Variable Interest Entities and Securitizations - Continuing Involvement in Securitization Related VIEs (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
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Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Securities held by third-party investors, non-mortgage	$ 9,054	$ 10,361
Receivables in the trust, non-mortgage	21,803	23,683
Cash balance of spread or reserve accounts, non-mortgage	0	0
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Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Securities held by third-party investors, non-mortgage	1,507	2,053
Receivables in the trust, non-mortgage	1,664	2,243
Cash balance of spread or reserve accounts, non-mortgage	$ 10	$ 10