Summary of Significant Accounting Policies - Cash and Cash Equivalents, Program and Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 555	$ 570
Program cash	85	70
Restricted cash	4	2
Total cash and cash equivalents, program and restricted cash	$ 644	$ 642	$ 626	$ 765