Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Summary of the Aging of Loans Broken out by Risk-based Segments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Past due	$ 38,234
Current	36,688,988
Total	36,727,222	$ 33,164,636
Loans Past Due 90 Days or More Still Accruing Interest	76
Past due, at gross basis		191,587
Current, at gross basis		33,136,117
Loans, at gross basis		33,327,704
Loans Past Due 90 Days or More Still Accruing Interest, at gross basis		3,515
30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	15,230
Past due, at gross basis		137,375
60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	7,874
Past due, at gross basis		38,224
Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	15,130
Past due, at gross basis		15,988
Private equity/venture capital
Financing Receivable, Past Due [Line Items]
Past due	73
Current	17,901,044
Total	17,901,117	17,696,794
Loans Past Due 90 Days or More Still Accruing Interest	0
Past due, at gross basis		101,272
Current, at gross basis		17,611,525
Loans, at gross basis		17,712,797
Loans Past Due 90 Days or More Still Accruing Interest, at gross basis		3,150
Private equity/venture capital | 30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	54
Past due, at gross basis		97,739
Private equity/venture capital | 60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	10
Past due, at gross basis		383
Private equity/venture capital | Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	9
Past due, at gross basis		3,150
Investor dependent
Financing Receivable, Past Due [Line Items]
Past due	23,109
Current	5,115,767
Total	5,138,876	4,335,195
Loans Past Due 90 Days or More Still Accruing Interest	73
Past due, at gross basis		60,298
Current, at gross basis		4,358,586
Loans, at gross basis		4,418,884
Loans Past Due 90 Days or More Still Accruing Interest, at gross basis		0
Investor dependent | 30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	7,434
Past due, at gross basis		19,445
Investor dependent | 60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	7,373
Past due, at gross basis		29,561
Investor dependent | Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	8,302
Past due, at gross basis		11,292
Investor dependent | Early stage
Financing Receivable, Past Due [Line Items]
Past due	3,867
Current	1,793,709
Total	1,797,576	1,624,221
Loans Past Due 90 Days or More Still Accruing Interest	73
Past due, at gross basis		24,092
Current, at gross basis		1,629,333
Loans, at gross basis		1,653,425
Loans Past Due 90 Days or More Still Accruing Interest, at gross basis		0
Investor dependent | Early stage | 30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	742
Past due, at gross basis		1,307
Investor dependent | Early stage | 60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	316
Past due, at gross basis		22,062
Investor dependent | Early stage | Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	2,809
Past due, at gross basis		723
Investor dependent | Mid stage
Financing Receivable, Past Due [Line Items]
Past due	12,840
Current	1,422,932
Total	1,435,772	1,047,398
Loans Past Due 90 Days or More Still Accruing Interest	0
Past due, at gross basis		17,024
Current, at gross basis		1,049,759
Loans, at gross basis		1,066,783
Loans Past Due 90 Days or More Still Accruing Interest, at gross basis		0
Investor dependent | Mid stage | 30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	4,190
Past due, at gross basis		10,025
Investor dependent | Mid stage | 60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	3,157
Past due, at gross basis		6,999
Investor dependent | Mid stage | Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	5,493
Past due, at gross basis		0
Investor dependent | Later stage
Financing Receivable, Past Due [Line Items]
Past due	6,402
Current	1,899,126
Total	1,905,528	1,663,576
Loans Past Due 90 Days or More Still Accruing Interest	0
Past due, at gross basis		19,182
Current, at gross basis		1,679,494
Loans, at gross basis		1,698,676
Loans Past Due 90 Days or More Still Accruing Interest, at gross basis		0
Investor dependent | Later stage | 30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	2,502
Past due, at gross basis		8,113
Investor dependent | Later stage | 60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	3,900
Past due, at gross basis		500
Investor dependent | Later stage | Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	0
Past due, at gross basis		10,569
Cash flow dependent
Financing Receivable, Past Due [Line Items]
Past due	6,547
Current	4,838,699
Total	4,845,246	4,424,238
Loans Past Due 90 Days or More Still Accruing Interest	0
Past due, at gross basis		5,489
Current, at gross basis		4,450,378
Loans, at gross basis		4,455,867
Loans Past Due 90 Days or More Still Accruing Interest, at gross basis		0
