Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Composition of Loans, Net of Unearned Income (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned income on loans	$ 165,000	$ 173,000
Loans, net of unearned income	31,063,994	28,338,280
Commercial loans, excluding real estate secured and construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	26,662,081	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	6,009,518	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	1,357,617	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	16,293,556	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	2,381,822	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	234,555	249,266
Commercial loans, excluding real estate secured and construction | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	385,013	321,978
Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,803,987	3,363,803
Real estate secured loans | Premium wine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	749,259	710,397
Real estate secured loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,015,396	2,612,971
Real estate secured loans | Other real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	39,332	40,435
Construction loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	116,854	97,077
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,496,468	3,033,643
Consumer loans | Real estate secured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,015,396	2,612,971
Consumer loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 481,072	$ 420,672