Note 9 - Regulatory Capital Requirements and Restrictions on Dividends - Capital Requirements (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Total risk-based capital, actual, amount	$ 449,655	$ 383,282
Total risk-based capital, actual, ratio	10.87%	11.15%
Total risk-based capital for capital adequacy purposes, amount, without capital conservation buffer	$ 330,798	$ 275,090
Capital Required For Capital Adequacy Excluding Capital Conservation Buffer	$ 330,798	$ 275,090
Total risk-based capital for capital adequacy purposes, ratio, without capital conservation buffer	8.00%	8.00%
Total risk-based capital for capital adequacy purposes, amount	$ 408,329	$ 318,073
Total risk-based capital for capital adequacy purposes, ratio	9.875%	9.25%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 413,497	$ 343,862
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	$ 406,578	$ 348,530
Tier 1 risk-based capital, actual, ratio	9.83%	10.14%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer	$ 248,098	$ 206,317
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	$ 325,629	$ 249,300
Tier 1 risk-based capital for capital adequacy purposes, ratio	7.875%	7.25%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 330,798	$ 275,090
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio	8.00%	8.00%
Tier 1 leverage, actual, amount	$ 406,578	$ 348,530
Tier 1 leverage, actual, ratio	8.87%	8.98%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer	$ 183,278	$ 155,256
Tier 1 leverage for capital adequacy purposes, ratio, without capital conservation buffer	4.00%	4.00%
Tier 1 leverage for capital adequacy purposes, amount	$ 183,278	$ 155,256
Tier 1 leverage for capital adequacy purposes, ratio	4.00%	4.00%
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount	$ 229,098	$ 194,070
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio	5.00%	5.00%
Common equity Tier 1, actual, amount	$ 368,952	$ 313,012
Common equity Tier 1, actual ratio	8.92%	9.10%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer	$ 186,074	$ 154,738
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	$ 263,605	$ 197,721
Common equity Tier 1 for capital adequacy purposes, ratio	6.375%	5.75%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount	$ 268,773	$ 223,510
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	$ 160,806	$ 160,112
Total risk-based capital, actual, ratio	11.72%	12.35%
Total risk-based capital for capital adequacy purposes, amount, without capital conservation buffer	$ 109,744	$ 103,711
Capital Required For Capital Adequacy Excluding Capital Conservation Buffer	$ 109,744	$ 103,711
Total risk-based capital for capital adequacy purposes, ratio, without capital conservation buffer	8.00%	8.00%
Total risk-based capital for capital adequacy purposes, amount	$ 135,466	$ 119,916
Total risk-based capital for capital adequacy purposes, ratio	9.875%	9.25%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 137,180	$ 129,639
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	$ 147,532	$ 147,472
Tier 1 risk-based capital, actual, ratio	10.75%	11.38%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer	$ 82,308	$ 77,783
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	$ 108,029	$ 93,988
Tier 1 risk-based capital for capital adequacy purposes, ratio	7.875%	7.25%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 109,744	$ 103,711
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio	8.00%	8.00%
Tier 1 leverage, actual, amount	$ 147,532	$ 147,472
Tier 1 leverage, actual, ratio	9.32%	9.52%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer	$ 63,297	$ 61,985
Tier 1 leverage for capital adequacy purposes, ratio, without capital conservation buffer	4.00%	4.00%
Tier 1 leverage for capital adequacy purposes, amount	$ 63,297	$ 61,985
Tier 1 leverage for capital adequacy purposes, ratio	4.00%	4.00%
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount	$ 79,121	$ 77,481
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio	5.00%	5.00%
Common equity Tier 1, actual, amount	$ 147,532	$ 147,472
Common equity Tier 1, actual ratio	10.75%	11.38%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer	$ 61,731	$ 58,337
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	$ 87,452	$ 74,542
Common equity Tier 1 for capital adequacy purposes, ratio	6.375%	5.75%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount	$ 89,167	$ 84,265
