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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		$ 72	$ 74	$ 67
Charge-offs		(2)		(2)
Provision	$ 0	2	88	7
Other		(1)	(5)	(1)
Ending balance	134	$ 71	134	$ 71
Leveraged Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	113		61
Charge-offs	(14)		(33)
Provision	3		73
Other	(4)		(5)
Ending balance	106		106
Other Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	20		10
Charge-offs	0		0
Provision	0		10
Other	0		0
Ending balance	20		20
Other Loans | Fund Finance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Ending balance	15		15
Other Loans | Other Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Ending balance	5		5
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	8		2
Charge-offs	0		0
Provision	0		6
Other	0		0
Ending balance	8		8
Held-to-Maturity Securities
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3		0
Charge-offs	0		0
Provision	0		3
Other	0		0
Ending balance	3		3
Off-Balance Sheet Commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	18		19
Charge-offs	0		0
Provision	(3)		(4)
Other	0		0
Ending balance	15		15
All Other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1		1
Charge-offs	0		0
Provision	0		0
Other	0		0
Ending balance	1		1
Total Credit Reserve
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	163		93
Charge-offs	(14)		(33)
Provision	0		88
Other	(4)
Ending balance	$ 153		$ 153