Schedule of Recorded Investment in Past Due Loans by Class (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Mortgage loans held for sale	$ 55,686		$ 55,686		$ 40,828
Loans held for investment	5,120,794		5,120,794		4,856,615
Total loans	5,176,480		5,176,480		4,897,443
Interest Income on Non-Accrual Loans if Accrued	828	$ 992	2,331	$ 3,176
Commercial real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	7,030		7,030		6,632
Current Loans	1,720,928		1,720,928		1,605,421
Non-accrual Loans	22,839		22,839		27,369
Loans held for investment	1,750,797		1,750,797		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	11,069		11,069		1,222
Current Loans	192,819		192,819		210,969
Non-accrual Loans	9,102		9,102		8,252
Loans held for investment	212,990		212,990		220,443
Residential construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,145		1,145		475
Current Loans	111,021		111,021		95,833
Non-accrual Loans	329		329		272
Loans held for investment	112,495		112,495		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	92,792		92,792		98,582
Non-accrual Loans	983		983		2,564
Loans held for investment	93,775		93,775		101,246
Total construction loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	12,214		12,214		1,797
Current Loans	396,632		396,632		405,384
Non-accrual Loans	10,414		10,414		11,088
Loans held for investment	419,260		419,260		418,269
Residential real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	8,755		8,755		9,376
Current Loans	1,009,119		1,009,119		987,735
Non-accrual Loans	2,571		2,571		2,792
Loans held for investment	1,020,445		1,020,445		999,903
Agricultural real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	881		881		1,860
Current Loans	155,443		155,443		158,957
Non-accrual Loans	6,792		6,792		6,842
Loans held for investment	163,116		163,116		167,659
Total real estate loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	28,880		28,880		19,665
Current Loans	3,282,122		3,282,122		3,157,497
Non-accrual Loans	42,616		42,616		48,091
Loans held for investment	3,353,618		3,353,618		3,225,253
Indirect consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	4,765		4,765		3,723
Current Loans	610,641		610,641		548,757
Non-accrual Loans	736		736		383
Loans held for investment	616,142		616,142		552,863
Other consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,301		1,301		1,160
Current Loans	148,119		148,119		142,432
Non-accrual Loans	750		750		549
Loans held for investment	150,170		150,170		144,141
Credit card consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,245		1,245		968
Current Loans	64,391		64,391		64,484
Non-accrual Loans	13		13		15
Loans held for investment	65,649		65,649		65,467
Total consumer loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	7,311		7,311		5,851
Current Loans	823,151		823,151		755,673
Non-accrual Loans	1,499		1,499		947
Loans held for investment	831,961		831,961		762,471
Total loans	831,961		831,961		762,471
Commercial
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	5,240		5,240		4,800
Current Loans	751,769		751,769		722,575
Non-accrual Loans	21,639		21,639		12,698
Loans held for investment	778,648		778,648		740,073
Total loans	778,648		778,648		740,073
Agricultural
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	407		407		1,125
Current Loans	153,843		153,843		123,288
Non-accrual Loans	605		605		446
Loans held for investment	154,855		154,855		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	1,401		1,401		3,959
Non-accrual Loans	0		0		0
Loans held for investment	1,712		1,712		3,959
Loans held for investment
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	42,149		42,149		31,441
Current Loans	5,012,286		5,012,286		4,762,992
Non-accrual Loans	66,359		66,359		62,182
Loans held for investment	5,120,794		5,120,794		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	55,686		55,686		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	42,149		42,149		31,441
Current Loans	5,067,972		5,067,972		4,803,820
Non-accrual Loans	66,359		66,359		62,182
Total loans	5,176,480		5,176,480		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	5,968		5,968		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	4,495		4,495		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	1,011		1,011		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	5,506		5,506		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	5,639		5,639		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	881		881		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	17,994		17,994		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	3,991		3,991		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	1,012		1,012		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	402		402		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	5,405		5,405		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	3,440		3,440		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	281		281		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	27,120		27,120		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	27,120		27,120		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	664		664		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	6,530		6,530		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	134		134		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	6,664		6,664		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	2,355		2,355		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	0		0		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	9,683		9,683		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	683		683		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	264		264		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	325		325		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	1,272		1,272		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	717		717		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	0		0		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	11,672		11,672		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	11,672		11,672		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	398		398		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	44		44		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	44		44		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	761		761		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	1,203		1,203		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	91		91		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	25		25		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	518		518		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	634		634		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	1,083		1,083		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	126		126		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	3,357		3,357		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	$ 3,357		$ 3,357		$ 2,593