Note 3 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
General Obligation Bonds [Member]
Note 3 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	82	77
Amortized cost	$ 66,683,832	$ 67,868,415
Fair value	67,778,032	68,768,171
Average exposure per issuer (fair value)	$ 826,561	$ 893,093
General Obligation Bonds [Member] | IOWA
Note 3 - 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	$ 19,974,939	$ 20,156,969
Fair value	20,247,108	20,446,655
Average exposure per issuer (fair value)	$ 1,349,807	$ 1,460,475
General Obligation Bonds [Member] | ILLINOIS
Note 3 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	9	10
Amortized cost	$ 10,928,700	$ 22,447,799
Fair value	11,264,348	22,784,638
Average exposure per issuer (fair value)	$ 1,251,594	$ 2,278,464
General Obligation Bonds [Member] | NORTH DAKOTA
Note 3 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	5
Amortized cost	$ 10,890,000
Fair value	11,050,235
Average exposure per issuer (fair value)	$ 2,210,047
General Obligation Bonds [Member] | MISSOURI
Note 3 - 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	$ 7,924,800	$ 8,424,928
Fair value	7,986,856	8,426,047
Average exposure per issuer (fair value)	$ 665,571	$ 766,004
General Obligation Bonds [Member] | Other States [Member]
Note 3 - 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	$ 16,965,393	$ 16,838,719
Fair value	17,229,485	17,110,831
Average exposure per issuer (fair value)	$ 420,231	$ 407,401
Revenue Bonds [Member]
Note 3 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	92	64
Amortized cost	$ 212,705,308	$ 160,369,899
Fair value	214,441,841	161,695,606
Average exposure per issuer (fair value)	$ 2,330,890	$ 2,526,494
Revenue Bonds [Member] | IOWA
Note 3 - 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	$ 70,773,660	$ 59,417,246
Fair value	71,659,410	60,402,941
Average exposure per issuer (fair value)	$ 2,756,131	$ 3,020,147
Revenue Bonds [Member] | MISSOURI
Note 3 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	41	30
Amortized cost	$ 78,593,590	$ 62,358,276
Fair value	79,015,378	62,584,516
Average exposure per issuer (fair value)	$ 1,927,204	$ 2,086,151
Revenue Bonds [Member] | Other States [Member]
Note 3 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	5	4
Amortized cost	$ 11,570,998	$ 8,295,311
Fair value	11,735,678	8,449,900
Average exposure per issuer (fair value)	$ 2,347,136	$ 2,112,475
Revenue Bonds [Member] | INDIANA
Note 3 - Investment Securities (Details) - Amortized Cost and Fair Values of General Obligation Bonds by Issuer's State [Line Items]
Number of issuers	17	8
Amortized cost	$ 40,018,381	$ 17,991,200
Fair value	40,210,320	17,925,721
Average exposure per issuer (fair value)	$ 2,365,313	$ 2,240,715
Revenue Bonds [Member] | KANSAS
Note 3 - 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	$ 11,748,679	$ 12,307,866
Fair value	11,821,055	12,332,528
Average exposure per issuer (fair value)	$ 3,940,352	$ 6,166,264