Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended				9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	May 31, 2013 Class A Common Stock [Member]	Sep. 30, 2013 REIT [Member]	Dec. 31, 2012 Capital Loss Carryforwards Expiring 2013 [Member]	Dec. 31, 2012 Capital Loss Carryforwards Expiring 2014 [Member]	Dec. 31, 2012 Capital Loss Carryforwards Expiring 2015 [Member]	Dec. 31, 2012 Capital Loss Carryforwards Expiring 2017 [Member]	Dec. 31, 2012 Total Capital Loss Carryforwards [Member]
Tax Credit Carryforward [Line Items]
Annual distribution of net taxable income for U.S. federal income tax not to apply to our earnings that we distribute (percent)			90.00%
Net taxable income subject to distribution (percent)			100.00%
Excise tax rate			4.00%
Income tax provision	$ (264,000)	$ 166,000	$ 329,000	$ 467,000			$ 329,000
Common stock, shares issued	28,802,000		28,802,000		2,927,000	25,875,000
Net operating loss carried forward					161,500,000
Net capital losses carried forward								$ 2,000,000	$ 87,400,000	$ 31,400,000	$ 602,000	$ 121,400,000
NOL expiration date			Expires in 2029