Loans and Allowance for Loan Losses - Troubled Debt Restructurings, Excluding Loans Acquired, Segregated by Class of Loans (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) loan	Dec. 31, 2017 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	8	16
Loans, Excluding Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	33	40
Total TDR loans | $	$ 9,215	$ 12,938
Loans, Excluding Acquired Loans | Accruing TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	12	13
Total TDR loans | $	$ 6,369	$ 7,107
Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	21	27
Total TDR loans | $	$ 2,846	$ 5,831
Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	4	5
Real Estate | Loans, Excluding Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	23	29
Total TDR loans | $	$ 5,664	$ 9,549
Real Estate | Loans, Excluding Acquired Loans | Accruing TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	8	8
Total TDR loans | $	$ 3,536	$ 4,463
Real Estate | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	15	21
Total TDR loans | $	$ 2,128	$ 5,086
Real Estate | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	1	1
Real Estate | Construction | Loans, Excluding Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	3	1
Total TDR loans | $	$ 485	$ 420
Real Estate | Construction | Loans, Excluding Acquired Loans | Accruing TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	0	0
Total TDR loans | $	$ 0	$ 0
Real Estate | Construction | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	3	1
Total TDR loans | $	$ 485	$ 420
Real Estate | Single family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	1	1
Real Estate | Single family residential | Loans, Excluding Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	16	19
Total TDR loans | $	$ 846	$ 1,095
Real Estate | Single family residential | Loans, Excluding Acquired Loans | Accruing TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	6	4
Total TDR loans | $	$ 230	$ 141
Real Estate | Single family residential | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	10	15
Total TDR loans | $	$ 616	$ 954
Real Estate | Other commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	2	3
Real Estate | Other commercial | Loans, Excluding Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	4	9
Total TDR loans | $	$ 4,333	$ 8,034
Real Estate | Other commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	2	4
Total TDR loans | $	$ 3,306	$ 4,322
Real Estate | Other commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	2	5
Total TDR loans | $	$ 1,027	$ 3,712
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	3	11
Commercial | Loans, Excluding Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	10	11
Total TDR loans | $	$ 3,551	$ 3,389
Commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	4	5
Total TDR loans | $	$ 2,833	$ 2,644
Commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	6	6
Total TDR loans | $	$ 718	$ 745
Commercial | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	3	11
Commercial | Commercial | Loans, Excluding Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	10	11
Total TDR loans | $	$ 3,551	$ 3,389
Commercial | Commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	4	5
Total TDR loans | $	$ 2,833	$ 2,644
Commercial | Commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDR loans	6	6
Total TDR loans | $	$ 718	$ 745