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	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 29,020,519	$ 28,511,312
Pass
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	27,891,991	27,492,604
Performing (Criticized)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	927,421	848,634
Performing Impaired (Criticized)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	67,484	75,932
Nonperforming Impaired (Nonaccrual)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	133,623	94,142
Commercial loans | Software/internet
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	6,287,367	6,209,978
Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,266,082	1,245,800
Commercial loans | Private equity/venture capital
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	14,315,660	14,118,132
Commercial loans | Life science/healthcare
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,593,914	2,461,076
Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,015,704	960,553
Commercial loans | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	445,412	485,408
Commercial loans | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	25,924,139	25,480,947
Commercial loans | Pass | Software/internet
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	5,619,634	5,574,332
Commercial loans | Pass | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,096,461	1,146,985
Commercial loans | Pass | Private equity/venture capital
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	14,306,933	14,098,281
Commercial loans | Pass | Life science/healthcare
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,422,438	2,291,356
Commercial loans | Pass | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	945,712	909,965
Commercial loans | Pass | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	425,012	467,653
Commercial loans | Pass | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	24,816,190	24,488,572
Commercial loans | Performing (Criticized) | Software/internet
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	568,799	520,796
Commercial loans | Performing (Criticized) | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	149,814	87,309
Commercial loans | Performing (Criticized) | Private equity/venture capital
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,780	16,151
Commercial loans | Performing (Criticized) | Life science/healthcare
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	104,105	135,653
Commercial loans | Performing (Criticized) | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	68,756	49,287
Commercial loans | Performing (Criticized) | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	20,396	17,344
Commercial loans | Performing (Criticized) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	914,650	826,540
Commercial loans | Performing Impaired (Criticized) | Software/internet
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	36,336	48,069
Commercial loans | Performing Impaired (Criticized) | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	11,753	10,250
Commercial loans | Performing Impaired (Criticized) | Private equity/venture capital
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	0	0
Commercial loans | Performing Impaired (Criticized) | Life science/healthcare
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	14,427	16,276
Commercial loans | Performing Impaired (Criticized) | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	968	1,017
Commercial loans | Performing Impaired (Criticized) | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	0	0
Commercial loans | Performing Impaired (Criticized) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	63,484	75,612
Commercial loans | Nonperforming Impaired (Nonaccrual) | Software/internet
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	62,598	66,781
Commercial loans | Nonperforming Impaired (Nonaccrual) | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	8,054	1,256
Commercial loans | Nonperforming Impaired (Nonaccrual) | Private equity/venture capital
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	5,947	3,700
Commercial loans | Nonperforming Impaired (Nonaccrual) | Life science/healthcare
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	52,944	17,791
Commercial loans | Nonperforming Impaired (Nonaccrual) | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	268	284
Commercial loans | Nonperforming Impaired (Nonaccrual) | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	4	411
Commercial loans | Nonperforming Impaired (Nonaccrual) | Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	129,815	90,223
Consumer loans | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,675,719	2,609,645
Consumer loans | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	420,661	420,720
Consumer loans | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,096,380	3,030,365
Consumer loans | Pass | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,656,069	2,584,261
Consumer loans | Pass | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	419,732	419,771
Consumer loans | Pass | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,075,801	3,004,032
Consumer loans | Performing (Criticized) | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	11,856	21,145
Consumer loans | Performing (Criticized) | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	915	949
Consumer loans | Performing (Criticized) | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	12,771	22,094
Consumer loans | Performing Impaired (Criticized) | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	4,000	320
Consumer loans | Performing Impaired (Criticized) | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	0	0
Consumer loans | Performing Impaired (Criticized) | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	4,000	320
Consumer loans | Nonperforming Impaired (Nonaccrual) | Real estate secured loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,794	3,919
Consumer loans | Nonperforming Impaired (Nonaccrual) | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	14	0
Consumer loans | Nonperforming Impaired (Nonaccrual) | Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 3,808	$ 3,919