Loans and Allowance for Loan Losses ("ALLL") - Loan Loss Activity - Previous GAAP (Details) $ in Thousands	3 Months Ended
Mar. 31, 2021 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	$ 75,295
Provision	7,500
Charge-offs	(8,266)
Recoveries	22
Ending balance	74,551
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	24,693
Provision	7,015
Charge-offs	(8,266)
Recoveries	22
Ending balance	23,464
Energy
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	18,341
Provision	1,951
Charge-offs	0
Recoveries	0
Ending balance	20,292
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	22,354
Provision	(1,745)
Charge-offs	0
Recoveries	0
Ending balance	20,609
Construction and land development
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	3,612
Provision	225
Charge-offs	0
Recoveries	0
Ending balance	3,837
Residential and Multifamily Real Estate [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	5,842
Provision	214
Charge-offs	0
Recoveries	0
Ending balance	6,056
Paycheck Protection Program ("PPP")
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	0
Provision	0
Charge-offs	0
Recoveries	0
Ending balance	0
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	453
Provision	(160)
Charge-offs	0
Recoveries	0
Ending balance	$ 293

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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