Shareholders' Equity - Additional Information (Detail) (USD $)	1 Months Ended			1 Months Ended			1 Months Ended
	Feb. 13, 2002	Dec. 31, 2011 Vote	Dec. 31, 2010	Feb. 13, 2002 Minimum	Feb. 13, 2002 Series A Preferred Stock	Dec. 31, 2011 Series A Preferred Stock	Jan. 17, 2012 Dividend Declared
Stockholders Equity Note [Line Items]
Common stock votes per share		1
Dividends declared per common share							$ 0.24
Cash dividend, payment date							Feb. 15, 2012
Cash dividend, record date							Feb. 01, 2012
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