Loans and Allowance for Credit Losses: Loans and Unfunded Credit Commitments - Composition of Loans, Net of Unearned Income (Additional Information) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	$ 68,665	$ 66,276
Private bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	9,235	8,743
CRE
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	2,595	2,670
Premium wine and other | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	997	985
Premium wine and other | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	319	317
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	11,766	11,456
Real estate secured loans | Private bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	8,029	7,659
Real estate secured loans | Private bank | Loans for personal residence
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	7,302	6,939
Real estate secured loans | Private bank | Loans to eligible employees
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	463	455
Real estate secured loans | Private bank | Home equity lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	130	130
Real estate secured loans | Private bank | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	134	135
Real estate secured loans | CRE
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	2,595	2,670
Real estate secured loans | CRE | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	130	148
Real estate secured loans | CRE | Multifamily and residential investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	980	1,021
Real estate secured loans | CRE | Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	511	524
Real estate secured loans | CRE | Office and medical
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	480	499
Real estate secured loans | CRE | Manufacturing, industrial and warehouse
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	353	336
Real estate secured loans | CRE | Hospitality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	141	142
Real estate secured loans | Premium wine and other | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	794	793
Real estate secured loans | Premium wine and other | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	$ 348	$ 334