Fair Value - Assets and liabilities measured at fair value on a nonrecurring basis - (Details) - Nonrecurring basis $ in Thousands	Sep. 30, 2018 USD ($) item	Dec. 31, 2017 USD ($) item	Sep. 30, 2017 USD ($) item
OREO
Fair Value
Other Real Estate	$ 12,119	$ 11,203	$ 13,527
Non-acquired impaired loans
Fair Value
Other Real Estate	6,990	10,495	5,588
Significant Unobservable Inputs (Level 3) | OREO
Fair Value
Other Real Estate	12,119	11,203	13,527
Significant Unobservable Inputs (Level 3) | Non-acquired impaired loans
Fair Value
Other Real Estate	$ 6,990	$ 10,495	$ 5,588
Significant Unobservable Inputs (Level 3) | Discounted appraisals | Impaired loans | Weighted average | Collateral discounts
Quantitative Information about Level 3 Fair Value Measurements
Discount rate (as a percent) | item	0.03	0.03	0.03
Significant Unobservable Inputs (Level 3) | Discounted appraisals | OREO | Weighted average | Collateral discounts and estimated costs to sell
Quantitative Information about Level 3 Fair Value Measurements
Discount rate (as a percent) | item	0.24	0.21	0.23