Summary of Significant Accounting Policies (Details 10) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Noncontrolling interests:
Balance	$ 6,893,089	$ 5,544,288	$ 5,633,752
Other comprehensive income (loss) allocable to noncontrolling interests:
Unrealized gain (loss) on derivative hedge agreements	7,101	16,652	(91,933)
Net loss reclassified from accumulated other comprehensive loss into earnings	9,205	21,042	16,169
Currency translation adjustments	2,865	9,200	(8,462)
Changes in available-for-sale securities and other	(1,479)	(39,248)	(37,431)
Other comprehensive income (loss)	17,692	7,646	(121,657)
Balance	6,822,632	6,893,089	5,544,288
Noncontrolling Interests
Noncontrolling interests:
Balance	982,486	894,622	802,972
Net income attributable to noncontrolling interests after preferred distributions and income attributable to redeemable noncontrolling interests in consolidated properties	221,176	274,701	210,240
Distributions to noncontrolling interest holders	(242,881)	(239,207)	(212,526)
Other comprehensive income (loss) allocable to noncontrolling interests:
Unrealized gain (loss) on derivative hedge agreements	1,057	5,634	(15,814)
Net loss reclassified from accumulated other comprehensive loss into earnings	1,317	3,021	2,774
Currency translation adjustments	426	2,435	(1,484)
Changes in available-for-sale securities and other	(213)	(6,807)	(6,340)
Other comprehensive income (loss)	2,587	4,283	(20,864)
Adjustment to limited partners' interest from change in ownership in the Operating Partnership	(29,615)	99,834	(36,032)
Units issued to limited partners		31,324	9,084
Units exchanged for common shares	(11,161)	(144,197)	(9,465)
Units Redeemed		(38,904)
Long-term incentive performance units	45,341	41,470	27,881
Purchase of noncontrolling interests, noncontrolling interests in newly consolidated properties and other	5,293	58,560	123,332
Balance	$ 973,226	$ 982,486	$ 894,622