Summary of Significant Accounting Policies - Rollforward Of Noncontrolling Interest, Simon Group Property L.P. (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Noncontrolling interests:
Net income attributable to noncontrolling nonredeemable interests	$ 83,037	$ 58,393	$ 177,213	$ 131,338
Distributions to noncontrolling nonredeemable interest holders	(91,901)	(83,680)	(183,913)	(167,901)
Contributions by noncontrolling nonredeemable interests, net, and other	90	65	114	236
Simon Property Group, L.P.
Noncontrolling interests:
Noncontrolling nonredeemable interests in properties, beginning of period	3,800	4,647	3,738	5,116
Net income attributable to noncontrolling nonredeemable interests	218	397	745	1,072
Distributions to noncontrolling nonredeemable interest holders	(475)	(845)	(964)	(2,160)
Contributions by noncontrolling nonredeemable interests, net, and other	89	65	113	236
Noncontrolling nonredeemable interests in properties, end of period	$ 3,632	$ 4,264	$ 3,632	$ 4,264