Per Share and Per Unit Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended									12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Per Share And Per Unit Data
Net Income attributable to Common Stockholders - Basic		$ 510,194	$ 544,254	$ 495,324	$ 548,475	$ 712,796	$ 556,267	$ 547,004	$ 620,654	$ 2,098,247	$ 2,436,721	$ 1,944,625
Net Income attributable to Common Stockholders - Diluted										$ 2,098,247	$ 2,436,721	$ 1,944,625
Weighted Average Shares Outstanding - Basic and Diluted		306,868,960	307,275,230	308,708,798	308,978,053	309,293,708	309,294,045	309,355,154	310,583,643	307,950,112	309,627,178	311,517,345
Dividends
Dividends declared per common share (in dollars per share)	$ 2.10
Common stock dividends paid (in dollars per share)										$ 8.30	$ 7.90	$ 7.15
Percent taxable as ordinary income										100.00%	96.20%	100.00%
Percent taxable as long-term capital gains										0.00%	3.80%	0.00%
Total percentage of dividends paid										100.00%	100.00%	100.00%
Simon Property Group, L.P.
Per Share And Per Unit Data
Net Income attributable to Common Stockholders - Basic		$ 587,931	$ 627,074	$ 570,389	$ 631,551	$ 821,237	$ 640,402	$ 629,822	$ 714,303	$ 2,416,945	$ 2,805,764	$ 2,239,638
Net Income attributable to Common Stockholders - Diluted										$ 2,416,945	$ 2,805,764	$ 2,239,638
Weighted Average Shares Outstanding - Basic and Diluted		353,619,579	354,038,110	355,491,396	355,778,250	356,396,387	356,073,080	356,181,817	357,446,988	354,724,019	356,520,452	358,776,632