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	$ 145,066	$ 138,492
Total risk-based capital, actual, ratio	11.79%	11.88%
Total risk-based capital for capital adequacy purposes, amount, without capital conservation buffer	$ 98,462	$ 93,272
Capital Required For Capital Adequacy Excluding Capital Conservation Buffer	$ 98,462	$ 93,272
Total risk-based capital for capital adequacy purposes, ratio, without capital conservation buffer	8.00%	8.00%
Total risk-based capital for capital adequacy purposes, amount	$ 121,540	$ 107,846
Total risk-based capital for capital adequacy purposes, ratio	9.875%	9.25%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 123,078	$ 116,590
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	$ 131,839	$ 126,601
Tier 1 risk-based capital, actual, ratio	10.71%	10.86%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer	$ 73,847	$ 69,954
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	$ 96,924	$ 84,528
Tier 1 risk-based capital for capital adequacy purposes, ratio	7.875%	7.25%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 98,462	$ 93,272
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio	8.00%	8.00%
Tier 1 leverage, actual, amount	$ 131,839	$ 126,601
Tier 1 leverage, actual, ratio	9.83%	11.68%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer	$ 53,659	$ 43,348
Tier 1 leverage for capital adequacy purposes, ratio, without capital conservation buffer	4.00%	4.00%
Tier 1 leverage for capital adequacy purposes, amount	$ 53,659	$ 43,348
Tier 1 leverage for capital adequacy purposes, ratio	4.00%	4.00%
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount	$ 67,074	$ 54,185
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio	5.00%	5.00%
Common equity Tier 1, actual, amount	$ 131,839	$ 126,601
Common equity Tier 1, actual ratio	10.71%	10.86%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer	$ 55,385	$ 52,465
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	$ 78,462	$ 67,039
Common equity Tier 1 for capital adequacy purposes, ratio	6.375%	5.75%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount	$ 80,001	$ 75,783
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	$ 72,601	$ 66,271
Total risk-based capital, actual, ratio	11.43%	11.71%
Total risk-based capital for capital adequacy purposes, amount, without capital conservation buffer	$ 50,801	$ 45,293
Capital Required For Capital Adequacy Excluding Capital Conservation Buffer	$ 50,801	$ 45,293
Total risk-based capital for capital adequacy purposes, ratio, without capital conservation buffer	8.00%	8.00%
Total risk-based capital for capital adequacy purposes, amount	$ 62,708	$ 52,370
Total risk-based capital for capital adequacy purposes, ratio	9.875%	9.25%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 63,501	$ 56,616
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	$ 67,149	$ 61,941
Tier 1 risk-based capital, actual, ratio	10.57%	10.94%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer	$ 38,101	$ 33,970
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	$ 50,007	$ 41,047
Tier 1 risk-based capital for capital adequacy purposes, ratio	7.875%	7.25%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 50,801	$ 45,293
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio	8.00%	8.00%
Tier 1 leverage, actual, amount	$ 67,149	$ 61,941
Tier 1 leverage, actual, ratio	9.62%	9.77%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer	$ 27,918	$ 25,354
Tier 1 leverage for capital adequacy purposes, ratio, without capital conservation buffer	4.00%	4.00%
Tier 1 leverage for capital adequacy purposes, amount	$ 27,918	$ 25,354
Tier 1 leverage for capital adequacy purposes, ratio	4.00%	4.00%
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount	$ 34,898	$ 31,693
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio	5.00%	5.00%
Common equity Tier 1, actual, amount	$ 67,149	$ 61,941
Common equity Tier 1, actual ratio	10.57%	10.94%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer	$ 28,576	$ 25,477
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	$ 40,482	$ 32,554
Common equity Tier 1 for capital adequacy purposes, ratio	6.375%	5.75%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount	$ 41,276	$ 36,801
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	$ 45,314	$ 45,684
