Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Summary of Loans Modified in Troubled Debt Restructurings (TDRs) (Detail) $ in Thousands	6 Months Ended
Jun. 30, 2018 USD ($) troubled_debt_restructuring	Dec. 31, 2017 USD ($)
Financing Receivable, Modifications [Line Items]
Number of troubled debt restructurings \| troubled_debt_restructuring	20
Loans modified in TDRs	$ 128,869	$ 147,793
Unfunded commitments available for funding associated with TDRs	600
Commercial loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	128,544	147,370
Commercial loans \| Software/internet
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	50,202	73,455
Commercial loans \| Hardware
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	49,834	51,132
Commercial loans \| Private equity/venture capital
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	25,460	19,235
Commercial loans \| Premium wine
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	3,048	3,198
Consumer loans \| Other
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs	$ 325	$ 423

Total commitments available for funding to clients with financing receivables modified by troubled debt restructurings.

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+ References

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Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554

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