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Schedule III - Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 325,038 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 450,881 |  |  |
Buildings and Improvements | 2,669,016 |  |  |
Net Improvements (Retirements) Since Acquisition | 539,989 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 481,282 |  |  |
Buildings and Improvements | 3,178,604 |  |  |
Total | 3,659,886 | $ 4,487,588 | $ 4,631,128 | $ 4,669,289
Accumulated Depreciation at December 31, 2016 | 885,392 | $ 1,080,616 | $ 1,078,996 | $ 983,808
PENNSYLVANIA SUBURBS [Member] | 400 Berwyn Park [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,657 |  |  |
Buildings and Improvements | 4,462 |  |  |
Net Improvements (Retirements) Since Acquisition | 13,383 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,657 |  |  |
Buildings and Improvements | 17,845 |  |  |
Total | 20,502 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 7,132 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1999 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1999 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 300 Berwyn Park [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,206 |  |  |
Buildings and Improvements | 13,422 |  |  |
Net Improvements (Retirements) Since Acquisition | 4,014 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,206 |  |  |
Buildings and Improvements | 17,436 |  |  |
Total | 19,642 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 9,213 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1989 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 1050 Westlakes Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,611 |  |  |
Buildings and Improvements | 10,445 |  |  |
Net Improvements (Retirements) Since Acquisition | 6,130 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,611 |  |  |
Buildings and Improvements | 16,575 |  |  |
Total | 19,186 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 9,450 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1984 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1999 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 1200 Swedesford Road [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,595 |  |  |
Buildings and Improvements | 11,809 |  |  |
Net Improvements (Retirements) Since Acquisition | 2,996 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,595 |  |  |
Buildings and Improvements | 14,805 |  |  |
Total | 17,400 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 8,043 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1994 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2001 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 200 Berwyn Park [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 1,533 |  |  |
Buildings and Improvements | 9,460 |  |  |
Net Improvements (Retirements) Since Acquisition | 1,864 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,533 |  |  |
Buildings and Improvements | 11,324 |  |  |
Total | 12,857 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 5,947 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 1180 Swedesford Road [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,086 |  |  |
Buildings and Improvements | 8,342 |  |  |
Net Improvements (Retirements) Since Acquisition | 3,110 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,086 |  |  |
Buildings and Improvements | 11,452 |  |  |
Total | 13,538 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 4,429 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2001 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 100 Berwyn Park [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 1,180 |  |  |
Buildings and Improvements | 7,290 |  |  |
Net Improvements (Retirements) Since Acquisition | 1,483 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,180 |  |  |
Buildings and Improvements | 8,773 |  |  |
Total | 9,953 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 4,508 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1986 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 1160 Swedesford Road [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 1,781 |  |  |
Buildings and Improvements | 7,124 |  |  |
Net Improvements (Retirements) Since Acquisition | 6,108 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,045 |  |  |
Buildings and Improvements | 12,968 |  |  |
Total | 15,013 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 4,437 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1986 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2001 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 1100 Cassett Road [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 1,695 |  |  |
Buildings and Improvements | 6,779 |  |  |
Net Improvements (Retirements) Since Acquisition | 1,271 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,695 |  |  |
Buildings and Improvements | 8,050 |  |  |
Total | 9,745 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 3,133 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1997 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2001 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | Six Tower Bridge (181 Washington Street) [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 6,927 |  |  |
Buildings and Improvements | 14,722 |  |  |
Net Improvements (Retirements) Since Acquisition | 1,504 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 6,237 |  |  |
Buildings and Improvements | 16,916 |  |  |
Total | 23,153 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,838 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1999 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2013 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 426 Lancaster Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 1,689 |  |  |
Buildings and Improvements | 6,756 |  |  |
Net Improvements (Retirements) Since Acquisition | 376 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,689 |  |  |
Buildings and Improvements | 7,132 |  |  |
Total | 8,821 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 3,812 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1990 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 52 Swedesford Square [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 4,241 |  |  |
Buildings and Improvements | 16,579 |  |  |
Net Improvements (Retirements) Since Acquisition | 3,852 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 4,241 |  |  |
Buildings and Improvements | 20,431 |  |  |
Total | 24,672 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 8,834 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1988 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 640 Freedom Business Center [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 4,222 |  |  |
Buildings and Improvements | 16,891 |  |  |
Net Improvements (Retirements) Since Acquisition | 5,060 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 4,222 |  |  |
Buildings and Improvements | 21,951 |  |  |
Total | 26,173 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 10,997 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1991 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 630 Allendale Road [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,836 |  |  |
Buildings and Improvements | 4,028 |  |  |
Net Improvements (Retirements) Since Acquisition | 12,614 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,894 |  |  |
