Segment Reporting - Schedule of Financial Information with Respect to Company's Reportable Business Segments (Detail) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Net interest income	$ 40,688		$ 35,264	$ 79,520	$ 69,748
Provision for loan losses	2,656	$ 888	1,365	3,725	3,091	$ 5,648
Noninterest income	20,626		15,819	38,201	28,573
Noninterest expense
Salaries and employee benefits	22,465		16,942	43,097	34,336
Equipment and occupancy expenses	4,809		4,071	9,363	8,135
Data processing and telecommunications expenses	4,214		3,940	8,474	7,394
Other expenses	25,376		12,365	36,757	20,692
Total noninterest expense	56,864		37,318	97,691	70,557
Income (loss) before income tax expense (benefit)	1,794		12,400	16,305	24,673
Income tax expense	486		4,270	5,233	8,193
Net income	1,308		8,130	11,072	16,480
Less preferred stock dividends					286
Net income (loss) available to common shareholders	1,308		8,130	11,072	16,194
Total assets	5,205,734	$ 4,037,077	3,973,135	5,205,734	3,973,135	$ 4,037,077
Intangible assets	106,556		68,715	106,556	68,715
Banking Division [Member]
Segment Reporting Information [Line Items]
Net interest income	36,806		33,345	72,645	66,273
Provision for loan losses	2,456		1,365	3,383	3,091
Noninterest income	9,262		7,449	18,042	14,810
Noninterest expense
Salaries and employee benefits	15,675		12,509	31,037	26,086
Equipment and occupancy expenses	4,376		3,752	8,520	7,501
Data processing and telecommunications expenses	3,913		3,590	7,924	6,916
Other expenses	24,048		10,753	34,404	18,133
Total noninterest expense	48,012		30,604	81,885	58,636
Income (loss) before income tax expense (benefit)	(4,400)		8,825	5,419	19,356
Income tax expense	(1,682)		3,019	1,423	6,332
Net income	(2,718)		5,806	3,996	13,024
Less preferred stock dividends					286
Net income (loss) available to common shareholders	(2,718)		5,806	3,996	12,738
Total assets	4,823,335		3,744,089	4,823,335	3,744,089
Intangible assets	106,556		68,715	106,556	68,715
Retail Mortgage Division [Member]
Segment Reporting Information [Line Items]
Net interest income	1,979		972	3,524	1,886
Provision for loan losses	200			342
Noninterest income	9,095		6,836	16,705	11,916
Noninterest expense
Salaries and employee benefits	5,592		3,881	10,119	7,403
Equipment and occupancy expenses	396		300	776	601
Data processing and telecommunications expenses	279		329	491	443
Other expenses	1,150		1,233	2,082	2,008
Total noninterest expense	7,417		5,743	13,468	10,455
Income (loss) before income tax expense (benefit)	3,457		2,065	6,419	3,347
Income tax expense	1,210		723	2,246	1,171
Net income	2,247		1,342	4,173	2,176
Net income (loss) available to common shareholders	2,247		1,342	4,173	2,176
Total assets	235,067		131,275	235,067	131,275
Warehouse Lending Division [Member]
Segment Reporting Information [Line Items]
Net interest income	1,179		367	2,014	553
Noninterest income	383		166	656	250
Noninterest expense
Salaries and employee benefits	99		56	226	102
Equipment and occupancy expenses	1			3	1
Data processing and telecommunications expenses	20		14	53	22
Other expenses	19		79	55	119
Total noninterest expense	139		149	337	244
Income (loss) before income tax expense (benefit)	1,423		384	2,333	559
Income tax expense	498		134	817	196
Net income	925		250	1,516	363
Net income (loss) available to common shareholders	925		250	1,516	363
Total assets	82,913		44,010	82,913	44,010
SBA Division [Member]
Segment Reporting Information [Line Items]
Net interest income	724		580	1,337	1,036
Noninterest income	1,886		1,368	2,798	1,597
Noninterest expense
Salaries and employee benefits	1,099		496	1,715	745
Equipment and occupancy expenses	36		19	64	32
Data processing and telecommunications expenses	2		7	6	13
Other expenses	159		300	216	432
Total noninterest expense	1,296		822	2,001	1,222
Income (loss) before income tax expense (benefit)	1,314		1,126	2,134	1,411
Income tax expense	460		394	747	494
Net income	854		732	1,387	917
Net income (loss) available to common shareholders	854		732	1,387	917
Total assets	$ 64,419		$ 53,761	$ 64,419	$ 53,761