Loans, net and allowance for loan losses - Major Classifications of Loans Outstanding (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable
Loans, net	$ 1,559,867	$ 1,532,965
Commercial
Accounts, Notes, Loans and Financing Receivable
Loans, net	431,164	408,814
Real estate Commercial
Accounts, Notes, Loans and Financing Receivable
Loans, net	703,194	700,144
Real estate Residential
Accounts, Notes, Loans and Financing Receivable
Loans, net	286,389	289,781
Consumer
Accounts, Notes, Loans and Financing Receivable
Loans, net	$ 139,120	$ 134,226

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5074-111524

Name:	us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant