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
	Mar. 31, 2019	Mar. 31, 2018
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment modified during period	$ 5,677	$ 3,880
Loans classified as TDRs, charge-offs	2,200	0
Commercial loans
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment modified during period	5,677	3,554
Commercial loans | Software/internet
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment modified during period	677	756
Commercial loans | Hardware
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment modified during period	0	1,559
Commercial loans | Life science/healthcare
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment modified during period	5,000	1,239
Consumer loans | Other
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment modified during period	0	326
Payment deferrals granted
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment modified during period	$ 5,700	$ 3,900