Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Nonaccrual Loans with No Allowance for Credit Loss (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans	$ 50,607	$ 102,669	$ 133,623	$ 94,142
Nonaccrual Loans with no Allowance for Credit Loss	6,899	7,230
Private equity/venture capital
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans	0	0	5,947	3,700
Nonaccrual Loans with no Allowance for Credit Loss	0	0
Investor dependent
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans	45,037	34,719	63,936	23,752
Nonaccrual Loans with no Allowance for Credit Loss	3,630	734
Cash flow dependent
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans	13	62,266	54,927	56,690
Nonaccrual Loans with no Allowance for Credit Loss	0	2,782
SVB Private Bank
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans	4,857	5,480	3,809	3,919
Nonaccrual Loans with no Allowance for Credit Loss	3,269	3,714
Balance sheet dependent
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans	0	0	4,736	5,004
Nonaccrual Loans with no Allowance for Credit Loss	0	0
Premium wine
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans	700	204	268	285
Nonaccrual Loans with no Allowance for Credit Loss	0	0
Other
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans	0	0	0	792
Nonaccrual Loans with no Allowance for Credit Loss	0	0
Early stage | Investor dependent
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans	18,414	11,093	8,697	7,616
Nonaccrual Loans with no Allowance for Credit Loss	1,562	460
Mid stage | Investor dependent
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans	12,180	17,330	32,099	4,751
Nonaccrual Loans with no Allowance for Credit Loss	261	274
Later stage | Investor dependent
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans	14,443	6,296	23,140	11,385
Nonaccrual Loans with no Allowance for Credit Loss	1,807	0
Sponsor led buyout | Cash flow dependent
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans	0	44,585	38,237	39,534
Nonaccrual Loans with no Allowance for Credit Loss	0	0
Other | Cash flow dependent
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Loans	13	17,681	$ 16,690	$ 17,156
Nonaccrual Loans with no Allowance for Credit Loss	$ 0	$ 2,782