v2.4.0.8

Real Estate Activity During the Nine Months Ended September 30, 2014 (Narrative) (Details) (USD $) | 3 Months Ended | 9 Months Ended | 0 Months Ended |  |  |  |  |  |  |  |  |  |  | 0 Months Ended |  | 0 Months Ended |  |  | 0 Months Ended
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Sep. 30, 2014 | Sep. 30, 2013 | Sep. 30, 2014 | Sep. 30, 2013 | Jul. 29, 2014 Mountain View Technology Park and Mountain View Research Building Sixteen [Member] | Aug. 20, 2014 Land at One Reston Overlook [Member] | Aug. 22, 2014 Land Parcel Within Broad Run Business Park [Member] | Aug. 22, 2014 Land Parcel Within Broad Run Business Park [Member] acre | Jun. 11, 2014 Patriots park [Member] Buildings sqft | May 20, 2014 10 CityPoint [Member] sqft | May 20, 2014 888 Boylston Street [Member] sqft | Apr. 03, 2014 690 Folsom Street [Member] sqft | Apr. 01, 2014 99 Third Avenue [Member] sqft | Feb. 10, 2014 The Avant at Reston Town Center Residential [Member] apartments sqft | Jul. 29, 2014 Mountain View Technology [Member] Mountain View Technology Park and Mountain View Research Building Sixteen [Member] Buildings sqft | Jul. 29, 2014 Mountain View Research Building Sixteen [Member] Mountain View Technology Park and Mountain View Research Building Sixteen [Member] sqft | Aug. 31, 2014 250 West 55th Street [Member] sqft | Sep. 17, 2014 680 Folsom Street [Member] sqft | Sep. 16, 2014 Consolidated Properties [Member] 601 Lexington Avenue, Atlantic Wharf Office Building and One Hundred Federal Street [Member] | Apr. 10, 2014 Consolidated Properties [Member] Salesforece Tower (formerly Transbay Tower) [Member] sqft floor | Sep. 16, 2014 Consolidated Properties [Member] 601 Lexington Avenue [Member] 601 Lexington Avenue, Atlantic Wharf Office Building and One Hundred Federal Street [Member] sqft | Sep. 16, 2014 Consolidated Properties [Member] Atlantic Wharf Office [Member] 601 Lexington Avenue, Atlantic Wharf Office Building and One Hundred Federal Street [Member] sqft | Sep. 16, 2014 Consolidated Properties [Member] 100 Federal Street [Member] 601 Lexington Avenue, Atlantic Wharf Office Building and One Hundred Federal Street [Member] sqft | Sep. 16, 2014 Consolidated Properties [Member] Low Rise [Member] 601 Lexington Avenue [Member] 601 Lexington Avenue, Atlantic Wharf Office Building and One Hundred Federal Street [Member] floor | Sep. 16, 2014 Consolidated Properties [Member] Office Tower [Member] 601 Lexington Avenue [Member] 601 Lexington Avenue, Atlantic Wharf Office Building and One Hundred Federal Street [Member] floor | Oct. 02, 2014 Subsequent Event [Member] Patriots park [Member] sqft Buildings | Oct. 30, 2014 Subsequent Event [Member] Consolidated Properties [Member] 601 Lexington Avenue, Atlantic Wharf Office Building and One Hundred Federal Street [Member] | Oct. 30, 2014 Subsequent Event [Member] Consolidated Properties [Member] 601 Lexington Avenue [Member] 601 Lexington Avenue, Atlantic Wharf Office Building and One Hundred Federal Street [Member] sqft | Oct. 30, 2014 Subsequent Event [Member] Consolidated Properties [Member] Atlantic Wharf Office [Member] 601 Lexington Avenue, Atlantic Wharf Office Building and One Hundred Federal Street [Member] sqft | Oct. 30, 2014 Subsequent Event [Member] Consolidated Properties [Member] 100 Federal Street [Member] 601 Lexington Avenue, Atlantic Wharf Office Building and One Hundred Federal Street [Member] sqft | Oct. 30, 2014 Subsequent Event [Member] Consolidated Properties [Member] Low Rise [Member] 601 Lexington Avenue [Member] 601 Lexington Avenue, Atlantic Wharf Office Building and One Hundred Federal Street [Member] floor | Oct. 30, 2014 Subsequent Event [Member] Consolidated Properties [Member] Office Tower [Member] 601 Lexington Avenue [Member] 601 Lexington Avenue, Atlantic Wharf Office Building and One Hundred Federal Street [Member] floor
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of real estate properties |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  | 7 |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  |
Number of apartment units |  |  |  |  |  |  |  |  |  |  |  |  |  | 359 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Area of Real Estate Property |  |  |  |  |  |  |  |  | 706,000 | 245,000 | 425,000 | 26,000 | 17,000 | 355,000 | 135,000 | 63,000 | 988,000 | 525,000 |  | 1,400,000 | 1,669,000 | 791,000 | 1,323,000 |  |  | 706,000 |  | 1,669,000 | 791,000 | 1,323,000 |  |
Sales price |  |  |  |  | $ 92,100,000 |  |  | $ 9,800,000 | $ 321,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 321,000,000 |  |  |  |  |  |
Ownership Percentage by Parent |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 95.00% |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 45.00% |  |  |  |  |  |  |  | 45.00% |  |  |  |  |
Square Footage Of Signed Lease |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 714,000 |  |  |  |  |  |  |  |  |  |  |  |
Number of floors real estate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 61 |  |  |  | 6 | 59 |  |  |  |  |  | 6 | 59
Secured Debt Carrying Value |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 712,900,000 |  |  |  |  |  |  |  | 712,900,000 |  |  |  |  |
Proceeds from the sales of real estate |  |  | 103,542,000 | 160,815,000 | 91,200,000 | 2,600,000 | 9,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gains on sales of real estate | 41,937,000 | 0 | 41,937,000 | 0 | 36,400,000 | 1,200,000 | 4,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Area of Land |  |  |  |  |  |  |  | 15.5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross Sales Price Before Deducting Indebtedness |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,827,000,000 |  |  |  |  |  |  |  | $ 1,827,000,000 |  |  |  |  |

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