Note 16 - Regulatory Capital Requirements and Restrictions on Dividends - Capital Requirements (Details) - USD ($)		Dec. 31, 2017	Dec. 31, 2016
Total risk-based capital, actual, amount		$ 383,282	$ 327,440
Total risk-based capital, actual, ratio		11.15%	11.56%
Total risk-based capital for capital adquacy purposes, amount, without capital conservation buffer		$ 275,090	$ 226,587
Total risk-based capital for capital adquacy purposes, ratio, without capital conservation buffer		8.00%	8.00%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 318,073	$ 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		$ 343,862	$ 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		$ 348,530	$ 296,366
Tier 1 risk-based capital, actual, ratio		10.14%	10.46%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 206,317	$ 169,940
Tier 1 risk-based capital for capital adequacy purposes, ratio, without capital conservation buffer		6.00%	6.00%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 249,300	$ 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		$ 275,090	$ 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		$ 348,530	$ 296,366
Tier 1 leverage, actual, ratio		8.98%	9.10%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer		$ 155,256	$ 130,229
Tier 1 leverage for capital adequacy purposes, ratio, without capital conservation buffer		4.00%	4.00%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 155,256	$ 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		$ 194,070	$ 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		$ 313,012	$ 266,419
Common equity Tier 1, actual ratio		9.10%	9.41%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer		$ 154,738	$ 127,455
Common equity Tier 1 for capital adequacy purposes, ratio, without capital conservation buffer		4.50%	4.50%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 197,721	$ 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		$ 223,510	$ 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		$ 160,112	$ 142,990
Total risk-based capital, actual, ratio		12.35%	12.27%
Total risk-based capital for capital adquacy purposes, amount, without capital conservation buffer		$ 103,711	$ 93,212
Total risk-based capital for capital adquacy purposes, ratio, without capital conservation buffer		8.00%	8.00%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 119,916	$ 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		$ 129,639	$ 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		$ 147,472	$ 129,524
Tier 1 risk-based capital, actual, ratio		11.38%	11.12%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 77,783	$ 69,909
Tier 1 risk-based capital for capital adequacy purposes, ratio, without capital conservation buffer		6.00%	6.00%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 93,988	$ 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		$ 103,711	$ 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		$ 147,472	$ 129,524
Tier 1 leverage, actual, ratio		9.52%	9.18%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer		$ 61,985	$ 56,445
Tier 1 leverage for capital adequacy purposes, ratio, without capital conservation buffer		4.00%	4.00%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 61,985	$ 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		$ 77,481	$ 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		$ 147,472	$ 129,524
Common equity Tier 1, actual ratio		11.38%	11.12%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer		$ 58,337	$ 52,432
Common equity Tier 1 for capital adequacy purposes, ratio, without capital conservation buffer		4.50%	4.50%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 74,542	$ 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		$ 84,265	$ 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		$ 138,492	$ 106,791
Total risk-based capital, actual, ratio		11.88%	12.82%
Total risk-based capital for capital adquacy purposes, amount, without capital conservation buffer		$ 93,272	$ 66,623
Total risk-based capital for capital adquacy purposes, ratio, without capital conservation buffer		8.00%	8.00%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 107,846	$ 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		$ 116,590	$ 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		$ 126,601	$ 96,369
Tier 1 risk-based capital, actual, ratio		10.86%	11.57%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 69,954	$ 49,968
Tier 1 risk-based capital for capital adequacy purposes, ratio, without capital conservation buffer		6.00%	6.00%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 84,528	$ 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		$ 93,272	$ 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		$ 126,601	$ 96,369
Tier 1 leverage, actual, ratio		11.68%	10.69%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer		$ 43,348	$ 36,061
Tier 1 leverage for capital adequacy purposes, ratio, without capital conservation buffer		4.00%	4.00%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 43,348	$ 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		$ 54,185	$ 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		$ 126,601	$ 96,369
Common equity Tier 1, actual ratio		10.86%	11.57%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer		$ 52,465	$ 37,476
Common equity Tier 1 for capital adequacy purposes, ratio, without capital conservation buffer		4.50%	4.50%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 67,039	$ 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		$ 75,783	$ 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		$ 66,271	$ 68,216
Total risk-based capital, actual, ratio		11.71%	13.81%
Total risk-based capital for capital adquacy purposes, amount, without capital conservation buffer		$ 45,293	$ 39,521
Total risk-based capital for capital adquacy purposes, ratio, without capital conservation buffer		8.00%	8.00%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 52,370	$ 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		$ 56,616	$ 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		$ 61,941	$ 66,746
Tier 1 risk-based capital, actual, ratio		10.94%	13.51%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 33,970	$ 29,641
Tier 1 risk-based capital for capital adequacy purposes, ratio, without capital conservation buffer		6.00%	6.00%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 41,047	$ 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		$ 45,293	$ 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		$ 61,941	$ 66,746
Tier 1 leverage, actual, ratio		9.77%	11.75%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer		$ 25,354	$ 22,726
Tier 1 leverage for capital adequacy purposes, ratio, without capital conservation buffer		4.00%	4.00%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 25,354	$ 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		$ 31,693	$ 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		$ 61,941	$ 66,746
Common equity Tier 1, actual ratio		10.94%	13.51%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer		$ 25,477	$ 22,231
Common equity Tier 1 for capital adequacy purposes, ratio, without capital conservation buffer		4.50%	4.50%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 32,554	$ 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		$ 36,801	$ 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		$ 45,684	$ 42,007
Total risk-based capital, actual, ratio		11.28%	12.26%
Total risk-based capital for capital adquacy purposes, amount, without capital conservation buffer		$ 32,413	$ 27,410
Total risk-based capital for capital adquacy purposes, ratio, without capital conservation buffer		8.00%	8.00%
Total risk-based capital for capital adquacy purposes, amount	[1]	$ 37,477	$ 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		$ 40,516	$ 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		$ 40,615	$ 37,716
Tier 1 risk-based capital, actual, ratio		10.02%	11.01%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 24,310	$ 20,558
Tier 1 risk-based capital for capital adequacy purposes, ratio, without capital conservation buffer		6.00%	6.00%
Tier 1 risk-based capital for capital adequacy purposes, amount	[1]	$ 29,374	$ 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		$ 32,413	$ 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		$ 40,615	$ 37,716
Tier 1 leverage, actual, ratio		8.94%	9.57%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer		$ 18,177	$ 15,772
Tier 1 leverage for capital adequacy purposes, ratio, without capital conservation buffer		4.00%	4.00%
Tier 1 leverage for capital adequacy purposes, amount	[1]	$ 18,177	$ 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		$ 22,721	$ 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		$ 40,615	$ 37,716
Common equity Tier 1, actual ratio		10.02%	11.01%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer		$ 18,232	$ 15,418
Common equity Tier 1 for capital adequacy purposes, ratio, without capital conservation buffer		4.50%	4.50%
Common equity Tier 1 for capital adequacy purposes, amount	[1]	$ 23,297	$ 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		$ 26,335	$ 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 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).