Note 7 - Selected Financial Information on the Company's Business Segments (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Operating Segments [Member] | Commercial Banking Segment [Member] | Quad City Bank and Trust Company [Member]
Total revenue	$ 14,162,914	$ 12,930,582	$ 27,679,846	$ 25,732,000
Net interest income	11,207,759	9,741,899	22,169,206	19,016,937
Net income (loss)	3,898,343	229,577	6,730,039	2,792,190
Assets	1,390,025,232	1,299,556,911	1,390,025,232	1,299,556,911
Provision for loan/lease losses	747,850	1,673,665	1,970,835	2,556,121
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 revenue	10,438,092	8,777,259	21,277,313	18,302,906
Net interest income	7,135,725	6,522,511	14,160,713	12,880,808
Net income (loss)	3,144,986	(316,567)	6,079,717	1,751,739
Assets	904,367,275	860,403,296	904,367,275	860,403,296
Provision for loan/lease losses	150,000	500,000	700,000	1,100,000
Goodwill
Core deposit intangible	1,371,653	1,571,165	1,371,653	1,571,165
Operating Segments [Member] | Commercial Banking Segment [Member] | Rockford Bank and Trust [Member]
Total revenue	3,918,629	3,627,740	7,712,876	7,169,330
Net interest income	2,945,417	2,684,330	5,857,391	5,318,412
Net income (loss)	772,169	529,567	1,389,954	1,048,224
Assets	402,157,473	363,049,771	402,157,473	363,049,771
Provision for loan/lease losses	300,000	175,000	600,000	403,000
Goodwill
Core deposit intangible
Operating Segments [Member] | Wealth Management Segment [Member]
Total revenue	2,204,821	2,269,609	4,439,113	4,613,047
Net interest income
Net income (loss)	386,202	438,530	833,972	897,860
Assets
Provision for loan/lease losses
Goodwill
Core deposit intangible
Operating Segments [Member] | Other Segments [Member]
Total revenue	8,244,495	718,325	15,104,270	6,334,768
Net interest income	(280,088)	(457,904)	(580,975)	(943,104)
Net income (loss)	6,676,467	(523,818)	13,049,955	3,654,071
Assets	328,099,700	268,874,722	328,099,700	268,874,722
Provision for loan/lease losses
Goodwill
Core deposit intangible
Intersegment Eliminations [Member]
Total revenue	(8,293,266)	(811,669)	(15,213,201)	(6,516,697)
Net interest income
Net income (loss)	(8,201,700)	(881,107)	(15,033,681)	(6,490,013)
Assets	(341,215,392)	(248,915,854)	(341,215,392)	(248,915,854)
Provision for loan/lease losses
Goodwill
Core deposit intangible
Total revenue	30,675,685	27,511,846	61,000,217	55,635,354
Net interest income	21,008,813	18,490,836	41,606,335	36,273,053
Net income (loss)	6,676,467	(523,818)	13,049,956	3,654,071
Assets	2,683,434,288	2,542,968,846	2,683,434,288	2,542,968,846	$ 2,593,198,275
Provision for loan/lease losses	1,197,850	2,348,665	3,270,835	4,059,121
Goodwill	3,222,688	3,222,688	3,222,688	3,222,688	3,222,688
Core deposit intangible	$ 1,371,653	$ 1,571,165	$ 1,371,653	$ 1,571,165	$ 1,471,409