Loans and Allowance for Credit Losses - Troubled Debt Restructurings, Excluding Loans Acquired, Segregated by Class of Loans (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($) loan	Jun. 30, 2019 loan	Jun. 30, 2020 USD ($) loan	Jun. 30, 2019 loan	Dec. 31, 2019 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans	1	0	1	0
Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			28		30
Troubled debt, balance | $	$ 4,778		$ 4,778		$ 5,313
Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			16		12
Troubled debt, balance | $	3,960		$ 3,960		$ 4,411
Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			12		18
Troubled debt, balance | $	818		$ 818		$ 902
Real Estate | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			21		23
Troubled debt, balance | $	1,971		$ 1,971		$ 2,450
Real Estate | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			12		8
Troubled debt, balance | $	1,221		$ 1,221		$ 1,627
Real Estate | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			9		15
Troubled debt, balance | $	$ 750		$ 750		$ 823
Real Estate | Construction and development | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans					1
Troubled debt, balance | $					$ 72
Real Estate | Construction and development | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans					0
Troubled debt, balance | $					$ 0
Real Estate | Construction and development | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans					1
Troubled debt, balance | $					$ 72
Real Estate | Single family residential
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans	1		1
Real Estate | Single family residential | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			19		19
Troubled debt, balance | $	$ 1,901		$ 1,901		$ 1,822
Real Estate | Single family residential | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			12		7
Troubled debt, balance | $	1,221		$ 1,221		$ 1,151
Real Estate | Single family residential | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			7		12
Troubled debt, balance | $	680		$ 680		$ 671
Real Estate | Other commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			2		3
Troubled debt, balance | $	70		$ 70		$ 556
Real Estate | Other commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			0		1
Troubled debt, balance | $	0		$ 0		$ 476
Real Estate | Other commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			2		2
Troubled debt, balance | $	70		$ 70		$ 80
Commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			7		7
Troubled debt, balance | $	2,807		$ 2,807		$ 2,863
Commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			4		4
Troubled debt, balance | $	2,739		$ 2,739		$ 2,784
Commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			3		3
Troubled debt, balance | $	68		$ 68		$ 79
Commercial | Commercial | Loans, Excluding Acquired Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			7		7
Troubled debt, balance | $	2,807		$ 2,807		$ 2,863
Commercial | Commercial | Loans, Excluding Acquired Loans | Accruing TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			4		4
Troubled debt, balance | $	2,739		$ 2,739		$ 2,784
Commercial | Commercial | Loans, Excluding Acquired Loans | Nonaccrual TDR Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans			3		3
Troubled debt, balance | $	$ 68		$ 68		$ 79