Financial Instruments - Consolidated Statements of Cash Flows Reconciliation (Details) - USD ($) $ in Millions	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Cash and cash equivalents	$ 40,380		$ 42,122
Restricted cash included in accounts receivable, net and other	265		233
Restricted cash included in other assets	22		22
Total cash, cash equivalents, and restricted cash shown in the consolidated statements of cash flows	$ 40,667	$ 34,155	$ 42,377	$ 37,842	$ 27,505	$ 36,410	$ 22,965