Schedule III: Real Estate and Accumulated Depreciation (Rollforward) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Carrying cost:
Balance at beginning of period	$ 19,241,735	$ 20,393,411	$ 18,763,903
Additions during period:
Acquisitions	4,063,355	1,769,790	1,623,648
Capital expenditures	229,560	189,711	183,929
Dispositions:
Sales and/or transfers to assets held for sale	(867,158)	(3,023,401)	(155,184)
Foreign currency translation	(209,460)	(87,776)	(22,885)
Balance at end of period	22,458,032	19,241,735	20,393,411
Accumulated depreciation:
Balance at beginning of period	2,925,508	2,881,950	2,289,783
Additions during period:
Depreciation expense	778,419	725,485	674,141
Dispositions:
Sales and/or transfers to assets held for sale	(144,545)	(675,846)	(78,061)
Foreign currency translation	(14,757)	(6,081)	(3,913)
Balance at end of period	$ 3,544,625	$ 2,925,508	$ 2,881,950