Schedule III - Real Estate and Accumulated Depreciation (Details) - Changes in Total Real Estate Assets and Accumulated Depreciation (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Changes in Total Real Estate Assets and Accumulated Depreciation [Abstract]
Balance, beginning of period	$ 8,947,286,646	$ 8,771,256,852	$ 8,587,378,001
Balance, end of period	9,123,343,869	8,947,286,646	8,771,256,852
Balance, beginning of period	1,745,461,577	1,693,089,989	1,549,380,256
Balance, end of period	1,878,680,836	1,745,461,577	1,693,089,989
Acquisitions	475,108,219	411,166,315	406,431,259
Improvements	107,411,806	85,801,777	118,072,955
Transfers from (to) unconsolidated joint ventures	317,995,154	212,231,319	(49,812,485)
Sales	(559,328,593)	(503,767,086)	(186,887,870)
Assets held for sale	(77,664,078)	(9,845,065)	(4,503,823)
Adjustment of fully depreciated asset	(4,780,841)	(21,711,782)	(27,412,282)
Adjustment of property carrying values	(69,463,649)	(34,121,504)	(4,616,890)
Change in exchange rate	(13,220,795)	36,275,820	(67,392,013)
Depreciation for year	243,011,431	248,426,786	237,782,626
Transfers (to) unconsolidated joint ventures		(8,390,550)	(2,725,794)
Sales	(96,915,316)	(161,515,292)	(59,086,170)
Adjustment of fully depreciated asset	(4,780,841)	(21,711,782)	(27,412,282)
Assets held for sale	(7,351,096)	(6,582,611)	(633,676)
Change in exchange rate	$ (744,919)	$ 2,145,037	$ (4,214,971)