Comprehensive Income - Change in AOCI by Component (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 30, 2019	Mar. 31, 2018	Mar. 30, 2019	Mar. 31, 2018	Dec. 30, 2018	Sep. 30, 2018	Dec. 31, 2017	Oct. 01, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balances	$ 117,892	$ 140,199	$ 107,147	$ 134,047
Total other comprehensive income/(loss)	2,089	(1,945)	1,866	(2,636)
Ending balances	105,860	126,878	105,860	126,878
Total AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balances	(3,588)	(841)	(3,454)	(150)
Other comprehensive income/(loss) before reclassifications			2,291
Amounts reclassified from AOCI			49
Tax effect			(474)
Total other comprehensive income/(loss)	2,089	(1,945)	1,866	(2,636)
Cumulative effects of changes in accounting principles					$ 0	$ 89	$ (278)	$ (278)
Ending balances	(1,499)	$ (3,064)	(1,499)	$ (3,064)
Cumulative Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balances			(1,055)
Other comprehensive income/(loss) before reclassifications			90
Amounts reclassified from AOCI			0
Tax effect			6
Total other comprehensive income/(loss)			96
Ending balances	(959)		(959)
Unrealized Gains/Losses on Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balances			810
Other comprehensive income/(loss) before reclassifications			(533)
Amounts reclassified from AOCI			(34)
Tax effect			120
Total other comprehensive income/(loss)			(447)
Ending balances	363		363
Unrealized Gains/Losses on Marketable Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balances			(3,209)
Other comprehensive income/(loss) before reclassifications			2,734
Amounts reclassified from AOCI			83
Tax effect			(600)
Total other comprehensive income/(loss)			2,217
Ending balances	$ (903)		$ (903)
Accounting Standards Update 2016-01 | Total AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effects of changes in accounting principles						89
Accounting Standards Update 2016-01 | Cumulative Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effects of changes in accounting principles						0
Accounting Standards Update 2016-01 | Unrealized Gains/Losses on Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effects of changes in accounting principles						0
Accounting Standards Update 2016-01 | Unrealized Gains/Losses on Marketable Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effects of changes in accounting principles						$ 89