Cash flow dependent | 30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	2,362
Past due, at gross basis		2,426
Cash flow dependent | 60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	197
Past due, at gross basis		3,061
Cash flow dependent | Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	3,988
Past due, at gross basis		2
Cash flow dependent | Sponsor led buyout
Financing Receivable, Past Due [Line Items]
Past due	60
Current	2,057,379
Total	2,057,439	2,185,497
Loans Past Due 90 Days or More Still Accruing Interest	0
Past due, at gross basis		0
Current, at gross basis		2,203,020
Loans, at gross basis		2,203,020
Loans Past Due 90 Days or More Still Accruing Interest, at gross basis		0
Cash flow dependent | Sponsor led buyout | 30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	46
Past due, at gross basis		0
Cash flow dependent | Sponsor led buyout | 60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	14
Past due, at gross basis		0
Cash flow dependent | Sponsor led buyout | Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	0
Past due, at gross basis		0
Cash flow dependent | Other
Financing Receivable, Past Due [Line Items]
Past due	6,487
Current	2,781,320
Total	2,787,807	2,238,741
Loans Past Due 90 Days or More Still Accruing Interest	0
Past due, at gross basis		5,489
Current, at gross basis		2,247,358
Loans, at gross basis		2,252,847
Loans Past Due 90 Days or More Still Accruing Interest, at gross basis		0
Cash flow dependent | Other | 30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	2,316
Past due, at gross basis		2,426
Cash flow dependent | Other | 60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	183
Past due, at gross basis		3,061
Cash flow dependent | Other | Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	3,988
Past due, at gross basis		2
SVB Private Bank
Financing Receivable, Past Due [Line Items]
Past due	3,350
Current	3,812,927
Total	3,816,277	3,492,269
Loans Past Due 90 Days or More Still Accruing Interest	0
Past due, at gross basis		10,175
Current, at gross basis		3,479,044
Loans, at gross basis		3,489,219
Loans Past Due 90 Days or More Still Accruing Interest, at gross basis		365
SVB Private Bank | 30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	601
Past due, at gross basis		6,582
SVB Private Bank | 60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	0
Past due, at gross basis		2,049
SVB Private Bank | Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	2,749
Past due, at gross basis		1,544
Balance sheet dependent
Financing Receivable, Past Due [Line Items]
Past due	5,032
Current	1,688,039
Total	1,693,071	1,286,153
Loans Past Due 90 Days or More Still Accruing Interest	0
Past due, at gross basis		2,731
Current, at gross basis		1,294,573
Loans, at gross basis		1,297,304
Loans Past Due 90 Days or More Still Accruing Interest, at gross basis		0
Balance sheet dependent | 30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	4,777
Past due, at gross basis		2,731
Balance sheet dependent | 60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	255
Past due, at gross basis		0
Balance sheet dependent | Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	0
Past due, at gross basis		0
Premium wine
Financing Receivable, Past Due [Line Items]
Past due	1
Current	1,039,455
Total	1,039,456	1,062,264
Loans Past Due 90 Days or More Still Accruing Interest	0
Past due, at gross basis		11,605
Current, at gross basis		1,051,907
Loans, at gross basis		1,063,512
Loans Past Due 90 Days or More Still Accruing Interest, at gross basis		0
Premium wine | 30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	1
Past due, at gross basis		8,435
Premium wine | 60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	0
Past due, at gross basis		3,170
Premium wine | Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	0
Past due, at gross basis		0
Other
Financing Receivable, Past Due [Line Items]
Past due	122
Current	457,112
Total	457,234	867,723
Loans Past Due 90 Days or More Still Accruing Interest	3
Past due, at gross basis		17
Current, at gross basis		890,104
Loans, at gross basis		890,121
Loans Past Due 90 Days or More Still Accruing Interest, at gross basis		0
Other | 30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	1
Past due, at gross basis		17
Other | 60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	39
Past due, at gross basis		0
Other | Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	82
Past due, at gross basis		0
SBA loans
Financing Receivable, Past Due [Line Items]
Past due	0
Current	1,835,945
Total	1,835,945	$ 0
Loans Past Due 90 Days or More Still Accruing Interest	0
SBA loans | 30 - 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	0
SBA loans | 60 - 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	0
SBA loans | Equal to or Greater Than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Past due	$ 0