Disclosure Of Fair Value Of Assets And Liabilities (Narrative) (Details)
|
3 Months Ended |
12 Months Ended |
|
Mar. 31, 2018
USD ($)
property
|
Dec. 31, 2017
USD ($)
property
|
| Fair Value Inputs, Assets, Quantitative Information [Line Items] |
|
|
| Fair value of Company's long-term debt |
$ 2,534,001,000
|
$ 2,764,033,000
|
| Principal balance outstanding |
2,615,211,000
|
2,809,568,000
|
| Aggregate carrying value |
38,566,000
|
$ 171,578,000
|
| Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Paramus And Rochelle Park [Member] |
|
|
| Fair Value Inputs, Assets, Quantitative Information [Line Items] |
|
|
| Aggregate carrying value |
$ 38,566,000
|
|
| Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Office [Member] | Parsippany, Paramus, Rochelle Park, Hamilton And Wall, New Jersey And White Plains, New York [Member] |
|
|
| Fair Value Inputs, Assets, Quantitative Information [Line Items] |
|
|
| Number of properties held for sale | property |
|
21
|
| Aggregate carrying value |
|
$ 171,600,000
|
| Unrealized losses on rental properties held for sale |
|
$ 12,300,000
|
| Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Office [Member] | Paramus, Rochelle Park, Hamilton And Wall, New Jersey And White Plains, New York [Member] |
|
|
| Fair Value Inputs, Assets, Quantitative Information [Line Items] |
|
|
| Number of properties not expected to recover from estimated net sales proceeds | property |
|
7
|
| Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Office [Member] | Paramus And Rochelle Park [Member] |
|
|
| Fair Value Inputs, Assets, Quantitative Information [Line Items] |
|
|
| Number of properties held for sale | property |
2
|
|
| Estimated expected sales proceeds |
$ 41,400,000
|
|
| Disposal Group, Not Discontinued Operations [Member] |
|
|
| Fair Value Inputs, Assets, Quantitative Information [Line Items] |
|
|
| Sales proceeds |
$ 223,049,000
|
|