Summary of Significant Accounting Policies - AOCI, Simon Property Group, Inc. (Details) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($)
Changes in accumulated other comprehensive income (loss)
Beginning balance	$ 3,296,681
Ending balance	3,212,959
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss)
Beginning balance	(126,017)
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
Ending balance	(120,962)
Currency translation adjustments
Changes in accumulated other comprehensive income (loss)
Beginning balance	(158,904)
Other comprehensive (loss) income before reclassifications	(4,130)
Net current-period other comprehensive (loss) income	(4,130)
Ending balance	(163,034)
Accumulated derivative gains (losses), net
Changes in accumulated other comprehensive income (loss)
Beginning balance	32,933
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
Ending balance	41,993
Net unrealized (losses) gains on marketable securities
Changes in accumulated other comprehensive income (loss)
Beginning balance	(46)
Other comprehensive (loss) income before reclassifications	125
Net current-period other comprehensive (loss) income	125
Ending balance	$ 79

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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