Significant Accounting Policies - Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 4,438	$ 4,154	$ 2,452
Restricted cash and cash equivalents	68	69	56
Total cash and cash equivalents, and restricted cash and cash equivalents presented in the consolidated statements of cash flows	$ 4,506	$ 4,223	$ 2,508	$ 2,926