Dispositions	12 Months Ended
Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Dispositions	Dispositions: On June 30, 2015, the Company conveyed Great Northern Mall, an 895,000 square foot regional shopping center in Clay, New York, to the mortgage lender by a deed-in-lieu of foreclosure and was discharged from the mortgage note payable. The loan was nonrecourse to the Company. As a result, the Company recognized a loss on the extinguishment of debt of $1,627. On November 19, 2015, the Company sold Panorama Mall, a 312,000 square foot community center in Panorama City, California, for $98,000, resulting in a gain on the sale of assets of $73,726. The Company used the proceeds from the sale to pay down its line of credit and for general corporate purposes. On April 13, 2016, the Company sold Capitola Mall, a 586,000 square foot regional shopping center in Capitola, California, for $93,000, resulting in a gain on the sale of assets of $24,894. The Company used the proceeds from the sale to pay down its line of credit and for general corporate purposes. On May 31, 2016, the Company sold a former Mervyn's store in Yuma, Arizona, for $3,200, resulting in a loss on the sale of assets of $3,066. The Company used the proceeds from the sale to pay down its line of credit and for general corporate purposes. On July 15, 2016, the Company conveyed Flagstaff Mall, a 347,000 square foot regional shopping center in Flagstaff, Arizona, to the mortgage lender by a deed-in-lieu of foreclosure and was discharged from the mortgage note payable. The loan was non-recourse to the Company. As a result, the Company recognized a gain on the extinguishment of debt of $5,284. On January 18, 2017, the Company sold Cascade Mall, a 589,000 square foot regional shopping center in Burlington, Washington; and Northgate Mall, a 750,000 square foot regional shopping center in San Rafael, California, in a combined transaction for $170,000, resulting in a gain on the sale of assets of $59,577. The proceeds were used to pay off the mortgage note payable on Northgate Mall and to repurchase shares of the Company's common stock under the 2017 Stock Buyback Program (See Note 13—Stockholders' Equity). On November 16, 2017, the Company sold 500 North Michigan Avenue, a 326,000 square foot office building in Chicago, Illinois for $86,350, resulting in a gain on sale of assets of $14,597. The Company used the proceeds from the sale to pay down its line of credit and for other general corporate purposes.

Dispositions:

On June 30, 2015, the Company conveyed Great Northern Mall, an 895,000 square foot regional shopping center in Clay, New York, to the mortgage lender by a deed-in-lieu of foreclosure and was discharged from the mortgage note payable. The loan was nonrecourse to the Company. As a result, the Company recognized a loss on the extinguishment of debt of $1,627.

On November 19, 2015, the Company sold Panorama Mall, a 312,000 square foot community center in Panorama City, California, for $98,000, resulting in a gain on the sale of assets of $73,726. The Company used the proceeds from the sale to pay down its line of credit and for general corporate purposes.

On April 13, 2016, the Company sold Capitola Mall, a 586,000 square foot regional shopping center in Capitola, California, for $93,000, resulting in a gain on the sale of assets of $24,894. The Company used the proceeds from the sale to pay down its line of credit and for general corporate purposes.

On May 31, 2016, the Company sold a former Mervyn's store in Yuma, Arizona, for $3,200, resulting in a loss on the sale of assets of $3,066. The Company used the proceeds from the sale to pay down its line of credit and for general corporate purposes.

On July 15, 2016, the Company conveyed Flagstaff Mall, a 347,000 square foot regional shopping center in Flagstaff, Arizona, to the mortgage lender by a deed-in-lieu of foreclosure and was discharged from the mortgage note payable. The loan was non-recourse to the Company. As a result, the Company recognized a gain on the extinguishment of debt of $5,284.

On January 18, 2017, the Company sold Cascade Mall, a 589,000 square foot regional shopping center in Burlington, Washington; and Northgate Mall, a 750,000 square foot regional shopping center in San Rafael, California, in a combined transaction for $170,000, resulting in a gain on the sale of assets of $59,577. The proceeds were used to pay off the mortgage note payable on Northgate Mall and to repurchase shares of the Company's common stock under the 2017 Stock Buyback Program (See Note 13—Stockholders' Equity).

On November 16, 2017, the Company sold 500 North Michigan Avenue, a 326,000 square foot office building in Chicago, Illinois for $86,350, resulting in a gain on sale of assets of $14,597. The Company used the proceeds from the sale to pay down its line of credit and for other general corporate purposes.