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	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	$ 53,728	$ 37,941
Individually evaluated for impairment, recorded investment in loans	142,940	170,074
Collectively evaluated for impairment, allowance for loan losses	250,682	242,962
Collectively evaluated for impairment, allowance for loan losses	30,921,054	28,168,206
Commercial loans
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	53,577	37,675
Individually evaluated for impairment, recorded investment in loans	135,852	165,835
Collectively evaluated for impairment, allowance for loan losses	229,996	223,291
Collectively evaluated for impairment, allowance for loan losses	27,431,674	25,138,802
Commercial loans \| Software/internet
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	24,882	28,527
Individually evaluated for impairment, recorded investment in loans	81,480	114,850
Collectively evaluated for impairment, allowance for loan losses	73,320	75,040
Collectively evaluated for impairment, allowance for loan losses	5,928,038	6,039,905
Commercial loans \| Hardware
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	5,230	1,253
Individually evaluated for impairment, recorded investment in loans	9,923	11,506
Collectively evaluated for impairment, allowance for loan losses	18,814	18,472
Collectively evaluated for impairment, allowance for loan losses	1,347,694	1,223,051
Commercial loans \| 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	3,700
Collectively evaluated for impairment, allowance for loan losses	108,531	98,581
Collectively evaluated for impairment, allowance for loan losses	16,293,556	14,106,860
Commercial loans \| Life science/healthcare
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	22,161	7,484
Individually evaluated for impairment, recorded investment in loans	39,521	34,067
Collectively evaluated for impairment, allowance for loan losses	22,331	24,696
Collectively evaluated for impairment, allowance for loan losses	2,342,301	2,351,545
Commercial loans \| Premium wine
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	394	0
Individually evaluated for impairment, recorded investment in loans	2,339	1,301
Collectively evaluated for impairment, allowance for loan losses	3,649	3,355
Collectively evaluated for impairment, allowance for loan losses	981,475	958,362
Commercial loans \| Other
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	910	411
Individually evaluated for impairment, recorded investment in loans	2,589	411
Collectively evaluated for impairment, allowance for loan losses	3,351	3,147
Collectively evaluated for impairment, allowance for loan losses	538,610	459,079
Consumer loans
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	151	266
Individually evaluated for impairment, recorded investment in loans	7,088	4,239
Collectively evaluated for impairment, allowance for loan losses	20,686	19,671
Collectively evaluated for impairment, allowance for loan losses	$ 3,489,380	$ 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=118936363&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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