Summary of Significant Accounting Policies - AOCI, Simon Property Group L.P. (Details) $ in Thousands	6 Months Ended
Jun. 30, 2019 USD ($)
Simon Property Group, L.P.
Changes in accumulated other comprehensive income (loss)
Beginning Balance	$ 3,789,558
Ending balance	3,356,638
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss)
Other comprehensive (loss) income before reclassifications	(4,613)
Amounts reclassified from accumulated other comprehensive income (loss)	1,887
Net current-period other comprehensive (loss) income	(2,726)
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	(5,364)
Amounts reclassified from accumulated other comprehensive income (loss)	2,174
Net current-period other comprehensive (loss) income	(3,190)
Ending balance	(148,304)
Currency translation adjustments
Changes in accumulated other comprehensive income (loss)
Other comprehensive (loss) income before reclassifications	(7,208)
Net current-period other comprehensive (loss) income	(7,208)
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	(8,367)
Net current-period other comprehensive (loss) income	(8,367)
Ending balance	(191,345)
Accumulated derivative gains (losses), net
Changes in accumulated other comprehensive income (loss)
Other comprehensive (loss) income before reclassifications	2,002
Amounts reclassified from accumulated other comprehensive income (loss)	1,887
Net current-period other comprehensive (loss) income	3,889
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	2,320
Amounts reclassified from accumulated other comprehensive income (loss)	2,174
Net current-period other comprehensive (loss) income	4,494
Ending balance	42,410
Net unrealized (losses) gains on marketable securities
Changes in accumulated other comprehensive income (loss)
Other comprehensive (loss) income before reclassifications	593
Net current-period other comprehensive (loss) income	593
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	683
Net current-period other comprehensive (loss) income	683
Ending balance	$ 631

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