Buildings and Improvements | 16,584 |  |  |
Total | 19,478 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 6,597 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2000 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2000 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 620 Freedom Business Center [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,770 |  |  |
Buildings and Improvements | 11,014 |  |  |
Net Improvements (Retirements) Since Acquisition | 2,115 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,770 |  |  |
Buildings and Improvements | 13,129 |  |  |
Total | 15,899 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 7,064 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1986 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 1000 First Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,772 |  |  |
Buildings and Improvements | 10,936 |  |  |
Net Improvements (Retirements) Since Acquisition | 2,495 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,772 |  |  |
Buildings and Improvements | 13,431 |  |  |
Total | 16,203 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 6,427 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1980 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 1060 First Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,712 |  |  |
Buildings and Improvements | 10,953 |  |  |
Net Improvements (Retirements) Since Acquisition | 4,261 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,712 |  |  |
Buildings and Improvements | 15,214 |  |  |
Total | 17,926 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 6,705 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 630 Freedom Business Center [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,773 |  |  |
Buildings and Improvements | 11,144 |  |  |
Net Improvements (Retirements) Since Acquisition | 3,786 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,773 |  |  |
Buildings and Improvements | 14,930 |  |  |
Total | 17,703 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 7,019 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1989 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 1020 First Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,168 |  |  |
Buildings and Improvements | 8,576 |  |  |
Net Improvements (Retirements) Since Acquisition | 7,627 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,168 |  |  |
Buildings and Improvements | 16,203 |  |  |
Total | 18,371 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 8,469 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1984 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 1040 First Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,860 |  |  |
Buildings and Improvements | 11,282 |  |  |
Net Improvements (Retirements) Since Acquisition | 5,037 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,860 |  |  |
Buildings and Improvements | 16,319 |  |  |
Total | 19,179 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 6,699 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1985 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 610 Freedom Business Center [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,017 |  |  |
Buildings and Improvements | 8,070 |  |  |
Net Improvements (Retirements) Since Acquisition | 2,878 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,017 |  |  |
Buildings and Improvements | 10,948 |  |  |
Total | 12,965 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 5,174 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1985 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 650 Park Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 1,916 |  |  |
Buildings and Improvements | 4,378 |  |  |
Net Improvements (Retirements) Since Acquisition | 1,561 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,916 |  |  |
Buildings and Improvements | 5,939 |  |  |
Total | 7,855 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 3,295 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1968 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 600 Park Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 1,012 |  |  |
Buildings and Improvements | 4,048 |  |  |
Net Improvements (Retirements) Since Acquisition | 385 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,012 |  |  |
Buildings and Improvements | 4,433 |  |  |
Total | 5,445 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 2,286 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1964 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 14 Campus Boulevard [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,244 |  |  |
Buildings and Improvements | 4,217 |  |  |
Net Improvements (Retirements) Since Acquisition | 1,533 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,244 |  |  |
Buildings and Improvements | 5,750 |  |  |
Total | 7,994 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 4,008 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1998 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 17 Campus Boulevard [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 1,108 |  |  |
Buildings and Improvements | 5,155 |  |  |
Net Improvements (Retirements) Since Acquisition | (924) |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,108 |  |  |
Buildings and Improvements | 4,231 |  |  |
Total | 5,339 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,595 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2001 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 11 Campus Boulevard [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 1,112 |  |  |
Buildings and Improvements | 4,067 |  |  |
Net Improvements (Retirements) Since Acquisition | 998 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,112 |  |  |
Buildings and Improvements | 5,065 |  |  |
Total | 6,177 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 2,286 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1998 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1999 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 15 Campus Boulevard [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 1,164 |  |  |
Buildings and Improvements | 3,896 |  |  |
Net Improvements (Retirements) Since Acquisition | 285 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,164 |  |  |
Buildings and Improvements | 4,181 |  |  |
Total | 5,345 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,485 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2002 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2000 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 18 Campus Boulevard [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 787 |  |  |
Buildings and Improvements | 3,312 |  |  |
Net Improvements (Retirements) Since Acquisition | 856 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 787 |  |  |
Buildings and Improvements | 4,168 |  |  |
Total | 4,955 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,844 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1990 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1996 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 401 Plymouth Road [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 6,199 |  |  |
Buildings and Improvements | 16,131 |  |  |
Net Improvements (Retirements) Since Acquisition | 16,815 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 6,199 |  |  |
Buildings and Improvements | 32,946 |  |  |
