Note 12 - Junior Subordinated Debentures - Junior Subordinated Debentures (Details) - USD ($)		Dec. 31, 2017	Dec. 31, 2016
Junior subordinated debentures		$ 37,486,487	$ 33,480,202
Junior subordinated debentures	[1]	(2,723,513)	(2,089,798)
Note Payable to QCR Holdings Capital Trust II [Member]
Junior subordinated debentures		10,310,000	10,310,000
Note Payable to Trust III [Member]
Junior subordinated debentures		8,248,000	8,248,000
Note Payable to Trust V [Member]
Junior subordinated debentures		10,310,000	10,310,000
Community National Trust II [Member]
Junior subordinated debentures		3,093,000	3,093,000
Community National Trust III [Member]
Junior subordinated debentures		3,609,000	3,609,000
Note Payable to Guaranty Bankshares Statutory Trust I [Member]
Junior subordinated debentures	[2]	$ 4,640,000

[1] Discount on junior subordinated debt acquired in 2013 as part of the purchase of Community National and junior subordinated debt acquired in 2017 as part of the purchase of Guaranty Bank.

[2] As part of the acquisition of Guaranty Bank, the Company assumed one junior subordinated debenture with a fair value of $3,857,275.