Note Allowance for loan losses (T D R that subsequently defaulted) (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) loans	Mar. 31, 2016 USD ($) loans
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Loan count | loans	214	186
Recorded investment as of first default date | $	$ 7,340	$ 8,300
CRE non-owner occupied
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Loan count | loans	1	2
Recorded investment as of first default date | $	$ 262	$ 327
CRE owner occupied
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Loan count | loans	1	6
Recorded investment as of first default date | $	$ 267	$ 2,456
Commercial and industrial
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Loan count | loans	2
Recorded investment as of first default date | $	$ 544
Mortgages
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Loan count | loans	36	27
Recorded investment as of first default date | $	$ 3,695	$ 3,235
Leasing
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Loan count | loans	1
Recorded investment as of first default date | $	$ 45
Credit cards
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Loan count | loans	128	106
Recorded investment as of first default date | $	$ 1,349	$ 1,122
Home equity lines of credit
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Loan count | loans	1
Recorded investment as of first default date | $	$ 97
Personal
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Loan count | loans	42	43
Recorded investment as of first default date | $	$ 1,024	$ 1,139
Auto
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Loan count | loans	2	1
Recorded investment as of first default date | $	$ 57	$ 17
Other
Troubled Debt Restructuring, Debtor, Current Period [Line Items]
Loan count | loans		1
Recorded investment as of first default date | $		$ 4