Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Composition of Loans, Net of Unearned Income (Details) - USD ($) $ in Millions	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	$ 61,487		$ 45,181
ACL	(398)	$ (396)	(448)	$ (513)	$ (590)	$ (305)
Net loans	61,089		44,733
Unearned income on loans	240		226
Credit cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	548		400
Construction loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	320		118
Global fund banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	34,120		25,543
ACL	(59)	(66)	(46)	(39)	(54)	(107)
Investor dependent
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	5,377		4,972
ACL	(138)	(158)	(213)	(263)	(292)	(82)
Investor dependent | Early stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,550		1,486
Investor dependent | Growth stage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	3,827		3,486
Cash flow dependent and innovation C&I (Commercial and Industrial)
Accounts, Notes, Loans and Financing Receivable [Line Items]
ACL	(109)	(119)	(125)	(121)	(123)	(81)
Cash flow dependent and innovation C&I (Commercial and Industrial) | Cash flow dependent - SLBO
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,895		1,989
Cash flow dependent and innovation C&I (Commercial and Industrial) | Innovation C&I
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	5,916		5,136
Private bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	8,370		4,901
ACL	(31)	(47)	(53)	(76)	(91)	(22)
CRE
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	2,753		0
ACL	(40)	0	0
Other C&I
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	1,259		0
ACL	(12)	0	0
Premium wine and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
ACL	(9)	$ (6)	(9)	(11)	(26)	(13)
Premium wine and other | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	980		1,053
Premium wine and other | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	252		28
PPP Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, amortized cost	565		1,559
ACL	$ 0		$ (2)	$ (3)	$ (4)	$ 0