Loans and Allowance for Loan Losses - SBA Loan Summary (Details) $ in Thousands	Sep. 30, 2020 USD ($) loan	Dec. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held-for-investment	$ 1,578,804	$ 1,450,831
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held-for-investment	$ 342,518	240,480
Commercial and Industrial | SBA PPP
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	1,614
Loans held-for-investment	$ 136,418	$ 0
$50,000 or less | Commercial and Industrial | SBA PPP
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	1,043
Loans held-for-investment	$ 21,551
Over $50,000 and less than $350,000 | Commercial and Industrial | SBA PPP
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	499
Loans held-for-investment	$ 60,679
Over $350,000 and less than $2,000,000 | Commercial and Industrial | SBA PPP
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	69
Loans held-for-investment	$ 45,813
$2,000,000 or more | Commercial and Industrial | SBA PPP
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Loans | loan	3
Loans held-for-investment	$ 8,375