General - Cash, Cash Equivalents and Restricted Cash Equivalents (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash and cash equivalents	$ 2,270	$ 2,008	$ 2,021
Restricted cash and restricted cash equivalents	183	170	269
Restricted cash and restricted cash equivalents included in long-term receivables and other assets, net	15		74
Cash, cash equivalents, restricted cash and restricted cash equivalents	$ 2,468	$ 2,194	$ 2,364	$ 3,574