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Real Estate Investments Real Estate Investments (Tables) | 3 Months Ended
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Mar. 31, 2013
Real Estate [Abstract] |
Gross Carrying Value Of Company's Properties [Table Text Block] | As of March 31, 2013 and December 31, 2012, the gross carrying value of the Company’s Properties was as follows (in thousands):
| March 31, 2013 |  | December 31, 2012
Land | $ | 641,507 |  |  | $ | 662,107 |
Building and improvements | 3,483,888 |  |  | 3,576,065 |
Tenant improvements | 482,495 |  |  | 487,997 |
| $ | 4,607,890 |  |  | $ | 4,726,169 |

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