Loans and Allowance for Loan Losses (Granite Purchased Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable [Line Items]
Total Loans	$ 1,543,795	$ 1,357,788
Granite Corp. [Member]
Financing Receivable [Line Items]
Purchased Impaired	87,564	122,842	$ 161,652
Purchased Contractual	18,153	25,948
Total Loans	105,717	148,790
Unpaid Principal Balance	106,466	153,774
Granite Corp. [Member] | Commercial and agricultural [Member]
Financing Receivable [Line Items]
Purchased Impaired	4,995	7,535
Purchased Contractual	238	4,288
Total Loans	5,233	11,823
Unpaid Principal Balance	4,149	10,508
Granite Corp. [Member] | Real estate - construction [Member]
Financing Receivable [Line Items]
Purchased Impaired	7,744	9,197
Purchased Contractual	0	0
Total Loans	7,744	9,197
Unpaid Principal Balance	8,579	10,463
Granite Corp. [Member] | Real estate - mortgage, 1-4 family residential [Member]
Financing Receivable [Line Items]
Purchased Impaired	13,917	17,737
Purchased Contractual	17,915	21,660
Total Loans	31,832	39,397
Unpaid Principal Balance	32,558	41,295
Granite Corp. [Member] | Real estate - mortgage, commercial [Member]
Financing Receivable [Line Items]
Purchased Impaired	59,989	87,345
Purchased Contractual	0	0
Total Loans	59,989	87,345
Unpaid Principal Balance	60,582	90,830
Granite Corp. [Member] | Consumer [Member]
Financing Receivable [Line Items]
Purchased Impaired	919	1,028
Purchased Contractual	0	0
Total Loans	919	1,028
Unpaid Principal Balance	$ 598	$ 678