Loans and Allowance for Loan Losses - Troubled Debt Restructurings, Excluding Loans Acquired, Segregated by Class of Loans (Details) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2019 USD ($) loan	Jun. 30, 2018 loan	Dec. 31, 2018 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts		2
Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	31		33
Troubled debt, balance | $	$ 8,523		$ 9,215
Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	11		12
Troubled debt, balance | $	$ 6,246		$ 6,369
Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	20		21
Troubled debt, balance | $	$ 2,277		$ 2,846
Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts		1
Real Estate | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	22		23
Troubled debt, balance | $	$ 5,400		$ 5,664
Real Estate | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	7		8
Troubled debt, balance | $	$ 3,434		$ 3,536
Real Estate | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	15		15
Troubled debt, balance | $	$ 1,966		$ 2,128
Real Estate | Construction | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	3		3
Troubled debt, balance | $	$ 405		$ 485
Real Estate | Construction | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	0		0
Troubled debt, balance | $	$ 0		$ 0
Real Estate | Construction | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	3		3
Troubled debt, balance | $	$ 405		$ 485
Real Estate | Single family residential
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts		1
Real Estate | Single family residential | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	15		16
Troubled debt, balance | $	$ 804		$ 846
Real Estate | Single family residential | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	5		6
Troubled debt, balance | $	$ 221		$ 230
Real Estate | Single family residential | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	10		10
Troubled debt, balance | $	$ 583		$ 616
Real Estate | Other commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	4		4
Troubled debt, balance | $	$ 4,191		$ 4,333
Real Estate | Other commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	2		2
Troubled debt, balance | $	$ 3,213		$ 3,306
Real Estate | Other commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	2		2
Troubled debt, balance | $	$ 978		$ 1,027
Commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	9		10
Troubled debt, balance | $	$ 3,123		$ 3,551
Commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	4		4
Troubled debt, balance | $	$ 2,812		$ 2,833
Commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	5		6
Troubled debt, balance | $	$ 311		$ 718
Commercial | Commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	9		10
Troubled debt, balance | $	$ 3,123		$ 3,551
Commercial | Commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	4		4
Troubled debt, balance | $	$ 2,812		$ 2,833
Commercial | Commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	5		6
Troubled debt, balance | $	$ 311		$ 718