Net Income (Loss) Per Class A Share - Basic and Diluted Net Income (Loss) Per Class A Share (Parenthetical) (Detail) (USD $)	3 Months Ended		6 Months Ended		1 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Feb. 10, 2012 Class A Shares [Member]	May 06, 2013 Class A Shares [Member]	Feb. 08, 2013 Class A Shares [Member]	May 08, 2012 Class A Shares [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distribution on Class A shares	$ 0.57	$ 0.25	$ 1.62	$ 0.71	$ 0.46	$ 0.57	$ 1.05	$ 0.25