Variable Interest Entities - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Maximum exposure to loss		$ 2,077	$ 3,457
Carrying value of structured note vehicle		3,684	4,611
Structured note vehicles [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Maximum exposure to loss		1,515	3,003
Loss on structured note settlement	$ 39
Carrying value of structured note vehicle		$ 1,524	$ 3,033
Trading Assets [Member] | Structured note vehicles [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Carrying value of structured note vehicle	$ 1,293