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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment subsequently defaulted	$ 1,420	$ 790	$ 1,420	$ 1,374
Commercial Portfolio Segment | Software/internet
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment subsequently defaulted	1,234	0	1,234	584
Commercial Portfolio Segment | Premium wine
Financing Receivable, Modifications [Line Items]
Financing receivable modifications recorded investment subsequently defaulted	$ 186	$ 790	$ 186	$ 790