Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Composition of Loans, Net of Unearned Income (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned income on loans	$ 161,000	$ 173,000
Loans, net of unearned income	29,209,573	28,338,280
Commercial loans, excluding real estate secured and construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	25,016,983	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	6,000,284	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	1,328,589	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	14,684,900	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	2,382,847	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	236,116	249,266
Commercial loans, excluding real estate secured and construction | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	384,247	321,978
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,601,841	3,363,803
Real estate secured loans | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	753,468	710,397
Real estate secured loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,808,707	2,612,971
Real estate secured loans | Other real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	39,666	40,435
Construction loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	126,895	97,077
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,272,561	3,033,643
Consumer loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,808,707	2,612,971
Consumer loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 463,854	$ 420,672