Significant Accounting Policies (Details 5) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Noncontrolling interests:
Balance			$ 6,893,089
Other comprehensive income (loss) allocable to noncontrolling interests:
Unrealized (loss) gain on derivative hedge agreements	(1,796)	(8,587)	5,275	3,105
Net loss reclassified from accumulated other comprehensive loss into earnings	2,566	5,138	4,076	10,252
Currency translation adjustments	(22,960)	(65,453)	(21,912)	(21,511)
Changes in available-for-sale securities and other	(631)	(666)	(815)	23,869
Other comprehensive income (loss)			(11,427)
Balance	6,806,247		6,806,247
Noncontrolling Interests
Noncontrolling interests:
Balance	977,753	1,215,628	982,486	894,622
Net income attributable to noncontrolling interests after preferred distributions and income attributable to redeemable noncontrolling interests in consolidated properties	57,202	42,308	104,761	175,318
Distributions to noncontrolling interest holders	(60,082)	(61,107)	(119,907)	(119,205)
Other comprehensive income (loss) allocable to noncontrolling interests:
Unrealized (loss) gain on derivative hedge agreements	(219)	(1,395)	740	1,006
Net loss reclassified from accumulated other comprehensive loss into earnings	368	858	586	1,716
Currency translation adjustments	(3,285)	(10,957)	(3,158)	(3,433)
Changes in available-for-sale securities and other	(92)	(138)	(117)	3,819
Other comprehensive income (loss)	(3,228)	(11,632)	(1,949)	3,108
Adjustment to limited partners' interest from change in ownership in the Operating Partnership	(7,934)	(7,547)	(10,581)	156,299
Units exchanged for common shares	(3,461)	(2,600)	(5,982)	(4,018)
Purchase of noncontrolling interest and other	11,248	10,368	22,670	79,294
Balance	$ 971,498	$ 1,185,418	$ 971,498	$ 1,185,418