Fair Value Disclosures - Assets, Liabilities and Off-balance Sheet Items Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Assets:
Held-to-maturity securities	$ 148,960	$ 141,575
Other real estate owned	540	1,187
Total assets	1,748		$ 1,895
Deposits:
Time deposits	638,684	670,077
Subordinated notes	94,635	94,574
Fair Value [Member]
Assets:
Cash and short-term interest-earning assets	66,141	109,420
Held-to-maturity securities	148,960	141,575
Loans held for sale	948	1,798
Net loans and leases held for investment	4,020,771	3,924,329
Servicing rights	10,362	11,496
Total assets	4,247,182	4,188,618
Deposits:
Demand and savings deposits, non-maturity	3,364,469	3,215,856
Time deposits	635,255	664,738
Total deposits	3,999,724	3,880,594
Short-term borrowings	73,185	189,768
Long-term debt	144,717	144,021
Subordinated notes	96,394	95,113
Total liabilities	4,314,020	4,309,496
Off-Balance-Sheet:
Commitments to extend credit	(7,988)	(2,516)
Fair Value [Member] | Level 1 [Member]
Assets:
Cash and short-term interest-earning assets	66,141	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	66,141	109,420
Deposits:
Demand and savings deposits, non-maturity	3,364,469	3,215,856
Time deposits	0	0
Total deposits	3,364,469	3,215,856
Short-term borrowings	0	0
Long-term debt	0	0
Subordinated notes	0	0
Total liabilities	3,364,469	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	148,960	141,575
Loans held for sale	948	1,798
Net loans and leases held for investment	0	0
Servicing rights	0	0
Total assets	149,908	143,373
Deposits:
Demand and savings deposits, non-maturity	0	0
Time deposits	635,255	664,738
Total deposits	635,255	664,738
Short-term borrowings	73,185	189,768
Long-term debt	144,717	144,021
Subordinated notes	96,394	95,113
Total liabilities	949,551	1,093,640
Off-Balance-Sheet:
Commitments to extend credit	(7,988)	(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	4,020,771	3,924,329
Servicing rights	10,362	11,496
Total assets	4,031,133	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	66,141	109,420
Held-to-maturity securities	148,470	142,634
Federal Home Loan Bank, Federal Reserve Bank and other stock	32,699	28,337
Loans held for sale	921	1,754
Net loans and leases held for investment	4,010,030	3,950,265
Servicing rights	6,725	6,768
Total assets	4,264,986	4,239,178
Deposits:
Demand and savings deposits, non-maturity	3,364,469	3,215,856
Time deposits	638,684	670,077
Total deposits	4,003,153	3,885,933
Short-term borrowings	73,185	189,768
Long-term debt	145,263	145,330
Subordinated notes	94,635	94,574
Total liabilities	4,316,236	4,315,605
Off-Balance-Sheet:
Commitments to extend credit	0	0
Fair Value Measured on Recurring Basis [Member]
Assets:
Net loans and leases held for investment	1,748	1,779
Total assets	320,640	333,130
Deposits:
Total liabilities	458	501
Fair Value Measured on Recurring Basis [Member] | Level 1 [Member]
Assets:
Net loans and leases held for investment	0	0
Total assets	2,765	2,165
Deposits:
Total liabilities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 2 [Member]
Assets:
Net loans and leases held for investment	0	0
Total assets	289,488	303,457
Deposits:
Total liabilities	144	170
Fair Value Measured on Recurring Basis [Member] | Level 3 [Member]
Assets:
Net loans and leases held for investment	1,748	1,779
Total assets	28,387	27,508
Deposits:
Total liabilities	$ 314	$ 331