Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Average Impaired Loans, Broken out by Portfolio Segment and Class of Financing Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 160,347	$ 179,666
Interest income recognized on impaired loans	4,582	2,664
Commercial loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	153,181	175,280
Interest income recognized on impaired loans	4,528	2,649
Commercial loans | Software/internet
Financing Receivable, Impaired [Line Items]
Average impaired loans	88,628	112,493
Interest income recognized on impaired loans	2,813	1,513
Commercial loans | Hardware
Financing Receivable, Impaired [Line Items]
Average impaired loans	12,500	28,540
Interest income recognized on impaired loans	464	312
Commercial loans | Private equity/venture capital
Financing Receivable, Impaired [Line Items]
Average impaired loans	2,264	1,327
Interest income recognized on impaired loans	0	0
Commercial loans | Life science/healthcare
Financing Receivable, Impaired [Line Items]
Average impaired loans	44,827	30,144
Interest income recognized on impaired loans	919	756
Commercial loans | Premium wine
Financing Receivable, Impaired [Line Items]
Average impaired loans	2,912	2,605
Interest income recognized on impaired loans	311	68
Commercial loans | Other
Financing Receivable, Impaired [Line Items]
Average impaired loans	2,050	171
Interest income recognized on impaired loans	21	0
Consumer loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	7,166	4,386
Interest income recognized on impaired loans	54	15
Consumer loans | Other
Financing Receivable, Impaired [Line Items]
Average impaired loans	7	358
Interest income recognized on impaired loans	0	0
Consumer loans | Real estate secured loans
Financing Receivable, Impaired [Line Items]
Average impaired loans	7,159	4,028
Interest income recognized on impaired loans	$ 54	$ 15