Schedule of Recorded Investment in Past Due Loans by Class (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Loans held for investment	$ 4,326,367		$ 4,303,992
Mortgage loans held for sale	38,471		40,861
Total loans	4,364,838	4,224,559	4,344,853
Interest Income on Non-Accrual Loans if Accrued	1,121	1,352
Commercial real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	12,692		5,924
60 to 89 Days Past Due	142		2,472
Greater than 90 Days Past Due	231		22
Total Loans 30 or More Days Past Due	13,065		8,418
Current Loans	1,395,474		1,391,823
Non-accrual Loans	44,428		48,933
Loans held for investment	1,452,967		1,449,174
Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	249		1,062
60 to 89 Days Past Due	0		468
Greater than 90 Days Past Due	38		38
Total Loans 30 or More Days Past Due	287		1,568
Current Loans	184,664		188,074
Non-accrual Loans	12,631		16,269
Loans held for investment	197,582		205,911
Residential construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	403		933
60 to 89 Days Past Due	0		250
Greater than 90 Days Past Due	0		0
Total Loans 30 or More Days Past Due	403		1,183
Current Loans	79,932		73,933
Non-accrual Loans	1,076		1,372
Loans held for investment	81,411		76,488
Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	8,389		584
60 to 89 Days Past Due	0		0
Greater than 90 Days Past Due	0		0
Total Loans 30 or More Days Past Due	8,389		584
Current Loans	66,747		68,427
Non-accrual Loans	220		225
Loans held for investment	75,356		69,236
Total construction loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	9,041		2,579
60 to 89 Days Past Due	0		718
Greater than 90 Days Past Due	38		38
Total Loans 30 or More Days Past Due	9,079		3,335
Current Loans	331,343		330,434
Non-accrual Loans	13,927		17,866
Loans held for investment	354,349		351,635
Residential real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	2,722		3,630
60 to 89 Days Past Due	449		206
Greater than 90 Days Past Due	628		1,162
Total Loans 30 or More Days Past Due	3,799		4,998
Current Loans	858,698		856,800
Non-accrual Loans	6,339		6,114
Loans held for investment	868,836		867,912
Agricultural real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	2,221		328
60 to 89 Days Past Due	4,903		646
Greater than 90 Days Past Due	0		0
Total Loans 30 or More Days Past Due	7,124		974
Current Loans	144,692		163,986
Non-accrual Loans	8,754		8,574
Loans held for investment	160,570		173,534
Total real estate loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	26,676		12,461
60 to 89 Days Past Due	5,494		4,042
Greater than 90 Days Past Due	897		1,222
Total Loans 30 or More Days Past Due	33,067		17,725
Current Loans	2,730,207		2,743,043
Non-accrual Loans	73,448		81,487
Loans held for investment	2,836,722		2,842,255
Indirect consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	2,193		3,303
60 to 89 Days Past Due	302		430
Greater than 90 Days Past Due	10		9
Total Loans 30 or More Days Past Due	2,505		3,742
Current Loans	478,631		471,906
Non-accrual Loans	346		364
Loans held for investment	481,482		476,012
Other consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	758		925
60 to 89 Days Past Due	73		130
Greater than 90 Days Past Due	25		1
Total Loans 30 or More Days Past Due	856		1,056
Current Loans	129,182		131,508
Non-accrual Loans	576		475
Loans held for investment	130,614		133,039
Credit card consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	183		364
60 to 89 Days Past Due	244		187
Greater than 90 Days Past Due	363		515
Total Loans 30 or More Days Past Due	790		1,066
Current Loans	57,502		61,451
Non-accrual Loans	18		19
Loans held for investment	58,310		62,536
Total consumer loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	3,134		4,592
60 to 89 Days Past Due	619		747
Greater than 90 Days Past Due	398		525
Total Loans 30 or More Days Past Due	4,151		5,864
Current Loans	665,315		664,865
Non-accrual Loans	940		858
Loans held for investment	670,406		671,587
Commercial
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	3,544		2,791
60 to 89 Days Past Due	679		1,186
Greater than 90 Days Past Due	303		563
Total Loans 30 or More Days Past Due	4,526		4,540
Current Loans	689,319		660,035
Non-accrual Loans	13,392		11,969
Loans held for investment	707,237		676,544
Agricultural
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	770		453
60 to 89 Days Past Due	118		672
Greater than 90 Days Past Due	103		0
Total Loans 30 or More Days Past Due	991		1,125
Current Loans	107,051		110,622
Non-accrual Loans	334		125
Loans held for investment	108,376		111,872
Other, including overdrafts
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	0		0
60 to 89 Days Past Due	0		0
Greater than 90 Days Past Due	0		0
Total Loans 30 or More Days Past Due	0		0
Current Loans	3,626		1,734
Non-accrual Loans	0		0
Loans held for investment	3,626		1,734
Loans held for investment
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	34,124		20,297
60 to 89 Days Past Due	6,910		6,647
Greater than 90 Days Past Due	1,701		2,310
Total Loans 30 or More Days Past Due	42,735		29,254
Current Loans	4,195,518		4,180,299
Non-accrual Loans	88,114		94,439
Loans held for investment	4,326,367		4,303,992
Mortgage loans originated for sale
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	0		0
60 to 89 Days Past Due	0		0
Greater than 90 Days Past Due	0		0
Total Loans 30 or More Days Past Due	0		0
Current Loans	38,471		40,861
Non-accrual Loans	0		0
Total loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	34,124		20,297
60 to 89 Days Past Due	6,910		6,647
Greater than 90 Days Past Due	1,701		2,310
Total Loans 30 or More Days Past Due	42,735		29,254
Current Loans	4,233,989		4,221,160
Non-accrual Loans	88,114		94,439
Total loans	$ 4,364,838		$ 4,344,853