Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Summary of Recorded Investment in Loans Modified in TDRs (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]
Financing receivable modifications recorded investment modified during period	$ 8,566	$ 10,398	$ 73,439	$ 32,647
Loans classified as TDRs, charge-offs	3,700	13,000	9,200	21,500
Commercial loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modifications recorded investment modified during period	8,566	10,398	71,613	32,325
Commercial loans | Software/internet
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modifications recorded investment modified during period	8,566	0	60,650	14,069
Commercial loans | Hardware
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modifications recorded investment modified during period	0	10,398	0	12,347
Commercial loans | Life science/healthcare
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modifications recorded investment modified during period	0	0	10,963	5,909
Consumer loans | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modifications recorded investment modified during period	0	0	1,826	322
Payment deferrals granted
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modifications recorded investment modified during period	6,400	$ 10,400	69,400	$ 32,600
Partial principal forgiveness
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing receivable modifications recorded investment modified during period	$ 2,200		$ 4,000