Consolidations and Transfers of Financial Assets - Transfers of Financial Assets and Portfolio Securitizations (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Transfers of Financial Assets [Line Items]
Portfolio securitizations: unpaid principal balance	$ 35,300	$ 35,300	$ 102,000	$ 100,500
Unconsolidated VIEs
Transfers of Financial Assets [Line Items]
Retained interests: principal and interest received	66	$ 72	193	$ 220
Unconsolidated VIEs | Single Class MBS, REMIC & Megas
Transfers of Financial Assets [Line Items]
Retained interests: unpaid principal balance	672		672		$ 821
Retained interests: fair value	$ 1,100		$ 1,100		$ 1,300