Total risk-based capital, actual, ratio	10.19%	11.28%
Total risk-based capital for capital adequacy purposes, amount, without capital conservation buffer	$ 35,583	$ 32,413
Capital Required For Capital Adequacy Excluding Capital Conservation Buffer	$ 35,583	$ 32,413
Total risk-based capital for capital adequacy purposes, ratio, without capital conservation buffer	8.00%	8.00%
Total risk-based capital for capital adequacy purposes, amount	$ 43,923	$ 37,477
Total risk-based capital for capital adequacy purposes, ratio	9.875%	9.25%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 44,479	$ 40,516
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	$ 39,692	$ 40,615
Tier 1 risk-based capital, actual, ratio	8.92%	10.02%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer	$ 26,688	$ 24,310
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	$ 35,027	$ 29,374
Tier 1 risk-based capital for capital adequacy purposes, ratio	7.875%	7.25%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 35,583	$ 32,413
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio	8.00%	8.00%
Tier 1 leverage, actual, amount	$ 39,692	$ 40,615
Tier 1 leverage, actual, ratio	8.20%	8.94%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer	$ 19,365	$ 18,177
Tier 1 leverage for capital adequacy purposes, ratio, without capital conservation buffer	4.00%	4.00%
Tier 1 leverage for capital adequacy purposes, amount	$ 19,365	$ 18,177
Tier 1 leverage for capital adequacy purposes, ratio	4.00%	4.00%
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount	$ 24,207	$ 22,721
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio	5.00%	5.00%
Common equity Tier 1, actual, amount	$ 39,692	$ 40,615
Common equity Tier 1, actual ratio	8.92%	10.02%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer	$ 20,016	$ 18,232
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	$ 28,356	$ 23,297
Common equity Tier 1 for capital adequacy purposes, ratio	6.375%	5.75%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount	$ 28,912	$ 26,335
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, ratio	6.50%	6.50%
SPRINGFIELD BANCSHARES, INC
Total risk-based capital, actual, amount	$ 54,108
Total risk-based capital, actual, ratio	11.64%
Total risk-based capital for capital adequacy purposes, amount, without capital conservation buffer	$ 37,196
Capital Required For Capital Adequacy Excluding Capital Conservation Buffer	$ 37,196
Total risk-based capital for capital adequacy purposes, ratio, without capital conservation buffer	8.00%
Total risk-based capital for capital adequacy purposes, amount	$ 45,914
Total risk-based capital for capital adequacy purposes, ratio	9.875%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 46,495
Total risk-based capital to be well capitalized under prompt corrective action provisions, ratio	10.00%
Tier 1 risk-based capital, actual, amount	$ 48,870
Tier 1 risk-based capital, actual, ratio	10.51%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer	$ 27,897
Tier 1 risk-based capital for capital adequacy purposes, ratio, without capital conservation buffer	6.00%
Tier 1 risk-based capital for capital adequacy purposes, amount	$ 36,615
Tier 1 risk-based capital for capital adequacy purposes, ratio	7.875%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	$ 37,196
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio	8.00%
Tier 1 leverage, actual, amount	$ 48,870
Tier 1 leverage, actual, ratio	9.31%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer	$ 20,988
Tier 1 leverage for capital adequacy purposes, ratio, without capital conservation buffer	4.00%
Tier 1 leverage for capital adequacy purposes, amount	$ 20,988
Tier 1 leverage for capital adequacy purposes, ratio	4.00%
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount	$ 26,235
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio	5.00%
Common equity Tier 1, actual, amount	$ 48,870
Common equity Tier 1, actual ratio	10.51%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer	$ 20,923
Common equity Tier 1 for capital adequacy purposes, ratio, without capital conservation buffer	4.50%
Common equity Tier 1 for capital adequacy purposes, amount	$ 29,640
Common equity Tier 1 for capital adequacy purposes, ratio	6.375%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount	$ 30,222
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, ratio	6.50%