Acquisitions, Dispositions, and Mortgage Funding (Details Textual) (USD $)			6 Months Ended			3 Months Ended
	Jun. 30, 2013 Property	Dec. 31, 2012 Property	Jun. 30, 2013 Oklahoma and Missouri [Member] Mortgage Note Financing [Member] mortgage_note_receivable	Jun. 30, 2013 OKLAHOMA Mortgage Note Financing [Member]	Jun. 30, 2013 MISSOURI Mortgage Note Financing [Member]	Jun. 30, 2013 TEXAS
Acquisitions and Dispositions [Line Items]
Payments to fund mortgage notes receivable			$ 45,900,000	$ 18,100,000	$ 27,800,000
Number of mortgage notes funded			2
Mortgage notes receivable	212,313,000	162,191,000	164,300,000	74,900,000	89,400,000
Estimated Remaining Fundings				16,300,000	22,000,000
Proceeds from noncontrolling interest						1,400,000
Noncontrolling interest, ownership percentage by parent						40.00%
Partnership, ownership percentage	60.00%
Partnership, permanent mortgage loan upon settlement of equity contributions	10,300,000
Partnership, consolidated mortgage loan	$ 13,700,000
Number of properties held for sale	2	1