Summary of Significant Accounting Policies - AOCI, Simon Property Group L.P. (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Simon Property Group, L.P.
Changes in accumulated other comprehensive income (loss)
Beginning Balance	$ 4,235,026
Ending balance	4,029,536
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss)
Other comprehensive income (loss) before reclassifications	5,835
Amounts reclassified from accumulated other comprehensive income (loss)	1,871
Net current-period other comprehensive income (loss)	7,706
Accumulated Other Comprehensive Income (Loss) | Simon Property Group, L.P.
Changes in accumulated other comprehensive income (loss)
Beginning Balance	(127,102)
Other comprehensive income (loss) before reclassifications	6,657
Amounts reclassified from accumulated other comprehensive income (loss)	2,153
Net current-period other comprehensive income (loss)	8,810
Ending balance	(118,292)
Currency translation adjustments
Changes in accumulated other comprehensive income (loss)
Other comprehensive income (loss) before reclassifications	11,429
Net current-period other comprehensive income (loss)	11,429
Currency translation adjustments | Simon Property Group, L.P.
Changes in accumulated other comprehensive income (loss)
Beginning Balance	(135,940)
Other comprehensive income (loss) before reclassifications	13,092
Net current-period other comprehensive income (loss)	13,092
Ending balance	(122,848)
Accumulated derivative gains (losses), net
Changes in accumulated other comprehensive income (loss)
Other comprehensive income (loss) before reclassifications	(5,343)
Amounts reclassified from accumulated other comprehensive income (loss)	1,871
Net current-period other comprehensive income (loss)	(3,472)
Accumulated derivative gains (losses), net | Simon Property Group, L.P.
Changes in accumulated other comprehensive income (loss)
Beginning Balance	9,263
Other comprehensive income (loss) before reclassifications	(6,146)
Amounts reclassified from accumulated other comprehensive income (loss)	2,153
Net current-period other comprehensive income (loss)	(3,993)
Ending balance	5,270
Net unrealized losses on marketable securities
Changes in accumulated other comprehensive income (loss)
Other comprehensive income (loss) before reclassifications	(251)
Net current-period other comprehensive income (loss)	(251)
Net unrealized losses on marketable securities | Simon Property Group, L.P.
Changes in accumulated other comprehensive income (loss)
Beginning Balance	(425)
Other comprehensive income (loss) before reclassifications	(289)
Net current-period other comprehensive income (loss)	(289)
Ending balance	$ (714)