Fair Value Disclosures - Assets, Liabilities and Off-balance Sheet Items Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Assets:
Held-to-maturity securities	$ 208,307	$ 194,886
Total assets	255		$ 1,725
Deposits:
Time deposits	520,485	606,010
Subordinated notes	94,903	94,818
Fair Value [Member]
Assets:
Cash and short-term interest-earning assets	348,529	125,128
Held-to-maturity securities	208,307	194,886
Loans held for sale	31,279	5,560
Net loans and leases held for investment	4,977,902	4,309,208
Servicing rights	6,191	9,340
Total assets	5,572,208	4,644,122
Deposits:
Demand and savings deposits, non-maturity	4,348,844	3,754,065
Time deposits	532,459	609,387
Total deposits	4,881,303	4,363,452
Short-term borrowings	210,780	18,680
Long-term debt	215,137	151,343
Subordinated notes	93,430	96,663
Total liabilities	5,400,650	4,630,138
Fair Value [Member] | Level 1 [Member]
Assets:
Cash and short-term interest-earning assets	348,529	125,128
Held-to-maturity securities	0	0
Loans held for sale	14,416	0
Net loans and leases held for investment	0	0
Servicing rights	0	0
Total assets	362,945	125,128
Deposits:
Demand and savings deposits, non-maturity	4,348,844	3,754,065
Time deposits	0	0
Total deposits	4,348,844	3,754,065
Short-term borrowings	0	0
Long-term debt	0	0
Subordinated notes	0	0
Total liabilities	4,348,844	3,754,065
Fair Value [Member] | Level 2 [Member]
Assets:
Cash and short-term interest-earning assets	0	0
Held-to-maturity securities	208,307	194,886
Loans held for sale	16,863	5,560
Net loans and leases held for investment	0	0
Servicing rights	0	0
Total assets	225,170	200,446
Deposits:
Demand and savings deposits, non-maturity	0	0
Time deposits	532,459	609,387
Total deposits	532,459	609,387
Short-term borrowings	210,780	18,680
Long-term debt	215,137	151,343
Subordinated notes	93,430	96,663
Total liabilities	1,051,806	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	0
Net loans and leases held for investment	4,977,902	4,309,208
Servicing rights	6,191	9,340
Total assets	4,984,093	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	348,529	125,128
Held-to-maturity securities	201,703	192,052
Federal Home Loan Bank, Federal Reserve Bank and other stock	28,192	28,254
Loans held for sale	31,082	5,504
Net loans and leases held for investment	4,840,697	4,314,893
Servicing rights	6,081	6,626
Total assets	5,456,284	4,672,457
Deposits:
Demand and savings deposits, non-maturity	4,348,844	3,754,065
Time deposits	520,485	606,010
Total deposits	4,869,329	4,360,075
Short-term borrowings	210,780	18,680
Long-term debt	210,039	150,098
Subordinated notes	94,903	94,818
Total liabilities	$ 5,385,051	$ 4,623,671