Common Stock (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2013 Subsequent Event
Common Stock [Line Items]
Dividends declared, per share	$ 0.055	$ 0.055	$ 0.055	$ 0.055
Dividends declared, date of declaration	Feb. 07, 2013	Dec. 06, 2012	Sep. 06, 2012	May 09, 2013
Dividends declared, date of record	Mar. 15, 2013	Dec. 17, 2012	Sep. 17, 2012	Jun. 14, 2013
Dividends declared, date of distribution	Mar. 26, 2013	Dec. 28, 2012	Sep. 28, 2012	Jun. 25, 2013