Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Composition of Loans, Net of Unearned Income (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned income on loans	$ 163,000	$ 173,000
Loans, net of unearned income	33,164,636	28,338,280
Commercial loans, excluding real estate secured and construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	28,428,121	24,456,728
Commercial loans, excluding real estate secured and construction | Software/internet
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	6,199,548	6,154,755
Commercial loans, excluding real estate secured and construction | Hardware
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,371,159	1,234,557
Commercial loans, excluding real estate secured and construction | Private equity/venture capital
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	17,801,324	14,110,560
Commercial loans, excluding real estate secured and construction | Life science/healthcare
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,368,048	2,385,612
Commercial loans, excluding real estate secured and construction | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	267,487	249,266
Commercial loans, excluding real estate secured and construction | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	420,555	321,978
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	4,146,347	3,363,803
Real estate secured loans | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	820,730	710,397
Real estate secured loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	38,880	40,435
Real estate secured loans | Construction loans, premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	83,000	99,000
Construction loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	100,219	97,077
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,776,686	3,033,643
Consumer loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,286,737	2,612,971
Consumer loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 489,949	$ 420,672