Significant Accounting Policies (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Noncontrolling interests:
Balance	$ 5,951,505
Other comprehensive income (loss) allocable to noncontrolling interests:
Unrealized gain (loss) on derivative hedge agreements	10,099	(7,533)
Net loss reclassified from accumulated other comprehensive loss into earnings	2,627	2,697
Currency translation adjustments	(124,512)	13,733
Changes in available-for-sale securities and other	5,637	479
Purchase and dispositions of noncontrolling interests, net and other	(5,629)
Balance	5,765,063
Noncontrolling Interests
Noncontrolling interests:
Balance	858,328	973,226
Net income attributable to noncontrolling interests after preferred distributions and income attributable to redeemable noncontrolling interests in consolidated properties	62,021	57,650
Distributions to noncontrolling interest holders	(74,910)	(77,436)
Other comprehensive income (loss) allocable to noncontrolling interests:
Unrealized gain (loss) on derivative hedge agreements	1,481	(1,236)
Net loss reclassified from accumulated other comprehensive loss into earnings	381	392
Currency translation adjustments	(17,998)	1,932
Changes in available-for-sale securities and other	777	72
Other comprehensive income (loss)	(15,359)	1,160
Adjustment to limited partners' interest from change in ownership in the Operating Partnership	(5,624)	(67,226)
Units issued to limited partners		84,910
Units exchanged for common shares	(7,849)	(911)
Long-term incentive performance units	11,828	12,485
Purchase and dispositions of noncontrolling interests, net and other	183	6,130
Balance	$ 828,618	$ 989,988