Shareholders' Equity - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended			1 Months Ended		12 Months Ended			52 Months Ended		1 Months Ended
	Feb. 13, 2002	Dec. 31, 2012 Vote	Dec. 31, 2011	Dec. 31, 2010	Feb. 13, 2002 Minimum	Feb. 13, 2002 Series A Preferred Stock	Dec. 31, 2012 Stock Repurchase Program	Dec. 31, 2011 Stock Repurchase Program	Dec. 31, 2010 Stock Repurchase Program	Dec. 31, 2012 Stock Repurchase Program	Aug. 28, 2008 Stock Repurchase Program Maximum	Jan. 22, 2013 Dividend Declared
Stockholders Equity Note [Line Items]
Common stock votes per share		1
Dividends declared per common share												$ 0.27
Cash dividend, payment date												Feb. 15, 2013
Cash dividend, record date												Feb. 01, 2013
Preferred stock, shares authorized		5,000	5,000			2,000
Dividend distribution of rights declared for each outstanding share of common stock	1
Declaration date for dividend of one right per share of Common Stock	Feb. 13, 2002
Record date for dividend of one right per share of Common Stock	Feb. 25, 2002
Beneficial interest percentage					15.00%
Shares entitled to purchase						0.015
Incentive Stock purchase price						$ 133
Rights redemption price						$ 0.01
Date on which rights expire						2012-02-13
Multiplier for exercise price per share for acquiring Common Stock						2
Board of Directors authorized the repurchase of common stock											2,000,000
Repurchased and retired, shares							60,000	55,000	19,500	1,877,576
Repurchased and retired, aggregate price		$ 5,727	$ 6,649	$ 1,212			$ 5,727	$ 6,649	$ 1,212	$ 78,301