Schedule I (Parentheticals) (Details)					0 Months Ended						0 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Nov. 30, 2012 Depositary Units [Member]	Aug. 31, 2012 Depositary Units [Member]	May 31, 2012 Depositary Units [Member]	Mar. 30, 2012 Depositary Units [Member]	Dec. 31, 2012 Parent Company [Member]	Dec. 31, 2011 Parent Company [Member]	Nov. 30, 2012 Parent Company [Member] Depositary Units [Member]	Aug. 31, 2012 Parent Company [Member] Depositary Units [Member]	May 31, 2012 Parent Company [Member] Depositary Units [Member]	Mar. 30, 2012 Parent Company [Member] Depositary Units [Member]
Limited partners: Depositary units issued	104,850,813	86,708,914							104,850,813	86,708,914
Limited partners: Depositary units outstanding	104,850,813	85,571,714							104,850,813	85,571,714
Units issued as a unit distribution					621,064	627,651	532,190	619,585			621,064	627,651	532,190	619,585
Treasury units at cost, units outstanding	0	1,137,200	1,137,200	1,137,200					0	1,137,200