Debt - Additional Information (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Outstanding borrowings under credit facility	$ 30,500,000	$ 79,500,000
Maximum borrowing availability under revolving credit facility	115,000,000
Consolidated fixed charge coverage ratio	2.03
Fixed Rate Debt
Debt Instrument [Line Items]
Estimated fair value of debt	177,900,000	168,200,000
Variable rate debt
Debt Instrument [Line Items]
Estimated fair value of debt	30,500,000	79,500,000
Senior Secured Revolving Credit Facility
Debt Instrument [Line Items]
Outstanding borrowings under credit facility	30,500,000	79,500,000
Number of properties in borrowing base securing borrowing under credit facility	11
Maximum borrowing availability under revolving credit facility	$ 115,000,000