Note 5. Held to Maturity Securities (Detail) - Amortized Costs and Fair Values of Held to Maturity Securities (USD $)	Jun. 30, 2012	Dec. 31, 2011
Amortized Cost	$ 335,836,897	$ 360,566,062
Unrealized Gains	4,140,631	2,785,852
Unrealized Losses	(92,262)	(99,230)
Fair Value	339,885,266	363,252,684
US States and Political Subdivisions Debt Securities [Member]
Amortized Cost	60,146,013	63,145,630
Unrealized Gains	1,938,157	1,897,676
Unrealized Losses	(26,415)	(3,892)
Fair Value	62,057,755	65,039,414
US Government-sponsored Enterprises Debt Securities [Member]
Amortized Cost	107,000,000	261,601,680
Unrealized Gains	341,300	810,407
Unrealized Losses		(5,000)
Fair Value	107,341,300	262,407,087
Collateralized Mortgage Obligations [Member]
Amortized Cost	47,617,750	17,069,071
Unrealized Gains	807,039	25,702
Unrealized Losses	(40,460)	(81,226)
Fair Value	48,384,329	17,013,547
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Amortized Cost	121,023,134	18,699,681
Unrealized Gains	1,054,135	52,067
Unrealized Losses	(25,387)	(9,112)
Fair Value	122,051,882	18,742,636
Other Debt Obligations [Member]
Amortized Cost	50,000	50,000
Fair Value	$ 50,000	$ 50,000