Note 7 - Business Segment Information - Selected Financial Information on the Company's Business Segments (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Operating Segments [Member] | Commercial Banking Segment [Member] | Quad City Bank and Trust Company [Member]
Total revenue	$ 18,026,215	$ 14,143,548	$ 45,706,061	$ 39,893,713
Net interest income	11,225,414	10,728,143	33,394,620	29,745,080
Net income (loss)	3,596,469	3,786,289	10,326,508	6,578,479
Total assets	1,407,733,009	1,328,053,105	1,407,733,009	1,328,053,105
Provision for loan/lease losses	1,137,986	910,263	3,108,821	3,466,384
Goodwill	3,222,688	3,222,688	3,222,688	3,222,688
Finite-Lived Intangible Assets, Net
Operating Segments [Member] | Commercial Banking Segment [Member] | Cedar Rapids Bank and Trust [Member]
Total revenue	10,065,032	10,047,658	31,342,345	28,396,380
Net interest income	7,594,557	6,956,027	21,755,270	19,836,835
Net income (loss)	3,286,724	2,893,397	9,366,441	4,645,136
Total assets	887,592,695	867,064,041	887,592,695	867,064,041
Provision for loan/lease losses		550,000	700,000	1,650,000
Goodwill
Finite-Lived Intangible Assets, Net	1,321,775	1,521,287	1,321,775	1,521,287
Operating Segments [Member] | Commercial Banking Segment [Member] | Community State Bank [Member]
Total revenue	2,675,741		2,675,741
Net interest income	2,191,862		2,191,862
Net income (loss)	188,608		188,608
Total assets	580,210,270		580,210,270
Provision for loan/lease losses	270,000		270,000
Goodwill	10,408,938		10,408,938
Finite-Lived Intangible Assets, Net	6,291,818		6,291,818
Operating Segments [Member] | Commercial Banking Segment [Member] | Rockford Bank and Trust [Member]
Total revenue	4,232,205	3,922,304	11,945,081	11,095,899
Net interest income	3,056,989	2,771,214	8,914,380	8,089,626
Net income (loss)	944,781	847,709	2,334,735	1,895,933
Total assets	393,191,774	360,348,002	393,191,774	360,348,002
Provision for loan/lease losses	200,000	175,000	800,000	578,000
Goodwill
Finite-Lived Intangible Assets, Net
Operating Segments [Member] | Wealth Management Segment [Member]
Total revenue	2,284,577	2,314,406	6,723,690	6,927,453
Net interest income
Net income (loss)	398,859	373,801	1,232,831	1,271,661
Total assets
Provision for loan/lease losses
Goodwill
Finite-Lived Intangible Assets, Net
Operating Segments [Member] | Other Segments [Member]
Total revenue	8,463,636	7,937,087	23,567,906	14,487,857
Net interest income	(438,045)	(317,858)	(1,019,020)	(1,260,962)
Net income (loss)	6,107,492	6,488,988	19,157,447	10,143,059
Total assets	368,990,749	277,001,408	368,990,749	277,001,408
Provision for loan/lease losses
Goodwill
Finite-Lived Intangible Assets, Net
Intersegment Eliminations [Member]
Total revenue	(8,507,270)	(8,821,205)	(23,720,471)	(15,556,437)
Net interest income
Net income (loss)	(8,415,432)	(7,901,197)	(23,449,113)	(14,391,210)
Total assets	(356,732,388)	(256,611,839)	(356,732,388)	(256,611,839)
Provision for loan/lease losses
Goodwill
Finite-Lived Intangible Assets, Net
Total revenue	37,240,136	29,543,798	98,240,353	85,244,865
Net interest income	23,630,777	20,137,526	65,237,112	56,410,579
Net income (loss)	6,107,501	6,488,987	19,157,457	10,143,058
Total assets	3,280,986,109	2,575,854,717	3,280,986,109	2,575,854,717	$ 2,593,198,275
Provision for loan/lease losses	1,607,986	1,635,263	4,878,821	5,694,384
Goodwill	13,631,626	3,222,688	13,631,626	3,222,688	3,222,688
Finite-Lived Intangible Assets, Net	$ 7,613,593	$ 1,521,287	$ 7,613,593	$ 1,521,287	$ 1,471,409