Income taxes - Current and Deferred Amounts of Provision for Income Taxes Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current									$ 4,072	$ 6,515	$ 6,450
Deferred									(681)	1,665	(1,442)
Total income tax expense (benefit)	$ 904	$ 902	$ 811	$ 774	$ 3,971	$ 1,287	$ 1,653	$ 1,269	3,391	8,180	5,008
Peoples Bank
Total income tax expense (benefit)									$ (27)	$ (54)	$ (75)

Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration