Debt - Additional Information (Detail) (USD $)	1 Months Ended			3 Months Ended	12 Months Ended
	Oct. 31, 2012	Mar. 31, 2012	Jun. 30, 2011	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Oct. 10, 2012	Sep. 07, 2012	Mar. 29, 2012	Jan. 10, 2012	Jun. 01, 2011	Mar. 07, 2011	Jan. 19, 2011
Debt Disclosure [Line Items]
Unamortized deferred loan fees written off					$ 600,000	$ 600,000
Loan transfer and consent fees paid					9,000,000
Non-recourse mortgage loan	10 years
Original principal amount of non-recourse mortgage loan							111,000,000
Interest rate	3.98%
Maturity date of loan	Nov. 01, 2022
Number of year non-recourse mortgage loan									7 years
Principal of non-recourse mortgage loan									21,900,000		84,500,000
Non-recourse mortgage loan, maturity date		Apr. 01, 2019	Jul. 01, 2016
Fixed rate interest on non-recourse loan									3.94%		3.97%
Non-recourse mortgage loan, term			5 years
Revolving credit facility borrowing limit, maximum borrowing capacity													250,000,000
Revolving credit facility borrowing limit, maximum allowable borrowing amount					226,300,000
Revolving credit facility borrowing limit,amount borrowed				164,000,000	164,000,000
Years, maximum maturities of securities												30 years
Year, extension on term of revolving credit facility					1 year
Percent of secured indebtedness of the company's secured total asset value								55.00%
Line of credit facility material acquisition					Greater than $100 million
Maximum leverage ratio of revolving credit facility										60.00%
Minimum fixed charge coverage ratio on revolving credit facility										1.50
Maximum secured leverage ratio on revolving credit facility								55.00%
Percent minimum tangible net worth in relation to tangible net worth as of Offering													75.00%
Percent of net proceeds of any additional equity issuances in relation to net proceeds as of Offering													85.00%
Maximum principal amount of recourse indebtedness outstanding at any time, aside from revolving credit facility										35,000,000
Percentage annual distributions cannot exceed funds from operations					95.00%
Subject to meeting specified requirements and obtaining additional commitments
Debt Disclosure [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity													400,000,000
Defeasance Costs
Debt Disclosure [Line Items]
Early extinguishment of debt					24,300,000
Fair Value Adjustment
Debt Disclosure [Line Items]
Early extinguishment of debt					$ 900,000