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Summary Of Significant Accounting Policies (Summary Of Currency Exchange Rates) (Details) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Australian Dollar [Member] | Spot Rate [Member] |  |  |
Currency Exchange Rates [Line Items] |  |  |
Foreign currency exchange rate | 0.7709 | 0.7030 | 0.7046
Australian Dollar [Member] | Average Rate [Member] |  |  |
Currency Exchange Rates [Line Items] |  |  |
Foreign currency exchange rate | 0.6904 | 0.6954 | 0.7479
New Zealand Dollar [Member] | Spot Rate [Member] |  |  |
Currency Exchange Rates [Line Items] |  |  |
Foreign currency exchange rate | 0.7194 | 0.6745 | 0.6711
New Zealand Dollar [Member] | Average Rate [Member] |  |  |
Currency Exchange Rates [Line Items] |  |  |
Foreign currency exchange rate | 0.6504 | 0.6593 | 0.6930

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