Fair Value - Assets and liabilities measured at fair value on a nonrecurring basis (Details) - Nonrecurring basis $ in Thousands	Sep. 30, 2019 USD ($) item	Dec. 31, 2018 USD ($) item	Sep. 30, 2018 USD ($) item
OREO | Fair Value
Fair Value
Other Real Estate	$ 13,415	$ 11,410	$ 12,119
Non-acquired impaired loans | Fair Value
Fair Value
Other Real Estate	$ 10,620	$ 13,164	$ 6,990
Significant Unobservable Inputs (Level 3) | Impaired loans
Quantitative Information about Level 3 Fair Value Measurements
Long-term Debt, Valuation Technique [Extensible List]	us-gaap:MarketApproachValuationTechniqueMember	us-gaap:MarketApproachValuationTechniqueMember	us-gaap:MarketApproachValuationTechniqueMember
Long-term Debt, Measurement Input [Extensible List]	us-gaap:MeasurementInputDiscountRateMember	us-gaap:MeasurementInputDiscountRateMember	us-gaap:MeasurementInputDiscountRateMember
Significant Unobservable Inputs (Level 3) | Impaired loans | Weighted average
Quantitative Information about Level 3 Fair Value Measurements
Discount rate (as a percent) | item	0.02	0.03	0.03
Significant Unobservable Inputs (Level 3) | OREO
Fair Value
Other Real Estate	$ 13,415	$ 11,410	$ 12,119
Quantitative Information about Level 3 Fair Value Measurements
Long-term Debt, Valuation Technique [Extensible List]	us-gaap:MarketApproachValuationTechniqueMember	us-gaap:MarketApproachValuationTechniqueMember	us-gaap:MarketApproachValuationTechniqueMember
Long-term Debt, Measurement Input [Extensible List]	us-gaap:MeasurementInputCostToSellMember	us-gaap:MeasurementInputCostToSellMember	us-gaap:MeasurementInputCostToSellMember
Significant Unobservable Inputs (Level 3) | OREO | Weighted average
Quantitative Information about Level 3 Fair Value Measurements
Discount rate (as a percent) | item	0.25	0.23	0.24
Significant Unobservable Inputs (Level 3) | Non-acquired impaired loans
Fair Value
Other Real Estate	$ 10,620	$ 13,164	$ 6,990