Loans Held for Investment Internal Risk Grading System (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Credit Risk Grades
Totals	$ 2,167,547	$ 1,628,445	$ 1,547,911
Commercial and industrial
Credit Risk Grades
Totals	288,982	228,979	218,871
Franchise
Credit Risk Grades
Totals	295,965	199,228	163,887
Commercial owner occupied
Credit Risk Grades
Totals	302,556	210,995	215,938
SBA
Credit Risk Grades
Totals	70,191	28,404	20,482
Warehouse facilities
Credit Risk Grades
Totals	144,274	113,798	108,093
Commercial non-owner occupied
Credit Risk Grades
Totals	406,490	359,213	355,984
Multi-family
Credit Risk Grades
Totals	421,240	262,965	262,588
One-to-four family
Credit Risk Grades
Totals	78,781	122,795	125,326
Construction
Credit Risk Grades
Totals	141,293	89,682	67,118
Land
Credit Risk Grades
Totals	12,758	9,088	6,103
Other loans
Credit Risk Grades
Totals	5,017	3,298	3,521
Pass
Credit Risk Grades
Totals	2,143,143	1,612,143	1,529,964
Pass | Commercial and industrial
Credit Risk Grades
Totals	285,931	227,151	217,093
Pass | Franchise
Credit Risk Grades
Totals	294,335	199,228	163,887
Pass | Commercial owner occupied
Credit Risk Grades
Totals	291,121	202,390	206,096
Pass | SBA
Credit Risk Grades
Totals	70,191	28,132	20,482
Pass | Warehouse facilities
Credit Risk Grades
Totals	144,274	113,798	108,093
Pass | Commercial non-owner occupied
Credit Risk Grades
Totals	403,020	355,274	351,614
Pass | Multi-family
Credit Risk Grades
Totals	417,576	261,956	261,574
Pass | One-to-four family
Credit Risk Grades
Totals	77,729	122,146	124,383
Pass | Construction
Credit Risk Grades
Totals	141,293	89,682	67,118
Pass | Land
Credit Risk Grades
Totals	12,656	9,088	6,103
Pass | Other loans
Credit Risk Grades
Totals	5,017	3,298	3,521
Special Mention
Credit Risk Grades
Totals	2,311	773	891
Special Mention | Commercial and industrial
Credit Risk Grades
Totals	80	0	0
Special Mention | Franchise
Credit Risk Grades
Totals	0	0	0
Special Mention | Commercial owner occupied
Credit Risk Grades
Totals	1,274	0	387
Special Mention | SBA
Credit Risk Grades
Totals	0	272	0
Special Mention | Warehouse facilities
Credit Risk Grades
Totals	0	0	0
Special Mention | Commercial non-owner occupied
Credit Risk Grades
Totals	259	0	0
Special Mention | Multi-family
Credit Risk Grades
Totals	698	501	504
Special Mention | One-to-four family
Credit Risk Grades
Totals	0	0	0
Special Mention | Construction
Credit Risk Grades
Totals	0	0	0
Special Mention | Land
Credit Risk Grades
Totals	0	0	0
Special Mention | Other loans
Credit Risk Grades
Totals	0	0	0
Substandard
Credit Risk Grades
Totals	22,093	15,529	17,056
Substandard | Commercial and industrial
Credit Risk Grades
Totals	2,971	1,828	1,778
Substandard | Franchise
Credit Risk Grades
Totals	1,630	0	0
Substandard | Commercial owner occupied
Credit Risk Grades
Totals	10,161	8,605	9,455
Substandard | SBA
Credit Risk Grades
Totals	0	0	0
Substandard | Warehouse facilities
Credit Risk Grades
Totals	0	0	0
Substandard | Commercial non-owner occupied
Credit Risk Grades
Totals	3,211	3,939	4,370
Substandard | Multi-family
Credit Risk Grades
Totals	2,966	508	510
Substandard | One-to-four family
Credit Risk Grades
Totals	1,052	649	943
Substandard | Construction
Credit Risk Grades
Totals	0	0	0
Substandard | Land
Credit Risk Grades
Totals	102	0	0
Substandard | Other loans
Credit Risk Grades
Totals	$ 0	$ 0	$ 0