Subsequent Events - Additional Information (Detail) (USD $)	3 Months Ended		1 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Apr. 16, 2012 Dividend Declared
Subsequent Event [Line Items]
Dividends declared	$ 0.31	$ 0.23	$ 0.31
Dividend payable date			Jun. 15, 2012
Dividend payable, stockholders of record date			May 23, 2012