Note 12 - Junior Subordinated Debentures - Trust Preferred Securities (Details) - USD ($)		12 Months Ended
	Feb. 12, 2019	Dec. 31, 2018	Dec. 31, 2017
Aggregate principal amount		$ 40,210,000	$ 40,210,000
Interest rate (as a percent)		4.94%	3.82%
London Interbank Offered Rate (LIBOR)
Variable interest rate (as a percent)	282.00%
Trust Preferred Securities [Member] | Qcr Holdings Statutory Trust I I Member
Date issued		February 2004
Aggregate principal amount		$ 10,310,000	$ 10,310,000
Interest rate (as a percent)		5.65%	4.54%
Trust Preferred Securities [Member] | Qcr Holdings Statutory Trust I I Member | London Interbank Offered Rate (LIBOR)
Variable interest rate (as a percent)		2.85%
Trust Preferred Securities [Member] | QCR Holdings Statutory Trust III [Member]
Date issued		February 2004
Aggregate principal amount		$ 8,248,000	$ 8,248,000
Interest rate (as a percent)		5.65%	4.54%
Trust Preferred Securities [Member] | QCR Holdings Statutory Trust III [Member] | London Interbank Offered Rate (LIBOR)
Variable interest rate (as a percent)		2.85%
Trust Preferred Securities [Member] | QCR Holdings Statutory Trust V [Member]
Date issued		February 2006
Aggregate principal amount		$ 10,310,000	$ 10,310,000
Interest rate (as a percent)		3.99%	2.91%
Trust Preferred Securities [Member] | QCR Holdings Statutory Trust V [Member] | London Interbank Offered Rate (LIBOR)
Variable interest rate (as a percent)		1.55%
Trust Preferred Securities [Member] | Community National Statutory Trust II [Member]
Date issued		September 2004
Aggregate principal amount		$ 3,093,000	$ 3,093,000
Interest rate (as a percent)		4.96%	3.80%
Trust Preferred Securities [Member] | Community National Statutory Trust II [Member] | London Interbank Offered Rate (LIBOR)
Variable interest rate (as a percent)		2.17%
Trust Preferred Securities [Member] | Community National Statutory Trust III [Member]
Date issued		March 2007
Aggregate principal amount		$ 3,609,000	$ 3,609,000
Interest rate (as a percent)		4.54%	3.32%
Trust Preferred Securities [Member] | Community National Statutory Trust III [Member] | London Interbank Offered Rate (LIBOR)
Variable interest rate (as a percent)		1.75%
Trust Preferred Securities [Member] | Guaranty Bankshares Statutory Trust I [Member]
Date issued		May 2005
Aggregate principal amount		$ 4,640,000	$ 4,640,000
Interest rate (as a percent)		4.54%	3.34%
Trust Preferred Securities [Member] | Guaranty Bankshares Statutory Trust I [Member] | London Interbank Offered Rate (LIBOR)
Variable interest rate (as a percent)		1.75%