Note 13 - Junior Subordinated Debentures - Trust Preferred Securities (Details) - USD ($) $ in Thousands		12 Months Ended
	Feb. 12, 2019	Dec. 31, 2020	Dec. 31, 2019
Aggregate principal amount		$ 40,210	$ 40,210
Interest rate (as a percent)		2.48%	4.18%
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	$ 10,310
Interest rate (as a percent)		3.10%	4.79%
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	$ 8,248
Interest rate (as a percent)		3.10%	4.79%
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	$ 10,310
Interest rate (as a percent)		1.79%	3.54%
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	$ 3,093
Interest rate (as a percent)		2.41%	4.08%
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	$ 3,609
Interest rate (as a percent)		1.97%	3.64%
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	$ 4,640
Interest rate (as a percent)		1.97%	3.64%
Trust Preferred Securities [Member] | Guaranty Bankshares Statutory Trust I [Member] | London Interbank Offered Rate (LIBOR)
Variable interest rate (as a percent)		1.75%