Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net income	$ 25,579	$ 35,825	$ 20,649
Adjustments to reconcile net income to net cash from operating activities:
Stock-based compensation	2,870	2,509	1,100
Depreciation	3,565	3,130	2,496
Amortization of operating lease right-of-use asset	629
Amortization of cloud computing implementation costs	100
Provision for loan losses	18,354	3,961	2,953
Net amortization (accretion) of purchase valuation adjustments	(4,360)	(5,586)	(4,518)
Amortization (accretion) of premiums and discounts on securities	5,828	3,062	2,869
Amortization of intangible assets	3,218	2,492	1,070
Deferred income taxes	1,563	3,483	2,621
Federal Home Loan Bank stock dividends	(994)	(1,402)	(760)
Loss (gain) on sales and valuation adjustments on other real estate owned	68	(580)	(109)
Net loss (gain) on sales and settlements of securities		(1)	(271)
Change in unrealized (gains) losses on equity securities	(14)	11
Loss (gain) on disposal of premises and equipment	(19)	(182)	(5)
Loss (gain) on lease termination	(7)
Loss (gain) on sales of foreclosed assets	25	(17)	32
Loss (gain) on sales of loans	(2,062)	(1,072)	(1,640)
Originations of loans held for sale	(99,686)	(48,576)	(73,961)
Proceeds from the sale of loans held for sale	98,787	48,271	78,077
Increase in the value of bank-owned life insurance	(1,998)	(2,199)	(1,445)
Change in fair value of derivatives recognized in earnings	308	271	(14)
Payments on operating lease payable	(760)
Net change in:
Interest receivable	1,649	(2,255)	(1,276)
Other assets	(3,823)	(5,738)	(673)
Interest payable and other liabilities	(299)	1,259	433
Net cash provided by operating activities	48,521	36,666	27,628
Cash flows (to) from investing activities
Purchases of available-for-sale securities		(36,007)	(105,749)
Purchases of held-to-maturity securities	(154,573)	(150,479)	(129,016)
Proceeds from sales, calls, pay-downs and maturities of available-for- sale securities	30,633	58,739	102,040
Proceeds from calls, pay-downs and maturities of held-to-maturity securities	129,349	73,098	58,245
Net change in interest-bearing time deposits in other banks	2,493	2,742	1,242
Net change in loans	8,537	(135,500)	(125,679)
Capitalized construction cost of other real estate owned	(56)
Purchase of premises and equipment	(6,948)	(8,831)	(6,873)
Proceeds from sale of premises and equipment	21	1,254	9
Proceeds from sale of foreclosed assets	410	217	165
Net redemptions (purchases) of Federal Home Loan Bank and Federal Reserve Bank stock	(928)	(1,891)	(4,276)
Proceeds from sale of other real estate owned	1,803	4,730	5,461
Purchase of bank-owned life insurance			(15,000)
Proceeds from bank-owned life insurance death benefits		347
Net cash (used in) provided by investing activities	96,101	(171,488)	(222,924)
Cash flows (to) from financing activities
Net increase (decrease) in deposits	(158,652)	228,924	123,224
Net change in federal funds purchased and retail repurchase agreements	(14,360)	12,576	8,177
Net borrowings (repayments) on Federal Home Loan Bank line of credit	(57,547)	20,078	79,996
Principal repayments on Federal Home Loan Bank term advances	(2,954)	(1,214)	(1,300)
Borrowings on bank stock loan	7,209	22,500	2,500
Principal repayments on bank stock loan	(13,669)	(9,550)	(1,000)
Proceeds from exercise of employee stock options	371	133	1,215
Principal payments on employee stock loan	44		121
Proceeds from employee stock purchase plan	405
Purchase of treasury stock	(10,867)
Net change in contractual obligations	1,871	1,998	(537)
Net cash provided by (used in) financing activities	(248,149)	275,445	212,396
Net change in cash and cash equivalents	(103,527)	140,623	17,100
Cash and cash equivalents, beginning of period	192,818	52,195	35,095
Ending cash and cash equivalents	89,291	192,818	52,195
Supplemental cash flow information:
Interest paid	48,367	32,667	15,041
Income taxes paid, net of refunds	3,108	9,214	6,438
Supplemental noncash disclosures:
Other real estate owned acquired in settlement of loans	3,737	2,307	4,562
Operating leases recognized	4,814
Prairie State Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash (paid) received 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) received 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) received 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) received 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) received 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) received 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
MidFirst Bank [Member]
Cash flows (to) from investing activities
Net cash (paid) received from acquisition	85,360
Supplemental noncash disclosures:
Total fair value of assets acquired, net of cash	13,246
Total fair value of liabilities acquired	$ 98,606