Loans and Allowance for Loan and Lease Losses - Aging (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Aging of loans held for investment
Current	$ 1,326,424	$ 1,239,201
Past due	1,333,719	1,247,280
Non-Accruing	6,817	7,818
Total	1,333,719	1,247,280
Real Estate Secured
Aging of loans held for investment
Total	1,084,069	1,012,076
Real Estate Secured | Commercial real estate
Aging of loans held for investment
Total	618,400	579,244
Real Estate Secured | Residential 1 to 4 family
Aging of loans held for investment
Total	184,097	165,829
Real Estate Secured | Farmland
Aging of loans held for investment
Total	131,574	120,566
Real Estate Secured | Multi-family residential
Aging of loans held for investment
Total	85,254	79,381
Real Estate Secured | Construction and land
Aging of loans held for investment
Total	36,753	35,669
Real Estate Secured | Home equity lines of credit
Aging of loans held for investment
Total	27,991	31,387
Commercial
Aging of loans held for investment
Total	244,706	229,171
Commercial | Commercial and industrial
Aging of loans held for investment
Total	182,645	164,808
Commercial | Agriculture
Aging of loans held for investment
Total	62,061	64,363
Consumer
Aging of loans held for investment
Total	4,944	6,033
Non-PCI Loans
Aging of loans held for investment
Current	1,318,478	1,230,561
Past due	1,325,702	1,238,505
Non-Accruing	6,746	7,683
Total	1,325,702	1,238,505
Non-PCI Loans | Real Estate Secured
Aging of loans held for investment
Total	1,078,055	1,005,536
Non-PCI Loans | Real Estate Secured | Commercial real estate
Aging of loans held for investment
Current	612,533	571,665
Past due		573,559
Non-Accruing	233	1,894
Total	612,766	573,559
Non-PCI Loans | Real Estate Secured | Residential 1 to 4 family
Aging of loans held for investment
Current	183,976	165,176
Past due		165,256
Non-Accruing		80
Total	183,976	165,256
Non-PCI Loans | Real Estate Secured | Farmland
Aging of loans held for investment
Current	131,497	120,483
Past due		120,566
Non-Accruing	77	83
Total	131,574	120,566
Non-PCI Loans | Real Estate Secured | Multi-family residential
Aging of loans held for investment
Current	85,254	79,381
Past due		79,381
Total	85,254	79,381
Non-PCI Loans | Real Estate Secured | Construction and land
Aging of loans held for investment
Current	32,448	31,419
Past due		35,387
Non-Accruing	4,046	3,968
Total	36,494	35,387
Non-PCI Loans | Real Estate Secured | Home equity lines of credit
Aging of loans held for investment
Current	27,907	31,303
Past due		31,387
Non-Accruing	84	84
Total	27,991	31,387
Non-PCI Loans | Commercial
Aging of loans held for investment
Total	242,703	226,936
Non-PCI Loans | Commercial | Commercial and industrial
Aging of loans held for investment
Current	180,276	162,223
Past due		164,025
Non-Accruing	1,826	1,541
Total	182,102	164,025
Non-PCI Loans | Commercial | Agriculture
Aging of loans held for investment
Current	59,760	62,911
Past due		62,911
Non-Accruing	363
Total	60,601	62,911
Non-PCI Loans | Consumer
Aging of loans held for investment
Current	4,827	6,000
Past due		6,033
Non-Accruing	117	33
Total	4,944	6,033
Non-PCI Loans | MISN
Aging of loans held for investment
Total	145,900	163,800
PCI loans
Aging of loans held for investment
Current	7,946	8,640
Past due		8,775
Non-Accruing	71	135
Total	8,017	8,775
PCI loans | Real Estate Secured
Aging of loans held for investment
Total	6,014	6,540
PCI loans | Real Estate Secured | Commercial real estate
Aging of loans held for investment
Current	5,603	5,639
Past due		5,685
Non-Accruing	31	46
Total	5,634	5,685
PCI loans | Real Estate Secured | Residential 1 to 4 family
Aging of loans held for investment
Current	121	282
Past due		282
Total	121	573
PCI loans | Real Estate Secured | Construction and land
Aging of loans held for investment
Current	259	573
Past due		573
Total	259	282
PCI loans | Commercial
Aging of loans held for investment
Total	2,003	2,235
PCI loans | Commercial | Commercial and industrial
Aging of loans held for investment
Current	503	694
Past due		783
Non-Accruing	40	89
Total	543	783
PCI loans | Commercial | Agriculture
Aging of loans held for investment
Current	1,460	1,452
Past due		1,452
Total	1,460	1,452
Current
Aging of loans held for investment
Non-Accruing	6,100	6,400
30 to 59 Days Past Due
Aging of loans held for investment
Past due	97	66
Non-Accruing	100	28,000
30 to 59 Days Past Due | Non-PCI Loans
Aging of loans held for investment
Past due	97	66
30 to 59 Days Past Due | Non-PCI Loans | Commercial | Commercial and industrial
Aging of loans held for investment
Past due		66
30 to 59 Days Past Due | Non-PCI Loans | Commercial | Agriculture
Aging of loans held for investment
Past due	97
60 to 89 Days Past Due
Aging of loans held for investment
Past due	381	195
Non-Accruing	100	26,000
60 to 89 Days Past Due | Non-PCI Loans
Aging of loans held for investment
Past due	381	195
60 to 89 Days Past Due | Non-PCI Loans | Commercial | Commercial and industrial
Aging of loans held for investment
Past due		195
60 to 89 Days Past Due | Non-PCI Loans | Commercial | Agriculture
Aging of loans held for investment
Past due	381
90+ Days Past Due
Aging of loans held for investment
Non-Accruing	$ 500	$ 1,400