Amount of net assets (liabilities).

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Variable Interest Entities - Re-securitizations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Transfers of securities to VIEs
U.S. GSEs and government agencies	$ 18,794	$ 12,505	$ 31,899	$ 15,222
U.S. GSEs and government agencies \| Nonconsolidated re-securitization VIEs
Variable Interest Entity [Line Items]
Interest in VIEs	$ 3,068		$ 3,068		$ 2,631