Loans and Allowance for Loan Losses ("ALLL") - Troubled Debt Restructuring Loans (Details) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2021 USD ($) contract	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total troubled debt restructurings	$ 0	$ 5,511
Number of Loans \| contract	16		17
Outstanding Balance	$ 61,715		$ 63,095
Balance 90 days past due at any time during previous 12 months	6,734		5,489
Increase in allowance for loan losses from loan restructuring	$ 5,000		$ 4,000
Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans \| contract	6		7
Outstanding Balance	$ 21,631		$ 22,759
Balance 90 days past due at any time during previous 12 months	$ 4,115		$ 2,776
Energy
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans \| contract	4		4
Outstanding Balance	$ 10,850		$ 11,053
Balance 90 days past due at any time during previous 12 months	$ 2,619		$ 2,713
Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans \| contract	4		4
Outstanding Balance	$ 25,990		$ 26,038
Balance 90 days past due at any time during previous 12 months	$ 0		$ 0
Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans \| contract	0		0
Outstanding Balance	$ 0		$ 0
Balance 90 days past due at any time during previous 12 months	$ 0		$ 0
Residential and multifamily real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans \| contract	2		2
Outstanding Balance	$ 3,244		$ 3,245
Balance 90 days past due at any time during previous 12 months	$ 0		$ 0
Paycheck Protection Program (“PPP”)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans \| contract	0		0
Outstanding Balance	$ 0		$ 0
Balance 90 days past due at any time during previous 12 months	$ 0		$ 0
Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans \| contract	0		0
Outstanding Balance	$ 0		$ 0
Balance 90 days past due at any time during previous 12 months	0		$ 0
Interest Rate Reduction \| Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total troubled debt restructurings	0	3,171
Extension of Maturity Date \| Energy
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total troubled debt restructurings	$ 0	$ 2,340

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
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