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	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Supplemental Cash Flow Elements [Abstract]
Restricted fiduciary cash	$ 1,365	$ 1,412
Non-restricted fiduciary cash	204	191
Total restricted and non-restricted fiduciary cash at the end of the period	1,569	1,603
Cash and cash equivalents	581	700	$ 563
Fiduciary cash	1,569		1,380
Total cash and cash equivalents inclusive of restricted cash at the end of the period	$ 2,150	$ 2,303	$ 1,943	$ 2,033