Fair Value Disclosures - Assets, Liabilities and Off-balance Sheet Items Not Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets:
Held-to-maturity securities	$ 156,325	$ 194,886
Total assets	187	317
Deposits:
Time deposits	563,775	606,010
Subordinated notes	183,515	94,818
Fair Value [Member]
Assets:
Cash and short-term interest-earning assets	219,858	125,128
Held-to-maturity securities	156,325	194,886
Loans held for sale		5,560
Net loans and leases held for investment	5,338,782	4,309,208
Servicing rights	6,783	9,340
Total assets	5,721,748	4,644,122
Deposits:
Demand and savings deposits, non-maturity	4,678,940	3,754,065
Time deposits	574,018	609,387
Total deposits	5,252,958	4,363,452
Short-term borrowings	17,906	18,680
Long-term debt	112,968	151,343
Subordinated notes	190,045	96,663
Total liabilities	5,573,877	4,630,138
Fair Value [Member] | Level 1 [Member]
Assets:
Cash and short-term interest-earning assets	219,858	125,128
Held-to-maturity securities	0	0
Loans held for sale		0
Net loans and leases held for investment	0	0
Servicing rights	0	0
Total assets	219,858	125,128
Deposits:
Demand and savings deposits, non-maturity	4,678,940	3,754,065
Time deposits	0	0
Total deposits	4,678,940	3,754,065
Short-term borrowings	0	0
Long-term debt	0	0
Subordinated notes	0	0
Total liabilities	4,678,940	3,754,065
Fair Value [Member] | Level 2 [Member]
Assets:
Cash and short-term interest-earning assets	0	0
Held-to-maturity securities	156,325	194,886
Loans held for sale		5,560
Net loans and leases held for investment	0	0
Servicing rights	0	0
Total assets	156,325	200,446
Deposits:
Demand and savings deposits, non-maturity	0	0
Time deposits	574,018	609,387
Total deposits	574,018	609,387
Short-term borrowings	17,906	18,680
Long-term debt	112,968	151,343
Subordinated notes	190,045	96,663
Total liabilities	894,937	876,073
Fair Value [Member] | Level 3 [Member]
Assets:
Cash and short-term interest-earning assets	0	0
Held-to-maturity securities	0	0
Loans held for sale		0
Net loans and leases held for investment	5,338,782	4,309,208
Servicing rights	6,783	9,340
Total assets	5,345,565	4,318,548
Deposits:
Demand and savings deposits, non-maturity	0	0
Time deposits	0	0
Total deposits	0	0
Short-term borrowings	0	0
Long-term debt	0	0
Subordinated notes	0	0
Total liabilities	0	0
Carrying Amount [Member]
Assets:
Cash and short-term interest-earning assets	219,858	125,128
Held-to-maturity securities	151,257	192,052
Federal Home Loan Bank, Federal Reserve Bank and other stock	28,183	28,254
Loans held for sale		5,504
Net loans and leases held for investment	5,192,710	4,314,893
Servicing rights	6,408	6,626
Total assets	5,598,416	4,672,457
Deposits:
Demand and savings deposits, non-maturity	4,678,940	3,754,065
Time deposits	563,775	606,010
Total deposits	5,242,715	4,360,075
Short-term borrowings	17,906	18,680
Long-term debt	110,000	150,098
Subordinated notes	183,515	94,818
Total liabilities	$ 5,554,136	$ 4,623,671