Schedule of Recorded Investment in Past Due Loans by Class (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Mortgage loans held for sale	$ 62,938		$ 62,938		$ 40,861
Loans held for investment	4,791,444		4,791,444		4,303,992
Total loans	4,854,382	4,332,092	4,854,382	4,332,092	4,344,853
Interest Income on Non-Accrual Loans if Accrued	992	1,216	3,176	3,877
Commercial real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	4,290		4,290		5,924
60 to 89 Days Past Due	3,173		3,173		2,472
Greater than 90 Days Past Due	199		199		22
Total Loans 30 or More Days Past Due	7,662		7,662		8,418
Current Loans	1,643,243		1,643,243		1,391,823
Non-accrual Loans	35,604		35,604		48,933
Loans held for investment	1,686,509		1,686,509		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	4,674		4,674		1,062
60 to 89 Days Past Due	941		941		468
Greater than 90 Days Past Due	0		0		38
Total Loans 30 or More Days Past Due	5,615		5,615		1,568
Current Loans	178,608		178,608		188,074
Non-accrual Loans	9,915		9,915		16,269
Loans held for investment	194,138		194,138		205,911
Residential construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	1,798		1,798		933
60 to 89 Days Past Due	311		311		250
Greater than 90 Days Past Due	0		0		0
Total Loans 30 or More Days Past Due	2,109		2,109		1,183
Current Loans	85,832		85,832		73,933
Non-accrual Loans	238		238		1,372
Loans held for investment	88,179		88,179		76,488
Commercial construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	0		0		584
60 to 89 Days Past Due	0		0		0
Greater than 90 Days Past Due	0		0		0
Total Loans 30 or More Days Past Due	0		0		584
Current Loans	82,534		82,534		68,427
Non-accrual Loans	2,569		2,569		225
Loans held for investment	85,103		85,103		69,236
Total construction loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	6,472		6,472		2,579
60 to 89 Days Past Due	1,252		1,252		718
Greater than 90 Days Past Due	0		0		38
Total Loans 30 or More Days Past Due	7,724		7,724		3,335
Current Loans	346,974		346,974		330,434
Non-accrual Loans	12,722		12,722		17,866
Loans held for investment	367,420		367,420		351,635
Residential real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	5,054		5,054		3,630
60 to 89 Days Past Due	542		542		206
Greater than 90 Days Past Due	766		766		1,162
Total Loans 30 or More Days Past Due	6,362		6,362		4,998
Current Loans	948,412		948,412		856,800
Non-accrual Loans	2,508		2,508		6,114
Loans held for investment	957,282		957,282		867,912
Agricultural real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	909		909		328
60 to 89 Days Past Due	154		154		646
Greater than 90 Days Past Due	0		0		0
Total Loans 30 or More Days Past Due	1,063		1,063		974
Current Loans	151,028		151,028		163,986
Non-accrual Loans	6,849		6,849		8,574
Loans held for investment	158,940		158,940		173,534
Total real estate loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	16,725		16,725		12,461
60 to 89 Days Past Due	5,121		5,121		4,042
Greater than 90 Days Past Due	965		965		1,222
Total Loans 30 or More Days Past Due	22,811		22,811		17,725
Current Loans	3,089,657		3,089,657		2,743,043
Non-accrual Loans	57,683		57,683		81,487
Loans held for investment	3,170,151		3,170,151		2,842,255
Indirect consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	2,728		2,728		3,303
60 to 89 Days Past Due	278		278		430
Greater than 90 Days Past Due	2		2		9
Total Loans 30 or More Days Past Due	3,008		3,008		3,742
Current Loans	534,344		534,344		471,906
Non-accrual Loans	413		413		364
Loans held for investment	537,765		537,765		476,012
Other consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	976		976		925
60 to 89 Days Past Due	154		154		130
Greater than 90 Days Past Due	39		39		1
Total Loans 30 or More Days Past Due	1,169		1,169		1,056
Current Loans	143,320		143,320		131,508
Non-accrual Loans	587		587		475
Loans held for investment	145,076		145,076		133,039
Credit card consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	340		340		364
60 to 89 Days Past Due	261		261		187
Greater than 90 Days Past Due	235		235		515
Total Loans 30 or More Days Past Due	836		836		1,066
Current Loans	61,789		61,789		61,451
Non-accrual Loans	16		16		19
Loans held for investment	62,641		62,641		62,536
Total consumer loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	4,044		4,044		4,592
60 to 89 Days Past Due	693		693		747
Greater than 90 Days Past Due	276		276		525
Total Loans 30 or More Days Past Due	5,013		5,013		5,864
Current Loans	739,453		739,453		664,865
Non-accrual Loans	1,016		1,016		858
Loans held for investment	745,482		745,482		671,587
Commercial
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	10,716		10,716		2,791
60 to 89 Days Past Due	1,077		1,077		1,186
Greater than 90 Days Past Due	113		113		563
Total Loans 30 or More Days Past Due	11,906		11,906		4,540
Current Loans	712,261		712,261		660,035
Non-accrual Loans	12,741		12,741		11,969
Loans held for investment	736,908		736,908		676,544
Agricultural
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	23		23		453
60 to 89 Days Past Due	0		0		672
Greater than 90 Days Past Due	0		0		0
Total Loans 30 or More Days Past Due	23		23		1,125
Current Loans	136,089		136,089		110,622
Non-accrual Loans	475		475		125
Loans held for investment	136,587		136,587		111,872
Other, including overdrafts
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	0		0		0
60 to 89 Days Past Due	0		0		0
Greater than 90 Days Past Due	0		0		0
Total Loans 30 or More Days Past Due	0		0		0
Current Loans	2,316		2,316		1,734
Non-accrual Loans	0		0		0
Loans held for investment	2,316		2,316		1,734
Loans held for investment
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	31,508		31,508		20,297
60 to 89 Days Past Due	6,891		6,891		6,647
Greater than 90 Days Past Due	1,354		1,354		2,310
Total Loans 30 or More Days Past Due	39,753		39,753		29,254
Current Loans	4,679,776		4,679,776		4,180,299
Non-accrual Loans	71,915		71,915		94,439
Loans held for investment	4,791,444		4,791,444		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		0
60 to 89 Days Past Due	0		0		0
Greater than 90 Days Past Due	0		0		0
Total Loans 30 or More Days Past Due	0		0		0
Current Loans	62,938		62,938		40,861
Non-accrual Loans	0		0		0
Total loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	31,508		31,508		20,297
60 to 89 Days Past Due	6,891		6,891		6,647
Greater than 90 Days Past Due	1,354		1,354		2,310
Total Loans 30 or More Days Past Due	39,753		39,753		29,254
Current Loans	4,742,714		4,742,714		4,221,160
Non-accrual Loans	71,915		71,915		94,439
Total loans	$ 4,854,382		$ 4,854,382		$ 4,344,853