Stockholders' Equity	12 Months Ended
Dec. 31, 2018
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders' Equity: 2015 Stock Buyback Program: On September 30, 2015, the Company's Board of Directors authorized the repurchase of up to $1,200,000 of the Company's outstanding common shares over the period ending September 30, 2017, as market conditions warranted. On February 17, 2016, the Company entered into an accelerated share repurchase program ("ASR") to repurchase an $400,000 of the Company's common stock. In accordance with the ASR, the Company made a prepayment of $400,000 and received an initial share delivery of 4,222,193 shares. On April 19, 2016, the ASR was completed and the Company received delivery of an additional 861,235 shares. The average price of the 5,083,428 shares repurchased under the ASR was $78.69 per share. The ASR was funded from borrowings under the Company's line of credit, which had been recently paid down from the proceeds from the financings and sale of ownership interests in Arrowhead Towne Center and the MAC Heitman Portfolio (See Note 4—Investments in Unconsolidated Joint Ventures). On May 9, 2016, the Company entered into an ASR to repurchase the remaining $400,000 of the Company's common stock authorized for repurchase. In accordance with the ASR, the Company made a prepayment of $400,000 and received an initial share delivery of 3,964,812 shares. On July 11, 2016, the ASR was completed and the Company received delivery of an additional 1,104,162 shares. The average price of the 5,068,974 shares repurchased under the ASR was $78.91 per share. The ASR was funded from borrowings under the Company's line of credit, which had been recently paid down from the proceeds from the financings and sale of ownership interests in Arrowhead Towne Center and the MAC Heitman Portfolio (See Note 4—Investments in Unconsolidated Joint Ventures). 2017 Stock Buyback Program: On February 12, 2017, the Company's Board of Directors authorized the repurchase of up to $500,000 of its outstanding common shares as market conditions and the Company’s liquidity warrant. Repurchases may be made through open market purchases, privately negotiated transactions, structured or derivative transactions, including ASR transactions, or other methods of acquiring shares, from time to time as permitted by securities laws and other legal requirements. During the period from February 12, 2017 to December 31, 2017, the Company repurchased a total of 3,627,390 of its common shares for $221,428, representing an average price of $61.01 per share. The Company funded the repurchases from the net proceeds of the sale of Cascade Mall and Northgate Mall (See Note 15—Dispositions), its share of the proceeds from the sale of ownership interests in office buildings at Country Club Plaza and Fashion District Philadelphia (See Note 4—Investments in Unconsolidated Joint Ventures) and from borrowings under its line of credit. There were no repurchases during the year ended December 31, 2018. Special Dividend: On October 30, 2015, the Company declared a special dividend/distribution ("Special Dividend") of $2.00 per share of common stock and per OP Unit that was paid on January 6, 2016 to common stockholders and OP Unit holders of record on November 12, 2015. The Special Dividend was funded from proceeds in connection with the financing and sale of ownership interests in the PPR Portfolio and Arrowhead Towne Center (See Note 4—Investments in Unconsolidated Joint Ventures). At-The-Market Stock Offering Program ("ATM Program"): On August 20, 2014, the Company entered into an equity distribution agreement with a number of sales agents (the "ATM Program") to issue and sell, from time to time, shares of common stock, par value $0.01 per share, having an aggregate offering price of up to $500,000. The ATM Program expired by its terms in August 2017. No shares were sold under the ATM Program.

Stockholders' Equity:

2015 Stock Buyback Program:

On September 30, 2015, the Company's Board of Directors authorized the repurchase of up to $1,200,000 of the Company's outstanding common shares over the period ending September 30, 2017, as market conditions warranted.

On February 17, 2016, the Company entered into an accelerated share repurchase program ("ASR") to repurchase an $400,000 of the Company's common stock. In accordance with the ASR, the Company made a prepayment of $400,000 and received an initial share delivery of 4,222,193 shares. On April 19, 2016, the ASR was completed and the Company received delivery of an additional 861,235 shares. The average price of the 5,083,428 shares repurchased under the ASR was $78.69 per share. The ASR was funded from borrowings under the Company's line of credit, which had been recently paid down from the proceeds from the financings and sale of ownership interests in Arrowhead Towne Center and the MAC Heitman Portfolio (See Note 4—Investments in Unconsolidated Joint Ventures).

On May 9, 2016, the Company entered into an ASR to repurchase the remaining $400,000 of the Company's common stock authorized for repurchase. In accordance with the ASR, the Company made a prepayment of $400,000 and received an initial share delivery of 3,964,812 shares. On July 11, 2016, the ASR was completed and the Company received delivery of an additional 1,104,162 shares. The average price of the 5,068,974 shares repurchased under the ASR was $78.91 per share. The ASR was funded from borrowings under the Company's line of credit, which had been recently paid down from the proceeds from the financings and sale of ownership interests in Arrowhead Towne Center and the MAC Heitman Portfolio (See Note 4—Investments in Unconsolidated Joint Ventures).

2017 Stock Buyback Program:

On February 12, 2017, the Company's Board of Directors authorized the repurchase of up to $500,000 of its outstanding common shares as market conditions and the Company’s liquidity warrant. Repurchases may be made through open market purchases, privately negotiated transactions, structured or derivative transactions, including ASR transactions, or other methods of acquiring shares, from time to time as permitted by securities laws and other legal requirements.

During the period from February 12, 2017 to December 31, 2017, the Company repurchased a total of 3,627,390 of its common shares for $221,428, representing an average price of $61.01 per share. The Company funded the repurchases from the net proceeds of the sale of Cascade Mall and Northgate Mall (See Note 15—Dispositions), its share of the proceeds from the sale of ownership interests in office buildings at Country Club Plaza and Fashion District Philadelphia (See Note 4—Investments in Unconsolidated Joint Ventures) and from borrowings under its line of credit. There were no repurchases during the year ended December 31, 2018.

Special Dividend:

On October 30, 2015, the Company declared a special dividend/distribution ("Special Dividend") of $2.00 per share of common stock and per OP Unit that was paid on January 6, 2016 to common stockholders and OP Unit holders of record on November 12, 2015. The Special Dividend was funded from proceeds in connection with the financing and sale of ownership interests in the PPR Portfolio and Arrowhead Towne Center (See Note 4—Investments in Unconsolidated Joint Ventures).

At-The-Market Stock Offering Program ("ATM Program"):

On August 20, 2014, the Company entered into an equity distribution agreement with a number of sales agents (the "ATM Program") to issue and sell, from time to time, shares of common stock, par value $0.01 per share, having an aggregate offering price of up to $500,000. The ATM Program expired by its terms in August 2017. No shares were sold under the ATM Program.