Note 3 - Investment Securities (Details) - Amortized Cost and Fair Value of Investment Securities (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Securities held to maturity:
Securities held to maturity amortized cost	$ 105,201,749	$ 72,079,385
Securities held to maturity gross unrealized gains	152,017	997,969
Securities held to maturity gross unrealized losses	(5,853,172)	(71,648)
Securities held to maturity fair value	99,500,594	73,005,706
Securities available for sale:
Securities available for sale amortized cost	613,263,964	522,547,519
Securities available for sale gross unrealized gains	3,675,154	7,985,963
Securities available for sale gross unrealized losses	(18,673,718)	(373,496)
Securities available for sale fair value	598,265,400	530,159,986
US States and Political Subdivisions Debt Securities [Member]
Securities held to maturity:
Securities held to maturity amortized cost	104,551,749	71,429,385
Securities held to maturity gross unrealized gains	152,017	997,969
Securities held to maturity gross unrealized losses	(5,853,172)	(71,648)
Securities held to maturity fair value	98,850,594	72,355,706
Securities available for sale:
Securities available for sale amortized cost	36,478,946	24,508,015
Securities available for sale gross unrealized gains	1,102,715	1,696,555
Securities available for sale gross unrealized losses	(752,811)	(18,834)
Securities available for sale fair value	36,828,850	26,185,736
Equity Securities, Other [Member]
Securities held to maturity:
Securities held to maturity amortized cost	650,000	650,000
Securities held to maturity gross unrealized gains	0	0
Securities held to maturity gross unrealized losses	0	0
Securities held to maturity fair value	650,000	650,000
Securities available for sale:
Securities available for sale amortized cost	1,362,730	1,347,113
Securities available for sale gross unrealized gains	396,393	300,732
Securities available for sale gross unrealized losses	(218)	(23,469)
Securities available for sale fair value	1,758,905	1,624,376
US Government-sponsored Enterprises Debt Securities [Member]
Securities available for sale:
Securities available for sale amortized cost	395,513,928	336,570,995
Securities available for sale gross unrealized gains	238,359	2,198,655
Securities available for sale gross unrealized losses	(14,836,396)	(160,279)
Securities available for sale fair value	380,915,891	338,609,371
Residential Mortgage Backed Securities [Member]
Securities available for sale:
Securities available for sale amortized cost	179,822,160	160,035,196
Securities available for sale gross unrealized gains	1,807,687	3,736,821
Securities available for sale gross unrealized losses	(3,084,293)	(170,914)
Securities available for sale fair value	178,545,554	163,601,103
Trust preferred securities [Member]
Securities available for sale:
Securities available for sale amortized cost	86,200	86,200
Securities available for sale gross unrealized gains	130,000	53,200
Securities available for sale gross unrealized losses	0	0
Securities available for sale fair value	$ 216,200	$ 139,400