Business Combinations - Pro Forma Information of Acquisitions (Detail) (Coastal Bankshares, Inc. [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Coastal Bankshares, Inc. [Member]
Business Acquisition [Line Items]
Net interest income and noninterest income	$ 52,590
Net income	9,052
Net income available to common stockholders	$ 8,766
Income per common share available to common stockholders - basic	$ 0.33
Income per common share available to common stockholders - diluted	$ 0.32
Average number of shares outstanding, basic	26,743
Average number of shares outstanding, diluted	27,172