Schedule of Recorded Investment in Past Due Loans by Class (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Mortgage loans held for sale	$ 75,322		$ 75,322		$ 40,828
Loans held for investment	5,028,624		5,028,624		4,856,615
Total loans	5,103,946		5,103,946		4,897,443
Interest Income on Non-Accrual Loans if Accrued	875	$ 1,061	1,613	$ 2,182
Commercial real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	8,037		8,037		6,632
Current Loans	1,669,445		1,669,445		1,605,421
Non-accrual Loans	26,591		26,591		27,369
Loans held for investment	1,704,073		1,704,073		1,639,422
Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,507		1,507		1,222
Current Loans	202,620		202,620		210,969
Non-accrual Loans	7,762		7,762		8,252
Loans held for investment	211,889		211,889		220,443
Residential construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	417		417		475
Current Loans	100,274		100,274		95,833
Non-accrual Loans	332		332		272
Loans held for investment	101,023		101,023		96,580
Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		100
Current Loans	86,874		86,874		98,582
Non-accrual Loans	3,442		3,442		2,564
Loans held for investment	90,316		90,316		101,246
Total construction loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,924		1,924		1,797
Current Loans	389,768		389,768		405,384
Non-accrual Loans	11,536		11,536		11,088
Loans held for investment	403,228		403,228		418,269
Residential real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	6,016		6,016		9,376
Current Loans	990,453		990,453		987,735
Non-accrual Loans	2,569		2,569		2,792
Loans held for investment	999,038		999,038		999,903
Agricultural real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,136		1,136		1,860
Current Loans	150,586		150,586		158,957
Non-accrual Loans	6,784		6,784		6,842
Loans held for investment	158,506		158,506		167,659
Total real estate loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	17,113		17,113		19,665
Current Loans	3,200,252		3,200,252		3,157,497
Non-accrual Loans	47,480		47,480		48,091
Loans held for investment	3,264,845		3,264,845		3,225,253
Indirect consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	3,915		3,915		3,723
Current Loans	585,200		585,200		548,757
Non-accrual Loans	364		364		383
Loans held for investment	589,479		589,479		552,863
Other consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	935		935		1,160
Current Loans	143,241		143,241		142,432
Non-accrual Loans	743		743		549
Loans held for investment	144,919		144,919		144,141
Credit card consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,030		1,030		968
Current Loans	63,684		63,684		64,484
Non-accrual Loans	14		14		15
Loans held for investment	64,728		64,728		65,467
Total consumer loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	5,880		5,880		5,851
Current Loans	792,125		792,125		755,673
Non-accrual Loans	1,121		1,121		947
Loans held for investment	799,126		799,126		762,471
Total loans	799,126		799,126		762,471
Commercial
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	9,287		9,287		4,800
Current Loans	788,210		788,210		722,575
Non-accrual Loans	21,622		21,622		12,698
Loans held for investment	819,119		819,119		740,073
Total loans	819,119		819,119		740,073
Agricultural
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	740		740		1,125
Current Loans	141,264		141,264		123,288
Non-accrual Loans	625		625		446
Loans held for investment	142,629		142,629		124,859
Other, including overdrafts
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	311		311		0
Current Loans	2,594		2,594		3,959
Non-accrual Loans	0		0		0
Loans held for investment	2,905		2,905		3,959
Loans held for investment
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	33,331		33,331		31,441
Current Loans	4,924,445		4,924,445		4,762,992
Non-accrual Loans	70,848		70,848		62,182
Loans held for investment	5,028,624		5,028,624		4,856,615
Mortgage loans originated for sale
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		0
Current Loans	75,322		75,322		40,828
Non-accrual Loans	0		0		0
Total loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	33,331		33,331		31,441
Current Loans	4,999,767		4,999,767		4,803,820
Non-accrual Loans	70,848		70,848		62,182
Total loans	5,103,946		5,103,946		4,897,443
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	5,123		5,123		4,692
Financing Receivables, 30 to 59 Days Past Due [Member] | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,075		1,075		839
Financing Receivables, 30 to 59 Days Past Due [Member] | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	417		417		0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		100
Financing Receivables, 30 to 59 Days Past Due [Member] | Total construction loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,492		1,492		939
Financing Receivables, 30 to 59 Days Past Due [Member] | Residential real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	3,563		3,563		6,969
Financing Receivables, 30 to 59 Days Past Due [Member] | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	875		875		1,624
Financing Receivables, 30 to 59 Days Past Due [Member] | Total real estate loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	11,053		11,053		14,224
Financing Receivables, 30 to 59 Days Past Due [Member] | Indirect consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	3,382		3,382		3,235
Financing Receivables, 30 to 59 Days Past Due [Member] | Other consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	785		785		988
Financing Receivables, 30 to 59 Days Past Due [Member] | Credit card consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	415		415		369
Financing Receivables, 30 to 59 Days Past Due [Member] | Total consumer loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	4,582		4,582		4,592
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	8,285		8,285		3,659
Financing Receivables, 30 to 59 Days Past Due [Member] | Agricultural
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	700		700		1,125
Financing Receivables, 30 to 59 Days Past Due [Member] | Other, including overdrafts
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		0
Financing Receivables, 30 to 59 Days Past Due [Member] | Loans held for investment
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	24,620		24,620		23,600
Financing Receivables, 30 to 59 Days Past Due [Member] | Mortgage loans originated for sale
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		0
Financing Receivables, 30 to 59 Days Past Due [Member] | Total loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	24,620		24,620		23,600
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	2,803		2,803		1,609
Financing Receivables, 60 to 89 Days Past Due [Member] | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	276		276		383
Financing Receivables, 60 to 89 Days Past Due [Member] | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		475
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		0
Financing Receivables, 60 to 89 Days Past Due [Member] | Total construction loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	276		276		858
Financing Receivables, 60 to 89 Days Past Due [Member] | Residential real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,524		1,524		645
Financing Receivables, 60 to 89 Days Past Due [Member] | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	261		261		236
Financing Receivables, 60 to 89 Days Past Due [Member] | Total real estate loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	4,864		4,864		3,348
Financing Receivables, 60 to 89 Days Past Due [Member] | Indirect consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	507		507		482
Financing Receivables, 60 to 89 Days Past Due [Member] | Other consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	121		121		140
Financing Receivables, 60 to 89 Days Past Due [Member] | Credit card consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	224		224		284
Financing Receivables, 60 to 89 Days Past Due [Member] | Total consumer loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	852		852		906
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	812		812		994
Financing Receivables, 60 to 89 Days Past Due [Member] | Agricultural
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	30		30		0
Financing Receivables, 60 to 89 Days Past Due [Member] | Other, including overdrafts
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		0
Financing Receivables, 60 to 89 Days Past Due [Member] | Loans held for investment
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	6,558		6,558		5,248
Financing Receivables, 60 to 89 Days Past Due [Member] | Mortgage loans originated for sale
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		0
Financing Receivables, 60 to 89 Days Past Due [Member] | Total loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	6,558		6,558		5,248
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	111		111		331
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	156		156		0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Residential construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Total construction loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	156		156		0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Residential real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	929		929		1,762
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Agricultural real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Total real estate loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,196		1,196		2,093
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Indirect consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	26		26		6
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Other consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	29		29		32
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Credit card consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	391		391		315
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Total consumer loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	446		446		353
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	190		190		147
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Agricultural
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	10		10		0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Other, including overdrafts
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	311		311		0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Loans held for investment
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	2,153		2,153		2,593
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Mortgage loans originated for sale
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Total loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	$ 2,153		$ 2,153		$ 2,593