Loans - Schedule of Loans by Class (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Loans and Leases Receivable
Loans held for investment	$ 4,303,992	$ 4,157,470
Mortgage loans held for sale	40,861	66,442
Total loans	4,344,853	4,223,912
Commercial real estate
Loans and Leases Receivable
Loans held for investment	1,449,174	1,497,272
Land acquisition & development construction real estate
Loans and Leases Receivable
Loans held for investment	205,911	220,196
Residential construction real estate
Loans and Leases Receivable
Loans held for investment	76,488	49,274
Commercial construction real estate
Loans and Leases Receivable
Loans held for investment	69,236	65,059
Total construction loans
Loans and Leases Receivable
Loans held for investment	351,635	334,529
Residential real estate
Loans and Leases Receivable
Loans held for investment	867,912	708,339
Loans receivable, maturity	15 years
Agricultural real estate
Loans and Leases Receivable
Loans held for investment	173,534	177,244
Total real estate loans
Loans and Leases Receivable
Loans held for investment	2,842,255	2,717,384
Indirect consumer
Loans and Leases Receivable
Loans held for investment	476,012	438,245
Other consumer
Loans and Leases Receivable
Loans held for investment	133,039	137,743
Credit card consumer
Loans and Leases Receivable
Loans held for investment	62,536	60,806
Total consumer loans
Loans and Leases Receivable
Loans held for investment	671,587	636,794
Commercial
Loans and Leases Receivable
Loans held for investment	676,544	688,753
Agricultural
Loans and Leases Receivable
Loans held for investment	111,872	113,627
Other, including overdrafts
Loans and Leases Receivable
Loans held for investment	1,734	912
Home equity line of credit
Loans and Leases Receivable
Loans held for investment	$ 272,415	$ 273,739
Loans receivable, loan to value limit	80.00%
Commercial and agricultural real estate
Loans and Leases Receivable
Loans receivable, maturity	5 years