Fair Value of Financial Instruments and Fair Value Measurements - Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financial assets:
Debt securities available for sale	$ 1,187,455	$ 785,977
Interest receivable	21,082	18,525
FHLB stock	12,858	15,381
Derivative assets	14,391	1,848
Financial liabilities:
Interest-bearing deposits	1,153,697	962,830
Short-term borrowings	162,224	139,349
Finance leases payable	1,162	1,224
Carrying Amount
Financial assets:
Cash and cash equivalents	117,210	73,484
Debt securities available for sale	1,187,455	785,977
Loans held for sale	12,048	5,400
Loans held for investment, net	3,541,395	3,422,187
Interest receivable	21,082	18,525
FHLB stock	12,858
Derivative assets	14,391	1,848
Financial liabilities:
Non-interest bearing deposits	867,637	662,209
Interest-bearing deposits	3,397,798	3,066,446
Short-term borrowings	162,224	139,349
Finance leases payable	1,162	1,224
Federal Home Loan Bank borrowings	108,246	145,700
Junior subordinated notes issued to capital trusts	41,675	41,587
Subordinated debentures	10,890	10,899
Other long-term debt	28,000	32,250
Derivative liabilities	18,517	3,242
Estimated Fair Value
Financial assets:
Cash and cash equivalents	117,210	73,484
Debt securities available for sale	1,187,455	785,977
Loans held for sale	12,401	5,476
Loans held for investment, net	3,597,325	3,427,952
Interest receivable	21,082	18,525
FHLB stock	12,858	15,381
Derivative assets	14,391	1,848
Financial liabilities:
Non-interest bearing deposits	867,637	662,209
Interest-bearing deposits	3,405,414	3,066,427
Short-term borrowings	162,224	139,349
Finance leases payable	1,162	1,224
Federal Home Loan Bank borrowings	111,902	146,913
Junior subordinated notes issued to capital trusts	34,546	39,391
Subordinated debentures	11,123	11,083
Other long-term debt	28,000	32,250
Derivative liabilities	18,517	3,242
Level 1 | Estimated Fair Value
Financial assets:
Cash and cash equivalents	117,210	73,484
Debt securities available for sale	0	0
Interest receivable	0	0
FHLB stock	0	0
Derivative assets	0	0
Financial liabilities:
Non-interest bearing deposits	867,637	662,209
Interest-bearing deposits	2,428,327	2,113,000
Short-term borrowings	162,224	139,349
Finance leases payable	0	0
Federal Home Loan Bank borrowings	0	0
Junior subordinated notes issued to capital trusts	0	0
Subordinated debentures	0	0
Other long-term debt	0	0
Derivative liabilities	0	0
Level 2 | Estimated Fair Value
Financial assets:
Debt securities available for sale	1,187,455	785,977
Loans held for sale	12,401	5,476
Interest receivable	21,082	18,525
FHLB stock	12,858	15,381
Derivative assets	14,391	1,848
Financial liabilities:
Interest-bearing deposits	977,087	953,427
Finance leases payable	1,162	1,224
Federal Home Loan Bank borrowings	111,902	146,913
Junior subordinated notes issued to capital trusts	34,546	39,391
Subordinated debentures	11,123	11,083
Other long-term debt	28,000	32,250
Derivative liabilities	18,517	3,242
Level 3 | Estimated Fair Value
Financial assets:
Loans held for sale	0	0
Loans held for investment, net	3,597,325	3,427,952
Derivative assets	0	0
Financial liabilities:
Finance leases payable	0	0
Subordinated debentures	0	0
Other long-term debt	0	0
Derivative liabilities	$ 0	$ 0