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	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Troubled Debt Restructuring [Line Items]
TDRs modified within the previous 12 months that defaulted in the period	$ 47,933	$ 0	$ 0
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	0	0
Commercial loans | Life science/healthcare
Financing Receivable, Troubled Debt Restructuring [Line Items]
TDRs modified within the previous 12 months that defaulted in the period	$ 10,639	$ 0	$ 0