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	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Supplemental Cash Flow Elements [Abstract]
Restricted fiduciary cash	$ 1,674	$ 1,570
Non-restricted fiduciary cash	352	257
Total restricted and non-restricted fiduciary cash at the end of the period	2,026	1,827
Cash and cash equivalents	8,893	675	$ 1,107
Fiduciary cash	2,026		1,867
Total cash and cash equivalents inclusive of restricted cash at the end of the period	$ 10,919	$ 2,502	$ 2,974	$ 2,303