Loans and Allowance for Loan Losses - Recorded Investment in Loans Modified in TDRs (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	$ 110,371,000	$ 2,738,000	$ 13,848,000
Partial charge-offs on loans classified as TDRs	23,500,000	0	11,100,000
Commercial loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	110,371,000	2,738,000	13,842,000
Commercial loans | Software and internet
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	56,790,000	1,033,000	4,932,000
Commercial loans | Hardware
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	286,000	1,118,000	8,143,000
Commercial loans | Private equity/venture capital
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0	0	77,000
Commercial loans | Life science/healthcare
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	51,878,000	0	0
Commercial loans | Premium wine
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	898,000	587,000	0
Commercial loans | Other
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	519,000	0	690,000
Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0	0	6,000
Consumer loans | Other
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	$ 0	$ 0	$ 6,000