Segment Reporting - Schedule of Financial Information with Respect to Company's Reportable Business Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Net interest income	$ 34,484	$ 28,338
Provision for loan losses	1,726	2,923
Noninterest income	12,754	11,360
Noninterest expense:
Salaries and employee benefits	17,394	13,806
Equipment and occupancy expenses	4,064	2,931
Data processing and telecommunications expenses	3,454	2,570
Other expenses	8,327	9,577
Total noninterest expense	33,239	28,884
Income before income tax expense	12,273	7,891
Income tax expense	3,923	2,606
Net income	8,350	5,285
Less preferred stock dividends	286	441
Net income available to common shareholders	8,064	4,844
Total assets	3,487,984	2,861,651	3,667,649
Stockholders' equity	300,030	283,722	316,699
Retail Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	33,384	27,766
Provision for loan losses	1,726	2,923
Noninterest income	7,590	6,896
Noninterest expense:
Salaries and employee benefits	13,826	11,037
Equipment and occupancy expenses	3,762	2,765
Data processing and telecommunications expenses	3,332	2,471
Other expenses	7,512	8,890
Total noninterest expense	28,432	25,163
Income before income tax expense	10,816	6,576
Income tax expense	3,413	2,146
Net income	7,403	4,430
Less preferred stock dividends	286	441
Net income available to common shareholders	7,117	3,989
Total assets	3,359,912	2,784,883
Stockholders' equity	296,978	282,851
Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net interest income	1,100	572
Noninterest income	5,164	4,464
Noninterest expense:
Salaries and employee benefits	3,568	2,769
Equipment and occupancy expenses	302	166
Data processing and telecommunications expenses	122	99
Other expenses	815	687
Total noninterest expense	4,807	3,721
Income before income tax expense	1,457	1,315
Income tax expense	510	460
Net income	947	855
Net income available to common shareholders	947	855
Total assets	128,072	76,768
Stockholders' equity	$ 3,052	$ 871