Loans Held for Investment (Details 5) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Other information concerning the credit quality
Current	$ 2,127,575	$ 1,628,347	$ 1,323,892
30-59 Days Past Due	645	20	118
60-89 Days Past Due	375	24	32
90+ Days Past Due	2,258	54	1,427
Total	2,130,853	1,628,445	1,325,469
Non-Accruing	4,663	1,444	2,674
Business loans: Commercial and industrial
Other information concerning the credit quality
Current	417,894	428,183	271,845
30-59 Days Past Due	146
60-89 Days Past Due		24	32
90+ Days Past Due	2,178
Total	420,218	428,207	271,877
Non-Accruing	2,455		31
Business loans: Commercial owner occupied
Other information concerning the credit quality
Current	351,600	210,995	223,402
30-59 Days Past Due	349
60-89 Days Past Due	375
90+ Days Past Due	27		446
Total	352,351	210,995	223,848
Non-Accruing	527	514	864
Business loans: SBA
Other information concerning the credit quality
Current	49,855	28,404	10,985
30-59 Days Past Due			46
90+ Days Past Due			14
Total	49,855	28,404	11,045
Non-Accruing			14
Business loans: Warehouse facilities
Other information concerning the credit quality
Current	216,554	113,798	81,033
Total	216,554	113,798	81,033
Real estate loans: Commercial non-owner occupied
Other information concerning the credit quality
Current	452,422	359,213	332,572
90+ Days Past Due			918
Total	452,422	359,213	333,490
Non-Accruing	1,602	848	1,327
Real estate loans: Multi-family
Other information concerning the credit quality
Current	397,130	262,965	223,200
Total	397,130	262,965	223,200
Real estate loans: One-to-four family
Other information concerning the credit quality
Current	116,533	122,722	141,348
30-59 Days Past Due	149	19	72
90+ Days Past Due	53	54	49
Total	116,735	122,795	141,469
Non-Accruing	79	82	438
Real estate loans: Construction
Other information concerning the credit quality
Current	111,704	89,682	29,857
Total	111,704	89,682	29,857
Real estate loans: Land
Other information concerning the credit quality
Current	7,243	9,088	6,170
Total	7,243	9,088	6,170
Other loans
Other information concerning the credit quality
Current	6,640	3,297	3,480
30-59 Days Past Due	1	1
Total	$ 6,641	$ 3,298	$ 3,480