Note 16 - Regulatory Capital Requirements and Restrictions on Dividends - Capital Requirements (Details) - USD ($)		Dec. 31, 2018	Dec. 31, 2017
Total risk-based capital, actual, amount		$ 460,416	$ 383,282
Total risk-based capital, actual, ratio		10.69%	11.15%
Total risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 344,551	$ 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		$ 425,305	$ 318,073
Total risk-based capital for capital adequacy purposes, ratio	[1]	9.875%	9.25%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	[1]	$ 430,689	$ 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		$ 420,569	$ 348,530
Tier 1 risk-based capital, actual, ratio		9.77%	10.14%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 258,413	$ 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		$ 339,168	$ 249,300
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	7.875%	7.25%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	[1]	$ 344,551	$ 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		$ 420,569	$ 348,530
Tier 1 leverage, actual, ratio		8.87%	8.98%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer		$ 189,858	$ 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		$ 189,858	$ 155,256
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	[1]	$ 237,322	$ 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		$ 382,899	$ 313,012
Common equity Tier 1, actual ratio		8.89%	9.10%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer		$ 193,810	$ 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		$ 274,564	$ 197,721
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	6.375%	5.75%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount	[1]	$ 279,948	$ 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		$ 162,009	$ 160,112
Total risk-based capital, actual, ratio		11.38%	12.35%
Total risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 113,900	$ 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		$ 140,596	$ 119,916
Total risk-based capital for capital adequacy purposes, ratio	[1]	9.875%	9.25%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	[1]	$ 142,376	$ 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		$ 148,529	$ 147,472
Tier 1 risk-based capital, actual, ratio		10.43%	11.38%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 85,425	$ 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		$ 112,121	$ 93,988
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	7.875%	7.25%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	[1]	$ 113,900	$ 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		$ 148,529	$ 147,472
Tier 1 leverage, actual, ratio		9.04%	9.52%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer		$ 65,744	$ 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		$ 65,744	$ 61,985
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	[1]	$ 82,180	$ 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		$ 148,529	$ 147,472
Common equity Tier 1, actual ratio		10.43%	11.38%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer		$ 64,069	$ 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		$ 90,764	$ 74,542
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	6.375%	5.75%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount	[1]	$ 92,544	$ 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		$ 146,292	$ 138,492
Total risk-based capital, actual, ratio		11.55%	11.88%
Total risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 101,310	$ 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		$ 125,054	$ 107,846
Total risk-based capital for capital adequacy purposes, ratio	[1]	9.875%	9.25%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	[1]	$ 126,637	$ 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		$ 133,982	$ 126,601
Tier 1 risk-based capital, actual, ratio		10.58%	10.86%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 75,982	$ 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		$ 99,727	$ 84,528
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	7.875%	7.25%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	[1]	$ 101,310	$ 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		$ 133,982	$ 126,601
Tier 1 leverage, actual, ratio		9.98%	11.68%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer		$ 53,682	$ 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		$ 53,682	$ 43,348
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	[1]	$ 67,103	$ 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		$ 133,982	$ 126,601
Common equity Tier 1, actual ratio		10.58%	10.86%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer		$ 56,987	$ 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		$ 80,731	$ 67,039
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	6.375%	5.75%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount	[1]	$ 82,314	$ 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		$ 75,233	$ 66,271
Total risk-based capital, actual, ratio		11.24%	11.71%
Total risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 53,567	$ 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		$ 66,122	$ 52,370
Total risk-based capital for capital adequacy purposes, ratio	[1]	9.875%	9.25%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	[1]	$ 66,959	$ 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		$ 69,101	$ 61,941
