Fair Value Measurements - Summary of Carrying Amount and Fair Values of Financial Instruments Reported on the Balance Sheets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Balance sheet assets
Securities available for sale	$ 1,223,052	$ 721,369
Securities held to maturity	62,725	65,679
State tax credits held for sale	0	0
Carrying Amount
Balance sheet assets
Cash and due from banks	106,835	91,511
Federal funds sold	2,744	1,714
Interest-bearing deposits	82,571	106,512
Securities available for sale	1,223,052	721,369
Securities held to maturity	62,725	65,679
Other investments, at cost	42,990	26,654
Loans held for sale	1,437	392
Derivatives	11,124	3,023
Portfolio loans, net	5,105,675	4,306,525
State tax credits held for sale	37,294	37,587
Accrued interest receivable	27,008	16,069
Balance sheet liabilities
Deposits	5,559,338	4,587,985
Subordinated debentures and notes	141,100	118,156
Federal Home Loan Bank advances	389,446	70,000
Other borrowings	198,104	223,450
Derivatives	14,938	3,023
Accrued interest payable	2,701	1,977
Estimated fair value
Balance sheet assets
Cash and due from banks	106,835	91,511
Federal funds sold	2,744	1,714
Interest-bearing deposits	82,571	106,512
Securities available for sale	1,223,052	721,369
Securities held to maturity	63,061	63,934
Other investments, at cost	42,990	26,654
Loans held for sale	1,437	392
Derivatives	11,124	3,023
Portfolio loans, net	5,049,215	4,253,239
State tax credits held for sale	39,037	39,169
Accrued interest receivable	27,008	16,069
Balance sheet liabilities
Deposits	5,536,456	4,583,047
Subordinated debentures and notes	132,301	106,316
Federal Home Loan Bank advances	389,471	70,000
Other borrowings	197,988	223,260
Derivatives	14,938	3,023
Accrued interest payable	$ 2,701	$ 1,977