Debt - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Sep. 07, 2012	Jan. 10, 2012	Mar. 07, 2011	Jan. 19, 2011
Debt Disclosure [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity					$ 250.0
Revolving credit facility borrowing limit, maximum allowable borrowing amount	226.2
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			35.0
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					$ 400.0