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