Loans and Allowance for Credit Losses - Net Loans (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	$ 26,860	$ 26,309
Allowance for loan losses	(141)	(74)	$ (72)	$ (70)	$ (67)
Loans, net of allowance	26,719	26,235
Loans, Excluding Unfunded Commitments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	26,860	26,309
Allowance for loan losses	(141)	(74)
Loans, net of allowance	26,719	26,235
Fund Finance | Securities Finance Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	1,448	2,537
Fund Finance | Municipal Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	933	848
Fund Finance | Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	97	26
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	1,944	1,766
Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	19,453	20,528
Domestic | Fund Finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	9,696	10,270
Overdrafts	4,455	3,256
Domestic | Fund Finance | 40 Act Funds
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	5,026	6,040
Domestic | Fund Finance | Private Equity Capital Call Finance Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	7,272	6,076
Domestic | Fund Finance | Business Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	820	932
Domestic | Leveraged loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	3,071	3,342
Domestic | Overdrafts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	2,292	1,739
Domestic | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	2,450	3,411
Domestic | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	1,944	1,766
Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	7,407	5,781
Foreign | Fund Finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	3,986	3,145
Foreign | Leveraged loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	1,230	1,119
Foreign | Overdrafts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	2,163	1,517
Foreign | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross	$ 28	$ 0