Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities - Schedule of Reconciliation of Cash and Cash Equivalents Inclusive of Restricted Cash (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Supplemental Cash Flow Elements [Abstract]
Restricted fiduciary cash	$ 1,457	$ 1,412
Non-restricted fiduciary cash	287	191
Total restricted and non-restricted fiduciary cash at the end of the period	1,744	1,603
Cash and cash equivalents	957	700	$ 756
Fiduciary cash	1,744		1,515
Total cash and cash equivalents inclusive of restricted cash at the end of the period	$ 2,701	$ 2,303	$ 2,271	$ 2,033