Accounting Policies and Supplemental Disclosures - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Accounting Policies [Abstract]
Cash paid for interest on debt, net of capitalized interest	$ 269	$ 402	$ 2,475	$ 1,684
Cash paid for operating leases	3,332	2,467	11,318	8,733
Cash paid for interest on finance leases	74	81	301	348
Cash paid for interest on financing obligations	64	59	201	208
Cash paid for income taxes, net of refunds	458	619	11,018	6,201
Assets acquired under operating leases	3,753	3,626	14,179	20,251
Property and equipment acquired under finance leases, net of remeasurements and modifications	42	8	676	517
Property and equipment recognized during the construction period of build-to-suit lease arrangements	37	131	263	1,953
Property and equipment derecognized after the construction period of build-to-suit lease arrangements, with the associated leases recognized as operating	$ 0	$ 720	$ 654	$ 5,845