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	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	$ 53,067	$ 37,941
Individually evaluated for impairment, recorded investment in loans	185,523	170,074
Collectively evaluated for impairment, allowance for loan losses	248,821	242,962
Collectively evaluated for impairment, allowance for loan losses	29,024,050	28,168,206
Commercial loans
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	52,923	37,675
Individually evaluated for impairment, recorded investment in loans	179,880	165,835
Collectively evaluated for impairment, allowance for loan losses	230,026	223,291
Collectively evaluated for impairment, allowance for loan losses	25,757,132	25,138,802
Commercial loans \| Software/internet
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	25,284	28,527
Individually evaluated for impairment, recorded investment in loans	109,076	114,850
Collectively evaluated for impairment, allowance for loan losses	76,714	75,040
Collectively evaluated for impairment, allowance for loan losses	5,891,208	6,039,905
Commercial loans \| Hardware
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	8,389	1,253
Individually evaluated for impairment, recorded investment in loans	15,535	11,506
Collectively evaluated for impairment, allowance for loan losses	18,543	18,472
Collectively evaluated for impairment, allowance for loan losses	1,313,054	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	105,524	98,581
Collectively evaluated for impairment, allowance for loan losses	14,684,900	14,106,860
Commercial loans \| Life science/healthcare
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	17,722	7,484
Individually evaluated for impairment, recorded investment in loans	51,011	34,067
Collectively evaluated for impairment, allowance for loan losses	22,484	24,696
Collectively evaluated for impairment, allowance for loan losses	2,331,836	2,351,545
Commercial loans \| Premium wine
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	244	0
Individually evaluated for impairment, recorded investment in loans	1,028	1,301
Collectively evaluated for impairment, allowance for loan losses	3,754	3,355
Collectively evaluated for impairment, allowance for loan losses	988,556	958,362
Commercial loans \| Other
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	1,284	411
Individually evaluated for impairment, recorded investment in loans	3,230	411
Collectively evaluated for impairment, allowance for loan losses	3,007	3,147
Collectively evaluated for impairment, allowance for loan losses	547,578	459,079
Consumer loans
Financing Receivable, Impaired [Line Items]
Individually evaluated for impairment, allowance for loan losses	144	266
Individually evaluated for impairment, recorded investment in loans	5,643	4,239
Collectively evaluated for impairment, allowance for loan losses	18,795	19,671
Collectively evaluated for impairment, allowance for loan losses	$ 3,266,918	$ 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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