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	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 28,511,312	$ 23,254,153
Pass
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	27,492,604	22,357,492
Performing (Criticized)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	848,634	721,800
Performing Impaired
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	75,932	55,602
Non Performing Impaired
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	94,142	119,259
Commercial loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	25,480,947	20,627,844
Commercial loans | Software and internet
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	6,209,978	6,232,725
Commercial loans | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,245,800	1,200,900
Commercial loans | Private equity/venture capital
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	14,118,132	9,961,121
Commercial loans | Life science/healthcare
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,461,076	1,867,960
Commercial loans | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	960,553	874,369
Commercial loans | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	485,408	490,769
Commercial loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	24,488,572	19,748,266
Commercial loans | Pass | Software and internet
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	5,574,332	5,655,739
Commercial loans | Pass | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,146,985	1,112,574
Commercial loans | Pass | Private equity/venture capital
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	14,098,281	9,955,082
Commercial loans | Pass | Life science/healthcare
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,291,356	1,720,613
Commercial loans | Pass | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	909,965	834,537
Commercial loans | Pass | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	467,653	469,721
Commercial loans | Performing (Criticized)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	826,540	707,320
Commercial loans | Performing (Criticized) | Software and internet
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	520,796	466,332
Commercial loans | Performing (Criticized) | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	87,309	51,976
Commercial loans | Performing (Criticized) | Private equity/venture capital
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	16,151	5,381
Commercial loans | Performing (Criticized) | Life science/healthcare
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	135,653	125,660
Commercial loans | Performing (Criticized) | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	49,287	36,955
Commercial loans | Performing (Criticized) | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	17,344	21,016
Commercial loans | Performing Impaired
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	75,612	55,602
Commercial loans | Performing Impaired | Software and internet
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	48,069	31,794
Commercial loans | Performing Impaired | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	10,250	20,165
Commercial loans | Performing Impaired | Private equity/venture capital
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	0	0
Commercial loans | Performing Impaired | Life science/healthcare
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	16,276	1,167
Commercial loans | Performing Impaired | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,017	2,476
Commercial loans | Performing Impaired | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	0	0
Commercial loans | Non Performing Impaired
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	90,223	116,656
Commercial loans | Non Performing Impaired | Software and internet
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	66,781	78,860
Commercial loans | Non Performing Impaired | Hardware
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	1,256	16,185
Commercial loans | Non Performing Impaired | Private equity/venture capital
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,700	658
Commercial loans | Non Performing Impaired | Life science/healthcare
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	17,791	20,520
Commercial loans | Non Performing Impaired | Premium wine
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	284	401
Commercial loans | Non Performing Impaired | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	411	32
Consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,030,365	2,626,309
Consumer loans | Real estate secured consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,609,645	2,297,857
Consumer loans | Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	420,720	328,452
Consumer loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,004,032	2,609,226
Consumer loans | Pass | Real estate secured consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	2,584,261	2,282,375
Consumer loans | Pass | Other Loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	419,771	326,851
Consumer loans | Performing (Criticized)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	22,094	14,480
Consumer loans | Performing (Criticized) | Real estate secured consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	21,145	13,301
Consumer loans | Performing (Criticized) | Other Loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	949	1,179
Consumer loans | Performing Impaired
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	320	0
Consumer loans | Performing Impaired | Real estate secured consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	320	0
Consumer loans | Performing Impaired | Other Loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	0	0
Consumer loans | Non Performing Impaired
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,919	2,603
Consumer loans | Non Performing Impaired | Real estate secured consumer loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	3,919	2,181
Consumer loans | Non Performing Impaired | Other Loans
Financing Receivable, Recorded Investment [Line Items]
Financing receivable	$ 0	$ 422