Disclosures About Fair Value of Financial Instruments - Balance Sheet Grouping (Details 3) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Available-for-sale securities	$ 211,463	$ 187,565
Held-to-maturity securities	47,344	50,725
Loans held for sale	1,287	573
Loans held for investment	1,894,742	1,799,155	$ 1,433,702
Real estate acquired by foreclosure	4,488	4,863
Level 1 [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and short term investments	168,416	68,923
Available-for-sale securities	75,115	27,035
Other securities	10,831	11,365
Loans held for sale	1,287	573
Total	255,649	107,896
Level 2 [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Available-for-sale securities	136,348	160,530
Held-to-maturity securities	47,344	50,725
Total	183,692	211,255
Financial Liabilities:
Deposits	2,021,048	1,849,281
Securities sold under agreements to repurchase	9,858	4,605
Other borrowed funds	67,140	47,561
Total	2,098,046	1,901,447
Level 3 [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Loans held for investment	1,856,451	1,788,454
Real estate acquired by foreclosure	4,488	4,863
Total	1,860,939	1,793,317
Carrying Value [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and short term investments	168,416	68,923
Available-for-sale securities	211,463	187,565
Held-to-maturity securities	47,419	50,713
Other securities	10,831	11,365
Loans held for sale	1,287	573
Loans held for investment	1,894,742	1,799,155
Real estate acquired by foreclosure	4,488	4,863
Total	2,338,646	2,123,157
Financial Liabilities:
Deposits	2,024,531	1,845,713
Securities sold under agreements to repurchase	9,858	4,605
Other borrowed funds	67,309	47,586
Total	2,101,698	1,897,904
Fair Value [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and short term investments	168,416	68,923
Available-for-sale securities	211,463	187,565
Held-to-maturity securities	47,344	50,725
Other securities	10,831	11,365
Loans held for sale	1,287	573
Loans held for investment	1,856,451	1,788,454
Real estate acquired by foreclosure	4,488	4,863
Total	2,300,280	2,112,468
Financial Liabilities:
Deposits	2,021,048	1,849,281
Securities sold under agreements to repurchase	9,858	4,605
Other borrowed funds	67,140	47,561
Total	$ 2,098,046	$ 1,901,447