Note 16 - Regulatory Capital Requirements and Restrictions on Dividends - Capital Requirements (Details) - USD ($)		Dec. 31, 2016	Dec. 31, 2015
Parent Company [Member]
Total risk-based capital, actual, amount		$ 327,440	$ 280,273
Total risk-based capital, actual, ratio		11.56%	13.11%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 244,289	$ 170,969
Total risk-based capital for capital adquacy purposes, ratio	[1]	8.625%	8.00%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 283,233	$ 213,711
Total risk-based capital to be well capitalized under prompt corrective action provisions, ratio		10.00%	10.00%
Tier 1 risk-based capital, actual, amount		$ 296,366	$ 253,891
Tier 1 risk-based capital, actual, ratio		10.46%	11.88%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 187,642	$ 128,227
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	6.625%	6.00%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 226,587	$ 170,969
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio		8.00%	8.00%
Tier 1 leverage, actual, amount		$ 296,366	$ 253,891
Tier 1 leverage, actual, ratio		9.10%	9.75%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 130,229	$ 104,163
Tier 1 leverage for capital adequacy purposes, ratio	[1]	4.00%	4.00%
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount		$ 162,787	$ 130,203
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio		5.00%	5.00%
Common equity Tier 1, actual, amount		$ 266,419	$ 220,800
Common equity Tier 1, actual ratio		9.41%	10.33%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 145,157	$ 96,170
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	5.125%	4.50%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 184,102	$ 138,912
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, ratio		6.50%	6.50%
Quad City Bank and Trust Company [Member]
Total risk-based capital, actual, amount		$ 142,990	$ 135,477
Total risk-based capital, actual, ratio		12.27%	12.50%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 100,494	$ 86,726
Total risk-based capital for capital adquacy purposes, ratio	[1]	8.625%	8.00%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 116,515	$ 108,407
Total risk-based capital to be well capitalized under prompt corrective action provisions, ratio		10.00%	10.00%
Tier 1 risk-based capital, actual, amount		$ 129,524	$ 123,498
Tier 1 risk-based capital, actual, ratio		11.12%	11.39%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 77,191	$ 65,044
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	6.625%	6.00%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 93,212	$ 86,726
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio		8.00%	8.00%
Tier 1 leverage, actual, amount		$ 129,524	$ 123,498
Tier 1 leverage, actual, ratio		9.18%	8.87%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 56,445	$ 55,718
Tier 1 leverage for capital adequacy purposes, ratio	[1]	4.00%	4.00%
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount		$ 70,556	$ 69,648
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio		5.00%	5.00%
Common equity Tier 1, actual, amount		$ 129,524	$ 123,498
Common equity Tier 1, actual ratio		11.12%	11.39%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 59,714	$ 48,783
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	5.125%	4.50%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 75,735	$ 70,465
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, ratio		6.50%	6.50%
Cedar Rapids Bank and Trust [Member]
Total risk-based capital, actual, amount		$ 106,791	$ 105,285
Total risk-based capital, actual, ratio		12.82%	14.39%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 71,828	$ 58,537
Total risk-based capital for capital adquacy purposes, ratio	[1]	8.625%	8.00%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 83,279	$ 73,172
Total risk-based capital to be well capitalized under prompt corrective action provisions, ratio		10.00%	10.00%
Tier 1 risk-based capital, actual, amount		$ 96,369	$ 96,118
Tier 1 risk-based capital, actual, ratio		11.57%	13.14%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 55,173	$ 43,903
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	6.625%	6.00%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 66,623	$ 58,537
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio		8.00%	8.00%
Tier 1 leverage, actual, amount		$ 96,369	$ 96,118
Tier 1 leverage, actual, ratio		10.69%	10.96%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 36,061	$ 35,079
Tier 1 leverage for capital adequacy purposes, ratio	[1]	4.00%	4.00%
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount		$ 45,076	$ 43,848
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio		5.00%	5.00%
Common equity Tier 1, actual, amount		$ 96,369	$ 96,118
Common equity Tier 1, actual ratio		11.57%	13.14%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 42,681	$ 32,927
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	5.125%	4.50%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 54,132	$ 47,562
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, ratio		6.50%	6.50%
Community State Bank [Member]
Total risk-based capital, actual, amount		$ 68,216
Total risk-based capital, actual, ratio		13.81%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 42,609
Total risk-based capital for capital adquacy purposes, ratio	[1]	8.625%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 49,402
Total risk-based capital to be well capitalized under prompt corrective action provisions, ratio		10.00%
Tier 1 risk-based capital, actual, amount		$ 66,746
Tier 1 risk-based capital, actual, ratio		13.51%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 32,729
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	6.625%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 39,522
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio		8.00%
Tier 1 leverage, actual, amount		$ 66,746
Tier 1 leverage, actual, ratio		11.75%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 22,726
Tier 1 leverage for capital adequacy purposes, ratio	[1]	4.00%
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount		$ 28,408
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio		5.00%
Common equity Tier 1, actual, amount		$ 66,746
Common equity Tier 1, actual ratio		13.51%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 25,319
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	5.125%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 32,111
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, ratio		6.50%
Rockford Bank and Trust [Member]
Total risk-based capital, actual, amount		$ 42,007	$ 38,544
Total risk-based capital, actual, ratio		12.26%	11.96%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 29,551	$ 25,772
Total risk-based capital for capital adquacy purposes, ratio	[1]	8.625%	8.00%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 34,262	$ 32,216
Total risk-based capital to be well capitalized under prompt corrective action provisions, ratio		10.00%	10.00%
Tier 1 risk-based capital, actual, amount		$ 37,716	$ 34,514
Tier 1 risk-based capital, actual, ratio		11.01%	10.71%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 22,699	$ 19,329
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	6.625%	6.00%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 27,410	$ 25,772
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio		8.00%	8.00%
Tier 1 leverage, actual, amount		$ 37,716	$ 34,514
Tier 1 leverage, actual, ratio		9.57%	9.59%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 15,772	$ 14,401
Tier 1 leverage for capital adequacy purposes, ratio	[1]	4.00%	4.00%
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount		$ 19,716	$ 18,001
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio		5.00%	5.00%
Common equity Tier 1, actual, amount		$ 37,716	$ 34,514
Common equity Tier 1, actual ratio		11.01%	10.71%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 17,559	$ 14,497
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	5.125%	4.50%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 22,270	$ 20,940
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, ratio		6.50%	6.50%

[1] The minimums under Basel III phase in higher by .625% (the capital conservation buffer) for all ratios other than Tier 1 leverage annually until 2019. The fully phased-in minimums are 10.5% (Total risk-based capital), 8.5% (Tier 1 risk-based capital), and 7.0% (Common equity Tier 1). At December 31, 2015, the New Basel III minimums mirrored the minimums required for capital adequacy purposes. The first phase-in of the Basel III capital conservation buffer occurred in 2016.