Note 7 - Regulatory Capital Requirements and Restrictions on Dividends - Capital Requirements (Details) - USD ($)		Mar. 31, 2017	Dec. 31, 2016
Parent Company [Member]
Total risk-based capital, actual, amount		$ 336,993	$ 327,440
Total risk-based capital, actual, ratio		11.90%	11.56%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 262,053	$ 244,289
Total risk-based capital for capital adquacy purposes, ratio	[1]	9.25%	8.625%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 283,300	$ 283,233
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		$ 304,594	$ 296,366
Tier 1 risk-based capital, actual, ratio		10.75%	10.46%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 205,393	$ 187,642
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	7.25%	6.625%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 226,640	$ 226,587
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio		8.00%	8.00%
Tier 1 leverage, actual, amount		$ 304,594	$ 296,366
Tier 1 leverage, actual, ratio		9.37%	9.10%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 129,996	$ 130,229
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		$ 162,495	$ 162,787
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio		5.00%	5.00%
Common equity Tier 1, actual, amount		$ 273,076	$ 266,419
Common equity Tier 1, actual ratio		9.64%	9.41%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 162,898	$ 145,157
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	5.75%	5.125%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 184,145	$ 184,102
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		$ 145,432	$ 142,990
Total risk-based capital, actual, ratio		12.61%	12.27%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 106,664	$ 100,494
Total risk-based capital for capital adquacy purposes, ratio	[1]	9.25%	8.625%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 115,312	$ 116,515
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		$ 131,860	$ 129,524
Tier 1 risk-based capital, actual, ratio		11.44%	11.12%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 83,601	$ 77,191
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	7.25%	6.625%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 92,250	$ 93,212
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio		8.00%	8.00%
Tier 1 leverage, actual, amount		$ 131,860	$ 129,524
Tier 1 leverage, actual, ratio		9.25%	9.18%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 57,045	$ 56,445
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		$ 71,306	$ 70,556
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio		5.00%	5.00%
Common equity Tier 1, actual, amount		$ 131,860	$ 129,524
Common equity Tier 1, actual ratio		11.44%	11.12%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 66,304	$ 59,714
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	5.75%	5.125%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 74,953	$ 75,735
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		$ 107,776	$ 106,791
Total risk-based capital, actual, ratio		12.79%	12.82%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 77,956	$ 71,828
Total risk-based capital for capital adquacy purposes, ratio	[1]	9.25%	8.625%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 84,277	$ 83,279
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		$ 97,230	$ 96,369
Tier 1 risk-based capital, actual, ratio		11.54%	11.57%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 61,101	$ 55,173
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	7.25%	6.625%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 67,421	$ 66,623
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio		8.00%	8.00%
Tier 1 leverage, actual, amount		$ 97,230	$ 96,369
Tier 1 leverage, actual, ratio		10.74%	10.69%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 36,206	$ 36,061
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		$ 45,257	$ 45,076
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio		5.00%	5.00%
Common equity Tier 1, actual, amount		$ 97,230	$ 96,369
Common equity Tier 1, actual ratio		11.54%	11.57%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 48,459	$ 42,681
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	5.75%	5.125%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 54,780	$ 54,132
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		$ 66,300	$ 68,216
Total risk-based capital, actual, ratio		13.50%	13.81%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 45,426	$ 42,609
Total risk-based capital for capital adquacy purposes, ratio	[1]	9.25%	8.625%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 49,109	$ 49,402
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		$ 64,052	$ 66,746
Tier 1 risk-based capital, actual, ratio		13.04%	13.51%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 35,604	$ 32,729
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	7.25%	6.625%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 39,287	$ 39,522
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio		8.00%	8.00%
Tier 1 leverage, actual, amount		$ 64,052	$ 66,746
Tier 1 leverage, actual, ratio		10.99%	11.75%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 23,317	$ 22,726
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		$ 29,146	$ 28,408
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio		5.00%	5.00%
Common equity Tier 1, actual, amount		$ 64,052	$ 66,746
Common equity Tier 1, actual ratio		13.04%	13.51%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 28,238	$ 25,319
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	5.75%	5.125%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 31,921	$ 32,111
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, ratio		6.50%	6.50%
Rockford Bank and Trust [Member]
Total risk-based capital, actual, amount		$ 42,916	$ 42,007
Total risk-based capital, actual, ratio		12.31%	12.26%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 32,256	$ 29,551
Total risk-based capital for capital adquacy purposes, ratio	[1]	9.25%	8.625%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 34,871	$ 34,262
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		$ 38,548	$ 37,716
Tier 1 risk-based capital, actual, ratio		11.05%	11.01%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 25,282	$ 22,699
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	7.25%	6.625%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 27,897	$ 27,410
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio		8.00%	8.00%
Tier 1 leverage, actual, amount		$ 38,548	$ 37,716
Tier 1 leverage, actual, ratio		9.82%	9.57%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 15,707	$ 15,772
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		$ 19,634	$ 19,716
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio		5.00%	5.00%
Common equity Tier 1, actual, amount		$ 38,548	$ 37,716
Common equity Tier 1, actual ratio		11.05%	11.01%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 20,051	$ 17,559
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	5.75%	5.125%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 22,666	$ 22,270
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, ratio		6.50%	6.50%

[1] The minimums under Basel III increase by .625% (the capital conservation buffer) 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).