Segment Reporting - Schedule of Financial Information with Respect to Company's Reportable Business Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Net interest income	$ 35,264	$ 29,476	$ 69,748	$ 57,814
Provision for loan losses	1,365	4,165	3,091	7,088
Noninterest income	15,819	11,384	28,573	22,744
Noninterest expense:
Salaries and employee benefits	16,942	13,381	34,336	27,187
Equipment and occupancy expenses	4,071	2,978	8,135	5,909
Data processing and telecommunications expenses	3,940	2,836	7,394	5,406
Other expenses	12,365	7,493	20,692	17,070
Total noninterest expense	37,318	26,688	70,557	55,572
Income before income tax expense	12,400	10,007	24,673	17,898
Income tax expense	4,270	3,329	8,193	5,935
Net income	8,130	6,678	16,480	11,963
Less preferred stock dividends		442	286	883
Net income available to common shareholders	8,130	6,236	16,194	11,080
Total assets	3,973,135	2,808,675	3,973,135	2,808,675	3,667,649
Stockholders' equity	343,399	287,777	343,399	287,777	316,699
Retail Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	33,925	28,517	67,309	56,283
Provision for loan losses	1,365	4,165	3,091	7,088
Noninterest income	8,817	6,383	16,407	13,279
Noninterest expense:
Salaries and employee benefits	13,005	10,478	26,831	21,515
Equipment and occupancy expenses	3,771	2,781	7,533	5,546
Data processing and telecommunications expenses	3,597	2,634	6,929	5,105
Other expenses	11,053	6,444	18,565	15,334
Total noninterest expense	31,426	22,337	59,858	47,500
Income before income tax expense	9,951	8,398	20,767	14,974
Income tax expense	3,413	2,766	6,826	4,912
Net income	6,538	5,632	13,941	10,062
Less preferred stock dividends		442	286	883
Net income available to common shareholders	6,538	5,190	13,655	9,179
Total assets	3,797,850	2,695,554	3,797,850	2,695,554
Stockholders' equity	345,256	286,127	345,256	286,127
Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	1,339	959	2,439	1,531
Noninterest income	7,002	5,001	12,166	9,465
Noninterest expense:
Salaries and employee benefits	3,937	2,903	7,505	5,672
Equipment and occupancy expenses	300	197	602	363
Data processing and telecommunications expenses	343	202	465	301
Other expenses	1,312	1,049	2,127	1,736
Total noninterest expense	5,892	4,351	10,699	8,072
Income before income tax expense	2,449	1,609	3,906	2,924
Income tax expense	857	563	1,367	1,023
Net income	1,592	1,046	2,539	1,901
Net income available to common shareholders	1,592	1,046	2,539	1,901
Total assets	175,285	113,121	175,285	113,121
Stockholders' equity	$ 1,857	$ 1,650	$ 1,857	$ 1,650