Fair Value Measurements - Summary of Carrying Amount and Fair Values of Financial Instruments Reported on the Balance Sheets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Balance sheet assets
Securities available for sale	$ 651,140	$ 641,382
Securities held to maturity	68,931	73,749
State tax credits held for sale	299	400
Carrying Amount
Balance sheet assets
Cash and due from banks	91,851	91,084
Federal funds sold	1,445	1,223
Interest-bearing deposits	86,141	63,661
Securities available for sale	651,140	641,382
Securities held to maturity	68,931	73,749
Other investments, at cost	36,132	26,661
Loans held for sale	1,388	3,155
Derivative financial instruments	5,358	3,589
Portfolio loans, net	4,231,391	4,054,473
State tax credits held for sale	46,481	43,468
Accrued interest receivable	17,808	14,069
Balance sheet liabilities
Deposits	4,247,912	4,156,414
Subordinated debentures and notes	118,131	118,105
Federal Home Loan Bank advances	361,534	172,743
Other borrowings	167,216	253,674
Derivative financial instruments	5,358	3,589
Accrued interest payable	1,884	1,730
Estimated fair value
Balance sheet assets
Cash and due from banks	91,851	91,084
Federal funds sold	1,445	1,223
Interest-bearing deposits	86,141	63,661
Securities available for sale	651,140	641,382
Securities held to maturity	66,909	73,458
Other investments, at cost	36,132	26,661
Loans held for sale	1,388	3,155
Derivative financial instruments	5,358	3,589
Portfolio loans, net	4,252,679	4,096,741
State tax credits held for sale	45,069	44,271
Accrued interest receivable	17,808	14,069
Balance sheet liabilities
Deposits	4,242,061	4,153,323
Subordinated debentures and notes	105,889	105,031
Federal Home Loan Bank advances	361,531	172,893
Other borrowings	167,086	253,530
Derivative financial instruments	5,358	3,589
Accrued interest payable	$ 1,884	$ 1,730