Comprehensive Income - Change in AOCI by Component (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances as of September 30, 2017	$ 134,047
Total other comprehensive income/(loss)	(691)	$ (389)
Balances as of December 30, 2017	140,199
Cumulative Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances as of September 30, 2017	(354)
Other comprehensive income/(loss) before reclassifications	41
Amounts reclassified from AOCI	0
Tax effect	(1)
Total other comprehensive income/(loss)	40
Balances as of December 30, 2017	(314)
Unrealized Gains/Losses on Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances as of September 30, 2017	(124)
Other comprehensive income/(loss) before reclassifications	154
Amounts reclassified from AOCI	123
Tax effect	(87)
Total other comprehensive income/(loss)	190
Balances as of December 30, 2017	66
Unrealized Gains/Losses on Marketable Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances as of September 30, 2017	328
Other comprehensive income/(loss) before reclassifications	(1,310)
Amounts reclassified from AOCI	(116)
Tax effect	505
Total other comprehensive income/(loss)	(921)
Balances as of December 30, 2017	(593)
Total AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances as of September 30, 2017	(150)
Other comprehensive income/(loss) before reclassifications	(1,115)
Amounts reclassified from AOCI	7
Tax effect	417
Total other comprehensive income/(loss)	(691)
Balances as of December 30, 2017	$ (841)