Loans and Allowance for Credit Losses - Summary of Contractually Past Due and Nonaccrual Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	$ 116,596	$ 72,859
Current	4,736,315	4,121,653
Total	4,852,911	4,194,512
Past Due 90 Days or More and Accruing	10,344	5,369
Past Due 30-59 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	78,689	39,055
Past Due 60-90 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	17,614	14,790
Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	20,293	19,014
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	11,373	4,839
Current	751,158	1,042,122
Total	762,531	1,046,961
Past Due 90 Days or More and Accruing	1,287	0
Commercial real estate | Past Due 30-59 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	1,714	1,752
Commercial real estate | Past Due 60-90 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	6,993	1,328
Commercial real estate | Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	2,666	1,759
Construction, land development, land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	2,686	2,988
Current	241,826	157,581
Total	244,512	160,569
Past Due 90 Days or More and Accruing	0	0
Construction, land development, land | Past Due 30-59 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	608	1,785
Construction, land development, land | Past Due 60-90 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	894	842
Construction, land development, land | Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	1,184	361
1-4 family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	2,959	2,673
Current	161,826	176,752
Total	164,785	179,425
Past Due 90 Days or More and Accruing	143	286
1-4 family residential | Past Due 30-59 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	1,049	1,396
1-4 family residential | Past Due 60-90 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	849	723
1-4 family residential | Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	1,061	554
Farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	684	2,560
Current	110,282	152,415
Total	110,966	154,975
Past Due 90 Days or More and Accruing	0	0
Farmland | Past Due 30-59 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	400	52
Farmland | Past Due 60-90 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	0	132
Farmland | Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	284	2,376
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	13,821	18,153
Current	1,523,082	1,324,530
Total	1,536,903	1,342,683
Past Due 90 Days or More and Accruing	276	808
Commercial | Past Due 30-59 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	5,954	4,444
Commercial | Past Due 60-90 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	1,548	4,154
Commercial | Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	6,319	9,555
Factored receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	84,407	40,526
Current	931,930	579,460
Total	1,016,337	619,986
Past Due 90 Days or More and Accruing	8,638	4,226
Factored receivables | Past Due 30-59 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	68,522	29,118
Factored receivables | Past Due 60-90 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	7,247	7,182
Factored receivables | Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	8,638	4,226
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	666	1,120
Current	16,440	20,805
Total	17,106	21,925
Past Due 90 Days or More and Accruing	0	49
Consumer | Past Due 30-59 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	442	508
Consumer | Past Due 60-90 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	83	429
Consumer | Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	141	183
Mortgage warehouse
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	0	0
Current	999,771	667,988
Total	999,771	667,988
Past Due 90 Days or More and Accruing	0	0
Mortgage warehouse | Past Due 30-59 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	0	0
Mortgage warehouse | Past Due 60-90 Days
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	0	0
Mortgage warehouse | Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans past due	$ 0	$ 0