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	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	$ 29,370,403	$ 28,511,312
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	28,393,270	27,492,604
Performing (Criticized)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	791,610	848,634
Performing Impaired (Criticized)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	88,882	75,932
Nonperforming Impaired (Nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	96,641	94,142
Commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	26,100,841	25,480,947
Commercial loans | Software/internet
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	6,044,350	6,209,978
Commercial loans | Hardware
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	1,337,198	1,245,800
Commercial loans | Private equity/venture capital
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	14,688,338	14,118,132
Commercial loans | Life science/healthcare
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	2,447,763	2,461,076
Commercial loans | Premium wine
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	990,139	960,553
Commercial loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	593,053	485,408
Commercial loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	25,141,567	24,488,572
Commercial loans | Pass | Software/internet
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	5,457,188	5,574,332
Commercial loans | Pass | Hardware
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	1,185,161	1,146,985
Commercial loans | Pass | Private equity/venture capital
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	14,688,329	14,098,281
Commercial loans | Pass | Life science/healthcare
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	2,310,262	2,291,356
Commercial loans | Pass | Premium wine
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	925,649	909,965
Commercial loans | Pass | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	574,978	467,653
Commercial loans | Performing (Criticized)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	779,394	826,540
Commercial loans | Performing (Criticized) | Software/internet
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	478,086	520,796
Commercial loans | Performing (Criticized) | Hardware
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	136,502	87,309
Commercial loans | Performing (Criticized) | Private equity/venture capital
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	9	16,151
Commercial loans | Performing (Criticized) | Life science/healthcare
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	86,490	135,653
Commercial loans | Performing (Criticized) | Premium wine
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	63,462	49,287
Commercial loans | Performing (Criticized) | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	14,845	17,344
Commercial loans | Performing Impaired (Criticized)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	88,882	75,612
Commercial loans | Performing Impaired (Criticized) | Software/internet
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	72,060	48,069
Commercial loans | Performing Impaired (Criticized) | Hardware
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	6,667	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	9,371	16,276
Commercial loans | Performing Impaired (Criticized) | Premium wine
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	784	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	90,998	90,223
Commercial loans | Nonperforming Impaired (Nonaccrual) | Software/internet
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	37,016	66,781
Commercial loans | Nonperforming Impaired (Nonaccrual) | Hardware
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	8,868	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	41,640	17,791
Commercial loans | Nonperforming Impaired (Nonaccrual) | Premium wine
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	244	284
Commercial loans | Nonperforming Impaired (Nonaccrual) | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	3,230	411
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	3,269,562	3,030,365
Consumer loans | Real estate secured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	2,805,321	2,609,645
Consumer loans | Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	464,241	420,720
Consumer loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	3,251,703	3,004,032
Consumer loans | Pass | Real estate secured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	2,787,853	2,584,261
Consumer loans | Pass | Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	463,850	419,771
Consumer loans | Performing (Criticized)
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	12,216	22,094
Consumer loans | Performing (Criticized) | Real estate secured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	11,838	21,145
Consumer loans | Performing (Criticized) | Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	378	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	5,643	3,919
Consumer loans | Nonperforming Impaired (Nonaccrual) | Real estate secured loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	5,630	3,919
Consumer loans | Nonperforming Impaired (Nonaccrual) | Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable	$ 13	$ 0