Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Composition of Loans, Net of Unearned Income (Details) - USD ($) $ in Millions	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	$ 50,754		$ 45,181
ACL	(396)	$ (392)	(448)	$ (590)	$ (549)	$ (305)
Net loans	50,358		44,733
Global fund banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	30,630		25,543
Investor dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	5,328		4,972
ACL	(158)	(168)	(213)	(292)	(276)	(82)
Investor dependent | Early stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,565		1,486
ACL	(55)	(62)	(86)	(148)	(127)	(26)
Investor dependent | Mid stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,708		1,565
Investor dependent | Later stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	2,055		1,921
Cash flow dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	4,843		4,934
Cash flow dependent | Sponsor led buyout
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,917		1,989
Cash flow dependent | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	2,926		2,945
Private bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	5,297		4,901
ACL	(47)	$ (44)	(53)	$ (91)	$ (88)	$ (22)
Balance sheet dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	2,804		2,191
Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,002		1,053
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	7		28
SBA loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	$ 843		$ 1,559