Tier 1 risk-based capital, actual, ratio		10.32%	10.94%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 40,175	$ 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		$ 52,730	$ 41,047
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	7.875%	7.25%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	[1]	$ 53,567	$ 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		$ 69,101	$ 61,941
Tier 1 leverage, actual, ratio		9.19%	9.77%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer		$ 30,070	$ 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		$ 30,070	$ 25,354
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	[1]	$ 37,588	$ 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		$ 69,101	$ 61,941
Common equity Tier 1, actual ratio		10.32%	10.94%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer		$ 30,131	$ 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		$ 42,686	$ 32,554
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	6.375%	5.75%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount	[1]	$ 43,523	$ 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		$ 50,648	$ 45,684
Total risk-based capital, actual, ratio		10.89%	11.28%
Total risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 37,208	$ 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		$ 45,929	$ 37,477
Total risk-based capital for capital adequacy purposes, ratio	[1]	9.875%	9.25%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	[1]	$ 46,511	$ 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		$ 44,821	$ 40,615
Tier 1 risk-based capital, actual, ratio		9.64%	10.02%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 27,906	$ 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		$ 36,627	$ 29,374
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	7.875%	7.25%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	[1]	$ 37,208	$ 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		$ 44,821	$ 40,615
Tier 1 leverage, actual, ratio		8.93%	8.94%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer		$ 20,081	$ 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		$ 20,081	$ 18,177
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	[1]	$ 25,101	$ 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		$ 44,821	$ 40,615
Common equity Tier 1, actual ratio		9.64%	10.02%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer		$ 20,930	$ 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		$ 29,650	$ 23,297
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	6.375%	5.75%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount	[1]	$ 30,232	$ 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		$ 57,051
Total risk-based capital, actual, ratio		12.24%
Total risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 37,278
Total risk-based capital for capital adequacy purposes, ratio, without capital conservation buffer		8.00%
Total risk-based capital for capital adequacy purposes, amount		$ 46,016
Total risk-based capital for capital adequacy purposes, ratio	[1]	9.875%
Total risk-based capital to be well capitalized under prompt corrective action provisions, amount	[1]	$ 46,598
Total risk-based capital to be well capitalized under prompt corrective action provisions, ratio		10.00%
Tier 1 risk-based capital, actual, amount		$ 51,279
Tier 1 risk-based capital, actual, ratio		11.00%
Tier 1 risk-based capital for capital adequacy purposes, amount, without capital conservation buffer		$ 27,959
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		$ 36,696
Tier 1 risk-based capital for capital adequacy purposes, ratio	[1]	7.875%
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, amount	[1]	$ 37,278
Tier 1 risk-based capital to be well capitalized under prompt corrective action provisions, ratio		8.00%
Tier 1 leverage, actual, amount		$ 51,279
Tier 1 leverage, actual, ratio		9.39%
Tier 1 leverage for capital adequacy purposes, amount, without capital conservation buffer		$ 21,849
Tier 1 leverage for capital adequacy purposes, ratio, without capital conservation buffer		4.00%
Tier 1 leverage for capital adequacy purposes, amount		$ 21,849
Tier 1 leverage for capital adequacy purposes, ratio	[1]	4.00%
Tier 1 leverage to be well capitalized under prompt corrective action provisions, amount	[1]	$ 27,312
Tier 1 leverage to be well capitalized under prompt corrective action provisions, ratio		5.00%
Common equity Tier 1, actual, amount		$ 51,279
Common equity Tier 1, actual ratio		11.00%
Common equity Tier 1 for capital adequacy purposes, amount, without capital conservation buffer		$ 20,969
Common equity Tier 1 for capital adequacy purposes, ratio, without capital conservation buffer		4.50%
Common equity Tier 1 for capital adequacy purposes, amount		$ 29,706
Common equity Tier 1 for capital adequacy purposes, ratio	[1]	6.375%
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, amount	[1]	$ 30,289
Common equity Tier 1 to be well capitalized under prompt corrective action provisions, ratio		6.50%

[1] The minimums under Basel III increase by .625% (the capital conservation buffer) for all ratios other than Tier 1 leverage annually until 2019.