Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Recorded Investment in Loans Modified in TDRs within Previous 12 months Subsequently Defaulted (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable, Troubled Debt Restructuring [Line Items]
TDRs modified within the previous 12 months that defaulted in the period	$ 48,257	$ 26,920	$ 48,257	$ 54,256
Commercial loans | Software/internet
Financing Receivable, Troubled Debt Restructuring [Line Items]
TDRs modified within the previous 12 months that defaulted in the period	37,294	18,911	37,294	41,568
Commercial loans | Hardware
Financing Receivable, Troubled Debt Restructuring [Line Items]
TDRs modified within the previous 12 months that defaulted in the period	0	2,100	0	5,549
Commercial loans | Life science/healthcare
Financing Receivable, Troubled Debt Restructuring [Line Items]
TDRs modified within the previous 12 months that defaulted in the period	$ 10,963	$ 5,909	$ 10,963	$ 7,139