Fair Value Disclosures - Assets, Liabilities and Off-balance Sheet Items Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Assets:
Held-to-maturity securities	$ 115,661	$ 156,325
Total assets	82		$ 221
Deposits:
Time Deposits	494,040	563,775
Subordinated notes	98,797	183,515
Estimate of Fair Value Measurement [Member]
Assets:
Cash and short-term interest-earning assets	902,357	219,858
Held-to-maturity securities	115,661	156,325
Net loans and leases held for investment	5,223,709	5,338,782
Servicing rights	10,336	6,783
Total assets	6,252,063	5,721,748
Deposits:
Demand and savings deposits, non-maturity	5,444,114	4,678,940
Time Deposits	500,192	574,018
Total deposits	5,944,306	5,252,958
Short-term borrowings	14,101	17,906
Long-term debt	96,762	112,968
Subordinated notes	105,500	190,045
Total liabilities	6,160,669	5,573,877
Estimate of Fair Value Measurement [Member] | Level 1 [Member]
Assets:
Cash and short-term interest-earning assets	902,357	219,858
Held-to-maturity securities	0	0
Net loans and leases held for investment	0	0
Servicing rights	0	0
Total assets	902,357	219,858
Deposits:
Demand and savings deposits, non-maturity	5,444,114	4,678,940
Time Deposits	0	0
Total deposits	5,444,114	4,678,940
Short-term borrowings	0	0
Long-term debt	0	0
Subordinated notes	0	0
Total liabilities	5,444,114	4,678,940
Estimate of Fair Value Measurement [Member] | Level 2 [Member]
Assets:
Cash and short-term interest-earning assets	0	0
Held-to-maturity securities	115,661	156,325
Net loans and leases held for investment	0	0
Servicing rights	0	0
Total assets	115,661	156,325
Deposits:
Demand and savings deposits, non-maturity	0	0
Time Deposits	500,192	574,018
Total deposits	500,192	574,018
Short-term borrowings	14,101	17,906
Long-term debt	96,762	112,968
Subordinated notes	105,500	190,045
Total liabilities	716,555	894,937
Estimate of Fair Value Measurement [Member] | Level 3 [Member]
Assets:
Cash and short-term interest-earning assets	0	0
Held-to-maturity securities	0	0
Net loans and leases held for investment	5,223,709	5,338,782
Servicing rights	10,336	6,783
Total assets	5,234,045	5,345,565
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	902,357	219,858
Held-to-maturity securities	112,643	151,257
Federal Home Loan Bank, Federal Reserve Bank and other stock	28,679	28,183
Net loans and leases held for investment	5,147,334	5,192,710
Servicing rights	7,610	6,408
Total assets	6,198,623	5,598,416
Deposits:
Demand and savings deposits, non-maturity	5,444,114	4,678,940
Time Deposits	494,040	563,775
Total deposits	5,938,154	5,242,715
Short-term borrowings	14,101	17,906
Long-term debt	95,000	110,000
Subordinated notes	98,797	183,515
Total liabilities	$ 6,146,052	$ 5,554,136