Fair Value Disclosures - Assets, Liabilities and Off-balance Sheet Items Not Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets:
Held-to-maturity securities	$ 194,886	$ 141,575
Total assets	317	1,779
Deposits:
Time deposits	606,010	670,077
Subordinated notes	94,818	94,574
Fair Value [Member]
Assets:
Cash and short-term interest-earning assets	125,128	109,420
Held-to-maturity securities	194,886	141,575
Loans held for sale	5,560	1,798
Net loans and leases held for investment	4,309,208	3,924,329
Servicing rights	9,340	11,496
Total assets	4,644,122	4,188,618
Deposits:
Demand and savings deposits, non-maturity	3,754,065	3,215,856
Time deposits	609,387	664,738
Total deposits	4,363,452	3,880,594
Short-term borrowings	18,680	189,768
Long-term debt	151,343	144,021
Subordinated notes	96,663	95,113
Total liabilities	4,630,138	4,309,496
Off-Balance-Sheet:
Commitments to extend credit	(8,070)	(2,516)
Fair Value [Member] | Level 1 [Member]
Assets:
Cash and short-term interest-earning assets	125,128	109,420
Held-to-maturity securities	0	0
Loans held for sale	0	0
Net loans and leases held for investment	0	0
Servicing rights	0	0
Total assets	125,128	109,420
Deposits:
Demand and savings deposits, non-maturity	3,754,065	3,215,856
Time deposits	0	0
Total deposits	3,754,065	3,215,856
Short-term borrowings	0	0
Long-term debt	0	0
Subordinated notes	0	0
Total liabilities	3,754,065	3,215,856
Off-Balance-Sheet:
Commitments to extend credit	0	0
Fair Value [Member] | Level 2 [Member]
Assets:
Cash and short-term interest-earning assets	0	0
Held-to-maturity securities	194,886	141,575
Loans held for sale	5,560	1,798
Net loans and leases held for investment	0	0
Servicing rights	0	0
Total assets	200,446	143,373
Deposits:
Demand and savings deposits, non-maturity	0	0
Time deposits	609,387	664,738
Total deposits	609,387	664,738
Short-term borrowings	18,680	189,768
Long-term debt	151,343	144,021
Subordinated notes	96,663	95,113
Total liabilities	876,073	1,093,640
Off-Balance-Sheet:
Commitments to extend credit	(8,070)	(2,516)
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	0
Net loans and leases held for investment	4,309,208	3,924,329
Servicing rights	9,340	11,496
Total assets	4,318,548	3,935,825
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
Off-Balance-Sheet:
Commitments to extend credit	0	0
Carrying Amount [Member]
Assets:
Cash and short-term interest-earning assets	125,128	109,420
Held-to-maturity securities	192,052	142,634
Federal Home Loan Bank, Federal Reserve Bank and other stock	28,254	28,337
Loans held for sale	5,504	1,754
Net loans and leases held for investment	4,314,893	3,950,265
Servicing rights	6,626	6,768
Total assets	4,672,457	4,239,178
Deposits:
Demand and savings deposits, non-maturity	3,754,065	3,215,856
Time deposits	606,010	670,077
Total deposits	4,360,075	3,885,933
Short-term borrowings	18,680	189,768
Long-term debt	150,098	145,330
Subordinated notes	94,818	94,574
Total liabilities	4,623,671	4,315,605
Off-Balance-Sheet:
Commitments to extend credit	$ 0	$ 0