Loans (Details) (USD $)											1 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Jun. 30, 2012 Commercial and agricultural [Member]	Dec. 31, 2011 Commercial and agricultural [Member]	Jun. 30, 2012 Real estate - construction [Member]	Dec. 31, 2011 Real estate - construction [Member]	Apr. 30, 2012 Real estate - mortgage, 1-4 family residential [Member]	Feb. 29, 2012 Real estate - mortgage, 1-4 family residential [Member]	Jun. 30, 2012 Real estate - mortgage, 1-4 family residential [Member]	Dec. 31, 2011 Real estate - mortgage, 1-4 family residential [Member]	Jun. 30, 2012 Real estate - mortgage, commercial [Member]	Dec. 31, 2011 Real estate - mortgage, commercial [Member]	Jun. 30, 2012 Consumer [Member]	Dec. 31, 2011 Consumer [Member]	Jun. 30, 2012 Granite Corp [Member]	Dec. 31, 2011 Granite Corp [Member]	Jun. 30, 2012 Granite Corp [Member] Commercial and agricultural [Member]	Dec. 31, 2011 Granite Corp [Member] Commercial and agricultural [Member]	Jun. 30, 2012 Granite Corp [Member] Real estate - construction [Member]	Dec. 31, 2011 Granite Corp [Member] Real estate - construction [Member]	Jun. 30, 2012 Granite Corp [Member] Real estate - mortgage, 1-4 family residential [Member]	Dec. 31, 2011 Granite Corp [Member] Real estate - mortgage, 1-4 family residential [Member]	Jun. 30, 2012 Granite Corp [Member] Real estate - mortgage, commercial [Member]	Dec. 31, 2011 Granite Corp [Member] Real estate - mortgage, commercial [Member]	Jun. 30, 2012 Granite Corp [Member] Consumer [Member]	Dec. 31, 2011 Granite Corp [Member] Consumer [Member]
Financing Receivable [Line Items]
Loans held for sale	$ 1,324,000		$ 4,529,000																$ 0	$ 0
Loans held for investment	1,281,823,000		1,217,535,000				78,367,000	95,089,000	75,576,000	92,806,000			589,972,000	453,725,000	493,721,000	531,383,000	44,187,000	44,532,000	323,748,000	373,488,000	26,560,000	36,933,000	5,671,000	7,641,000	76,523,000	87,484,000	213,750,000	239,621,000	1,244,000	1,809,000
Less: Allowance for loan losses	(38,551,000)	(39,795,000)	(39,360,000)	(59,366,000)	(68,729,000)	(93,687,000)													(3,336,000)	0
Net loans held for investment	1,243,272,000		1,178,175,000																320,412,000	373,488,000
Loans purchases											75,500,000	61,900,000
Loans purchases premium											1,400,000	2,300,000
Net deferred loan premiums (discounts)	(2,600,000)		1,800,000
Unpaid principal balance for loans serviced for others	$ 2,500,000		$ 700,000