Disclosure Of Fair Value Of Assets And Liabilities (Narrative) (Details)
|
3 Months Ended |
6 Months Ended |
12 Months Ended |
|
Jun. 30, 2019
USD ($)
ft²
property
|
Jun. 30, 2019
USD ($)
ft²
property
|
Dec. 31, 2018
USD ($)
property
|
| Fair Value Measurement Inputs and Valuation Techniques [Line Items] |
|
|
|
| Fair value of Company's long-term debt |
$ 2,638,850,000
|
$ 2,638,850,000
|
$ 2,711,712,000
|
| Principal balance outstanding |
2,687,642,000
|
2,687,642,000
|
$ 2,792,651,000
|
| Land impairments |
$ 2,499,000
|
$ 2,499,000
|
|
| Conshohocken And Bala Cynwyd, Pennsylvania [Member] |
|
|
|
| Fair Value Measurement Inputs and Valuation Techniques [Line Items] |
|
|
|
| Number of real estate properties | property |
2
|
2
|
2
|
| Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Conshohocken And Bala Cynwyd, Pennsylvania [Member] |
|
|
|
| Fair Value Measurement Inputs and Valuation Techniques [Line Items] |
|
|
|
| Land impairments |
|
|
$ 24,600,000
|
| Parsippany [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] |
|
|
|
| Fair Value Measurement Inputs and Valuation Techniques [Line Items] |
|
|
|
| Area of property (in square feet) | ft² |
317,040
|
317,040
|
|
| Valuation impairment charge |
$ 5,800,000
|
|
|