Equity - Additional Information (Detail) (USD $)	1 Months Ended						9 Months Ended			1 Months Ended	3 Months Ended		1 Months Ended
	Aug. 31, 2012	May 31, 2012	Feb. 28, 2012	Aug. 31, 2011	May 31, 2011	Feb. 13, 2011	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Jul. 02, 2012 Common Stock	Jun. 30, 2012 Common Stock	Apr. 02, 2012 Common Stock	Feb. 13, 2011 IPO	Feb. 13, 2011 IPO Common Stock	Oct. 28, 2011 IPO Series A Cumulative Redeemable Preferred Stock	Feb. 13, 2011 Director Common Stock
Class of Stock [Line Items]
New issued stock (in shares)													26,000,000	27,274,000	2,000,000
New issued stock, par value														$ 0.01	$ 0.01
Common shares issued to directors																4,000
Options granted						940,000
Common stock redemptions										745,130		3,270,062
Stock awards, independent directors and executive officers											208,027
Common stock shares issued							31,501,219	30,756,089	27,278,000
Dividends paid to common stockholders	$ 0.1125	$ 0.1125	$ 0.1125	$ 0.1125	$ 0.1125
Percentage of redeemable preferred stock															9.25%
Dividends paid to preferred stockholders	$ 0.578125	$ 0.578125	$ 0.578125