Note 12 - Junior Subordinated Debentures - Trust Preferred Securities (Details) - USD ($)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Amount Outstanding		$ 40,210,000	$ 35,570,000
Interest Rate		3.82%	3.26%
Trust Preferred Securities [Member] | QCR Holdings Statuory Trust II [Member]
Date issued	[1]	February 2004
Amount Outstanding	[1]	$ 10,310,000	$ 10,310,000
Interest Rate	[1]	4.54%	3.85%
Trust Preferred Securities [Member] | QCR Holdings Statuory Trust II [Member] | London Interbank Offered Rate (LIBOR) [Member]
Interest Rate, Basis Spread	[1]	2.85%
Trust Preferred Securities [Member] | QCR Holdings Statutory Trust III [Member]
Date issued		February 2004
Amount Outstanding		$ 8,248,000	$ 8,248,000
Interest Rate		4.54%	3.85%
Trust Preferred Securities [Member] | QCR Holdings Statutory Trust III [Member] | London Interbank Offered Rate (LIBOR) [Member]
Interest Rate, Basis Spread		2.85%
Trust Preferred Securities [Member] | QCR Holdings Statutory Trust V [Member]
Date issued		February 2006
Amount Outstanding		$ 10,310,000	$ 10,310,000
Interest Rate		2.91%	2.43%
Trust Preferred Securities [Member] | QCR Holdings Statutory Trust V [Member] | London Interbank Offered Rate (LIBOR) [Member]
Interest Rate, Basis Spread		1.55%
Trust Preferred Securities [Member] | Community National Statutory Trust II [Member]
Date issued		September 2004
Amount Outstanding		$ 3,093,000	$ 3,093,000
Interest Rate		3.80%	3.17%
Trust Preferred Securities [Member] | Community National Statutory Trust II [Member] | London Interbank Offered Rate (LIBOR) [Member]
Interest Rate, Basis Spread		2.17%
Trust Preferred Securities [Member] | Community National Statutory Trust III [Member]
Date issued		March 2007
Amount Outstanding		$ 3,609,000	$ 3,609,000
Interest Rate		3.32%	2.71%
Trust Preferred Securities [Member] | Community National Statutory Trust III [Member] | London Interbank Offered Rate (LIBOR) [Member]
Interest Rate, Basis Spread		1.75%
Trust Preferred Securities [Member] | Guaranty Bankshares Statutory Trust I [Member]
Date issued		May 2005
Amount Outstanding		$ 4,640,000
Interest Rate		3.34%
Trust Preferred Securities [Member] | Guaranty Bankshares Statutory Trust I [Member] | London Interbank Offered Rate (LIBOR) [Member]
Interest Rate, Basis Spread		1.75%

[1] Original amount issued for QCR Holdings Statutory Trust II was $12,372,000.