Loans Held for Investment and Allowance for Loan Losses - Restructured Loans (Details) $ in Thousands	6 Months Ended
Jun. 30, 2020 USD ($) loan	Jun. 30, 2019 USD ($) loan	Dec. 31, 2019 USD ($)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccrual loans that met the criteria for restructured	$ 23,700		$ 35,100
Number of Contracts \| loan	3	2
Loans modified as restructured loans	$ 14,011	$ 18,437
Aggregate number of loans modified \| loan	482
Financing Receivable, Modifications, Outstanding Balance	$ 1,200,000
Aggregate interest deferred	$ 10,800
Extended maturity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| loan	3	2
Loans modified as restructured loans	$ 14,011	$ 18,437
Adjusted payment schedule
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| loan	0	0
Loans modified as restructured loans	$ 0	$ 0
Commercial Loan \| Business Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| loan	2	1
Loans modified as restructured loans	$ 7,906	$ 1,896
Commercial Loan \| Business Loans \| Extended maturity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| loan	2	1
Loans modified as restructured loans	$ 7,906	$ 1,896
Commercial Loan \| Business Loans \| Adjusted payment schedule
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| loan	0	0
Loans modified as restructured loans	$ 0	$ 0
Commercial Loan \| Energy
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| loan	1	1
Loans modified as restructured loans	$ 6,105	$ 16,541
Commercial Loan \| Energy \| Extended maturity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| loan	1	1
Loans modified as restructured loans	$ 6,105	$ 16,541
Commercial Loan \| Energy \| Adjusted payment schedule
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| loan	0	0
Loans modified as restructured loans	$ 0	$ 0

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- Definition

Financing Receivable, Modifications, Aggregate Number of Contracts

+ References

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- Definition

Nonaccrual loans that met the criteria for restructured

+ References

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- Definition

Financing Receivable, Modifications, Outstanding Balance

+ References

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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.

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Number of financing receivables that have been modified by troubled debt restructurings.

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Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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