Significant Accounting Policies (Schedule Of Rental Property Improvements) (Details) - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended |
|---|---|---|
Mar. 31, 2021 |
Dec. 31, 2020 |
|
| Property, Plant and Equipment [Line Items] | ||
| Land held for development (including pre-development costs, if any) | $ 360,930 | $ 364,946 |
| Development and construction in progress, including land | 766,978 | 733,560 |
| Total | 1,127,908 | 1,098,506 |
| Buildings and improvement | 160,300 | 160,300 |
| Development [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Land | 74,400 | $ 74,900 |
| Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Buildings and improvement | 6,500 | |
| Land | $ 27,900 |