Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Credit Quality Indicators, Broken out by Risk-Based Segments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	$ 35,968,085	$ 33,164,636
Loans, at gross basis		33,327,704
Nonperforming (Nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	50,607
Loans, at gross basis		102,669
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	34,782,203
Loans, at gross basis		32,361,879
Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	1,135,275
Loans, at gross basis		863,156
Private equity/venture capital
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	18,868,875	17,696,794
Loans, at gross basis		17,712,797
Private equity/venture capital | Nonperforming (Nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	0
Loans, at gross basis		0
Private equity/venture capital | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	18,868,764
Loans, at gross basis		17,708,550
Private equity/venture capital | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	111
Loans, at gross basis		4,247
Investor dependent
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	5,236,710	4,335,195
Loans, at gross basis		4,418,884
Investor dependent | Early stage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	1,806,011	1,624,221
Loans, at gross basis		1,653,425
Investor dependent | Mid stage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	1,399,209	1,047,398
Loans, at gross basis		1,066,783
Investor dependent | Later stage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	2,031,490	1,663,576
Loans, at gross basis		1,698,676
Investor dependent | Nonperforming (Nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	45,037
Loans, at gross basis		34,719
Investor dependent | Nonperforming (Nonaccrual) | Early stage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	18,414
Loans, at gross basis		11,093
Investor dependent | Nonperforming (Nonaccrual) | Mid stage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	12,180
Loans, at gross basis		17,330
Investor dependent | Nonperforming (Nonaccrual) | Later stage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	14,443
Loans, at gross basis		6,296
Investor dependent | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	4,598,851
Loans, at gross basis		3,850,585
Investor dependent | Pass | Early stage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	1,588,307
Loans, at gross basis		1,436,022
Investor dependent | Pass | Mid stage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	1,224,481
Loans, at gross basis		924,002
Investor dependent | Pass | Later stage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	1,786,063
Loans, at gross basis		1,490,561
Investor dependent | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	592,822
Loans, at gross basis		533,580
Investor dependent | Criticized | Early stage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	199,290
Loans, at gross basis		206,310
Investor dependent | Criticized | Mid stage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	162,548
Loans, at gross basis		125,451
Investor dependent | Criticized | Later stage
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	230,984
Loans, at gross basis		201,819
Cash flow dependent
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	4,877,302	4,424,238
Loans, at gross basis		4,455,867
Cash flow dependent | Sponsor led buyout
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	2,121,007	2,185,497
Loans, at gross basis		2,203,020
Cash flow dependent | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	2,756,295	2,238,741
Loans, at gross basis		2,252,847
Cash flow dependent | Nonperforming (Nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	13
Loans, at gross basis		62,266
Cash flow dependent | Nonperforming (Nonaccrual) | Sponsor led buyout
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	0
Loans, at gross basis		44,585
Cash flow dependent | Nonperforming (Nonaccrual) | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	13
Loans, at gross basis		17,681
Cash flow dependent | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	4,542,223
Loans, at gross basis		4,181,613
Cash flow dependent | Pass | Sponsor led buyout
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	1,952,061
Loans, at gross basis		2,039,847
Cash flow dependent | Pass | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	2,590,162
Loans, at gross basis		2,141,766
Cash flow dependent | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	335,066
Loans, at gross basis		211,988
Cash flow dependent | Criticized | Sponsor led buyout
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	168,946
Loans, at gross basis		118,588
Cash flow dependent | Criticized | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	166,120
Loans, at gross basis		93,400
SVB Private Bank
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	3,669,295	3,492,269
Loans, at gross basis		3,489,219
SVB Private Bank | Nonperforming (Nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	4,857
Loans, at gross basis		5,480
SVB Private Bank | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	3,639,776
Loans, at gross basis		3,472,138
SVB Private Bank | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	24,662
Loans, at gross basis		11,601
Balance sheet dependent
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	1,850,941	1,286,153
Loans, at gross basis		1,297,304
Balance sheet dependent | Nonperforming (Nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	0
Loans, at gross basis		0
Balance sheet dependent | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	1,725,273
Loans, at gross basis		1,231,961
Balance sheet dependent | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	125,668
Loans, at gross basis		65,343
Premium wine
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	1,056,927	1,062,264
Loans, at gross basis		1,063,512
Premium wine | Nonperforming (Nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	700
Loans, at gross basis		204
Premium wine | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	999,373
Loans, at gross basis		1,026,973
Premium wine | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	56,854
Loans, at gross basis		36,335
Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	408,035	867,723
Loans, at gross basis		890,121
Other | Nonperforming (Nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	0
Loans, at gross basis		0
Other | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	407,943
Loans, at gross basis		890,059
Other | Criticized
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, at amortized cost	$ 92
Loans, at gross basis		$ 62