Total | 39,145 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 12,591 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2001 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2000 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | Metroplex (4000 Chemical Road) [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 4,373 |  |  |
Buildings and Improvements | 24,546 |  |  |
Net Improvements (Retirements) Since Acquisition | 1,300 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 4,373 |  |  |
Buildings and Improvements | 25,846 |  |  |
Total | 30,219 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 6,243 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2007 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2001 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 610 West Germantown Pike [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 3,651 |  |  |
Buildings and Improvements | 14,514 |  |  |
Net Improvements (Retirements) Since Acquisition | 3,337 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 3,651 |  |  |
Buildings and Improvements | 17,851 |  |  |
Total | 21,502 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 6,986 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2002 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 600 West Germantown Pike [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 3,652 |  |  |
Buildings and Improvements | 15,288 |  |  |
Net Improvements (Retirements) Since Acquisition | 2,295 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 3,652 |  |  |
Buildings and Improvements | 17,583 |  |  |
Total | 21,235 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 6,436 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1986 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2002 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 630 West Germantown Pike [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 3,558 |  |  |
Buildings and Improvements | 14,743 |  |  |
Net Improvements (Retirements) Since Acquisition | 1,630 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 3,558 |  |  |
Buildings and Improvements | 16,373 |  |  |
Total | 19,931 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 6,002 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1988 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2002 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 620 West Germantown Pike [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 3,572 |  |  |
Buildings and Improvements | 14,435 |  |  |
Net Improvements (Retirements) Since Acquisition | 1,119 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 3,572 |  |  |
Buildings and Improvements | 15,554 |  |  |
Total | 19,126 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 5,778 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1990 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2002 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 660 West Germantown Pike [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 3,694 |  |  |
Buildings and Improvements | 5,487 |  |  |
Net Improvements (Retirements) Since Acquisition | 19,487 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 5,405 |  |  |
Buildings and Improvements | 23,263 |  |  |
Total | 28,668 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 3,359 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2012 |  |  |
Depreciable Life (Years) | 30 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 351 Plymouth Road [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 1,043 |  |  |
Buildings and Improvements | 555 |  |  |
Net Improvements (Retirements) Since Acquisition | 0 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,043 |  |  |
Buildings and Improvements | 555 |  |  |
Total | 1,598 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 163 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2000 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 150 Radnor Chester Road [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 11,925 |  |  |
Buildings and Improvements | 36,986 |  |  |
Net Improvements (Retirements) Since Acquisition | 11,990 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 11,897 |  |  |
Buildings and Improvements | 49,004 |  |  |
Total | 60,901 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 20,032 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1983 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 29 years |  |  |
PENNSYLVANIA SUBURBS [Member] | One Radnor Corporate Center [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 7,323 |  |  |
Buildings and Improvements | 28,613 |  |  |
Net Improvements (Retirements) Since Acquisition | 23,052 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 7,323 |  |  |
Buildings and Improvements | 51,665 |  |  |
Total | 58,988 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 23,923 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1998 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 29 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 201 King of Prussia Road [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 8,956 |  |  |
Buildings and Improvements | 29,811 |  |  |
Net Improvements (Retirements) Since Acquisition | 4,587 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 8,949 |  |  |
Buildings and Improvements | 34,405 |  |  |
Total | 43,354 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 17,840 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2001 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 25 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 555 Lancaster Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 8,014 |  |  |
Buildings and Improvements | 16,508 |  |  |
Net Improvements (Retirements) Since Acquisition | 17,847 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 8,609 |  |  |
Buildings and Improvements | 33,760 |  |  |
Total | 42,369 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 15,559 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1973 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 24 years |  |  |
PENNSYLVANIA SUBURBS [Member] | Four Radnor Corporate Center [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 5,406 |  |  |
Buildings and Improvements | 21,390 |  |  |
Net Improvements (Retirements) Since Acquisition | 13,271 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 5,705 |  |  |
Buildings and Improvements | 34,362 |  |  |
Total | 40,067 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 12,531 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1995 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 30 years |  |  |
PENNSYLVANIA SUBURBS [Member] | Five Radnor Corporate Center [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 6,506 |  |  |
Buildings and Improvements | 25,525 |  |  |
Net Improvements (Retirements) Since Acquisition | 5,540 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 6,578 |  |  |
Buildings and Improvements | 30,993 |  |  |
Total | 37,571 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 10,392 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1998 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 38 years |  |  |
PENNSYLVANIA SUBURBS [Member] | Three Radnor Corporate Center [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 4,773 |  |  |
Buildings and Improvements | 17,961 |  |  |
Net Improvements (Retirements) Since Acquisition | 2,615 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 4,791 |  |  |
