Fair Value Disclosures (Debt Obligations) (Details) - USD ($) $ in Thousands |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Estimated fair value of the Company's debt obligations compared to their carrying amounts | ||
| Mortgages and secured loans payable | $ 5,622,111 | $ 5,676,238 |
| Total debt obligations, net | 5,622,111 | 5,676,238 |
| Carrying Amount | ||
| Estimated fair value of the Company's debt obligations compared to their carrying amounts | ||
| Mortgages and secured loans payable | 911,665 | 917,945 |
| Notes payable | 3,183,771 | 3,182,492 |
| Unsecured credit facility and term loan | 1,526,675 | 1,575,801 |
| Total debt obligations, net | 5,622,111 | 5,676,238 |
| Fair Value | ||
| Estimated fair value of the Company's debt obligations compared to their carrying amounts | ||
| Mortgages and secured loans payable | 946,503 | 963,702 |
| Notes payable | 3,154,654 | 3,224,877 |
| Unsecured credit facility and term loan | 1,536,230 | 1,586,206 |
| Total debt obligations | $ 5,637,387 | $ 5,774,785 |