Fair Value Disclosures - Assets, Liabilities and Off-balance Sheet Items Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Assets:
Held-to-maturity securities	$ 229,552	$ 194,886
Total assets	288		$ 1,748
Deposits:
Time deposits	637,012	606,010
Subordinated notes	94,879	94,818
Fair Value [Member]
Assets:
Cash and short-term interest-earning assets	182,902	125,128
Held-to-maturity securities	229,552	194,886
Loans held for sale	11,525	5,560
Net loans and leases held for investment	4,454,495	4,309,208
Servicing rights	6,684	9,340
Total assets	4,885,158	4,644,122
Deposits:
Demand and savings deposits, non-maturity	3,770,291	3,754,065
Time deposits	647,933	609,387
Total deposits	4,418,224	4,363,452
Short-term borrowings	18,415	18,680
Long-term debt	214,492	151,343
Subordinated notes	91,872	96,663
Total liabilities	4,743,003	4,630,138
Off-Balance-Sheet:
Commitments to extend credit	(8,033)	(8,070)
Fair Value [Member] | Level 1 [Member]
Assets:
Cash and short-term interest-earning assets	182,902	125,128
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	182,902	125,128
Deposits:
Demand and savings deposits, non-maturity	3,770,291	3,754,065
Time deposits	0	0
Total deposits	3,770,291	3,754,065
Short-term borrowings	0	0
Long-term debt	0	0
Subordinated notes	0	0
Total liabilities	3,770,291	3,754,065
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	229,552	194,886
Loans held for sale	11,525	5,560
Net loans and leases held for investment	0	0
Servicing rights	0	0
Total assets	241,077	200,446
Deposits:
Demand and savings deposits, non-maturity	0	0
Time deposits	647,933	609,387
Total deposits	647,933	609,387
Short-term borrowings	18,415	18,680
Long-term debt	214,492	151,343
Subordinated notes	91,872	96,663
Total liabilities	972,712	876,073
Off-Balance-Sheet:
Commitments to extend credit	(8,033)	(8,070)
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	4,454,495	4,309,208
Servicing rights	6,684	9,340
Total assets	4,461,179	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
Off-Balance-Sheet:
Commitments to extend credit	0	0
Carrying Amount [Member]
Assets:
Cash and short-term interest-earning assets	182,902	125,128
Held-to-maturity securities	222,389	192,052
Federal Home Loan Bank, Federal Reserve Bank and other stock	28,465	28,254
Loans held for sale	11,417	5,504
Net loans and leases held for investment	4,346,725	4,314,893
Servicing rights	6,440	6,626
Total assets	4,798,338	4,672,457
Deposits:
Demand and savings deposits, non-maturity	3,770,291	3,754,065
Time deposits	637,012	606,010
Total deposits	4,407,303	4,360,075
Short-term borrowings	18,415	18,680
Long-term debt	210,069	150,098
Subordinated notes	94,879	94,818
Total liabilities	4,730,666	4,623,671
Off-Balance-Sheet:
Commitments to extend credit	$ 0	$ 0