Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Composition of Loans, Net of Unearned Income (Additional Information) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned income on loans	$ 222,000	$ 163,000
Loans, at amortized cost	38,413,891	33,164,636
Credit cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	329,000	395,000
Construction loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	118,000	183,000
SVB Private Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	4,424,899	3,492,269
Loans reported in Other under historical definitions	411,200
Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	1,081,963	1,062,264
Loans reported in Other under historical definitions	50,300
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	48,206	867,723
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	4,708,631	4,146,347
Real estate secured loans | SVB Private Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	3,816,948	3,325,617
Real estate secured loans | SVB Private Bank | Loans for personal residence
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	3,179,148	2,829,880
Real estate secured loans | SVB Private Bank | Loans to eligible employees
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	449,551	401,396
Real estate secured loans | SVB Private Bank | Home equity lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	50,929	55,461
Real estate secured loans | SVB Private Bank | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	137,320	38,880
Real estate secured loans | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	831,182	820,730
Real estate secured loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at amortized cost	$ 60,501	$ 0