Note 2 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
General Obligation Bonds [Member]
Note 2 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	81	77
Amortized cost	$ 63,805,626	$ 67,868,415
Fair value	64,689,601	68,768,171
Average exposure per issuer (fair value)	$ 798,637	$ 893,093
General Obligation Bonds [Member] | IOWA
Note 2 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	15	14
Amortized cost	$ 20,225,477	$ 20,156,969
Fair value	20,363,737	20,446,655
Average exposure per issuer (fair value)	$ 1,357,582	$ 1,460,475
General Obligation Bonds [Member] | ILLINOIS
Note 2 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	10	10
Amortized cost	$ 11,851,955	$ 22,447,799
Fair value	12,191,238	22,784,638
Average exposure per issuer (fair value)	$ 1,219,124	$ 2,278,464
General Obligation Bonds [Member] | MISSOURI
Note 2 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	12	11
Amortized cost	$ 7,930,365	$ 8,424,928
Fair value	7,968,565	8,426,047
Average exposure per issuer (fair value)	$ 664,047	$ 766,004
General Obligation Bonds [Member] | NORTH DAKOTA
Note 2 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	3
Amortized cost	$ 6,675,000
Fair value	6,767,961
Average exposure per issuer (fair value)	$ 2,255,987
General Obligation Bonds [Member] | Other States [Member]
Note 2 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	41	42
Amortized cost	$ 17,122,829	$ 16,838,719
Fair value	17,398,100	17,110,831
Average exposure per issuer (fair value)	$ 424,344	$ 407,401
Revenue Bonds [Member]
Note 2 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	87	64
Amortized cost	$ 200,600,147	$ 160,369,899
Fair value	201,382,892	161,695,606
Average exposure per issuer (fair value)	$ 2,314,746	$ 2,526,494
Revenue Bonds [Member] | IOWA
Note 2 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	26	20
Amortized cost	$ 71,365,816	$ 59,417,246
Fair value	71,890,381	60,402,941
Average exposure per issuer (fair value)	$ 2,765,015	$ 3,020,147
Revenue Bonds [Member] | MISSOURI
Note 2 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	40	30
Amortized cost	$ 75,016,470	$ 62,358,276
Fair value	75,197,907	62,584,516
Average exposure per issuer (fair value)	$ 1,879,948	$ 2,086,151
Revenue Bonds [Member] | Other States [Member]
Note 2 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	4	4
Amortized cost	$ 7,764,820	$ 8,295,311
Fair value	7,898,909	8,449,900
Average exposure per issuer (fair value)	$ 1,974,727	$ 2,112,475
Revenue Bonds [Member] | INDIANA
Note 2 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	14	8
Amortized cost	$ 34,701,481	$ 17,991,200
Fair value	34,707,516	17,925,721
Average exposure per issuer (fair value)	$ 2,479,108	$ 2,240,715
Revenue Bonds [Member] | KANSAS
Note 2 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	3	2
Amortized cost	$ 11,751,560	$ 12,307,866
Fair value	11,688,179	12,332,528
Average exposure per issuer (fair value)	$ 3,896,060	$ 6,166,264