Fair Value Measurements - Summary of Carrying Amount and Fair Values of Financial Instruments Reported on the Balance Sheets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Balance sheet assets
Securities available for sale	$ 652,272	$ 641,382
Securities held to maturity	70,579	73,749
State tax credits held for sale	350	400
Carrying Amount
Balance sheet assets
Cash and due from banks	81,604	91,084
Federal funds sold	1,099	1,223
Interest-bearing deposits	62,798	63,661
Securities available for sale	652,272	641,382
Securities held to maturity	70,579	73,749
Other investments, at cost	29,263	26,661
Loans held for sale	1,748	3,155
Derivative financial instruments	4,006	3,589
Portfolio loans, net	4,146,195	4,054,473
State tax credits held for sale	42,364	43,468
Accrued interest receivable	17,277	14,069
Balance sheet liabilities
Deposits	4,281,377	4,156,414
Subordinated debentures and notes	118,118	118,105
Federal Home Loan Bank advances	224,624	172,743
Other borrowings	166,589	253,674
Derivative financial instruments	4,006	3,589
Accrued interest payable	2,046	1,730
Estimated fair value
Balance sheet assets
Cash and due from banks	81,604	91,084
Federal funds sold	1,099	1,223
Interest-bearing deposits	62,798	63,661
Securities available for sale	652,272	641,382
Securities held to maturity	68,766	73,458
Other investments, at cost	29,263	26,661
Loans held for sale	1,748	3,155
Derivative financial instruments	4,006	3,589
Portfolio loans, net	4,158,694	4,096,741
State tax credits held for sale	41,072	44,271
Accrued interest receivable	17,277	14,069
Balance sheet liabilities
Deposits	4,276,096	4,153,323
Subordinated debentures and notes	105,751	105,031
Federal Home Loan Bank advances	224,665	172,893
Other borrowings	166,471	253,530
Derivative financial instruments	4,006	3,589
Accrued interest payable	$ 2,046	$ 1,730