Significant Accounting Policies - Rollforward Of Noncontrolling Interest, Simon Group Property, Inc. (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Noncontrolling interests:
Balance			$ 5,216,369
Other comprehensive income (loss) allocable to noncontrolling interests:
Unrealized (loss) gain on derivative hedge agreements	$ (1,256)	$ (6,884)	(16,351)	$ 12,455
Net loss (gain) reclassified from accumulated other comprehensive loss into earnings	3,199	2,819	145,737	(72,090)
Currency translation adjustments	1,447	(6,033)	18,888	(144,826)
Changes in available-for-sale securities and other	1,313	8,004	13,375	(14,080)
Contributions by noncontrolling interests, net, and other			(1,947)
Balance	5,326,813		5,326,813
Noncontrolling Interests
Noncontrolling interests:
Balance	696,286	766,261	744,905	858,328
Net income attributable to noncontrolling interests after preferred distributions and income attributable to redeemable noncontrolling interests in consolidated properties	77,172	71,175	229,370	243,432
Distributions to noncontrolling interest holders	(79,235)	(81,296)	(239,679)	(234,694)
Other comprehensive income (loss) allocable to noncontrolling interests:
Unrealized (loss) gain on derivative hedge agreements	(164)	(987)	(1,886)	1,874
Net loss (gain) reclassified from accumulated other comprehensive loss into earnings	418	404	19,147	(10,341)
Currency translation adjustments	194	(865)	5,977	(20,530)
Changes in available-for-sale securities and other	172	1,148	1,557	(2,216)
Other comprehensive income (loss)	620	(300)	24,795	(31,213)
Adjustment to limited partners' interest from change in ownership in the Operating Partnership	(9,433)	(9,791)	(28,398)	(91,294)
Units exchanged for common shares	(96)	(2)	(70,101)	(7,907)
Units redeemed				(14,843)
Long-term incentive performance units	12,081	11,819	36,243	35,459
Contributions by noncontrolling interests, net, and other	421	165	681	763
Balance	$ 697,816	$ 758,031	$ 697,816	$ 758,031