Fair Value Measurements - Summary of Carrying Amount and Fair Values of Financial Instruments Reported on the Balance Sheets (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Balance sheet assets
Securities available for sale	$ 400,146	$ 434,587
Securities held to maturity	45,985	0
State tax credits held for sale	11,689	16,491
Carrying Amount
Balance sheet assets
Cash and due from banks	42,903	19,573
Federal funds sold	35	76
Interest-bearing deposits	63,058	196,220
Securities available for sale	400,146	434,587
Securities held to maturity	45,985	0
Other investments, at cost	17,037	12,605
Loans held for sale	4,033	1,834
Derivative financial instruments	909	1,000
Portfolio loans, net	2,487,424	2,235,124
State tax credits held for sale	38,309	48,457
Accrued interest receivable	7,956	7,303
Balance sheet liabilities
Deposits	2,491,510	2,534,953
Subordinated debentures	56,807	62,581
Federal Home Loan Bank advances	144,000	50,000
Other borrowings	239,883	214,331
Derivative financial instruments	907	990
Accrued interest payable	843	957
Estimated fair value
Balance sheet assets
Cash and due from banks	42,903	19,573
Federal funds sold	35	76
Interest-bearing deposits	63,058	196,220
Securities available for sale	400,146	434,587
Securities held to maturity	45,795	0
Other investments, at cost	17,037	12,605
Loans held for sale	4,033	1,834
Derivative financial instruments	909	1,000
Portfolio loans, net	2,482,700	2,232,134
State tax credits held for sale	42,970	52,159
Accrued interest receivable	7,956	7,303
Balance sheet liabilities
Deposits	2,494,624	2,540,822
Subordinated debentures	34,124	39,358
Federal Home Loan Bank advances	144,000	54,137
Other borrowings	239,950	214,377
Derivative financial instruments	907	990
Accrued interest payable	$ 843	$ 957