Pending Merger and Acquisition - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended
	May 01, 2013	Jun. 30, 2013
Prosperity Banking Company [Member]
Business Acquisition [Line Items]
Reported assets of Prosperity		$ 754
Reported loans of Prosperity		485
Reported deposits of Prosperity		493
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
Prosperity Bank [Member]
Business Acquisition [Line Items]
Number of banking locations	12