Area of a real estate property.

No definition available.

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2420-110228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

Dispositions (Narratives) (Details)											3 Months Ended		12 Months Ended
Dispositions (Narratives) (Details)	Mar. 31, 2018 USD ($)	Dec. 22, 2015 USD ($) ft²	Sep. 09, 2015 USD ($) ft²	Aug. 06, 2015 USD ($)	Mar. 31, 2015 USD ($) ft² $ / shares shares	Mar. 13, 2015 USD ($)	Jan. 15, 2015 USD ($) Properties	Dec. 18, 2014 USD ($) ft²	Jul. 08, 2014 USD ($) ft²	Feb. 24, 2014 USD ($)	Mar. 31, 2015 USD ($) ft² $ / shares	Mar. 31, 2014 USD ($)	Dec. 31, 2016 USD ($) ft² Properties	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) Properties
Dispositions
Income from discontinued operations													$ 7,172,000	$ 52,262,000	$ 585,676,000
Gain (Loss) from disposal of real estate													5,074,000	65,396,000	507,192,000
Cash Considerations Transferred During Spin Off (in US Dollars)													0	225,000,000	0
Operating Partnership Units Value													0	80,000,000	0
Real estate impairment losses													$ 161,165,000	$ 256,000	26,518,000
PREIT
Dispositions
Equity method ownership percentage													8.00%
Washington DC \| Office
Dispositions
Square Footage Of Real Estate Property \| ft²													11,100,000
Number Of Real Estate Properties \| Properties													44
Discontinued Operations \| Strip Shopping Centers
Dispositions
Gain (Loss) from disposal of real estate															$ 22,500,000
Number Of Real Estate Properties Sold \| Properties															6
Cash Proceeds from sale of real estate															$ 66,410,000
Discontinued Operations \| Springfield Mall \| PREIT
Dispositions
Square Footage Of Real Estate Property \| ft²					1,350,000						1,350,000
Gross proceeds from the sale of real estate					$ 485,313,000
Gain (Loss) from disposal of real estate					7,823,000						$ 7,192,000
Cash Proceeds from sale of real estate					$ 340,000,000
Operating Partnership Units Received From Buyer \| shares					6,250,000
Operating Partnership Units Value					$ 145,313,000
Operating Partnership Unis Value Per Unit \| $ / shares					$ 23.25						$ 23.25
Deferred Gain on Sale of Property					$ 631,000						$ 631,000
Real estate impairment losses												$ 20,000,000
Discontinued Operations \| Monmouth Mall \| Regional Malls
Dispositions
Gross proceeds from the sale of real estate				$ 38,000,000
Gain (Loss) from disposal of real estate				33,153,000
Market value of the property sold				$ 229,000,000
Sale Of Ownership Interest Percent				50.00%
Discontinued Operations \| Geary Street, CA
Dispositions
Proceeds from Sale of interest in leases						$ 34,189,000
Gain on sale of interest in leases						$ 21,376,000
Discontinued Operations \| Urban Edge Properties
Dispositions
Cash Considerations Transferred During Spin Off (in US Dollars)							$ 225,000,000
Discontinued Operations \| Urban Edge Properties \| Warehouse
Dispositions
Number Of Real Estate Properties \| Properties							1
Discontinued Operations \| Urban Edge Properties \| Strip Shopping Centers
Dispositions
Number Of Real Estate Properties \| Properties							79
Discontinued Operations \| Urban Edge Properties \| Regional Malls
Dispositions
Number Of Real Estate Properties \| Properties							3
Discontinued Operations \| Retail Properties \| Retail CA Los Angeles Beverly Connection
Dispositions
Square Footage Of Real Estate Property \| ft²									335,000
Gross proceeds from the sale of real estate									$ 260,000,000
Gain (Loss) from disposal of real estate									44,155,000
Cash Proceeds from sale of real estate									239,000,000
Mortgage loan receivable									$ 21,000,000
Mortgage loan receivable maturity tenure									10 years
Discontinued Operations \| New York \| 20 Broad Street \| Office
Dispositions
Square Footage Of Real Estate Property \| ft²		473,000
Gross proceeds from the sale of real estate		$ 200,000,000
Income from discontinued operations		157,000,000
Gain (Loss) from disposal of real estate		142,000,000
Lease termination income		$ 15,000,000
Discontinued Operations \| New York \| Retail NY Hicksville (Broadway Mall)
Dispositions
Gross proceeds from the sale of real estate										$ 94,000,000
Net proceeds from the sale of real estate										$ 92,174,000
Discontinued Operations \| New York \| 1740 Broadway \| Office
Dispositions
Square Footage Of Real Estate Property \| ft²								601,000
Gross proceeds from the sale of real estate								$ 605,000,000
Gain (Loss) from disposal of real estate								441,000,000
Net proceeds from the sale of real estate								580,000,000
Income tax on gain on sale								$ 484,000,000
Discontinued Operations \| Washington DC \| 1750 Pennsylvania Avenue \| Office
Dispositions
Square Footage Of Real Estate Property \| ft²			278,000
Gross proceeds from the sale of real estate			$ 182,000,000
Gain (Loss) from disposal of real estate			102,000,000
Deferred Tax Gain On Sale Of Real Estate			$ 137,000,000
Discontinued Operations \| Estimate \| Springfield Mall \| PREIT
Dispositions
Additional Consideration Receivable Percent	50.00%
Additional Consideration Theshold, Value	$ 465,000,000
Capitalization rate	5.50%