Note 8 - Regulatory Capital Requirements - Capital Requirements (Details) - USD ($)		Sep. 30, 2016	Dec. 31, 2015
Parent Company [Member]
Total risk-based capital, actual, amount		$ 316,063	$ 280,273
Total risk-based capital, actual, ratio		11.33%	13.11%
Total risk-based capital for capital adequacy purposes, amount	[1]	$ 240,629	$ 170,969
Total risk-based capital for capital adequacy purposes, ratio	[1]	8.625%	8.00%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 278,991	$ 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		$ 287,015	$ 253,891
Tier 1 risk-based capital, actual, ratio		10.29%	11.88%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 184,831	$ 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		$ 223,192	$ 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		$ 287,015	$ 253,891
Tier 1 leverage, actual, ratio		10.09%	9.75%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 113,737	$ 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		$ 142,172	$ 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		$ 257,119	$ 220,800
Common equity Tier 1, actual ratio		9.22%	10.33%
Common equity Tier 1 capital adequacy purposes, amount	[1]	$ 142,983	$ 96,170
Common equity Tier 1 capital adequacy purposes, ratio	[1]	5.125%	4.50%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 181,344	$ 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		$ 138,333	$ 135,477
Total risk-based capital, actual, ratio		11.71%	12.50%
Total risk-based capital for capital adequacy purposes, amount	[1]	$ 101,861	$ 86,726
Total risk-based capital for capital adequacy purposes, ratio	[1]	8.625%	8.00%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 118,100	$ 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		$ 125,410	$ 123,498
Tier 1 risk-based capital, actual, ratio		10.62%	11.39%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 78,241	$ 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		$ 94,480	$ 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		$ 125,410	$ 123,498
Tier 1 leverage, actual, ratio		8.86%	8.87%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 56,628	$ 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		$ 70,785	$ 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		$ 125,410	$ 123,498
Common equity Tier 1, actual ratio		10.62%	11.39%
Common equity Tier 1 capital adequacy purposes, amount	[1]	$ 60,526	$ 48,783
Common equity Tier 1 capital adequacy purposes, ratio	[1]	5.125%	4.50%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 76,765	$ 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		$ 104,206	$ 105,285
Total risk-based capital, actual, ratio		13.13%	14.39%
Total risk-based capital for capital adequacy purposes, amount	[1]	$ 68,474	$ 58,537
Total risk-based capital for capital adequacy purposes, ratio	[1]	8.625%	8.00%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 79,390	$ 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		$ 94,266	$ 96,118
Tier 1 risk-based capital, actual, ratio		11.87%	13.14%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 52,596	$ 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		$ 63,512	$ 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		$ 94,266	$ 96,118
Tier 1 leverage, actual, ratio		10.36%	10.96%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 36,407	$ 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		$ 45,509	$ 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		$ 94,266	$ 96,118
Common equity Tier 1, actual ratio		11.87%	13.14%
Common equity Tier 1 capital adequacy purposes, amount	[1]	$ 40,687	$ 32,927
Common equity Tier 1 capital adequacy purposes, ratio	[1]	5.125%	4.50%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 51,604	$ 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		$ 67,008
Total risk-based capital, actual, ratio		14.09%
Total risk-based capital for capital adequacy purposes, amount	[1]	$ 41,031
Total risk-based capital for capital adequacy purposes, ratio	[1]	8.625%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 47,572
Total risk-based capital to be well capitalized under prompt corrective action provisions, ratio		10.00%
Tier 1 risk-based capital, actual, amount		$ 66,735
Tier 1 risk-based capital, actual, ratio		14.03%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 31,516
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		$ 38,058
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio		8.00%
Tier 1 leverage, actual, amount		$ 66,735
Tier 1 leverage, actual, ratio		11.74%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 22,745
Tier 1 leverage for capital adequacy purposes, ratio	[1]	4.00%
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount		$ 28,431
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio		5.00%
Common equity Tier 1, actual, amount		$ 66,735
Common equity Tier 1, actual ratio		14.03%
Common equity Tier 1 capital adequacy purposes, amount	[1]	$ 24,381
Common equity Tier 1 capital adequacy purposes, ratio	[1]	5.125%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 30,922
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		$ 41,130	$ 38,544
Total risk-based capital, actual, ratio		11.95%	11.96%
Total risk-based capital for capital adequacy purposes, amount		$ 29,680	$ 25,772	[1]
Total risk-based capital for capital adequacy purposes, ratio		8.625%	8.00%	[1]
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 34,412	$ 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		$ 36,821	$ 34,514
Tier 1 risk-based capital, actual, ratio		10.70%	10.71%
Tier 1 risk-based capital for capital adequacy purposes, amount		$ 22,798	$ 19,329	[1]
Tier 1 risk-based capital for capital adequacy purposes, ratio		6.625%	6.00%	[1]
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount		$ 27,529	$ 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		$ 36,821	$ 34,514
Tier 1 leverage, actual, ratio		9.45%	9.59%
Tier 1 leverage for capital adequacy purposes, amount		$ 15,587	$ 14,401	[1]
Tier 1 leverage for capital adequacy purposes, ratio		4.00%	4.00%	[1]
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount		$ 19,484	$ 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		$ 36,821	$ 34,514
Common equity Tier 1, actual ratio		10.70%	10.71%
Common equity Tier 1 capital adequacy purposes, amount		$ 17,636	$ 14,497	[1]
Common equity Tier 1 capital adequacy purposes, ratio		5.125%	4.50%	[1]
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount		$ 22,367	$ 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) 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 occured in 2016.