Subsequent Events:	12 Months Ended
Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Events:	Subsequent Events: On January 4, 2016, the Company announced that it had reached an agreement with Taubman Centers, Inc. to form a 50/50 joint venture, to acquire Country Club Plaza, a 1,300,000 square foot regional shopping center in Kansas City, Missouri for a total purchase price of $660,000. The Company anticipates that it will fund its pro rata share of $330,000 with borrowings under its line of credit. The Company expects the purchase of Country Club Plaza, which is subject to usual and customary closing conditions, will be completed in the first quarter of 2016. On January 6, 2016, the Company replaced the existing loan on Arrowhead Towne Center with a new $400,000 loan that bears interest at 4.05% and matures on February 1, 2028. Concurrent with the refinancing, the Company sold a 40% ownership interest in Arrowhead Towne Center for $284,000. The sales price was funded by a cash payment of $124,000 and the assumption of a pro rata share of the mortgage note payable on the property of $160,000. The Company used the cash proceeds from the sale to pay down its line of credit and for general corporate purposes, which included funding the Special Dividend (See Note 12—Stockholders' Equity). On January 14, 2016, the Company placed a $150,000 loan on Twenty Ninth Street that bears interest at an effective rate of 4.10% and matures on February 6, 2026. The Company used the cash proceeds from the sales to pay down its line of credit and for general corporate purposes. On January 14, 2016, the Company formed a joint venture, whereby the Company sold a 49% ownership interest in Deptford Mall, a 1,040,000 square foot regional shopping center in Deptford, New Jersey; FlatIron Crossing, a 1,430,000 square foot regional shopping center in Broomfield, Colorado; and Twenty Ninth Street, an 850,000 square foot regional shopping center in Boulder, Colorado (the "MAC Heitman Portfolio"), for $750,980. The sales price was funded by a cash payment of $458,110 and the assumption of a pro rata share of the mortgage note payable on the properties of $292,870. The Company used the cash proceeds from the sale to pay down its line of credit and for general corporate purposes. On January 20, 2016, the Company completed its ASR program and took delivery of an additional 970,609 shares. Upon the Completion of the ASR, the Company had repurchased a total of 5,111,397 shares with an average price of $78.26 (See Note 12—Stockholders' Equity). On January 29, 2016, the Company announced a dividend/distribution of $0.68 per share for common stockholders and OP Unit holders of record on February 19, 2016. All dividends/distributions will be paid 100% in cash on March 4, 2016. On February 17, 2016, the Company entered into an ASR to repurchase $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. The Company expects to complete the ASR on or before April 22, 2016. The ASR was funded from borrowings under the Company's line of credit, which had been recently paid down from the proceeds from the recently completed financings and sale of ownership interests (See Note 4—Investments in Unconsolidated Joint Ventures).

Subsequent Events:

On January 4, 2016, the Company announced that it had reached an agreement with Taubman Centers, Inc. to form a 50/50 joint venture, to acquire Country Club Plaza, a 1,300,000 square foot regional shopping center in Kansas City, Missouri for a total purchase price of $660,000. The Company anticipates that it will fund its pro rata share of $330,000 with borrowings under its line of credit. The Company expects the purchase of Country Club Plaza, which is subject to usual and customary closing conditions, will be completed in the first quarter of 2016.

On January 6, 2016, the Company replaced the existing loan on Arrowhead Towne Center with a new $400,000 loan that bears interest at 4.05% and matures on February 1, 2028. Concurrent with the refinancing, the Company sold a 40% ownership interest in Arrowhead Towne Center for $284,000. The sales price was funded by a cash payment of $124,000 and the assumption of a pro rata share of the mortgage note payable on the property of $160,000. The Company used the cash proceeds from the sale to pay down its line of credit and for general corporate purposes, which included funding the Special Dividend (See Note 12—Stockholders' Equity).

On January 14, 2016, the Company placed a $150,000 loan on Twenty Ninth Street that bears interest at an effective rate of 4.10% and matures on February 6, 2026. The Company used the cash proceeds from the sales to pay down its line of credit and for general corporate purposes.

On January 14, 2016, the Company formed a joint venture, whereby the Company sold a 49% ownership interest in Deptford Mall, a 1,040,000 square foot regional shopping center in Deptford, New Jersey; FlatIron Crossing, a 1,430,000 square foot regional shopping center in Broomfield, Colorado; and Twenty Ninth Street, an 850,000 square foot regional shopping center in Boulder, Colorado (the "MAC Heitman Portfolio"), for $750,980. The sales price was funded by a cash payment of $458,110 and the assumption of a pro rata share of the mortgage note payable on the properties of $292,870. The Company used the cash proceeds from the sale to pay down its line of credit and for general corporate purposes.

On January 20, 2016, the Company completed its ASR program and took delivery of an additional 970,609 shares. Upon the Completion of the ASR, the Company had repurchased a total of 5,111,397 shares with an average price of $78.26 (See Note 12—Stockholders' Equity).

On January 29, 2016, the Company announced a dividend/distribution of $0.68 per share for common stockholders and OP Unit holders of record on February 19, 2016. All dividends/distributions will be paid 100% in cash on March 4, 2016.

On February 17, 2016, the Company entered into an ASR to repurchase $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. The Company expects to complete the ASR on or before April 22, 2016. The ASR was funded from borrowings under the Company's line of credit, which had been recently paid down from the proceeds from the recently completed financings and sale of ownership interests (See Note 4—Investments in Unconsolidated Joint Ventures).