Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Allowance for Loan Losses Individually and Collectively Evaluated for Impairment (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	$ 61,225	$ 37,941
Individually evaluated for impairment, recorded investment in loans	201,107	170,074
Collectively evaluated for impairment, allowance for loan losses	238,926	242,962
Collectively evaluated for impairment, allowance for loan losses	28,649,338	28,168,206
Commercial loans \| Software/internet
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	22,770	28,527
Individually evaluated for impairment, recorded investment in loans	98,934	114,850
Collectively evaluated for impairment, allowance for loan losses	72,913	75,040
Collectively evaluated for impairment, allowance for loan losses	6,137,332	6,039,905
Commercial loans \| Hardware
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	5,311	1,253
Individually evaluated for impairment, recorded investment in loans	19,807	11,506
Collectively evaluated for impairment, allowance for loan losses	19,810	18,472
Collectively evaluated for impairment, allowance for loan losses	1,237,084	1,223,051
Commercial loans \| Private equity/venture capital
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	2,247	0
Individually evaluated for impairment, recorded investment in loans	5,947	3,700
Collectively evaluated for impairment, allowance for loan losses	95,213	98,581
Collectively evaluated for impairment, allowance for loan losses	14,302,130	14,106,860
Commercial loans \| Life science/healthcare
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	30,730	7,484
Individually evaluated for impairment, recorded investment in loans	67,371	34,067
Collectively evaluated for impairment, allowance for loan losses	25,084	24,696
Collectively evaluated for impairment, allowance for loan losses	2,455,360	2,351,545
Commercial loans \| Premium wine
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	0	0
Individually evaluated for impairment, recorded investment in loans	1,236	1,301
Collectively evaluated for impairment, allowance for loan losses	3,799	3,355
Collectively evaluated for impairment, allowance for loan losses	1,013,739	958,362
Commercial loans \| Other
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	4	411
Individually evaluated for impairment, recorded investment in loans	4	411
Collectively evaluated for impairment, allowance for loan losses	3,204	3,147
Collectively evaluated for impairment, allowance for loan losses	412,093	459,079
Commercial loans \| Commercial loans
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	61,062	37,675
Individually evaluated for impairment, recorded investment in loans	193,299	165,835
Collectively evaluated for impairment, allowance for loan losses	220,023	223,291
Collectively evaluated for impairment, allowance for loan losses	25,557,738	25,138,802
Consumer loans \| Consumer loans
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	163	266
Individually evaluated for impairment, recorded investment in loans	7,808	4,239
Collectively evaluated for impairment, allowance for loan losses	18,903	19,671
Collectively evaluated for impairment, allowance for loan losses	$ 3,091,600	$ 3,029,404

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&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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-Publisher FASB
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-Topic 310
-SubTopic 10
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