Segment Information - Reportable Segments and Reconciliation to Consolidated Net Income (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($) segment	Mar. 31, 2019 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment	3
Segment Reporting Disclosure [Line Items]
Net sales	$ 75,452	$ 59,700
Operating expenses	71,463	55,280
Operating income (loss)	3,989	4,420
Total non-operating income (expense)	(606)	(19)
Provision for income taxes	(744)	(836)
Equity-method investment activity, net of tax	(104)	(4)
Net income	2,535	3,561	$ 10,563	$ 12,005
North America
Segment Reporting Disclosure [Line Items]
Net sales	46,127	35,812
Operating expenses	44,815	33,525
Operating income (loss)	1,312	2,287
International
Segment Reporting Disclosure [Line Items]
Net sales	19,106	16,192
Operating expenses	19,504	16,282
Operating income (loss)	(398)	(90)
AWS
Segment Reporting Disclosure [Line Items]
Net sales	10,219	7,696
Operating expenses	7,144	5,473
Operating income (loss)	$ 3,075	$ 2,223