Loans and Allowance for Loan Losses (Granite Purchased Loans) (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Financing Receivable [Line Items]
Allowance of loan losses	$ 29,314,000	$ 39,360,000	$ 93,687,000	$ 49,461,000
Purchased impaired	228,392,000	330,836,000
Purchased contractual	34,844,000	42,652,000
Loans held for investment	1,177,035,000	1,217,535,000
Unpaid principal balance	271,060,000	404,130,000
PI [Member]
Financing Receivable [Line Items]
Loans held for investment	228,392,000	332,223,000
PC [Member]
Financing Receivable [Line Items]
Loans held for investment	948,643,000	885,312,000
Granite Corp. [Member]
Financing Receivable [Line Items]
Allowance of loan losses		0
Purchased impaired	228,392,000	330,836,000
Loans held for investment	263,236,000	373,488,000
Granite Corp. [Member] | Commercial and agricultural [Member]
Financing Receivable [Line Items]
Purchased impaired	14,666,000	28,872,000
Purchased contractual	7,311,000	8,061,000
Loans held for investment	21,977,000	36,933,000
Unpaid principal balance	21,692,000	39,531,000
Granite Corp. [Member] | Real estate - construction [Member]
Financing Receivable [Line Items]
Purchased impaired	2,682,000	7,641,000
Purchased contractual	0	0
Loans held for investment	2,682,000	7,641,000
Unpaid principal balance	2,677,000	8,413,000
Granite Corp. [Member] | Real estate - mortgage, 1-4 family residential [Member]
Financing Receivable [Line Items]
Purchased impaired	39,215,000	52,894,000
Purchased contractual	27,484,000	34,590,000
Loans held for investment	66,699,000	87,484,000
Unpaid principal balance	69,200,000	93,310,000
Granite Corp. [Member] | Real estate - mortgage, commercial [Member]
Financing Receivable [Line Items]
Purchased impaired	170,467,000	239,621,000
Purchased contractual	49,000	0
Loans held for investment	170,516,000	239,621,000
Unpaid principal balance	176,347,000	261,076,000
Granite Corp. [Member] | Consumer [Member]
Financing Receivable [Line Items]
Purchased impaired	1,362,000	1,808,000
Purchased contractual	0	1,000
Loans held for investment	1,362,000	1,809,000
Unpaid principal balance	1,144,000	1,800,000
Granite Corp. [Member] | PI [Member]
Financing Receivable [Line Items]
Allowance of loan losses	5,400,000
Granite Corp. [Member] | PC [Member]
Financing Receivable [Line Items]
Allowance of loan losses	$ 500,000