Buildings and Improvements | 20,558 |  |  |
Total | 25,349 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 9,654 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1998 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 29 years |  |  |
PENNSYLVANIA SUBURBS [Member] | Two Radnor Corporate Center [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 3,937 |  |  |
Buildings and Improvements | 15,484 |  |  |
Net Improvements (Retirements) Since Acquisition | 4,075 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 3,942 |  |  |
Buildings and Improvements | 19,554 |  |  |
Total | 23,496 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 8,510 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1998 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 29 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 130 Radnor Chester Road [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,573 |  |  |
Buildings and Improvements | 8,338 |  |  |
Net Improvements (Retirements) Since Acquisition | 3,483 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,567 |  |  |
Buildings and Improvements | 11,827 |  |  |
Total | 14,394 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 5,433 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1983 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 25 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 170 Radnor Chester Road [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,514 |  |  |
Buildings and Improvements | 8,147 |  |  |
Net Improvements (Retirements) Since Acquisition | 2,864 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,509 |  |  |
Buildings and Improvements | 11,016 |  |  |
Total | 13,525 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 3,992 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1983 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 25 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 200 N. Radnor Chester Rd. [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 3,366 |  |  |
Buildings and Improvements | 0 |  |  |
Net Improvements (Retirements) Since Acquisition | 3,583 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 3,366 |  |  |
Buildings and Improvements | 3,583 |  |  |
Total | 6,949 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 373 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2014 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2005 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 101 West Elm Street [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 6,251 |  |  |
Buildings and Improvements | 25,209 |  |  |
Net Improvements (Retirements) Since Acquisition | 3,170 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 6,251 |  |  |
Buildings and Improvements | 28,379 |  |  |
Total | 34,630 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 8,912 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1999 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2005 |  |  |
Depreciable Life (Years) | 40 years |  |  |
PENNSYLVANIA SUBURBS [Member] | 1 West Elm Street [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 3,557 |  |  |
Buildings and Improvements | 14,249 |  |  |
Net Improvements (Retirements) Since Acquisition | 3,125 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 3,557 |  |  |
Buildings and Improvements | 17,374 |  |  |
Total | 20,931 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 4,687 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1999 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2005 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Philadelphia CBD [Member] | Cira Centre (2929 Arch Street) [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 0 |  |  |
Buildings and Improvements | 208,570 |  |  |
Net Improvements (Retirements) Since Acquisition | (9,473) |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 12,586 |  |  |
Buildings and Improvements | 186,511 |  |  |
Total | 199,097 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 63,153 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2005 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Philadelphia CBD [Member] | Three Logan Square (1717 Arch Street) [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 0 |  |  |
Buildings and Improvements | 98,188 |  |  |
Net Improvements (Retirements) Since Acquisition | 68,691 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 25,195 |  |  |
Buildings and Improvements | 141,684 |  |  |
Total | 166,879 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 33,059 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1990 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2010 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Philadelphia CBD [Member] | Two Commerce Square (2001 Market Street) [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 112,000 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 15,323 |  |  |
Buildings and Improvements | 120,200 |  |  |
Net Improvements (Retirements) Since Acquisition | 21,518 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 15,323 |  |  |
Buildings and Improvements | 141,718 |  |  |
Total | 157,041 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 12,190 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1992 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2013 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Philadelphia CBD [Member] | One Logan Square (130 North 18th Street) [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 14,496 |  |  |
Buildings and Improvements | 107,736 |  |  |
Net Improvements (Retirements) Since Acquisition | 27,447 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 14,473 |  |  |
Buildings and Improvements | 135,206 |  |  |
Total | 149,679 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 46,840 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1998 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 34 years |  |  |
Philadelphia CBD [Member] | Two Logan Square (100 North 18th Street) [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 86,012 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 16,066 |  |  |
Buildings and Improvements | 100,255 |  |  |
Net Improvements (Retirements) Since Acquisition | 17,631 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 16,066 |  |  |
Buildings and Improvements | 117,886 |  |  |
Total | 133,952 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 37,378 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1988 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 36 years |  |  |
Philadelphia CBD [Member] | One Commerce Square (2005 Market Street) [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 127,026 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 15,161 |  |  |
Buildings and Improvements | 105,021 |  |  |
Net Improvements (Retirements) Since Acquisition | 21,419 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 15,160 |  |  |
Buildings and Improvements | 126,441 |  |  |
Total | 141,601 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 11,190 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2013 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Philadelphia CBD [Member] | Cira Centre South Garage [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 0 |  |  |
Buildings and Improvements | 76,008 |  |  |
Net Improvements (Retirements) Since Acquisition | 7,588 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 0 |  |  |
