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Properties, net (Details 3) (USD $)
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3 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | ||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Dec. 31, 2012
|
Sep. 30, 2012
|
Jun. 30, 2012
|
Mar. 31, 2012
|
Dec. 31, 2011
|
Sep. 30, 2011
|
Jun. 30, 2011
|
Mar. 31, 2011
|
Dec. 31, 2012
|
Dec. 31, 2011
|
Dec. 31, 2010
|
Dec. 31, 2012
Non-operating Properties
|
Sep. 30, 2012
400 Professional Drive
|
Sep. 30, 2012
Greater Philadelphia
|
Dec. 31, 2012
Greater Philadelphia
|
Dec. 31, 2012
Colorado Springs
|
Dec. 31, 2012
Properties, net
Significant Unobservable Inputs (Level 3)
Fair value measurement on a nonrecurring basis
|
Jul. 02, 2012
Secured Debt [Member]
400 Professional Drive
|
Dec. 31, 2012
Operating properties
sqft
|
Sep. 30, 2012
Operating properties
|
Jun. 30, 2012
Operating properties
|
Mar. 31, 2012
Operating properties
|
Dec. 31, 2011
Operating properties
sqft
|
Sep. 30, 2011
Operating properties
|
Jun. 30, 2011
Operating properties
|
Mar. 31, 2011
Operating properties
|
Dec. 31, 2012
Operating properties
buillding
sqft
|
Dec. 31, 2011
Operating properties
buillding
sqft
|
Dec. 31, 2012
Operating properties
White Marsh Portfolio
buillding
sqft
|
Dec. 31, 2012
Operating properties
1101 Sentry Gateway
buillding
sqft
|
Dec. 31, 2012
Operating properties
222 and 224 Schilling Circle
buillding
sqft
|
Dec. 31, 2012
Operating properties
15 and 45 West Gude Drive
buillding
sqft
|
Dec. 31, 2012
Operating properties
11800 Tech Road
buillding
sqft
|
Dec. 31, 2012
Operating properties
400 Professional Drive
buillding
sqft
|
Dec. 31, 2012
Operating properties
July 2012 Portfolio Disposition
buillding
sqft
|
Dec. 31, 2011
Operating properties
1344 & 1348 Ashton Road and 1350 Dorsey Road
buillding
sqft
|
Dec. 31, 2011
Operating properties
216 Schilling Circle
buillding
sqft
|
Dec. 31, 2011
Operating properties
Towson Portfolio
buillding
sqft
|
Dec. 31, 2011
Operating properties
11011 McCormick Road
buillding
sqft
|
Dec. 31, 2011
Operating properties
10001 Franklin Square Drive
buillding
sqft
|
Dec. 31, 2011
Operating properties
Rutherford Business Center Portfolio
buillding
sqft
|
Dec. 31, 2012
Non-operating Properties
|
Sep. 30, 2012
Non-operating Properties
|
Jun. 30, 2012
Non-operating Properties
|
Mar. 31, 2012
Non-operating Properties
|
Dec. 31, 2011
Non-operating Properties
|
Sep. 30, 2011
Non-operating Properties
|
Jun. 30, 2011
Non-operating Properties
|
Mar. 31, 2011
Non-operating Properties
|
Dec. 31, 2012
Non-operating Properties
|
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| Dispositions | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Number of Buildings | 35 | 23 | 5 | 1 | 2 | 2 | 1 | 1 | 23 | 3 | 1 | 4 | 1 | 1 | 13 | |||||||||||||||||||||||||||||||||||
| Total Rentable Square Feet | 2,302,000 | 894,000 | 2,302,000 | 894,000 | 163,000 | 95,000 | 56,000 | 231,000 | 240,000 | 130,000 | 1,387,000 | 39,000 | 36,000 | 179,000 | 57,000 | 218,000 | 365,000 | |||||||||||||||||||||||||||||||||
| Sale Price of Operating Properties | $ 285,506,000 | $ 76,660,000 | $ 19,100,000 | $ 13,500,000 | $ 4,400,000 | $ 49,107,000 | $ 21,300,000 | $ 16,198,000 | $ 161,901,000 | $ 3,800,000 | $ 4,700,000 | $ 16,000,000 | $ 3,450,000 | $ 16,250,000 | $ 32,460,000 | |||||||||||||||||||||||||||||||||||
| Gain on Sale | 21,186,000 | 4,807,000 | 2,445,000 | 1,739,000 | 102,000 | 0 | 0 | 0 | 16,900,000 | 150,000 | 175,000 | 1,134,000 | 822,000 | 305,000 | 2,221,000 | |||||||||||||||||||||||||||||||||||
| Sale Price of Non-operating Properties | 28,100,000 | |||||||||||||||||||||||||||||||||||||||||||||||||
| Debt settled through the surrender of real estate assets | 15,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||||
| Fair value of real estate disposed in settlement of debt | 11,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||||
| Gain (loss) on early extinguishment of debt | (943,000) | (1,639,000) | 0 | 3,700,000 | ||||||||||||||||||||||||||||||||||||||||||||||
| Expected future redevelopment expenditure | 25,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||||
| Impairment on Disposition of Additional Property | 5,100,000 | |||||||||||||||||||||||||||||||||||||||||||||||||
| Asset Impairment Charges, Continuing and Noncontinuing Operations Including Exit Costs | 2,140,000 | 55,829,000 | 2,354,000 | 6,587,000 | 151,021,000 | 78,674,000 | 44,605,000 | 27,742,000 | 66,910,000 | 151,021,000 | 0 | 247,000 | 55,829,000 | 2,354,000 | 11,833,000 | 70,512,000 | 39,481,000 | 31,031,000 | 0 | 70,263,000 | 1,893,000 | 0 | 0 | (5,246,000) | 80,509,000 | 39,193,000 | 13,574,000 | 27,742,000 | (3,353,000) | |||||||||||||||||||||
| Disposals and Impairment Losses | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Aggregate net impairment losses recognized in connection with disposition plan | 6,900,000 | |||||||||||||||||||||||||||||||||||||||||||||||||
| Aggregate net impairment losses recognized in discontinued operation in connection with disposition plan | 23,700,000 | |||||||||||||||||||||||||||||||||||||||||||||||||
| Exit Costs Included in Impairment Losses in Connection with Dispositions | (4,146,000) | 0 | 0 | 4,200,000 | ||||||||||||||||||||||||||||||||||||||||||||||
| Aggregate non-cash impairment losses on properties included in disposition plan | 122,500,000 | 46,100,000 | ||||||||||||||||||||||||||||||||||||||||||||||||
| Real estate impairment classified as discontinued operations | 67,500,000 | |||||||||||||||||||||||||||||||||||||||||||||||||
| Real estate impairment excluded related to income tax benefits | $ 4,800,000 | |||||||||||||||||||||||||||||||||||||||||||||||||