Fair Value of Financial Instruments - Balances and Levels of Assets Measured at Fair Value on Non-recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financial assets:
Impaired loans	$ 9,996	$ 9,373
Fair Value, Measurements, Nonrecurring
Financial assets:
Other real estate owned	1,333	13,174
Impaired loans	3,997	77,027
Fair Value, Measurements, Nonrecurring | Commercial and Industrial
Financial assets:
Impaired loans	1,695	1,971
Fair Value, Measurements, Nonrecurring | Consumer and Other
Financial assets:
Impaired loans		25,320
Fair Value, Measurements, Nonrecurring | Construction Loans | Commercial and Industrial
Financial assets:
Impaired loans	830	4,211
Fair Value, Measurements, Nonrecurring | Owner Occupied | Commercial Real Estate
Financial assets:
Impaired loans	82	10,030
Fair Value, Measurements, Nonrecurring | 1-to-4 Family Mortgage | Residential Real Estate
Financial assets:
Impaired loans	146	21,902
Fair Value, Measurements, Nonrecurring | Non-Owner Occupied | Commercial Real Estate
Financial assets:
Impaired loans	1,244	13,593
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3)
Financial assets:
Other real estate owned	1,333	13,174
Impaired loans	3,997	77,027
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Commercial and Industrial
Financial assets:
Impaired loans	1,695	1,971
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Consumer and Other
Financial assets:
Impaired loans		25,320
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Construction Loans | Commercial and Industrial
Financial assets:
Impaired loans	830	4,211
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Owner Occupied | Commercial Real Estate
Financial assets:
Impaired loans	82	10,030
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | 1-to-4 Family Mortgage | Residential Real Estate
Financial assets:
Impaired loans	146	21,902
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Non-Owner Occupied | Commercial Real Estate
Financial assets:
Impaired loans	$ 1,244	$ 13,593