Unconsolidated Real Estate Joint Ventures (Unaudited Condensed Financial Information) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Debt	$ 1,475,336				$ 1,368,832				$ 1,475,336	$ 1,368,832
Note payable to EPR	0				0				0	0
Net income	63,042	43,502	32,476	41,206	29,281	34,175	36,818	21,390	180,226	121,664	115,266
Atlantic-EPR I and II [Member]
Rental properties, net	44,644				45,496				44,644	45,496	46,600
Cash	512				278				512	278	1,071
Debt	0				11,827				0	11,827	12,224
Partners' equity	18,372				18,675				18,372	18,675	34,772
Rental revenue									4,373	5,604	6,523
Net income									1,430	1,842	1,874
Atlantic-EPR II [Member]
Note payable to EPR	11,796				0				11,796	0	0
Atlantic-EPR I [Member]
Note payable to EPR	$ 21,293				$ 17,979				$ 21,293	$ 17,979	$ 0