Unconsolidated Real Estate Joint Ventures (Unaudited Condensed Financial Information) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Long-term debt	$ 1,270,560,000		$ 1,270,560,000		$ 1,154,295,000
Note payable to EPR	0		0		0
Net income	36,818,000	2,000	58,208,000	41,735,000
Atlantic-EPR I [Member]
Advanced under secure mortgage loan agreement			4,000,000
Rental properties, net	25,702,000	26,346,000	25,702,000	26,346,000
Cash	10,000	1,178,000	10,000	1,178,000
Long-term debt	15,165,000	0	15,165,000	0
Partners' equity	10,683,000	27,634,000	10,683,000	27,634,000
Rental revenue			1,360,000	2,283,000
Net income			(97,000)	816,000
Atlantic-EPR II [Member]
Rental properties, net	20,346,000	20,807,000	20,346,000	20,807,000
Cash	131,000	231,000	131,000	231,000
Long-term debt	12,028,000	12,413,000	12,028,000	12,413,000
Note payable to EPR	117,000	117,000	117,000	117,000
Partners' equity	8,059,000	8,140,000	8,059,000	8,140,000
Rental revenue			1,444,000	1,444,000
Net income			$ 728,000	$ 679,000