Summary of Significant Accounting Policies - Cash, Cash Equivalents, and Restricted Cash Reconciliation (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 7,933	$ 8,307	$ 2,882
Restricted cash included in prepaid expenses and other	163	192	212
Noncurrent assets:
Cash restricted for airport construction	473	1,556	636
Total cash, cash equivalents and restricted cash	$ 8,569	$ 10,055	$ 3,730	$ 2,748