Business Combinations - Pro Forma Information of Acquisitions (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Prosperity Banking Company [Member]	Dec. 31, 2012 Prosperity Banking Company [Member]
Business Acquisition [Line Items]
Net interest income and noninterest income	$ 176,262	$ 187,826	$ 187,927	$ 199,089
Net income	(10,233)	(17,744)	19,927	15,604
Net income available to common shareholders			$ 18,189	$ 12,027
Net income common share available to common shareholders - basic			$ 0.73	$ 0.48
Net income per common share available to common shareholders - diluted			$ 0.71	$ 0.48
Average number shares outstanding, basic	23,816	23,446	25,087	24,985
Average number shares outstanding, diluted	23,857	23,538	25,634	25,026