Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Impaired Loans and Allowance for Loan Losses, Broken out by Portfolio Segment and Class of Financing Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Total carrying value of impaired loans	$ 153,009	$ 170,074
Total unpaid principal of impaired loans	214,036	199,908
Impaired Financing Receivables With Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired loans for which there is a related allowance for loan losses	95,438	73,002
Impaired Financing Receivables With No Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired loans for which there is no related allowance for loan losses	57,571	97,072
Commercial loans
Financing Receivable, Impaired [Line Items]
Total carrying value of impaired loans	147,529	165,835
Total unpaid principal of impaired loans	205,509	193,939
Commercial loans | Software/internet
Financing Receivable, Impaired [Line Items]
Impaired loans for which there is a related allowance for loan losses	64,100	49,625
Impaired loans for which there is no related allowance for loan losses	31,472	65,225
Total carrying value of impaired loans	95,572	114,850
Total unpaid principal of impaired loans	109,736	131,858
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Impaired loans for which there is a related allowance for loan losses	2,143	1,256
Impaired loans for which there is no related allowance for loan losses	3,315	10,250
Total carrying value of impaired loans	5,458	11,506
Total unpaid principal of impaired loans	10,049	12,159
Commercial loans | Private equity/venture capital
Financing Receivable, Impaired [Line Items]
Impaired loans for which there is a related allowance for loan losses	0	0
Impaired loans for which there is no related allowance for loan losses	0	3,700
Total carrying value of impaired loans	0	3,700
Total unpaid principal of impaired loans	0	3,700
Commercial loans | Life science/healthcare
Financing Receivable, Impaired [Line Items]
Impaired loans for which there is a related allowance for loan losses	25,941	17,791
Impaired loans for which there is no related allowance for loan losses	5,671	16,276
Total carrying value of impaired loans	31,612	34,067
Total unpaid principal of impaired loans	70,600	44,446
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Impaired loans for which there is a related allowance for loan losses	204	0
Impaired loans for which there is no related allowance for loan losses	11,718	1,301
Total carrying value of impaired loans	11,922	1,301
Total unpaid principal of impaired loans	12,010	1,365
Commercial loans | Other
Financing Receivable, Impaired [Line Items]
Impaired loans for which there is a related allowance for loan losses	1,284	411
Impaired loans for which there is no related allowance for loan losses	1,681	0
Total carrying value of impaired loans	2,965	411
Total unpaid principal of impaired loans	3,114	411
Commercial loans | Impaired Financing Receivables With Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired loans for which there is a related allowance for loan losses	93,672	69,083
Commercial loans | Impaired Financing Receivables With No Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired loans for which there is no related allowance for loan losses	53,857	96,752
Consumer loans
Financing Receivable, Impaired [Line Items]
Total carrying value of impaired loans	5,480	4,239
Total unpaid principal of impaired loans	8,527	5,969
Consumer loans | Real estate secured loans
Financing Receivable, Impaired [Line Items]
Impaired loans for which there is a related allowance for loan losses	1,766	3,919
Impaired loans for which there is no related allowance for loan losses	3,714	320
Total carrying value of impaired loans	5,480	4,239
Total unpaid principal of impaired loans	8,527	5,969
Consumer loans | Impaired Financing Receivables With Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired loans for which there is a related allowance for loan losses	1,766	3,919
Consumer loans | Impaired Financing Receivables With No Related Allowance
Financing Receivable, Impaired [Line Items]
Impaired loans for which there is no related allowance for loan losses	$ 3,714	$ 320