Buildings and Improvements | 83,596 |  |  |
Total | 83,596 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 12,504 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2010 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Philadelphia CBD [Member] | 1900 Market [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 7,768 |  |  |
Buildings and Improvements | 17,263 |  |  |
Net Improvements (Retirements) Since Acquisition | 27,176 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 7,768 |  |  |
Buildings and Improvements | 44,439 |  |  |
Total | 52,207 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 4,389 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1981 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2012 |  |  |
Depreciable Life (Years) | 30 years |  |  |
Philadelphia CBD [Member] | 3020 Market Street [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 0 |  |  |
Buildings and Improvements | 21,417 |  |  |
Net Improvements (Retirements) Since Acquisition | 7,651 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 0 |  |  |
Buildings and Improvements | 29,068 |  |  |
Total | 29,068 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 6,105 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1959 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2011 |  |  |
Depreciable Life (Years) | 26 years |  |  |
Philadelphia CBD [Member] | The Lift at Juniper Street (101 - 103 Juniper Street) [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 0 |  |  |
Buildings and Improvements | 14,401 |  |  |
Net Improvements (Retirements) Since Acquisition | 324 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 478 |  |  |
Buildings and Improvements | 14,247 |  |  |
Total | 14,725 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 2,915 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2010 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Philadelphia CBD [Member] | Philadelphia Marine Center [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 532 |  |  |
Buildings and Improvements | 2,196 |  |  |
Net Improvements (Retirements) Since Acquisition | 4,317 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 628 |  |  |
Buildings and Improvements | 6,417 |  |  |
Total | 7,045 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 2,965 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1998 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Philadelphia CBD [Member] | 618-634 Market Street [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 13,365 |  |  |
Buildings and Improvements | 5,791 |  |  |
Net Improvements (Retirements) Since Acquisition | 460 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 13,365 |  |  |
Buildings and Improvements | 6,251 |  |  |
Total | 19,616 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 2,056 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1966 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2015 |  |  |
Depreciable Life (Years) | 5 years |  |  |
Philadelphia CBD [Member] | FMC Tower at Cira Centre South [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 0 |  |  |
Buildings and Improvements | 166,474 |  |  |
Net Improvements (Retirements) Since Acquisition | 0 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 0 |  |  |
Buildings and Improvements | 166,474 |  |  |
Total | 166,474 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 3,325 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2016 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Metropolitan DC [Member] | 11720 Beltsville Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 3,831 |  |  |
Buildings and Improvements | 16,661 |  |  |
Net Improvements (Retirements) Since Acquisition | (8,065) |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,472 |  |  |
Buildings and Improvements | 10,955 |  |  |
Total | 12,427 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 6,066 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 46 years |  |  |
Metropolitan DC [Member] | 11700 Beltsville Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,808 |  |  |
Buildings and Improvements | 12,081 |  |  |
Net Improvements (Retirements) Since Acquisition | (10,823) |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 257 |  |  |
Buildings and Improvements | 3,809 |  |  |
Total | 4,066 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 2,999 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1981 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 46 years |  |  |
Metropolitan DC [Member] | 11710 Beltsville Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,278 |  |  |
Buildings and Improvements | 11,100 |  |  |
Net Improvements (Retirements) Since Acquisition | (9,060) |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 408 |  |  |
Buildings and Improvements | 3,910 |  |  |
Total | 4,318 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 2,615 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 46 years |  |  |
Metropolitan DC [Member] | 11740 Beltsville Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 198 |  |  |
Buildings and Improvements | 870 |  |  |
Net Improvements (Retirements) Since Acquisition | (159) |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 155 |  |  |
Buildings and Improvements | 754 |  |  |
Total | 909 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 255 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 46 years |  |  |
Metropolitan DC [Member] | 6600 Rockledge Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 0 |  |  |
Buildings and Improvements | 37,421 |  |  |
Net Improvements (Retirements) Since Acquisition | 10,700 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 0 |  |  |
Buildings and Improvements | 48,121 |  |  |
Total | 48,121 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 11,894 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1981 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 50 years |  |  |
Metropolitan DC [Member] | 2340 Dulles Corner Boulevard [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 16,345 |  |  |
Buildings and Improvements | 65,379 |  |  |
Net Improvements (Retirements) Since Acquisition | 5,188 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 16,129 |  |  |
Buildings and Improvements | 70,783 |  |  |
Total | 86,912 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 21,568 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Metropolitan DC [Member] | 2291 Wood Oak Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 8,243 |  |  |
Buildings and Improvements | 52,413 |  |  |
Net Improvements (Retirements) Since Acquisition | 12,543 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 8,782 |  |  |
Buildings and Improvements | 64,417 |  |  |
Total | 73,199 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 17,417 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1999 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 55 years |  |  |
Metropolitan DC [Member] | 2251 Corporate Park Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 11,472 |  |  |
Buildings and Improvements | 45,893 |  |  |
Net Improvements (Retirements) Since Acquisition | 3,411 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 11,472 |  |  |
Buildings and Improvements | 49,304 |  |  |
Total | 60,776 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 12,696 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2000 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Metropolitan DC [Member] | 2355 Dulles Corner Boulevard [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 10,365 |  |  |
