Schedule of Loans by Class (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 4,449,699	$ 4,303,992
Mortgage loans held for sale	56,663	40,861
Total loans	4,506,362	4,344,853	4,297,364
Commercial real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	1,464,947	1,449,174
Land acquisition & development construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	192,289	205,911
Residential construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	82,121	76,488
Commercial construction real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	86,599	69,236
Total construction loans
Loans and Leases Receivable [Line Items]
Loans held for investment	361,009	351,635
Residential real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	894,502	867,912
Agricultural real estate
Loans and Leases Receivable [Line Items]
Loans held for investment	162,428	173,534
Total real estate loans
Loans and Leases Receivable [Line Items]
Loans held for investment	2,882,886	2,842,255
Indirect consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	512,063	476,012
Other consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	133,604	133,039
Credit card consumer
Loans and Leases Receivable [Line Items]
Loans held for investment	61,368	62,536
Total consumer loans
Loans and Leases Receivable [Line Items]
Loans held for investment	707,035	671,587
Commercial
Loans and Leases Receivable [Line Items]
Loans held for investment	727,482	676,544
Agricultural
Loans and Leases Receivable [Line Items]
Loans held for investment	130,280	111,872
Other, including overdrafts
Loans and Leases Receivable [Line Items]
Loans held for investment	$ 2,016	$ 1,734