Summary of Significant Accounting Policies - Reclassification Out Of AOCI, Simon Property Group, L.P. (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Significant Accounting Policies
Interest expense									$ (809,393)	$ (857,554)	$ (923,697)
Gain upon acquisition of controlling interests and sale or disposal of assets and interests in unconsolidated entities, net									3,647	84,553	250,516
Other Income									296,978	276,544	325,597
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS or UNITHOLDERS	$ 571,116	$ 513,783	$ 381,990	$ 477,736	$ 394,431	$ 504,744	$ 455,389	$ 480,995	1,944,625	1,835,559	1,824,383
Simon Property Group, L.P.
Significant Accounting Policies
Interest expense									(809,393)	(857,554)	(923,697)
Gain upon acquisition of controlling interests and sale or disposal of assets and interests in unconsolidated entities, net									3,647	84,553	250,516
Other Income									296,978	276,544	325,597
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS or UNITHOLDERS	$ 657,774	$ 591,872	$ 439,986	$ 550,006	$ 453,726	$ 581,266	$ 525,447	$ 561,797	2,239,638	2,122,236	2,131,139
Currency translation adjustments | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS or UNITHOLDERS										(118,858)
Currency translation adjustments | Simon Property Group, L.P. | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
Gain upon acquisition of controlling interests and sale or disposal of assets and interests in unconsolidated entities, net										(136,806)
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS or UNITHOLDERS										(136,806)
Accumulated derivative gains (losses), net | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS or UNITHOLDERS									(8,186)	(11,135)	(9,421)
Accumulated derivative gains (losses), net | Simon Property Group, L.P. | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
Interest expense									(9,419)	(12,230)	(10,998)
Gain upon acquisition of controlling interests and sale or disposal of assets and interests in unconsolidated entities, net										(586)
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS or UNITHOLDERS									(9,419)	$ (12,816)	(10,998)
Net unrealized gains (losses) on marketable securities | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS or UNITHOLDERS									18,721		68,685
Net unrealized gains (losses) on marketable securities | Simon Property Group, L.P. | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
Other Income									21,541		80,187
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS or UNITHOLDERS									$ 21,541		$ 80,187