Loans and reserve for credit losses (Loans, Covered Loans, Loss Share Payable (Receivable)) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)
Loans and Leases Receivable, Covered [Roll Forward]
Balance at beginning of period	$ 289
Paid to FDIC	(1,224)
Increase due to impairment	(53)
FDIC reimbursement	1,156
Shared loss expenses	(96)
Adjustments from prior periods	4
Balance at end of period	$ 76