Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Summary of Loans Modified in Troubled Debt Restructurings (TDRs) by Portfolio Segment and Class of Financing Receivables (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) troubled_debt_restructuring	Dec. 31, 2017 USD ($) troubled_debt_restructuring
Financing Receivable, Modifications [Line Items]
Number of TDRs | troubled_debt_restructuring	17	22
Loans modified in TDRs	$ 83,695	$ 147,793
Commercial loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	83,375	147,370
Commercial loans | Software and internet
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	58,089	73,455
Commercial loans | Hardware
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	9,665	51,132
Commercial loans | Private Equity And Venture Capital Financing Receivable [Member]
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	0	350
Commercial loans | Life science/healthcare
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	12,738	19,235
Commercial loans | Premium wine
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	2,883	3,198
Consumer loans | Other
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	$ 320	$ 423