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
	Mar. 31, 2018	Mar. 31, 2017
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment subsequently defaulted	$ 3,032	$ 3,641
Commercial loans
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment subsequently defaulted	3,032	3,105
Commercial Portfolio Segment | Software/internet
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment subsequently defaulted	3,032	0
Commercial Portfolio Segment | Hardware
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment subsequently defaulted	0	3,105
Consumer Portfolio Segment [Member] | Other
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment subsequently defaulted	$ 0	$ 536