Loans and Allowance for Credit Losses - Activity in the Allowance for Credit Losses for Loans Held for Investment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		$ 70	$ 74	$ 67
Provision	$ 52	1	88	5
FX translation		1	1
Ending balance	141	$ 72	141	$ 72
Leveraged Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	83		61
Charge-offs(1)	(14)		(19)
Provision	43		70
FX translation	1		1
Ending balance	113		113
Other Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	10		10
Charge-offs(1)	0		0
Provision	10		10
FX translation	0		0
Ending balance	20		20
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	4		2
Charge-offs(1)	0		0
Provision	4		6
FX translation	0		0
Ending balance	8		8
Off-Balance Sheet Commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	22		19
Charge-offs(1)	0		0
Provision	(4)		(1)
FX translation	0		0
Ending balance	18		18
All Other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	5		1
Charge-offs(1)	0		0
Provision	(1)		3
FX translation	0		0
Ending balance	4		4
Total Credit Reserve
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	124		93
Charge-offs(1)	(14)		(19)
Provision	52		88
FX translation	1
Ending balance	$ 163		$ 163