666
Cash and cash equivalents		16,689	21,120	$ 19,478	$ 13,844
Short-term marketable securities		21,385	20,481
Long-term marketable securities		177,665	164,065
Cash
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost		11,152	11,389
Unrealized Gains		0	0
Unrealized Losses		0	0
Fair Value		11,152	11,389
Cash and cash equivalents		11,152	11,389
Short-term marketable securities		0	0
Long-term marketable securities		0	0
Level 1
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	[1]	5,289	3,570
Unrealized Gains	[1]	0	0
Unrealized Losses	[1]	(206)	(144)
Fair Value	[1]	5,083	3,426
Cash and cash equivalents	[1]	3,517	1,798
Short-term marketable securities	[1]	1,566	1,628
Long-term marketable securities	[1]	0	0
Level 1 | Money market funds
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	[1]	3,517	1,798
Unrealized Gains	[1]	0	0
Unrealized Losses	[1]	0	0
Fair Value	[1]	3,517	1,798
Cash and cash equivalents	[1]	3,517	1,798
Short-term marketable securities	[1]	0	0
Long-term marketable securities	[1]	0	0
Level 1 | Mutual funds
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	[1]	1,772	1,772
Unrealized Gains	[1]	0	0
Unrealized Losses	[1]	(206)	(144)
Fair Value	[1]	1,566	1,628
Cash and cash equivalents	[1]	0	0
Short-term marketable securities	[1]	1,566	1,628
Long-term marketable securities	[1]	0	0
Level 2
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	[2]	201,379	191,461
Unrealized Gains	[2]	234	574
Unrealized Losses	[2]	(2,109)	(1,184)
Fair Value	[2]	199,504	190,851
Cash and cash equivalents	[2]	2,020	7,933
Short-term marketable securities	[2]	19,819	18,853
Long-term marketable securities	[2]	177,665	164,065
Level 2 | U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	[2]	40,739	34,902
Unrealized Gains	[2]	43	181
Unrealized Losses	[2]	(108)	(1)
Fair Value	[2]	40,674	35,082
Cash and cash equivalents	[2]	203	0
Short-term marketable securities	[2]	1,602	3,498
Long-term marketable securities	[2]	38,869	31,584
Level 2 | U.S. agency securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	[2]	5,307	5,864
Unrealized Gains	[2]	2	14
Unrealized Losses	[2]	(10)	0
Fair Value	[2]	5,299	5,878
Cash and cash equivalents	[2]	469	841
Short-term marketable securities	[2]	865	767
Long-term marketable securities	[2]	3,965	4,270
Level 2 | Non-U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	[2]	6,530	6,356
Unrealized Gains	[2]	31	45
Unrealized Losses	[2]	(201)	(167)
Fair Value	[2]	6,360	6,234
Cash and cash equivalents	[2]	0	43
Short-term marketable securities	[2]	454	135
Long-term marketable securities	[2]	5,906	6,056
Level 2 | Certificates of deposit and time deposits
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	[2]	2,986	4,347
Unrealized Gains	[2]	0	0
Unrealized Losses	[2]	0	0
Fair Value	[2]	2,986	4,347
Cash and cash equivalents	[2]	258	2,065
Short-term marketable securities	[2]	1,424	1,405
Long-term marketable securities	[2]	1,304	877
Level 2 | Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	[2]	2,236	6,016
Unrealized Gains	[2]	0	0
Unrealized Losses	[2]	0	0
Fair Value	[2]	2,236	6,016
Cash and cash equivalents	[2]	1,089	4,981
Short-term marketable securities	[2]	895	1,035
Long-term marketable securities	[2]	252	0
Level 2 | Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	[2]	125,000	116,908
Unrealized Gains	[2]	132	242
Unrealized Losses	[2]	(1,684)	(985)
Fair Value	[2]	123,448	116,165
Cash and cash equivalents	[2]	1	3
Short-term marketable securities	[2]	14,463	11,948
Long-term marketable securities	[2]	108,984	104,214
Level 2 | Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	[2]	946	947
Unrealized Gains	[2]	3	5
Unrealized Losses	[2]	(1)	0
Fair Value	[2]	948	952
Cash and cash equivalents	[2]	0	0
Short-term marketable securities	[2]	28	48
Long-term marketable securities	[2]	920	904
Level 2 | Mortgage- and asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	[2]	17,635	16,121
Unrealized Gains	[2]	23	87
Unrealized Losses	[2]	(105)	(31)
Fair Value	[2]	17,553	16,177
Cash and cash equivalents	[2]	0	0
Short-term marketable securities	[2]	88	17
Long-term marketable securities	[2]	$ 17,465	$ 16,160

[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.