Buildings and Improvements | 43,876 |  |  |
Net Improvements (Retirements) Since Acquisition | 4,510 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 10,365 |  |  |
Buildings and Improvements | 48,386 |  |  |
Total | 58,751 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 15,120 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1988 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Metropolitan DC [Member] | 2411 Dulles Corner Park [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 7,279 |  |  |
Buildings and Improvements | 46,340 |  |  |
Net Improvements (Retirements) Since Acquisition | 18,759 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 7,417 |  |  |
Buildings and Improvements | 64,961 |  |  |
Total | 72,378 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 13,783 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1990 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 50 years |  |  |
Metropolitan DC [Member] | 13880 Dulles Corner Lane [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 7,236 |  |  |
Buildings and Improvements | 39,213 |  |  |
Net Improvements (Retirements) Since Acquisition | 4,458 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 7,373 |  |  |
Buildings and Improvements | 43,534 |  |  |
Total | 50,907 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 10,044 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1997 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 55 years |  |  |
Metropolitan DC [Member] | 2121 Cooperative Way [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 5,598 |  |  |
Buildings and Improvements | 38,639 |  |  |
Net Improvements (Retirements) Since Acquisition | 2,793 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 5,795 |  |  |
Buildings and Improvements | 41,235 |  |  |
Total | 47,030 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 9,814 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2000 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 54 years |  |  |
Metropolitan DC [Member] | 2201 Cooperative Way [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 4,809 |  |  |
Buildings and Improvements | 34,093 |  |  |
Net Improvements (Retirements) Since Acquisition | 6,051 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 4,809 |  |  |
Buildings and Improvements | 40,144 |  |  |
Total | 44,953 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 9,918 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1990 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 54 years |  |  |
Metropolitan DC [Member] | 13825 Sunrise Valley Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 3,794 |  |  |
Buildings and Improvements | 19,365 |  |  |
Net Improvements (Retirements) Since Acquisition | 2,485 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 3,866 |  |  |
Buildings and Improvements | 21,778 |  |  |
Total | 25,644 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 6,283 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1989 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 46 years |  |  |
Metropolitan DC [Member] | 1676 International Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 18,437 |  |  |
Buildings and Improvements | 97,538 |  |  |
Net Improvements (Retirements) Since Acquisition | 3,307 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 18,785 |  |  |
Buildings and Improvements | 100,497 |  |  |
Total | 119,282 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 21,039 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1999 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 55 years |  |  |
Metropolitan DC [Member] | 8260 Greensboro Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 7,952 |  |  |
Buildings and Improvements | 33,964 |  |  |
Net Improvements (Retirements) Since Acquisition | 2,873 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 8,102 |  |  |
Buildings and Improvements | 36,687 |  |  |
Total | 44,789 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 9,000 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1980 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 52 years |  |  |
Metropolitan DC [Member] | 2273 Research Boulevard [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 5,167 |  |  |
Buildings and Improvements | 31,110 |  |  |
Net Improvements (Retirements) Since Acquisition | 4,153 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 5,237 |  |  |
Buildings and Improvements | 35,193 |  |  |
Total | 40,430 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 8,885 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1999 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 45 years |  |  |
Metropolitan DC [Member] | 2275 Research Boulevard [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 5,059 |  |  |
Buildings and Improvements | 29,668 |  |  |
Net Improvements (Retirements) Since Acquisition | 8,227 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 5,154 |  |  |
Buildings and Improvements | 37,800 |  |  |
Total | 42,954 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 10,439 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1990 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 45 years |  |  |
Metropolitan DC [Member] | 2277 Research Boulevard [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 4,649 |  |  |
Buildings and Improvements | 26,952 |  |  |
Net Improvements (Retirements) Since Acquisition | 18,863 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 4,733 |  |  |
Buildings and Improvements | 45,731 |  |  |
Total | 50,464 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 10,051 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1986 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 45 years |  |  |
Metropolitan DC [Member] | 1900 Gallows Road [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 7,797 |  |  |
Buildings and Improvements | 47,817 |  |  |
Net Improvements (Retirements) Since Acquisition | 12,386 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 7,944 |  |  |
Buildings and Improvements | 60,056 |  |  |
Total | 68,000 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 15,234 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1989 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 52 years |  |  |
Metropolitan DC [Member] | 8521 Leesburg Pike [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 4,316 |  |  |
Buildings and Improvements | 30,885 |  |  |
Net Improvements (Retirements) Since Acquisition | 6,201 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 4,397 |  |  |
Buildings and Improvements | 37,005 |  |  |
Total | 41,402 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 8,321 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1984 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 51 years |  |  |
Austin, Texas [Member] | 11501 Burnet Road - Building 1 [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 3,755 |  |  |
Buildings and Improvements | 22,702 |  |  |
Net Improvements (Retirements) Since Acquisition | 144 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 3,755 |  |  |
Buildings and Improvements | 22,846 |  |  |
Total | 26,601 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,071 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1991 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2015 |  |  |
