Note 6 - Business Segment Information - Selected Financial Information on the Company's Business Segments (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Total assets	$ 3,457,186,695	$ 2,683,434,288	$ 3,457,186,695	$ 2,683,434,288	$ 3,301,943,748
Total revenue	39,235,786	30,675,685	77,864,639	61,000,217
Net interest income	28,046,697	21,008,813	55,715,580	41,606,335
Provision for loan/lease losses	2,022,993	1,197,850	4,128,102	3,270,835
Net income (loss)	8,766,017	6,676,467	17,950,982	13,049,956
Goodwill	13,110,913	3,222,688	13,110,913	3,222,688	13,110,913
Core deposit intangible	6,919,480	1,371,653	6,919,480	1,371,653	$ 7,381,213
Operating Segments [Member] | Commercial Banking Segment [Member] | Quad City Bank and Trust Company [Member]
Total assets	1,400,307,827	1,390,025,232	1,400,307,827	1,390,025,232
Total revenue	14,210,040	14,162,914	27,745,981	27,679,846
Net interest income	11,414,818	11,207,759	22,716,300	22,169,206
Provision for loan/lease losses	552,993	747,850	1,484,102	1,970,835
Net income (loss)	4,073,777	3,898,343	7,728,783	6,730,039
Goodwill	3,222,688	3,222,688	3,222,688	3,222,688
Core deposit intangible
Operating Segments [Member] | Commercial Banking Segment [Member] | Cedar Rapids Bank and Trust [Member]
Total assets	993,768,912	904,367,275	993,768,912	904,367,275
Total revenue	10,149,769	10,438,092	20,536,314	21,277,313
Net interest income	7,230,425	7,135,725	14,204,472	14,160,713
Provision for loan/lease losses	300,000	150,000	550,000	700,000
Net income (loss)	2,870,582	3,144,986	5,763,142	6,079,717
Goodwill
Core deposit intangible	1,172,141	1,371,653	1,172,141	1,371,653
Operating Segments [Member] | Commercial Banking Segment [Member] | Community State Bank [Member]
Total assets	642,761,140		642,761,140
Total revenue	8,171,307		16,303,013
Net interest income	6,920,820		13,947,328
Provision for loan/lease losses	861,000		1,635,000
Net income (loss)	1,920,040		3,815,174
Goodwill	9,888,225		9,888,225
Core deposit intangible	5,747,339		5,747,339
Operating Segments [Member] | Commercial Banking Segment [Member] | Rockford Bank and Trust [Member]
Total assets	426,159,677	402,157,473	426,159,677	402,157,473
Total revenue	4,241,431	3,918,629	8,189,230	7,712,876
Net interest income	3,095,512	2,945,417	6,063,586	5,857,391
Provision for loan/lease losses	309,000	300,000	459,000	600,000
Net income (loss)	834,842	772,169	1,679,411	1,389,954
Goodwill
Core deposit intangible
Operating Segments [Member] | Wealth Management Segment [Member]
Total assets
Total revenue	2,560,836	2,204,821	5,262,642	4,439,113
Net interest income
Provision for loan/lease losses
Net income (loss)	454,465	386,202	1,015,527	833,972
Goodwill
Core deposit intangible
Operating Segments [Member] | Other Segments [Member]
Total assets	382,407,292	328,099,700	382,407,292	328,099,700
Total revenue	10,181,814	8,244,495	20,057,957	15,104,270
Net interest income	(614,878)	(280,088)	(1,216,106)	(580,975)
Provision for loan/lease losses
Net income (loss)	8,766,014	6,676,467	17,950,982	13,049,955
Goodwill
Core deposit intangible
Intersegment Eliminations [Member]
Total assets	(388,218,153)	(341,215,392)	(388,218,153)	(341,215,392)
Total revenue	(10,279,411)	(8,293,266)	(20,230,498)	(15,213,201)
Net interest income
Provision for loan/lease losses
Net income (loss)	(10,153,703)	(8,201,700)	(20,002,037)	(15,033,681)
Goodwill
Core deposit intangible