Loans and Allowance for Loan Losses - Troubled Debt Restructurings, Excluding Loans Acquired, Segregated by Class of Loans (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($) loan	Mar. 31, 2019	Dec. 31, 2019 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts	0	0
Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	30		30
Troubled debt, balance | $	$ 5,233		$ 5,313
Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	12		12
Troubled debt, balance | $	$ 4,110		$ 4,411
Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	18		18
Troubled debt, balance | $	$ 1,123		$ 902
Real Estate | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	23		23
Troubled debt, balance | $	$ 2,403		$ 2,450
Real Estate | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	8		8
Troubled debt, balance | $	$ 1,353		$ 1,627
Real Estate | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	15		15
Troubled debt, balance | $	$ 1,050		$ 823
Real Estate | Construction and development | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	1		1
Troubled debt, balance | $	$ 71		$ 72
Real Estate | Construction and development | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	0		0
Troubled debt, balance | $	$ 0		$ 0
Real Estate | Construction and development | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	1		1
Troubled debt, balance | $	$ 71		$ 72
Real Estate | Single family residential | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	19		19
Troubled debt, balance | $	$ 1,802		$ 1,822
Real Estate | Single family residential | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	7		7
Troubled debt, balance | $	$ 898		$ 1,151
Real Estate | Single family residential | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	12		12
Troubled debt, balance | $	$ 904		$ 671
Real Estate | Other commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	3		3
Troubled debt, balance | $	$ 530		$ 556
Real Estate | Other commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	1		1
Troubled debt, balance | $	$ 455		$ 476
Real Estate | Other commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	2		2
Troubled debt, balance | $	$ 75		$ 80
Commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	7		7
Troubled debt, balance | $	$ 2,830		$ 2,863
Commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	4		4
Troubled debt, balance | $	$ 2,757		$ 2,784
Commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	3		3
Troubled debt, balance | $	$ 73		$ 79
Commercial | Commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	7		7
Troubled debt, balance | $	$ 2,830		$ 2,863
Commercial | Commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	4		4
Troubled debt, balance | $	$ 2,757		$ 2,784
Commercial | Commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt, number of contracts | loan	3		3
Troubled debt, balance | $	$ 73		$ 79