Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Credit Quality Indicators, Broken out by Portfolio Segment and Class of Financing Receivables (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	$ 31,229,003	$ 28,511,312
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	30,217,584	27,492,604
Performing (Criticized)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	868,479	848,634
Performing Impaired (Criticized)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	38,895	75,932
Nonperforming Impaired (Nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	104,045	94,142
Commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	27,735,519	25,480,947
Commercial loans | Software/internet
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	6,067,667	6,209,978
Commercial loans | Hardware
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	1,367,892	1,245,800
Commercial loans | Private equity/venture capital
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	16,310,084	14,118,132
Commercial loans | Life science/healthcare
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	2,447,193	2,461,076
Commercial loans | Premium wine
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	985,088	960,553
Commercial loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	557,595	485,408
Commercial loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	26,741,466	24,488,572
Commercial loans | Pass | Software/internet
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	5,454,896	5,574,332
Commercial loans | Pass | Hardware
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	1,251,074	1,146,985
Commercial loans | Pass | Private equity/venture capital
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	16,310,056	14,098,281
Commercial loans | Pass | Life science/healthcare
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	2,258,771	2,291,356
Commercial loans | Pass | Premium wine
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	928,817	909,965
Commercial loans | Pass | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	537,852	467,653
Commercial loans | Performing (Criticized)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	858,201	826,540
Commercial loans | Performing (Criticized) | Software/internet
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	531,291	520,796
Commercial loans | Performing (Criticized) | Hardware
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	106,895	87,309
Commercial loans | Performing (Criticized) | Private equity/venture capital
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	28	16,151
Commercial loans | Performing (Criticized) | Life science/healthcare
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	148,901	135,653
Commercial loans | Performing (Criticized) | Premium wine
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	53,932	49,287
Commercial loans | Performing (Criticized) | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	17,154	17,344
Commercial loans | Performing Impaired (Criticized)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	38,895	75,612
Commercial loans | Performing Impaired (Criticized) | Software/internet
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	25,588	48,069
Commercial loans | Performing Impaired (Criticized) | Hardware
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	4,482	10,250
Commercial loans | Performing Impaired (Criticized) | Private equity/venture capital
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	0	0
Commercial loans | Performing Impaired (Criticized) | Life science/healthcare
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	6,879	16,276
Commercial loans | Performing Impaired (Criticized) | Premium wine
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	1,946	1,017
Commercial loans | Performing Impaired (Criticized) | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	0	0
Commercial loans | Nonperforming Impaired (Nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	96,957	90,223
Commercial loans | Nonperforming Impaired (Nonaccrual) | Software/internet
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	55,892	66,781
Commercial loans | Nonperforming Impaired (Nonaccrual) | Hardware
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	5,441	1,256
Commercial loans | Nonperforming Impaired (Nonaccrual) | Private equity/venture capital
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	0	3,700
Commercial loans | Nonperforming Impaired (Nonaccrual) | Life science/healthcare
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	32,642	17,791
Commercial loans | Nonperforming Impaired (Nonaccrual) | Premium wine
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	393	284
Commercial loans | Nonperforming Impaired (Nonaccrual) | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	2,589	411
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	3,493,484	3,030,365
Consumer loans | Real estate secured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	3,012,047	2,609,645
Consumer loans | Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	481,437	420,720
Consumer loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	3,476,118	3,004,032
Consumer loans | Pass | Real estate secured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	2,994,694	2,584,261
Consumer loans | Pass | Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	481,424	419,771
Consumer loans | Performing (Criticized)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	10,278	22,094
Consumer loans | Performing (Criticized) | Real estate secured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	10,278	21,145
Consumer loans | Performing (Criticized) | Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	0	949
Consumer loans | Performing Impaired (Criticized)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	0	320
Consumer loans | Performing Impaired (Criticized) | Real estate secured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	0	320
Consumer loans | Performing Impaired (Criticized) | Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	0	0
Consumer loans | Nonperforming Impaired (Nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	7,088	3,919
Consumer loans | Nonperforming Impaired (Nonaccrual) | Real estate secured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	7,075	3,919
Consumer loans | Nonperforming Impaired (Nonaccrual) | Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	$ 13	$ 0