Summary of Significant Accounting Policies - AOCI, Simon Property Group L.P. (Details) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($)
Simon Property Group, L.P.
Changes in accumulated other comprehensive income (loss)
Beginning Balance	$ 3,789,558
Ending balance	3,692,948
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss)
Other comprehensive (loss) income before reclassifications	4,110
Amounts reclassified from accumulated other comprehensive income (loss)	945
Net current-period other comprehensive (loss) income	5,055
Accumulated Other Comprehensive Income (Loss) \| Simon Property Group, L.P.
Changes in accumulated other comprehensive income (loss)
Beginning Balance	(145,114)
Other comprehensive (loss) income before reclassifications	4,742
Amounts reclassified from accumulated other comprehensive income (loss)	1,088
Net current-period other comprehensive (loss) income	5,830
Ending balance	(139,284)
Currency translation adjustments
Changes in accumulated other comprehensive income (loss)
Other comprehensive (loss) income before reclassifications	(4,130)
Net current-period other comprehensive (loss) income	(4,130)
Currency translation adjustments \| Simon Property Group, L.P.
Changes in accumulated other comprehensive income (loss)
Beginning Balance	(182,978)
Other comprehensive (loss) income before reclassifications	(4,744)
Net current-period other comprehensive (loss) income	(4,744)
Ending balance	(187,722)
Accumulated derivative gains (losses), net
Changes in accumulated other comprehensive income (loss)
Other comprehensive (loss) income before reclassifications	8,115
Amounts reclassified from accumulated other comprehensive income (loss)	945
Net current-period other comprehensive (loss) income	9,060
Accumulated derivative gains (losses), net \| Simon Property Group, L.P.
Changes in accumulated other comprehensive income (loss)
Beginning Balance	37,916
Other comprehensive (loss) income before reclassifications	9,342
Amounts reclassified from accumulated other comprehensive income (loss)	1,088
Net current-period other comprehensive (loss) income	10,430
Ending balance	48,346
Net unrealized (losses) gains on marketable securities
Changes in accumulated other comprehensive income (loss)
Other comprehensive (loss) income before reclassifications	125
Net current-period other comprehensive (loss) income	125
Net unrealized (losses) gains on marketable securities \| Simon Property Group, L.P.
Changes in accumulated other comprehensive income (loss)
Beginning Balance	(52)
Other comprehensive (loss) income before reclassifications	144
Net current-period other comprehensive (loss) income	144
Ending balance	$ 92

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