Note 8. Short-Term Borrowings (Details) - Overnight Repurchase Agreements - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Repurchase Agreements with Customers [Member]
Note 8. Short-Term Borrowings (Details) - Overnight Repurchase Agreements [Line Items]
Average daily balance during the period	$ 121,186,231	$ 128,818,152
Average daily interest rate during the period	0.11%	0.12%
Maximum month-end balance during the period	$ 159,407,193	$ 147,623,624
Weighted average rate as of end of period	0.11%	0.11%
Federal Funds Purchased [Member]
Note 8. Short-Term Borrowings (Details) - Overnight Repurchase Agreements [Line Items]
Average daily balance during the period	$ 32,826,489	$ 33,876,815
Average daily interest rate during the period	0.41%	0.40%
Maximum month-end balance during the period	$ 126,220,000	$ 131,100,000
Weighted average rate as of end of period	0.57%	0.51%