Document and Entity Information	3 Months Ended
	Mar. 31, 2015 $ / shares shares
Entity Registrant Name	SIMON PROPERTY GROUP INC /DE/
Entity Central Index Key	0001063761
Document Type	10-Q/A
Document Period End Date	Mar. 31, 2015
Amendment Flag	true
Amendment Description	We are filing this Amendment No. 1 on Form 10-Q/A (this "Form 10-Q/A") to amend and restate in their entirety the following items of our Quarterly Report on Form 10-Q for the quarter ended March 31, 2015 as originally filed with the Securities and Exchange Commission on May 7, 2015 (the "Original Form 10-Q"): (i) Item 1 of Part I "Financial Information," (ii) Item 2 of Part I, "Management's Discussion and Analysis of Financial Condition and Results of Operations," (iii) Item 4 of Part I, "Controls and Procedures," and (iv) Item 6 of Part II, "Exhibits", and we have also updated the signature page, the certifications of our Chief Executive Officer and Chief Financial Officer in Exhibits 31.1, 31.2, 32.1 and 32.2, and our financial statements formatted in Extensible Business Reporting Language (XBRL) in Exhibits 101. We are amending and restating these items to reflect the recognition of the non-cash gain described in the following paragraph. No other sections were affected, but for the convenience of the reader, this Form 10-Q/A restates in its entirety, as amended, our Original Form 10-Q. This Form 10-Q/A is presented as of the filing date of the Original Form 10-Q and does not reflect events occurring after that date, or modify or update disclosures in any way other than as required to reflect the amendment and restatement described below. During the preparation of our financial statements for the year ended December 31, 2015, our year end reporting procedures and controls identified that a non-cash gain of $206.9 million, solely related to our equity method investment in Klépierre SA, or Klépierre, and Klépierre's acquisition of Corio N.V., or Corio, in January, 2015 should have been recorded in the first quarter of 2015. Klépierre issued 114 million additional shares of its common stock in connection with its acquisition of Corio which effectively reduced our percentage ownership interest in Klépierre common shares from 28.9% to 18.3% during the quarterly period ending March 2015. As a result of Klépierre's issuance of additional shares and the reduction in our ownership interest, we are required to recognize a gain (or loss) based on the difference in Klépierre's issue price per share as compared to our carrying value per Klépierre share. This non-cash gain is recognized in our net income in the period the change of our ownership interest occurred. We sold no shares of Klépierre in 2015 in connection with Klépierre's Corio acquisition or otherwise. The unaudited consolidated balance sheet and unaudited consolidated statement of operations and comprehensive income for the quarter ended March 31, 2015 included in this Form 10-Q/A have been amended and restated to include the effects of the $206.9 million non-cash gain.
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Common stock
Entity Common Stock, Shares Outstanding | shares	311,260,775
Entity Listing, Par Value Per Share | $ / shares	$ 0.0001
Class B common stock
Entity Common Stock, Shares Outstanding | shares	8,000
Entity Listing, Par Value Per Share | $ / shares	$ 0.0001