Loans and Allowance for Loan Losses - Amount of Loans by Loan Category Broken Between Loans Individually and Collectively Evaluated for Impairment and Acquired with Deteriorated Credit Quality (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	$ 9,263	$ 9,373
Collectively evaluated for impairment	3,327,999	3,068,703
Acquired with deteriorated credit quality	78,313	88,835
Gross loans	3,415,575	3,166,911
Commercial and Industrial
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	2,186	1,579
Collectively evaluated for impairment	809,102	711,352
Acquired with deteriorated credit quality	1,766	2,144
Gross loans	813,054	715,075
Construction
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	1,281	1,289
Collectively evaluated for impairment	514,129	439,309
Acquired with deteriorated credit quality	7,061	7,728
Gross loans	522,471	448,326
Residential Real Estate | 1-to-4 Family Mortgage
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	1,503	1,262
Collectively evaluated for impairment	505,643	456,229
Acquired with deteriorated credit quality	21,012	23,498
Gross loans	528,158	480,989
Residential Real Estate | Residential Line of Credit
Accounts Notes And Loans Receivable [Line Items]
Collectively evaluated for impairment	208,668	194,986
Gross loans	208,668	194,986
Residential Real Estate | Multi-Family Mortgage
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	951	978
Collectively evaluated for impairment	56,377	61,376
Acquired with deteriorated credit quality	16	20
Gross loans	57,344	62,374
Commercial Real Estate | Owner Occupied
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	2,266	2,520
Collectively evaluated for impairment	460,281	481,390
Acquired with deteriorated credit quality	8,325	11,962
Gross loans	470,872	495,872
Commercial Real Estate | Non-Owner Occupied
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	1,049	1,720
Collectively evaluated for impairment	581,531	531,704
Acquired with deteriorated credit quality	18,049	18,164
Gross loans	600,629	551,588
Consumer and Other
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	27	25
Collectively evaluated for impairment	192,268	192,357
Acquired with deteriorated credit quality	22,084	25,319
Gross loans	$ 214,379	$ 217,701