Loans and reserve for credit losses (Schedule of Accounts, Notes, Loans and Financing Receivable) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 2,061,508	$ 1,687,929
Loans and leases receivable, before fees, gross, percent	100.00%	100.00%
Deferred loan fees	$ (1,917)	$ (1,419)
Reserve for loan losses	(25,238)	(24,415)
Loans, net	2,034,353	1,662,095
Commercial real estate: \| Owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 376,003	$ 308,331
Loans and leases receivable, before fees, gross, percent	18.10%	18.30%
Commercial real estate: \| Non-owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 588,777	$ 526,562
Loans and leases receivable, before fees, gross, percent	28.60%	31.20%
Commercial real estate: \| Total commercial real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 964,780	$ 834,893
Loans and leases receivable, before fees, gross, percent	46.70%	49.50%
Reserve for loan losses	$ (6,019)	$ (3,934)
Construction \| Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 182,981	$ 130,352
Loans and leases receivable, before fees, gross, percent	8.90%	7.70%
Reserve for loan losses	$ (1,857)	$ (1,044)
Residential real estate \| Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 465,466	$ 298,390
Loans and leases receivable, before fees, gross, percent	22.60%	17.70%
Reserve for loan losses	$ (3,763)	$ (2,075)
Commercial and industrial \| Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 405,269	$ 384,444
Loans and leases receivable, before fees, gross, percent	19.70%	22.80%
Reserve for loan losses	$ (10,549)	$ (13,969)
Consumer \| Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 43,012	$ 39,850
Loans and leases receivable, before fees, gross, percent	2.10%	2.30%
Reserve for loan losses	$ (1,212)	$ (917)
Originated Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 1,762,724	$ 1,452,978
Loans and leases receivable, before fees, gross, percent	100.00%	100.00%
Deferred loan fees	$ (1,917)	$ (1,419)
Reserve for loan losses	(25,238)	(24,415)
Loans, net	1,735,569	1,427,144
Originated Loans \| Commercial real estate: \| Owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 280,901	$ 263,095
Loans and leases receivable, before fees, gross, percent	15.80%	18.10%
Originated Loans \| Commercial real estate: \| Non-owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 486,689	$ 431,379
Loans and leases receivable, before fees, gross, percent	27.60%	29.70%
Originated Loans \| Commercial real estate: \| Total commercial real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 767,590	$ 694,474
Loans and leases receivable, before fees, gross, percent	43.40%	47.80%
Originated Loans \| Construction \| Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 168,558	$ 119,723
Loans and leases receivable, before fees, gross, percent	9.60%	8.20%
Originated Loans \| Residential real estate \| Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 406,374	$ 237,084
Loans and leases receivable, before fees, gross, percent	23.10%	16.30%
Originated Loans \| Commercial and industrial \| Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 378,700	$ 363,335
Loans and leases receivable, before fees, gross, percent	21.50%	25.00%
Originated Loans \| Consumer \| Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 41,502	$ 38,362
Loans and leases receivable, before fees, gross, percent	2.40%	2.70%
Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 298,784	$ 234,951
Loans and leases receivable, before fees, gross, percent	100.00%	100.00%
Acquired Loans \| Commercial real estate: \| Owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 95,102	$ 45,236
Loans and leases receivable, before fees, gross, percent	31.80%	19.30%
Acquired Loans \| Commercial real estate: \| Non-owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 102,088	$ 95,183
Loans and leases receivable, before fees, gross, percent	34.20%	40.50%
Acquired Loans \| Commercial real estate: \| Total commercial real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 197,190	$ 140,419
Loans and leases receivable, before fees, gross, percent	66.00%	59.80%
Acquired Loans \| Construction \| Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 14,423	$ 10,629
Loans and leases receivable, before fees, gross, percent	4.80%	4.50%
Acquired Loans \| Residential real estate \| Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 59,092	$ 61,306
Loans and leases receivable, before fees, gross, percent	19.80%	26.10%
Acquired Loans \| Commercial and industrial \| Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 26,569	$ 21,109
Loans and leases receivable, before fees, gross, percent	8.90%	9.00%
Acquired Loans \| Consumer \| Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, before fees, gross, amount	$ 1,510	$ 1,488
Loans and leases receivable, before fees, gross, percent	0.50%	0.60%

Loans and Leases Receivable before Fees, Gross, Percentage

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

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Amount, before allowance and fees, of loans and leases receivable. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and 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 and loans held for sale.

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Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

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