Note 22 - Business Segment Information - Selected Financial Information on the Company's Business Segments (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Total income									$ 137,504,610	$ 114,366,574	$ 107,246,535
Net interest income	$ 29,279,665	$ 23,630,777	$ 21,008,813	$ 20,597,522	$ 19,886,145	$ 20,137,526	$ 18,490,836	$ 17,782,217	94,516,777	76,296,724	69,071,128
Provision for loan/lease losses	2,599,345	1,607,986	1,197,850	2,072,985	1,176,516	1,635,263	2,348,665	1,710,456	7,478,166	6,870,900	6,807,000
Net income (loss)									27,686,787	16,927,881
Goodwill	13,110,913				3,222,688				13,110,913	3,222,688	3,222,688
Core deposit intangible	7,381,213				1,471,409				7,381,213	1,471,409	1,670,921
Total assets	3,301,943,748				2,593,198,275				3,301,943,748	2,593,198,275	2,524,958,100
Net income	8,529,330	$ 6,107,501	$ 6,676,467	$ 6,373,489	6,784,823	$ 6,488,987	$ (523,818)	$ 4,177,889	27,686,787	16,927,881	14,952,537
Operating Segments [Member] | Commercial Banking Segment [Member] | Quad City Bank and Trust Company [Member]
Total income									59,442,052	52,914,705	48,878,342
Net interest income									45,081,080	40,416,563	36,539,635
Provision for loan/lease losses									4,168,166	4,367,234	3,800,667
Net income (loss)									14,116,751	10,333,111
Goodwill	3,222,688				3,222,688				3,222,688	3,222,688	3,222,688
Core deposit intangible
Total assets	1,395,785,241				1,336,571,694				1,395,785,241	1,336,571,694	1,320,684,456
Net income											9,065,183
Operating Segments [Member] | Commercial Banking Segment [Member] | Cedar Rapids Bank and Trust [Member]
Total income									37,242,901	37,593,652	35,972,996
Net interest income									29,205,047	26,635,659	24,215,815
Provision for loan/lease losses									950,000	1,750,000	1,855,333
Net income (loss)									12,317,545	7,695,867
Goodwill
Core deposit intangible	1,271,897				1,471,409				1,271,897	1,471,409	1,670,921
Total assets	913,055,738				866,872,406				913,055,738	866,872,406	840,331,777
Net income											7,562,252
Operating Segments [Member] | Commercial Banking Segment [Member] | Community State Bank [Member]
Total income									11,408,277
Net interest income									10,004,729
Provision for loan/lease losses									1,460,000
Net income (loss)									2,132,252
Goodwill	9,888,225								9,888,225
Core deposit intangible	6,109,316								6,109,316
Total assets	600,075,798								600,075,798
Net income
Operating Segments [Member] | Commercial Banking Segment [Member] | Rockford Bank and Trust [Member]
Total income									16,043,894	14,816,300	14,286,757
Net interest income									11,887,201	10,854,637	10,261,615
Provision for loan/lease losses									900,000	753,666	1,151,000
Net income (loss)									3,235,711	2,402,522
Goodwill
Core deposit intangible
Total assets	391,154,780				367,471,639				391,154,780	367,471,639	353,448,134
Net income											2,149,676
Operating Segments [Member] | Wealth Management Segment [Member]
Total income									9,156,948	9,103,173	8,513,322
Net interest income
Provision for loan/lease losses
Net income (loss)									1,665,453	1,627,586
Goodwill
Core deposit intangible
Total assets
Net income											1,556,082
Operating Segments [Member] | Other Segments [Member]
Total income									109,563	363,432	80,978
Net interest income									(1,661,280)	(1,610,135)	(1,945,937)
Provision for loan/lease losses
Net income (loss)									(5,780,925)	(5,131,205)
Goodwill
Core deposit intangible
Total assets	34,998,902				27,605,704				34,998,902	27,605,704	17,727,123
Net income											(5,380,656)
Intersegment Eliminations [Member]
Total income									4,100,975	(424,688)	(485,860)
Net interest income
Provision for loan/lease losses
Net income (loss)
Goodwill
Core deposit intangible
Total assets	$ (33,126,711)				$ (5,323,168)				$ (33,126,711)	$ (5,323,168)	(7,233,390)
Net income