Loans and Allowance for Loan and Lease Losses - Summary of Individual and Collective Allowance for Loan Losses and Loan Balances by Class (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Evaluation, Individually	$ 39,313	$ 40,528
Loan Evaluation, Collectively	2,755,945	1,960,189
Loans	2,810,856	2,027,624
ALLL Allocations, Individually	2,713	3,773
ALLL Allocations, Collectively	16,035	11,277
ALLL Allocations, Total ALLL	18,748	15,405	$ 12,567	$ 8,843
Purchased Credit Impaired Loans
Financing Receivable Allowance For Credit Losses [Line Items]
Loans	15,598	26,907
ALLL Allocations, PCI		355
Commercial real estate
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Evaluation, Individually	1,013	1,456
Loan Evaluation, Collectively	735,118	427,918
Loans	745,893	442,237
ALLL Allocations, Individually	123	100
ALLL Allocations, Collectively	3,312	1,358
ALLL Allocations, Total ALLL	3,435	1,813	1,489	533
Commercial real estate \| Purchased Credit Impaired Loans
Financing Receivable Allowance For Credit Losses [Line Items]
Loans	9,762	12,863
ALLL Allocations, PCI		355
Construction, land development, land
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Evaluation, Individually	136	362
Loan Evaluation, Collectively	130,732	105,493
Loans	134,812	109,812
ALLL Allocations, Individually		25
ALLL Allocations, Collectively	883	440
ALLL Allocations, Total ALLL	883	465	367	333
Construction, land development, land \| Purchased Credit Impaired Loans
Financing Receivable Allowance For Credit Losses [Line Items]
Loans	3,944	3,957
1-4 family residential properties
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Evaluation, Individually	2,638	1,095
Loan Evaluation, Collectively	122,093	101,551
Loans	125,827	104,974
ALLL Allocations, Individually	152	1
ALLL Allocations, Collectively	141	252
ALLL Allocations, Total ALLL	293	253	274	215
1-4 family residential properties \| Purchased Credit Impaired Loans
Financing Receivable Allowance For Credit Losses [Line Items]
Loans	1,096	2,328
Farmland
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Evaluation, Individually	3,800	1,333
Loan Evaluation, Collectively	176,232	140,045
Loans	180,141	141,615
ALLL Allocations, Collectively	310	170
ALLL Allocations, Total ALLL	310	170	134	19
Farmland \| Purchased Credit Impaired Loans
Financing Receivable Allowance For Credit Losses [Line Items]
Loans	109	237
Commercial Loans
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Evaluation, Individually	26,616	33,033
Loan Evaluation, Collectively	893,509	738,088
Loans	920,812	778,643
ALLL Allocations, Individually	1,409	2,101
ALLL Allocations, Collectively	6,741	5,913
ALLL Allocations, Total ALLL	8,150	8,014	5,276	4,003
Commercial Loans \| Purchased Credit Impaired Loans
Financing Receivable Allowance For Credit Losses [Line Items]
Loans	687	7,522
Factored receivables
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Evaluation, Individually	4,726	3,176
Loan Evaluation, Collectively	369,684	235,022
Loans	374,410	238,198
ALLL Allocations, Individually	949	1,546
ALLL Allocations, Collectively	3,648	2,542
ALLL Allocations, Total ALLL	4,597	4,088	4,509	3,462
Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Evaluation, Individually	384	73
Loan Evaluation, Collectively	30,747	29,691
Loans	31,131	29,764
ALLL Allocations, Individually	80
ALLL Allocations, Collectively	703	420
ALLL Allocations, Total ALLL	783	420	216	140
Mortgage warehouse
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Evaluation, Collectively	297,830	182,381
Loans	297,830	182,381
ALLL Allocations, Collectively	297	182
ALLL Allocations, Total ALLL	$ 297	$ 182	$ 302	$ 138

A valuation allowance for financing receivables that are expected to be uncollectible.

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The balance of financing receivables that were collectively evaluated for impairment.

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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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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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