Equity - Temporary Equity (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($) item shares	Dec. 31, 2017 USD ($) item shares
Redeemable preferred stock
Limited partners' preferred interest in the Operating Partnership and noncontrolling redeemable interests in properties | $	$ 197,937	$ 190,480
Simon Property Group, L.P.
Redeemable preferred stock
Limited partners' preferred interest in the Operating Partnership and noncontrolling redeemable interests in properties | $	$ 197,937	$ 190,480
7.5% Cumulative Redeemable Preferred Units
Redeemable preferred stock
Noncontrolling interests redeemable at amounts in excess of fair value | item	0	0
Preferred stock stated dividend rate percentage	7.50%	7.50%
Temporary equity, shares authorized | shares	260,000	260,000
Temporary equity, shares issued | shares	255,373	255,373
Temporary equity, shares outstanding | shares	255,373	255,373
Limited partners' preferred interest in the Operating Partnership and noncontrolling redeemable interests in properties | $	$ 25,537	$ 25,537
7.5% Cumulative Redeemable Preferred Units | Simon Property Group, L.P.
Redeemable preferred stock
Preferred stock stated dividend rate percentage	7.50%	7.50%
Temporary equity, shares authorized | shares	260,000	260,000
Temporary equity, shares issued | shares	255,373	255,373
Temporary equity, shares outstanding | shares	255,373	255,373
Limited partners' preferred interest in the Operating Partnership and noncontrolling redeemable interests in properties | $	$ 25,537	$ 25,537
Other noncontrolling redeemable interest
Redeemable preferred stock
Limited partners' preferred interest in the Operating Partnership and noncontrolling redeemable interests in properties | $	172,400	164,943
Other noncontrolling redeemable interest | Simon Property Group, L.P.
Redeemable preferred stock
Limited partners' preferred interest in the Operating Partnership and noncontrolling redeemable interests in properties | $	$ 172,400	$ 164,943