Pending Merger and Acquisition - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended	1 Months Ended
	Jun. 30, 2013 Prosperity Bank [Member] Location	May 01, 2013 Prosperity Banking Company [Member]	Dec. 31, 2012 Prosperity Banking Company [Member]
Business Acquisition [Line Items]
Number of banking locations	12
Reported assets of Prosperity			$ 742
Reported loans of Prosperity			464
Reported deposits of Prosperity			478
Shares to receive for each share of Prosperity common stock pursuant to the merger agreement		3.125
Cash to receive for each share of Prosperity common stock pursuant to the merger agreement		$ 41.50
Maximum consideration in form of cash		50.00%
Stock consideration		100.00%
Transaction amount		$ 15.7
Company's closing stock price		$ 13.32
Prosperity's common shares outstanding		377,960