Loans and Allowance for Loan Losses - Allowance for Loan Losses Individually and Collectively Evaluated for Impairment (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	$ 50,373	$ 57,773
Individually evaluated for impairment, recorded investment in loans	167,147	182,684
Collectively evaluated for impairment, allowance for loan losses	190,192	159,840
Collectively evaluated for impairment, allowance for loan losses	18,945,118	16,559,386
Commercial Portfolio Segment \| Software and internet
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	24,815	34,098
Individually evaluated for impairment, recorded investment in loans	57,831	100,866
Collectively evaluated for impairment, allowance for loan losses	71,523	68,947
Collectively evaluated for impairment, allowance for loan losses	5,335,594	5,337,049
Commercial Portfolio Segment \| Hardware
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	6,041	3,160
Individually evaluated for impairment, recorded investment in loans	49,356	27,736
Collectively evaluated for impairment, allowance for loan losses	26,564	19,925
Collectively evaluated for impairment, allowance for loan losses	1,098,474	1,043,792
Commercial Portfolio Segment \| Private equity/venture capital
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	0	0
Individually evaluated for impairment, recorded investment in loans	0	0
Collectively evaluated for impairment, allowance for loan losses	51,943	35,282
Collectively evaluated for impairment, allowance for loan losses	7,412,238	5,467,577
Commercial Portfolio Segment \| Life science/healthcare
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	18,206	20,230
Individually evaluated for impairment, recorded investment in loans	54,341	51,354
Collectively evaluated for impairment, allowance for loan losses	18,842	16,346
Collectively evaluated for impairment, allowance for loan losses	1,678,576	1,659,288
Commercial Portfolio Segment \| Premium wine
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	128	90
Individually evaluated for impairment, recorded investment in loans	1,285	2,065
Collectively evaluated for impairment, allowance for loan losses	4,961	5,115
Collectively evaluated for impairment, allowance for loan losses	870,746	845,230
Commercial Portfolio Segment \| Other
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	42	52
Individually evaluated for impairment, recorded investment in loans	417	520
Collectively evaluated for impairment, allowance for loan losses	4,779	4,200
Collectively evaluated for impairment, allowance for loan losses	476,671	435,270
Commercial Portfolio Segment \| Commercial loans
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	49,232	57,630
Individually evaluated for impairment, recorded investment in loans	163,230	182,541
Collectively evaluated for impairment, allowance for loan losses	178,612	149,815
Collectively evaluated for impairment, allowance for loan losses	16,872,299	14,788,206
Consumer Portfolio Segment \| Consumer loans
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	1,141	143
Individually evaluated for impairment, recorded investment in loans	3,917	143
Collectively evaluated for impairment, allowance for loan losses	11,580	10,025
Collectively evaluated for impairment, allowance for loan losses	$ 2,072,819	$ 1,771,180

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

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