Disclosures About Fair Value of Financial Instruments - Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Available-for-sale securities	$ 280,560	$ 276,021
Held-to-maturity securities	38,006	41,996
Loans held for sale	38,934	384
Loans held for investment	3,047,618	3,130,669	$ 1,982,280
Real estate acquired by foreclosure	2,801	12,122
Level 1 [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and short term investments	313,366	124,906
Available-for-sale securities	113,355	74,974
Other securities	17,955	20,320
Loans held for sale	38,934	384
Total	483,610	220,584
Level 2 [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Available-for-sale securities	167,205	201,047
Held-to-maturity securities	38,006	41,996
Total	205,211	243,043
Financial Liabilities:
Deposits	3,323,421	3,100,748
Securities sold under agreements to repurchase	2,855	3,073
Other borrowed funds	148,941	221,104
Subordinated debentures	13,502	13,187
Total	3,488,719	3,338,112
Level 3 [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Loans held for investment	3,056,110	3,147,615
Real estate acquired by foreclosure	2,801	12,122
Total	3,058,911	3,159,737
Carrying Value [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and short term investments	313,366	124,906
Available-for-sale securities	280,560	276,021
Held-to-maturity securities	37,729	42,130
Other securities	17,955	20,320
Loans held for sale	38,934	384
Loans held for investment	3,047,618	3,130,669
Real estate acquired by foreclosure	2,801	12,122
Total	3,738,963	3,606,552
Financial Liabilities:
Deposits	3,315,899	3,100,748
Securities sold under agreements to repurchase	2,855	3,073
Other borrowed funds	150,000	223,265
Subordinated debentures	13,502	13,187
Total	3,482,256	3,340,273
Fair Value [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and short term investments	313,366	124,906
Available-for-sale securities	280,560	276,021
Held-to-maturity securities	38,006	41,996
Other securities	17,955	20,320
Loans held for sale	38,934	384
Loans held for investment	3,056,110	3,147,615
Real estate acquired by foreclosure	2,801	12,122
Total	3,747,732	3,623,364
Financial Liabilities:
Deposits	3,323,421	3,100,748
Securities sold under agreements to repurchase	2,855	3,073
Other borrowed funds	148,941	221,104
Subordinated debentures	13,502	13,187
Total	$ 3,488,719	$ 3,338,112