Shareholders' Equity - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended		3 Months Ended
	Nov. 26, 2012	Dec. 31, 2012 2010 Repurchase Plan [Member]	Nov. 16, 2010 2010 Repurchase Plan [Member]	Jun. 27, 2012 Dutch Auction Tender Offer [Member]	May 30, 2012 Dutch Auction Tender Offer [Member]
Shareholders' Equity [Line Items]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased			470,000
Repurchase of common stock number of shares purchased		140,000
Treasury Stock Acquired, Average Cost Per Share		$ 17.59
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased		330,000
Maximum limit of purchase					$ 10,000,000
Repurchase program maturity date				Jun. 27, 2012
Minimum tender price				$ 12.00
Maximum tender price				$ 13.50
Tender price increments				$ 0.25
Number of shares properly tendered				307,000
Purchase price company accepts in accordance with terms of offer to purchase				$ 13.50
Approximate percentage of common stock outstanding				6.90%
Shares outstanding with completion of tender offer				4,121,000
Purchase price paid by company in connection to tender offer excluding transaction costs				4,147,000
Cash dividend per common share	$ 2.00
Cash dividend paid	$ 8,322,000