Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net income	$ 35,825	$ 20,649	$ 9,374
Adjustments to reconcile net income to net cash from operating activities:
Stock based compensation	2,509	1,100	553
Depreciation	3,130	2,496	1,764
Provision for loan losses	3,961	2,953	2,119
Net amortization (accretion) of purchase valuation adjustments	(5,586)	(4,518)	615
Amortization (accretion) of premiums and discounts on securities	3,062	2,869	3,049
Amortization of intangible assets	2,492	1,070	419
Deferred income taxes	3,483	2,621	909
Federal Home Loan Bank stock dividends	(1,402)	(760)	(657)
Loss (gain) on sales and valuation adjustments on other real estate owned	(580)	(109)	(112)
Net loss (gain) on sales and settlements of securities	(1)	(271)	(479)
Change in unrealized (gains)/losses on equity securities	11
Loss (gain) on disposal of premises and equipment	(182)	(5)	(42)
Loss (gain) on sales of foreclosed assets	(17)	32
Loss (gain) on sales of loans	(1,072)	(1,640)	(1,198)
Originations of loans held for sale	(48,576)	(73,961)	(51,369)
Proceeds from the sale of loans held for sale	48,271	78,077	51,241
Increase in the value of bank-owned life insurance	(2,199)	(1,445)	(1,000)
Change in fair value of derivatives recognized in earnings	271	(14)	6
Net change in:
Interest receivable	(2,255)	(1,276)	(544)
Other assets	(5,738)	(673)	885
Interest payable and other liabilities	1,259	433	15
Net cash provided by operating activities	36,666	27,628	15,548
Cash flows (to) from investing activities
Purchases of available-for-sale securities	(36,007)	(105,749)	(56,391)
Purchases of held-to-maturity securities	(150,479)	(129,016)	(134,745)
Proceeds from sales, calls, pay-downs and maturities of available-for- sale securities	58,739	102,040	90,459
Proceeds from calls, pay-downs and maturities of held-to-maturity securities	73,098	58,245	51,439
Net change in interest-bearing time deposits in other banks	2,742	1,242	1,495
Net change in loans	(135,500)	(125,679)	(73,932)
Purchase of premises and equipment	(8,831)	(6,873)	(2,796)
Proceeds from sale of premises and equipment	1,254	9	209
Proceeds from sale of foreclosed assets	217	165
Net redemptions (purchases) of Federal Home Loan Bank and Federal Reserve Bank stock	(1,891)	(4,276)	(1,973)
Proceeds from sale of other real estate owned	4,730	5,461	3,017
Purchase of bank-owned life insurance		(15,000)	(14,500)
Proceeds from bank-owned life insurance death benefits	347
Net cash (used in) investing activities	(171,488)	(222,924)	(140,689)
Cash flows (to) from financing activities
Net increase (decrease) in deposits	228,924	123,224	39,082
Net change in federal funds purchased and retail repurchase agreements	12,576	8,177	(4,150)
Net borrowings (repayments) on Federal Home Loan Bank line of credit	20,078	79,996	114,149
Principal repayments on Federal Home Loan Bank term advances	(1,214)	(1,300)	(25,221)
Borrowings on bank stock loan	22,500	2,500	6,000
Principal repayments on bank stock loan	(9,550)	(1,000)	(33,218)
Proceeds from issuance of common stock, net			23,643
Proceeds from exercise of employee stock options	133	1,215	112
Principal payments on employee stock loan		121
Redemption of Series C preferred stock			(16,372)
Net change in contractual obligations	1,998	(537)	(589)
Dividends paid on preferred stock			(42)
Excess tax benefits as a result of the exercise of employee stock options			13
Net cash provided by (used in) financing activities	275,445	212,396	103,407
Net change in cash and cash equivalents	140,623	17,100	(21,734)
Cash and cash equivalents, beginning of period	52,195	35,095	56,829
Ending cash and cash equivalents	192,818	52,195	35,095
Supplemental cash flow information:
Interest paid	32,667	15,041	8,943
Income taxes paid, net of refunds	9,214	6,438	3,212
Supplemental noncash disclosures:
Other real estate owned acquired in settlement of loans	2,307	4,562	3,006
Community First Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash (paid)/from acquisition			(2,971)
Supplemental noncash disclosures:
Total fair value of assets acquired, net of cash			496,352
Total fair value of liabilities acquired			$ 419,641
Prairie State Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash (paid)/from acquisition		(6,744)
Supplemental noncash disclosures:
Total fair value of assets acquired, net of cash		147,247
Total fair value of liabilities acquired		125,591
Eastman National Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash (paid)/from acquisition	(55)	6,108
Supplemental noncash disclosures:
Total fair value of assets acquired, net of cash		267,094
Total fair value of liabilities acquired		234,337
Cache Holdings, Inc. [Member]
Cash flows (to) from investing activities
Net cash (paid)/from acquisition		(2,857)
Supplemental noncash disclosures:
Total fair value of assets acquired, net of cash		333,140
Total fair value of liabilities acquired		$ 291,056
Kansas Bank Corporation [Member]
Cash flows (to) from investing activities
Net cash (paid)/from acquisition	12,774
Supplemental noncash disclosures:
Total fair value of assets acquired, net of cash	308,225
Total fair value of liabilities acquired	289,103
Adams Dairy Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash (paid)/from acquisition	(1,385)
Supplemental noncash disclosures:
Total fair value of assets acquired, net of cash	117,010
Total fair value of liabilities acquired	102,406
City Bank and Trust Company [Member]
Cash flows (to) from investing activities
Net cash (paid)/from acquisition	8,759
Supplemental noncash disclosures:
Total fair value of assets acquired, net of cash	135,594
Total fair value of liabilities acquired	$ 144,353