Investments in Securities - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Schedule of Accumulated Other Comprehensive Income (Loss) [Abstract]
Net unrealized gains on AFS securities for which we have not recorded an allowance for credit losses	$ 12		$ 12		$ 74
Net unrealized gains (losses) on AFS securities for which we have recorded an allowance for credit losses	(2)		(2)		0
Total proceeds (excludes initial sale of securities from new portfolio securitizations)	0	$ 137	582	$ 258
Other	33		33		42
Accumulated other comprehensive income	$ 43		$ 43		$ 116