Other Assets - Schedule of Other Assets (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Other Assets [Abstract]
Property and equipment at cost	$ 2,190	$ 2,153
Accumulated depreciation	(923)	(871)
Net property and equipment	1,267	1,282
Proportional amortization investments	2,034	1,866
Net deferred tax assets	1,468	1,224
Accrued interest, fees, and rent receivables	945	935
Nonmarketable equity investments	789	886
Goodwill	669	669	$ 822
Equity-method investments	658	651
Restricted cash and cash equivalents	399	87
Restricted cash held for securitization trusts	289	407
Other accounts receivable	203	189
Operating lease right-of-use assets	85	90
Net intangible assets	58	73
Other assets	1,043	1,036
Total other assets	$ 9,907	$ 9,395
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Total other assets	Total other assets