Depreciable Life (Years) | 35 years |  |  |
Austin, Texas [Member] | 11501 Burnet Road - Building 2 [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,732 |  |  |
Buildings and Improvements | 16,305 |  |  |
Net Improvements (Retirements) Since Acquisition | 1,518 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,732 |  |  |
Buildings and Improvements | 17,823 |  |  |
Total | 20,555 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 936 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1991 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2015 |  |  |
Depreciable Life (Years) | 35 years |  |  |
Austin, Texas [Member] | 11501 Burnet Road - Building 3 [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 3,688 |  |  |
Buildings and Improvements | 22,348 |  |  |
Net Improvements (Retirements) Since Acquisition | 142 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 3,688 |  |  |
Buildings and Improvements | 22,490 |  |  |
Total | 26,178 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,055 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1991 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2015 |  |  |
Depreciable Life (Years) | 35 years |  |  |
Austin, Texas [Member] | 11501 Burnet Road - Building 4 [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,614 |  |  |
Buildings and Improvements | 15,740 |  |  |
Net Improvements (Retirements) Since Acquisition | 100 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,614 |  |  |
Buildings and Improvements | 15,840 |  |  |
Total | 18,454 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 743 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1991 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2015 |  |  |
Depreciable Life (Years) | 35 years |  |  |
Austin, Texas [Member] | 11501 Burnet Road - Building 5 [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 3,689 |  |  |
Buildings and Improvements | 22,354 |  |  |
Net Improvements (Retirements) Since Acquisition | 142 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 3,689 |  |  |
Buildings and Improvements | 22,496 |  |  |
Total | 26,185 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,055 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1991 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2015 |  |  |
Depreciable Life (Years) | 35 years |  |  |
Austin, Texas [Member] | 11501 Burnet Road - Building 8 [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 1,400 |  |  |
Buildings and Improvements | 7,422 |  |  |
Net Improvements (Retirements) Since Acquisition | 47 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,400 |  |  |
Buildings and Improvements | 7,469 |  |  |
Total | 8,869 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 357 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1991 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2015 |  |  |
Depreciable Life (Years) | 35 years |  |  |
Austin, Texas [Member] | 11501 Burnet Road - Parking Garage [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 0 |  |  |
Buildings and Improvements | 19,826 |  |  |
Net Improvements (Retirements) Since Acquisition | 126 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 0 |  |  |
Buildings and Improvements | 19,952 |  |  |
Total | 19,952 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,248 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1991 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2015 |  |  |
Depreciable Life (Years) | 35 years |  |  |
Other [Member] | 200 Lake Drive East [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,069 |  |  |
Buildings and Improvements | 8,275 |  |  |
Net Improvements (Retirements) Since Acquisition | (844) |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,440 |  |  |
Buildings and Improvements | 8,060 |  |  |
Total | 9,500 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 3,995 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1989 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2001 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | 220 Lake Drive East [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,144 |  |  |
Buildings and Improvements | 8,798 |  |  |
Net Improvements (Retirements) Since Acquisition | (713) |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,492 |  |  |
Buildings and Improvements | 8,737 |  |  |
Total | 10,229 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 4,093 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1988 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2001 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | 210 Lake Drive East [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 1,645 |  |  |
Buildings and Improvements | 6,579 |  |  |
Net Improvements (Retirements) Since Acquisition | 564 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 1,145 |  |  |
Buildings and Improvements | 7,643 |  |  |
Total | 8,788 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 3,618 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1986 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2001 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | 1200 Concord Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 6,395 |  |  |
Buildings and Improvements | 24,664 |  |  |
Net Improvements (Retirements) Since Acquisition | (5,168) |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 4,748 |  |  |
Buildings and Improvements | 21,143 |  |  |
Total | 25,891 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 10,481 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1984 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 34 years |  |  |
Other [Member] | 1220 Concord Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 6,476 |  |  |
Buildings and Improvements | 24,966 |  |  |
Net Improvements (Retirements) Since Acquisition | (5,463) |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 4,719 |  |  |
Buildings and Improvements | 21,260 |  |  |
Total | 25,979 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 10,500 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1984 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2006 |  |  |
Depreciable Life (Years) | 34 years |  |  |
Other [Member] | 20 East Clementon Road [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 769 |  |  |
Buildings and Improvements | 3,055 |  |  |
Net Improvements (Retirements) Since Acquisition | 500 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 719 |  |  |
Buildings and Improvements | 3,605 |  |  |
Total | 4,324 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,815 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1986 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | 10 Foster Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 244 |  |  |
Buildings and Improvements | 971 |  |  |
Net Improvements (Retirements) Since Acquisition | 69 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 244 |  |  |
Buildings and Improvements | 1,040 |  |  |
Total | 1,284 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 544 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1983 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | 7 Foster Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 231 |  |  |
Buildings and Improvements | 921 |  |  |
Net Improvements (Retirements) Since Acquisition | 75 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 231 |  |  |
Buildings and Improvements | 996 |  |  |
