Acquisitions - Summary of Pro Forma Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	4 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012
Business Combinations [Abstract]
Net interest income	$ 3,534	$ 81,331	$ 80,352
Noninterest income	513	16,624	15,312
Noninterest expense	2,047	60,024	56,835
Net income	$ 1,300	$ 20,477	$ 17,573
Earnings per share:
Fully diluted		$ 0.57	$ 0.54