Schedule of Recorded Investment in Past Due Loans by Class (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Mortgage loans held for sale	$ 30,383		$ 30,383		$ 61,794
Loans held for investment	7,525,590		7,525,590		5,416,750
Total loans	7,555,973		7,555,973		5,478,544
Interest Income on Non-Accrual Loans if Accrued	919	$ 821	1,772	$ 1,690
Commercial real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	5,919		5,919		8,709
Current Loans	2,780,010		2,780,010		1,799,525
Non-accrual Loans	30,597		30,597		26,211
Loans held for investment	2,816,526		2,816,526		1,834,445
Land acquisition & development construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,974		1,974		1,264
Current Loans	333,247		333,247		202,223
Non-accrual Loans	4,663		4,663		5,025
Loans held for investment	339,884		339,884		208,512
Residential construction real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,632		1,632		1,195
Current Loans	217,914		217,914		146,245
Non-accrual Loans	210		210		456
Loans held for investment	219,756		219,756		147,896
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
Current Loans	117,287		117,287		124,827
Non-accrual Loans	4,318		4,318		762
Loans held for investment	121,605		121,605		125,589
Total construction loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	3,606		3,606		2,459
Current Loans	668,448		668,448		473,295
Non-accrual Loans	9,191		9,191		6,243
Loans held for investment	681,245		681,245		481,997
Residential real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	20,302		20,302		5,968
Current Loans	1,441,507		1,441,507		1,014,990
Non-accrual Loans	4,205		4,205		6,435
Loans held for investment	1,466,014		1,466,014		1,027,393
Agricultural real estate
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	3,932		3,932		628
Current Loans	156,898		156,898		165,293
Non-accrual Loans	2,345		2,345		4,327
Loans held for investment	163,175		163,175		170,248
Total real estate loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	33,759		33,759		17,764
Current Loans	5,046,863		5,046,863		3,453,103
Non-accrual Loans	46,338		46,338		43,216
Loans held for investment	5,126,960		5,126,960		3,514,083
Indirect consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	8,237		8,237		11,466
Current Loans	769,361		769,361		740,163
Non-accrual Loans	1,428		1,428		780
Loans held for investment	779,026		779,026		752,409
Other consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,634		1,634		1,724
Current Loans	173,713		173,713		146,006
Non-accrual Loans	390		390		357
Loans held for investment	175,737		175,737		148,087
Credit card consumer
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	1,330		1,330		1,404
Current Loans	74,300		74,300		68,366
Non-accrual Loans	1		1		0
Loans held for investment	75,631		75,631		69,770
Total consumer loans
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	11,201		11,201		14,594
Current Loans	1,017,374		1,017,374		954,535
Non-accrual Loans	1,819		1,819		1,137
Loans held for investment	1,030,394		1,030,394		970,266
Commercial
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	6,419		6,419		4,632
Current Loans	1,178,688		1,178,688		767,878
Non-accrual Loans	25,762		25,762		25,432
Loans held for investment	1,210,869		1,210,869		797,942
Agricultural
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	2,537		2,537		1,894
Current Loans	143,824		143,824		127,956
Non-accrual Loans	2,768		2,768		3,008
Loans held for investment	149,129		149,129		132,858
Other, including overdrafts
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	0		0		312
Current Loans	8,238		8,238		1,289
Non-accrual Loans	0		0		0
Loans held for investment	8,238		8,238		1,601
Loans held for investment
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]
Total Loans 30 or More Days Past Due	53,916		53,916		39,196
Current Loans	7,394,987		7,394,987		5,304,761
Non-accrual Loans	76,687		76,687		72,793
Loans held for investment	7,525,590		7,525,590		5,416,750
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	30,383		30,383		61,794
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	53,916		53,916		39,196
Current Loans	7,425,370		7,425,370		5,366,555
Non-accrual Loans	76,687		76,687		72,793
Total loans	7,555,973		7,555,973		5,478,544
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	4,522		4,522		7,307
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	1,880		1,880		633
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	1,124		1,124		931
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		0
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	3,004		3,004		1,564
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	14,136		14,136		3,986
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	1,371		1,371		341
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	23,033		23,033		13,198
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	6,430		6,430		8,425
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	1,246		1,246		1,322
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	488		488		504
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	8,164		8,164		10,251
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	3,487		3,487		3,171
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	1,618		1,618		1,518
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	36,302		36,302		28,138
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	36,302		36,302		28,138
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	419		419		1,099
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	42		42		352
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	508		508		264
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	550		550		616
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	2,583		2,583		1,280
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	661		661		287
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	4,213		4,213		3,282
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	1,648		1,648		2,329
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	301		301		235
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	355		355		333
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	2,304		2,304		2,897
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	1,248		1,248		727
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	487		487		362
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		1
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	8,252		8,252		7,269
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	8,252		8,252		7,269
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	978		978		303
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	52		52		279
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	52		52		279
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	3,583		3,583		702
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	1,900		1,900		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	6,513		6,513		1,284
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	159		159		712
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	87		87		167
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	487		487		567
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	733		733		1,446
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	1,684		1,684		734
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	432		432		14
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	0		0		311
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	9,362		9,362		3,789
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	$ 9,362		$ 9,362		$ 3,789