Variable Interest Entities - Additional Information (Details) - Structured Note Vehicles [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on structured note settlement	$ 39
Carrying value of structured note vehicle	1,524
Trading Assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Carrying value of structured note vehicle	$ 1,293	$ 501