Loans and Allowance for Loan Losses - Amount of Loans by Loan Category Broken Out Between Loans Individually Evaluated for Impairment and Collectively Evaluated for Impairment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	$ 9,018	$ 9,373
Collectively evaluated for impairment	3,149,893	3,068,703
Acquired with deteriorated credit quality	85,752	88,835
Gross loans	3,244,663	3,166,911
Commercial and Industrial
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	1,385	1,579
Collectively evaluated for impairment	761,779	711,352
Acquired with deteriorated credit quality	1,951	2,144
Gross loans	765,115	715,075
Construction
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	1,285	1,289
Collectively evaluated for impairment	457,785	439,309
Acquired with deteriorated credit quality	7,425	7,728
Gross loans	466,495	448,326
Residential Real Estate | 1-to-4 Family Mortgage
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	1,492	1,262
Collectively evaluated for impairment	467,329	456,229
Acquired with deteriorated credit quality	22,904	23,498
Gross loans	491,725	480,989
Residential Real Estate | Residential Line of Credit
Accounts Notes And Loans Receivable [Line Items]
Collectively evaluated for impairment	197,740	194,986
Gross loans	197,740	194,986
Residential Real Estate | Multi-Family Mortgage
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	964	978
Collectively evaluated for impairment	62,313	61,376
Acquired with deteriorated credit quality	18	20
Gross loans	63,295	62,374
Commercial Real Estate | Owner Occupied
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	2,150	2,520
Collectively evaluated for impairment	485,411	481,390
Acquired with deteriorated credit quality	11,770	11,962
Gross loans	499,331	495,872
Commercial Real Estate | Non-Owner Occupied
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	1,713	1,720
Collectively evaluated for impairment	542,351	531,704
Acquired with deteriorated credit quality	18,064	18,164
Gross loans	562,128	551,588
Consumer and Other
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	29	25
Collectively evaluated for impairment	175,185	192,357
Acquired with deteriorated credit quality	23,620	25,319
Gross loans	$ 198,834	$ 217,701