Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Investment in real estate:
Balance at beginning of year		$ 25,491,935	[1]	$ 23,734,733	[1]	$ 18,082,399
Additions:
Acquisitions		3,364,891		2,210,600		3,597,955
Improvements		445,625		380,298		408,844
Assumed other items, net		389,256		160,897		772,972
Assumed debt		1,064,810		265,152		1,340,939
Total additions		5,264,582		3,016,947		6,120,710
Deductions:
Cost of real estate sold		(449,932)		(916,997)		(498,564)
Reclassification of accumulated depreciation and amortization for assets held for sale		(41,464)		(64,476)		(3,730)
Impairment of assets		(2,220)		0		0
Total deductions		(493,616)		(981,473)		(502,294)
Foreign currency translation on real estate, net		(397,411)		(278,272)		33,918
Balance at end of year	[1]	29,865,490		25,491,935		23,734,733
Accumulated depreciation:
Balance at beginning of year		3,020,908		2,386,658		1,555,055
Additions:
Depreciation and amortization expenses		826,240		844,130		873,960
Amortization of above market leases		11,912		7,935		7,831
Total additions		838,152		852,065		881,791
Deductions:
Sale of properties		(69,735)		(123,582)		(49,625)
Reclassification of accumulated depreciation and amortization for assets held for sale		(41,464)		(64,476)		(3,730)
Total deductions		(111,199)		(188,058)		(53,355)
Foreign currency translation on accumulated depreciation, net		48,436		(29,757)		3,167
Balance at end of year		3,796,297		3,020,908		2,386,658
Reconciliation of real property (Textual) [Abstract]
Aggregate cost for tax purposes for real property		$ 19,159,762		$ 21,621,760		$ 20,260,297

[1] The aggregate cost for tax purposes for real property equals $19,159,762,000, $21,621,760,000, and $20,260,297,000 at December 31, 2015, 2014 and 2013, respectively.