Loans and Allowance for Credit Losses - Activity in the Allowance for Credit Losses for Loans Held for Investment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 74	$ 67	$ 54
Charge-offs		(3)	(2)
Provision (reversal) for credit loss	88	10	15
Ending balance	122	74	$ 67
Leveraged Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	61
Charge-offs	(41)
Provision (reversal) for credit loss	70
Other	(7)
Ending balance	97	61
Other Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	10
Charge-offs	0
Provision (reversal) for credit loss	7
Other	0
Ending balance	17	10
Other Loans | Fund Finance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Ending balance	13
Other Loans | Other Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Ending balance	4
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	2
Charge-offs	0
Provision (reversal) for credit loss	6
Other	0
Ending balance	8	2
Held-to-Maturity Securities
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0
Charge-offs	0
Provision (reversal) for credit loss	3
Other	0
Ending balance	3	0
Off Balance Sheet Commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	19
Charge-offs	0
Provision (reversal) for credit loss	2
Other	(1)
Ending balance	22	19
All Other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1
Charge-offs	0
Provision (reversal) for credit loss	0
Other	0
Ending balance	1	1
Total Credit Reserve
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	93
Charge-offs	(41)
Provision (reversal) for credit loss	88
Other	(8)
Ending balance	$ 148	$ 93