Total | 1,227 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 520 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1983 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | 2 Foster Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 185 |  |  |
Buildings and Improvements | 730 |  |  |
Net Improvements (Retirements) Since Acquisition | 58 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 185 |  |  |
Buildings and Improvements | 788 |  |  |
Total | 973 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 382 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1974 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | 4 Foster Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 183 |  |  |
Buildings and Improvements | 726 |  |  |
Net Improvements (Retirements) Since Acquisition | 30 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 183 |  |  |
Buildings and Improvements | 756 |  |  |
Total | 939 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 376 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1974 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | 1 Foster Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 93 |  |  |
Buildings and Improvements | 364 |  |  |
Net Improvements (Retirements) Since Acquisition | 30 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 93 |  |  |
Buildings and Improvements | 394 |  |  |
Total | 487 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 212 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1972 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | 5 U.S. Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 21 |  |  |
Buildings and Improvements | 81 |  |  |
Net Improvements (Retirements) Since Acquisition | 2 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 21 |  |  |
Buildings and Improvements | 83 |  |  |
Total | 104 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 43 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | 5 Foster Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 9 |  |  |
Buildings and Improvements | 32 |  |  |
Net Improvements (Retirements) Since Acquisition | 26 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 9 |  |  |
Buildings and Improvements | 58 |  |  |
Total | 67 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 32 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1968 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | Two Eves Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 818 |  |  |
Buildings and Improvements | 3,461 |  |  |
Net Improvements (Retirements) Since Acquisition | 269 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 818 |  |  |
Buildings and Improvements | 3,730 |  |  |
Total | 4,548 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,897 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | Five Eves Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 703 |  |  |
Buildings and Improvements | 2,819 |  |  |
Net Improvements (Retirements) Since Acquisition | 1,456 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 703 |  |  |
Buildings and Improvements | 4,275 |  |  |
Total | 4,978 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,996 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1986 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | Four B Eves Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 588 |  |  |
Buildings and Improvements | 2,369 |  |  |
Net Improvements (Retirements) Since Acquisition | 185 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 588 |  |  |
Buildings and Improvements | 2,554 |  |  |
Total | 3,142 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,377 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | Four A Eves Drive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 539 |  |  |
Buildings and Improvements | 2,168 |  |  |
Net Improvements (Retirements) Since Acquisition | 608 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 539 |  |  |
Buildings and Improvements | 2,776 |  |  |
Total | 3,315 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,305 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1987 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | 7000 Midlantic Derive [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,560 |  |  |
Buildings and Improvements | 2,790 |  |  |
Net Improvements (Retirements) Since Acquisition | 0 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,560 |  |  |
Buildings and Improvements | 2,790 |  |  |
Total | 5,350 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 51 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 2016 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2003 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | Main Street-Plaza 1000 [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 2,732 |  |  |
Buildings and Improvements | 10,942 |  |  |
Net Improvements (Retirements) Since Acquisition | 95 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 2,732 |  |  |
Buildings and Improvements | 11,037 |  |  |
Total | 13,769 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 11,012 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1988 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | Main Street-Piazza [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 696 |  |  |
Buildings and Improvements | 2,802 |  |  |
Net Improvements (Retirements) Since Acquisition | 3,442 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 696 |  |  |
Buildings and Improvements | 6,244 |  |  |
Total | 6,940 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 2,375 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1990 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | Main Street-Promenade [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 532 |  |  |
Buildings and Improvements | 2,052 |  |  |
Net Improvements (Retirements) Since Acquisition | 525 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 532 |  |  |
Buildings and Improvements | 2,577 |  |  |
Total | 3,109 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 1,379 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1988 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 1997 |  |  |
Depreciable Life (Years) | 40 years |  |  |
Other [Member] | 920 North King Street [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 6,141 |  |  |
Buildings and Improvements | 21,140 |  |  |
Net Improvements (Retirements) Since Acquisition | 3,599 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 6,141 |  |  |
Buildings and Improvements | 24,739 |  |  |
Total | 30,880 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 9,090 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1989 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 30 years |  |  |
Other [Member] | 300 Delaware Avenue [Member] |  |  |  |
Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 0 |  |  |
Initial Cost [Abstract] |  |  |  |
Land | 6,369 |  |  |
Buildings and Improvements | 13,739 |  |  |
Net Improvements (Retirements) Since Acquisition | 3,032 |  |  |
Carrying Amount at Which Carried [Abstract] |  |  |  |
Land | 6,369 |  |  |
Buildings and Improvements | 16,771 |  |  |
Total | 23,140 |  |  |
Accumulated Depreciation at December 31, 2016 | $ 8,202 |  |  |
Real Estate And Accumulated Depreciation Construction Year | 1989 |  |  |
Real Estate And Accumulated Depreciation Year Of Acquisition | 2004 |  |  |
Depreciable Life (Years) | 23 years |  |  |

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